[en] Tin oxide thin films were prepared by using a spray pyrolysis technique. It has been shown that the tin oxide thin film doped with thorium shows a high sensitivity towards trimethylamine (TMA) gas. It has been demonstrated that 1.18 wt.% thorium-doped tin oxide has a sensitivity of 2900 towards 800 vol. ppm TMA gas in air, while pure tin oxide has only a sensitivity of 5 at the operating temperature of 225 deg. C. Thorium stabilizes the tin oxide structure at lower deposition temperature, gives improved electrical characteristics and also enhances the sensitivity and selectivity towards TMA. The effect of surface coverage, morphology, oxidation state and amount of Th on the sensitivity and selectivity has been studied. The correlation of thorium doping in tin oxide at different deposition temperatures with morphology, improvement in the selectivity and sensitivity towards TMA is discussed

[en] Graphene-nanocrystalline calcium sulphide has been synthesized using in-situ reduction of calcium salt and graphene oxide. Graphene oxide was prepared using Hummer's method. Surface morphology and crystal structure of samples were observed by transmission electron microscopy (TEM) and X-Ray diffraction (XRD). Ultra thin graphene and graphene oxide sheets with size ranging between tens to several hundreds of square nanometers are observed in TEM images. The TEM micrographs of G-CaS show that CaS particles are embedded in graphene sheets and the average particle size of CaS particles in the composite is less than 50 nm. The reduction in the intensity of various functional groups in FTIR spectrum also confirms the formation of graphene. The UV-Visible spectra of CaS shows absorption peak at 220 nm with a small shoulder at 250 nm whereas in G-CaS 220 nm absorption peak has reduced intensity and the shoulder at 250 nm has now shifted to 270 nm due to modification in the defect structure of CaS by graphene. CaS and G-CaS shows photoluminescence emission at 470 nm (λ_exc. = 375 nm) and 440 nm (λ_exc. = 350 nm) respectively, however emission intensity of G-CaS is relatively lower than CaS. Although the emission intensity is found to be lower than CaS, addition of CaS to graphene in G-CaS complex has made graphene luminescent. XPS spectra also indicate reduction of various oxygen containing functional groups in highly reduced graphene oxide and G-CaS. - Highlights: • G-CaS was synthesized using in situ reduction of calcium salt and graphene oxide. • Samples were characterized by XRD, TEM, PL, FTIR, XPS, Raman Spectroscopy. • TEM of GCaS show CaS particles having size less than 50 nm are embedded in graphene. • G-CaS shows PL emission at 440 nm when excited with 350 nm. • PL emission intensity in case of G-CaS is lower than CaS but it is luminescent

[en] In the present report, CdS and Ag-CdS nanoparticles were synthesized using cysteine as a capping agent. Surface properties CdS and Ag-CdS nanoparticles were studied by X-ray photoelectron spectroscopy (XPS). XPS study of CdS nanoparticles was carried out as a function of pH and for a refluxed sample at pH 11.2. Effect of dopant concentration on surface properties of Ag-CdS nanoparticles was also studied for as prepared samples as well as for annealed sample at 2% doping. Effect of pH, dopant concentration, and effect of particle size on different sulfur species present in the system was studied. Features of Cd 3d, S 2p and Ag 3d core level have been discussed in detail.

[en] Highlights: • First ever study on DEE–kerosene–diesel blends used in CI engine. • DEE–diesel blends have reduced the trade-off between PM and NOx of diesel engine. • Optimum performance blend has been found as DE15D. • Adulteration effects of kerosene with diesel have also been investigated. • Additions of kerosene with DE15D blend have deteriorated the overall engine performance. - Abstract: An experimental investigation had been carried out to evaluate the effects of oxygenated cetane improver diethyl ether (DEE) blends with kerosene and diesel on the combustion, performance and emission characteristics of a direct injection diesel engine. Initially, 2%, 5%, 8%, 10%, 15%, 20% and 25% DEE (by volume) were blended into diesel. The DEE–diesel blends have reduced the trade-off between PM and NOx of diesel engine and the optimum performance blend has been found as DE15D. Similarly, 5%, 10% and 15% kerosene (by volume) were blended into diesel to investigate the adulteration effect. In addition, a study was carried out to evaluate the effects of kerosene adulteration on DE15D by blending with 5%, 10% and 15% kerosene (by volume). The engine tests were carried out at 10%, 25%, 50%, 75% and 100% of full load for all test fuels. Laboratory fuel tests showed that the DEE is completely miscible with diesel and kerosene in any proportion. It was observed that the density, kinematic viscosity and calorific value of the blends decreases, while the oxygen content and cetane number of the blends increases with the concentration of DEE addition. The experimental test results showed that the DEE–kerosene–diesel blends have low brake thermal efficiency, high brake specific fuel consumption, high smoke at full load, low smoke at part load, overall low NO, almost similar CO, high HC at full load and low HC at part load as compared to DE15D blend

[en] Comparatively higher photoluminescence yield along with robustness of core/shell semiconductor nanocrystals make them attractive candidates for studying intricate quantum size effects. Here, we report, one pot synthesis of Zn_1−xCd_xSe graded core/shell structures by exploiting change in the reactivity of precursors. Optical and structural measurements indicate formation of graded structure. Growth mechanism probed by inductively coupled plasma atomic emission spectroscopy shows formation of graded core/shell structure, with CdSe rich core and ZnSe rich shell. Annealing these nanocrystals, in chemical bath, leads to diffusion of Cd from core to shell region. Formation of Zn_1−xCd_xSe alloy is also observed in X-ray photoelectron spectroscopic measurements, confirming the diffusion of Cd from core to shell region. Substantially high photoluminescence quantum efficiency of 60% with narrow line width of about 27 nm, was observed and is attributable to the reduced strain due to graded core/shell structure. - Highlights: ► Graded CdSe/ZnSe core–shell nanocrystals are synthesized exploiting reactivity of precursors. ► Growth mechanism is probed using ICP-AES spectroscopy. ► Reduced strain leads to luminescence efficiency as high as 60%. ► Alloy formation by annealing in chemical bath is probed using XPS.

[en] Cycloocteno-1,2,3-selenadiazole, an organometallic selenium precursor reacts with mercury acetate in aq. N,N'-dimethylformamide (DMF) or in ethylene glycol (EG) at a temperature between 120 and 130 deg. C to afford nano-sized HgSe. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy TEM. The electron diffraction analysis showed crystalline nature of nano-particles of HgSe. The calculation made by XRD suggest the particles size to be less than 20 nm which match well with the observations made by TEM. The current method uses 1,2,3-selenadiazole, an organo-selenium compounds thus extending the scope of organo-chalcogen compound in material science

[en] Different densities of ZnO nanoneedle films have been prepared by pre-coated zinc foils with thin layer of copper and carbon followed by thermal oxidation at 400 deg. C in air. The X-ray diffraction patterns show well defined peaks, which could be indexed to the wurtzite hexagonal phase of ZnO. The scanning electron microscope images clearly reveal formation of ZnO needles on the entire substrate surface. The X-ray photoelectron spectroscopy studies indicate that Cu and C ions are incorporated into the ZnO lattice. Photoluminescence studies evaluate different emission bands originated from different defect mechanism. From the field emission studies, the threshold field, required to draw emission current density of ∼100 μA/cm², is observed to be 2.25 V/μm and 1.57 V/μm for annealed zinc foil pre-coated with copper and carbon, respectively. The annealed film with copper layer exhibits good emission current stability at the pre-set value of ∼100 μA over a duration of 4 h. The results show that buffer layer is an important factor to control the growth rate, resulting in different density of ZnO needles, which leads to field emission properties. This method may have potential in fabrication of electron sources for high current density applications.

[en] Highlights: ► Single step synthesis approach with site preference of silver as a dopant. ► Silver as a crystal dopant with precursors of chromium (nitrate and acetate). ► Valence states of La, Cr, O and silver as a dopant in a perovskite lattice. ► Atomic ratio of constituent elements in bulk as well as surface regime of samples. - Abstract: Crystalline state of lanthanum chromites with silver as a dopant has been studied by X-ray diffraction and transmission electron microscopy reveals microscopic properties of grain boundaries. X-ray photoelectron spectroscopy has been used to analyze surface states with atomic ratio of La, Cr, O and Ag as a dopant. LaCrO₃ shows mixed valence states of chromium while the silver doped samples exhibit differences in chromium concentration with the oxidation of Cr³⁺ to Cr⁶⁺ in presence of chromium nitrate as a precursor salt. Trivalent stable state of chromium is observed for samples synthesized by chromic acetate as a precursor salt.

[en] Graphical abstract: Electrochromic intercalation and deintercalation of Li⁺ ions and electrons is facilitated by providing hexagonal tunnel, trigonal cavity and square window which allows easy and fast insertion and extraction of ions. Highlights: ► Novel two step MW-SGS is first time employed to prepare WO₃ thin films. ► MW-SGS is simple and cost effective technique for preparation of nanostructures. ► Petal-like hexagonal WO₃ nanodisks were successfully deposited. ► O/W ratio calculated by XPS studies is 2.89. ► Good electrochromic performance suggests practical usability of proposed technique. -- Abstract: Use of domestic microwave oven is first time employed for chemical deposition of nanocrystalline hexagonal WO₃ (h-WO₃) thin films. Low cost precursors like sodium tungstate, hydrochloric acid, oxalic acid and potassium sulfate signifies cost effectiveness of this thin film fabrication route. Scanning electron microscopy images reveal formation of petal like nanodisks. A number of analytical techniques were used to characterize the WO₃ petal like nanodisks, including X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy, FT-IR spectroscopy, Raman scattering spectroscopy, UV–visible spectrophotometry and cyclic voltammetry (CV). The X-ray photoelectron spectroscopic studies revealed 2.89 O/W atomic ratio. The electrical transport studies on WO₃ thin films show semiconducting behavior with n-type semiconductivity. The value of determined coloration efficiency is 57.90 cm²/C. The mechanism of Li⁺ intercalation and deinercalation in h-WO₃ matrix is proposed for enhanced electrochromism.

[en] Research highlights: → A rapid synthesis method is reported for nano magnetic particles of nickel ferrite involving direct current transferred arc thermal plasma assisted vapor phase condensation process. → The as synthesized nanoparticles of NiFe₂O₄ are found to be polycrystalline in nature with average particle size of 30 nm; as revealed by the TEM analysis. → The saturation magnetization and coercivity values of the as synthesized particles are found to be dependent on the different operating parameters on account of the cation distributions. → Reasonably high saturation magnetization (48 emu/g) has been assigned to the high degree of crystallinity, achieved on account of high temperature during the growth, and the cation redistribution. - Abstract: A rapid synthesis method is reported for magnetic nanoparticles of nickel ferrite involving thermal plasma assisted vapor phase condensation process. The as-synthesized samples were characterized by X-ray Diffraction, Transmission Electron Microscopy, Vibrating Sample Magnetometer and X-ray Photoelectron Spectroscopy techniques. The average particle size was determined from the TEM micrographs and found to be around 30 nm. The effects of reactor parameters on the magnetic and structural properties have been evaluated, to find the optimized parameters so as to achieve the highest values of saturation magnetization and coercivity. Reasonably high saturation magnetization (48 emu/g) has been assigned to the high degree of crystallinity, achieved on account of high temperature during the growth, and the cation redistribution. The high value of coercivity (115 Oe) is explained on the basis of possible lattice defects arising from the cation redistribution. Detailed analysis of cation distribution using the XRD line intensity data leads to the conclusion that these samples are iron deficit and nickel rich.