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Applied Nanoscience (v.3, #1)
Effect of growth potential on the electrodeposition of CIS thin films by Vishakha N. Dhanwate; N. B. Chaure (pp. 1-5).
Thin films of copper indium diselenide (CIS) were prepared in aqueous bath by low-cost potentiostatic electrodeposition technique onto Fluorine doped tin oxide substrates. The deposition potential was optimized using cyclic voltammetry study in a ternary Cu–In–Se system. The films were characterized systematically with the aid of UV–Vis spectroscopy, IV measurements, X-ray diffraction, Scanning electron microscopy and Energy dispersive X-ray analysis. CIS films deposited for different growth potential shows the tetragonal structure with (112) preferential orientation. Annealing of the films at temperature 400°C not only improves the crystallinity of layers, but it also increases the grain size, which is suitable for the development of high efficiency solar cells.
Keywords: I–III–VI semiconductor; Copper indium diselenide; Electrochemical route; Three-electrode geometry
Mechanical and thermal studies of unsaturated polyester-toughened epoxy composites filled with amine-functionalized nanosilica by Y. Jaya Vinse Ruban; S. Ginil Mon; D. Vetha Roy (pp. 7-12).
The inter-crosslinking networks of unsaturated polyester (UP)-toughened epoxy-nanosilica hybrid nanocomposites have been developed. Epoxy resin was toughened with 5 and 10% (by wt) of unsaturated polyester using benzoyl peroxide as radical initiator and 4,4′-diaminodiphenylmethane (DDM) as a curing agent at appropriate condition, and the resulting product was identified by FT-IR spectra. Unsaturated polyester-toughened epoxy system (10%) was further filled with 1, 3, 5 and 7% (by wt) of amine-functionalized nanosilica particles prepared by sol–gel method. Modified nanosilica-filled hybrid UP–epoxy matrices developed in the form of casting were characterized for their thermal, mechanical properties and water absorption capacity according to ASTM standards. The degree of dispersion of nanosilica in the matrices was investigated by SEM technique. Mechanical testing data indicate that the introduction of UP into epoxy resin has improved the impact strength. Significant improvement in the flexural properties, tensile properties and impact strength were observed in the UP–epoxy blends with increase in the percentage of amine-modified nanosilica particles. The T g value decreases with UP toughening and increases with concentration of modified nanosilica on the UP–epoxy matrix. The water absorption behavior is found to decrease with UP toughening and concentration of modified nanosilica on the UP–epoxy matrix.
Keywords: Epoxy; Unsaturated polyester; Sol–gel method; Amine–nanosilica; Thermal property; Mechanical properties; Water absorption; Nanocomposites
Electrical and optical studies of pure and Ni-doped CdS quantum dots by Arfat Firdous; D. Singh; M. M. Ahmad (pp. 13-18).
Quantum dots of CdS and Ni-doped CdS were synthesized through chemical precipitation method using a high-boiling solvent. Nanocrystallinity of the as prepared nanostructure is confirmed using X-ray diffraction (XRD). The mean crystal size obtained by full-width half maxima (FWHM) analysis is 3.33 nm for CdS, 3.37 nm for CdS:Ni (2 mM) and 3.39 nm for CdS:Ni (4 mM). The electrical conductivity data reveal semiconducting behaviour of both pure CdS and Ni-doped CdS nano-crystals. The optical absorption analysis conducted in UV–vis range 200–900 nm reveals the transparency of these nanocrystals in entire visible range but not in ultraviolet range. The results based on optical analysis yield band gap values as 2.65 eV for CdS, 2.59 eV for CdS:Ni (2 mM) and 2.53 eV for CdS:Ni (4 mM) nanoparticles. This implies that pure CdS and Ni doped CdS are blue shifted with respect to the bulk CdS (2.42 eV); however, Nickel doped CdS nanocrystals are red shifted with respect to pure CdS nanocrystals.
Keywords: CdS nanocrystals; Doping; Electrical properties; Optical properties
Electrical, optical and morphological properties of chemically deposited nanostructured tungsten disulfide thin films by P. A. Chate; D. J. Sathe; P. P. Hankare (pp. 19-23).
Nanocrystalline tungsten disulfide thin films have been deposited on non-conducting glass substrates using triethanolamine bath. The film samples were characterized by X-ray diffraction, scanning electron microscopy, optical spectroscopy and thermoelectric techniques. The crystalline phase of the deposited sample was of hexagonal wurtzite-type. The optical band gap energy of the sample was found to be 1.46 eV. The electrical conductivity of the film sample was found to be in the order of 10−3 (Ω cm)−1. Thermoelectric measurement showed n-type of conductivity. The configuration of fabricated cell is n-WS2 | NaI (2 M) + I2 (1 M) | C(graphite). The efficiency of the cell was found to be 1.29%.
Keywords: Chalcogenides; Electronic material; Thin films; Nanomaterial
Intrinsic and extrinsic contributions to magnetodielectric effect in double perovskite La2CoMnO6 nanoparticles by A. Venimadhav; Devi Chandrasekar; J. Krishna Murthy (pp. 25-28).
We have studied the magnetic and magnetodielectric (MD) properties of La2CoMnO6 nanoparticles of size ~28 nm prepared by sol–gel method. Dielectric behavior showed two relaxations coinciding with the magnetic transitions at 218 and 150 K, respectively. At those relaxation maxima, a large MD effect of 11 and 8% (at 100 kHz) with 5T was observed and the magnitude of MD effect is dependent on frequency. ΔεMD ∝ M 2 relation in the paramagnetic to ferromagnetic regime suggests the spin lattice coupling; however, within the ferromagnetic region (200–100 K), we have found ΔεMD ∝ M 4 relation which may be due to the complicated spin–pair correlation interactions among next nearest neighbors. Complex impedance analysis showed large frequency dispersion of dielectric permittivity, and strong influence of both bulk and grain boundary impedances with magnetic field clearly suggests that both intrinsic spin–lattice coupling and extrinsic Maxwell–Wagner model combined with magnetoresistance effect contribute to the observed MD property.
Keywords: Magnetodielectric effect; La2CoMnO6 nanoparticles; Spin–lattice coupling; Maxwell–Wagner model
An alternative improved method for the homogeneous dispersion of CNTs in Cu matrix for the fabrication of Cu/CNTs composites by Maneet Lal; S. K. Singhal; Indu Sharma; R. B. Mathur (pp. 29-35).
Copper has a wide range of applications due to its excellent properties (high thermal and electrical conductivity). Carbon nanotubes (CNTs) are widely used as a reinforcing material due to their superior properties. Copper/Carbon nanotube (Cu/CNTs) composites show enhanced mechanical, electrical and thermal properties as compared to pure Cu and Cu composites. Hence, Cu/CNTs composites have tremendous applications. Cu/CNTs are being developed for use as antifungal and antimicrobial agents, which can lead to their further use in biomedical devices and implant materials. The versatility of this material is such that Cu/CNTs are being developed for use in ultra-large scale integrated circuits for use in the latest integrated circuits and semiconductor chips. The composite material is being used as heat sinks for various industries. Cu/CNTs are now also being employed as catalysts for various industrial reactions. Fuel cell electrodes based on Cu/CNTs are being developed to replace expensive Pt/Pd-based electrodes, currently being used. Another application in the energy sector is the use of Cu/CNTs in direct methanol fuel cells and in methanol gas reforming for H2 production. These extensive applications provided motivation for the current work. However, these applications can only be realized if a stable and uniform Cu/CNTs composite powder can be made. The challenges in fabricating Cu/CNTs composites are: (1) homogeneous dispersion of CNTs in Cu matrix, (2) interfacial bonding between CNTs and Cu matrix and (3) retention of structural integrity of CNTs. Powder metallurgy (PM) has been widely used, but dispersion of Cu/CNTs remains an issue. We employed the molecular level mixing method (MLM), coupled with high energy ball milling (BM) to overcome above mentioned issues. To the best of our knowledge, this is a new process for the homogeneous dispersion of CNTs in copper and has been reported for the first time. To produce a homogenous mixture of Cu and CNTs, a combination of MLM and BM was used in the present work. This method involves using a Cu salt/CNTs mixture in desirable weight ratio (CNTs being were taken in a high concentration), followed by chemical reduction in aqueous medium using NABH4 as reducing agent and EDTA as the oxidation control agent. The resultant mixture (Copper/Carbon nanotube) was mixed with pure Cu using BM. The composites were fabricated using PM, in which the composite powders were first cold pressed at 500–550 MPa followed by sintering at 550–900 °C in a vacuum of 10−2 Torr. Characterization was carried out using SEM, XRD and HRTEM, and various mechanical properties were measured using a Universal testing Instron machine.
Keywords: Copper/Carbon nanotube composites; Molecular level mixing; High energy ball milling
Synthesis and properties of ZnO nanorods by modified Pechini process by Ramasamy Devaraj; Krishnamoorthy Karthikeyan; Kadarkaraithangam Jeyasubramanian (pp. 37-40).
Zinc oxide (ZnO) nanorods have been successfully synthesized by modified Pechini process. The as-synthesized ZnO nanorods were characterized by X-ray diffraction, scanning electron microscope, Raman spectrum, ultraviolet–visible (UV–vis) spectrum. X-ray diffraction result shows that the ZnO nanorods are oriented in wurtzite phase. Raman spectroscopy measurements revealed the presence of E2 (high) mode at 437 cm−1 indicating the high crystallinity of the as-synthesized ZnO nanorods. The optical property of the ZnO nanorods were studied from their UV–vis spectroscopy analysis which exhibits the absorbance at 373 nm corresponds to the Zn–O absorption. A mechanism for modified Pechini process for the synthesis of ZnO nanorods using citric acid–ethylene glycol precursor has also been proposed.
Keywords: ZnO nanorods; Pechini process; Raman spectrum; Optical properties
Synthesis and characterization of carbon nanotubes over iron carbide nanoparticles coated Al powder using thermal chemical vapor deposition by S. K. Singhal; R. K. Seth; Rashmi; Satish Teotia; Mamta; Rajeev Chahal; R. B. Mathur (pp. 41-48).
A simple method is described to synthesize carbon nanotubes (CNTs) by the thermal decomposition of toluene at 750°C over a thin catalyst film deposited on Al powder. This method allows the bulk metal surface to act as both the catalyst and support for CNT growth. The catalyst film on Al was prepared from an ethanol solution of iron nitrate. Under the growth conditions, iron nitrate formed an amorphous iron oxide layer that transform into crystalline Fe2O3, which was further reduced to Fe3O4 and Fe3C. It is believed that the growth of CNTs took place on iron carbide nanoparticles that were formed from FeO. The characterization of CNTs was mainly carried out by powder X-ray diffraction and scanning electron microscopy, X-ray fluorescence and thermogravimatric analysis. The CNTs were found to be highly dispersed in Al powder. This composite powder could be further used for the fabrication of Al matrix composites using powder metallurgy process in which the powder were first cold pressed at 500–550 MPa followed by sintering at 620°C for 2 h under a vacuum of 10−2 torr. The mechanical properties of the sintered composites were measured using a microhardness tester and a Universal testing Instron machine.
Keywords: Carbon nanotubes; Thermal chemical vapor deposition; Metal-matrix composites
Synthesis of ZnO/Al:ZnO nanomaterial: structural and band gap variation in ZnO nanomaterial by Al doping by Muhammad Nafees; Wasim Liaqut; Salamat Ali; Muhammad Ahsan Shafique (pp. 49-55).
Pure ZnO and Al-doped ZnO nanomaterial have been successfully fabricated using zinc acetate dihydrate in a basic aqueous solution of KOH through solution precipitation method then treated at 600°C in air. The XRD analysis confirms the Wurtzite hexagonal crystal structure of the product with crystallite size in 32–53 nm range. The morphology of the product has been studied under scanning electron microscopy (SEM). The simultaneous differential scanning calorimetry and thermogravimetric analyses were used to investigate thermal decomposition temperature and different phase transitions up to 800°C. The optical properties and variation in band gap of ZnO by Al doping were investigated by ultraviolet–visible spectroscopy.
Keywords: ZnO; Band gap; Nanomaterial; Lattice strain; Al doping
Optimization of preparation conditions of ZnO–SiO2 xerogel by sol–gel technique for photodegradation of methylene blue dye by R. M. Mohamed; E. S. Baeissa; I. A. Mkhalid; M. A. Al-Rayyani (pp. 57-63).
The ZnO–SiO2 xerogel photocatalyst was prepared via the sol–gel technique and applied for photodegradation of methylene blue (MB) dye. The optimum conditions for preparation of ZnO–SiO2 gel is 30:70 ZnO:SiO2 molar ratio and TEOS:C2H5OH:H2O:HNO3 is 1:16:12:0.04 molar ratios at 30°C for 30 min, at these conditions the photoactivity of ZnO–SiO2 xerogel was 99% at a surface area of 500 m2/g after 60 min. The optimum loading of ZnO–SiO2 photocatalyst was 0.050 wt% that gives 99% MB dye removal efficiency after 40 min. The overall kinetics of photodegradation of MB dye using ZnO–SiO2 photocatalyst was found to be of the first order.
Keywords: Sol–gel; Nanoparticles; ZnO–SiO2 ; Photocatalysis; Methylene blue dye
Synthesis of silver nanoparticles by coastal plant Prosopis chilensis (L.) and their efficacy in controlling vibriosis in shrimp Penaeus monodon by Kathiresan Kandasamy; Nabeel M. Alikunhi; Gayathridevi Manickaswami; Asmathunisha Nabikhan; Gopalakrishnan Ayyavu (pp. 65-73).
The present work investigated the effect of leaf extract from coastal plant Prosopis chilensis on synthesis of silver nanoparticles using AgNO3 as a substrate and to find their antibacterial potential on pathogenic Vibrio species in the shrimp, Penaeus monodon. The leaf extract could be able to produce silver nanoparticles, as evident by gradual change in colour of the reaction mixture consisted of the extract and 1 mM AgNO3 to dark brown. The silver nanoparticles exhibited 2θ values corresponding to the presence of silver nanocrystal, as evident by X-ray diffraction spectrum. The peaks corresponding to flavanones and terpenoids were found to be stabilizing agents of the nanoparticles, as revealed by Fourier transform infrared spectroscopy. The size of silver nanoparticles ranged from 5 to 25 nm with an average of 11.3 ± 2.1 nm and was mostly of spherical in shape, as confirmed by transmission electron microscopy. The silver nanoparticles were found to inhibit Vibrio pathogens viz., Vibrio cholerae, V. harveyi, and V. parahaemolyticus and this antibacterial effect was better than that of leaf extract, as proved by disc diffusion assay. The nanoparticles were then tested in the shrimp Penaeus monodon challenged with the four species of Vibrio pathogens for 30 days. The shrimps fed with silver nanoparticles exhibited higher survival, associated with immunomodulation in terms of higher haemocyte counts, phenoloxidase and antibacterial activities of haemolymph of P. monodon which is on par with that of control. Thus, the present study proved the possibility of using silver nanoparticles produced by coastal Prosopis chilensis as antibacterial agent in controlling vibriosis.
Keywords: Silver nanoparticles; Shrimp aquaculture; Vibriosis; Prosopis chilensis ; Penaeus monodon
Influence of Mn substitution on crystal structure and magnetocrystalline anisotropy of nanocrystalline Co1−x Mn x Fe2−2x Mn2x O4 by Lawrence Kumar; Pawan Kumar; Manoranjan Kar (pp. 75-82).
Nanocrystalline Mn substituted cobalt ferrite Co1−x Mn x Fe2−2x Mn2x O4 (x = 0.0–0.4) has been synthesized by the standard citrate–gel method. The structural and magnetic characteristics of all samples have been studied using powder X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM) and VSM techniques. Distributions of cations between the two interstitial sites (tetrahedral and octahedral site) have been estimated qualitatively by analyzing the powder X-ray diffraction patterns by employing the Rietveld refinement technique. All samples are found to be mixed spinel with cubic structure ( $$ Fdmathop 3limits^{ - } m $$ space group). The FT-IR study shows the presence of absorption bands in the range of 390–750 cm−1, which confirm the spinel structure of the sample. The stoichiometry of Co, Fe, Mn and O ions in the sample has been obtained by using energy-dispersive spectrum with help of an FE-SEM. The magnetizations in saturation have been analyzed by employing the “law of approach” technique. The saturation magnetization, coercivity and magnetocrystalline anisotropy constant depend upon Mn ion concentration and crystallite size.
Keywords: Rietveld; Spinel; Magnetocrystalline; Law of approach; XRD
Synthesis and characterization of core–shell gold nanoparticles with poly(vinyl pyrrolidone) from a new precursor salt by M. Behera; S. Ram (pp. 83-87).
In this article, we report a facile one-step chemical synthesis of gold (Au) nanoparticles (GNPs) from a new precursor salt i.e., gold hydroxide in the presence of poly(vinyl pyrrolidone) (PVP) polymer. The non-aqueous dispersion of GNPs was comprehensively characterized by UV–Visible, FTIR, zeta potential, and transmission electron microscope (TEM). A strong surface plasmon resonance band at 529 nm in the UV–Visible spectrum confirms the formation of GNPs in the Au colloid. The FTIR spectroscopic results showed that PVP molecules get chemisorbed onto the surface of GNP via O-atom of carbonyl group. A negative zeta potential of (−)16 mV reveals accumulation of nonbonding electrons of O-atom of carbonyl group of PVP molecules on the nanosurface of GNP. TEM images demonstrate a core–shell nanostructure with an Au-crystalline core covered by a thin amorphous PVP-shell. PVP-capped GNPs could be a potential candidate for bio-sensing, catalysis, and other applications.
Keywords: Gold nanoparticles; Core–shell nanostructure; Zeta potential; Chemisorption