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The wastewater released from industries contains many harmful materials like organic dyes and toxic metal ions which badly affect our environment. Nanotechnology is one of the unique approaches to reducing these chemicals. In current research work monometallic ZnO and Co-ZnO bimetallic NPs were synthesized from Brassica rapa leave’s extract and then these were employed for the elimination of methylene blue (MB) and metal ions of Cu (II). Characterization was done by several analytical techniques such as EDX, FTIR, UV–Visible spectroscopy, SEM and XRD. The average diameter of ZnO and Co-ZnO BMNPs was found to be 32.94 nm and 13.82 nm assessed by XRD analysis. The SEM investigation revealed that the produced NPs had a spherical shape. Three distinct methods have opted to determine the antioxidant potential of synthesized NPs. Different factors like pH, contact time, NPs conc., dye conc. and temperature were studied for the elimination of dye while for the eradication of Cu (II) ions; pH, contact time, NPs conc. and adsorbate doses were studied. Adsorption isotherm and kinetic studies were employed for MB and Cu (II) ions elimination while thermodynamic studies were also done for the elimination of MB.

In this study, green synthesis of monometallic (Ag) and bimetallic (Ag-Ni) nanoparticles is carried out. UV-Visible spectra illustrated peaks at 463 and 429 nm for monometallic and bimetallic nanoparticles. FTIR spectra analysis revealed the presence of different functional groups. SEM and EDX elaborated on the morphology and indicate the presence of respective elemental peaks. XRD data calculations predicted the size of monometallic and bimetallic to be 42 and 25 nm. In the end, the biosynthesized nanoparticles are used as a spectrophotometric probe for the determination of cupric ions. Different parameters are studied and optimized on a standard aqueous solution. Monometallic nanoparticles showed an optimum response in a slightly alkaline medium within 12.5 min of contact time for 8 μM analyte concentration. While bimetallic nanoparticles attained this target in a shorter contact time with a higher concentration value. Then these optimized conditions are utilized for the determination of cupric ions in real water samples.

Nowadays, for environmental remediation, photocatalytic process involving graphene-based semiconductors is considered a very promising oxidation process for water treatment. In the present study, nanocomposite (Cu/Ni/rGO) has been synthesized by Dypsis lutescens leaf extract. Characterization of the sample was carried out by UV-visible spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Different parameters like contact time, nanocatalyst amount, dye concentration, effect of temperature. and pH factor were optimized to examine the maximum removal efficiency for dyes rhodamine B and alizarine R with and without visible light source. In both cases, i.e., with or without light, maximum removal was observed at 20 mg of nanocatalyst for 5 ppm concentration of both dyes at 45 °C temperature and pH 10 for rhodamine B and pH 4 for alizarine R, respectively with a 20 min contact time. Maximum removal of dyes 93% rhodamine B and 91% alizarine R were observed under a tungsten lamp as compared to without a tungsten lamp, i.e., 78% of RhB and 75% of AR from mixture solution of these dyes. To assess the rate of reaction, spontaneity, and nature of reaction thermodynamics, kinetics and adsorption isotherms were studied. Thermodynamic values indicated that both dyes depicted endothermic and spontaneous degradation processes. Isotherm data fitted best to a Freundlich isotherm, while results of kinetic studies of both dyes followed the pseudo 2nd order kinetic equation. In the end, scavenging radical studies concluded that hydroxyl radicals were the main active specie involved in the photocatalytic degradation process, and regeneration experiments resulted that Cu/Ni/rGO nanocomposites were re-utilized for about four times.

In this work, green synthesized cobalt monometallic and cobalt–zinc bimetallic NPs were prepared by bioreduction of metallic salts with Cymbopogan citratus plant extract. Biosynthesized cobalt nanoparticles (NPs) and cobalt–zinc bimetallic NPs were characterized using diverse techniques such as FTIR, UV-Visible spectroscopy, SEM, XRD, and EDX analyses. UV-visible spectra for green-synthesized cobalt monometallic and cobalt–zinc bimetallic NPs were in the range between 300 to 350 nm, which confirmed the formation of stable monometallic and bimetallic NPs. The average particle size of CoNPs calculated by XRD analysis was found to be 22.77 nm and that of Co-Zn BMNPs was 14.8 nm. Different functional groups in the Cymbopogan citratus plant extract, which served as a reducing and stabilizing agent for NPs, were identified by FTIR spectra. Cobalt NPs and cobalt–zinc bimetallic NPs were used in the evaluation of antioxidant, anti-inflammatory, and dye degradation activity. Green-synthesized cobalt monometallic NPs and cobalt–zinc bimetallic NPs exhibited excellent antioxidant activity with the scavenging of DPPH free radicals. Green synthesized cobalt NPs and cobalt–zinc bimetallic NPs were utilized for the removal of methylene blue (MB) dye. Different parameters such as the effect of temperature, pH, and dye concentration on adsorbent doses were analyzed and optimized. The best dye removal percentage was obtained with Co-Zn BMNPs compared with CoNPs. Cobalt NPs and cobalt–zinc bimetallic NPs did not display good anti-inflammatory activity because of the presence of secondary metabolites which inhibited them to react with proteins.

The demand for clean and sustainable alternative energy resources is linearly increasing day by day due to the prevailing electricity crisis. Small-scale energy harvesting is considered a sustainable way to generate clean energy. Advanced energy solar cells, mainly dye-sensitized solar cells use solar energy and convert it into electrical energy. Similarly, MEMS-based piezoelectric materials are used to convert mechanical energy into electrical energy. For these applications, zinc oxide is considered one of the most suitable materials with high conductive, tunable band gap, and piezoelectric properties. However, altering these properties can be carried out by the addition of metal and other materials. Various research work has been carried out to study the addition of conductive metal as a dopant to alter the properties of zinc oxide. In this study, Strontium has been doped in ZnO to form a nanostructure for application in DSSC and microelectromechanical systems (MEMS) energy harvesters. Analysis has been conducted using the simulation and fabrication method. The results show that the doping and the pore size of the substrate (Anodic Aluminum oxide membrane) largely affect the output voltage and current. The difference between the simulated and experimental results was less than 1%, which shows the accuracy of the simulation. Tuning of the band gap can be observed by the addition of Sr in the ZnO nanostructure. For microelectromechanical systems energy harvesters, Sr-doped ZnO nanostructures deposited on anodic aluminum oxide show 7.10 mV of voltage and 1.11 uA of current output. The addition of Sr doping in ZnO shows the improvement in the generated current and voltage for the energy harvester and the improvement in overall power conversion efficiency for dyesensitized solar cells. MEMS-based energy harvesting devices and low-cost advanced solar cells are promising to improve the efficiency of energy generation at a small scale. [ABSTRACT FROM AUTHOR]