Construction of CdSe-AuPd quantum dot 0D/0D hybrid photocatalysts: charge transfer dynamic study with electrochemical analysis for improved photocatalytic activity.

Abstract

The integration of semiconductor quantum dots and noble metal nanoparticles can efficiently couple numerous effects corresponding to the individual domains of the hybrid system for a variety of applications. Herein, we establish a direct correlation between the electronic band structure and optical band gap of monometallic and bimetallic alloy nanoparticle decorated CdSe quantum dots, which in turn regulate the charge shuttling dynamics in a quantum dot hybrid (QDH) system. Directly coupled Au, Pd, AuPd, and CdSe QDHs were prepared via a simple fabrication technique. The photoluminescence intensity of the QDHs was quenched compared to that of CdSe quantum dots with a maximumally diminished CdSe-AuPd system. Broadening of the absorbance peak along with a blue shift for QDHs confirm the interaction of the energy levels of the QDs and metal domains. AuPd decorated CdSe QDs demonstrate enhanced photocatalytic activity compared to their monometallic counterparts, which has made them interesting catalysts reported for the first time. Lifetime decay measurements, which isolated the individual charge-transfer steps, showed that a maximum amount of photoexcitons can be separated by bimetallic alloy decoration compared to monometallic ones. Cyclic voltammetry results offer insight into the change in the conduction band edge energy position for both monometallic and bimetallic incorporating semiconductor hybrid systems. Our findings reveal that photoexcited semiconductor quantum dots undergo charge equilibration when the QDs are in contact with metallic domains, influencing the shifting of the conduction band energy level of the hybrid to a more negative potential, and this is a maximum for the CdSe-AuPd hybrid, resulting in the best photocatalytic activity. Shuttling of electrons around the conduction band of CdSe and the Fermi level of the metallic domains is the main deciding factor for an efficient photocatalyst hybrid system.