Silver-Based Nanomaterials Through Electrochemical Roughening for Plasmonic Applications

電化學粗糙化製備的銀納米材料及其等離激元應用

Student thesis: Doctoral Thesis

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Award date27 Oct 2023

Abstract

Nanomaterials have been widely used in different fields, including catalysis, sensors, energy storage, and many others. In this thesis, we choose silver-based nanomaterials as our major focus, the controlled fabrication of the nano morphology and their applications in Surface Enhanced Raman Spectroscopy (SERS), as well as the plasmonic related applications. The techniques developed in this thesis are facile and ready for mass-production, which will be important for large-scale applications in the future.

In chapter 2, A one-pot electro-chemical method to fast (~ 2 mins) produce Ag multiple-twinned polyhedron nanocrystals from commercial bulk Ag materials in a nitric acid solution, eliminating any need for surfactants or capping agents were developed. The size of polyhedron nanocrystals can be easily manipulated in an unprecedentedly wide range from 35 to 660 nm. Furthermore, the Ag polyhedrons are directly grown on the Ag substrate, highly desirable for promising applications such as catalysis and plasmonic. Mechanistic studies reveal the concentration of Ag+ in the diffusion layer nearby the surface, controlled by voltage and pulse time, are critical in governing the polyhedron formation (<1.3 mM) and its dimensional adjustability.

In chapter 3, with the mass-produced sliver-based SERS substrate, a potable Raman spectrometer, and a homemade 3D-print holder, we developed a rapid, sensitive, and on-site SERS method for selective detection of ZPT in complex real-world samples, we also unravel that ZPT has the ultra-strong binding capacity with Ag due to the easy formation of Ag-S and Ag-Zn bonds, which explains the high selectivity and sensitivity of our method.

In chapter 4, we monitored the reorientation of PATP molecules on the surfactant-free stable Ag nanomaterial substrates by operando SERS. The Raman features of molecular reorientation are clearly extracted through the protonation of the PATP molecules to suppress the conversion of PATP to DMAB. Additionally, this chapter solves the long-standing puzzle why the conversion to DMAB is suppressed with concentrated PATP: this is because the over-crowded PATP adsorbed on the substrate refrains its own reorientation (similar to the space-steric effect) which is a prerequisite for producing DMAB. To the best of our knowledge, this is the first time that molecular reorientation during PMCRs is in-situ observed using the Raman spectroscopy techniques, offering new insights into the plasmonic catalysis mechanisms.