<p>Though analytes are sensed efficiently using nanoparticles as sensing platforms, the employment of metal-enhanced fluorescence (MEF) in this regard is quite new. The MEF of quinone-capped (oxidized 2-hydroxy benzaldehyde) silver hydrosol was synthesized using 2-hydroxy benzaldehyde and silver nitrate in an alkaline medium via simple aging. The MEF was quenched selectively with ascorbic acid and regained selectively with Hg²⁺. Thus, a one-pot twin-sensing platform was obtained for ascorbic acid (range of linear detection: 10^− 5 M – 10^− 8 M; limit of detection: 2.1 × 10^− 6 M) and Hg²⁺ (range of linear detection: 10^− 4 M to 10^− 8 M: 4.45 × 10^− 6 M). The lossy surface wave was ascribed to turning off fluorescence, while the lightning rod effect &amp; higher radiative decay rate were ascribed to turning on fluorescence. A temperature-dependent fluorescence study supports that Hg-induced fluorescence enhancement was not just the restoration of fluorescence of quinone-capped silver hydrosol. Improvement of metal-enhanced fluorescence from bimetallic (Ag⁰ and Hg⁰) nanoparticles due to amalgam formation may open a fresh window for young scientists to venture into the field of nanosensing and sustainable water management.</p> Graphical abstract <p></p>