Additive-free shape-invariant nano-to-micron size-tuning of Cu₂O cubic crystals by square-wave voltammetry

We demonstrate in this study the application of square-wave voltammetry (SWV), an electrochemical technique that has been commonly employed in electroanalysis but much less utilized in electrocrystallization, in the shape-invariant size-tuning of the electrodeposited cuprous oxide (Cu ₂O) crystalline cubic particles from ∼30 nm to 3 μm in aqueous solution under ambient conditions without using any organic surfactant and surface capping agent. We show systematically how each and every adjustable parameter in SWV technique affects the size-tuning of Cu₂O nanocubes under shape invariance. A systematic comparison was made between SWV and several other EC techniques, including linear-sweep voltammetry (LSV), stair-case voltammetry (SCV), chronoamperometry (CA or simple i vs t), square-wave chronoamperometry (SWCA), and differential pulse voltammetry (DPV), for the shape-invariant electrodeposition of crystalline Cu₂O nanocubes. The as-fabricated Cu₂O nanocubes were employed as the size- and shape-controlled galvanic templates to fabricate Cu₂O@Ag core-shell structures which display excellent performance in "single-particle" surface-enhanced Raman spectroscopy (sp-SERS).