Colloidal Synthesis of Gold-noble Metal Dichalcogenide Heterostructures for Surface-enhanced Raman Scattering and Electrocatalysis 

Abstract

Noble metal dichalcogenides are distinguished from the TMDs by their unique properties. For instance, platinum diselenide (PtSe₂) exhibits the low-energy difference between different polymorphs, layer-dependent electrical properties, and catalytic properties. Another example is that ruthenium diselenide (RuSe₂) with the 1T/2H phase showed superior HER activity in alkaline electrolytes, but the low phase purity made it difficult to establish a clear structure-property relationship. The wet chemical synthesis method is rapid and mild, which is beneficial for constructing heterostructures and discovering unknown structures and properties. However, the colloidal synthesis methods of noble metal dichalcogenides are relatively uninvestigated. Recently, it was discovered that the Au template could interact with the TMDs during the wet chemical synthesis process and stabilize unconventional phases of TMDs, which may also be applied in the synthesis of noble metal dichalcogenides.

This thesis aims to complete the wet-chemical preparation of gold-platinum diselenide (Au-PtSe₂) and gold-ruthenium diselenide (Au-RuSe₂) heterostructures with high phase purity, tune the parameters of the growth process, and explore their structure-dependent physicochemical properties using 4H-Au nanowires as templates. The study of the colloidal synthesis of the noble metal dichalcogenides could open up new frontiers in this field.

In particular, the thesis will be divided into three parts, which are listed below. In part 1, the Au@PtSe₂ with a well-defined structure was successfully prepared using the colloidal synthesis method. As a proof-of-concept application, the Au-PtSe₂ heterostructures with different layer numbers were used for SERS detection of Rhodamine 6G, methylene blue, and crystal violet.

In part 2, the 4H-Au@PtSe₂ heterostructure with multilayers was synthesized and applied as a catalyst for the HER. In part 3, this wet-chemical synthesis strategy was used to prepare Au-RuSe₂ heterostructures. The RuSe₂ exhibited the pure 1T phase when growing on the Au template, while mixed 1T and 2H phases could be obtained without the Au template. Owing to the metallic nature of 1T-RuSe₂, this heterostructure can serve as a potential SERS substrate with good performance.

Date of Award	15 Sept 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Hua ZHANG (Supervisor)