Humidity Effect on Transport Properties of Titanium Dioxide Nanoparticles

Rutile TiO2 nanoparticles were synthesized using co-precipitation method with an average diameter of 30 nm TiO2 nanoparticle device was then fabricated on glass substrate.Aluminum electrodes were defined using photolithography and vacuum evaporation.A suspension of TiO2 nanoparticles was prepared in isopropanol using ultrasonic agitation.The nanoparticles were deposited between the electrodes.The device was tested by AC electrical measurements at 40%-90%relative humidity（RH）.The impedance of the TiO2nanoparticles decreases by about 80 times with the increase in RH from 40%to 90%at 100 Hz.The response time and the recovery time were 4 s and 5 s,respectively between 40%and 90%RH.At 100 Hz,the sensitivity of the aluminum electrode TiO2 nanoparticle device in the range of 40%—90%RH was17 MΩ/%RH.Complex modulus analysis also confirms the increase in DC conductivity of TiO2 nanoparticles as RH increases.     

Structural,Optical,Antibacterial and Antifungal Properties of Zirconia Nanoparticles by Biobased Protocol

Biological entities and inorganic materials have been in constant touch with each other ever since inception of life on earth.This method has lots of merits such as not requiring complex procedures,template supporting etc.In this work,Aloe vera plant mediated synthesis of tetragonal zirconia nanoparticles has been performed and thermogravimetric and differential thermal analysis（TG/DTA）,X-ray diffraction（XRD）,scanning electron microscopy（SEM） with energy dispersive X-ray spectroscopy（EDX）,atomic force microscopy（AFM）,ultraviolet—visible（UV—VIS） technique and Fourier transform infrared spectroscopy（FTIR） have been provided for characterizing the nanoparticles.Formation of homogeneously distributed spherical zirconia nanoparticles of 50—100 nm in size is predicted.The antimicrobial and antifungal properties are also investigated for synthesis of zirconia nanoparticles and the treated cotton by agar diffusion method against Staphylococcus aureus and Escherichia coli bacterial pathogens and fungal strains Candida albicans and Aspergillus niger,respectively.     

Synthesis of Nanocrystalline FeS2 with Increased Band Gap for Solar Energy Harvesting

In this paper,we have reported the synthesis of FeS2 of higher band gap energy（2.75 eV） by using capping reagent and its successive application in organic-inorganic based hybrid solar cells.Hydrothermal route was adopted for preparing iron pyrite（FeS2） nanoparticles with capping reagent PEG-400.The quality of synthesized FeS2 material was confirmed by X-ray diffraction,field emission scanning electron microscopy,transmission electron microscopy,Fourier transform infrared,thermogravimetric analyzer,and Raman study.The optical band gap energy and electro-chemical band gap energy of the synthesized FeS2 were investigated by UV-vis spectrophotometry and cyclic voltammetry.Finally band gap engineered FeS2 has been successfully used in conjunction with conjugated polymer MEHPPV for harvesting solar energy.The energy conversion efficiency was obtained as 0.064%with a fill-factor of 0.52.     

Enhanced Stability of Anisotropic Gold Nanoparticles by Poly（N-isopropylacrylamide）

A simple synthetic method has been described to prepare anisotropic gold nanoparticles （AuNPs） possessing unique optical and structural properties at room temperature, and subsequently the nanoparticles have been stabilized by temperature-sensitive poly（N-isopropylacrylamide）, or poly（NIPAM）. Although poly（NIPAM） does not exhibit a strong binding affinity to gold, simply introducing poly（NIPAM） to these unstable anisotropic AuNPs can maintain the original structures and absorption properties for several weeks. This increased stability is presumably caused by the adsorbed polymer layer around the anisotropic AuNPs. The existence of adsorbed linear poly（NIPAM） around the AuNPs is confirmed through the reversible absorption properties of the nanoparticles upon heating and cooling. To verify the presence of weak attractive forces （e.g., van der Waals, dipole-dipole, and possible hydrogen bonding） between the polymer and the AuNPs, various concentrations of linear poly（NIPAM） are introduced during the formation of the AuNPs resulting in the systematical control of the size and roughness of the nanoparticles. In addition, the preferential attachment of pre-formed anisotropic AuNPs on cross-linked poly（NIPAM） nanoparticles indicates the presence of weak attractive forces between AuNPs and poly（NIPAM）. As such, poly（NIPAM） and its derivatives can serve as a useful stabilizing and capping agent to preserve the properties of the anisotropic AuNPs.     

Synthesis,Characterization and Biocompatibility of Potassium Ferrite Nanoparticles简

In the present study,morphology,size distribution,structure,biocompatibility and magnetic properties of potassium ferrite nanoparticles(KFeO_2 NPs),synthesized by conventional sol—gel method have been reported.The formation of spherical nanoparticles with orthorhombic structure has been confirmed by scanning electron microscopy and X-ray diffraction.The particle size,as obtained by transmission electron microscopy has been found to be in the range of 4—7 nm.Further,the size distribution has been scrutinized using Analyse-it software,where a platykurtic feature in the size distribution was observed.Fourier transform-infrared spectroscopy and thermogravimetric analysis showed the formation of metal(Fe,K) bonds at Neel temperature of 337℃.Vibrating sample magnetometer analysis revealed the superparamagnetic behaviour of the synthesized KFeO_2NPs,with saturation magnetization of 25.72 emu/g.In vitro cytotoxicity test,using MTT assay,on T cell lines(Jurkat cells) showed that KFeO_2 NPs are biocompatible at a particle concentration of 100 |j.g/ml.     

Effect of Fuel to Oxidant Molar Ratio on Structural and DC Electrical Conductivity of ZnO Nanoparticles Prepared by Simple Solution Combustion Method

ZnO nanoparticles of different sizes were prepared by varying the molar ratio of glycine and zinc nitrate hexahydrate as fuel and oxidizer （0.1, 0.8, 1.11, 1.3, 1.5, 1.7, 2.0） by simple solution combustion method. UV-Visible spectrophotometry studies show that, the band gap of the prepared ZnO nanoparticles increases with increasing fuel to oxidant （F/O） molar ratio up to 1.7 revealing the formation of ZnO nanoparticles. The decrease in band gap for the sample of F/O molar ratio 2.0 is due to an increase in particle size. Powder X-ray diffraction patterns of the prepared samples show the formation of single phase ZnO nanoparticles and the particle size decreases with increasing F/O molar ratio up to 1.7. Surface morphology of the prepared samples was studied by scanning electron microscopy and it was observed that, the porosity increases with increasing F/O molar ratio. DC electrical conductivity at room temperature and in the temperature range of 303-563 K was studied for all the samples and the results revealed that, the sample of F/O molar ratio 1.7 has low electrical conductivity at room temperature and high EAR （high temperature activation energy） compared to other samples.     

Nanocrystalline Growth Activation Energy of Zirconia Polymorphs Synthesized by Mechanochemical Technique

The synthesis of ZrO_2 by mechanochemical reaction using ZrCI_4 and CaO as raw materials and subsequent annealing of the products were investigated.The effect of thermal treatment on the structural evolution and morphological characteristics of the nanopowders was studied by X-ray diffractometry,Raman spectroscopy,transmission electron microscopy,scanning electron microscopy,differential thermal analysis and Rietveld refinement.The results showed that the average crystallite size of ZrO_2 was less than 100 nm up to around1100 ℃.The activation energy for ZrO_2 nanocrystallite growth during calcination was calculated to be about13,715 and 27,333 J/mol for tetragonal(t-ZrO_2) and monoclinic(m-ZrO_2) polymorphs,respectively.Mechanism of the nanocrystallite growth of the ZrO_2 polymorphs during annealing is primarily investigated.     

Hydrothermal Synthesis of CsxWO3 and the Effects of N2 Annealing on its Microstructure and Heat Shielding Properties

Cesium tungsten bronze(Cs_xWO_3) powders were synthesized by hydrothermal reaction at 190 ℃ by using sodium tungstate and cesium carbonate as raw materials,and the effects of N_2 annealing on the microstructure and near-infrared(NIR) shielding as well as heat insulation properties of Cs_xWO_3 were investigated.The results indicated that the synthesized Cs_xWO_3 powders exhibited hexagonal Cs_(0.32)WO_3crystal structure,and subsequent N_2 annealing could further improve the crystallinity of CsxW03 particles.Moreover,the NIR shielding and heat insulation properties of Cs_xWO_3 could be further improved after N_2annealing at appropriate temperature for a period of time.Particularly,the 500 ℃-annealed Cs_xWO_3 products in the N_2 atmosphere showed the best NIR shielding and heat insulation properties.When the N_2 annealing temperature was higher than 700 ℃,the NIR shielding properties decreased again.The 800 ℃-annealed samples in the N_2 atmosphere showed higher visible light transmittance,however,the NIR shielding properties were lower than that of the non-annealed samples.     

CaCO3/TiO2 Nanoparticles Based Dye Sensitized Solar Cell

In this communication,the synthesis and structural,morphological,optical,and photo-electrochemical properties of TiO_2 and CaCO_3/TiO_2 nanoparticles as well as their applications in dye sensitized solar cells(DSSCs),have been reported.In an X-ray diffraction pattern of CaCO_3/TiO_2 nanoparticles,the peak at 29.41°of CaCO_3 has been detected,demonstrating its coating on the surface of TiO_2,which is further verified using high resolution-transmission electron microscopy,energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy.The strong quenching in photoluminescence emission,in the case of CaCO_3/TiO_2nanoparticles,has been attributed to the decrease in recombination rate of photo-generated electron—hole pairs.In the case of UV—visible reflectance spectra,the absorption edge for CaCO_3/TiO_2 nanoparticles has slightly been found to be blue-shifted as compared to bare TiO_2 nanoparticles,which corresponds to an increase in energy band gap of the former.The dye desorption studies reveal that CaCO_3/TiO_2 electrodes adsorbed more dye than the bare TiO_2 electrode.CaCO_3/TiO_2 based DSSC show improved photoelectrochemical properties compared to the bare TiO_2 based DSSC as CaCO_3 coating on TiO_2 forms an energy barrier,and,consequently suppressing the charge recombination,and,thus,improving the overall energy conversion efficiency(η) from 0.46%to 1.44%under the illumination of simulated light of 100 mW/cm~2.     

A Novel Synthesis of Malic Acid Capped Silver Nanoparticles using Solanum lycopersicums Fruit Extract

Integration of green chemistry principles to nanotechnology is one of the key issues in nanoscience research. The development of the concept of green nanoparticle preparation has been growingly needed for environmentally benign metal nanoparticle synthesis protocols to avoid adverse effects in medical applications. Keep this in mind, in the present study, silver nanoparticles were synthesized using Solanum lycopersicums fruit extract. The prepared silver nanoparticles were characterized by UV-visible spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy techniques. The surface plasmon resonance peak was found at 445 nm. The synthesized silver nanoparticles were spherical in shape with the average size of 10 nm. The citric acid present in S. lycopersicums fruit extract acted as reducing agent and malic acid was responsible for capping of the bioreduced silver nanoparticles.     

A Facile Synthetic Approach to Reduced Graphene Oxide-Fe3O4 Composite as High Performance Anode for Lithium-ion Batteries

Reduced graphene oxide-Fe3O4（rGO—Fe3O4） composite has been prepared via a facile and effective hydrothermal method by synthesizing Fe3O4 nanospheres on the planes of reduced graphene oxide（rGO）.Characterizations suggest the successful attachment of Fe3O4 nanospheres to rGO sheets.The rGO—Fe3O4composite（66.7 wt%of Fe3O4 in the composite） exhibits a stable capacity of 668 mAh g-1 without noticeable fading for up to 200 cycles in the voltage range of 0.001—3.0 V,and the superior performance of rGO-Fe3O4 is clearly established by comparison of the results with those from bare Fe3O4 nanospheres（capacity declined to 117 mAh g-1 only at the 200 th cycle）.The excellent electrochemical performance of rGO—Fe3O4 composite can be attributed to the fact that the uniform dispersion of the Fe3O4 nanospheres growing on the rGO sheets avoids aggregation during Li uptake-release cycling,which is desired for cycle stability.Meanwhile,the rGO sheets afford not only elastic buffer to alleviate the volume variations of Fe3O4nanospheres,but also good ionic and electronic transport medium in the electrode.     

Density Functional Theory Study on the Oxidation of Hydrosilylated Silicon Nanocrystals

As a leading surface modification approach,hydrosilylation enables freestanding silicon nanocrystals(Si NCs) to be well dispersed in a desired medium.Although hydrosilylation-induced organic layers at the NC surface may somehow retard the oxidation of Si NCs,oxidation eventually occurs to Si NCs after relatively long time exposure to air.We now investigated the oxidation of hydrosilylated Si NCs in the frame work of density functional theory(DFT).Three oxygen configurations that may be introduced by the oxidation of a Si NC are considered.It is found that a hydrosilylated Si NC is less prone to oxidation than a fully H-passivated Si NC in the point of view of thermodynamics.At the ground state,backbond oxygen(BBO) and hydroxyl(OH) hardly change the gap between the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital(LUMO) of a hydrosilylated Si NC.At the excited state,the decrease in the HOMO-LUMO gap induced by the introduction of doubly bonded oxygen(DBO) is more significant than that induced by the introduction of BBO or OH.We have correlated the changes in the optical absorption(emission) of a hydrosilylated Si NC after oxidation to those of the HOMO—LUMO gap at the ground state(excited state).     

Microstructure Evolution and Tensile Properties of Ti3Al/Ni-based Superalloy Welded Joint

In the present work,the dissimilar joining of a Ti_3AI-based alloy to a Ni-based superalloy was attempted by gas tungsten arc(GTA) welding technology.Sound joints were successfully achieved by using a Cu—Ni alloy as filler material.According to X-ray energy dispersive spectroscopy and X-ray diffraction analysis results three transitional layers at the weld/Ti_3AI interface were verified as follows:Ti_2AINb phase dissolved with Cu and Ni;AI(Cu,Ni)_2Ti,(Cu,Ni)_2Ti and(Nb,Ti) solid solution;Cu-rich phase and a complex multi-element phase.The In718/weld interface is characterized by solid solutions of Ni,Cu,Cr,Fe and Nb.The average tensile strength of the as-welded joints at room temperature is 1 63 MPa,and after a post—weld heat treatment it is increased slightly to 177 MPa.The fracture occurred at the surfacial layer of the joined Ti_3AI base alloy,indicating that the Ti_2AINb layer dissolved with Cu and Ni is the weak link of the Ti_3AI/ln71 8 joint.     

Tensile Strength and Electrical Conductivity of Carbon Nanotube Reinforced Aluminum Matrix Composites Fabricated by Powder Metallurgy Combined with Friction Stir Processing

A route combining powder metallurgy and subsequent friction stir processing was utilized to fabricate carbon nanotube(CNT) reinforced Al(CNT/AI) and 6061 Al(CNT/6061AI) composites.Microstructural observations indicated that CNTs were uniformly dispersed in the matrix in both CNT/AI and CNT/6061 AI composites.Mg and Si elements tended to segregate at CNT—Al interfaces in the CNT/6061 AI composite during artificial aging treatment.The tensile properties of both the Al and 6061 Al were increased by CNT incorporation.The electrical conductivity of CNT/AI was decreased by CNT addition,while CNT/6061 AI exhibited an increase in electrical conductivity due to the Mg and Si segregation.     

Synthesis,Surface Characterization and Photocatalytic Activity of TiO2 Supported on Almond Shell Activated Carbon

Three types of photocatalysts were synthesized by metal organic chemical vapor deposition and impregnation methods using the almond shell activated carbon as support. These photocatalysts denoted by （TiO2/ASAC （V）, TiO2/ASAC （11） and TiO2/ASAC （12）） were characterized by scanning electron microscopy （SEM）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, diffuse reflectance spectroscopy （DRS） and nitrogen adsorption-desorption isotherms. SEM observation shows that TiO2 was deposited on activated carbon surface. XRD results confirm that TiO2 existed in a mixture of anatase and rutile phases. The DRS spectra show the characteristic absorption edge of TiO2 at approximate 380 nm corresponding to the optical band gap of 3.26 eV. Besides, FTIR spectrum indicated the presence of （Ti-O） groups. The specific surface area of photocatalysts decreased drastically in comparison with the original activated carbon. The catalysts were very efficient for the photodegradation of total organic carbon （TOC） from industrial phosphoric acid solution under UV irradiation. The kinetics of photocatalytic TOC degradation was found to follow a pseudo- first-order model. The prepared TiO2/ASAC showed high photoactivity for the photodegradation of TOC in the following order： TiO2/ASAC （V） 〉 TiO2/ASAC （11） 〉 TiO2/ASAC （12） 〉 ASAC 〉 TiO2 （P25）.     

Influences of Reaction Parameters and Ce Contents on Structure and Properties of Nano-scale Ce-HA Powders

Ce-incorporated apatite（Ce-HA） nano-scale particles with different Ce percentage contents（atomic ratio of Ce to Ce ＋ Ca is 5%,10%and 20%,respectively） were synthesized via a simple wet chemical method in this study.The crystal structure,chemical groups,thermal stability,crystal morphologies and crystal sizes of the Ce-HA nano-particles were characterized by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR）,and transmission electron microscopy（TEM）.The influences of reaction temperature,reaction time,pH value,and the atomic ratio of Ce to Ce ＋ Ca on the structure and performance of Ce-HA particles were studied.The results show that the lattice constants,particle sizes,crystallinity and thermal stability of Ce-HA vary with the doped Ce contents.With the increase of Ce content,the lattice constants of the Ce-HA nano-particles remarkably increase but the particle size,crystallinity and thermal stability gradually decrease.The reaction temperature as well as the reaction time has no significant effect on the properties of the final products,while the pH value has a direct relationship with their final chemical composition.The obtained Ce-HA nanosize particles possess potential application in preparing artificial bone implants,bone tissue engineering scaffold and other bioactive coatings.     

Photoelectrochemical Performance of Nb-doped TiO2 Nanoparticles Fabricated by Hydrothermal Treatment of Titanate Nanotubes in Niobium Oxalate Aqueous Solution

Nb-doped TiO2 nanoparticles were prepared by hydrothermal treatment of titanate nanotubes in niobium oxalate aqueous solution.The effect of Nb doping and rutile content on the photoelectrochemical performance based on TiO2 powder electrodes was investigated.The results show that Nb-doped TiO2 with a small amount of rutile exhibits the enhanced photoelectric conversion efficiency for dye-sensitized solar cell.The highest photoelectric conversion efficiency of 8.53%is obtained for 1%Nb—TiO2 containing a small amount of rutile.When a small amount of rutile contained in 2%Nb—TiO2,a higher photoelectric conversion efficiency of8.77%is achieved.     

Dry Sliding Tribological Properties of a Dendrite-reinforced Zr-based Bulk Metallic Glass Matrix Composite

In-situ dendrite-reinforced metallic glass matrix （MGM） composites with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 were prepared with a vacuum arc melter by the copper mold suction casting. Effect of different normal loads and sliding velocities on the tribological properties of MGM composites was studied. The results showed that the friction coefficient and wear rate of composites initially descended with increasing the normal load and reached a minimum of 0.339 and 1.826 × 10^-4 mm^3/（N m） at 10 N, respectively, then ascended. Similarly, the friction coefficient and wear rate of composites initially decreased with the increase in the sliding velocity and reached a minimum of 0.330 and 2.389 × 10^-4 mm^3/（N m） at 0.4 m/s and 0.3 m/s, respectively, then raised. The wear mechanism of composites was mainly adhesive wear accompanied by abrasive wear at lower normal load and sliding velocity. However, the wear mechanism of composites was abrasive wear and adhesive wear as well as delamination at higher normal load and sliding velocity due to the nucleation and propagation of surface and subsurface cracks during the wear process. The flake-like and particle-like wear debris was the dominant shapes of debris observed.     

In Vitro Comparative Effect of Three Novel Borate Bioglasses on the Behaviors of Osteoblastic MC3T3-E1 Cells

Most related investigations focused on the effects of borate glass on cell proliferation/biocompatibility in vitro or bone repair in vivo; however, very few researches were carried out on other cell behaviors. Three novel borate bioglasses were designed as scaffolds for bone regeneration in this wok. Comparative effects of three bioglasses on the behaviors of osteoblastic MC3T3-E1 cells were evaluated. Excellent cytocompatibility of these novel borate bioglasses were approved in this work. Meanwhile, the promotion on cell proliferation, protein secretion and migration with minor cell apoptosis were also discussed in details, which contributed to the potential clinical application as a new biomaterial for orthopedics.     

Effects of Y on the Microstructure,Mechanical and Bio-corrosion Properties of Mg-Zn-Ca Bulk Metallic Glass

The micro-alloying effects of Y on the microstructure, mechanical properties, and bio-corrosion behavior of Mg69-xZn27Ca4Yx（x= 0, 1, 2 at.%） alloys were investigated through X-ray diffraction, compressive tests,electrochemical treatments, and immersion tests. The Mg69Zn27Ca4 alloy was found to be absolutely amorphous, and its glass-forming ability decreased with the addition of Y. The Mg68Zn27Ca4Y1 alloy exhibited an ultrahigh compressive strength above 1010 MPa as well as high capacity for plastic strain above 3.1%.Electrochemical and immersion tests revealed that these Y-doped MgeZ neC a alloys had good bio-corrosion resistance in simulated body fluid（SBF） at 37℃. The results of the cytotoxicity test showed high cell viabilities for these alloys, which means good bio-compatibility.