Photoluminescence studies of monolayer protected gold, silver, and alloy nanoparticles.

摘要

This dissertation describes work done to understand luminescence properties and the corresponding controls of monolayer protected gold, silver or alloy core clusters (MPCs).; Chapter 1 introduces the luminescence properties of MPCs and theories underline the mechanism of the light emission properties of metallic core nanoparticles.; Chapter 2 outlines the synthesis, and characterization of water soluble gold MPCs, the luminescence properties of four different thiolates protected water soluble gold MPCs respectively, as well as those of several different core sized tiopronin protected gold MPCs.; Chapter 3 describes the luminescence quenching properties of the tiopronin protected gold MPCs. The tiopronin protected gold MPCs exert energy transfer quenching by both dynamic quenching and by static quenching in electrostatic complexes formed between [Ru(bpy)₃]2+ and the tiopronin carboxylate groups. MPCs with average Au core diameters of 2.2 nm exhibited quenching constants that are 20-fold larger than those for 1.8 nm diameter.; Chapter 4 describes the synthesis and characterization of water-soluble tiopronin protected silver MPCs. Water-soluble tiopronin protected silver MPCs, with 1.6nm average diameter cores, exhibit visible luminescence at 500 nm with a quantum yield estimated near 10−4 when excited at 400 nm. Atoms in the Ag MPC core can be replaced by Au atoms using a galvanic metal exchange reaction between the silver clusters and Au(I)[SCH₂(C ₆H₄)C(CH₃)₃].; Chapter 5 continues to study the mechanism of the core atom exchange reaction between the silver nanoparticles and Au(I)[SCH₂(C ₆H₄)C(CH₃)₃]. Both the kinetics and the equilibrium are discussed. The results show that the exchange reaction mechanism is about one Au(I)[SCH₂(C₆H₄)C(CH ₃)₃] exchanges with one silver atom on the surface of MPC. And the luminescence is mostly from the radiative decays of excited metallic atoms on the surfaces of MPCs.