Dual-Surfactant-Capped Ag Nanoparticles as a Highly Selective and Sensitive Colorimetric Sensor for Citrate Detection

A colorimetric sensor for the detection of citrate ions is reported here using dual-surfactant-capped Ag nanoparticles (dual-AgNP sensor). A mixture of cetyl trimethyl ammonium bromide and a newly prepared gemini nonionic (GFEO) surfactant was used as a capping agent to synthesize dual-surfactant-capped Ag NPs for selective and sensitive citrate detection. The GFEO surfactant was designed with a specific chemical structure to provide strong binding with citrate for selective and sensitive detection. The developed dual-AgNP sensor showed extremely high selectivity toward citrate even in the presence of interfering species. Quantitative detection of citrate was carried out based on the changes in UV-vis absorbance and naked-eye readout. After optimization, the dual-AgNP sensor exhibited a visual detection limit of 25 μM and a low limit of detection of 4.05 nM with a UV-vis spectrometer. The developed citrate sensor performed well with a urine sample, with a high recovery of 99.6%. The prepared solution sensor was constructed on a paper-based analytical device.