In this work, we fabricated an efficient macroporous silicon/gold nanoparticles (macro psi/AuNPs) hybrid structure and how well controlling of plasmonic features on macro psi/AuNPs employs them for highly sensitive detection of the very low concentration of cyanine (Cy) dyes molecules. Macro-PSi was synthesized on n-type Si wafer with 3-10 Ω. cm resistivity and 100 orientation using Photo Electro Chemical Etching (PECE) process with630 nm illumination wavelength and 30 mW/cm2 illumination intensity. The macroPSi /AuNPs hybrid structure substrates were prepared by simple and quick dipping process of macroPSi in tetrachloroauric gold solution HAuCl4 with different concentrations of (10-2 M, 10-2 M diluted in 2.9 M of HF, 5 × 10-3 M, and 5 × 10-3 M diluted in 2.9 M of HF). Efficient surface-enhanced Raman scattering (SERS) signals was obtained from macroPSi/AuNPs substrates for Cy dye concentration of about 10-6 and 10-10 M. The detection method is dependent on a nanoparticles sizes process through controlling the concentration in a HAuCl4 solution. Higher SERS signal was found for sample with lower salt concentration of 5 × 10-3 M diluted in HF. The enhancement factors (EF) of Raman's signal increased four orders of magnitude by diluting the salt concentration. The values of EF in the range of 0.8 × 103-0.72 × 107 were obtained by controlling the salt concentration from 10-2 to 5 × 10-3 diluted in HF acid.
Keywords: Cy molecules; Gold nanoparticles; Liquid detection; PECE; SERS active substrate; macroPSi/AuNPs.