Design of NiS/CNTs nanocomposites for visible light driven catalysis and antibacterial activity studies

The outstanding photocatalytic activity of metal sulphide based photocatalysts have much attention in environmental remediation due to utilization of wide spectrum range. In present paper, the photocatalytic activity of NiS and NiS-CNTs (carbon nanotubes) nanocomposite has been investigated. The hydrothermal technique was used for synthesis of NiS and NiS/CNTs nanocomposite. Structural elucidation of NiS and NiS/CNTs nanocomposite was conducted by X-ray diffraction (XRD) and Fourier transform infra-red (FTIR) techniques. These characterization techniques verified the formation and purity of samples as extra peaks of impurities were not observed in the obtained data. Scherer formula was used to examine the crystallite size of NiS NPs and NiS/CNTs reported that 9.5 nm and 10.2 nm are sizes of NiS and NiS/CNTs respectively. Scanning electron microscopic (SEM) analysis revealed the reduction in the aggregation of NiS and improved the surface area to assist the redox reactions due to presence of CNTs. Current-voltage (I-V) measurements studied the electrical behaviour of photocatalysts. Optical measurements of synthesized samples were analysed by UV-Visible spectrophotometry. The improvement in bandgap energy of nanocomposite was main reason of excellent photocatalytic activity. About 96% degradation of methylene blue was recorded via NiS/CNTs nanocomposite within 50 min. Photocatalytic performance of nanocomposite is faster than individual metal sulphide due to production of more free radicals, Ni-S-C bond development, surface defects and availability of more reaction sites. These features improved the photocatalytic activity of NiS/CNTs and provide an evidence to use carbon nanotubes for the formation of metal sulphide nanocomposites. Antibacterial property of sample was investigated by four Gram negative bacteria (Proteus vulgaris, Klebsiella pneumonia, Escherichia coli and Pseudomonas aeruginosa) and one Gram positive bacteria (Staphylococcus aureus) at different concentrations using disc diffusion method. The possible mechanism for degradation of Methylene blue under UV-Visible illuminations has been discussed. The upgraded degradation of methylene blue by NiS/CNTs nanocomposite supported that it is promising material for treatment of wastewater.