Structural Modification in Au-MoS2 Quantum Dot Composites for Improved Catalytic Efficiency in p-Nitrophenol Reduction

Abstract

Au-MoS2 quantum dots (QDs) composites are ideal catalysts for a number of reactions, including the reduction of p-nitrophenol (PNP). However, the structural role of Au-MoS2 QDs composites in their catalytic efficiency has never been investigated. In this work, a comparative study is carried out to investigate the catalytic reactivities of a gold nanorod–molybdenum disulfide quantum dots (AuNR-MoS2 QDs) composite and a gold nanosphere–molybdenum disulfide quantum dots (AuNS-MoS2 QDs) composite. In addition, the catalytic reactivities of a gold nanorod (AuNR) and a gold nanosphere (AuNS) are also studied. The catalytic efficiency of the as-prepared composites is then investigated for the reduction of p-nitrophenol, taken as the model reaction. The kinetics of the catalytic reduction of p-nitrophenol reveal that the AuNR-MoS2 QDs composite demonstrates the highest catalytic efficiency, having a rate constant of 0.06 min–1, compared to the AuNS-MoS2 QDs composite, AuNR, and AuNS, having a rate constant of 0.023, 0.021, and 0.008 min–1, respectively. The possible mechanism is also discussed in the paper. Finite difference time domain (FDTD) simulation was carried out to simulate the electric field intensity of the AuNR-MoS2 QDs composite, AuNS-MoS2 QDs composite, AuNR, and AuNS. It is observed that, in general, the electric field intensity increases for the AuNR-MoS2 QDs and AuNS-MoS2 QDs composites when compared with only AuNR and AuNS. Therefore, this study emphasizes understanding the structural role of AuNR-MoS2 QDs and AuNS-MoS2 QDs composites, which is paramount in evaluating the catalytic efficiencies as demonstrated in the reduction of aromatic nitro compounds.