Plasmon-Enhanced Copper Nanodendrites as Dual-Function SERS Substrates and Photoelectrochemical H₂O₂ Sensors

A facile, one-step galvanic replacement route was used to grow hierarchical copper nanodendrites (Cu NDs) directly on aluminum (Al) foil, providing a dual-function plasmonic platform for surface-enhanced Raman scattering (SERS) and enzyme-free photoelectrochemical (PEC) detection of hydrogen peroxide (H₂O₂). The Cu NDs were formed by immersing Al foil in an acidified CuSO₄ solution at room temperature, and their fern-leaf morphology, phase purity, and metallic Cu(0) oxidation state were confirmed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Using 4-mercaptobenzoic acid (4-MBA) as a probe molecule, the Cu NDs/Al foil substrate achieved SERS detection down to 10^-7 M with an approximate enhancement factor of ~10⁶, consistent with strong localized surface plasmon resonance (LSPR)-driven electromagnetic enhancement. Under simulated solar illumination, LSPR-excited hot carriers additionally accelerated the electrocatalytic reduction of H₂O₂, raising the detection sensitivity from 110.6 to 145.3 μA cm^-2 mM^-1 relative to dark conditions. Wavelength- and intensity-dependent photocurrent measurements confirmed that this enhancement tracks the LSPR absorption band of the Cu NDs rather than photothermal heating. These results establish low-cost, earth-abundant Cu nanodendrites as an effective plasmonic platform for combined optical and electrochemical (bio)sensing.