One-pot Preparation of Creatinine-functionalized Gold Nanoparticles for Colorimetric Detection of Silver Ions

Creatinine-functionalized AuNPs (CreAuNPs) were prepared via a facile one-pot reaction of sodium borohydride and the mixture solution of gold(III) chloride trihydrate and creatinine. The morphology and surface state of as-prepared CreAuNPs were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. All the results demonstrated that CreAuNPs were spherical with an average diameter of about 4.2 nm, and creatinine existed on the surface of AuNPs via Au-N interaction. The as-prepared CreAuNPs exhibited a weak surface plasmon resonance (SPR) absorption owing to their small size, while the addition of Ag+ could induce the aggregation of spherical CreAuNPs, producing a strong SPR absorption and apparent color change from colorless to purple owing to the surface plasmon coupling. On this basis, a colorimetric assay for Ag+ was established. The assay could selectively detect Ag+ as low as 1 μM with a good linearity in the range of 5–40 μM. Additionally, the assay was successfully applied to the determination of Ag+ in tap water, lake water, and river water samples.