Optical Super‐Localisation of Single Nanoparticle Nucleation and Growth in Nanodroplets

Abstract

The formation of metal nanoparticles (NPs) on surfaces by electrodeposition is of significant interest, particularly with a view to understand the early stages of nucleation and growth.Here, the combination of scanning electrochemical cell microscopy (SECCM) and interference reflection microscopy (IRM) is demonstrated to be a compelling approach for real-time monitoring of NP dynamics within the SECCM meniscuselectrode wetted area, through synchronous monitoring in the millisecond range of the electrochemical and optical signatures. Diffraction-limited entities, undergoing phase changes at the electrode substrate, are readily highlighted and tracked in time, including the onset time for the appearance of NPs and their movement over time. The results strongly implicate the rapid formation, surface diffusion and aggregation of smaller entities (not detectable optically) to produce the larger electrodeposited NPs. By applying SECCM tips of different size, it is also possible to understand how the wetted area (meniscus size) plays a key role in the number of NPs formed, with small tip sizes allowing the formation of single NPs. The SECCM-IRM approach is expected to be a powerful platform for the study of myriad phase-formation processes at the nanoscale, particularly by drawing on the possibility of making hundreds or thousands of measurements in fresh surface locations through SECCM technology.

Evaluating Analytical Expressions for Scanning Electrochemical Cell Microscopy (SECCM)

“…Sequentially positioning the nanopipette at an array of points across the substrate surface and performing an electrochemical characterization at each point creates a nanoscale electrochemical map. SECCM is used to quantify reactions and processes at a wide variety of electrochemical interfaces with nanoscale spatial resolution, − including corrosion, − phase formation, − surface defect detection, − battery materials, − and electrocatalytic reactions (e.g., hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, etc.) on single particles. − …”

Imaging the Footprint of Nanoscale Electrochemical Reactions for Assessing Synergistic Hydrogen Evolution

“…Electrodeposition offers several advantages compared to chemical synthesis: in addition to guaranteeing a good electrical contact between the NPs and the substrate, [34] it can produce NPs with a wide range of sizes, allowing for the screening of size‐dependent electrochemistry at the single NP level [35, 36] . Moreover, optical microscopy allows an in situ monitoring of the NPs’ growth [37–39] …”

“…[35,36] Moreover, optical microscopy allows an in situ monitoring of the NPs' growth. [37][38][39] The surface confined by a miniaturized electrochemical cell containing a Ni 2 + solution is subjected to HER by applying a negative potential bias cycle in a cyclic voltammetry (CV) experiment (Figure 1c) while optical images of the surface are continuously acquired under optical microscopy observation in a reflection mode at 20 Hz by a CMOS camera.…”

Antimicrobial effects of silver nanoparticle-microspots on the mechanical properties of single bacteria

“…29 The pipette itself does not come into contact with, or affect, the surface, rendering it a non-contact technique. In comparison to other micro-spotting techniques, 30 SECCM, and in general SPM techniques, have already shown their capacity for the potential-controlled patterned electrodeposition of polymers 31,32 and micro-and nano-metre structures [33][34][35][36][37][38][39][40][41] on a variety of substrates.…”