Electrochemical Detection and Sizing of Colloidal ZnO Nanoparticles

Abstract

We demonstrate the controlled reduction of colloidal ZnO nanoparticles (NPs) on a Hg ultramicroelectrode (UME) and its application to determine the redox potential for the deoxygenation of ZnO. The NPs are in colloidal suspension in acetonitrile (MeCN) and reach the electrode by migrational mass transport. At the electrode surface, the Zn 2+ in zinc oxide NPs is reduced to a Zn(Hg) amalgam. The redissolution (stripping) of Zn 2+ from the amalgam into MeCN is used to determine the amount of reduced ZnO. The stripping charge is proportional to the concentration of the colloidal ZnO NPs at potentials where the reduction is found to be limited by mass transport. The charge resulting from the reduction of ZnO is a function of the reduction potential and presents a sigmoidal curve that fits a quasireversible model and is used to determine the formal reduction potential, E 0 ′.We observed that E 0 ′ is a strong function of NP size in the size regime of 11−80 nm in diameter. The ZnO particles studied are more stable than the Zn(Hg) amalgam, but smaller NPs are less stable compared to larger particles, making smaller NPs relatively easier to reduce. The reduction potential of ZnO NPs is a strong function of 1/r. This Kelvin effect is analogous to the electrochemical behavior of metal nanoparticles described by Plieth's model.

Stochastic Collision Nanoelectrochemistry: A Review of Recent Developments

“…As a convenient and rapid strategy, SCNEC has broad applications in many areas, including electrocatalysis, bioelectrochemistry, and biosensing . Moreover, a key finding has shown that SCNEC is particularly powerful for obtaining the properties of single nanoparticles (SNPs), such as the particle size, concentration, aggregation, and catalytic reactivity, by using electrochemical signals.…”

“…The electrochemical behavior of NPs mainly depends on their composition, diameter, and geometry. Metal and metal oxide NPs have been widely used by researchers in SCNEC studies over the past decade . Currently, “soft particles” (SPs) offer a promising new trend in SCNEC research, which has tremendously expanded the application of SCNEC in the area of interface‐transfer analysis, immuno‐detection, and single bio‐particle monitoring …”

Reduction Kinetics and Mass Transport of ZnO Single Entities on a Hg Ultramicroelectrode

“…For the supported system, we did not obtain a linearly increasing calibration curve, so we focused our analysis on the unsupported system. The concentration dependence studies confirm the stripping peaks around −1.5 V are due to the oxidation of Zn(Hg) . The stripping voltammogram is obtained immediately after the preconcentration step of 40 nM ZnO colloids for a time of 1800 s. Figure a and b show a zoom‐in of the spikes in the i ‐t transients for the unsupported and supported suspensions, respectively.…”

Electrochemical analysis of single particles

“…CeO2 NP [62] Pt UME 颗粒的抗氧化活性 CeO2 还 原 ZnO NP [63] Hg UME 尺 寸 分 布 ZnO 还 原 MoS2, WS2, MoSe2, WSe2 NP [45] SPE 尺寸分布; 颗粒双功能表现评估 MoS2, WS2, MoSe2, WSe2氧化…”