Improved SERS performance from uniformly distributed Au nanoparticles by tannic acid treatment

Surface enhanced Raman spectroscopy (SERS) is a powerful molecular analytical tool that allows for highly sensitive chemical detection of low concentration analytes through the amplification of electromagnetic (EM) fields generated by the excitation of localized surface plasmons. SERS performance such as enhancement factor (EF), reproducibility and repeatability is highly related to distribution profile of Au nanoparticles on SERS substrates. The uniformity distribution of Au nanoparticles usually results in good SERS performance. We introduce a new SERS substrate that produces improved performance through surface modification of silicon wafers. For this purpose, hydrophilic silicon wafers are prepared and then their surfaces are coated with tannic acid (TA) by thermal treatment. TA is used as a surface modifier with low cost and high adhesion to synthesize uniform and dense Au nanoparticles. The direct synthesis of Au nanoparticles is carried out through the successive ionic layer absorption and reaction (SILAR) method. 2-naphthalenethiol (2-NAT) dye was utilized to confirm the SERS performance of the as-fabricated substrate. The SERS performance was optimized by controlling the thickness of the Au nanoparticle layer synthesized by repeating the SILAR cycle. We expect the proposed SERS substrate to exhibit good reproducibility and repeatability due to the high uniformity distribution of Au nanoparticles.