Synergistic molecular assembly of an aptamer and surfactant on gold nanoparticles for the colorimetric detection of trace levels of As3+ ions in real samples

Abstract

The use of the synergistic molecular assembly of an aptamer and cetyltrimethylammonium bromide (CTAB) on gold nanoparticles (AuNPs) is described for the selective and sensitive colorimetric recognition of As³⁺ ions in water samples. The As³⁺ ions coordinate with Ars-3 aptamer–AuNPs, causing aggregation in the presence of CTAB, which induces a red-shift in the surface plasmon resonance (SPR) band and a visual change in the color. The aptamer has shown a strong tendency to bind with As³⁺ ions using CTAB as a binder, exhibiting good linearity between the absorption ratio (A₆₅₀/A₅₂₀) and the concentration of As³⁺ ions (1.0–100 ppb) with a detection limit of 16.9 ppb. In contrast, other chemical species (metal ions and anions) did not induce these changes at all, and thus the aptasensor is highly specific for As³⁺ ion sensing. The spectroscopic and TEM results show high selectivity for As³⁺ ion sensing and the assay is completed within 30 min. The aptamer–AuNP-based colorimetric method illustrates the potential utility for screening As³⁺ ion levels in real samples. The developed aptasensor was successfully applied for the detection of As³⁺ ions in water and cosmetic samples, signifying its remarkable application for As³⁺ ion sensing in real samples.