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Synthesis and Transformation of AuCu Intermetallic Nanoparticles

Electronic Theses of Indian Institute of Science

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Field Value
 
Title Synthesis and Transformation of AuCu Intermetallic Nanoparticles
 
Creator Sinha, Shyam Kanta
 
Subject Nanoparticles - Synthesis
Hybrid Nanoparticles
Gold-Copper (Au-Cu) Intermetallic Nanoparticles
Au-Cu Nanoparticles
Au-Cu Nano-Chain Network Structures
Gold-Copper-Sulfur (AuCu2S) Hybrid Nanostructures
Au-Cu Intermetallic Nanoparticles
Au-Cu Bimetallic Nanoparticles
Au-Cu Alloy Nanoparticles
AuCu Nanoparticles
AuCu Bimetallic Nanoparticles
AuCu Alloy Nanoparticles
Alloyed Nanoparticles
Au–Cu System
Materials Science
 
Description Investigations on size dependent phase stability and transformations in isolated nanoparticles have gained momentum in recent times. Size dependent phase stability generates size specific particle microstructure which consequently yields size specific functionality. One important prerequisite for conducting studies on nanoparticles is their synthesis. A substantial amount of research effort has therefore been focused on devising methodologies for synthesizing nanoparticles with controlled shapes and sizes. The present thesis deals with both these two aspects: (a) synthesis of nanoparticles and (b) phase transformations in nanoparticles. The system chosen in this study is AuCu intermetallic nanoparticles. The choice of AuCu nanoparticle was due to the fact that the literature contains abundance of structural and thermodynamic data on Au–Cu system which makes it a model system for investigating size dependence of phase transformations. With respect to synthesis, the present thesis provides methodologies for synthesizing alloyed Au–Cu nanoparticles of different sizes, Au–Cu nano-chain network structures and uniform Au–Cu2S hybrid nanoparticles. For every type, results are obtained from a detailed investigation of their formation mechanisms which are also presented in the thesis. With respect to phase transformation, the thesis presents results on the size dependence of fcc to L10 transformation onset in Au–Cu nanoparticles under isothermal annealing conditions.
The present thesis is divided into eight chapters. A summary of results and key conclusions of work presented in each chapter are as follows. The ‘introduction’ chapter (chapter I) describes the organization of the thesis. Chapter II (literature study) presents a review of the research work reported in the literature on the various methodologies used for synthesizing Au–Cu based nanoparticles of different shapes and sizes and on ordering transformation in AuCu nanoparticles. The chapter also presents a brief discussion on the reaction variables that control the process of nucleation and growth of the nanoparticles in solution. Chapter III titled ‘experimental details and instrumentation’ describes the synthesis procedures that were used for producing various nanoparticles in the present work. The chapter also briefly describes the various characterization techniques that were used to investigate the nanoparticles.
The fourth chapter titled ‘synthesis and mechanistic study of different sizes of AuCu nanoparticles’ provides two different methodologies for synthesis, referred as ‘two-stage process’ and ‘two-step process’ that have been used for producing alloyed AuCu nanoparticles of different sizes (5, 7, 10, 14, 17, 25 nm). The ‘two-stage’ process involved sequential reduction of Au and Cu precursors in a one pot synthesis process. Whereas, the ‘two-step’ process involved a two-pot synthesis in which separately synthesized Au nanoparticles were coated with Cu to generate alloyed AuCu nanoparticles. In the two-stage synthesis process it was observed that by changing the total surfactant-to-metal precursor molar ratio, sizes of the alloyed AuCu nanoparticles can be varied. ‘Total surfactants’ here include equal molar amounts of oleic acid and oleylamine surfactants. Interestingly, it was observed that there exists a limitation with respect to the minimum nanoparticle size that can be achieved by using the two-stage process. The minimum AuCu nanoparticle size achieved using the two-stage synthesis process was 14 nm. Mechanism of formation of AuCu nanoparticles in the two-stage synthesis process was investigated to find out the reason for this size limitation and also to determine how the synthesis process can be engineered to synthesize alloyed AuCu nanoparticles with smaller (
 
Contributor Chattopadhyay, K
 
Date 2018-04-16T14:29:07Z
2018-04-16T14:29:07Z
2018-04-16
2013
 
Type Thesis
 
Identifier http://etd.iisc.ernet.in/2005/3407
http://etd.iisc.ernet.in/abstracts/4273/G25905-Abs.pdf
 
Language en_US
 
Relation G25905