CONSTRUCTING HYBRID NANOSTRUCTURES OUT OF NOBLE METALS AND SEMICONDUCTORS

Abstract

Fabrication of complex hybrid nanostructures with tunable properties is desirable to fulfill functional applications in multidisciplinary areas. Manipulation of pre-designed nanostructure building blocks composed of distinct materials to achieve finite control over crystallinity, morphology, and composition is a major challenge. This dissertation aims to address the topic and create material with new optical properties. Questions explored are: How to realize delicate control on crystallinity of hybrid nanostructures through unconventional synthetic routes? How to achieve precise hybridized nanostructures with designed geometry, topology and composition? How do these features affect optical properties? Specifically, this dissertation contains recent efforts on fabrication and characterization of functional hybrid nanostructures made from metal and semiconducting materials. I first present a critical review of a monocrystalline nonepitaxially grown metallic @ semiconducting core @ shell hybrid nanostructures. This includes a comprehensive description of the novel nonepitaxial synthetic route, emphasizing critical experimental steps, anticipation of challenges, and ending with my perspective. This systematic review should expand knowledge of the newly developed nonepitaxial method and spread technical aspects of the experiments. I then introduce an anisotropically shaped semiconducting nanocrystal with binary alloy composition. The rod-shaped ensemble has exhibited tunable bright band gap fluorescence that is dependent on dimension. This work is the first to achieve binary semiconducting alloy nanocrystals with anisotropic shapes. Interestingly, the electronic behavior within the rod-shaped semiconducting nanocrystals is altered due to gradient element distribution of the binary material, which is of fundamental interest and potential practical importance. Lastly, a core – metallic satellites-styled nanoparticle assembly structure will be discussed. Control over Ag nanoparticles as surrounding satellites in terms of size, shape and quantity is achieved via a facile synthetic route, and a collective electronic (dipole – dipole coupling) behavior within the metallic assembly is observed, and supported by numerical simulation. This work provides a new facile pathway to achieve well-controlled silica – Ag hybrid nanostructures.