Electroless Deposition of Single Silver and Silver Oxide Particles and Electrochemical Reconstruction at a Nanopipette Electrode

Abstract We present a method for fabricating single silver oxide and silver particles at the tip of a nanopipette. The silver oxide particle is formed directly at a pipet tip when Tollens’ reagent silver diammine complex-filled pipet is immersed in a strongly alkaline solution. The particle size, shape, and reaction rates are found to be sensitive to the migration of ions driven by electrochemical potential. To form a single particle at the tip, the pipet interior and its tip can be coated with silver via classical silver mirror reaction with dextrose. The metallic silver coating at the tip can be either wired directly to a conductive lead for testing its electrochemical performance or quantified in a wireless/bipolar configuration by having an electrolyte layer inside the pipet. The formation of silver inside the nanopipette and silver oxide at the tip can be observed in such a bipolar electrochemical cell configuration upon electrochemical-potential cycling. Optical microscopy, chronoamperometry, cyclic voltammetry (CV), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) provide complementary evidence for single-particle formation, composition, and stimulus-induced reconstruction. Importantly, this proof of concept establishes a simple and tunable route for controlling the composition and geometry of silver-functionalized tips through reaction conditions and electrochemical bias. Freshly prepared Ag is particularly attractive for probe-based applications because its strong plasmonic response and local electromagnetic field enhancement complement its intrinsic Ag/AgOx electrochemistry. The resulting architecture therefore provides a foundation for tailoring silver-tipped probes toward future dual-modality measurements such as fully integrated scanning electrochemical microscopy (SECM) with tip-enhanced Raman spectroscopy (TERS).