We wish to report, a minute synthesis of green fluorescent copper nanocluster by simple sonication. 1-Thio-β-d-glucose was used as a capping ligand to synthesis copper nanocluster (TG-CuNCs). The TG-CuNCs exhibit the emission maximum at 430 nm. The synthesized TG-CuNCs was well characterized by UV–vis, fluorescent, XRD, HR-TEM and FT-IR techniques. After the addition of Hg²⁺ or S²⁻ into TG-CuNCs, the fluorescence was quenched. Based on the quenching of fluorescence, we have calculated the detection limit 1.7 nM and 1.02 nM for Hg²⁺ and S²⁻, respectively. Finally, we have applied TG-CuNCs for the detection of Hg²⁺ and S²⁻ in tap, river, pond water. Importantly, the smartphone aided paper-based kit was developed for on-site monitoring of Hg²⁺ and S²⁻ ions. To the best of our knowledge, this is the first report for the one-minute synthesis of TG-CuNCs and the preparation of smartphone aided paper-based kit for on-site monitoring of Hg²⁺ and S²⁻ ions. Further, it is anticipated that this synthesis of TG-CuNCs and smartphone aided paper-based kit for Hg²⁺ and S²⁻ will be useful materials in the filled with the biosensor, material science and nanotechnology.