[en] The electrochemical synthesis of alpha Fe₂O₃ nanoparticles was performed using quaternary ammonium salts viz. TPAB, TBAB and TOAB in an organic medium by optimizing current density and molar concentration of the ligand. The role of ligands in the formation of α phase, structure and magnetic properties was investigated in details. The effect of increasing chain length on the particle size confirmed that as the chain length increases from propyl to octyl, the particle size decreases. X-ray diffraction spectra of as prepared samples and TEM analysis confirmed the amorphous nature of iron oxide. TEM showed beads of iron oxide joined together with a size distribution in the range of 6-30 nm. The Mossbauer studies also support this observation that for the lowest particle size, the line width is broader which successively reduces with increase in particle size. Iron oxide capped with TOAB indicated superparamagnetic nature at room temperature. The resultant internal magnetic field of 506 mm/s due to hyperfine splitting clearly established the formation of α-Fe₂O₃ The infrared spectroscopy and pH measurements revealed the binding of tetra alkyl ligand with iron oxide. The IR spectra and the increase in basicity of as prepared samples confirmed the formation of hydrated iron oxide. Above 800 deg. C the spectra indicated only iron oxide. Surface area obtained by BET method was 205 m²/g

[en] Zinc oxide (ZnO) nanobeads were synthesized by aqueous polymer thermolysis method in air. The precursor powders were prepared using different polymers of varied molecular weights. The influence of annealing temperature from 300 to 1000 deg. C on thermal properties of polymer gel precursors and ZnO nanoparticles is investigated systematically using thermogravimetric analysis (TGA). The nature and structure of different polymers and their affinity towards the solvent seem to be responsible for the formation of ZnO and their surface morphology. X-ray diffraction studies of the synthesized ZnO show polycrystalline hexagonal zincite syn structure. The composition and microstructural features of polycrystalline samples of zinc oxide were studied by FTIR, SEM and TEM. Infrared spectra reveal the formation of zinc oxide and the removal of organic matter at higher temperature. The as prepared samples, synthesized by poly-vinyl alcohol (PVA) of molecular weight 14,000 and 125,000 were decomposed by heating in air, resulting in the formation of spherical and cuboid shapes of ZnO. The results are compared with those of poly-vinyl pyrrolidone (PVP) capped ZnO. The smallest grain size was found in presence of PVP. The role of polymer interactions in the synthesis for obtaining well-dispersed crystallites has also been demonstrated

[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] A study has been undertaken on the effect of crystallization method on the IV ↔ III transition of ammonium nitrate (AN). AN is crystallized in three different ways, viz. recrystallization, evaporative crystallization and melt crystallization. When the samples were crystallized from saturated aqueous solution, ideal crystals were formed, which behaved differently from the crystals formed from the other methods. The DTA examination of the crystals showed that the crystals have different transition behaviour. The moisture uptake of the samples determined were found to have influenced by the mode of crystallization. The samples were further analyzed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The present study showed that the parameters like thermal history, number of previous transformations and moisture content have a very negligible influence on the IV ↔ III transition of AN as compared to the method of crystallization

[en] Graphical abstract: Raman spectra of TiO₂ sample doped with 50% CdS and annealed at 600 °C. Highlights: ► Transformation from anatase to rutile is prohibited in doped TiO₂. ► FTIR study indicates that TiO₂ lattice has been modified in the presence of CdS. ► Raman spectroscopy is found to be more sensitive as compared to XRD. -- Abstract: This report aimed to study the effect of CdS doping in TiO₂ on the phase transformation of TiO₂ from anatase to rutile using X-ray diffraction (XRD) and Raman spectroscopy. CdS-doped TiO₂ nanocomposites have been prepared and characterized using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). We have observed that contrary to bare TiO₂, phase transformation of TiO₂ from anatase to rutile is hindered when doped with CdS at high temperature. Raman spectroscopy is found to be more sensitive for detection of the surface of TiO₂ as compared to XRD.

[en] Highlights: • Oxidation of Ag clusters in the presence of POMs. • Decay rate of Ag atom increases in the presence of POMs. • Ag NPs stabilized by STA show good Raman activity. • Ag NPs stabilized by STA show good bactericidal property. -- Abstract: The mechanisms of reduction of silver ions and subsequently oxidation of silver atoms in the presence of polyoxometalates (POMs) are discussed. A step-by-step room temperature electron reduction of silver ions and its subsequent reactions has been used in this work to monitor oxidation of silver atoms and its clusters. The silver atoms can transfer electron to POMs is revealed by decrease in the yield of silver clusters and increase in their decay rates. The results of continuous γ-irradiation are compared using UV–visible (UV–Vis) absorption spectra, underlying the effect of silver atoms accumulation in the absence of POMs. Silver nanoparticles (Ag NPs) prepared by reduced silicotungstic acid (STA) were used as Raman substrate and also for antibacterial studies against panel of human pathogenic bacteria. The Ag NPs exhibited antibacterial activity against both Gram-positive and Gram-negative bacterial pathogens evaluated by well diffusion assay. The inhibition zones were within the range of 10 to 14 mm. We have also explored the surface enhanced Raman scattering (SERS) activity of the Ag NPs substrates using 1.0 × 10⁻⁷ M solution of crystal violet (CV) as Raman probe molecule. It was possible to detect SERS spectral pattern of CV on Ag NPs substrate with a high signal-to-noise ratio. Both SERS and antibacterial studies show that this simple, low cost, and greener method for synthesizing Ag NPs may be valuable in future studies about SERS sensor development and bio-applications.