Current Density Optimization for SERS Substrates Using Galvanostatically Anodized TiO2 Nanostructures Decorated with Pulsed-Electrodeposited Silver Dendrites

In this work, the effect of the applied current density (J) during galvanostatic anodization of titanium (5-30 mA/cm²) on the TiO₂ morphology and its influence on the SERS performance after pulsed silver electrodeposition (5 mA/cm², 400 cycles, 50 ms ON/250 ms OFF) was evaluated. SEM micrographs showed a transition from nanotubes with scarce nanograss to a dense coverage of nanograss over the surface, which conditioned the formation and distribution of silver nanoparticles and dendrites. Using methylene blue as a probe molecule, the substrate anodized at 15 mA/cm² exhibited the highest SERS intensity, attributed to the high density of hot spots vertically distributed in the 3D dendrites. The optimized substrate demonstrated detection of methylene blue down to 1 × 10^-11 M and reached an analytical enhancement factor of 7 × 10⁷, highlighting its strong performance. These results establish galvanostatic anodization as a novel and effective route for designing reproducible and scalable TiO₂/Ag substrates with high SERS response.