FABRICATION OF Ag/Au ALLOY NANOSTRUCTURE FOR METHYLENE BLUE DETECTION BY SURFACE ENHANCED RAMAN SCATTERING

Abstract

In this study, the author presents new results on the fabrication of silver/gold alloy nanostructures (AgAu alloy) to detect methylene blue by surface-enhanced Raman scattering (SERS) method. The silver/gold alloy nanoparticles are fabricated by the simultaneous reduction of AgNO₃ and HAuCl₄ by by trisodium citrate (TSC). The obtained products are investigated on some properties: the morphology of the alloy NPs are examined using transmission electron microscopy (TEM). The lattice constants of samples and the formation of homogeneous Ag/Au alloy nanocrystals were confirmed by high-resolution transmission electron microscopy (HRTEM) technique. The optical property (plasmon absorption) was analyzed by ultraviolet-visible (UV-Vis) spectroscopy; the experiment for methylene blue (MB) detection by the surface enhanced Raman scattering spectroscopy. The results show that AgAu alloy nanoparticles with molar component ratio 1:2 have a spherical shape, the size in the range of 40-50 nm, and the plasmon absorption peak at 523 nm. Interestingly, the highest SERS activity achieved at AgAu alloy sample with limit of detection (LOD) equals 10^-8 M and the linear dependence was found between the logarithmic concentration of MB and the intensities of the 1624 cm^-1 peak as shown in equation LogI = 0,33*LogC + 5,54, R² = 0,997. This result is particularly interesting for making the high-sensitivity chemical sensors for quantitative analysis of harmful pigments in food safety.