Synergism of Ag+ and Na+ in N-acetyl-p-quinoneimine matrix for dual sensing applications.

A highly fluorescent silver nanostructure was obtained from a commercially available pharmaceutical drug in an alkaline solution. The fluorescence observed was highly selective to Ag⁺, attributed to the in situ formation of Ag⁰ nanostructures. Nanoclusters are usually ≤ 2 nm in size. Microscopic techniques and dynamic light scattering spectroscopy did not find the presence of particles with ≤ 2 nm in our present work. The absence of a plasmon band in absorption spectroscopy and the presence of Ag₂-Ag₄ in LCMS fragmentations supported the silver giant nanocluster (a larger particle decorating with tiny clusters) with discrete energy levels due to inter-band d-d transition. It ruled out metal-enhanced fluorescence (MEF). Na⁺ increased the fluorescence intensity of giant clusters due to the natural crystallization and confinement effect. The influence of heat and sunlight was analyzed before and after Na⁺ inclusion. Thus, Ag⁺ (linear detection range of 5 × 10^- 5 M to 1 × 10^- 7 M and limit of detection of 3.6 × 10^- 6 M) and Na⁺ (linear detection range 10^- 6 M to 10^- 9 M and limit of detection 7.2 × 10^- 8 M) dual sensing was made possible in a single pot. The technique can facilitate sustainable water management to control water pollution.