A Simple Route to Reduced Graphene Oxide-Draped Nanocomposites with Markedly Enhanced Visible-Light Photocatalytic Performance

Graphene-based photocatalytic nanocomposites used to treat pharmaceutical and personal care product wastewater: A review

Photocatalytic technology has been widely studied by researchers in the field of environmental purification. This technology can not only completely convert organic pollutants into small molecules of CO₂ and H₂O through redox reactions but also remove metal ions and other inorganic substances from water. This article reviews the research progress of graphene-based photocatalytic nanocomposites in the treatment of wastewater. First, we elucidate the basic principles of photocatalysis, the types of graphene-based nanocomposites, and the role of graphene in photocatalysis (e.g., graphene can accelerate the separation of photon-hole pairs and increase the intensity and range of light absorption). Second, the preparation, characterization, and application of composites in wastewater are introduced. We also discuss the kinetic model of the photocatalytic degradation of pollutants. Finally, the enhancement mechanism of graphene in terms of photocatalysis is not completely clear, and graphene-based photocatalysts with high catalytic efficiency, low cost, and large-scale production have not yet appeared, so there is an urgent need for more extensive and in-depth research.

Metal-Based Nanocomposite Materials for Efficient Photocatalytic Degradation of Phenanthrene from Aqueous Solutions

Polycyclic aromatic hydrocarbons (PAHs) are a class of naturally occurring chemicals resulting from the insufficient combustion of fossil fuels. Among the PAHs, phenanthrene is one of the most studied compounds in the marine ecosystems. The damaging effects of phenanthrene on the environment are increasing day by day globally. To lessen its effect on the environment, it is essential to remove phenanthrene from the water resources in particular and the environment in general through advanced treatment methods such as photocatalytic degradation with high-performance characteristics and low cost. Therefore, the combination of metals or amalgamation of bimetallic oxides as an efficient photocatalyst demonstrated its propitiousness for the degradation of phenanthrene from aqueous solutions. Here, we reviewed the different nanocomposite materials as a photocatalyst, the mechanism and reactions to the treatment of phenanthrene, as well as the influence of other variables on the rate of phenanthrene degradation.

A Codoped Polymeric Photocatalyst with Prolonged Carrier Lifetime and Extended Spectral Response up to 600 nm for Enhanced Hydrogen Evolution

The intrinsic properties of photocatalysts, such as electron state and energy band structure, contribute significantly to their catalytic performance. However, it is difficult to alter these properties of semiconductors by conventional modifications. To adjust the intrinsic properties while preserving long-term conjugation of the polymeric photocatalysts, a post-thermal treatment is proposed to codope P and Na into polymeric carbon nitride in this work. After codoping, the absorption of visible irradiation is strongly extended up to 639 nm. Additionally, the lifetime of charge carriers is almost tripled from 1.09 to 2.93 ns. The photocatalytic hydrogen evolution performance under visible light is improved to 2032 μmol·h^-1 g^-1 in the optimized sample, corresponding to apparent quantum efficiencies of 6.79% and 0.09% at 420 and 600 nm, respectively. The enhanced catalytic activity is ascribed to the synergistic effects of prolonged lifetime and increased charge density that resulted from lattice distortion and extended visible utilization due to the formation of subgap state. Our work provides new pathways for the modification of polymeric catalysts toward high-performance and full-spectrum photocatalysis.

Improving Field Electron Emission Properties of ZnO Nanosheets with Ag Nanoparticles Adsorbed by Photochemical Method

Zinc oxide is a low cost and practical II-VI chemical material, which is utilized to absorb silver (Ag) nanoparticles (NPs) on zinc oxide nanosheets (ZnO NSs). Using the Ag NP-decorated ZnO NSs can improve the electrical characteristics of zinc oxide. Field electron emission characteristics of ZnO NSs and Ag-ZnO NSs indicate the turn-on fields were 5.3 and 3.2 V/μm in the dark, whereas the turn-on field were 4.3 and 2 V/μm under UV light, respectively. In addition, the field electron emission characteristics of ZnO NSs and Ag-ZnO NSs indicate the enhanced field enhancement factors were 3002 and 3420 in the dark and 3276 and 4815 under UV light, respectively.

Tuning the Bandgap of Photo-Sensitive Polydopamine/Ag3PO4/Graphene Oxide Coating for Rapid, Noninvasive Disinfection of Implants

Bacterial infection and associated complications are threats to human health especially when biofilms form on biomedical devices and artificial implants. Herein, a hybrid polydopamine (PDA)/Ag3PO4/graphene oxide (GO) coating is designed and constructed to achieve rapid bacteria killing and eliminate biofilms in situ. By varying the amount of GO in the hybrid coating, the bandgap can be tuned from 2.52 to 2.0 eV so that irradiation with 660 nm visible light produces bacteria-killing effects synergistically in concert with reactive oxygen species (ROS). GO regulates the release rate of Ag+ to minimize the cytotoxicity while maintaining high antimicrobial activity, and a smaller particle size enhances the yield of ROS. After irradiation with 660 nm visible light for 15 min, the antimicrobial rates of the PDA/Ag3PO4/GO hybrid coating against Escherichia coli and Staphylococcus aureus are 99.53% and 99.66%, respectively. In addition, this hybrid coating can maintain a repeatable and sustained antibacterial efficacy. The released Ag+ and photocatalytic Ag3PO4 produce synergistic antimicrobial effects in which the ROS increases the permeability of the bacterial membranes to increase the probability of Ag+ to enter the cells to kill them together with ROS synergistically.

In situ topotactic fabrication of direct Z-scheme 2D/2D ZnO/ZnxCd1−xS single crystal nanosheet heterojunction for efficient photocatalytic water splitting

The 2D/2D ZnO/Zn_xCd_1−xS single crystal nanosheet heterojunction exhibited high-performance hydrogen production activity.

Ordered Single-Crystalline Anatase TiO2 Nanorod Clusters Planted on Graphene for Fast Charge Transfer in Photoelectrochemical Solar Cells

Achieving efficient charge transport is a great challenge in nanostructured TiO₂ -electrode-based photoelectrochemical cells. Inspired by excellent directional charge transport and the well-known electroconductibility of 1D anatase TiO₂ nanostructured materials and graphene, respectively, planting ordered, single-crystalline anatase TiO₂ nanorod clusters on graphene sheets (rGO/ATRCs) via a facial one-pot solvothermal method is reported. The hierarchical rGO/ATRCs nanostructure can serve as an efficient light-harvesting electrode for dye-sensitized solar cells. In addition, the obtained high-crystallinity anatase TiO₂ nanorods in rGO/ATRCs possess a lower density of trap states, thus facilitating diffusion-driven charge transport and suppressing electron recombination. Moreover, the novel architecture significantly enhances the trap-free charge diffusion coefficient, which contributes to superior electron mobility properties. By virtue of more efficient charge transport and higher energy conversion efficiency, the rGO/ATRCs developed in this work show significant advantages over conventional rGO-TiO₂ nanoparticle counterparts in photoelectrochemical cells.

Reduced graphene oxide wrapped on microfiber and its light-control-light characteristics

Reduced graphene oxide (rGO) sheet wrapped on the tapered region of microfiber is demonstrated to enhance the interaction between rGO and strong evanescent field of optical fiber. The 405 nm and 980 nm lasers are employed to illuminate the rGO to investigate the response characteristics of the optical transmitted power (λ = 1550 nm) in the MF. The transmitted optical power of the MF with rGO changes with ~1.7 dB relative variation when the violet light is ranging from 0 mW to 12 mW (~0.21dB/mW) in the outside-pumped experiment. And in the inside-pumped experiment, the change of the 980 nm laser power from 0 mW to 156.5 mW makes ~6 dB relative variation power of the transmitted optical powers of the MF with rGO. These results indicate the optical transmitted power of the MF with wrapped rGO can be manipulated by the 405 and 980 nm light (order of mW), which signifies the device can potentially be applied as all optically and versatilely controllable devices.