Colloidal Fabrication of Catalytic and Nanophotonic Devices

open_access
Open Access
Author:
Chaturvedi, Neetu
Graduate Program:
Chemical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
January 25, 2011
Committee Members:
Darrell Velegol, Dissertation Advisor/Co-Advisor
Darrell Velegol, Committee Chair/Co-Chair
Michael John Janik, Committee Member
Joan Marie Redwing, Committee Member
Jun Huang, Committee Member
Andrew Zydney, Committee Member
Keywords:
Nanowells
Colloidal Doublets
Colloidal Motors
Bottom-up Assembly Techniques
Colloidal Assembly
Speckled Spheres
Nanodisc
Abstract:
The field of colloidal assembly is opening new opportunities in the development of sensors, microbots and other active “colloidal devices”. Although colloidal particles have been studied for so many years, the concept of assembling nanoscale or microscale particles into small “colloidal devices” is a rather recent development. Top-down or template-assisted methods exist to fabricate colloidal assemblies; however, they are usually quite expensive, complicated, limited to a specific particle size or material, and not scalable to production quantities. In this work, micro- and nano-size colloidal assemblies have been fabricated from precursor colloidal particles using simple, scalable and high-throughput bottom-up assembly techniques which can be adapted to a wide variety of materials. Functional colloidal devices were then created from these assemblies, like self-propelling catalytic motors; nanodisc and nanocusp structures; and surface-patterned structures. Micron-size colloidal particles have been assembled into “doublets” or “trimers” using the “Stimulus-Quench (SQ)” technique and have shown to behave as catalytic motors. The self-propelled motion of these motors has been verified under UV light in the presence of H2O2. A multi-stimulus (H2O2, magnetic field, UV light), triggerable (by UV light) collective motion was observed with magnetic doublets. In addition, a novel fabrication method has been presented to create two types of nanostructures that respond to electric field- nanodisc dimers and nanocusp structures- for photonic applications. This fabrication method, based on the SQ technique and colloidal lithography, is simple, fast, inexpensive and scalable. This dissertation also describes a simple, mask-less, high-throughput nanofabrication method for creating nanowells on a silicon substrate using chemically-reactive colloids. The nanowells were formed on silicon wafer, by localized etching of the wafer from etchant generated by the chemically reactive colloids upon heating. This dissertation comprises many research areas including: colloidal assembly, polymer and metal particle synthesis, catalyst chemistry, nanofabrication methods, colloidal lithography, plasmonics, anisotropic etching, and several analytical and characterization techniques.

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