Nanostructured Assemblies Based On Metal Colloids And Monolayers: Preparation, Characterisation And Studies Towards Novel Applications

Abstract

Nanoscience dominates virtually every field of science and technology in the 21st century. Nanoparticles are of fundamental interest since they possess unique size- dependent properties (optical, electrical, mechanical, chemical, magnetic etc.), which are quite different from the bulk and the atomic state. Bimetallic nanoparticles are of particular interest since they combine the advantages of the individual monometallic counterparts. The present study focuses on bimetallic nanoparticles containing gold as one of the constituents. Au-Pd, Au-Pt and Au-Ag bimetallic/alloy nanoparticles have been prepared by four different synthetic methods, and characterised by a variety of techniques, with an emphasis on Au-Ag alloy systems in the solution phase as well as in the form of nanostructured films on solid substrates. Au- Ag alloy nanoparticles have been used to demonstrate two different applications. The first is the use of Au-Ag monolayer protected alloy clusters in demonstrating single electron charging events in the solution phase as well as in the dry state. Single electron transfer events involving nanosized particles are being probed extensively due to their potential applications in the field of electronics. The second is an analytical application, involving the use of trisodium citrate capped Au-Ag alloy hydrosols as substrates for surface enhanced Raman and resonance Raman scattering [SE(R)RS] studies. The sols have been used for single molecule detection purposes. Various organic molecules such as quinones, phthalocyanines and methyl violet have been self- assembled in a stepwise manner on the nanoparticulate as well as bulk Au, Ag and Au-Ag surfaces, and characterised extensively by spectroscopic, electrochemical and spectroelectrochemical techniques.