Highly fluorescent quinone-capped silver hydrosol for environmental remediation and sensing applications

A metal-enhanced fluorescence was achieved from in situ-generated Ag⁰ nanoparticles in the proximity of 2-hydroxy benzaldehyde (2HB). Such nanoparticles eliminated methyl blue (MB) dye from water exclusively in the presence of Zn²⁺ and were proven to be an efficient adsorbent for environmental remediation (maximum uptake capacity 1065 mg·g^-1). Ag was zero valent in the absorbent, while Zn²⁺ was in Zn(OH)₂ form. Fe³⁺ brought back MB in the aqueous medium due to the strong interaction of MB with Fe³⁺ and the regeneration of blue color helped to design a selective and sensitive Fe³⁺ sensing platform colorimetrically (linear detection range 10^-4-10^-6 M; linear detection limit 10^-6 M). The silver nanoparticle-induced metal-enhanced fluorescence was quenched efficiently with MB. Pb²⁺ restored the quenched fluorescence by removing MB from the proximity of the metalized surface of silver, and Pb²⁺ sensing was performed fluorometrically (linear detection range; 10^-5-5 × 10^-8 M limit of detection 5 × 10^-8 M). Iron and lead were also estimated in a variety of natural water sources, including rainfall, drinking water from taps, and water from the Ganga River via spiking method.