Fabrication of effective photocatalyst using semiconductors and graphene or reduced graphene oxide has been regarded as one of the most promising task to attenuate the environmental pollution. This paper reports the synthesis of different nanocomposites of reduced graphene oxide-cadmium sulfide (RGO-CdS) with varying weight ratio of RGO by simple reflux condensation reaction, during which the reduction of graphene oxide (GO) and formation of CdS nanoparticles occur simultaneously. The combination of CdS nanoparticles (NPs) with the optimum amount of RGO gives a noticeable effect on the properties of the synthesized hybrid nanocomposites, such as enhanced optical, photocatalytic properties. The microscopic studies proved that with the increasing RGO content in the nanocomposites, the particle size decreases and got different shapes. These nanocomposites have been investigated separately as nanocatalyst for the reduction of Cr(VI) to Cr(III) in the presence of visible light irradiation and the catalytic activity depends on the pH of the medium and also the particle size of the CdS NPs which are supported by the band gap energy derived from Tauc's equation. The significant increase in photocatalytic performance of the RGO-CdS nanocomposite was attributed to high electron conductivity of the CdS NPs and RGO surface which facilitates charge separation and prolongs the lifetime of photogenerated electron-hole pairs by decreasing the recombination rate. Antibacterial and antiprotozoal activities have been investigated to determine the efficiency of these RGO-CdS nanocomposites on different bacterial and protozoan strains.

Synthetic dyes emerging from wastewater effluents result in a hazardous environment to our society, hence removal of these dye molecules from the water bodies is necessary due to their toxic nature for living beings. In our study, a straightforward one pot synthetic process is conducted to synthesize reduced graphene oxide (RGO) using Averrhoa carambola fruit extract. To confirm the formation of RGO, different characterization techniques such as Fourier transform infrared spectroscopy (FTIR), UV–Vis spectroscopy and X-Ray Diffraction (XRD) are investigated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to understand the morphology of RGO. Adsorption kinetics for pseudo-first order and pseudo-second order has been carried out for both dyes. Freundlich and Langmuir adsorption isotherm models were confirmed to describe each of the adsorption ability responses with high correlation coefficients. Maximum adsorption capacities of methylene blue (MB) and crystal violet (CV) on RGO were 52.308 mg g−1 and 31.466 mg g−1 respectively. The adsorption ability of this adsorbent is monitored by recyclability in five subsequent cycles and it is observed that up to 5 cycles, there is no significant decrease in adsorption capability. The present study showed that RGO is highly efficient in removing MB and CV dyes from environmental water bodies. The thermodynamics study for the adsorption phenomena of MB and CV dyes on RGO sheet has been investigated.

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A novel green synthesis of reduced gold-graphene oxide (Au-RGO) nanocomposite was fabricated through simple heating method using Alstonia scholaris ( A .scholaris) bark extract. The synthesized nanocatalyst was characterized by X-ray diffraction (XRD), UV-Visible spectroscopy, Fourier transformed infrared spectroscopy (FT-IR). Transmission electron microscopy (TEM) and size distribution study have been investigated to find the dimension of the gold nanoparticles (Au NPs) grown on reduced graphene oxide (RGO) surface. Subsequently, both the catalytic and photocatalytic performances of this nanocomposite were evaluated by using different organic hazardous dyes and a tentative photocatalytic reaction mechanism was discussed depending on the energy band position. To find the effect on different bacterial strains, antibacterial and antiprotozoal studies have been carried out with this nanocomposite.

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