Highly stable, branched gold nanoworms are formed spontaneously in an acetamide-based room temperature molten solvent without any additional external stabilizing or aggregating agent. The nanoworms can be anchored onto solid substrates such as indium tin oxide (ITO) without any change in morphology. The anchored nanoworms are explored as substrates for surface enhanced Raman scattering (SERS) studies using non-fluorescent 4-mercaptobenzoic acid (4-MBA) and fluorescent rhodamine 6G (R6G) as probe molecules. The anchored nanostructured particles respond to near IR (1064 nm) as well as visible (785, 632.8 and 514 nm) excitation lasers and yield good surface enhancement in Raman signals. Enhancement factors of the order 10 6 -10 7 are determined for the analytes using a 1064 nm excitation source. Minimum detection limits based on adsorption from ethanolic solutions of 10 28 M 4-MBA and aqueous solutions of 10 27 M R6G are achieved. Experimental Raman frequencies and frequencies estimated by DFT calculations are in fairly good agreement. SERS imaging of the nanostructures suggests that the substrates comprising of three dimensional, highly interlinked particles are more suited than particles fused in one dimension. The high SERS activity of the branched nanoworms may be attributed to both electromagnetic and charge transfer effects.

No abstract

Microcrystalline cellulose (MCC) was subjected to mechanical and mechanochemical shear in a rubber mixing milling. Nitrile rubber (NBR) and ethylene-propylene-diene monomer (EPDM) rubber were used to induce shear on cellulose during treatment. Solid-state interactions between N ,N-dimethylacetamide/lithium chloride (DMAc/LiCl) and cellulose particles were facilitated during mechanochemical shear. Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy and swelling studies were carried out on MCC, DMAc/LiCl-treated MCC, MCC subjected to mechanical shear and DMAc/LiCl-treated MCC subjected to mechanochemical shear. Crystallinity and swelling behaviour of the untreated and merely DMAc/LiCl-treated MCC samples, in the absence of any shear, were found to be similar. However, when MCC was subjected to mechanical shear assisted by NBR and DMAc/LiCl-treated MCC subjected to mechanochemical shear assisted by EPDM, the resultant MCC samples exhibited significant reduction in their crystalline index with increased swelling. When DMAc/LiCl-treated MCC was subjected to mechanochemical shear assisted by NBR and mechanical shear alone on MCC, assisted by EPDM, did not exhibit any appreciable change in the crystalline index and swelling behaviour of the resultant MCC samples. While NBR-assisted mechanical shear was found to reduce crystallinity in untreated MCC, crystallinity in DMAc/LiCl-treated MCC was found to be reduced significantly with EPDM rubber-assisted mechanochemical shear.

Ground water accounts for nearly 80% of the rural domestic water needs, and 50% of the urban water needs in India. Ground water gets contaminated because of anthropogenic activities. The incidence of fluoride and iron above permissible levels of 1.5 and 1 mg/L respectively occur in 14 Indian states. Various conventional methods are applied for removal of fluoride and iron but, in recent days owing to increasing eco-friendly alternatives like synthetic polymer resins are being considered. The study was focused on using polystyrene (PS) beads packed media for defluoridation and deironing of water. The removal efficiency of fluoride and iron by polystyrene beads (diameter 1.5, 4 and 8 mm) were determined for 1, 2, 3 and 4 L/min flow rates. For maximum flow rate 8 mm PS beads were efficient in reducing fluoride and iron by 94 and 90% respectively. Polystyrene beads proved to be efficient in removal of fluoride and iron.

The thin films of WO3were prepared on cleaned microscopic glass substrates by the electron beam evaporation technique. The films were coated at room temperature using pure WO3pellets as source. The prepared films were further post heat treated at different temperatures (100°C to 350°C) for about 1hr in air. The optical properties of WO3 thin films were studied in detail. The increase in the density of the film as the annealing temperature increases have been confirmed by the transmittance spectra. The film annealed at 250°C shows a strong photoluminescence peak. The peak intensity is found to be less for all other temperature. The observed results were discussed in terms of crystalline nature of WO3.