High enhancement SERS substrates created using DEP-DLA & annealing Au-W

Techniques of preparing reliable surface enhanced Raman spectroscopy (SERS) substrates with high enhancement factors (EF) in the range of ×10⁶-10⁹ using dielectrophoresis (DEP) of Au nanoparticles is presented. Diffusion limited aggregation (DLA) of Au NPs, here, gives rise to multi-branched fractal geometry that also incorporates the analyte and results in a large density of hot spots. The second substrate was prepared by annealing a thin film of Au on W to form nanometric structures with Au separated from W by a thin (~40nm) tungsten oxide layer. The benefit of using DEP-DLA is that it enables controlled assembly of NPs in real time. SERS of thymine and intensive surface studies using AFM and SEM were carried out.