Exploring the visible light driven photocatalysis by reduced graphene oxide supported Ppy/CdS nanocomposites for the degradation of organic pollutants

Photocatalytic behavior for removal of methylene blue from aqueous solutions via nanocomposites based on Gd2O3/CdS and cellulose acetate nanofibers

Efficient cleaning of contaminated water by photocatalysis has become an effective strategy in recent years due to its environmental and ecological designation. Cadmium sulfate (CdS) is an excellent photocatalyst in the visible region but has low quantum efficiency. In order to increase the photocatalytic efficiency, CdS was modified with gadolinium oxide (Gd2O3) and combined with graphene oxide (GO) nanoparticles. The estimated crystallite size (Ds) for Gd2O3, CdS/Gd2O3, and CdS/Gd2O3@GO was 29.6, 11.6, and 11.5 nm, respectively. The degradation of methylene blue (MB) reaches the highest values after 60 min under visible light irradiation with a dye concentration of (0.25 ppm). Whereas in powdered composition the efficiency of dye removal has been enhanced under UV irradiation, it reduced by increasing the MB concentration to 0.50 ppm with visible light irradiation. In addition, the CdS with/without Gd2O3 and GO were integrated into electrospun nanofibrous cellulose acetate (CA) through the electrospinning technique. The compounds of Gd2O3, CdS/Gd2O3, and CdS/Gd2O3/GO were encapsulated into CA nanofibers for the degradation of MB under visible and UV irradiation. The apparent rate constant (k) achieves a value of 0.006, 0.007, and 0.0013 min-1 while the removal efficiency reaches 41.02%, 54.71%, and 71.42% for Gd2O3@CA, CdS/Gd2O3@CA, and CdS/Gd2O3/GO@CA, respectively, after 60 min under UV irradiation.

Synthesis and antibacterial activity of nanoenhanced conjugate of Ag-doped ZnO nanorods with graphene oxide

In this paper, we report a successful synthesis of ZnO nanorods using the microwave-assisted technique, solid-state reaction method was utilized for the preparation of Zn_1-xAg_xO (x = 0.05, 0.1), Hummer's modified method for graphene oxide (GO) along with the sonication method to prepare GO-based Ag-doped ZnO (Zn_1-xAg_xO/GO: x  = 0.05, 0.1) nanocomposites. These nanorods and nanocomposites were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FTIR), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy for structural properties, scanning electron microscopy (SEM) along with energy dispersive X-ray (EDX) spectroscopy for morphological analysis, and UV-Vis spectroscopy for optical properties. XRD, FTIR, and Raman measurements substantiated that each sample is well crystallized in the single-phase polycrystalline wurtzite hexagonal structure of ZnO. The average crystallite size is found to be in decreasing order ranges 40 nm to 29 nm, respectively, along with a significant reduction in the optical bandgap. The SEM images showed a clear evidence of nanorods of ZnO, while the EDX spectra verified the presence of Zn, Ag, O, and C elements in the synthesized samples with their nominal percentage. Furthermore, the prepared nanocomposites effectively inhibited the growth ofStaphylococcus aureus and Escherichia coli. In comparison to pure ZnO nanorods, GO-based Ag-doped ZnO nanorods showed improved antibacterial activity against both S. aureus and E. coli.

Review elucidating graphene derivatives (GO/rGO) supported metal sulfides based hybrid nanocomposites for efficient photocatalytic dye degradation

Photocatalysis by utilizing semiconductors for the removal of toxic pollutants has gained tremendous interest for remediation purposes. The organic pollutants usually include; pesticides, dyes and other phenolic compounds. An imperative restraint associated with the photocatalytic effectiveness of the catalyst is the rapid recombination of the light generated electrons and holes. The particle agglomeration and electron-hole recombination hinders the rate of pollutant removal. For decades, researchers have used metal-sulfides efficiently for photocatalytic dye degradation. The recent use of hybrid nanomaterials with the combination of graphene derivatives such as graphene oxide and reduced graphene oxide (GO/rGO)-metal sulfide has gained interest. These composites have displayed an impressive upsurge in the photocatalytic activity of materials. The current review describes the various researches on dye photodegradation by employing (GO/rGO)-metal sulfide, exhibiting a boosted potential for photocatalytic dye degradation. A comprehensive study on (CuS, ZnS and CdS)–GO/rGO hybrid composites have been discussed in detail for effective photocatalytic dye degradation in this review. Astonishingly improved dye degradation rates were observed in all these studies employing such hybrid composites. The several studies described in the review highlighted the varying degradation rates based on diverse research parameters and efficacy of graphene derivatives for enhancement of photocatalytic activity.

Biogenic synthesis of a green tea stabilized PPy/SWCNT/CdS nanocomposite and its substantial applications, photocatalytic degradation and rheological behavior

A green tea leaf-derived cadmium sulfide quantum dot-based system containing different weight percentages of single-walled carbon nanotubes (SWCNTs) and polypyrrole, named PSC, was designed via a green method. The photocatalytic degradation of Ponceau BS dye (λ _max 505 nm) in the presence of PSC was measured. PSC with the highest weight percentage of SWCNTs (7-PSC) showed maximum photocatalytic activity, with 94.6% dye degradation in 55 minutes of irradiation time. This significant enhancement was due to the synergism in the intrinsic properties of the parent components. Alongside this, the rheological behavior of the prepared nanomaterial PSC was examined at constant (100 s^-1) and varying shear rate from 0 to 500 s^-1 at a fixed temperature of 25 °C for a specified volume percentage of 0.1% using Castrol class: 15W-40 engine oil as a base fluid. The objective of lowering the viscosity of engine oil by 98.9% (initial: 0.221000 Pa s, final: 0.0022 Pa s.) was achieved by chartering/mixing the prepared PSC nanomaterial into the engine oil. A comparative study of the experimental and simulation outputs implied the high precision of the modeling via a neural network with minute 0.373 average % errors.

Zinc oxide-decorated polypyrrole/chitosan bionanocomposites with enhanced photocatalytic, antibacterial and anticancer performance

A bio-nanocomposite matrix of polypyrrole grafted ZnO/chitosan (Ppy/C/Z) was synthesized via the in situ polymerization of pyrrole with different weight fractions of ZnO. Incorporation of ZnO nanoparticles with polypyrrole enhances the photocatalytic, antibacterial as well as cytotoxic properties of the resultant composite. Characterizations of the synthesized product were performed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and thermal analysis (TGA and DTA). Surface morphology and particle size were determined by SEM and TEM. The elemental composition of the material was studied by EDX coupled with SEM. Electrochemical surface area was calculated from electrochemical double layer capacitance (EDLC) measurements using cyclic voltammetry. The photocatalytic activity of the composite material was tested by monitoring the degradation of reactive orange-16 (RO-16), Coomassie Brilliant Blue R-250 (CBB-R-250) and Methylene Blue (MB) dyes and the composite was found to be an effective catalyst in the presence of a UV light source. Various scavengers were used to detect the reactive species involved in the photocatalytic process. Furthermore, the stability of the photocatalyst was assessed by recycling experiments. Moreover, the Ppy/C/Z bio-nanocomposite shows potential application with anti-bacterial and anti-cancer activity against Gram-positive and Gram-negative bacterial pathogens and human cancer cell lines (HeLa and MCF-7). The experimental data confirm that the bio-nanocomposite of Ppy/C/Z showed excellent anti-bacterial and anti-cancer activity as compared to a pristine polypyrrole and chitosan formulation (Ppy/C). The apoptosis data with varying concentrations of Ppy/C/Z reveal the remarkable activity against these cancer cell lines.

Bio-nanocomposites were synthesized via grafting polypyrrole/ZnO onto chitosan chain for the photodegradation of organic pollutants and biomedical applications.