Influence of Sodium Borohydride Content on Triangular Silver Nanoprisms Dropped on Copper Hydroxide Nanowire-Based SERS Substrates

In this work, surface-enhanced Raman scattering substrates with triangular silver nanoprisms (AgNPrs) dropped on copper hydroxide nanowires (CuOHNWs) were evaluated. AgNPrs were synthesized in colloidal solution using Ag nitrate, polyvinylpyrrolidone, trisodium citrate dihydrate, hydrogen peroxide, and sodium borohydride (NaBH₄). A set of five solutions with volume percentages from 0.99 to 4.76% v/v of NaBH₄ as reducing agents was studied. The reaction time associated with blue coloration was determined. The evolution of the colloids was studied by UV-vis spectroscopy over a period of 42 days, confirming the good stability of AgNPrs. In addition, their colloidal stability was also verified by the zeta potential. The influence of NaBH₄ concentration over the AgNPrs morphology was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). Finally, SERS substrates were fabricated with AgNPrs deposited on CuOHNW and used to detect methylene blue as a probe molecule. AgNPrs obtained with 2.91% v/v NaBH₄ presented the smallest sizes, and their SERS substrate presented the best Raman intensity.