Single-entity electrochemistry mainly focuses on the properties of single nanoscale systems, which provides a new avenue of studying electrochemical processes at the nanoscale rather than in complex ensemble systems. Stochastic collision nanoelectrochemistry (SCNEC), which has emerged as a convenient and fast single-entity electrochemical analysis method, has gone through significant improvements over the past few years. As a powerful tool for the establishment of multiple analytical strategies, SCNEC has broad applications in electrochemical analysis, catalysis, biosensing, and so forth. This technique is especially promising for the rapid analysis of a single entity with respect to size, concentration, aggregation, and kinetic studies. In this Minireview, we summarize the basic principles and experimental techniques of SCNEC and give a brief overview of the cutting-edge developments in SCNEC over the past 3 years.

Gold nanoparticles (AuNPs) have been demonstrated to serve as effective nanomaterial‐based enzyme mimetics (nanozymes) for a number of enzymatic reactions under mild conditions. The intrinsic glucose oxidase and peroxidase activities of single AuNPs and Ag–Au nanohybrids, respectively, were investigated by single NP collision electrochemical measurements. A significantly high turnover number of nanozymes was obtained from individual catalytic events compared with the results from the classical, ensemble‐averaged measurements. The unusual enhancement of catalytic activity of single nanozymes is believed to originate from the high accessible surface area of monodispersed NPs and the high activities of carbon‐supported NPs during single‐particle collision at a carbon ultramicroelectrode. This work introduces a new method for the precise characterization of the intrinsic catalytic activities of nanozymes, giving further insights to the design of high‐efficiency nanomaterial catalysts.

Hydrogen peroxide (H2O2) widely involves in intracellular and intercellular redox signaling pathways, playing a vital role in regulating various physiological events. Nevertheless, current analytical methods for the H2O2 assay are often hindered by relatively long response time, low sensitivity, or self-interference. Herein, a zeolitic imidazolate framework-8 (ZIF-8)-based surface-enhanced Raman scattering (SERS) sensor has been developed to detect H2O2 released from living cells by depositing ZIF-8 over SERS active gold nanoparticles (AuNPs) grafted with H2O2-responsive probe molecules, 2-mercaptohydroquinone. Combining the superior fingerprint identification of SERS and the highly efficient enrichment and selective response of H2O2 by ZIF, the ZIF-8-based SERS sensor exhibits a high anti-interference ability for H2O2 detection, with a limit of detection as low as 0.357 nM. Satisfyingly, owing to the enhanced catalytic activity derived from the successful integration of AuNPs and ZIF, the response time as short as 1 min can be obtained, demonstrating the effectiveness of the SERS sensor for rapid H2O2 detection. Furthermore, the developed SERS sensor enables real-time detection of H2O2 secreted from living cells under phorbol myristate acetate stimulation, as cells can be cultured on-chip. This study will pave the way toward the development of a metal–organic framework-based SERS platform for application in the fields of biosensing and early disease diagnosis associated with H2O2 secretion, thus exhibiting promising potential for future therapies.

We reported a novel method to real-time monitor the redox behaviors of single Ag nanoparticles (AgNPs) at a Au ultramicroelectrode between oxidizing and reducing pulse potentials using the nanocollision electrochemical method. At fast pulse potentials, the instantaneous anodic–cathodic current transients of a single AgNP were observed for the electrooxidation of AgNP, followed by the electroreduction of the newborn silver oxide (AgO) NP in alkaline media via switching of redox potentials; however, only anodic oxidation signals of individual AgNPs were observed in neutral solution. Through this study, we have revealed the substantial different dynamic nanocollision electrochemical behaviors of single AgNPs on the electrode surface in various media. Our study offers a new view for clearly clarifying in situ tracking of the electron-transfer process of single NPs by correlating electrochemical oxidation and reduction behaviors with the complementary information.