Characterizing the spectral reproducibility of quartz-bound Au nanoparticle substrates for surface-enhanced Raman spectroscopy

Visible extinction and Surface Enhanced Raman Scattering (SERS) spectra using quartz-bound Au nanoparticle substrates are used to identify substrate production-related sources of spectral variability. Hydrosol Au nanoparticle size distributions are known to affect SERS enhancement, but the effect of spatial orientation and nanoparticle physiosorption during substrate preparation on spectral reproducibility and performance are not well understood. Experiments varying quartz slide orientation and Au nanoparticle delivery method show significant concentration-gradient and physiosorption-related aggregation effects in the substrate extinction spectra and SERS spectra of R6G applied to spatially mapped substrate regions. Additionally, applying multiple Au hydrosol treatments to functionalized quartz substrates reveals interesting relationships between Au nanoparticle thickness and substrate extinction and SERS spectra. Of the many factors affecting substrate spectral reproducibility, minimizing concentration gradients and optimizing the rate of Au nanoparticle-quartz physiosorption allow improvements in SERS active substrate spectral reproducibility.