Materials Research Bulletin (v.48, #4)
Pt/TiO2 composite nanoparticles synthesized by electron beam irradiation for preferential CO oxidation
by Satoru Kageyama; Yoshitsune Sugano; Yukihiro Hamaguchi; Junichiro Kugai; Yuji Ohkubo; Satoshi Seino; Takashi Nakagawa; Satoshi Ichikawa; Takao A. Yamamoto (pp. 1347-1351).
Display Omitted► Stabilizer-free Pt/TiO2 catalysts were synthesized by electron beam irradiation. ► Synthetic condition affected the size and shape of Pt nanoparticles. ► The Pt/TiO2 exhibited a high performance of preferential CO oxidation.This paper describes a novel synthesis method of stabilizer-free Pt/TiO2 composite nanoparticles using electron beam irradiation. The chemical compositions were analyzed by inductively coupled plasma-atomic emission spectroscopy. The microstructures of the samples were observed by using transmission electron microscope. Pt nanoparticles with the sizes of 2–4nm were deposited on TiO2 without any use of stabilizers. The concentrations of Pt ions and 2-propanol notably affected the size and shape of Pt nanoparticles. Their reactions of preferential CO oxidation were measured in temperature region from 60 to 140°C. The Pt/TiO2 catalyst with spherical Pt nanoparticles exhibited a 67% of CO conversion rate and 100% of selectivity at a low temperature of 60°C.
Keywords: A. Composites; C. Electron microscopy; D. Catalytic properties
Ethylenediamine-assisted solvothermal synthesis of one-dimensional Cd xZn(1− x)S solid solutions and their photocatalytic activity for nitrobenzene reduction
by Hongwei Wei; Hechun Jiang; Zhen Zheng; Quanqin Zhao; Qingyin Wu; Jinhua Zhan (pp. 1352-1356).
Display Omitted► A series of Cd xZn(1− x)S solid solutions were prepared via a hydrothermal method with the assistance of ethylenediamine. ► Band gaps of Cd xZn(1− x)S solid solutions could be adjusted from 3.52eV to 2.38eV by changing the composition. ► Photocatalytic production for aniline via nitrobenzene reduction has been achieved. ► Cd0.73Zn0.27S exhibited the highest activity under the visible-light irradiation.A series of one-dimensional Cd xZn(1− x)S semiconductor alloys were prepared via a hydrothermal method with the assistance of ethylenediamine at 180°C for 12h. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption/desorption and Fourier transform infrared techniques. With the value of x increased, the band gap of Cd xZn(1− x)S semiconductor alloys gradually decreased indicating that catalysts were exchanged to visible-light response. Photocatalytic reduction results showed that Cd0.73Zn0.27S exhibited the highest photocatalytic activity toward photo production of aniline via nitrobenzene reduction under visible irradiation respectively. The reaction mechanism was also discussed.
Keywords: A. Semiconductors; B. Chemical synthesis; C. X-ray diffraction; D. Catalytic properties
Synthesis and characterization of MFe2O4 (M=Mg, Mn, Ni) nanoparticles
by Aurel Pui; Daniel Gherca; Nicoleta Cornei (pp. 1357-1362).
Display Omitted► MFe2O4 nano core–shell structures were obtained by thermal decomposition. ► Carboxymethyl cellulose was used as surfactant and capping agent. ► The structures were confirmed by thermal analysis, FTIR and XRD spectroscopy. ► The XRD patterns indicate that all the samples are in single phase spinel structure. ► The calculated crystallites are between 6 and 13nm in size.MFe2O4 nanoparticles were obtained in the presence of natural compounds as carboxymethylcellulose (CMC). The CMC polymer had a double function as a capping agent and as a protecting agent in the growth process of nanoparticles. The synthesized nanoparticles were characterized using thermal analysis (TG, DTA, DTG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM). The XRD patterns indicate that all the samples were formed in single phase spinel structure. The results also show that the samples calcinated at 500°C for 6h have the best crystallinity and the calculated crystallite size was in the range of 6–13nm. The thermal analysis and FTIR spectra indicate a core–shell structure of the MFe2O4 nanoparticles obtained.
Keywords: A. nanostructures; B. sol-gel chemistry; C. thermogravimetric analysis (TGA); C. X-ray diffraction; D. magnetic properties
Improved efficiency of sol–gel synthesized mesoporous anatase nanopowders in photocatalytic degradation of metoprolol
by A. Golubović; B. Abramović; M. Šćepanović; M. Grujić-Brojčin; S. Armaković; I. Veljković; B. Babić; Z. Dohčević-Mitrović; Z.V. Popović (pp. 1363-1371).
Display Omitted► Mesoporous anatase nanopowders have been synthesized by sol–gel method. ► Structural and morphological properties of powders were varied by calcination time. ► Photocatalytic activity of samples was tested in degradation of MET under UV light. ► Improvement of photocatalytic efficiency was mainly influenced by pore structure.The structural and morphological properties of mesoporous anatase nanopowders, synthesized by sol–gel method, have been modified by varying the duration of calcination, in order to obtain more efficient photocatalyst than Degussa P25 in the degradation of relatively large pollutant molecules (>1nm in size). According to X-ray diffraction analysis, the crystallite size was increased from 13 to 17.5nm with the increase of calcination time from 1 to 7h. The analysis of nitrogen sorption experimental data revealed that all samples were mesoporous, with a mean pore diameters in the range of ∼5–9nm. The corrugated pore structure model was employed to evaluate pore structure tortuosity. Nanopowder properties have been related to the photocatalytic activity, tested in the degradation of metoprolol tartrate salt, selective β1-blocker used in a variety of cardiovascular diseases, with molecular size of 0.610nm×1.347nm. The study has demonstrated that samples calcined for 4 and 5h have displayed higher photocatalytic performance than Degussa P25, whereas the sample calcined for 3h has shown comparable activity.
Keywords: A. Nanostructures; B. Sol–gel chemistry; C. Raman spectroscopy; C. X-ray diffraction; D. Catalytic properties
Comparison of Li+ conductivity in Li3− xNb1− xM xO4 (M=W, Mo) with that in Li3−2 xNi xNbO4
by Youhao Liao; Preetam Singh; Weishan Li; John B. Goodenough (pp. 1372-1375).
Display Omitted► Performance of Li2.9Nb0.9M0.lO4, M=W or Mo, as a solid electrolyte is presented. ► Li2.9Nb0.9W0.lO4 showed almost same Li+-ion conductivity compared to Li2.9Ni0.05NbO4. ► W(VI) or Mo(VI) is stable in Li2.9Nb0.9M0.lO4 and not reduced before Nb(V).The performance at 300°C of Li2.9Nb0.9M0.lO4, M=W or Mo, as a solid electrolyte is compared to that reported in 2004 by McLaren et al. for Li2.9Ni0.05NbO4. The Li+ conductivity and activation energy were found to be nearly identical for M=W. Ni in the Li array does not impede Li+ mobility more than aliovalent substitution for Nb, and W(VI) is not reduced before Nb(V). Substitution of Nb(V) by Mo(VI) was not as advantageous.
Keywords: Keyword; A. Ceramics; B. Electrochemical properties; B. Ionic conductivity; C. Impedance spectroscopy; C. X-ray diffraction
Influence of niobium and titanium introduction on optical and physical properties of silicate glasses
by Nicolas Nowak; Thierry Cardinal; Frédéric Adamietz; Marc Dussauze; Vincent Rodriguez; Laurence Durivault-Reymond; Christine Deneuvilliers; Jean-Eric Poirier (pp. 1376-1380).
Increase of Knoop microhardness as a function of the number of Nb5++Ti4+ ions in high refractive index silicate glass.Display Omitted► We investigate the introduction of large amounts of TiO2 and Nb2O5 in a silicate matrix. ► We establish correlation between the TiO2 and Nb2O5 content in a glass matrix and the high refractive index. ► We established correlation between the d0 ions concentration and the glass mechanical property.The effects on optical and mechanical properties of introducing large amounts of TiO2 and Nb2O5 in a silicate matrix have been studied. Raman spectroscopy has been carried out in order to tentatively establish correlations between structural and physical properties. The high linear refractive index and the increase of the hardness for increasing d0 ions concentration have been related to the formation of a denser glass network dominated by corner linked NbO6 and TiO6 octahedra.
Keywords: C. Raman spectroscopy; C. Infrared spectroscopy; D. Optical properties; D. Mechanical properties
Intermediate surface reactions to obtain nanocrystalline PbTe via high-energy milling
by H. Rojas-Chávez; F. Reyes-Carmona; L. Huerta; D. Jaramillo-Vigueras (pp. 1381-1387).
Display Omitted► Pb–O–Te ternary system presents three major reaction stages. ► Gas–solid reactions are the kinetic contributors that promote greater rates of transformation. ► A comprehensive model based on dynamical equilibria will be proposed. ► Non-stoichiometric phases have to be expected to see as amorphous reaction products.To elucidate how surface and gaseous phases interact each other to induce chemical reactions, X-ray photoelectron spectroscopy (XPS) analyses were carried out on powders as milling took place. An acute analysis of data acquired by the XPS-technique allowed us to find a series of well-defined chemical transitions from precursors to the stoichiometric PbTe phase. By coupling, theoretical and experimental data a self-consistent model was developed.Initially, the process manifested itself as an oxidation stage and secondly as a reducing process. In agreement with a thermodynamic evaluation of free energy of phases traced during milling, chemical transitions were traced as Te2+ to Te6+ in oxidation reactions. If high oxygen potential prevails in the milling system subsequently Pb2+ evolves to Pb4+. On the other way, high valence oxides like Pb4+ or Te4+ were reduced to Pb2+ and Te2−. However, the last transition an asymmetric transformations was identified as non-stoichiometric phases.
Keywords: Keyword; A. Nanostructures; A. Semiconductors; B. Chemical synthesis; C. Photoelectron spectroscopy
Hydrothermal-induced growth of Ca10V6O25 crystals with various morphologies in a strong basic medium at different temperatures
by Mirabbos Hojamberdiev; Mehmet S. Bozgeyik; Aboubakr M. Abdullah; Maged F. Bekheet; Gangqiang Zhu; Yinglin Yan; Yunhua Xu; Kiyoshi Okada (pp. 1388-1396).
Display Omitted► C10V6O25 crystals are hydrothermally grown in a strong basic medium. ► With the increase in the pH the average crystallite size of Ca10V6O25 increases. ► Morphological transformation occurs with increasing reaction temperature. ► Ca10V6O25 powders absorb UV light with the absorption edge at ∼380nm. ► Ca10V6O25 powders demonstrate a superparamagnetic behavior.The Ca10V6O25 crystals with various morphologies were synthesized by a facile hydrothermal method in a strong basic medium. The effects of the pH of synthesizing solution, hydrothermal reaction temperature and time on the morphology and crystallinity of Ca10V6O25 powders were investigated. The as-synthesized powders were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–vis spectrophotometer and vibrating sample magnetometer. The experimental results demonstrate that phase-pure Ca10V6O25 powders could be hydrothermally obtained at temperatures ranging from 120°C to 180°C for 12–48h with the pH≥12.5 of synthesizing solution. The morphology of Ca10V6O25 powders was strongly dependent on the synthesis parameters, such as pH, temperature and time. The Ca10V6O25 microspheres were obtained at 180°C for 48h with the pH=12.5 of synthesizing solution. The UV–vis diffuse reflectance spectra have shown that the Ca10V6O25 powders efficiently absorb UV light with an absorption edge at about 380nm. All the samples noticeably exhibit a superparamagnetic behavior with a nearly zero magnetic remanence (remanent magnetization). The hydrothermally synthesized Ca10V6O25 powders may be employed as a potential candidate in novel electronic and biomedical applications.
Keywords: A. Inorganic compounds; B. Chemical synthesis; C. Electron microscopy; C. X-ray diffraction; D. Magnetic properties
Enhanced photoluminescence and electrical properties of 0-3 type ZnO/Bi3.6Eu0.4Ti3O12 nanocomposite thin films
by Xiaoye Zhou; Ni Qin; Guangheng Wu; Dinghua Bao (pp. 1397-1402).
Display Omitted► 0-3 type ZnO/Bi3.6Eu0.4Ti3O12 nanocomposite films were prepared. ► The films showed strong red emission due to the energy transfer. ► High dielectric constant and large remanent polarization were obtained. ► The mechanisms for photoluminescence and electrical properties were discussed. ► The films are promising multifunctional materials for optoelectronic devices.0-3 type ZnO/Bi3.6Eu0.4Ti3O12 (BEuT) nanocomposite films with ZnO nanopowders in BEuT host were prepared by chemical solution deposition. The effects of ZnO content on the structure, photoluminescence, and electrical properties of the films were investigated. The ZnO/BEuT molar ratio strongly affected the grain size and growth orientation of BEuT, dielectric and ferroelectric properties, as well as emission intensity. The nanocomposite films showed strong red emission peaks due to5D0→7F1 and5D0→7F2 transitions of Eu3+ ions. Good electrical properties with high dielectric constant of 480 (at 1kHz) and large remanent polarization (2 P r) of 32μC/cm2 were obtained for the nanocomposite films having a ZnO/BEuT molar ratio of 1:2. The mechanisms for enhanced photoluminescence and electric properties were discussed. The results suggest that the nanocomposite thin films are promising candidate materials for multifunctional optoelectronic devices.
Keywords: A. Thin films; B. Chemical synthesis; D. Dielectric properties; D. Ferroelectricity; D. Luminescence
Fine-tuning the photoluminescence and photocatalytic properties of CdS nanorods of varying dimensions
by Rohit Singh; Bonamali Pal (pp. 1403-1410).
The relative photocatalytic activity (salicylic acid oxidation) and photoluminescence ( λext=380nm in acetone dispersion) of as-synthesized CdS nanostructures (NS=nanosphere and NR=nanorods (CdS-2h, 6h and 10h) of different aspect ratio and Au/Ag deposited CdS-10h) are considerably varied (photoactivity increases while photoemission decreases) with the crystallinity, length, BET surface area, surface to volume ratio, area per particle and Au/Ag deposition.Display Omitted► Hexagonal CdS nanorods of varied length, width and surface area is prepared. ► Photoactivity of CdS nanorod improves with the length and radial diameter. ► CdS luminescence increases with the decreasing crystallinity and aspect ratio. ► Size and nature (Au/Ag) of metal deposition alter the photoresponse of CdS. ► CdS absorption and emission are greatly changed due to quantum size effect.CdS nanorods having different aspect ratio viz., 17 (length ∼170nm and width ∼10nm) and 28 (length ∼140nm and width ∼5nm) has been synthesized by solvothermal technique at different time intervals (2–10h). The effect of aspect ratio, crystallinity, band gap energy, surface area and Au/Ag loading on the various photoactive properties of these CdS nanostructures are discussed here. The photocatalytic activity for salicylic acid oxidation under UV irradiation is gradually improved with the increasing crystallinity of CdS nanostructures, length (140<170nm), exposed area (2358<5722nm2) per particle and decreasing surface area (158<122<76m2g−1), surface to volume ratio (0.82<0.41nm−1) and aspect ratio (28<17). The deposition of 1–2wt% Au (∼3.5nm) and Ag (∼1.8nm) nanoparticles onto CdS drastically quenched the emission and enhanced the photocatalytic activity.
Keywords: A. Nanostructures; A. Chalcogénides; B. Crystal growth; A. Optical materials; D. Catalytic properties
Sintering and technological properties of alumina/zirconia/nano-TiO2 ceramic composites
by M.M.S. Wahsh; R.M. Khattab; M.F. Zawrah (pp. 1411-1414).
Display Omitted► The role of nano TiO2 on sintering and mechanical properties of Al2O3/ZrO2 composites has been investigated. ► The sinterability of the obtained composites was improved after addition of nano TiO2. ► Microhardness and thermal shock resistance were improved after addition of nano TiO2. ► Composite having 75% Al2O3, 5% ZrO2 and 20% nano TiO2 exhibited the best properties.The present work focuses on studying the effect of nano TiO2 (0.0–25mass%) on the sintering behavior and mechanical properties of alumina/zirconia ceramic composites. Al2O3–ZrO2–TiO2 oxides mixture was sintered at 1600°C to obtain the desired composites. The sinterability and the technological properties of these ceramic composites, i.e. the sintering parameters and microhardness as well as thermal shock resistance were investigated. Moreover, phase composition and microstructure of the sintered bodies were examined using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS). The results revealed that nano TiO2 is a beneficial component for alumina/zirconia ceramic composites. The batch containing 20mass% TiO2 exhibited the highest sintering and mechanical properties as well as resistance to thermal shock. The obtained microstructure exhibited high compacted ceramic matrix composites.
Keywords: A. Ceramics; A. Composites; A. Structural materials; D. Mechanical properties
Electrical and dielectric properties of nano crystalline Ni–Co spinel ferrites
by V.L. Mathe; R.B. Kamble (pp. 1415-1419).
Display Omitted► Successful synthesis and characterization of nanocrystalline Ni xCo1– xFe2O4 ferrites. ► Ferrimagnetic to paramagnetic transition values of Ni–Co ferrite lie between 863 and 793K. ► Unusual electric and dielectric behavior well above room temperature is discussed.Nanocrystalline samples of Ni xCo1– xFe2O4, where x=1, 0.8, 0.6, 0.4, 0.2 and 0, were synthesized by chemical co-precipitation method. The spinel cubic phase formation of Ni–Co ferrite samples was confirmed by X-ray diffraction (XRD) data analysis. All the Bragg lines observed in XRD pattern belong to cubic spinel structure of ferrite. Scanning Electron Microscopy (SEM) technique was used to study the surface morphology of the Ni–Co ferrite samples. Nanocrystalline size of Ni–Co ferrite series was observed in SEM images. Pellets of Ni–Co ferrite were used to study the electrical and dielectric properties. The resistivity measurements were carried out on the samples in the temperature range 300–900K. Ferrimagnetic to paramagnetic transition temperature ( T c) for all samples was noted from resistivity data. The activation energy below and above T c was calculated. The dielectric constant ( ɛ′) measurements with increasing temperature show two peaks in the temperature range of measurements for all samples under investigation. The peaks observed show frequency and compositional dependences as a function of temperature. Electrical and dielectric properties of nanocrystalline Ni xCo1– xFe2O4 samples show unusual behavior in temperature range of 500–750K. To our knowledge, nobody has discussed such anomalies for nanocrystalline Ni xCo1– xFe2O4 at high temperature. Here, we discuss the mechanism responsible for electrical and dielectric behavior of nanocrystalline Ni xCo1– xFe2O4 samples.
Keywords: A. Magnetic materials; C. X-ray diffraction; D. Dielectric properties; D. Electrical properties
Facile preparation of heterostructured Bi2O3/Bi2MoO6 hollow microspheres with enhanced visible-light-driven photocatalytic and antimicrobial activity
by Yang-Sen Xu; Ze-Jun Zhang; Wei-De Zhang (pp. 1420-1427).
Hierarchical β-Bi2O3/Bi2MoO6 flower-like microspheres assembled by nanosheets have been successfully prepared. The composites show dramatically enhanced visible-light photocatalytic activity for the degradation of RhB and inactivation of Escherichia coli. The highest efficiency is observed with the Bi/Mo molar ratio of 2.56/1 as the starting materials. The dramatic enhancement in the photocatalytic performance of the β-Bi2O3/Bi2MoO6 photocatalyst is discussed.Display Omitted► Hierarchical Bi2O3/Bi2MoO6 heterostructured hollow microspheres were prepared. ► Hollow microspheres composed of micro-/nanoplates. ► The Bi2O3/Bi2MoO6 composites exhibit superior visible-light photocatalytic activity. ► The hollow and heterojunction structures are responsible for the enhanced property.Hierarchical β-Bi2O3/Bi2MoO6 heterostructured flower-like microspheres assembled from nanoplates with different β-Bi2O3 loadings (0–26.5mol%) were synthesized through a one-step template-free solvothermal route. Under visible-light illumination ( λ>420nm), over 99% of rhodamine B was degraded within 90min on the 21.9mol% of β-Bi2O3 loading Bi2O3/Bi2MoO6 microspheres. The remarkable enhancement of photocatalytic activity of the hierarchical Bi2O3/Bi2MoO6 micro/nanostructures can be attributed to the effective separation of the photoinduced charge carriers at the interfaces and in the semiconductors. The electrons (e−) are the main active species in aqueous solution under visible-light irradiation. The Bi2O3/Bi2MoO6 also displays visible-light photocatalytic activity for the destruction of E. coli. In addition, the β-Bi2O3 in the hierarchical Bi2O3/Bi2MoO6 microspheres is very stable and the composite can be easily recycled by a simple filtration step, thus the second pollution can be effectively avoided. A possible photocatalytic mechanism was proposed based on the experimental results.
Keywords: A. Nanostructures; A. Oxides; A. Semiconductors; B. Chemical synthesis; D. Microstructure
An antibacterial macroporous polyurethane hybrid material with a high content of zinc ions: A template to uniform ZnO nanoparticles
by Gabriela Ambrožič; Jernej Šribar; Srečo D. Škapin; Majda Žigon; Zorica Crnjak Orel (pp. 1428-1434).
Display Omitted► Novel macroporous Zn-embedded polyurethane hybrid was prepared. ► The material exhibits extremely strong antibacterial properties against Escherichia coli. ► The calcination yields uniform ZnO nanoparticles indicating a high organic/inorganic compatibility.A simple method for the firm and effective in situ incorporation of zinc ions in a cross-linked polyurethane (PU) matrix containing isonicotinamide moieties is developed. The PU polymerization takes place in the presence of different concentrations of zinc acetate dihydrate (ZnAc), which acts both as a catalyst and a source of water molecules necessary for the formation of the porogenic agent (CO2). The textural porosity of the material increases with the increase of the initial concentration of ZnAc. The analyses of the as-prepared and/or isothermally annealed samples show a high compatibility between the cross-linked polymer matrix and the zinc ions derived from the ZnAc in all of the prepared hybrid materials. After the calcination the monodispersed and uniform ZnO nanoparticles are formed, indicating a uniform distribution of nucleation sites in the pre-calcinated hybrid materials. The antibacterial activity tests against Escherichia coli demonstrated that the macroporous sample obtained from 70wt% of ZnAc exhibits extremely strong biocidal properties.
Keywords: A. Composites; A. Oxides; A. Polymers; B. Chemical synthesis; B. Crystal growth
Giant dielectric permittivity and room temperature magnetodielectric study of BaTi0.2(Fe0.5Nb0.5)0.8O3 nanoceramic
by Piyush Kumar Patel; K.L. Yadav (pp. 1435-1438).
Display Omitted► Reporting synthesis of BaTi(1− x)(Fe0.5Nb0.5) xO3 ceramics with x=0.8 for first time. ► Enhanced dielectric constant ( ɛ∼15,000) with low loss (∼0.6) at room temperature. ► Reporting first time about presence of magnetocapacitance (∼8%) in the system.BaTi0.2(Fe0.5Nb0.5)0.8O3 [BTFN] ceramic was prepared by sol–gel method. X-ray diffraction pattern of the sample at room temperature shows a cubic phase. Microstructure analysis shows well-grown and dense grains in the sintered sample. High dielectric constant (∼15,000) with low loss (∼0.6) was found at room temperature at 1kHz frequency. Cole–Cole plot analysis shows that the grain boundary effect (barrier layer formation) is responsible for such a high value of dielectric constant. Another interesting feature of BTFN ceramic is the appearance of room temperature high magnetodielectric response (∼8%) at 9kOe magnetic field. Magnetodielectric effect was observed in the sample which is due to the Maxwell–Wagner polarization along with magnetoresistance.
Keywords: A. Ceramics; B. Sol–gel chemistry; C. Impedance spectroscopy; D. Dielectric properties
Fabrication, characterization, and magnetic properties of copper ferrite nanoparticles prepared by a simple, thermal-treatment method
by Mahmoud Goodarz Naseri; Elias B. Saion; Hossein Abasstabar Ahangar; Abdul Halim Shaari (pp. 1439-1446).
Display Omitted► An aqueous solution of PVA and metal nitrates was prepared at 353K. ► The mixed solution was heated at 373K to evaporate the water and the resulting solid was crushed to powder. ► The influence of calcination temperature on crystallinity, morphology and microstructure was characterized. ► Elemental composition, phase composition, magnetic properties and magnetic resonance were investigated.Tetragonal copper ferrite nanoparticles were fabricated by a thermal-treatment method by using a solution that contained poly(vinyl alcohol) (PVA) as a capping agent and Cu and Fe nitrates as alternative sources of metal. Heat treatment was conducted at temperatures between 673 and 823K, and final products had different crystallite sizes ranging from 11 to 42nm. The influence of calcination temperature on the degree of crystallinity, morphology, microstructure, and phase composition was investigated by different characterization techniques, i.e., X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscope (FESEM), and Fourier transform infrared (FT-IR) spectroscopy, respectively. The compositions of the samples were determined by energy dispersion X-ray analysis (EDXA), which revealed the presence of Cu, Fe, and O in the samples. The formed nanoparticles exhibited ferromagnetic behavior with unpaired electrons spins, which was confirmed by using a vibrating sample magnetometer (VSM) and electron paramagnetic resonance (EPR) spectroscopy.
Keywords: A. Metals; A. Magnetic materials; C. X-ray diffraction; D. Electronic paramagnetic resonance (EPR); D. Crystal structure; D. Magnetic properties
Synthesis of porous Fe3O4/g-C3N4 nanospheres as highly efficient and recyclable photocatalysts
by Xiaosong Zhou; Bei Jin; Ruqing Chen; Feng Peng; Yueping Fang (pp. 1447-1452).
Display Omitted► Novel porous Fe3O4/g-C3N4 nanospheres were designed and synthesized by a facile hydrothermal method. ► Porous Fe3O4/g-C3N4 nanospheres showed an expanding visible light absorption and considerable improved visible light photocatalytic activity. ► This structure exhibited excellent reusability and magnetic properties. ► The mechanism relies on photogenerated electrons and holes transfer between g-C3N4 and Fe3O4.A facile approach for the preparation of Fe3O4/g-C3N4 nanospheres with good porous structure has been demonstrated by a hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible light (UV–vis) absorbance spectra and X-ray photoelectron spectroscopy (XPS). The photocatalytic decomposition of methyl orange (MO) by the as-prepared samples was carried out under visible light irradiation. The reusability and magnetic properties were also investigated. The results revealed that the porous Fe3O4/g-C3N4 nanospheres showed considerable photocatalytic activity, and exhibited excellent reusability and magnetic properties with almost no change after five runs.
Keywords: Keyword; A. Nanostructures; A. Composites; B. Chemical synthesis; B. Catalytic properties
One-step hydrothermal synthesis, characterization and visible-light catalytic property of Ag-reduced graphene oxide composite
by Xian-hua Meng; Xin Shao; Huai-yong Li; Feng-zhen Liu; Xi-peng Pu; Wen-zhi Li; Chang-hua Su (pp. 1453-1457).
Display Omitted► Ag-RGO composites were synthesized via a facile one-step hydrothermal method. ► Glucose was used to reduce GO in the hydrothermal treatment. ► The Ag-RGO showed a high catalytic activity for the photodegradation of RhB.In this paper, a nanocomposite consisting of Ag nanoparticles and reduced graphene oxide sheets was synthesized via a one-step hydrothermal method using glucose as a reducing agent. The as-prepared sample was characterized systematically, and the results indicated that the graphene oxide was reduced and an Ag-reduced graphene oxide hybrid material was formed. It was shown that the as-prepared Ag-reduced graphene oxide was in a layered structure stacked by reduced graphene oxide sheets. The Ag nanoparticles decorated on the reduced graphene oxide sheets. The analysis revealed that there was strong interaction between the Ag nanoparticles and reduced graphene oxide sheets. A photodegradation study was also performed on the Ag-reduced graphene oxide composite. It showed that the composite exhibited a high catalytic activity for the photodegradation of Rhodamine B pollutant under visible-light irradiation, which made Ag-reduced graphene oxide a promising candidate as photocatalyst for Rhodamine B.
Keywords: A. Composites; B. Chemical synthesis; C. Thermogravimetric analysis; D. Catalytic properties
The effect of calcination conditions on the morphology, the architecture and the photo-electrical properties of TiO2 nanotube arrays
by Rui Liu; Liang-Sheng Qiang; Wein-Duo Yang; Hsin-Yi Liu (pp. 1458-1467).
Display Omitted► We fabricate well-ordered TiO2 nanotubes in formamide-based electrolyte. ► We use many characterizations to investigate properties of TiO2 nanotubes. ► We first discuss the effects of calcination conditions on efficiency of DSSC.Highly ordered TiO2 nanotube arrays were successfully prepared by electrochemical anodization in a formamide-based electrolyte containing 0.5wt.% NH4F and 2vol.% H2O. The effects of the calcining temperature, the calcining time and the heating rate on the formation of the TiO2 nanotube arrays were investigated in detail. The morphological changes and phase transformations of the TiO2 nanotubes were analyzed by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It was found that the calcining temperature and the calcining time determined the crystal phase, while the heating rate was only beneficial to altering the crystallinity. UV–vis diffuse reflectance spectroscopy was used to examine changes in the band gap energy. For applications to dye sensitized solar cells, a maximum conversion efficiency was achieved at 500°C for 2h with a heating rate of 10°C/min, which is attributed to the highly crystalline anatase and the lower surface defect concentrations of the nanotubes. The optimum calcination conditions help to retard the electron recombination and allow higher dye absorption capacities, thereby increasing Voc and Jsc.
Keywords: Keyword; A. Thin films; B. Chemical synthesis; C. X-ray diffraction; B. electrochemical properties
Spectroscopic, microscopic, and electrical characterization of nanostructured SnO2:Co thin films prepared by sol–gel spin coating technique
by J. Mazloom; F.E. Ghodsi (pp. 1468-1476).
Display Omitted► Optical properties of the SnO2:Co nanostructured thin films have been investigated. ► The grain size of the samples was decreased with increasing of Co. ► The carrier type was changed from n-type to p-type in doping level above 3mol%. ► The direct optical band gap shifted to the lower energy. ► The green emission in PL spectra enhanced with Co doping.Cobalt doped SnO2 thin films were prepared by sol–gel spin coating technique and influence of dopant concentration on structural, morphological and optical properties of thin films were investigated by XRD, XPS, FTIR, SEM, AFM, PL, UV–vis, and Hall effect measurement. All samples have a tetragonal rutile structure and the grain size decreases with increasing the doping concentration. XPS results clearly showed the presence of Co2+ ions into the SnO2. The SEM and AFM images reveal that the morphology of samples was affected by dopant. Conductivity type of the films changes from n-type to p-type with increasing Co-dopant above 3mol% and electrical resistivity increases with increasing Co content. The optical band gap gradually decreases with improved cobalt concentration from 3.91eV to 3.70eV. The PL measurements revealed the decrease in intensity of blue emission lines and increase in green emission when content of Co is enhanced in the thin films.
Keywords: PACS; 78.20.Ci; 81.20.Fw; 73.61.−r; 73.63.BdA. Thin film; B. Electrical properties; B. Sol–gel; D. Optical properties
Preparation and corrosion behavior of Ni and Ni–graphene composite coatings
by C.M. Praveen Kumar; T.V. Venkatesha; Rajashekhara Shabadi (pp. 1477-1483).
The graphite oxide was synthesized from the Hummers method, and then it was reduced by hydrazine hydrate to obtain graphene and then it was characterized from UV (ultra violet), IR (infra red), XRD (X-ray diffraction) spectra and SEM (scanning electron microscope) images.Display Omitted► Graphene was synthesized from the graphite oxide. ► Ni and Ni graphene coatings were synthesized. ► Corrosion resistance properties of pure Ni and its composite were compared.The graphite oxide was synthesized using the Hummers method, and then it was reduced by hydrazine hydrate to obtain graphene. It was characterized with UV (ultra violet), IR (infra red), XRD (X-ray diffraction) spectra and SEM (scanning electron microscope) images. The composite coating of Ni–graphene on mild steel specimens was obtained by the electrodeposition technique. The composite coating was subjected to various electrochemical tests to know its corrosion behavior and compared with pure Ni coating. The EIS (electrochemical impedance spectroscopy) was performed to confirm the corrosion resistance property. The composite film was studied by recording its XRD and SEM. The crystallite size, texture coefficients and hardness of coating was measured.
Keywords: A. Composites; B. Chemical synthesis; C. X-ray diffraction
One-step synthesis of copper nanoparticles embedded in carbon composites
by Jung Yoon Seo; Hyun Woo Kang; Dae Soo Jung; Hye Moon Lee; Seung Bin Park (pp. 1484-1489).
Copper nanoparticles of 30–50nm were incorporated in carbon composites when the same mass of PVP was added in precursor solution while the concentration of copper nitrates was fixed. XPS results demonstrated that copper nanoparticles were effectively protected from oxidation.Display Omitted► Cu/carbon composites were prepared by one-step spray pyrolysis. ► Morphological changes of powders were shown by varying the PVP to Cu salt ratio. ► Carbon played an important role in improving air-stability of Cu nanoparticles. ► The surface plasmon band of Cu/C composites was shifted toward high wavelengths.Copper nanoparticles embedded in carbon composites were prepared via spray pyrolysis by adjusting the polyvinylpyrrolidone (PVP) to copper nitrate mass ratio. When the equal amount of two precursors was mixed and spray pyrolyzed, copper nanoparticles with sizes in the range 30–50nm were incorporated into the carbon composites arising from PVP. X-ray photoelectron spectroscopy demonstrated that the copper nanoparticles exhibit oxidation resistance. In addition, the effects of carbon on the surface plasmon bands were investigated. This synthetic process is simple and environmentally friendly and reduces the problems associated with their oxidation through one-step passivation.
Keywords: A. Composites; B. Chemical synthesis; C. Electron microscopy; C. Photoelectron spectroscopy; D. Optical properties
Synthesis, characterization, EPR and thermoluminescence properties of CaTiO3 nanophosphor
by M. Shivaram; R. Hari Krishna; H. Nagabhushana; S.C. Sharma; B.M. Nagabhushana; B.S. Ravikumar; N. Dhananjaya; C. Shivakumara; J.L. Rao; R.P.S. Chakradhar (pp. 1490-1498).
Packing diagram of CaTiO3 prepared by MSS method.Display Omitted► Orthorhombic CaTiO3 nanophosphor was synthesized by three different routes. ► Well characterized by PXRD, SEM, TEM, FTIR, UV–vis spectroscopy. ► EPR spectrum reveals that g=2.027 signal and is attributed to [TiO6]9− center. ► Subjected to γ-irradiation and TL behavior has been studied for the first time. ► Trapping parameters have been evaluated and discussed in detail.Calcium titanate (CaTiO3) nanophosphors were synthesized by three different routes namely solution combustion (SC), modified solid-state reaction (MSS) and solid-state (SS) methods. Rietveld refinement studies revealed the presence of an orthorhombic structure with traces of CaCO3. The crystallite sizes were found to be in the 43–45nm range. TEM studies also confirm the nano size with well crystalline nature. EPR spectrum for SS method exhibits a broad resonance signal at g=2.027 is attributed to [TiO6]9− center, whereas in MSS sample the resonance signals are attributed to surface electron and hole trapping sites. The TL behavior has been investigated for the first time using γ-irradiation. TL glow peak at 169°C were recorded in CaTiO3 prepared by SC, MSS and SS methods. The trapping parameters such as activation energy ( E) and order of kinetics ( b) were estimated using peak shape method and results are discussed in detail.
Keywords: A. Oxides; B. Chemical synthesis; C. X-ray diffraction; D. Electronic paramagnetic resonance; D. Luminescence
Synthesis, characterization, and its photocatalytic activity of double-walled carbon nanotubes-TiO2 hybrid
by Changwei Liu; Haibo Chen; Ke Dai; Aifang Xue; Hao Chen; Qiaoyun Huang (pp. 1499-1505).
DWCNT-TiO2 hybrid prepared by hydrothermal method showed excellent visible-light photocatalytic activity, which is better than that of MWCNT-TiO2 or SWCNT-TiO2 hybrid. In addition, DWCNT-TiO2 with longer tubes showed better visible light photoactivity.Display Omitted► The introduction of DWCNT provides TiO2 with visible light photoactivity. ► DWCNT-TiO2 showed better photocatalytic activity than MWCNT-TiO2 or SWCNT-TiO2. ► DWCNT-TiO2 with longer nanotubes showed better visible light photoactivity.Double-walled carbon nanotube (DWCNT)-TiO2 hybrid was prepared by hydrothermal method and characterized by X-ray diffraction, electron microscopy, N2-adsorption analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of DWCNT-TiO2 hybrid was tested by the photocatalytic degradation of sulfathiazole. The experimental results showed that the introduction of the DWCNTs provides DWCNT-TiO2 hybrid with visible light-induced photoactivity and a large surface area. The DWCNTs were coated with TiO2 nanoparticles, which generated an intimate contact between the DWCNTs and TiO2. The DWCNT-TiO2 hybrid showed an excellent visible-light-induced activity, compared with multi-walled carbon nanotube-TiO2 and single-walled carbon nanotube-TiO2 hybrids, which can be attributed to the unique electronic structure of the DWCNTs that can work well as not only a photosensitizer but also an electron conductor. In addition, DWCNT-TiO2 hybrid with the DWCNTs of long length showed higher degradation efficiency than that with the short length.
Keywords: A. Composites; A. Fullerenes; A. Organic compounds; A. Semiconductors; D. Catalytic properties
Temperature dependent neutron diffraction and Mössbauer studies in zinc ferrite nanoparticles
by Jeevan Job Thomas; A.B. Shinde; P.S.R. Krishna; Nandakumar Kalarikkal (pp. 1506-1511).
Display Omitted► Micro-level magnetic alignments of zinc ferrite nanoparticles. ► Magnetization behavior clearly indicates the presence of superparamagnetism. ► Cation distribution shows a change from normal spinel structure. ► Structural parameters found vary with temperature which affects magnetic moments. ► Coexisting ferri and antiferromagnetic spins influence overall magnetic structure.The micro-level magnetic alignments of zinc ferrite nanoparticles synthesized by sol–gel method were investigated using magnetization study, neutron diffraction and Mössbauer spectroscopy. Magnetization behavior of the sample clearly indicates the presence of superparamagnetism. The neutron diffraction was performed at seven different temperatures between 6K and 300K. The cation distribution is found to have a variation from the from normal spinel structure. Both A and B site magnetic moment values found to vary with temperature which is found to correlates with variations in bond lengths and lattice constants. The Mössbauer spectrum at room temperature shows typical doublet while the spectrum 5K shows well defined sextet. The two sub-spectra in the sextet resolves well by the application of 5T magnetic field and the noncollinear nature of magnetic alignment with in the tetrahedral and octahedral sites of zinc ferrite are deduced.
Keywords: A. Magnetic materials; A. Nanostructures; B. Sol–gel chemistry; C. Mössbauer spectroscopy; C. Neutron scattering
Facile fabrication of ibuprofen–LDH nanohybrids via a delamination/reassembling process
by Xiaomei Lu; Liming Meng; Haiping Li; Na Du; Renjie Zhang; Wanguo Hou (pp. 1512-1517).
Ibuprofen intercalated layered double hydroxide (LDH) nanohybrid was successfully synthesized via a delamination/reassembling process. This method shows various remarkable advantages, such as simple procedure, short reaction time, mild condition, and high drug loading.Display Omitted► IBU–LDH nanohybrid was synthesized via a delamination/reassembling process. ► This method shows various advantages compared with conventional methods. ► The loading amount of IBU can exceed that determined by the charge-balancing law.In this paper, a delamination/reassembling method for the facile fabrication of ibuprofen (IBU), a non-steroidal anti-inflammatory drug, intercalated layered double hydroxide (LDH) nanohybrid was presented. In this method, LDH particles were first delaminated to well dispersed 2D nanosheets in formamide, and then the LDH nanosheets and IBU molecules coassembled into the IBU–LDH nanohybrid. The characteristics of the so-synthesized nanohybrid were the same as that of the IBU–LDH nanohybrids synthesized by the conventional methods including ion exchange, co-precipitation, reconstruction and hydrothermal methods. However, the delamination/reassembling method displayed various remarkable advantages, such as simple procedure, short reaction time, mild condition and high drug loading, compared with the conventional methods.
Keywords: A. Layered compounds; A. Nanostructures; B. Intercalation reactions; C. X-ray diffraction
2D SnO2 nanorod networks templated by garlic skins for lithium ion batteries
by Rui Mao; Hong Guo; Dongxue Tian; Depeng Zhao; Xiangjun Yang; Shixiong Wang; Jing Chen (pp. 1518-1522).
Display Omitted► 2D SnO2 nanorod network materials are synthesized by using garlic skins. ► The prepared SnO2 nanorods with length of ca. 80nm possess high BET surface area of 163.25m2g−1. ► Stable discharge capacities of ca. 620 and 560mAhg−1 are obtained at the current density of 100 and 500mAg−1, respectively.SnO2 nanorods with 2D network structure prepared via an effective method of using the skins of garlic bulbs as templates are examined as anode materials for Li-ion battery. The samples are composed of SnO2 nanorods with length of ca. 80nm and possess high BET surface area of 163.25m2g−1. The synthesized SnO2 electrode shows a high specific capacity (ca. 620mAhg−1), an excellent cycling stability and a good rate capability but low initial coulombic efficiency. The nanorods characteristics of SnO2 ensure the fast Li-ion diffusion in the electrode. The loose network structure provides the electrode with a sufficient void space, which sufficiently alleviates the mechanical stress caused by volume change, and thus avoids the electrode to pulverize in the charge–discharge process. Therefore, the obtained SnO2 electrode shows a good cyclic stability and a high rate performance.
Keywords: A. Nanostructures; B. Sol–gel chemistry; C. Electron microscopy; D. Energy storage
Silver nanoparticles preferentially reduced on PEG-grafted glass surfaces for SERS applications
by Sang-Myung Lee; Hong-Jun Cho; Ji Yun Han; Hyo-Jin Yoon; Kwang-Ho Lee; Dae Hong Jeong; Yoon-Sik Lee (pp. 1523-1529).
Uniform silver nanoparticles of ∼50nm size were easily generated by dipping the PEG-grafted glass surfaces in silver salt solution at room temperature without any additional reducing agent.Display Omitted► Uniform silver nanoparticles of 50-nm size can be generated on PEG2000-grafted glass without any additional reducing agents. ► Hydroxy group of PEG spacer plays the role of the reducing agent for formation of silver nanoparticles. ► The length of PEG is an important factor to control the size of sliver nanoparticles.Silver nanomaterials have been extensively investigated due to their unique optical and biological properties. Surface plasmons and scattering phenomena occurring on silver nanostructures can provide useful analytical or sensor platform. Here, we present silver nanoparticles preferentially reduced on polyethylene glycol (PEG)-grafted glass surfaces for application to surface-enhanced Raman scattering (SERS). Uniform silver nanoparticles of ∼50nm size were easily generated by dipping the PEG-grafted glass surfaces in silver salt solution at room temperature without any additional reducing agent. The silver nanoparticles generated on the PEG-grafted surfaces were confirmed by AFM and FE-SEM analysis.
Keywords: A. Silver nanoparticles; B. Chemical synthesis; C. Atomic force microscopy; D. Optical properties
Encapsulation of CdSe/ZnS nanocrystals within mesoporous silica spheres
by Jingting Song; Shaojue Wu; Yanli Zhao (pp. 1530-1535).
Display Omitted► Approach for fabrication of mesoporous silica coated CdSe/ZnS was developed. ► Different morphologies were achieved by simply changing the reaction conditions. ► Hybrid materials obtained present unique fluorescent properties. ► Synthetic process is easy to operate and cost-effective.Quantum dots (QDs) have attracted much attention on account of their unique optical and electronic properties. Applications of QDs in biological systems face challenges owing to their toxicity and hydrophobicity. Incorporation of QDs in mesoporous silica spheres affords not only hydrophilic shell for QDs in order to enhance their dispersion in aqueous medium, but also offers chemically inert shielding to reduce QD cytotoxicity. In the current work, two types of mesoporous silica encapsulated QDs were synthesized by rationally adjusting the reaction conditions. Mesoporous silica coated single CdSe/ZnS nanoparticles (sCdSe/ZnS@mSiO2) were prepared through the one-pot reaction. Further modification of this reaction offered hollow mesoporous silica spheres (CdSe/ZnS@HMSS) encapsulating multiple CdSe/ZnS QDs assembled on the internal surface of the spheres. Both of sCdSe/ZnS@mSiO2 and CdSe/ZnS@HMSS show significant photophysical properties. Possible formation mechanism of the two types of nanostructures was investigated and discussed.
Keywords: A. Nanostructures; A. Optical materials; A. Structural materials; B. Chemical synthesis; D. Optical properties
High surface area carbonate apatite nanorod bundles: Surfactant-free sonochemical synthesis and drug loading and release properties
by Chao Qi; Ying-Jie Zhu; Xin-Yu Zhao; Jing Zhao; Feng Chen; Guo-Feng Cheng; Yin-Jie Ruan (pp. 1536-1540).
We report a simple surfactant-free sonochemical synthesis of carbonate apatite nanorod bundles with high specific surface areas. The as-prepared carbonate apatite nanorod bundles are explored as the drug nanocarrier, which exhibit a sustained drug release behavior in simulated body fluid.Display Omitted► A simple surfactant-free sonochemical method has been demonstrated. ► Carbonate apatite nanorod bundles with high specific surface areas are obtained. ► Effects of experimental parameters on the product are investigated. ► Carbonate apatite nanorod bundles exhibit sustained drug release.The design and synthesis of calcium phosphates (CPs) nanostructures with high specific surface areas are significant for drug delivery systems. Herein, we report a simple surfactant-free sonochemical synthesis of carbonate apatite (CAP) nanorod bundles with a high specific surface area (183.39m2g−1) using an aqueous solution of CaCl2·2H2O and (NH4)2HPO4. The effects of experimental parameters including reactant species, pH value, calcium ion concentration, reaction time on the specific surface area of the product were investigated. The products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-prepared CAP nanorod bundles were explored as the drug nanocarrier, which exhibited a sustained drug release behavior in simulated body fluid.
Keywords: A. Nanostructures; B. Chemical synthesis
Preparation of N-methylaniline capped mesoporous TiO2 spheres by simple wet chemical method
by T. Prakash; M. Navaneethan; J. Archana; S. Ponnusamy; C. Muthamizhchelvan; Y. Hayakawa (pp. 1541-1544).
Display Omitted► Pure anatase TiO2 mesoporous nanospheres were prepared by wet chemical method. ► The average diameter of the TiO2 mesoporous nanospheres was found to be 600nm. ► Morphology can be controlled by adjusting the concentration of N-methylaniline.Pure anatase mesoporous TiO2 nanospheres were synthesized by simple wet chemical treatment and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis), Fourier transform infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD). The results revealed that the surface morphology of the TiO2 spheres could be controlled by adjusting the concentration of N-methylaniline and that the average diameter of the TiO2 spheres was 600nm. FTIR results confirmed the formation of N-methylaniline capped TiO2 nanospheres.
Keywords: A. Semiconductors; A. Nanostructures; B. Chemical synthesis; C. X-ray diffraction; D. Optical properties
Low temperature growth of SnO2 nanowires by electron beam evaporation and their application in UV light detection
by R. Rakesh Kumar /; K. Narasimha Rao; K. Rajanna; A.R. Phani (pp. 1545-1552).
Display Omitted► First time, SnO2 nanowires growth has been done by e-beam evaporation method. ► The growth of SnO2 nanowires has been taken at low substrate temperature of 450°C. ► Grown nanowires were single crystalline in nature and pure. ► Fabricated photo detector has shown reproducible photo response to UV light.For the first time, high quality tin oxide (SnO2) nanowires have been synthesized at a low substrate temperature of 450°C via vapor–liquid–solid mechanism using an electron beam evaporation technique. The grown nanowires have shown length of 2–4μm and diameter of 20–60nm. High resolution transmission electron microscope studies on the grown nanowires have shown the single crystalline nature of the SnO2 nanowires. We investigated the effect of growth temperature and oxygen partial pressure on SnO2 nanowires growth. Variation of substrate temperature at a constant oxygen partial pressure of 4×10−4mbar suggested that a temperature equal to or greater than 450°C was the best condition for phase pure SnO2 nanowires growth. The SnO2 nanowires grown on a SiO2 substrate were subjected to UV photo detection. The responsivity and quantum efficiency of SnO2 NWs photo detector (at 10V applied bias) was 12A/W and 45, respectively, for 12μW/cm2 UV lamp (330nm) intensity on the photo detector..
Keywords: A. Nanostructures; B. Vapor deposition; C. Electron microscopy; D. Microstructure; D. Surface properties
Synthesis and characterization of nanocrystalline ferroelectric Sr0.8Bi2.2Ta2O9 by conventional and microwave sintering: A comparative study
by Sugandha; A.K. Jha (pp. 1553-1559).
Comparison of dielectric constant with sintering temperature for conventional sintered (1100°C) sample and microwave sintered (1000°C and 1100°C) sample.Display Omitted► In this report Sr0.8Bi2.2Ta2O9 compounds have been synthesized. ► Synthesis was carried out by microwave sintering and solid-state reaction processes. ► The synthesized specimens were characterized for their structural and electrical properties. ► A comparative study reveals that microwave sintered specimen possesses superior properties.In recent years mechanical activation technique has been utilized to synthesize the nanocrystalline form of compounds resulting in enhancement in the properties. Also, microwave sintering is being preferred over conventional sintering due to rapid processing and uniform temperature distribution throughout the specimen. In the present work, nanocrystalline non-stoichiometric strontium bismuth tantalate (SBT) of the composition Sr0.8Bi2.2Ta2O9 ferroelectric ceramics were synthesized by microwave sintering process (with sintering temperatures of 1000°C and 1100°C) and conventional solid state reaction process (with sintering temperature of 1100°C) with an objective of comparing the properties of the synthesized specimens by the two processes. X-ray diffraction analysis shows the formation of single phase layered perovskite structure formation by both the processes. Scanning electron microscopy reveals the formation of a finer granular microstructure in the specimen synthesized by microwave sintering compared to that in the specimen prepared by conventional sintering. The specimen prepared by microwave sintering process exhibits improved electrical properties with higher dielectric constant, higher piezoelectric and pyroelectric coefficients and lower dielectric loss.
Keywords: A. Ceramics; A. Nanostructures; C. X-ray diffraction; D. Dielectric properties; D. Piezoelectricity
Preparation and characterization of CdSe and PbSe nanoparticles via aqueous solution for nanoparticle-based solar cells
by Jianzi Li; Jian Xu; Lixia Zhao; Qingbo Xu; Gang Fang (pp. 1560-1568).
Monodispersed CdSe and PbSe nanoparticles (NPs) as the building blocks could be applied to the all-inorganic nanoparticle solar cells and quantum-dot based solar cells. In the present work, a low-cost preparation route to monodispersed CdSe NPs and PbSe NPs with the particle sizes less than their Bohr radii was present. CdSe NPs and PbSe NPs were synthesized with different preparation conditions, using non-toxic chemicals such as the soluble starch as the surfactant and sodium citrate as the chelating agent in aqueous solutions. The effect of preparation conditions on the size (∼3–4nm) of monodispersed cubic phase CdSe NPs, their optical absorption and photo-luminescent spectra were investigated by various measurements and discussed with Brus’ effective mass model. Monodispersed cubic phase PbSe NPs with ca. 30–40nm in size were also obtained, but the smaller sized (<10nm) PbSe colloids could not be stabilized by the starch. Further modification need be done to prevent the smaller sized PbSe NPs from growing up.Display Omitted► A low-cost route to CdSe and PbSe NPs with smaller sizes than their Bohr-radii. ► Preparations were performed in aqueous solutions, using non-toxic chemicals. ► Optical properties of the NPs were discussed with Brus’ effective mass model.Monodispersed CdSe and PbSe nanoparticles (NPs) as the building blocks could be applied to the all-inorganic nanoparticle solar cells and quantum-dot based solar cells. In the present work, a low-cost preparation route to monodispersed CdSe NPs and PbSe NPs with the particle sizes less than their Bohr radii was present. CdSe NPs and PbSe NPs were synthesized with different preparation conditions, using non-toxic chemicals such as the soluble starch as the capping agent and sodium citrate as the chelating agent of metal ions in aqueous solutions. The effect of preparation conditions on the particle size (∼3–4nm) of monodispersed cubic phase CdSe NPs, their optical absorption and photo-luminescent spectra were investigated by various measurements and discussed with Brus's effective mass model. Monodispersed cubic phase PbSe NPs with ca. 30–40nm in size were also obtained, but the smaller sized (<10nm) PbSe colloids could not be stabilized by this capping agent starch. Further modification need be done to prevent the smaller sized PbSe NPs from growing up.
Keywords: A. Nanostructures; A. Semiconductors; C. X-ray diffraction; D. Luminescence
Microstructural evolution and optical properties of TiO2 synthesized by eggshell membrane templating for DSSCs application
by R. Camaratta; A.N. Correia Lima; M.D. Reyes; M.A. Hernández-Fenollosa; J. Orozco Messana; C.P. Bergmann (pp. 1569-1574).
Display Omitted► TiO2 was obtained by mimetization of eggshell membranes (ESM). ► Three temperatures of thermal treatment were investigated (600, 700 and 800°C). ► The optical properties were investigated by UV–vis diffuse reflectance. ► The morphology of the ESM was replicated in form of nanocrystalline TiO2. ► It was obtained samples with good porosity, bandgap and crystallinity for DSSCs.This article presents the bio-inspired synthesis of TiO2 using eggshell membranes (ESM) as a biotemplate on which the crystals of TiO2 are nucleated and grown. The microstructure, phase transformations and optical behavior were studied with the objective of understanding the effects of the thermal treatment on the properties of the TiO2 powder for application in dye sensitized solar cells (DSSC). The technique used for the mimetization of the ESM consists of submerging the biotemplate in an alcoholic solution of TiCl4 and thermal treating the samples at 600, 700 and 800°C. Thermal analysis (DTA and TGA) was used to investigate the thermal decomposition of the membranes. X-ray diffraction (XRD) studies revealed the phase evolution and the average crystal sizes. Scanning and transition electron microscopy (SEM and TEM, respectively) were used to investigate the morphology of the obtained powders. UV–vis diffuse reflectance was used to investigate the optical properties. The porosity was also evaluated using a BET instrument. The results indicated that the best features for DSSC application were presented by the sample that was thermally treated at 600°C. This is reflected in the good replication of the morphology of the used biotemplate, with a nanocrystalline anatase phase (average crystal size 15.82nm), high surface area (64.8m2/g), mesoporous structure (average pore size of 26.31Å) and large band gap (3.31eV).
Keywords: A. Semiconductors; B. Chemical synthesis; D. Microstructure; D. Optical properties
A facile synthesis of mesoporous graphene-tin composites as high-performance anodes for lithium-ion batteries
by Wenbo Yue; Sheng Yang; Yunling Liu; Xiaojing Yang (pp. 1575-1580).
Graphene–Sn composites with mesoporous structure are synthesized by a facile method and explored as anode materials for lithium-ion batteries. Sn nanoparticles with diameter under 5nm are reduced by NaBH4 solution and aggregate on the graphene surface to form the mesostructure. Compared to pure Sn particles, mesoporous graphene–Sn composites with large surface area exhibit superior electrochemical behaviors, especially after hydrothermal treatment.Display Omitted► A facile synthesis of graphene–Sn composites with mesoporous structure is proposed. ► Sn nanoparticles aggregate on the graphene surface to form the mesostructure. ► Mesoporous graphene–Sn composites exhibit improved electrochemical properties.Graphene-based metals and their oxides usually exhibit enhanced electrochemical behavior in lithium-ion batteries due to the outstanding properties of graphene. Moreover, the structure and morphology of electrodes can also take an important role in their electrochemical properties. Herein we describe a facile synthesis of graphene–Sn composites containing ca. 3–6nm diameter mesopores formed by aggregation of Sn nanoparticles on the graphene surface. These mesoporous composites with large surface area deliver higher capacity and better cycle performance in comparison with pristine Sn particles. Furthermore, the mesoporous composites treated under hydrothermal treatment exhibit higher rechargeable capacities and cycle performances.
Keywords: A. Composites; B. Chemical synthesis; B. Electrochemical properties
ZnO films and nanorod/shell arrays electrodeposited on PET-ITO electrodes
by Mariana Sima; Eugeniu Vasile; Marian Sima (pp. 1581-1586).
Display Omitted► A pulsed electrodeposition technique was used for producing ZnO films on PET-ITO. ► A ZnO nanorod/shell array was prepared on PET-ITO electrode. ► A ZnO nanorod/shell-Cu2O film solar cell was achieved on the PET-ITO support.In this work, ZnO films, nanorod and nanorod/shell arrays were synthesized on the surface of PET-ITO electrodes by electrochemical methods. ZnO films with high optical transmittance were prepared from a zinc nitrate solution using a pulsed current technique with a reduced pulse time (3s). The X-ray diffraction pattern of ZnO film deposited on PET-ITO electrode showed that it has a polycrystalline structure with preferred orientations in the directions  and . ZnO nanorods were synthesized on electrochemical seeded substrate in an aqueous solution containing zinc nitrate and hexamethylenetetramine. In order to increase the stability of PET-ITO electrode to electrochemical and chemical stresses during ZnO nanorods deposition the surface of the electrode was treated with a 17wt% NH4F aqueous solution. Electrochemical stability of PET-ITO electrode was evaluated in a solution containing nitrate ions and hexamethylenetetramine. ZnO nanorod/shell arrays were fabricated using eosin Y as nanostructuring agent. Photoluminescence spectra of ZnO nanorod and ZnO nanorod/shell arrays prepared on the surface of PET-ITO electrode were discussed comparatively. By employing the 1.5μm-length ZnO nanorod/shell array covered with a Cu2O film a photovoltaic device was fabricated on the PET-ITO substrate.
Keywords: A. Electronic materials; A. Nanostructures; C. Electrochemical measurements
A low temperature synthesis of nanocrystalline spinel NiFe2O4 and its electrochemical performance as anode of lithium-ion batteries
by Haowen Liu; Hua Zhu; Hanmin Yang (pp. 1587-1592).
Display Omitted► Nanocrystalline spinel NiFe2O4 has been synthesized at a low temperature. ► The obtained samples were investigated by TG, FTIR, TEM, XRD and CV. ► The obtained powders were charge–discharged at 0.2mAcm−2 in 0.0–3.0V. ► The sample calcined at 700°C was tested at various current densities in 0.0–3.0V. ► The prepared NiFe2O4 indicates a higher initial discharge capacity (1400mAhg−1).Nanocrystalline spinel NiFe2O4 was synthesized by a novel low temperature route. The crystal structure, composition and morphology of the as-prepared powder were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The average diameter of the particles prepared at 700°C is about 30nm. The electrochemical reaction mechanism and charge–discharge mechanism of the nanocrystalline NiFe2O4 were proposed based on thermogravimetric analysis (TGA) and cyclic voltammogram study. The charge–discharge tests indicated that the sample calcined at 700°C shows the highest initial discharge capacity (1400mAhg−1) attributed to the nanometer size and the better crystallinity of the powder. A discharge capacity stabilizes at about 600mAhg−1 after 10 cycles. The columbic efficiency is improved. The synthesis method is relatively low cost and convenient for large-scale production.
Keywords: A. Inorganic compounds; B. Chemical synthesis; C. X-ray diffraction; D. Electrochemical properties
Synthesis, structural and magnetic characterization of highly ordered single crystalline BiFeO3 nanotubes
by L.A.S. de Oliveira; K.R. Pirota (pp. 1593-1597).
Display Omitted► Highly ordered BiFeO3 nanotubes with 65nm of diameter and 3μm of length. ► Its morphology is smooth revealing, by TEM, a single crystalline structure. ► Suppression of the antiferromagnetic helical order giving rise to ferromagnetism. ► The large length-to-diameter ratio of the BiFeO3 nanotubes induced an uniaxial shape anisotropy which is added to the magnetocrystalline anisotropy.In this work, we report on the fabrication of highly ordered single crystalline BiFeO3 (BFO) nanotubes by a sol–gel technique using two-step anodic aluminum oxide (AAO) as template. We prepared BFO nanotubes with dimensions of 65nm in diameter and 3μm in length, as confirmed by scanning electron microscopy (SEM) measurements. The obtained single crystalline nanotubes present the expected pure phase (BiFeO3) as confirmed by energy-dispersive X-ray spectroscopy (EDX), selected area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). In addition to the antiferromagnetic behavior, the magnetization curves of the BFO nanotubes also present a ferromagnetic response, which holds from 2 to 300K. This desirable behavior is associated to the break of the antiferromagnetic helical spin ordering of the BFO nanotubes. Besides the magnetocrystalline anisotropy, the large length-to-diameter ratio induced an uniaxial shape anisotropy, attested by the applied magnetic field angle measurements.
Keywords: A. Nanostructures; B. Chemical synthesis; C. Electron microscopy; D. Magnetic properties
Fluorine intercalation in the n=1 and n=2 layered manganites Sr2MnO3.5+ x and Sr3Mn2O6
by Eirin Sullivan; Lisa J. Gillie; Joke Hadermann; Colin Greaves (pp. 1598-1605).
Display Omitted► Sr2MnO3.5+ x and Sr3Mn2O6 are amenable to fluorine insertion reactions. ► Sr2MnO3.5+ xF y has K2NiF4-type structure ( a=3.8210(1)Å and c=12.686(1)Å. ► Sr3Mn2O6F y has different levels of fluorine content with y=1, 2, and 3.Fluorine insertion into the oxygen defect superstructure manganite Sr2MnO3.5+ x has been shown by transmission electron microscopy (TEM) to result in two levels of fluorination. In the higher fluorine content sections, the fluorine anions displace oxygen anions from their apical positions into the equatorial vacancies, thus destroying the superstructure and reverting to a K2NiF4-type structure ( a=3.8210(1)Å and c=12.686(1)Å). Conversely, lower fluorine content sections retain the Sr2MnO3.5+ x defect superstructure, crystallising in the P21/ c space group. Fluorine intercalation into the reduced double-layer manganite Sr3Mn2O6 occurs in a step-wise fashion according to the general formula Sr3Mn2O6F y with y=1, 2, and 3. It is proposed that the y=1 phase ( a=3.815(1)Å, c=20.29(2)Å) is produced by the filling of all the equatorial oxygen vacancies by fluorine atoms whilst the y=2 phase ( a=3.8222(2)Å, c=21.2435(3)Å) has a random distribution of fluorine anions throughout both interstitial rocksalt and equatorial sites. Neutron powder diffraction data suggest that the fully fluorinated y=3 phase ( a=3.8157(6)Å, c=23.666(4)Å) corresponds to the complete occupation of all the equatorial oxygen vacancies and the interstitial sites by intercalated fluorine.
Keywords: A. Oxides; A. Fluorides; C. Neutron scattering; C. X-ray diffraction; D. Crystal structure
Improvement of cycle stability at elevated temperature and high rate for LiNi0.5− xCu xMn1.5O4 cathode material after Cu substitution
by Ou Sha; Zhi Qiao; Shaoliang Wang; Zhiyuan Tang; Hao Wang; Xinhe Zhang; Qiang Xu (pp. 1606-1611).
Display Omitted► A series of LiNi0.5− xCu xMn1.5O4 cathode materials were synthesized via a sol–gel method. ► The improvement of cycle stability at 55°C by Cu substitution is firstly reported. ► The LiNi0.45Cu0.05Mn1.5O4 material could achieve 115mAhg−1 at 20C discharge rate. ► The capacity retention at 55°C is 98% after 100 cycles at 5 C discharge rate.A series of Cu-substituted LiNi0.5− xCu xMn1.5O4 ( x=0, 0.03, 0.05 and 0.08) spinels have been synthesized using a sol–gel method. The results demonstrate that when x=0.05, the sample (LiNi0.45Cu0.05Mn1.5O4) exhibits the best electrochemical performance, achieving 124.5mAhg−1 and 115.0mAhg−1 at the discharge rates of 5C and 20C with the capacity retention of 97.7% and 95.7% after 150 cycles, respectively. Besides, the excellent cycle stability at 55°C has been demonstrated to retain 96.8% of the maximum attainable discharge capacity (127.3mAhg−1) at the discharge rate of 5C after 100 cycles. These data indicate that the LiNi0.45Cu0.05Mn1.5O4 cathode material has the real potential to be used for high power and high energy lithium ion battery in electric vehicle applications.
Keywords: A. Inorganic compounds; B. Sol–gel chemistry; C. X-ray diffraction; D. Electrochemical properties
Experimental and theoretical characterization of semiorganic nonlinear optical materiall-leucine hydrobromide
by Soma Adhikari; Tanusree Kar (pp. 1612-1617).
Display Omitted► Optically transparent crystals of LEUBr were grown by solution growth method. ► Transmission spectrum of LEUBr was studied. ► Optical band gap of LEUBr is calculated and found to be 5.12eV. ► Hardness of LEUBr decrease with increase of load following ISE method. ► Hyperpolarizability of LEUBr was calculated by computational method.Semiorganic nonlinear optical materiall-leucine hydrobromide (LEHBr) has been synthesized and single crystals were grown by solvent evaporation method at a constant temperature of 35°C. CHN test, FTIR and XRD analysis were performed for identification of the material. Thermal and mechanical stability of the grown crystal were investigated by DTA-TGA analysis and microhardness measurement respectively. Suitability of LEHBr for NLO application was studied by optical transmission study and second harmonic generation (SHG) efficiency measurement. SHG efficiency was found to be 4 times of KDP. First hyperpolarizability, dipole moment and polarizability of LEHBr were calculated at the framework of Hartree–Fock (HF) with 6-311G(d) basis set. First order hyperpolarizability was found to be 3.233×10−33esu which is 4.9 times of urea.
Keywords: A. Optical materials; B. Crystal growth; C. Infrared spectroscopy; C. Thermogravimetric analysis; D. Mechanical properties
Mechanism and improvement of the visible light photocatalysis of organic pollutants over microcrystalline AgNbO3 prepared by a sol–gel method
by Weiming Wu; Shijing Liang; Yan Chen; Lijuan Shen; Rusheng Yuan; Ling Wu (pp. 1618-1626).
Display Omitted► Microcrystalline AgNbO3 photocatalyst was prepared by a sol–gel method. ► Its photocatalytic activity was systematically evaluated under visible light. ► AgNbO3 might be inclined to absorb and degrade cationic dyes such as MB and RhB. ► Holes were the major oxidation agents responsible for decomposing organic pollutants. ► The addition of AgNO3 greatly enhanced the photocatalytic activity of AgNbO3.Microcrystalline AgNbO3 photocatalysts were successfully prepared by a sol–gel method. The photocatalytic activities of the samples were evaluated by the degradation of various organic pollutants under visible light irradiation ( λ≥420nm). The results indicated that AgNbO3 was favorable for adsorbing cationic dyes such as rhodamine B and methyl blue, and its photocatalytic performances were dominated by the adsorption abilities for different organic pollutants. For the degradation of rhodamine B, the sample prepared at 650°C showed the highest photocatalytic activity and good stability due to its suitable surface area and crystallinity. On the basic of the experimental results, photo-induced holes were suggested as the main oxidation species for the pollutants decomposition over AgNbO3. Furthermore, the photocatalytic activity of AgNbO3 was greatly enhanced by the addition of an electron acceptor AgNO3. The enhanced photocatalytic mechanism was also discussed.
Keywords: A. Semiconductors; B.; Sol–gel; chemistry; D. Catalytic properties
Tunable white light emitting from mono Ce3+ doped Sr5(PO4)2SiO4 phosphors for light emitting diodes
by Shuangyu Xin; Yuhua Wang; Ge Zhu; Feng Zhang; Yu Gong; Yan Wen; Bitao Liu (pp. 1627-1631).
Display Omitted► White emitting phosphor Sr5(PO4)2SiO4:Ce3+ was prepared via the high temperature reaction. ► The luminescence property and thermal stability were evaluated upon UV irradiation. ► The energy transfer process between Ce1 and Ce2 has been confirmed and demonstrated.The photoluminescence properties of mono Ce3+ doped Sr5(PO4)2SiO4 (SPS) apatite phosphors, prepared via a solid-state reaction at high temperature, were investigated in the ultraviolet region. The white light can be realized by adjusting the contents of activator Ce3+ or the excitation wavelength. Upon 365nm excitation, SPS: 0.05Ce3+ shows bright white light (34.74% of YAG) with CIE color coordinates of (0.33, 0.34), a superior color-rendering index of 90 and correlated color temperature of 5603K, suitable for potential use based on 365nm UV-InGaN chip.
Keywords: B. Luminescence; D. Optical properties
Growth and properties of sodium tetraborate decahydrate single crystals
by Neeti Goel; Nidhi Sinha; Binay Kumar (pp. 1632-1636).
Display Omitted► Good quality crystals of sodium tetraborate were grown by slow evaporation method. ► Microhardness studies reveal crystal is hard in nature. ► Band gap of crystals was found to be 4.1eV by DRS study. ► PL emission peak is observed in ultraviolet region at 340nm. ► Activation energy for these crystals was found to be 2.05eV.Sodium tetraborate decahydrate (Na2B4O7·10H2O) single crystals were grown from aqueous solution by slow solvent evaporation method and its functional groups have been confirmed by FTIR. Grown crystals were found to be hard in nature ( n=1.8). From optical studies band gap of the material was found to be 4.1eV and PL emission peak was found at 340nm which can be due to annihilation self trapped excitons present in borate crystals. Dielectric constant was found to increase with temperature up to 70°C. Conductivity obeys Jonscher's power law as seen at different temperatures. Activation energy of the crystal was found to be 2.05eV.
Keywords: A. Inorganic compounds; B. Crystal growth; C. X-ray diffraction; D. Dielectric properties; D. Optical properties
Formation and thermo-assisted stabilization of luminescent silver clusters in photosensitive glasses
by Kevin Bourhis; Arnaud Royon; Gautier Papon; Matthieu Bellec; Yannick Petit; Lionel Canioni; Marc Dussauze; Vincent Rodriguez; Laurent Binet; Daniel Caurant; Mona Treguer; Jean-Jacques Videau; Thierry Cardinal (pp. 1637-1644).
Display Omitted► Luminescent silver clusters have been stabilized within a photosensitive glass. ► Combined effect of UV laser irradiation and heat treatment has been studied. ► Temperature is as a key parameter for the formation and stabilization of the clusters. ► Optical and magnetic signatures of the silver species have been evidenced.Various photo-induced silver luminescent centres were obtained in photosensitive zinc and phosphate glasses containing silver ions after exposure to gamma or ultraviolet nanosecond pulsed-laser radiation. Gamma-irradiation of the glasses results mainly in the formation within the glass of electron-trapped and hole-trapped silver centres as evidenced by optical absorption, luminescence and electron spin resonance spectroscopies. For the highest irradiation doses silver clusters are obtained. Under ultraviolet nanosecond pulsed-laser exposure similar species are generated along the beam propagation direction as proven by the analogous optical and luminescence signatures. In this case for high irradiation doses few silver clusters are created. The evolution of the luminescence spectra with respect to the temperature and to the duration of the heat treatment after ultraviolet nanosecond pulsed-laser irradiation evidences the presence of potential barriers determining the stability limits of some species such as the Ag2+ hole-trapped centres or the Agm x+ clusters composed of silver ions and silver atoms. A heat treatment of several hundreds of degrees is identified as a the key parameter for tailoring the optical properties and controlling the formation of Agm x+ clusters in the photosensitive glasses.
Keywords: A. Optical materials; B. Electronic paramagnetic resonance (EPR); B. Luminescence; D. Color centers; D. Optical properties
The influences of B dopant on the crystal structure and nucleation ability of TiCx in the Al melt
by Jinfeng Nie; Xiangfa Liu; Yuying Wu (pp. 1645-1650).
Display Omitted► Synthesis and characterization of TiCx particles doped with different B content. ► The doping effect of B in TiCx reflected on the XRD patterns. ► The grain refinement on pure Al of TiCx improved by B dopant.The influences of B dopant on the crystal structure of TiCx and nucleation efficiency on α-Al are investigated in this paper. It was found that B solute atoms in the melt easily diffused into the crystal lattice of TiCx, meanwhile the f.c.c. crystal structure was preserved according to the EDS and TEM analysis. The doping effect of B in TiCx was reflected on the X-ray diffraction (XRD) patterns, in which the diffraction peak of (200) plane rose correspondingly. TiCx showed strong (111) orientation, but shifted to strong (200) after trace B doped. Furthermore, the grain refining ability of TiCx with strong (200) orientation induced by B dopant on commercial pure Al was improved obviously and the excellent refining performance was kept in a long holding time, which indicated that the structural stability of TiCx was enhanced after B doped.
Keywords: Carbides; Crystal growth; X-ray diffraction; Crystal structure; Microstructure
Phase transitions of bulk and nanocrystalline La1− xSr xMnO3 ( x=0.35 and 0.37) perovskite manganite materials using in situ ultrasonic studies
by K. Sakthipandi; V. Rajendran; T. Jayakumar (pp. 1651-1659).
The temperature-dependent ultrasonic parameters show both normal and anomalous behaviors. The temperature at which the anomaly in velocity takes place is the Curie temperature ( TC) of the perovskite sample. The anomalies that occurred in the velocities at 375, 371, 371, and 366K are the TC for bulk La0.63Sr0.37MnO3 (BLSMO37), bulk La0.65Sr0.35MnO3 (BLSMO35), nano La0.63Sr0.37MnO3 (NLSMO37) and nano La0.65Sr0.35MnO3 (NLSMO35), respectively. It is observed that the TC value of NLSMO is lower than that of the corresponding BLSMO perovskite sample.Display Omitted► A sharp FM to PM transition for bulk La1− xSr xMnO3 perovskite samples. ► Absence of sharp FM to PM transition for nano La1− xSr xMnO3 perovskite samples. ► Study of nanostructured perovskite through observed anomalous at TC.La1− xSr xMnO3 perovskite manganite materials with two compositions, namely x=0.35 and 0.37, both at bulk and nanoscale, were prepared by solid-state reaction and sonochemical reactor methods, respectively. The magnetic phase transition temperature of the prepared bulk and nanosamples was evaluated by in situ ultrasonic velocity and attenuation measurements. A home-made experimental setup was used for in situ measurement of ultrasonic velocities and attenuation over a wide range of temperatures (from 300 to 400K). The observed anomalous lattice-softening behavior in the ultrasonic parameters was used to study the phase transition temperature (Curie temperature, TC), i.e., from paramagnetic to ferromagnetic phase, both in bulk and nanostructured perovskite samples. Further, the ultrasonic measurements confirmed that sharp and broad transitions occur in bulk and nanostructured perovskite manganite materials, respectively. The Curie temperature for nanostructured perovskite samples was lower than that for the corresponding bulk perovskite sample, which was clearly identified by ultrasonic measurements.
Keywords: A. Magnetic materials; C. Ultrasonic measurements; D. Elastic properties; D. Phase transitions
Preparation of TiO2 nanoparticles by using tripodal tetraamine ligands as complexing agent via two-step sol–gel method and their application in dye-sensitized solar cells
by Noshin Mir; Masoud Salavati-Niasari (pp. 1660-1667).
Display Omitted► Tripodal ligands have crucial effect on the particle size and agglomeration level. ► The symmetry of the complexing agent has a crucial role on the morphology. ► The reflectivity property is very important factor in efficiency of DSSC.The effect of different tripodal tetraamine ligands was investigated on the particle size, agglomeration level, optical and photovoltaic properties of TiO2 nanoparticle prepared via a two-step sol–gel method. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron spectroscopy (TEM), scanning electron microscopy (SEM), and UV–vis spectroscopy. The results showed that the symmetry of ligands has a crucial effect on the size and agglomeration level of the products. The optical and photovoltaic properties of the products were studied, as well. The reflectivity property of the samples due to different agglomeration sizes is shown to be very important factor in increasing conversion efficiency of DSSC.
Keywords: A. Nanostructures; A. Semiconductors, B. Sol–gel chemistry, D. Optical properties, D. Energy storage
Photocatalytic mineralization of carboxylic acids over Fe-loaded ZnS nanoparticles
by Natda Wetchakun; Burapat Incessungvorn; Khatcharin Wetchakun; Sukon Phanichphant (pp. 1668-1674).
Display Omitted► Fe-loaded ZnS nanoparticles were prepared by hydrothermal and impregnation methods. ► Physicochemical properties played a significant role on photocatalytic efficiency. ► All Fe-loaded ZnS samples showed higher photocatalytic activity than pure ZnS. ► Fast degradation of oxalic acid may be due to high hydroxyl radical present.Zinc sulfide (ZnS) nanoparticles prepared by hydrothermal synthesis were subsequentially impregnated with different iron amounts (0.5−5.0at%) to obtain Fe-loaded ZnS nanoparticles. Phase composition, crystallinity, crystal size, and morphology of 0.5–5.0at% Fe-loaded ZnS nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). Specific surface area determined by the Brunauer, Emmett and Teller (BET) method was found to be in the range of 85–197m2/g. The average particle size obtained from TEM analysis of pure ZnS and 2.0at% Fe-loaded ZnS nanoparticles was 5–20nm. The optical absorption properties of the samples measured by UV–vis diffuse reflectance spectroscopy (UV–vis DRS) clearly indicated the bathochromic shift upon loading ZnS with Fe. Photocatalytic activities of pure ZnS and Fe-loaded ZnS nanoparticles were examined by studying the mineralization of oxalic acid and formic acid under UVA illumination. It was found that 2.0at% Fe-loaded ZnS sample exhibited the highest degradation activity possibly due to the presence of Fe in an optimum amount and the increases of surface area and light absorption in UVA region.
Keywords: A. Nanostructures; B. Chemical synthesis; C. X-ray diffraction; D. Catalytic properties
Fabrication and electrogenerated chemiluminescence properties of uniform octahedral 8-hydroxyquinoline zinc (Znq2)
by Xi-Bao Chen; Xiao-Dong Yang; Xiao-Wei Hu; Chang-Jie Mao; Ji-Ming Song; He-Lin Niu; Sheng-Yi Zhang (pp. 1675-1680).
Display Omitted► 8-Hydroxyquinoline zinc (Znq2) octahedral have been successfully synthesized. ► The solvent, reaction time and temperature play an important effect in the morphology of the final product. ► A possible formation mechanism for Znq2 octahedra was proposed. ► The as-prepared Znq2 octahedral exhibited excellent electrogenerated chemiluminescence (ECL) behaviour.Well-defined octahedral Znq2 has been synthesized via a facile solvothermal route. Field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images show that the as-prepared product has an octahedral structure with an edge length of 2μm. The reaction parameters, such as solvent, reaction time and temperature, play an important part in the morphology of the final product. A possible formation mechanism for octahedral Znq2 is proposed. The as-prepared octahedral Znq2 exhibits excellent electrogenerated chemiluminescence (ECL) behaviour.
Keywords: B. Crystal growth; D. Crystal structure; D. Luminescence
Effect of silver incorporation into PVDF-barium titanate composites for EMI shielding applications
by Nina Joseph; Santosh Kumar Singh; Roopas Kiran Sirugudu; Vemuri Rama Krishna Murthy; Solaiappan Ananthakumar; Mailadil Thomas Sebastian (pp. 1681-1687).
Display Omitted► PVDF composite with nano BaTiO3, micro BaTiO3 and silver were prepared. ► The PVDF-BaTiO3-Ag composite exhibits shielding effectiveness of about 26dB. ► PVDF-nano BaTiO3-Ag composites shield mainly by absorption. ► Easily tunable, low cost EMI shielding material is obtained in the X band. ► PVDF-nano BaTiO3-Ag composites exhibit broad shielding band width over X band.Composites of polyvinylidene fluoride (PVDF) with micron and nano sized BaTiO3 powders were developed for electromagnetic interference (EMI) shielding applications in the X band. PVDF-nano BaTiO3 composites show better shielding property compared to PVDF-micron sized BaTiO3 composites. The composite of PVDF with 40vol% of nano BaTiO3 showed the best EMI shielding effectiveness and is about 9dB. The contributions from reflection and absorption to the total EMI shielding effectiveness is same for the PVDF-BaTiO3 composites. Addition of small amount of silver particles improved the shielding properties of these composites due to the increased conductivity. An EMI shielding effectiveness of about 26dB is obtained in the measured frequency range for the PVDF-20vol% nano BaTiO3-10vol% Ag composite of thickness 1.2mm. Novel three phase composite combining the advantages of metal, nano ceramic and polymer is obtained with the potential for effective EMI shielding applications.
Keywords: A. Ceramics; A. Composites; A. Metals; A. Polymers; D. Dielectric properties
Raman spectroscopy and dielectric properties of nanoceramic NdFeO3
by Sadhan Chanda; Sujoy Saha; Alo Dutta; T.P. Sinha (pp. 1688-1693).
Display Omitted► Raman spectroscopy and dielectric properties of nanoceramic NdFeO3. ► Sol–gel citrate method is used to prepare the nanoceramic. ► The size of nano crystallites are ranging from 45 to 75nm as obtained by TEM micrograph. ► Raman spectrum is fitted with the sum of 18 Lorentzian peaks. ► The relaxation mechanism of the sample is modeled by Cole–Cole equation.The nanoceramic NdFeO3 is synthesized by the sol–gel citrate method. The Rietveld refinement of X-ray diffraction pattern at room temperature (30°C) shows the orthorhombic Pnma phase with lattice parameters a=5.576Å, b=7.756Å, c=5.447Å. Nano-sized crystallites of NdFeO3 ranging from 45 to 75nm have been verified by the transmission electron microscope image. The room temperature Raman spectrum is fitted with the sum of 18 Lorentzian peaks. Eigen frequencies of vibrational modes are calculated using density functional theory under generalized gradient approximation and compared with experimental results. Dielectric spectroscopy study of NdFeO3 has been performed in the frequency range from 50Hz to 1MHz and in the temperature range from 50°C to 240°C. The frequency dependence of real and imaginary parts of dielectric permittivity is analyzed using Cole–Cole equation. The frequency dependent conductivity spectra follow the power law.
Keywords: A. Nanostructures; B. Sol–gel chemistry; C. Impedance spectroscopy; C. Raman spectroscopy; D. Dielectric properties
Phase and morphology evolution of bismuth ferrites via hydrothermal reaction route
by Xin Yang; Yanfang Zhang; Gang Xu; Xiao Wei; Zhaohui Ren; Ge Shen; Gaorong Han (pp. 1694-1699).
Display Omitted► Phase-controlled synthesis of Bi2Fe4O9 and BiFeO3 were realized by a facial hydrothermal route. ► KOH plays an important role in the phase formation and morphology evolution of the products. ► The layered structure feature and the differential affinity lead to the Bi2Fe4O9 nanoflakes. ► Pure BiFeO3 perovskite powders are of dense microparticles.Phase-controlled synthesis of bismuth ferrites has been achieved via hydrothermal route by adjusting the KOH concentration. The as-prepared powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. The particle morphologies of the as-prepared powders evolve from nanoflakes, to self-assembled particles, and microparticles when the concentration of KOH was changed from 1.5M, 2.5M, to 3.5M, and 5M. Correspondingly, the main phase of the samples changed from orthorhombic Bi2Fe4O9, both Bi2Fe4O9 and BiFeO3, to pure rhombohedral BiFeO3. On the basis of these experiments, the phase formation and morphology evolution mechanism of the samples are discussed. Furthermore, the photocatalytic activity of the as-prepared samples was investigated by the photo-degradation of rhodamine-B solution.
Keywords: A. Inorganic compounds; A. Nanostructures; B. Chemical synthesis; B. Crystal growth; D. Catalytic properties
Lead citrate precursor route to synthesize nanostructural lead oxide from spent lead acid battery paste
by Lei Li; Yuchen Hu; Xinfeng Zhu; Danni Yang; Qin Wang; Jianwen Liu; R. Vasant Kumar; Jiakuan Yang (pp. 1700-1708).
Display Omitted► A new citrate precursor Pb3(C6H5O7)2·3H2O has been synthesized in leaching process. ► The calcination products of precursors in N2 consist of β-PbO, Pb and amorphous C. ► Nanostructural lead oxide is obtained in air with the particle size of 100–200nm.Nanostructural lead oxides were prepared by the decomposition of a new type of lead citrate precursor (Pb3(C6H5O7)2·3H2O), which was synthesized through leaching of spent lead acid battery paste in citrate salt aqueous system and more economical compared with former precursor (Pb(C6H6O7)·H2O). The products were characterized by thermogravimetric–differential thermal analysis, scanning electron microscopy and X-ray diffraction. The results show that when lead citrate of columnar-shape crystals are calcined in N2 gas, orthorhombic β-PbO is the main product containing small amount of Pb and C. On combusting the citrate in air, a mixture of orthorhombic β-PbO, tetragonal α-PbO and Pb with the particle size of 100–200nm is obtained, with β-PbO as the major product. And the cyclic voltammetry measurements of lead oxides present different electrochemical redox potentials because of the different structure of lead oxide obtained from Pb3(C6H5O7)2·3H2O.
Keywords: A. Nanostructures; B. Chemical synthesis; C. Thermogravimetric analysis; C. X-ray diffraction; D. Electrochemical properties
Sol–gel derived Cr(III) and Cu(II)/ γ-Al2O3 doped solids: Effect of the dopant precursor nature on the structural, textural and morphological properties
by Abbas Khaleel; Muhammad Nawaz; Bassam Hindawi (pp. 1709-1715).
Display Omitted► γ-Al2O3 doped with Cr3+ and Cu2+ was prepared via sol–gel method. ► Metal acetylacetonate, nitrate, and chloride were compared as dopant precursor. ► Acetylacetonate precursor enhanced gel formation and modified textural properties. ► Acetylacetonate resulted in nanoparticles and enhanced resistance to sintering.Powders of xerogel γ-Al2O3 doped with various concentrations of Cr3+ and Cu2+ (M/M+Al molar fraction=0.75–10%) were prepared via a sol–gel method. Cr3+ and Cu2+ precursors (acetylacetonate, nitrate or chloride) were added to 0.12M 2-propanol solution of aluminum tri-sec-butoxide (ASB) and hydrolysis was performed using a H2O/ASB molar ratio of 4.7. The effect of the dopant precursor on structural, textural and morphological properties was studied. Employing acac precursors resulted in unique properties after calcination at 500°C including high surface areas, as high as 455m2/g, homogeneous mesopores, 3–12nm, and amorphous powders (5–10nm particles in diameter). On the other hand, the acac precursor enhanced the resistance to sintering mainly at higher metal loads (10%) and elevated temperature (800°C). Nevertheless, the solids issued from nitrate and chloride precursors exhibited lower surface areas at high metal loads, and lower resistance to sintering.
Keywords: A. Nanostructures; A. Oxides; B. Sol–gel chemistry; C. X-ray diffraction; D. Microstructure
Synthesis and characterization of highly stable dispersions of copper nanoparticles by a novel one-pot method
by Guangbin Yang; Zhanming Zhang; Shengmao Zhang; Laigui Yu; Pingyu Zhang (pp. 1716-1719).
Highly stable dispersions of copper nanoparticles with an average particle size of about 2nm were synthesized via a simple and cost-effective one-pot method with CS2 as a reactant and a solvent as well for synthesizing surface-capping agent and Cu nanoparticles.Display Omitted► Cu nanoparticle and surface capping agent were prepared by a facile one-pot method. ► CS2 was used as both reactant and solvent for synthesizing process. ► Cu nanoparticles were highly stable dispersions. ► Cu nanoparticles with a diameter of about 2nm have a narrow size distribution.Highly stable dispersions of copper nanoparticles with an average particle size of about 2nm were synthesized via a simple and cost-effective one-pot method with CS2 as a reactant and a solvent as well for synthesizing surface-capping agent and Cu nanoparticles. As-prepared copper nanoparticles were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and Fourier transform infrared spectrometry. It has been found that surface-capped copper nanoparticles with a narrow size distribution can be readily fabricated with the established method. As-obtained spherical surface-capped Cu nanoparticles can form stable dispersions which do not show any sign of sediment even after storage at ambient conditions for 6 months, showing promising potential as novel lubricant additive.
Keywords: A. Metals; A. Nanostructures; B. Chemical synthesis
Properties of B4C/Al–B4C composite with a two-layer structure
by XinYan Yue; JianJun Wang; YangShuang Li; HongQiang Ru (pp. 1720-1724).
Display Omitted► A two-layer B4C/Al-B4C preform was synthesized by hot pressing. ► B4C porous layer looked like a network of interconnected capillaries. ► A two-layer B4C/Al–B4C composite was prepared by vacuum infiltration. ► The composite showed improved fracture toughness compared to B4C material.In order to obtain a material with a promising bulletproof performance, a two-layer structure composite consisting of B4C/Al-B4C was obtained using a two-step method for both hot pressing and infiltration aluminum in vacuum. Before aluminum infiltration the B4C porous layer of the two-layer preform looked like a three-dimensional network of interconnected capillaries. For the B4C ceramics layer the microstructure showed no apparent change before and/or after aluminum infiltration. The two-layer composite showed improved fracture toughness than that of B4C material and higher comprehensive hardness than that of B4C-Al material.
Keywords: A. Ceramics; A. Layered compounds; D. Microstructure; D. Mechanical properties
Facile synthesis of snowflake-like ZnO nanostructures at low temperature and their super catalytic activity for the ozone decomposition
by ZhenZhen Xu; Yue Ben; ZhongLin Chen; Fei Qi (pp. 1725-1727).
Snowflake-like ZnO nanocomposites with active hydroxyl groups in its structure show super catalytic activity.Display Omitted► Snowflake-like ZnO nanostructures have been successfully synthesized through a facile precipitation method at near room-temperature. ► The as-prepared ZnO exhibits super catalytic performance for ozone decomposition in water. ► Possible mechanism of catalyzed ozone decomposition on the surface of the snowflake-like ZnO was discussed.Snowflake-like ZnO nanostructures, with different shapes, have been successfully synthesized on a large scale via a facile chemical precipitation method without utilizing any additive agent. The physicochemical features of the product were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), and nitrogen absorption-desorption. Results show that the obtained ZnO had a snowflake-like structure which was made of nano-platelets with uniform thickness of 20–30nm. The average pore size and Brunauer–Emmet–Teller (BET) surface area of the as-synthesized ZnO were 31.3nm and 12.74m2/g. XPS spectrum predicts the existence of active hydroxyl groups in the prepared ZnO. The snowflake-like ZnO sample exhibited super catalytic performance for ozone decomposition in water, indicating a new effective catalyst for the ozonation of organic contaminants in water treatment.
Keywords: A. Nanostructures; A. Oxides; B. Chemical synthesis; D. Catalytic properties
Hydrothermal synthesis of nitrogen-containing carbon nanodots as the high-efficient sensor for copper(II) ions
by Yunfei Sha; Jiaying Lou; Shizhe Bai; Da Wu; Baizhan Liu; Yun Ling (pp. 1728-1731).
High photoluminescent nitrogen-containing CNDs have been synthesized by one-step hydrothermal treatment of the pipe tobacco. Chemical sensing results reveal that these CNDs can sensitively and selectively detect Cu2+ ions compared with other metal ions, which offers a novel sensing platform for the detection of Cu2+ ions.Display Omitted► High fluorescent nitrogen-containing carbon nanodots. ► One-step hydrothermal synthesis. ► The pipe tobacco as the starting material. ► Influent factors of synthetic conditions to the fluorescence were explored. ► High sensitively and selectively detect Cu2+ ions compared with other metal ions.Preparing high photoluminescent carbon nanodots (CNDs) by facile and low-cost processes have received considerable research interest. In this paper, high photoluminescent nitrogen-containing CNDs have been synthesized by one-step hydrothermal treatment of the pipe tobacco. The dispersion of these CNDs shows a strong blue luminescent emission with a max peak at 450nm when it is excited at 369nm. The as-made CNDs can sensitively and selectively detect Cu2+ ions compared with Ca2+, Mn2+, Zn2+, Cd2+, Pb2+ ions, which offers a novel sensing platform for the detection of Cu2+ ions.
Keywords: Key words; A. Amorphous materials; A. Optical materials; B. Chemical synthesis; B. Luminescence
Self-supported multi-walled carbon nanotube-embedded silicon nanoparticle films for anodes of Li-ion batteries
by Kyung-Soo Park; Kyung-Mi Min; Seung-Deok Seo; Gwang-Hee Lee; Hyun-Woo Shim; Dong-Wan Kim (pp. 1732-1736).
Display Omitted► Synthesis of MWCNT-embedded Si nanoparticle films via CVD and spin coating processes. ► Electrochemical evaluation of the MWCNT-embedded Si nanoparticle films for Li-ion battery electrodes. ► Beneficial effect of MWCNT network for the superior electrochemical performances.Self-supported multi-walled carbon nanotube (MWCNT)-embedded Si nanoparticle (NP) film electrodes for Li-ion rechargeable batteries have been prepared through chemical vapor deposition using acetylene gas and a facile spin coating process using commercial Si nanopowders. The void spaces between the MWCNTs were densely filled with a considerable amount of Si NPs with diameters of ∼50nm. The MWCNT-embedded Si NP film electrodes showed improved cycling performance. These high electrochemical performances were ascribed to the roles of MWCNTs providing an efficient electron-transport path and alleviating severe volume change of Si NPs occurring during Li-alloying/de-alloying process.
Keywords: A. Nanostructures; B. Vapor deposition; D. Electrochemical properties; D. Energy storage
Layered iron orthovanadate microrods as cathode for lithium ion batteries with enhanced cycle performance
by Zhen Fang; Fan Fan; Zekun Ding; Chenyan Wang; Liuyang Long; Shenghua Hao (pp. 1737-1740).
Display Omitted► Iron orthovanadate nanorods with layered structure were fabricated. ► Layered structure lead to good electrochemical properties. ► Iron orthovanadate nanorods shows a first discharge capacity of 423mAhg−1. ► After 15 cycles, a reversible capacity of 268mAhg−1 was obtained.Iron orthovanadate microrods with layered structure have been synthesized by a simple hydrothermal method. The composition and structure of the microrods were investigated by X-ray powder diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Electrochemical measurements indicated that the microrods maintained high capacity when used as lithium ion battery cathode. As-obtained iron orthovanadate microrods electrode exhibits a stable and reversible capacity of over 250mAhg−1 at 16mAg−1 between 1.6V and 4.7V after 15 cycles. Detailed investigations reveal that the layered structure may reduce the lithium ion diffusion path and be helpful for stable capacity.
Keywords: A. Oxides; C. Electron microscopy; D. Electrochemical properties