Synthesis of Cu and Cu-based Nanoparticles and Applications in Photocatalysis

Abstract

Copper-based materials are attractive photocatalysts for organic transformations owing to their earth abundance, low cost, and versatile redox properties. However, the intrinsic instability of copper nanoparticles (Cu NPs) under photochemical and oxidative conditions severely limits their practical application. This thesis investigates strategies for stabilising Cu NPs, their performance in representative photocatalytic reactions, and the mechanistic roles of key Cu-based intermediates. Cu-based materials are synthesised via physical vapor deposition, mechanical grinding, galvanic replacement, and wet impregnation, and characterised using SEM, HRTEM, XRD, XPS, UV–Vis, FTIR, and GC–MS. Liquid gallium is identified as an effective stabilisation strategy, where dynamic Cu–Ga interactions suppress aggregation and oxidation, significantly enhancing catalyst stability. Zeolite-supported Cu NPs are further applied to visible-light-driven aerobic oxidation of amines to imines under ambient conditions, achieving high efficiency and selectivity using molecular oxygen as the sole oxidant. In addition, the light-induced behaviour of copper(I) phenylacetylide and copper(I) thiophenolate is examined, demonstrating that these intermediates undergo photooxidation to form CuO nanoparticles under blue light irradiation, indicating their dynamic involvement in photocatalytic processes. Overall, this thesis shows that effective stabilisation strategies combined with mechanistic understanding of Cu intermediates are essential for the rational design of robust and sustainable Cu-based photocatalysts for organic synthesis.