Dissertations, Theses, and Capstone Projects

Date of Degree

9-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Michael Mirkin

Committee Members

Hiroshi Matsui

Daniel Steingart

Michael Ward

Subject Categories

Analytical Chemistry | Chemistry

Keywords

Electroanalysis, Electrocatalysis, Nanoelectrochemistry, Nanoparticle, SECM

Abstract

The studies of electrochemical processes on the nanoscale have led to a significant progress in understanding of electrochemical mechanisms and characterization of nanomaterials in the fields of energy, catalysis, and biological research. Electrochemical experiments at nanoscale require the fabrication and characterization of nanometer-sized electrochemical probes. The main advantages of the nanoprobes include very fast mass-transfer rate, high signal-to-noise ratio and extremely fine spatial resolution of electrochemical imaging. In the course of my Ph.D. research, different types of electrochemical probes were developed for measuring electron-transfer kinetics, probing single catalytic nanoparticles and sampling ultra-small volume of liquids.

We developed methodologies to fabricate and characterize disk-type platinum nanoelectrodes suitable for determining rapid heterogeneous electron-transfer kinetics and improved the reliability of kinetic measurements by performing steady-state voltammetry in solution containing both oxidized and reduced components of a redox couple. The Pt nanoelectrodes employed as tips in the scanning electrochemical microscope (SECM) were used to probe electrochemical processes at an individual metal nanoparticle. High-resolution topographic images of single nanoparticles were obtained in the feedback mode and their catalytic activities were mapped in the generation/collection mode. It was shown that a current-distance curve can be fitted to the theory to evaluate the size information of a nanoparticle.

Selective chemical vapor deposition (CVD) of carbon into quartz nanopipettes was used to fabricate carbon nanoprobes with controlled geometries. Completely filled carbon nanoelectrodes were employed as a catalytically inert support to probe electron-transfer reactions and electrocatalysis at single nanoparticles. Alternatively, a thin layer of carbon was deposited on the inner wall of a quartz nanopipette for sampling ultra-small volumes of liquids and quantitating the sampled redox species by voltammetry and coulometry.

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