A Phosphorescent Trinuclear Gold(I) Pyrazolate Chemosensor for Silver Ion Detection and Remediation in Aqueous Media

We report a phosphorescent chemosensor based on a trinuclear Au(I) pyrazolate complex or [Au(3-CH3,5-COOH)Pz]3 (aka Au3Pz3) stabilized in aqueous chitosan (CS) polymer media. Au3Pz3 is synthesized in situ within aqueous CS media at pH ∼ 6.5 and room temperature (RT). Au3Pz3 exhibits strong red emission (λmax ∼ 690 nm) in such solutions. On addition of silver salt to Au3Pz3/CS aqueous media, a bright-green emissive adduct (Au3Pz3/Ag+) with a peak maximum within 475–515 nm is developed. The silver adduct exhibits a 4-fold increase in quantum yield (0.19 ± 0.02) compared to Au3Pz3 alone (0.05 ± 0.01), along with a corresponding increase in phosphorescence lifetime. With almost zero interference from 15 other metal ions tested, Au3Pz3 exhibits extreme selectivity for Ag+ with nM/ppb detection limits (6.4−72 ppb, depending on %CS and on the sensitivity basis being a signal-to-noise ratio (S/N) = 3 or a baseline-corrected signal change = 10%). Au3Pz3 exhibits sensitivity to higher concentrations (>1 mM) of othe...