Electroanalytical Understanding of Metal Nanoparticle Growth Chemistry and Sythesis Design 3 views

The many applications of metal nanoparticles with well-controlled shaped structures and compositions, ranging from sensing to heterogenous catalysis, require reproducible routes for their synthesis. Despite significant synthetic work in this area, a limited picture of the fundamental growth mechanisms underlying shaped metal nanoparticle synthesis presently exists, limiting the ability to troubleshoot synthetic irreproducibility and to predictively design new syntheses. Mechanistic understanding is particularly restricted by the low number of widely applicable time-resolved tools for studying the chemistry of metal nanoparticle growth solutions. This dissertation establishes open-circuit potential (OCP) measurements of the mixed solution potential of colloidal metal nanoparticle growth solutions as a technique to fill the need for real time, in situ methods for characterizing the chemistry of faceted metal nanoparticle growth. Chapter One describes the state of the art in using OCP measurements to troubleshoot synthetic irreproducibility; observe, in real time, nanoparticle growth mechanisms; and inform design of new synthetic approaches, including using OCP measurements to design electrodeposition synthesis for metal nanoparticles inspired by colloidal synthesis design. Chapter Two further develops the previous state of the field in “colloidal-inspired” electrodeposition synthesis of metal nanoparticles. Chapter Three demonstrates the use of OCP measurements to facilitate simplified troubleshooting of synthetic reproducibility issues involving a novel synthesis for palladium (Pd) tetrahexahedra (THH), revealing initial relationships between the mixed solution potential and nanoparticle growth kinetics. This work additionally develops a translation of the colloidal synthesis for Pd THH to electrodeposition. Chapter Four pioneers approaches for deconvoluting the mechanistic information contained within OCP measurements of nanoparticle growth, providing a facile method to distinguish between surface passivation and kinetic shape control mechanisms, homogeneously- and heterogeneously-nucleated (seeded) nanoparticle growth, and changes in the mixed potential due to particle growth versus side reactions (reducing agent degradation in water). Additionally, further exploration of the Pd THH synthesis via OCP measurements and orthogonal time-resolved techniques reveals the complex kinetics of this growth reaction and provides new insight into the importance of early reagent diffusion to the seed surface in setting the correct reducing environment for faceted shape development, even when shape does not emerge until later in the growth process. Chapter Five introduces an inexpensive method for taking reliable OCP measurements of Pd, gold (Au), silver-gold ((Ag)Au), and copper (Cu) growth reactions using commercially-available oxidation-reduction potential (ORP) sensors, demonstrating the ability to make mechanistic determinations and troubleshoot synthetic reproducibility issues in (Ag)Au nanoparticle synthesis using even this more simple measurement system. This work additionally reveals fundamental information about the effects of electrode materials and surface treatment on the measured OCP. Chapter Six introduces a “colloidal inspired” electrodeposition synthesis of dilute bimetallic (Ag)Au nanoparticles with shape controlled by surface deposition of Ag, synthesizing insights from Chapters Three and Four about translation from colloidal to electrodeposition growth and the importance of finely tuning reagent diffusion to achieve ideal growth kinetics and morphology. Optimization of this electrodeposition synthesis uncovers fundamental synthetic handles for controlling reagent concentrations near the electrode surface, revealing new possibilities for the electrodeposition synthesis of complex multimetallic shaped materials. As a whole, the work presented in this dissertation represents a significant advance in the electroanalytical information which can be easily obtained and interpreted during metal nanoparticle synthesis, allowing for specific understanding of nanoparticle growth mechanisms and the harnessing of that mechanistic understanding for rational materials design.

PHD (Doctor of Philosophy)

Metal Nanoparticles; Electrochemistry

English

2026-07-24