Pattern-Assisted Pulse Electrochemical Deposition of Ag-Au Alloy Nanoparticles for Scalable and Uniform SERS Substrates (Supporting Information)

Homogeneous surface-enhanced Raman spectroscopy (SERS) substrates are critical for quantitative analysis but remain challenging to fabricate at scale. This study established a hybrid nanoimprint lithography and galvanostatic pulse electrodeposition strategy to fabricate scalable Ag–Au alloy SERS substrates with remarkable signal uniformity. By systematically optimizing pulse parameters, such as current, duty ratio, and deposition bath composition, including the Ag+/Au3+ ratio and the presence of thiourea additive, we achieved the uniform filling of nanoarrays with Ag–Au alloy nanoparticles with an optimal Ag content for the SERS enhancement effect. The Ag–Au SERS substrate prepared under the optimized conditions with 71 at% Ag displayed a high enhancement factor on the order of 106 and a record-low signal variability with a relative standard deviation of 6.8 % throughout the mapping area, surpassing sputtering-based Ag SERS substrates. This approach combines top-down patterning with bottom-up electrochemical growth, thereby offering a cost-effective path for fabricating reproducible plasmonic substrates for electrochemical analysis and environmental monitoring applications.