Check out our New Publishers' Select for Free Articles

Applied Surface Science (v.256, #9)

Interaction of bathocuproine with metals (Ca, Mg, Al, Ag, and Au) studied by density functional theory by Mahesh Datt Bhatt; Shugo Suzuki; Takeaki Sakurai; Katsuhiro Akimoto (pp. 2661-2667).

Electronic structure of the interface between a bathocuproine (BCP) molecule and metal surface was studied by density functional theory. The bond energy of BCP with metal surface increased with decreasing work function of metals, that is, Au, Ag, Al, Mg, and Ca in this order. The charge transfer also increased with decreasing metal work function. It was analyzed that the Fermi level and the lowest unoccupied molecular orbital of BCP are composed of both BCP and metal orbital component, and electron transport properties across the BCP and metal is discussed based on these analyses.

Keywords: Bathocuproine; Density functional theory; Interface states; Organic solar cell

Theoretical and experimental study on the electronic structure and optical absorption properties of P-doped TiO₂ by Ling Xu; Chao-Qun Tang; Jun Qian; Zong-Bin Huang (pp. 2668-2671).

Phosphorus-doped nanosized TiO₂ powders were prepared by a sol–gel technology. The optical absorption studies revealed that the spectral responses of phosphorus-doped (P-doped) TiO₂ powders shift to the visible light region. The optimum phosphorus (P) content in our experiments is 16.7% (mol), and the corresponding absorption edge shifts to 450nm. Furthermore, our ab initio calculations support the conclusion that the doping of phosphorus can reduce the band gap by mixing the P 3p states with O 2p states. The theoretical lattice parameters and optimum phosphorus content are in agreement with the experimental results.

Keywords: PACS; 71.55.2i; 71.15.Mb; 71.20.Nr; 78.20.2eTiO; ₂; P-doped TiO; ₂; Sol–gel technology; Ab initio calculations

A microscopy study of the effect of heat treatment on the structure and properties of anodised TiO₂ nanotubes by A. Jaroenworaluck; D. Regonini; C.R. Bowen; R. Stevens (pp. 2672-2679).

Titanium oxide (TiO₂) nanotubes prepared by anodisation of titanium in an aqueous electrolyte and glycerol have been heat treated in the temperature range 200–600°C to control the conversion of the amorphous structure to nano-crystalline anatase and rutile. The phase changes have been monitored are observed at lower temperatures (100°C or more) than previously reported. The sensitivity of the different techniques, each of which depends on the size of the crystalline phase, can explain the discrepancy with previous results. Transmission electron microscopy (TEM) has shown the phase changes which have occurred and which have been reported in an earlier publication; phenomena such as the collapse of the structures are explained. The TEM results are consistent with the Raman and XRD data, apart from the transformation temperatures, and also shed light on the nature of an amorphous phase found on the surfaces of the nanotubes.

Keywords: Titanium oxide; Nanotubes; Heat treatment; Phase change; Electron microscopy

Room temperature soft chemical route for nanofibrous wurtzite ZnO thin film synthesis by K.V. Gurav; V.J. Fulari; U.M. Patil; C.D. Lokhande; Oh-Shim Joo (pp. 2680-2685).

Room temperature soft chemical deposition route has been utilized to grow thin films of ZnO on glass substrate. Annealing at 673K removed zinc hydroxide phase and nanofibrous ZnO films with wurtzite crystal structure were obtained. Decrease in the room temperature electrical resistivity from 10⁷ to 10⁴Ωcm was observed after annealing. The nanofibrous ZnO thin films were sensitive to the explosive liquefied petroleum gas (LPG) and the maximum response of 17% at 698K under the exposure of 6500ppm of LPG was obtained.

Keywords: Zinc oxide; Thin films; Soft chemical synthesis; Air annealing; LPG sensor

Study on the adsorption of fluorescein on Ag(110) substrate by H.Q. Qian; H.Y. Mao; F. Song; S.Q. Shi; H.J. Zhang; H.Y. Li; P.M. He; S.N. Bao (pp. 2686-2690).

The adsorption of fluorescein on the Ag(110) surface has been investigated by the first-principles pseudopotential method. Various adsorption geometries have been calculated and the energetically most favorable structure of fluorescein/Ag(110) was identified. The fluorescein molecule, in most favorable structure, is on hollow site, and the adsorption energy is 2.34eV. Here the adsorption sites refer to the positions at the first layer of the substrate where the middle carbon atom of the fluorescein molecule is located. The bonding strength of the fluorescein molecule to the Ag substrate is site selective, being determined by electron transfer to the oxygen atoms of the molecule and local electrostatic attraction between the oxygen atoms and the silver atoms.

Keywords: PACS; 71.15.Mb; 68.43.−h; 73.20.AtOrganic semiconductor; First-principles calculations; Adsorption energy

Generation and removal of pits during chemical mechanical polishing process for MgO single crystal substrate by K. Wang; Y.Z. Li; R.K. Kang; D.M. Guo (pp. 2691-2699).

Magnesium oxide (MgO) single crystal is an important substrate for high temperature superconductor, ferroelectric and photoelectric applications. The function and reliability of these devices are directly affected by the quality of polished MgO surface because any defect on the substrate, such as pit or scratch, may be propagated onto device level. In this paper, chemical mechanical polishing (CMP) experiments were conducted on MgO (100) substrate using slurry mainly comprised of 1-hydroxy ethylidene-11-diphosphonic acid (HEDP) and silica or ceria particles. Through monitoring the variations of the pits topography on substrate surface, generation and removal mechanism of the pits were investigated. The experimental results indicate that the pits were first generated by an indentation or scratch caused by particles in the slurry. If the rate of chemical etching in the defect area is higher than the material removal rate, the pits will grow. If chemical reaction in the defect area is slower than the material removal rate, the pits will become smaller and eventually disappear. Consequently, these findings may provide insight into strategies for minimizing pits during CMP process.

Keywords: MgO single crystal substrate; Chemical mechanical polishing; Chemical etching; Pit

Biomimetic Ca–P coating on pre-calcified Ti plates by electrodeposition method by Xiudong Yang; Bo Zhang; Jian Lu; Jiyong Chen; Xingdong Zhang; Zhongwei Gu (pp. 2700-2704).

A new electrodeposition method was presented for Ca–P coating on pre-calcified titanium (PTi) plates at room temperature. The biomimetic coating morphology was investigated by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) results indicated that the functional TiO_x layer with groups of –Ca and –OH was formed on PTi surface after pre-calcified chemical treatment. The TiO_x layer showed a lower water contact angle and lower surface energy than those of pure titanium surfaces, and the PTi surface natures are benefited by coupling biomimetic Ca–P layer with bioactivity in the electrodeposition process. Moreover, the crystallization of Ca–P precipitate and the bond strength of coating to PTi substrates were improved significantly by post-treatments. Our results suggest this new coating process and its subsequent application to biomedical implant devices.

Keywords: Biomimetic coating; Titanium; Electrodeposition; Bioactive

Interlayer effect on the characterization of the La–Cr–O coatings with post-sputtering annealing treatment by Wei-Yu Ho; Cheng-Hsun Hsu; Ming-Hua Tsai; Yu-Sen Yang; Da-Yung Wang (pp. 2705-2710).

In this study, the deposition of La–Cr–O coatings on AISI 316 stainless steel was conducted by using a DC magnetron sputtering process. Three types of La–Cr–O coatings were designed, one type without interlayer, and another two types with an interlayer of Cr and CrN film, separately. This study aims to explore the interlayer effect on the properties of La–Cr–O coatings after post-annealing treatment. The coatings were characterized using the X-ray diffractionmeter (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA)/differential scanning calorimetry (DSC).The results showed that the three as-deposited La–Cr–O coatings had an amorphous structure. After annealing at 800°C for 1h in the air, the structure was transformed to the LaCrO₃ perovskite phase. Compared with the coatings without an interlayer, the double-layered coatings did not show the Cr₂O₃ phase in the structure. It implies that the use of the interlayer in the coatings could efficiently prohibit the diffusion of Cr to form oxide on the out-layer. Based on the TGA/DSC analysis and the electrical resistance measurement, it is understood that the annealed La–Cr–O coating with the CrN interlayer turns in the best performance in both chemical stability at high temperature and electrical resistance.

Keywords: Magnetron sputtering; LaCrO; ₃; CrN; Annealing

The influence of γ-irradiation on some physical properties of chlorophyll/PMMA films by E.M. Abdelrazek; G. El Damrawi; I.S. Elashmawi; A. El-Shahawy (pp. 2711-2718).

Films of poly(methylmethacrylate) PMMA doped with different concentrations of chlorophyll, from 2.5 up to 12.5wt.%, have been prepared by casting method. Studies were carried out utilizing FT-IR, UV/vis, fluorescence, TGA and DC electrical conduction to characterize the structural, optical and thermal properties of the films before and after irradiation. Results revealed that the structural and chemical characterizations of PMMA films are affected by the addition of chlorophyll and increasing dose of γ-irradiation. FT-IR analysis revealed that the hydroxyl and carbonyl groups were responsible for the decrease of the bands intensities with increasing the dose rate up to 100kGy. The change in these groups was attributed to competitive processes: decomposition with ester group abstraction and oxidation with formation of new oxidized carbonyls in the polymeric chains. The values of optical energy gap for the samples were decreased upon irradiation; this indicates that there is a charge transfer complexes arise between PMMA and chlorophyll. TGA analysis shows that the addition of chlorophyll to PMMA films enhances their thermal stability. The electric conduction data were interpreted on the basis of an intrachain one-dimensional interpolaron hopping model of Kuivalainen.

Keywords: PMMA; Chlorophyll; γ-Irradiation; FT-IR; UV/vis; TGA

Raman microprobe spectroscopy measurements of residual stress distribution along blisters in Cr₂O₃ thin films by M. Kemdehoundja; J.L. Grosseau-Poussard; J.F. Dinhut (pp. 2719-2725).

Raman spectroscopy has been used to characterise the buckling phenomenon of Cr₂O₃ films obtained by oxidation in air at 900°C of Ni33at%Cr. The observed circular blisters are described by measuring the radius from the optical top view, the profile via an autofocus device and the residual stress in each point of the chromia film: far away from the centre of the blister, in the vicinity and across the blister. The subsequent spalls are related to the morphology of the blisters and to the stress.

Keywords: Oxidation; Blisters; Residual stress; Raman spectroscopy; NiCr

Deposition and properties of B–N codoped p-type ZnO thin films by RF magnetron sputtering by Y.R. Sui; B. Yao; J.H. Yang; H.F. Cui; X.M. Huang; T. Yang; L.L. Gao; R. Deng; D.Z. Shen (pp. 2726-2730).

B–N codoped p-type ZnO thin films have been realized by radio frequency (rf) magnetron sputtering using a mixture of argon and oxygen as sputtering gas. Types of conduction and electrical properties in codoped ZnO films were found to be dependent on oxygen partial pressure ratios in the sputtering gas mixture. When oxygen partial pressure ratio was 70%, the codoped ZnO film showed p-type conduction and had the best electrical properties. Additionally, the p-ZnO/ n-Si heterojunction showed a clear p– n diode characteristic. XRD results indicate that the B–N codoped ZnO film prepared in 70% oxygen partial pressure ratio has high crystal quality with (002) preferential orientation. Meanwhile, the B–N codoped ZnO film has high optical quality and displays the stronger near band edge (NBE) emission in the temperature-dependent photoluminescence spectrum, the acceptor energy level was estimated to be located at 125meV above the valence band.

Keywords: Zinc oxide; B–N codoping; p; -Type conduction; Sputtering; Properties

Inter-diffusion of cobalt and silicon through an ultra thin aluminum oxide layer by T. El Asri; M. Raissi; S. Vizzini; A. El Maachi; E.L. Ameziane; F. Arnaud d’Avitaya; J.-L. Lazzari; C. Coudreau; H. Oughaddou; B. Aufray; A. Kaddouri (pp. 2731-2734).

Optical emission spectroscopy of sputtered species during ion bombardment, Auger electron spectroscopy and high-resolution transmission electron microscopy were used to study the cobalt and silicon diffusion through the interfaces of Co/AlO/Si(001) hetero-structure. The results are discussed as a function of the annealing temperature of sample and show that the diffusion process at the interfaces starts for annealing temperatures above 200°C without detectable modification of the oxide layer.

Keywords: Diffusion; Cobalt; Silicon; Aluminum oxide layer; MIS structure; AES; SIPS; HR-TEM

Investigations of the interactions of CO₂, O₃ and UV light with silver surfaces by in situ IRRAS/QCM and ex situ TOF-SIMS by R. Wiesinger; M. Schreiner; Ch. Kleber (pp. 2735-2741).

The characterization of the reactions occurring during the atmospheric corrosion of silver surfaces at the metal–atmosphere interface is of great importance as only the exact knowledge of the degradation mechanisms enables the development of suitable corrosion inhibiting steps. For in situ surface analysis three complementary experimental techniques have been combined in order to study the surface chemistry of silver samples exposed to humidified air, CO₂, ozone (O₃) and ultraviolet (UV) light. In situ infrared reflection absorption spectroscopy (IRRAS) combined with a quartz crystal microbalance (QCM) as well as ex situ time of flight secondary ion mass spectrometry (TOF-SIMS) provide an overall picture of the processes occurring at the metal–atmosphere interface. Investigations were carried out by exposing polycrystalline silver samples to synthetic air containing 50–90% relative humidity (RH) and 250ppm CO₂. Additionally, the samples were exposed to UV light or O₃ for certain time periods. The formation of the main corrosion products on the sample surfaces, depending on the relative humidity, O₃ content and UV light exposure could be observed in a time resolved way. These investigations reveal the different reaction mechanisms and reaction rates occurring on a silver surface.

Keywords: Silver; Atmospheric corrosion; In situ; IRRAS; QCM; Ozone; UV light

Thermal stability of thiol and silane monolayers: A comparative study by Amol Chandekar; Sandip K. Sengupta; James E. Whitten (pp. 2742-2749).

The stability of self-assembled monolayers (SAMs) at elevated temperatures is of considerable technological importance. The thermal stability of 1-octadecanethiol (ODT), 16-mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) SAMs on gold surfaces, and of 4-aminobutyltriethoxysilane (ABTES) and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) assembled on hydroxylated silicon surfaces, was studied by X-ray photoelectron spectroscopy (XPS). The samples were heated in ultrahigh vacuum to temperatures in excess of that required for SAM degradation. ODT monolayers were stable to ca. 110°C, while MHDA and PFDT SAMs were stable to ca. 145°C. ABTES SAMs were found to be indefinitely stable to 250°C, while PFDS SAMs were stable to 350°C. These studies demonstrate the advantages of using silane monolayers for moderate to high temperature applications and illustrate differences that arise due to the nature of the tail group. To demonstrate the feasibility of silanes for template-directed patterning, a hydroxylated silicon oxide surface containing microcontact-printed PFDS patterns was spin-coated with a mainly hydrophilic block copolymer. Annealing the surface at 90°C for 2h caused the block copolymer to dewet the hydrophobic PFDS-patterned regions and adsorb exclusively on the unpatterned regions of the surface.

Keywords: Thermal stability; Monolayer; Thiol; Silane; XPS; Microcontact printing

A novel sputtering oxidation coupling (SOC) method to fabricate VO₂ thin film by Xiaofeng Xu; Anyuan Yin; Xiliang Du; Jiqing Wang; Jiading Liu; Xinfeng He; Xingxing Liu; Yilong Huan (pp. 2750-2753).

VO₂ thin film synthesized by a novel sputtering oxidation coupling (SOC) method has been successfully fabricated. The experimental results show that the optimum oxidation time is 285s and the thin film exhibits a good metal-insulator transition (MIT) approximately at 340K. The corresponding structures and surface compositions of the films have been characterized by X-ray diffractometer and X-ray photoelectron spectroscopy separately.

Keywords: VO; ₂; thin films; Sputtering oxidation coupling; Metal-insulator transition

A one-pot method to prepare N-doped titania hollow spheres with high photocatalytic activity under visible light by Yanhui Ao; Jingjing Xu; Songhe Zhang; Degang Fu (pp. 2754-2758).

N-doped titania hollow spheres (NTHS) were prepared by a one-pot hydrothermal method using urea as precursor of nitrogen. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectrum (DRS). The photocatalytic activity of as-prepared titania hollow spheres was determined by degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2) under visible light irradiation, and was compared to non-doped titania hollow spheres and commercial P25 titania. Results indicated that the as-prepared NTHS showed highest photocatalytic activity.

Keywords: Photocatalysis; Titania; Hollow spheres; N-doped; Visible light

Surface-coated fly ash used as filler in biodegradable poly(vinyl alcohol) composite films: Part 1—The modification process by D.C.D. Nath; S. Bandyopadhyay; S. Gupta; A. Yu; D. Blackburn; C. White (pp. 2759-2763).

The surfaces of fly ash (FA) particles were modified by surfactant, sodium lauryl sulphate (SLS) and used in fabrication of composite films with polyvinyl alcohol (PVA). Both unmodified fly ash (FA) and modified fly ash (SLS–FA) samples were examined using a range of analytical tools including X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The distribution patterns of SLS–FA particles were shifted to the higher regions compared to FA by adding 1.2–4.2μm in the ranges between 2 and 25μm, whereas the modification process reduced the size of the particles over 25μm due to grinding during the activation process. The increased 1.2–4.2μm in average can be considered the thickness of the surfactant on the SLS–FA surface. On the oxides based chemical analysis by XRF, the compositions were almost unchanged. SEM and TEM were visualised the irregular sizes morphology mostly spherical of the particles, although it is impossible to capture the images of exactly same particles in modified and unmodified forms. The composite films reinforced with SLS–FA showed 33% higher strength than those of FA filled films. The enhancement of tensile strength attributed from the level of physical bonding between SLS–FA and PVA surfaces.

Keywords: Fly ash; Polyvinyl alcohol (PVA); Composite film; Surfactant; Interface

Enhanced field emission and patterned emitter device fabrication of metal-tetracyanoquinodimethane nanowires array by Kaibo Zheng; Xianyi Li; Xiaoliang Mo; Guanyu Chen; Zhengdong Wang; Guorong Chen (pp. 2764-2768).

Ag(TCNQ) and Cu(TCNQ) nanowires were synthesized via vapor-transport reaction method at a low temperature of 100°C. Field emission properties of the as-obtained nanowires on ITO glass substrates were studied. The turn-on electric fields of Ag(TCNQ) and Cu(TCNQ) nanowires were 9.7 and 7.6V/μm (with emission current of 10μA/cm²), respectively. The turn-on electric fields of Ag(TCNQ) and Cu(TCNQ) nanowires decreased to 6 and 2.2V/μm, and the emission current densities increased by two orders at a field of 8V/μm with a homogeneous-like metal (e.g. Cu for Cu(TCNQ)) buffer layer to the substrate. The improved field emission is due to the better conduct in the nanowires/substrate interface and higher internal conductance of the nanowires. The patterned field emission cathode was then fabricated by localized growing M-TCNQ nanowires onto mask-deposited metal film buffer layer. The emission luminance was measured to be 810cd/m² at a field of 8.5V/μm.

Keywords: PACS; 85.35.−pM-TCNQ; Nanowires; Field emission

A novel continuous process for synthesis of carbon nanotubes using iron floating catalyst and MgO particles for CVD of methane in a fluidized bed reactor by Sarah Maghsoodi; Abasali Khodadadi; Yadollah Mortazavi (pp. 2769-2774).

A novel continuous process is used for production of carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CVD) of methane on iron floating catalyst in situ deposited on MgO in a fluidized bed reactor. In the hot zone of the reactor, sublimed ferrocene vapors were contacted with MgO powder fluidized by methane feed to produce Fe/MgO catalyst in situ. An annular tube was used to enhance the ferrocene and MgO contacting efficiency. Multi-wall as well as single-wall CNTs was grown on the Fe/MgO catalyst while falling down the reactor. The CNTs were continuously collected at the bottom of the reactor, only when MgO powder was used. The annular tube enhanced the contacting efficiency and improved both the quality and quantity of CNTs.The SEM and TEM micrographs of the products reveal that the CNTs are mostly entangled bundles with diameters of about 10–20nm. Raman spectra show that the CNTs have low amount of amorphous/defected carbon with I_G/ I_D ratios as high as 10.2 for synthesis at 900°C. The RBM Raman peaks indicate formation of single-walled carbon nanotubes (SWNTs) of 1.0–1.2nm diameter.

Keywords: Continuous process; Carbon nanotubes; Ferrocene; Chemical vapor deposition; Fluidized bed; Floating catalyst

Applied validity of effortless method for design of sinusoidal surface microstructure by Xufeng Jing; Jianpeng Wang; Yunxia Jin; Hongbo He; Jianda Shao; Zhengxiu Fan (pp. 2775-2780).

With the purpose of easily analyzing and designing the transmittance performance of a sinusoidal surface microstructure, the validity of effortless methods including scalar diffraction theory and effective medium theory has been evaluated quantitatively by the comparison of diffraction efficiencies predicted from scalar theory and effective indices theory, respectively, with exact results calculated with the rigorous vector method of Fourier modal method. Generally speaking, when the normalized period of surface microstructure is less than ten wavelengths of the incident light the scalar diffraction theory is believed to be inaccurate for designing and analyzing the diffraction efficiency of surface microstructure. But, in this paper, it is found that scalar diffraction theory can be used for predicting transmittance of the optical elements when the normalized period is more than three wavelengths of incident light within the error less than 5% at normal incidence. In addition, it is generally recognized that the effective medium theory is inaccurate for analyzing periodic surface microstructure when the normalized period is more than a tenth of the wavelength of incident light. However, the results in this study shows that effective medium theory is accurate as only zero-order waves are to propagate through the surface profiles, which the maximum difference between zero-order effective indices method and rigorous vector method reaches to 1%. Besides, the limitation of both simplified theories is dependent on not only the normalized period of a surface microstructure but also the normalized groove depth. Therefore, the range of applied validity of scalar theory and effective medium theory is expanded quantitatively compared to that of previous inaccuracy application for more easily designing and analyzing a sinusoidal surface microstructure.

Keywords: PACS; 78.67.−n; 78.68.+m; 78.66.−wSinusoidal surface microstructure; Effective medium theory; Scalar diffraction theory; Transmittance performance

ZnO nanorods/plates on Si substrate grown by low-temperature hydrothermal reaction by S.Y. Gao; H.D. Li; J.J. Yuan; Y.A. Li; X.X. Yang; J.W. Liu (pp. 2781-2785).

The zinc oxide (ZnO) nanorods/plates are obtained via hydrothermal method assisted by etched porous Al film on Si substrate. The products consist of nanorods with average diameter of 100nm and nanoplates with thickness of 200–300nm, which are uniformly distributed widely and grown perpendicularly to the substrate. The ZnO nanoplates with thickness of 150–300nm were grown on Si substrate coated with a thin continuous Al film (without etching) in the same aqueous solution. The growth mechanism and room temperature photoluminescence (PL) properties of ZnO nanorods/plates and nanoplates were investigated. It is found that the introduction of the etched Al film plays a key role in the formation of ZnO nanorods/plates. The annealing process is favorable to enhance the UV PL emissions of the ZnO nanorods/plates.

Keywords: Zinc oxide; Nanorods/plates; Hydrothermal reaction; Photoluminescence

Influence of postdeposition annealing on structural properties and electrical characteristics of thin Tm₂O₃ and Tm₂Ti₂O₇ dielectrics by Tung-Ming Pan; Li-Chen Yen (pp. 2786-2791).

We describe the structural properties and electrical characteristics of thin thulium oxide (Tm₂O₃) and thulium titanium oxide (Tm₂Ti₂O₇) as gate dielectrics deposited on silicon substrates through reactive sputtering. The structural and morphological features of these films were explored by X-ray diffraction, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, and atomic force microscopy, measurements. It is found that the Tm₂Ti₂O₇ film annealed at 800°C exhibited a thinner capacitance equivalent thickness of 19.8Å, a lower interface trap density of 8.37×10¹¹eV⁻¹cm⁻², and a smaller hysteresis voltage of ∼4mV than the other conditions. We attribute this behavior to the Ti incorporated into the Tm₂O₃ film improving the interfacial layer and the surface roughness. This film also shows negligible degrees of charge trapping at high electric field stress.

Keywords: Tm; ₂; O; ₃; Tm; ₂; Ti; ₂; O; ₇; Gate dielectric; Interfacial SiO; ₂; Silicate

Surface characterization of polyethylene terephthalate/silica nanocomposites by Mazeyar Parvinzadeh; Siamak Moradian; Abosaeed Rashidi; Mohamad-Esmail Yazdanshenas (pp. 2792-2802).

Poly(ethylene terephthalate) (PET) based nanocomposites containing hydrophilic (i.e. Aerosil 200 or Aerosil TT 600) or hydrophobic (i.e. Aerosil R 972) nano-silica were prepared by melt compounding. Influence of nano-silica type on surface properties of the resultant nanocomposites was investigated by the use of Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), contact angle measurement (CAM), scanning electron microscopy (SEM) and reflectance spectroscopy (RS). The possible interaction between nano-silica particles and PET functional groups at bulk and surface were elucidated by transmission FTIR and FTIR-ATR spectroscopy, respectively. AFM studies of the resultant nanocomposites showed increased surface roughness compared to pure PET. Contact angle measurements of the resultant PET composites demonstrated that the wettability of such composites depends on surface treatment of the particular nano-silica particles used. SEM images illustrated that hydrophilic nano-silica particles tended to migrate to the surface of the PET matrix.

Keywords: PET; Nano-silica; Hydrophilic; Hydrophobic

Application of clean laser transfer for porphyrin micropatterning by T.V. Kononenko; I.A. Nagovitsyn; G.K. Chudinova; I.N. Mihailescu (pp. 2803-2808).

Blister-based laser-induced forward transfer is proposed as a promising tool for clean, cold and liquid-free local transfer of various organic substances. The feature of the given technique is non-destructive local deformation of an absorbing metal film on a transparent support avoiding the metal sputtering. Application of the blister-based laser transfer of a Langmuir film to fabricate mesotetraphenylporphyrin micropatterns on a silica substrate has been demonstrated. The metal film thickness is found to be a key parameter, which determines the laser fluence range allowing the clean transfer, predominant mechanism of the blister formation and laser-induced heating of the transferred material. According to the numerical modelling confirmed by UV–vis absorption spectroscopy, the target with 1.5μm thick titanium film provides negligible heating of the porphyrin transferred by 5ns laser pulses.

Keywords: Laser-induced forward transfer; Langmuir film; Porphyrin

Optical properties and electric conductivity of gold nanoparticle-containing, hydrogel-based thin layer composite films obtained by photopolymerization by László Janovák; Imre Dékány (pp. 2809-2817).

Poly(acrylamide) [poly(AAm)] and poly( N-isopropyl-acrylamide) [poly(NIPAAm)] based gel films containing Au nanoparticles ( d=14±2.5nm) were synthesized. Monomers and cross-linker were added to a gold nanodispersion, and after the addition of the initiator, polymer films were prepared on the surface of an interdigital microelectrode by photopolymerization. In the course of the syntheses the gold concentration of the films was constant (10.8μg/cm²) and the volume fraction of Au nanoparticles ( ϕ_Au) in the polymer gel films varied in the range of 0.58–85.3%. Poly(AAm)-based films swell when the temperature increases: due to a temperature shift of 15°C the Au plasmon absorption maximum at λ=∼532nm was shifted towards shorter wavelengths by 16.6nm (blue shift) through the swelling of the polymer gel film. In the case of poly(NIPAAm) the temperature-induced shrinking resulted in a red shift, namely the maximum was shifted by 18.07nm by a temperature shift of 15°C. In the case of both composites, the electric conductivity of the samples was shown to increase with increasing Au particle concentration. In the case of the poly(AAm)-based composite containing ϕ_Au=0.85 gold the resistance of the film spread on the surface of the electrode was 0.16MΩ at 25°C and 0.66MΩ at 50°C, i.e. the conductivity of the sample decreased with increasing temperature. The opposite effect is observed in the case of the poly(NIPAAm)-based composite: as temperature is raised, the resistance of the composite abruptly drops at the point of collapse of the NIPAAm gel (it is 0.28MΩ at 32°C and only 0.021MΩ at 35°C). This thermosensitive effect was detectable only at sufficiently high Au contents ( ϕ_Au=0.85) in both gels.

Keywords: Gold nanoparticle; Nanocomposite hydrogels; Electric conductivity; UV/VIS-spectroscopy

Ordered luminescent nanohybrid thin films of Eu(BA)₃Phen nanoparticle in polystyrene matrix from diblock copolymer self-assembly by Chao Wang; Yaoming Zhang; Xianqiang Pei; Tingmei Wang; Qihua Wang (pp. 2818-2825).

A simple route for fabricating highly ordered luminescent thin films based on hybrid material of diblock copolymer and europium complex, assisted with self-organization of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer upon solvent annealing, is presented. PS-b-PEO self-organized into hexagonal patterns and europium complex of Eu(BA)₃Phen was selectively embedded in PS blocks after solvent annealing in benzene or benzene/water vapor. During benzene annealing, the orientation of the PEO cylindrical domains strongly depended on the Eu(BA)₃Phen concentration. In contrast, when the hybrid thin films were annealed in mixture of benzene and water vapor, high degree of orientation of the PEO cylindrical domains is more easily obtained, which is independent of Eu(BA)₃Phen concentration. Furthermore, preferential interaction of PEO domains with water induces a generation of nanopores in the hybrid thin film. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the long-range lateral order and phase composition of the hybrid thin films. The ordered nanohybrid thin films kept the fluorescence property of Eu(BA)₃Phen and showed a strong red emission under the 254nm light's irradiation. The fluorescence property was confirmed by photoluminescence (PL) spectra.

Keywords: Block copolymer; Europium complex; Luminescence; Nanohybrid thin film; Self-assembly

Solvothermal synthesis and characterization of sandwich-like graphene/ZnO nanocomposites by Jili Wu; Xiaoping Shen; Lei Jiang; Kun Wang; Kangmin Chen (pp. 2826-2830).

Graphene-based nanocomposites are emerging as a new class of materials that hold promise for many applications. In this paper, we present a general approach for the preparation of sandwich-like graphene/ZnO nanocomposites in ethylene glycol (EG) medium using graphene oxide as a precursor of graphene and zinc acetylacetonate as a single-source precursor of zinc oxide. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, ultraviolet–visible (UV–vis) spectroscopy and thermogravimetry analysis. It was shown that the as-formed ZnO nanoparticles with a diameter of about 5nm were densely and uniformly deposited on both surfaces of the graphene sheets to form a sandwich-like composite structure and as a result, the restacking of the as-reduced graphene sheets was effectively prevented. The ZnO-coated graphene nanocomposites can be expected to effectively improve the photocatalysis and sensing properties of ZnO and would be promising for practical applications in future nanotechnology.

Keywords: Graphene; Zinc oxide; Synthesis; Nanocomposite

Structure, magnetic and electrical transport properties of cosputtered Fe_0.5Ge_0.5 nanocomposite films by W.B. Mi; P. Li; E.Y. Jiang; H.L. Bai (pp. 2831-2836).

Fe_0.5Ge_0.5 nanocomposite films with different film thicknesses were fabricated using cosputtering. The films are composed of Ge, Fe and Fe₃Ge₂, and are ferromagnetic at room temperature. The saturation magnetization and magnetic interaction including dipolar interaction and exchange coupling increase with the increasing film thickness. The electrical conductance mechanism turns from metallic to semiconducting and the saturation Hall resistivity ρ_xys increases with the decreasing film thickness. At 28nm, ρ_xys is ∼137μΩcm at 2K, about 150 times larger than that of pure Fe film (0.9μΩcm) and four orders larger than that of bulk Fe. The ρ_xy– H curves of all the films show the same linearity character in low-field range even though the temperature-independent slope is different at different film thicknesses. At high temperatures, the skew scattering mechanism is dominant. At low temperatures, side-jump effect should be dominant at large resistivity ρ_xx regime for the thin films, and the skew scattering is dominant at small ρ_xx regime for the thick films.

Keywords: PACS; 72.80.Tm; 73.63.−b; 68.55.−a; 73.40.−cNanocomposite; Electrical properties; Thin films; Sputtering

Catalyst-free synthesis of novel brush-shaped ZnO particles by a simple oxidation in air by Geun-Hyoung Lee; Jeong-Hwan Song (pp. 2837-2840).

Brush-shaped ZnO particles were synthesized by controlling the growth time in the direct melt oxidation process of Al–Zn mixture in air at atmospheric pressure. Particles with two kinds of structures were formed. One was consisted of nanowires grown along [0001] direction at the six corners and the center of (0001) basal plane on hexagonal ZnO microrod. The other was constructed by nanobelts between the corner-nanowires as well as nanowires at the corners on ZnO microrod. The structural configuration that the nanowires and the nanobelts have a well coherent orientation alignment with the base microrod implies that the brush-shaped ZnO is single crystal. Room temperature PL spectrum of the brush-shaped ZnO particles displayed predominant green emission with a wavelength of 510nm.

Keywords: PACS; 81.07.−b; 61.46.Km; 78.67.BfZnO particles; Brush shape; Direct melt oxidation; Vapor–solid growth

Adhesion of silver nanoparticles on the clay substrates; modeling and experiment by Jonáš Tokarský; Pavla Čapková; David Rafaja; Volker Klemm; Marta Valášková; Jana Kukutschová; Vladimír Tomášek (pp. 2841-2848).

Adhesion of silver nanoparticles on the montmorillonite and kaolinite substrates has been investigated using molecular modeling (force field calculations) that enabled the estimation and comparison of adhesion energies for Ag/montmorillonite and Ag/kaolinite nanocomposites and revealed the preferred orientation of Ag nanoparticles on the silicate substrates. Results of the modeling have been confronted with experiment (X-ray fluorescence, high-resolution transmission electron microscopy). This confrontation has shown that the results of the modeling are consistent with the experimental data and illustrated the capability of the molecular modeling for prediction of the nanoparticles orientation, structure and stability of the nanoparticle/substrate nanocomposite.

Keywords: Molecular modeling; Nanoparticles adhesion; Nanocomposite; Montmorillonite; Kaolinite; Silver

Influence of annealing conditions on the properties of reinforced silver-embedded silica matrix from the cheap silica source by Askwar Hilonga; Jong-Kil Kim; Pradip B. Sarawade; Hee Taik Kim (pp. 2849-2855).

The influence of annealing conditions on the properties of reinforced silver-embedded silica matrix was systematically investigated in the present study. The samples were prepared via a recently reported method using sodium silicate as a silica precursor. Aluminium ions were used to reinforce and improve the chemical durability of silver-embedded silica; and the mole ratio of the precursors was fixed at Al/Ag=1. The properties of the final product were examined in relation to its counterparts; namely pure silica, aluminium-embedded silica (without silver), and silver doped silica (without aluminium). The materials were heat treated at the range of 600–1000°C under the constant supply of argon (inert atmosphere). The properties of the final product were compared with those of the previously reported materials prepared via the same method but calcined in air. The current material was found to have pure silver nanoparticles (without AgCl nanoparticles) while the previous material had both silver and AgCl nanoparticles. The results demonstrate that materials with more desirable properties can be obtained by this newly developed technique while utilizing sodium silicate, which is relatively cheap, as a silica precursor. This may significantly boost the industrial production of the silver-embedded silicas for various applications.

Keywords: Silver nanoparticles; Silver-embedded; Silica matrix; Sodium silicate; Aluminium; BET

The fabrication of Ag nanoflake arrays via self-assembly on the surface of an anodic aluminum oxide template by Xueming Li; Kun Dong; Libin Tang; Yongjun Wu; Peizhi Yang; Pengxiang Zhang (pp. 2856-2858).

Vertical-aligned Ag nanoflake arrays are fabricated on the surface of an anodic aluminum oxide (AAO) template under a hydrothermal condition for the first time. The porous surface of AAO templates and the precursor solution may play key roles in the process of fabricating Ag nanoflakes. The rim of pores can provide many active sites for nucleation and growth, and then nanoflake arrays gradually form through self-assembly of Ag on the surface of AAO membranes. The product is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a growth mechanism of nanoflake is deduced. This work demonstrates that it is possible to make ordered nanoarrays without dissolving templates using the hydrothermal method, and this interesting Ag nanoflake arrays may provide a wider range of nanoscale applications.

Keywords: Crystal growth; Self-assembly; Nanomaterials; AAO template

Preparation, characterization and photocatalytic performance of TiO₂/Ce_xZr1−_xO₂ toward the oxidation of gaseous benzene by Jun bo Zhong; Di Ma; Xi yang He; Jian zhang Li; Yao qiang Chen (pp. 2859-2862).

Increasing environmental pollution caused by the volatile organic compounds due to their toxicity makes their removal imperative. So it is crucial to develop processes which can degrade these compounds effectively. The paper demonstrates that the photocatalytic activity of TiO₂ toward the decomposition of gaseous benzene in a batch reactor can be greatly enhanced by loading TiO₂ onto the surface of Ce_xZr1−_xO₂ ( x≥0.25) using sol–gel technology. This research investigated the relationship between x amount and the photocatalytic activity of TiO₂. The prepared photocatalysts were characterized by BET, XRD, UV–vis diffuse reflectance and XPS analyses. The specific surface area of photocatalyst decreases as x decreases. XRD results reveal the no peaks of titania were detected. Among the five catalysts prepared, only the binding energy values of Ti2p_3/2 of TiO₂/Ce_0.5Zr_0.5O₂ shift toward lower value. The order of photocatalytic activity is TiO₂/Ce_0.5Zr_0.5O₂>TiO₂/Ce_0.75Zr_0.25O₂>TiO₂/CeO₂≈TiO₂/Ce_0.25Zr_0.75O₂>TiO₂/ZrO₂≈TiO₂. The mechanism role of Ceria–Zirconia mixed oxides in photocatalytic reaction was speculated.

Keywords: TiO; ₂; Benzene; Ceria–Zirconia mixed oxides; Photocatalytic oxidation; Gas-phase

Study on effect of dimples on friction of parallel surfaces under different sliding conditions by Fanming Meng; Rui zhou; Tiffany Davis; Jian Cao; Q.Jane Wang; Diann Hua; Jordan Liu (pp. 2863-2875).

The influence of rectangle dimples with flat bottom on the friction of parallel surfaces at different sliding conditions is investigated based on lubrication equations. The elastic deformation of rough surfaces is evaluated using continuous convolution fast Fourier transform (CC-FFT). The friction coefficients for dimpled and non-dimpled parallel surfaces by simulation are compared with experimental results. Results show that this kind of dimples can reduce the friction coefficient for cases with the smaller ratio of film thickness to roughness ( h/R_q), small roughness or large applied load. The friction force for the parallel surfaces can decrease due to the dimple effect over the range of the larger sliding speed, larger load or smoother surfaces.

Keywords: Friction coefficient; Friction force; Dimple; Parallel surfaces; Lubrication; CC-FFT

Effect of applied bias voltage on corrosion-resistance for TiC1−_xN_x and Ti1−_xNb_xC1−_yN_y coatings by J.C. Caicedo; C. Amaya; L. Yate; W. Aperador; G. Zambrano; M.E. Gómez; J. Alvarado-Rivera; J. Muñoz-Saldaña; P. Prieto (pp. 2876-2883).

Corrosion-resistance behavior of titanium carbon nitride (Ti–C–N) and titanium niobium carbon nitride (Ti–Nb–C–N) coatings deposited onto Si(100) and AISI 4140 steel substrates via r.f. magnetron sputtering process was analyzed. The coatings in contact with a solution of sodium chloride at 3.5% were studied by Tafel polarization curves and impedance spectroscopy methods (EIS). Variations of the bias voltage were carried out for each series of deposition to observe the influence of this parameter upon the electrochemical properties of the coatings. The introduction of Nb in the ternary Ti–C–N film was evaluated via X-ray diffraction (XRD) analysis. The structure was characterized by using Raman spectroscopy to identify ternary and quaternary compounds. Surface corrosion processes were characterized using optical microscopy and scanning electron microscopy (SEM). XRD results show conformation of the quaternary phase, change in the strain of the film, and lattice parameter as the effect of the Nb inclusion. The main Raman bands were assigned to interstitial phases and “impurities” of the coatings. Changes in Raman intensities were attributed to the incorporation of niobium in the Ti–C–N structure and possibly to resonance enhancement. Finally, the corrosion data obtained for Ti–C–N were compared with the results of corrosion tests of Ti–Nb–C–N coating. The results obtained showed that the incorporation of niobium to Ti–C–N coatings led to an increase in the corrosion-resistance. On another hand, an increase in the bias voltage led to a decrease in the corrosion-resistance for both Ti–C–N and Ti–Nb–C–N coatings.

Keywords: PACS; 61.05.cf; 68.30j; 68.35.Ja; 68.43.Pq; 67.80.de; 65.40.gkX-ray scattering; Raman spectra; Electrochemical properties

Effect of complexing agent on the photoelectrochemical properties of bath deposited CdS thin films by S.B. Patil; A.K. Singh (pp. 2884-2889).

In the present paper photoelectrochemical (PEC) performance of bath deposited CdS thin films based on complexing agents i.e. ammonia and triethanolamine (TEA) has been discussed. Effect of annealing has also been analyzed. The as-deposited and annealed (at 523K for 1h in air) films were characterized by X-ray diffraction (XRD), ultraviolet–visible (UV–vis) absorption spectroscopy, SEM, electrochemical impedance spectroscopy (EIS), and PEC properties. XRD studies revealed that the films were nanocrystalline in nature with mixed hexagonal and cubic phases. TEA complex resulted in better crystallinity. Further improvement in the crystallinity of the films was observed after air annealing. The marigold flower-like structure, in addition to flakes morphology, was observed with TEA complex, whereas for ammonia complex only flakes morphology was observed. The UV–vis absorption studies revealed that the optical absorption edge for the films with ammonia and TEA complex was around 475nm and 500nm, respectively. Annealing of the films resulted in red shift in the UV–vis absorption. The PEC cell performance of CdS films was found to be strongly affected by crystallinity and morphology of the films resulted due to complexing agent and annealing. The air annealed film deposited using TEA complex showed maximum short circuit current density ( J_sc) and open circuit voltage ( V_oc) i.e. 99μA/cm² and 376mV respectively, under 10mW/cm² of illumination. The films deposited using TEA complex showed good stability under PEC cell conditions.

Keywords: Complexing agent; TEA; Ammonia; Marigold flower structure; EIS; PEC

An investigation of the internal temperature dependence of Pd–Pt cluster beam deposition: A molecular dynamics study by Cha’o-Kuang Chen; Shing-Cheng Chang (pp. 2890-2897).

We investigated the internal temperature dependence of the Pd1−_aPt_a cluster beam deposition in the present study via the molecular dynamics simulations of soft-landing. By analysis of the velocity distribution and diffusion coefficient of the bimetallic cluster, Pd atoms with better mobility improved the diffusibility of Pt atoms. The radial composition distribution showed that a Pt-core/Pd-shell structure of the cluster formed at high internal temperatures through migrations of the Pd atoms from inner to surface shells. In the soft-landing process, the diffusing and epitaxial behaviors of the deposited clusters mainly depended on the internal temperature because the incident energy of the cluster was very small. By depositing clusters at high internal temperatures, we obtained a thin film of good epitaxial growth as the energetic cluster impact. Furthermore, nonepitaxial configurations such as scattered nonepitaxial atoms, misoriented particles, and grain boundaries of (111) planes were produced in the growth of the cluster-assembled film. As the size of the incident cluster increased, the internal temperature of the cluster needed for better interfacial diffusion and contact epitaxy on the substrate also rose.

Keywords: Cluster beam deposition; Epitaxy; Surface segregation; Bimetallic cluster

Synthesis of ZnO–SnO₂ composite oxides by CTAB-assisted co-precipitation and photocatalytic properties by Zhijun Yang; Linlin Lv; Yali Dai; Zhihui Xv; Dong Qian (pp. 2898-2902).

ZnO–SnO₂ composite oxides with various molar ratios of Sn:Zn have been synthesized at different calcination temperatures via a facile cetyltrimethylammonium bromide (CTAB)-assisted co-precipitation method with Zn(NO₃)₂·6H₂O and SnCl₄·5H₂O as starting materials. XRD, TEM, SEM and BET were employed to characterize the as-prepared samples. It has been found that amorphous intermediates appear between the evolutions of ZnO and SnO₂ crystals. The photocatalytic properties of the composite oxides were investigated using photocatalytic degradation of methyl orange as the probe reaction. The results show that the ZnO–SnO₂ composite oxide with a cube morphology exhibits the best photocatalytic activity, which was prepared with a molar ratio of Zn:Sn of 2:1 and calcination temperature of 700°C.

Keywords: Zinc oxide; Tin oxide; Zinc stannate; Nanocomposites; Chemical preparation; Photocatalytic properties

Synthesis of narrow band gap (V₂O₅)_x–(TiO₂)1−_x nano-structured layers via micro arc oxidation by M.R. Bayati; A.Z. Moshfegh; F. Golestani-Fard (pp. 2903-2909).

V₂O₅–TiO₂ layers with a sheet-like morphology were synthesized by micro arc oxidation process for the first time. Surface morphology and topography of the layers were investigated by scanning electron microscope (SEM) and atomic force microscope (AFM). Phase structure and chemical composition of the layers were also studied by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. It was revealed that the composite layers had a sheet-like structure average thickness of which was about 100nm depending on the applied voltage. The layers consisted of anatase, rutile, and vanadium pentoxide phases fractions of which varied with the applied voltage. The optical properties of the layers were also examined employing a UV–vis spectrophotometer. It was found that the absorption edge of the grown composite layers shifted toward the visible wavelengths when compared to MAO-synthesized pure titania layers. The band gap energy of the composite layers was calculated as 2.58eV. Furthermore, photo-catalytic performance of the layers was examined by measuring the decomposition rate of methylene blue under ultraviolet and visible irradiations. The results demonstrated that about 90% and 68% of methylene blue solution was decomposed after 120min ultraviolet and visible irradiations over the composite layers, respectively.

Keywords: Titanium oxide; Vanadium oxide; Micro arc oxidation; Ceramics; Photo-catalysis

Optical and electrical properties of In-doped CdO thin films fabricated by pulse laser deposition by B.J. Zheng; J.S. Lian; L. Zhao; Q. Jiang (pp. 2910-2914).

Transparent indium-doped cadmium oxide (In-CdO) thin films were deposited on quartz glass substrates by pulse laser deposition (PLD) from ablating Cd–In metallic target at a fixed pressure 10Pa and a fixed substrate temperature 300°C. The influences of indium concentrations in target on the microstructure, optical and electrical performances were studied. When the indium concentration reaches to 3.9wt%, the as-deposited In-CdO film shows high optical transmission in visible light region, obviously enhanced direct band gap energy (2.97eV), higher carrier concentration and lower electric resistivity compared with the undoped CdO film, while a further increase of indium concentration to 5.6wt% induces the formation of In₂O₃, which reverse the variation of these parameters and performance.

Keywords: Cadmium oxide; Pulse laser deposition; Transparent conductor oxide; Hall effect

AFM analysis of bleaching effects on dental enamel microtopography by Ana Carolina Pedreira de Freitas; Luciana Cardoso Espejo; Sergio Brossi Botta; Fernanda de Sa Teixeira; Maria Aparecida A. Cerqueira Luz; Narciso Garone-Netto; Adriana Bona Matos; Maria Cecilia Barbosa da Silveira Salvadori (pp. 2915-2919).

The purpose of this in vitro study was to test a new methodology to evaluate the effects of 35% hydrogen peroxide agent on the microtopography of sound enamel using an atomic force microscope (AFM). The buccal sound surfaces of three extracted human lower incisors were used, without polishing the surfaces to maintain them with natural morphology. These unpolished surfaces were subjected to bleaching procedure with 35% hydrogen peroxide that consisted of 4 applications of the bleaching agent on enamel surfaces for 10min each application. Surface images were obtained in a 15μm×15μm area using an AFM. The roughness (Ra and RMS) and the power spectral density (PSD) were obtained before and after the bleaching treatment. As results we could inquire that the PSD analyses were very suitable to identifying the morphological changes on the surfaces, while the Ra and RMS parameters were insufficient to represent the morphological alterations promoted by bleaching procedure on enamel. The morphological wavelength in the range of visible light spectrum (380–750nm) was analyzed, showing a considerable increase of the PSD with the bleaching treatment.

Keywords: Surface morphology analysis; Dental enamel; Atomic force microscopy; Tooth bleaching; Roughness parameters; Power spectrum density

XRD and XPS characterization of mixed valence Mn₃O₄ hausmannite thin films prepared by chemical spray pyrolysis technique by A. Moses Ezhil Raj; S. Grace Victoria; V. Bena Jothy; C. Ravidhas; Joachim Wollschläger; M. Suendorf; M. Neumann; M. Jayachandran; C. Sanjeeviraja (pp. 2920-2926).

Spray pyrolysis technique has been employed successfully for the synthesis of single phase mixed valence spinel hausmannite (Mn₃O₄) thin films using alcoholic start solution of manganese acetate (Mn(CH₃COO)₂·4H₂O) on pyrex glass substrates at atmospheric pressure using air as a carrier gas. Thermal decomposition of the precursor in the temperature range 320–490°C led to the formation of Mn₃O₄ phase as revealed from the thermogravimetry analysis. Prepared samples are characterized by X-ray diffraction that shows spinel structure with space group I4₁/ amd. Pure and well crystallized specimen is subjected to X-ray photoelectron spectroscopy for the surface chemistry investigation of these systems at a molecular level. Surface Mn/O ratio is compared to the bulk composition of the sample. Atomic force micrographs revealed that the morphology and the surface grains of the films largely influenced by the substrate temperature.

Keywords: PACS; 52.77.Fv; 82.45.Mp; 68.55.jm; 79.60.Bm; 68.55.JSpray pyrolysis; Thin films; XRD; XPS; AFM

Effects of UV-irradiation on the thermo-mechanical properties of optical grade poly(methyl methacrylate) by S. Eve; J. Mohr (pp. 2927-2933).

We studied the evolution of the thermo-mechanical properties of poly(methyl methacrylate) (PMMA) materials exposed to ultra-violet (UV) light. To do so we measured important mechanical parameters including the fracture strength, the stress–strain relation, and Young's modulus as a function of the UV-irradiation dose. We concluded that the mechanical properties of PMMA are affected by UV light. The ductility disappears and the strength and strain at rupture strongly decrease (over 30%). The evolution of the Young's modulus is discussed as a function of the cross-linking degree of the materials. Moreover we observed the occurrence of surface damage, which in its turn enhances the degradation of these mechanical parameters.

Keywords: Poly(methyl methacrylate); UV-irradiation; Photo-chemical degradation; Mechanical properties; Damage evolution

Enhancing indium tin oxide (ITO) thin film adhesiveness using the coupling agent silane by Da Wu; Jiaxiang Liu; Yue Wang (pp. 2934-2938).

The coupling agent γ-mercapto propyl trimethoxy silane (WD-80) was used to enhance the adhesiveness of the indium tin oxide (ITO) thin film, which was prepared on a glass substrate using the sol–gel method. The nano-scratching test, XRD, TEM, SEM, and UV–vis spectrophotometer were employed to examine film adhesion, crystal structure, surface morphology, and transmittance. The results indicated that silane coupling agent, used in low concentration, did not change the film structure but increased the critical load of the film by 49%, from 4.16mN to 6.20mN, when the film was peeled off from the substrate. The principle by which the coupling agent works is discussed. In addition to increasing with the light wavelength, the average transmittance of the film in the visible range varied from 78.9% to 83.6%. Moreover, as a function of the WD-80 silane coupling agent, the film exhibited a high smoothness and density due to the orderly arrangement of particles.

Keywords: Indium tin oxide thin film; Sol–gel method; Silane coupling agent; Adhesiveness; Transmittance

The surface tension of liquid Cu–Fe–Sb alloys by Joanna Willner; Grzegorz Siwiec; Jan Botor (pp. 2939-2943).

The results of study on the influence of temperature and iron and antimony on the surface tension of liquid ternary Cu–Fe–Sb systems are presented. The measurements were carried out with the sessile drop method, in a broad range of the alloy additions concentration (Fe and Sb). It was demonstrated that the surface tension varies as a linear function of temperature and concentration of iron. It was also demonstrated that antimony, in examined alloys, shows the properties characteristic of a surface-active substance, significantly reducing the surface tension value. The changes of the surface tensions as a function of concentration of antimony were described with the Szyszkowski's equation. Composition of surface layer, enriched with an antimony, was determined basing on the model, which used data regarding properties of binary systems. The surface tension values of Cu–Fe–Sb systems was also computed from model and compared with experimental data. A good agreement was obtained.

Keywords: Cu–Fe–Sb alloys; Surface tension; Surface active substance; Sessile drop method

Fabrication of Au thin film gratings by pulsed laser interference by Hyunkwon Shin; Hyeonggeun Yoo; Myeongkyu Lee (pp. 2944-2947).

We report that one-dimensional (1D) and two-dimensional (2D) metal thin film gratings can be directly fabricated by interfering Nd–YAG pulsed laser beams (wavelength=1064nm, pulse width=6ns) incident from the backside of glass substrate. This process utilizes a laser-induced thermo-elastic force which plays a role to detach the film from the substrate. Micro-scale Au transmission gratings with a minimum feature size of 1μm could be generated by interference-driven periodic detachment. The fabrication of tube-structured patterns as well as stripes was also possible by adjusting the pulse power and this is explained with the effect of film cohesion.

Keywords: Metal thin film patterning; Grating; Pulse laser; Interference

In situ preparation and fluorescence quenching properties of polythiophene/ZnO nanocrystals hybrids through atom-transfer radical polymerization and hydrolysis by Xiaoming Peng; Lin Zhang; Yiwang Chen; Fan Li; Weihua Zhou (pp. 2948-2955).

In this paper, a new approach for in situ preparing nanocomposites of conjugated polymers (CPs) and semiconductor nanocrystals was developed. Polythiophene grafted poly(zinc methacrylate) (PTh-g-PZMA) copolymer was synthesized by atom-transfer radical polymerization (ATRP) of zinc methacrylate (ZMA) initiated from the macroinitiator poly(2,5-(3-(bromoisopropyl-carbonyl-oxymethylene) thiophene)) (PTh-Br) with pendant initiator groups. Subsequently, the polythiophene grafted poly(methacrylate)/ZnO (PTh-g-PMA/ZnO) hybrid heterojunction nanocomposites were successfully prepared by in situ hydrolysis of PTh-g-PZMA casting films in alkaline aqueous solution. The structures of PTh-Br, PTh-g-PZMA and PTh-g-PMA/ZnO were confirmed by the proton nuclear magnetic resonance (¹H NMR) spectra, Fourier transform infrared (FTIR) spectra and X-ray photoelectron spectroscopy (XPS). The morphologies of PTh-g-PMA/ZnO films prepared for different hydrolysis time were observed in the cross-sections by scanning electron microscope (SEM). The SEM images revealed that ZnO nanocrystals were uniformly dispersed in polymers without any aggregation and the appearances of ZnO nanocrystals changed from nanoparticles to nanorods with the hydrolysis treatment time increasing. The optical properties of these nanocomposites were studied by ultraviolet–visible (UV–vis) absorption and fluorescence spectroscopy. UV–vis absorption spectroscopy showed that the adsorption band of PTh-g-PMA/ZnO hybrids was broader than that of PTh-Br, implying that the existence of ZnO nanocrystals increased the optical absorption region of hybrids. The photoluminescence (PL) spectra of the hybrids showed that fluorescence quenching occurred in PTh-g-PMA/ZnO blends and a maximum of 85% of the fluorescence intensity quenched in the PTh-g-PMA/ZnO obtained from treatment in NaOH aqueous solution for 2h, which revealed the existence of photo-induced charge transfer between the polythiophene chains and ZnO. These results indicated that the hybrid heterojunction nanocomposites could be promising candidates for photovoltaic applications.

Keywords: Polythiophene; ZnO nanocrystals; ATRP; Hydrolysis

Influence of heat treatment on tribological properties of electroless Ni–P and Ni–P–Al₂O₃ coatings on Al–Si casting alloy by M. Novák; D. Vojtěch; T. Vítů (pp. 2956-2960).

Evolution of tribological properties of electroless Ni–P and Ni–P–Al₂O₃ coating on an Al–10Si–0.3Mg casting alloy during heat treatment is investigated in this work. The pre-treated substrate was plated using a bath containing nickel hypophosphite, nickel lactate and lactic acid. For preparation of fiber-reinforced coating Al₂O₃ Saffil fibers pre-treated in demineralised water were used. The coated samples were heat treated at 400–550°C/1–8h. Tribological properties were studied using the pin-on-disc method. It is found that the best coating performance is obtained using optimal heat treatment regime (400°C/1h). Annealing at higher temperatures (450°C and above) leads to the formation of intermetallic compounds that reduce the coating wear resistance. The reason is that the intermetallic phases adversely affect the coating adherence to the substrate. The analysis of wear tracks proves that abrasion is major wear mechanism, however due to the formed intermetallic sub-layers, partial coating delamination may occur during the pin-on-disc test on the samples annealed at 450°C and above. It was found that fiber reinforcement reduces this scaling and increases wear resistance of coatings as compared to the non-reinforced Ni–P coatings.

Keywords: Al–Si alloy; Electroless coating; Heat treatment; Wear testing

Batch study of arsenate (V) adsorption using Akadama mud: Effect of water mineralization by Rongzhi Chen; Zhenya Zhang; Chuanping Feng; Zhongfang Lei; Yuan Li; Miao Li; Kazuya Shimizu; Norio Sugiura (pp. 2961-2967).

Akadama mud, consisting mainly of different forms of iron and aluminum oxide minerals, was used for arsenate (V) adsorption from aqueous solutions. The adsorption process fitted the first-order kinetic equation and the Langmuir monolayer model well. The adsorption capacity, estimated by the Langmuir isotherm model, was 5.30mg/g at 20±0.5°C. The effects of the solution properties (initial concentration of As (V), pH, temperature, and mineralization degree) on As (V) removal were investigated. Various mineralization degrees in underground water were simulated by adjusting the ionic strength of the solution or adding coexisting ions to the contaminated solution. It was found that mineralization of the water significantly influenced the arsenic adsorption. The existence of multivalent metallic cations significantly enhanced the As (V) adsorption ability, whereas competing anions such as fluoride and phosphate greatly decreased the As (V) adsorption. This result suggests that Akadama mud is more suitable for arsenic adsorption in low-level phosphate and fluoride solutions. The loaded Akadama mud could be desorbed at polar pH conditions, especially in acidic conditions, and more than 65% As (V) sorption has been achieved at pH 1.

Keywords: Arsenate batch adsorption; Akadama mud; Langmuir isotherms; Sorption kinetics; Water mineralization

Exchange versus intercalation of n-dodecanethiol monolayers on copper in the presence of n-dodecaneselenol and vice versa by Grégory Fonder; Joseph Delhalle; Z. Mekhalif (pp. 2968-2973).

n-Dodecanethiol (RSH) and n-dodecaneselenol (RSeH) molecules have been self-assembled on electrochemically reduced copper sheets. To assess the stability of the resulting monolayers, immersion, during different times varying from minutes to hours, of the modified copper in a solution which contains the competitor molecule has been performed. PM-IRRAS shows a good organisation for all monolayers without any divergence. Based on XPS analysis, we have proved an intercalation process of RSeH molecules followed by adsorption on the free sites of copper modified with the RSH and in similar way the insertion and adsorption of RSH molecules in the RSeH modified copper. The only difference between the two directions is in the kinetics which seems to be faster for thiol compared to selenol.

Keywords: n; -Dodecaneselenol; n; -Dodecanethiol; Copper; Stability

A Monte Carlo simulation study of Nitrogen on LiF(001) by A.K. Sallabi; J.N. Dawoud; D.B. Jack (pp. 2974-2978).

The adsorption of N₂ gas on the LiF(001) surface is studied by canonical Monte Carlo (CMC) computer simulation. These results show that N₂ forms an ordered structure where the molecules are arranged in a unit cell ofp(22×2)R45° symmetry at temperatures below 23K with 50% coverage. The nitrogen molecules are tilted by 53° from the surface normal and have the same azimuthal orientation along diagonals, with diagonals alternating their orientation. Beyond 23K, the molecules become azimuthally disordered but with residual short-range order. No change in the position of the peak of the polar (tilt) angle distribution was observed above the transition temperature. This transition is purely of the order–disorder type.

Keywords: Physical adsorption; Monte Carlo simulations; Phase transition; LiF

Stabilization of Au nanoparticles prepared by laser ablation in chloroform with free-base porphyrin molecules by Karolína Šišková; Jiří Pfleger; Marek Procházka (pp. 2979-2987).

Laser ablation (LA) of a Au foil immersed in chloroform and/or in diluted 5,10,15,20-tetrakis-4-pyridylporphine (TPyP) chloroform solutions was carried out using 1064nm nanosecond laser pulses. The products were characterized by UV–visible-NIR optical extinction and IR absorption measurements, Raman spectroscopy and transmission electron microscopy (TEM). They were found to be strongly influenced by the convergence of the incident laser beam and delivered energy per pulse. Our results show that with highly focused laser beam chloroform underwent photochemical reactions and no nanoparticles with observable surface plasmon extinction (SPE) band were formed whereas at particular focusing conditions Au nanoparticles with the SPE band typical for Au organosols were created. Au organosols in pure chloroform showed a limited stability, the SPE band disappeared in a few hours after the preparation. When a small amount of TPyP was present in the course of LA both the efficiency of Au nanoparticles formation and the stability of the resulting organosols were improved. A possible mechanism of LA of the Au target in chloroform and in diluted TPyP chloroform solutions is discussed.

Keywords: PACS; 81.07 Pr (organic–inorganic hybrid nanostructures); 82.70 Dd (colloids)Au nanoparticles; Laser ablation; Chloroform; 5,10,15,20-Tetrakis-4-pyridylporphine (TPyP); Organosols

Electrochemical behaviors of the magnesium alloy substrates in various pretreatment solutions by Yanping Zhu; Gang Yu; Bonian Hu; Xiping Lei; Haibo Yi; Jun Zhang (pp. 2988-2994).

Interface reactions and film features of AZ91D magnesium alloy in pickling, activation and zinc immersion solutions have been investigated. The surface morphologies of the specimens were observed with scanning electron microscope (SEM). Electrochemical behaviors of AZ91D magnesium alloy in the baths of pickling, activation and zinc immersion were analyzed based on the open circuit potential (OCP) - time curves in various solutions. The results show that the corrosive rate in HNO₃+CrO₃ or HNO₃+H₃PO₄ pickling solution was more rapid than in KMnO₄ pickling–activation solution. Both α phase and β phase of the substrates were uniformly corroded in HNO₃+CrO₃ or HNO₃+H₃PO₄ pickling solution, the coarse surface can augment the mechanical occlusive force between the subsequent coatings and the substrates, so coatings with good adhesion can be obtained. In HF activation solution, the chromic compound formed via HNO₃+CrO₃ pickling was removed and a compact MgF₂ film was formed on the substrate surface. In K₄P₂O₇ activation solution, the corrosion products formed via HNO₃+H₃PO₄ pickling were removed, a new thin film of oxides and hydroxides was formed on the substrate surface. In KMnO₄ pickling–activation solution, a film of manganic oxides and phosphates was adhered on the substrate surface. Zinc film was symmetrically produced via K₄P₂O₇ activation or KMnO₄ pickling–activation, so it was good interlayer for Ni or Cu electroplating. Asymmetrical zinc film was produced because the MgF₂ film obtained in the HF activation solution had strong adhesive attraction and it was not suitable for interlayer for electroplating. However, the substrate containing compact MgF₂ film without zinc immersion was fit for direct electroless Ni–P plating.

Keywords: Magnesium alloy; Pickling; Activation; Zinc immersion; Interlayer

A new example of the diffusion-limited aggregation: Ni–Cu film patterns by Hakan Kockar; Mehmet Bayirli; Mursel Alper (pp. 2995-2999).

The mechanism of the growth of the dendrites in the Ni–Cu films is studied by comparing them with the aggregates obtained by Monte Carlo (MC) simulations according to the diffusion-limited aggregation (DLA) model. The films were grown by electrodeposition. The structural analysis of the films carried out using the x-ray diffraction showed that the films have a face-centered cubic structure. Scanning electron microscope (SEM) was used for morphological observations and the film compositions were determined by energy dispersive x-ray spectroscopy. The observed SEM images are compared with the patterns obtained by MC simulations according to DLA model in which the sticking probability, P between the particles is used as a parameter. For all samples between the least and the densest aggregates in the films, the critical exponents of the density–density correlation functions, α were within the interval 0.160±0.005–0.124±0.006, and the fractal dimensions, D_f, varies from 1.825±0.006 to 1.809±0.008 according to the method of two-point correlation function. These values are also verified by the mass-radius method. The pattern with α and D_f within these intervals was obtained by MC simulations to DLA model while the sticking probability, P was within the interval from 0.35 to 0.40 obtained by varying P (1–0.001). The results showed that the DLA model in this binary system is a possible mechanism for the formation of the ramified pattern of Ni–Cu within the Ni-rich base part of the Ni–Cu films due to the diffusive characteristics of Cu.

Keywords: Ferromagnetic thin film growth; Monte Carlo Simulations; Electrodepositing; Fractal dimension

Protein imprinted polymer using acryloyl-β-cyclodextrin and acrylamide as monomers by Wei Zhang; Lei Qin; Run-Run Chen; Xi-Wen He; Wen-You Li; Yu-Kui Zhang (pp. 3000-3005).

A novel protein imprinted polymer was prepared using acryloyl-β-cyclodextrin (β-CD) and acrylamide as monomers on the surface of silica gel. The bovine hemoglobin was used as template and β-CD was allowed to self-assemble with the template protein through hydrogen bonding and hydrophobic interaction. Polymerization was carried out in the presence of acrylamide as an assistant monomer, which resulted in a novel protein imprinted polymer. After removing the template, imprinted cavities with the shape and spatial distribution of functional groups were formed. Bovine serum albumin (BSA) cytochrome c (Cyt) and lysozyme (Lyz) were employed as non-template proteins to test the imprinting effect and the specific binding of bovine hemoglobin to the polymer. The results of the adsorption experiments indicated that such protein imprinted polymer, which was synthesized with β-CD and acrylamide as monomers, could selectively recognize the template protein.

Keywords: Surface molecular imprinting; β-Cyclodextrin; Bovine hemoglobin; Recognition

Sections

Personal tools

Applied Surface Science (v.256, #9)

Sections

Personal tools

Local resources

Applied Surface Science (v.256, #9)