Detection of heavy metals, SERS and antibacterial activity of polyvinylpyrolidone modified plasmonic nanoparticles.

Selective and sensitive optical sensor based on surface plasmon resonance for detection of various heavy metals in water using polyvinylpyrolidone modified silver nanoparticles was explained in this present study. The prepared nanoparticles were characterized by UV-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM). UV-visible spectra show the surface plasmon resonance (SPR) peak at 409 nm corresponding to silver nanoparticles. Crystalline nature of the nanoparticles was evident from TEM images and XRD analysis. TEM images showed average size of 10 nm for prepared silver nanoparticles. FTIR analysis provides the presence of various functional groups responsible for the reduction and stability of the prepared silver nanoparticles. SERS gives the molecular orientation of the adsorbed pyridine molecules via its nitrogen lone pair of electrons on the surface of silver. Prepared polyvinylpyrolidone modified silver nanoparticles (AgNPs) are demonstrated to detect the concentration of heavy metal contaminant Fe3+ ions in water based on linear change in surface plasmon resonance absorption strength. In addition, AgNPs showed promising activity towards E.coli. These observed optical properties suggest the possible utilization of prepared nanoparticles in the application of water purification.

Improved photocatalytic activity for degradation of textile dyeing waste water and thiazine dyes using PbWO4 nanoparticles synthesized by co-precipitation method.

The coloured dyes released from the textile industrial effluents into water resources cause non-aesthetic pollution and aquatic life toxicity. Thus textile waste water treatment has been studied globally for many years. Photocatalytic properties of lead tungstate (PbWO4) nanoparticles (NPs) were analyzed for thiazine dyes and textile waste water under ultraviolet light conditions. XRD result showed the tetragonal scheelite structure of PbWO4 NPs. The crystallinity of the sample was confirmed from the SAED and XRD pattern. The existence of stretch vibration of Pb-O and O-W-O confirmed from FTIR results. EDAX displays optical absorption signals of Pb, W and O, and confirm the formation of PbWO4. Optical studies reveal that the band gap of the obtained nanoparticles increases with respect to their bulk counterparts that may be attributed to reduction in particle size. TEM images of PbWO4 powder consists of hexagonal particles and relatively uniform and smooth surface rod shaped prism-like structures. The photocatalytic activity of the prepared nanoparticles was analyzed through the degradation of textile waste water under UV light irradiation. The photocatalytic reaction rate constant was found to be 0.014/min. The small sized PbWO4 particles can adsorb more OH groups and oxidatively degrade the pollutants in the textile waste water.