Green Route for Microwave-Assisted Preparation of AuAg-Alloy-Decorated Graphene Hybrids with Superior 4‑NP Reduction Catalytic Activity

A microwave-assisted green and facile route has been developed to disperse sub-6-nm Au–Ag alloy bimetallic nanoparticles on the surface of partially reduced graphene oxide (PRGO). The properties of the resulting materials were characterized by high-resolution transmission electron microscopy, scanning electron microscopy, EDX line scanning, UV–vis spectroscopy, ICP spectrometry, and X-ray photoelectron spectroscopy. The reduction reaction of 4-nitrophenol (4-NP) was investigated to evaluate the catalytic performance of AuAg–graphene hybrids, and it was found that this unique catalytic system exhibits excellent activity for this reaction. It is hoped that this fast route can be extended to prepare other preferred bimetallic nanoparticle structures with PRGO supports

Lipase Immobilized on Graphene Oxide As Reusable Biocatalyst

Graphene oxide (GO) has shown promising applications as supports for heterogeneous catalysts. This study reports the functionalization of GO by (3-mercaptopropyl) trimethoxysilane to immobilize lipase. The immobilization is carried out by the site-specific covalent binding between thiol groups of lipase and thiolsulfonate groups on modified GO. For the hydrolysis of <i>p</i>-nitrophenylpalmitate, the obtained GO–lipase shows catalytic performance (93.4%) comparable with that of the free lipase, and the reusability after 10 times is 69.9%. Compared with the free lipase, the GO–lipase exhibits good pH, thermal, and storage stability, which are important in practical applications

Catalytic Epoxidation of Olefins with Graphene Oxide Supported Copper (Salen) Complex

Immobilization of metal complexes on solid supports is an efficient approach to remedy the drawbacks of homogeneous catalysis. In this study, an in situ strategy of synthesis and immobilization of a copper (salen) complex onto graphene oxide (GO) support has been developed. To provide the salen ligands, GO was covalently modified with an aminosilane, followed by condensation with salicylaldehyde. The copper (salen) complex was subsequently synthesized and simultaneously immobilized onto the GO surface with a designed tetrahedral chelate structure. The immobilized copper (salen) complex [Cu­(salen)–<i>f</i>–GO] kept the two-dimensional sheetlike character of GO and was demonstrated to be highly effective for the epoxidation of olefins. It could be readily reused for successive twelve times without discernible activity and selectivity deterioration, which displays potential for practical applications

Eosin Y Covalently Anchored on Reduced Graphene Oxide as an Efficient and Recyclable Photocatalyst for the Aerobic Oxidation of α‑Aryl Halogen Derivatives

A visible-light photoredox with homogeneous catalyst-like transition metal complexes and organic dyes shows promising applications in organic synthesis. However, the practical applications of these photocatalysts are hampered by the difficulty of separating and recycling them from the reaction mixtures. In this study, we report the covalent immobilization of Eosin Y on reduced graphene oxide and demonstrate the obtained hybrid can be used as a recyclable photocatalyst with excellent catalytic performances in the aerobic oxidation of α-aryl halogen derivatives

Facet Dependent Activity of Fe(III) Species Modified TiO₂ for Simulated Sunlight Driven Fenton-like Reactions

TiO2 crystals with different exposed facets are synthesized and modified facilely by depositing Fe(III) species. With more (101) facets exposed, the photoactivity of Fe-TiO2 is obviously enhanced with peroxymonosulfate (PMS) as oxidant. The degradation rate for 20 ppm Bisphenol A (BPA) on Fe-TiO2 (101) can achieve 0.219 min–1, ∼8.5 times faster than that of pure TiO2 under simulated sunlight irradiation. Photoelectrochemical measurements and density functional theory (DFT) calculations confirm that the interfacial charge transfer (IFCT) on Fe-TiO2 (101) is stronger than that on Fe-TiO2 (001) and a faster Fe(III)/Fe(II) transformation rate can be therefore achieved. As a result, the generation of ·OH and 1O2 will be accelerated with more (101) facets exposed, thus obtaining better photoactivity. Under the Fe-TiO2/PMS/Light system, BPA can be effectively degraded in a wide pH range or in the presence of multiple inorganic anions. After five cycles, 100% BPA can still be degraded within 60 min. The study provides new photocatalysts design strategy based on Fe(III)/Fe(II) redox for PMS based photocatalytic oxidation

Ethylenediamine Modified Graphene and Its Chemically Responsive Supramolecular Hydrogels

In this study, reduced graphene oxide was functionalized with ethylenediamine (EDA) by a simple one-pot process, using a lithium ethylenediamine derivative as a nucleophilic reagent at 50 °C for 10 h. The presence of EDA chains in graphene was identified by Fourier transform infrared spectroscopy (FTIR), electronic energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS), and zeta potential. By using the simple amidation reaction of EDA modified graphene and subsequent host–guest interactions between β-cyclodextrins (β-CDs) and polymers carrying guest moieties, we also synthesized a new type of graphene-based β-CD supramolecular hydrogels. The obtained hydrogels exhibited the gel-to-sol transition by adding a competitive guest sodium adamantine carboxylate (AdCNa) or competitive host α-CD

Near-Infrared Responsive MoS₂/Poly(<i>N</i>‑isopropylacrylamide) Hydrogels for Remote Light-Controlled Microvalves

To achieve remote control over the swelling/deswelling transition, chemically exfoliated MoS₂ nanosheets with photothermal properties are successfully incorporated into poly­(<i>N</i>-isopropylacrylamide) (PNIPAM) hydrogel by in situ polymerization. Different from the conventional thermal-responsive PNIPAM hydrogel, the MoS₂/PNIPAM composite hydrogel here shows a reversible volumetric change in response to near-infrared (NIR) illumination. Based on this new composite hydrogel, a microfluidic device actuated remotely by NIR laser is also demonstrated

Utilization of MoS₂ Nanosheets To Enhance the Photocatalytic Activity of ZnO for the Aerobic Oxidation of Benzyl Halides under Visible Light

Semiconductors are the low cost and recyclable photocatalysts for visible-light photoredox catalysis, which is one of the prospective ways to convert solar energy to chemical energy in organic synthesis. This study reports a new MoS₂/ZnO composite for the aerobic oxidation of benzyl halides under visible light. Despite the limited intrinsic activity of the ZnO alone, we found that the introduction of a small amount of MoS₂ nanosheets (4 wt %) could significantly improve the catalytic performances of the ZnO in visible-light photoredox catalysis

Phosphotungstic Acid Immobilized on Amine-Grafted Graphene Oxide as Acid/Base Bifunctional Catalyst for One-Pot Tandem Reaction

In this study, phosphotungstic acid immobilized on amine-grafted graphene oxide (GOAP) was prepared successfully by silylanization and electrostatic interaction. The obtained GOAP was characterized by Raman spectroscopy, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), zeta potential measurements, and X-ray photoelectron spectroscopy (XPS). Systematic studies demonstrated that GOAP had excellent catalytic activities and robustness in the one-pot tandem deacetalization–nitroaldol reaction. The key role of the acid/base ratio in the catalytic performance of this bifunctional catalyst was also revealed by preliminary kinetic studies. This bifunctional catalyst might find promising applications in green chemistry, as it can not only reduce costs and waste by saving separation/purification steps and solvents/reagents, but also increase the yield by avoiding the separation of intermediate products

CoP Nanoparticles Combined with WSe₂ Nanosheets: An Efficient Hybrid Catalyst for Electrocatalytic Hydrogen Evolution Reaction

Hydrogen (H₂) is a clean and efficient energy carrier, and great efforts have been focused on developing new non-Pt electrocatalysts for the hydrogen evolution reaction (HER). In this study, CoP/WSe₂ nanosheets hybrids were successfully prepared, and their potential as a new non-noble HER catalyst was evaluated. We found that all the hybrids showed higher catalytic activity than pure CoP and WSe₂ nanosheets, suggesting their synergistic catalytic effect in the HER. Particularly, in 0.5 M H₂SO₄, the hybrid with an optimized CoP-to-WSe₂ mass ratio of 1:1 has the highest current density of 102.9 mA/cm² at 300 mV vs RHE and excellent long-term stability