A simple label-free rhodamine 6G SERS probe for quantitative analysis of trace As3+ in an aptamer–nanosol

Abstract

Gold nanoparticles (NGs) were modified by the aptamer (ssDNA) to prepare a NGssDNA probe for As³⁺. In pH 8.0 HEPES buffer solution containing 50 mmol L⁻¹ NaCl, rhodamine 6G (Rh6G) molecules adsorbed on the NGssDNA sol substrate exhibited a strong surface-enhanced Raman scattering peak (SERS) at 1358 cm⁻¹. Upon addition of As³⁺, it reacts with the NGssDNA probe to form a stable As–ssDNA complex and release NGs that were aggregated to the NG aggregates (NGAs) as a substrate, in which Rh6G SERS activity is very weak. With the increase of As³⁺ concentration, the SERS peak decreased at 1358 cm⁻¹ due to more NGAs forming. The decreased SERS intensity responds linearly with the concentration of As³⁺ over 0.288–23.04 ng mL⁻¹, with a detection limit of 0.1 ng mL⁻¹.