Abstract:
The thesis presents the results of investigations on the preparation,
characterization and organization of metal nanocrystals at the liquid-liquid interface,
and exploring the formation of their mesoscopic assemblies. Section 1 contains a brief
overview of nanocrystals and their mesoscopic organization. Section 2 contains the
scope of investigations as well as the results and discussion. Section 3 covers other
studies undertaken by the candidate.
The Liquid-liquid interface serves as an excellent nanoreactor where the
interaction among the reacting species from the two immiscible layers is confined due
to the interface. Synthesis of nanocrystalline filM.S. of Au, Ag, Pd and Cu metals and
their alloys using the liquid-liquid interface has been carried out by this elegant, yet
simple technique. Control parameters such as type of solvent, solution concentration,
temperature, viscosity and mechanical vibrations-all influence the nanocrystal
formation. Thus, it has been possible to achieve good control over the particle size
and the extent of packing in mesoscopic assemblies. Nanocrystalline Au filM.S. so
prepared have been investigated for their optical and electrical properties. The course
of growth of Au nanocrystalline filM.S. at the interface has been studied using small
angle X-ray scattering. Rheological properties of Ag filM.S. at the interface have also
been examined. Besides monometallic filM.S., nanocrystalline alloy filM.S. of Au-Ag,
Au-Cu and Au-Ag-Cu have been prepared by suitably mixing metal precursors in the
top organic phase. By adding surfactants to either of the layers, the formation of
dendritic structures and fractal assemblies has been observed. The nanocrystalline
filM.S. of Au have been chemically modified by adsorbing thiols of various types, such
as alkane thiols of different chain lengths as well as conjugated dithiols. The modified
filM.S. have been examined for their structural, optical and electrical properties. This
aspect of the study has enabled to understand the dependence of the surface plasmon
band and other characteristics on the interparticle separation. Apart from above
studies, a small electrode system was designed and fabricated to study single
molecular properties using two identical palladium nanocrystals, and scanning
tunneling microscopy to study molecular properties.
