Silver loaded graphene as a substrate for sensing 2-thiouracil using surface-enhanced Raman scattering

An efficient method was developed for the elucidation and quantitative determination of 2-Thiouracil using surface enhanced Raman spectroscopy (SERS) with substrates of silver nanoparticles seeded on graphene nanosheets (Ag/G). Graphene was used as a support to allow for uniform distribution of silver nanoparticles as proved by the TEM images. The assignment of the vibrational modes in SERS was performed with the help of density functional theory. The bands of 2-Thiouracil at 789, 913, 957, 1368, and 1554 cm⁻¹ are assigned to γ (C6-N3), δ (N3-C6-C8), (H-C7-C8-H) twist, ν (C5-N4), and ν (C5-N3). After introducing the Ag/G substrates these bands were shifted to 815, 931, 951, 1377 and 1527 cm⁻¹ respectively. In addition, the results demonstrate that Ag/G enhances the intensity of these bands. The highest SERS enhancement band at 815 cm⁻¹ was used to establish a calibration curve between the SERS signal intensity and 2-Thiouracil concentration ranging from 1 μM to 0.1 μM with a detection limit (S/N = 3) of 10 nM. The corresponding correlation coefficient of the linear equation was 0.9995. Therefore, Ag/G is a highly promising SERS substrate for the detection of 2-Thiouracil at ultra-low concentrations. This will further enhance the application of surface-enhanced Raman scattering in drug detection.