Chemical communication occurs between objects in nature by exchanging chemical messages, including potential energy, ions, molecules, etc. Extensive research has revealed that these communications are primary pathways through which individual particles interact with one another, controlling the physical and chemical process in complex systems. For example, photochemistry has stimulated interest in metallic nanomaterial synthesis, where the chemical communication between nanoparticles (NPs) determines the synthesis pathway and thus the morphology of NPs.Therefore, at the single NP level, in-situ monitoring of chemical communication between NPs is required to advance the fundamental understanding of photochemical synthesis kinetics, allowing the design of nanomaterials for sensing and catalytic applications. Recent developments in stochastic collision electrochemistry suggest its potential to provide insightful profiling of a single NP. The discrete collision of single NPs with a biased ultramicroelectrode (UME) results in a series of time-resolved current responses that are associated with the intrinsic features of individual NPs. Assisted by statistical analysis of high-throughput transient current signals, stochastic collision electrochemistry provides a sufficient resolution for size discrimination of single Ag NPs.
Professor Long’s group focuses on single entity electrochemistry by well-defined confined interface. By virtue of the superior sensitivity of stochastic collision electrochemical measurements, the authors extend this methodology to monitor the morphology evolution of single Ag NPs in photochemical processes in-situ. This method allows to unravel the photoinduced chemical communication between individual Ag NPs. This communication establishes a decision-making nanomaterial synthesis, determining the morphology of Ag NPs.
Figure 1. Schematic of (a) stochastic collision electrochemistry for monitoring interparticle chemical communication in the photochemical process by tracking the morphology evolution of individual Ag NPs under laser irradiation in-situ. (b) A representative transient chronoamperometric response of a single Ag NP electrooxidation during the polarization at +0.600 V vs. Ag/AgCl QRCE on a 12.5 μm diameter Au UME. Q is the total charge per a single current response, rnp is the radius of Ag NPs, M is the molar mass of Ag, F is Faraday constant, and ρ is the density of Ag.
To quantitively investigate the chemical communication between small and large Ag NPs, the integrated charge histograms are also fitted to two Gaussian distributions. Demonstrated that the proportion of two types of events, which indicates a clear correlation between small Ag NPs and large Ag NPs, and they do communicate with each other. Through theoretical deduction, chemical potential difference (Δμ) is a function of the proportion of collision events, and revealing how NP-to-NP interactions affect collective transformation kinetics of Ag NPs. Δμ positively affects the variation of heterogeneity, proving that the heterogeneity of chemical potential of individual Ag NPs is a key factor in the control of photoinduced transformation kinetics. Indicating the whole transformation process consists of two stages, where the fragmentation of Ag NPs is followed by Ostwald ripening.
Figure 2. In-situ monitoring of chemical communication between single Ag NPs by stochastic collision electrochemistry. a) Morphology transformation between small Ag NPs and large Ag NPs as a function of the irradiation time; b) The chemical potential difference (Δμ) between small Ag NPs and large Ag NPs recorded at each of different irradiation time; c) the kinetics of photoinduced transformation of Ag NPs as a function of the irradiation time.
Then, to alter the chemical communication-dependent morphology transformation of Ag NPs by controlling the concentration of Ag+. The experimental results indicate that Ostwald ripening is altered from the second stage to the first one in the photochemical process, which is followed by the fragmentation of Ag NPs. Chemical potential difference is indeed the promoter of interparticle chemical communication, which is affected by the Ag+ thermal diffusion.
Figure 3. Probing the control of chemical communication between Ag NPs. Plots of current amplitude (c), duration time (d), integrated charge (e) at different laser irradiation time for stochastic collision electrochemistry of Ag NPs.
The result proves that stochastic collision electrochemistry could be developed as aqueous electrochemical microscopy to the operando characterization of the morphology evolution of individual NPs, which sheds light on understanding the kinetics of synthesis and material design.
The related paper entitled Monitoring Photoinduced Interparticle Chemical CommunicationIn Situ, was published in Angewandte Chemie International Edition (DOI: 10.1002/anie.202215631, paper link: https://onlinelibrary.wiley.com/doi/10.1002/ange.202215631). This research was supported by the National Natural Science Foundation of China (22206074, 22090051), and the Fundamental Research Funds for the Central Universities (2022300325).