Improved the performance of tri_metallic plasmonics SERS sensors by controlling the metals ratio

In this paper, three distinct types of nano and tri_metallic SERS plasmonics sensors were configured, depending on their mixing volumetric ratio of metal solutions. Au, Ag, and Pd of fixed concentrations of 2 mM were mixed following the volumetric ratios, (1:1:1), (2:2:1) and (1:2:2), respectively, to synthesize the required ion reduction solutions necessary for the formation of tri_metallic nanoparticles. A meso porous silicon substrates (meso Psi) were dipped in each solution to produce plasmonics sensors. Bare (meso Psi) were synthesized by laser-supporting etching (LSE) method using (40 mW/cm2) laser illumination intensity, (10 mA/cm2) etching current density, and (10 min) etching period. The synthesized plasmonics sensors Au: Ag: Pd nanoparticles / meso Psi were examined at different concentrations of chlorpyrifos from 2 x 10-7 M to 2 x 10-9 M. The synthesised sensors showed strong dependence on nanoparticle sizes, population of hot spot regions, and surface density of tri_metallic nanoparticles. Higher (EF), lower (LOD) and high degree of reproducibility with minimum variation of 1 x 108, 10-13 M and 3.6% correspondingly was realized from the sensor which prepared using solution of volumetric ratio (2:2:1), due to the extra ordinary specific surface area. These high surface density of tri_metallic nanoparticles and hot spot regions provided a very high energy transfer efficiency from the nanoparticles to the pesticides molecules. The control of the volumetric ratios of tri_metallic ionic solutions was an effective and easy-to-implement path for improving the performance of plasmonics sensors to detect chlorpyrifos concentrations less than the internationally permissible limit.