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

[Image: see text] 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.