用于吖内酯合成的二氧化钛纳米晶体材料PriyankaAnandgaonker,GaneshKulkarni,SureshGaikwad,AnjaliRajbhoj简

Titanium dioxide nanoparticles were prepared by a electrochemical reduction method using parameters such as current density, solvent polarity, distance between electrodes, and concentration of stabilizers to control the size of the nanoparticles. The nanoparticles were characterized by UV-Vis spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy, and their catalytic performance was tested for the synthesis of a series of 4-aryldiene-2-phenyl-5(4)-oxazolones from the cyclodehydration and condensation of the respective aldehyde, hippuric acid and acetic anhydride. Easy availability, reusability and eco-friendliness were some prominent features of the nanocrystalline titanium dioxide catalyst.     

Possible room-temperature ferromagnetism in SnO2 nanocrystalline powders with nonmagnetic K doping

Sn_1 − xK_xO₂ nanocrystalline powders were synthesized by the sol-gel method. The room-temperature ferromagnetism was observed in K-doped samples, and the saturation magnetization increases with the K concentration. It indicates the ferromagnetism induced by holes injecting is possible. First-principles calculations were employed to analyze the effect of defects on the structural and magnetic properties. Taking into account the structural and valence state characterization, the inhomogeneous distribution of dopants and the holes compensation effect of K and H interstitials in crystal were thought to play important roles in reducing the magnetic moments in samples.     

Effect of incorporation of reduced graphene oxide on ZnO-based dye-sensitized solar cells

Here, we demonstrate a facile method to improve the cell performance of ZnO-based dye sensitized solar cell by incorporating different amount of reduced graphene oxide (rGO). Overall photo-to-current conversion-efficiency (PCE) of the device 3 with 0.75 mL rGO exhibits a 1.3 times improvement compared to bare ZnO. The electrochemical impedance spectroscopy (EIS) measurements show that the enhancement could be attributed to the improvement of electron transport/injection and the decrease of the charge recombination in the device, which arise from the formation of rGO-based Schottky junction in ZnO-photoanode.     

Laser fabrication nanocrystalline coatings using simultaneous powders/wire feed

Laser melting deposition (LMD) fabrication is used to investigate feasibilty of simultaneously feeding TC17 wire and the Stellite 20–Si₃N₄–TiC–Sb mixed powders in order to increase the utilization ratio of materials and also quality of LMD composite coatings on the TA1 substrate. SEM images indicated that such LMD coating with metallurgical joint to substrate was formed free of the obvious defects. Lots of the ultrafine nanocrystals (UNs) were produced, which distributed uniformly in some coating matrix location, retarding growth of the ceramics in a certain extent; UNs were intertwined with amorphous, leading the yarn-shape materials to be produced. Compared with substrate, an improvement of wear resistance was achieved for such LMD coating.     

Band gap bowing of nanocrystalline Zn(1−x)CaxO thin films for blue and ultraviolet optoelectronic applications

Alloying materials having different band gaps is a tool to tailor the optical energy gaps of semiconducting materials. In the present study, the effect of alloying ZnO with CaO was investigated. Thin films of Zn_(1−x)Ca_xO (0 ≤ x ≤ 0.20) were deposited on glass substrates by spray pyrolysis technique. All the films possessed nanocrystalline grains and crystallinity deteriorated with increase in Ca²⁺ substitution level. Elemental composition analysis confirmed the presence of Ca in the samples. Films showed good optical transmission in the visible and near infrared region and the absorption edge blue-shifted with Ca²⁺ substitution. Optical energy gap enhanced by 9.89% upon 20% Ca²⁺ substitution. Photoluminescence analysis also confirmed band gap broadening with mesovalent cation substitution.     

Fast Ion Conducting Nanocrystalline Alkaline Earth Fluorides Simply Prepared by Mixing or Manual Shaking

Simple mixing or shaking of alkaline earth hydroxides with ammonium fluoride results in nanocrystalline phase pure metal fluorides MF₂ (M: Ca, Sr, Ba). The formation of the alkaline earth fluorides was investigated by varying the reaction conditions. Evidence was found that just the contact between the starting materials is sufficient for the reaction to take place. X‐ray diffraction, elemental analysis, ¹⁹F MAS NMR spectroscopy, and measurements of DC conductivities were used to characterize the fluorides regarding properties like crystal structure, crystallite sizes, local fluorine coordination, and fluorine ion conductivity. The ¹⁹F MAS NMR spectra of the phase pure fluorides prepared showed several signals, which were assigned to defects, impurities, or geometric distortions. The fluorides prepared by mixing or shaking revealed fluorine ion conductivities several orders of magnitude higher than observed for the respective microcrystalline alkaline earth fluorides. Therefore, the synthesis routine presented in this study may open a path to a very quick and simple synthesis of nanocrystalline fast fluorine ion conductors.     

Solvothermal Preparation and Effects of Mixed Solvent on the Properties of Copper Indium Diselenide Nanoalloys

We have developed a simple solvothermal method by using solvent mixtures of ethylenediamine with ethanol and deionized water to produce the CuInSe₂ nanoalloys. The phase structure, morphology, elemental composition and optical band gap (E_g) of synthesized the CuInSe₂ nanoalloys were characterized by Raman spectroscopy, X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray spectroscopy (EDS) and zeta potential particle sizer measurements. The factors affecting product purity in the mixed solvent are also discussed. The results showed that CuInSe₂ nanoalloys with a chalcopyrite tetragonal structure were produced by adjusting the ratio of ethylenediamine to ethanol (1:2.33 by volume) and their corresponding energy band gap was found to be 1.27 eV. In addition, we prepared and coated the CuInSe₂ ink on the Mo substrate by the doctor blade method to produce a compact thin film. The crystallinity and the morphology of these polycrystalline CuInSe₂ films were characterized.     

Luminescence studies on swift heavy ion irradiated nanocrystalline aluminum oxide

Pellets of nanocrystalline aluminum oxide synthesized by a combustion technique are irradiated with 120 MeV Au⁹⁺ ions for fluence in the range 5×10¹¹-1×10¹³ ions cm⁻². Two photoluminescence (PL) emissions, a prominent one with peak at ∼525 nm and a shoulder at ∼465 nm are observed in heat treated and Au⁹⁺ ion irradiated aluminum oxide. The 525 nm emission is attributed to F₂²⁺-centers. The PL intensity at 525 nm is found to increase with increase in ion fluence up to 1×10¹² ions cm⁻² and decreases beyond this fluence. Thermoluminescence (TL) of heat-treated and swift heavy ion (SHI) irradiated aluminum oxide gives a strong and broad TL glow with peak at ∼610 K along with a weak shoulder at 500 K. The TL intensity is found to increase with Au⁹⁺ ion fluence up to 1×10¹³ ions cm⁻² and decreases beyond this fluence.     

Nanocrystallite interface effect and exchange bias phenomenology in Cr2O3 and NiO nanoparticles

Nanocrystalline Cr₂O₃ and NiO are prepared using high-energy ball milling. Average sizes of the particles obtained from Scanning Electron Microscopy and crystallite sizes obtained from X-ray diffraction are larger for Cr₂O₃ than NiO particles. At low temperature, large high-field magnetization and small coercivity lead to a weak exchange bias for Cr₂O₃, whereas small high-field magnetization and large coercivity lead to a considerable exchange bias for NiO. The training effect is observed for NiO at 4 K which could be described with a recursive formula constructed in the framework of the spin configurational relaxation model. The results suggest that the pinning mechanism at the interface between the antiferromagnetic and the weak ferromagnetic component ascribed to uncompensated spins leads to the exchange bias effect.     

Decay processes of photoluminescence in a nanocrystalline SiC thin film

Nanocrystalline (nc)-SiC film has been deposited by helicon wave plasma enhanced chemical vapor deposition technique and intense blue-white light emission is obtained. Microstructure analyses show that the 3C–SiC particles are embed in amorphous SiC matrix, and the average size of the nc-SiC is 3.96 nm. The photon energy of the main photoluminescence (PL) band is higher than the band gap of bulk SiC, which indicates that the optical emission mainly occurs in quantum states of 3C–SiC nanocrystals. In addition, the band tail states of amorphous SiC also contribute to the optical emission. Three decay processes are obtained from time-resolved PL spectra by deconvolution treatment, and the decay components correspond to the quantum confinement effect (QCE), surface states of nc-SiC particles, and band tail of amorphous SiC, respectively. The fractional integrated PL intensity of QCE related decay process decreases dramatically in the lower PL photon energy, indicating that the QCE mainly contributes to the short wavelength optical emission.