An Overview on Graphene-Metal Oxide Semiconductor Nanocomposite: A Promising Platform for Visible Light Photocatalytic Activity for the Treatment of Various Pollutants in Aqueous Medium

Synergistic effect of silver nanoclusters and graphene oxide on visible light-driven oxidase-like activity: Construction of a sustainable nanozyme for total antioxidant capacity detection

The high cost and low reusability of natural enzymes greatly limit their application in biosensing. In this work, a sustainable nanozyme with light-driven oxidase-like activity was fabricated by integrating protein-capped silver nanoclusters (AgNCs) with graphene oxide (GO) through multiple non-covalent interactions. The prepared AgNCs/GO nanozyme could effectively catalyze the oxidation of various chromogenic substrates by activating dissolved O₂ to reactive oxygen species under visible light irradiation. Moreover, the oxidase-like activity of AgNCs/GO could be well controlled by switching on and off the visible light source. Compared with natural peroxidase and most of other oxidase-mimicking nanozymes, AgNCs/GO possessed improved catalytic activity owing to the synergistic effect between AgNCs and GO. More importantly, AgNCs/GO showed outstanding stability against precipitation, pH (2.0-8.0), temperature (10-80 °C), and storage and could be reused at least 6 cycles without obvious loss in catalytic activity. On this basis, AgNCs/GO nanozyme was used to develop a colorimetric assay for the determination of total antioxidant capacity in human serum, which had the merits of high sensitivity, low cost, and good safety. This work holds a promising prospect in developing sustainable nanozymes for biosensing and clinical diagnosis.

Green synthesis of graphene-based metal nanocomposite for electro and photocatalytic activity; recent advancement and future prospective

The presence of pollutants in waste water is a demanding problem for human health. Investigations have been allocated to study the adsorptive behavior of graphene-based materials to remove pollutants from wastewater. Graphene (GO) due to its hydrophilicity, high surface area, and oxygenated functional groups, is an effective adsorbent for the removal of dyes and heavy metals from water. The disclosure of green synthesis opened the gateway for the economic productive methods. This article reveals the fabrication of graphene-based composite from aloe vera extract using a green method. The proposed mechanism of GO reduction via plant extract has also been mentioned in this work. The mechanism associated with the removal of dyes and heavy metals by graphene-based adsorbents and absorptive capacities of heavy metals has been discussed in detail. The toxicity of heavy metals has also been mentioned here. The Polyaromatic resonating system of GO develops significant π-π interactions with dyes whose base form comprises principally oxygenated functional groups. This review article illustrates a literature survey by classifying graphene-based composite with a global market value from 2010 to 2025 and also depicts a comparative study between green and chemical reduction methods. It presents state of art for the fabrication of GO with novel adsorbents such as metal, polymer, metal oxide and elastomers-based nanocomposites for the removal of pollutants. The current progress in the applications of graphene-based composites in antimicrobial, anticancer, drug delivery, and removal of dyes with photocatalytic efficacy of 73% is explored in this work. It gives a coherent overview of the green synthesis of graphene-based composite, various prospective for the fabrication of graphene, and their biotoxicity.

Fabrication of Novel Heterostructure-Functionalized Graphene-Based TiO2-Sr-Hexaferrite Photocatalyst for Environmental Remediation

Novel visible-light photocatalyst (titanium-dioxide-functionalized graphene/strontium-hexaferrites) TiO₂-FG/Sr-hexaferrite nanocomposites were fabricated using a simple hydrothermal technique. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), Raman spectroscopic analysis, and atomic force microscopy were used to analyze the composites as prepared. The unique TiO₂-FG/Sr-hexaferrite-based composite catalyst reveals superior photocatalytic properties for the disintegration of organic dyes methylene blue (MB) and rhodamine B (Rh. B) under visible-light irradiation. The result showed that the functionalized graphene with ternary structure improved the catalytic behavior of the composite due to the synergistic effect of the TiO₂-FG boosted by the graphene surface to provide a fast conducting path to the photogenerated charge carrier. The markedly high photocatalytic behavior has been ascribed to the formation of the ternary structure between TiO₂, FG, and Sr-hexaferrites through interface interaction. The prepared photocatalyst composite exhibited better recyclability, which further confirms its future uses as a photocatalyst in industrial waste products.

Boosting Photocatalytic Activity Using Reduced Graphene Oxide (RGO)/Semiconductor Nanocomposites: Issues and Future Scope

Semiconductor nanoparticles are promising materials for light-driven processes such as solar-fuel generation, photocatalytic pollutant remediation, and solar-to-electricity conversion. Effective application of these materials alongside light can assist in reducing the dependence on fossil-fuel driven processes and aid in resolving critical environmental issues. However, severe recombination of the photogenerated charge-carriers is a persistent bottleneck in several semiconductors, particularly those that contain multiple cations. This issue typically manifests in the form of reduced lifetime of the photoexcited electrons-holes leading to a decrease in the quantum efficiency of various light-driven applications. On the other hand, semiconducting oxides or sulfides, coupled with reduced graphene oxide (RGO), have drawn a considerable interest recently, partly because of the RGO enhancing charge separation and transportation through its honeycomb sp² network structure. High electron mobility, conductivity, surface area, and cost-effectiveness are the hallmark of the RGO. This Mini-Review focuses on (1) examining the approach to the integration of RGO with semiconductors to produce binary nanocomposites; (2) insights into the microstructure interface, which plays a critical role in leveraging charge transport; (3) key examples of RGO composites with oxide and sulfide semiconductors with photocatalysis as application; and (4) strategies that have to be pursued to fully leverage the benefit of RGO in RGO/semiconductors to attain high photocatalytic activity for a sustainable future. This Mini-Review focuses on areas requiring additional exploration to fully understand the interfacial science of RGO and semiconductor, for clarity regarding the interfacial stability between RGO and the semiconductor, electronic coupling at the heterojunction, and morphological properties of the nanocomposites. We believe that this Mini-Review will assist with streamlining new directions toward the fabrication of RGO/semiconductor nanocomposites with higher photocatalytic activity for solar-driven multifunctional applications.