In recent years, inorganic semiconductor quantum dots (QDs) have garnered significant attention of scientific diaspora owing to their unique photophysical properties. In this series, SnS2-QDs are predicted as one of the promising inorganic quantum dots. However, investigation on the photoluminescence property of SnS2 QDs and its biosensing applications is limited. Therefore, it needs serious exploration. In this work, we report the synthesis of in-situ functionalized fluorescent tin disulfide quantum dots (f-SnS2 QDs) using one-step bottom-up hydrothermal technique. The obtained f-SnS2 QDs are monodispersed in nature and exhibits strong blue fluorescence under UV exposure with a high quantum yield (QY ~8.7%) in aqueous medium. Interestingly, it is observed that fluorescence of f-SnS2 QDs significantly quenched in the presence of Fe3+ ions. The developed optical sensor shows linear response for Fe3+ ions in the concentration range of 0 μM–68 μM (~0.84 μM detection limit). Further, to understand the quenching kinetics, the PL and TRPL studies are conducted which reveal that the quenching phenomenon is both static as well as dynamic in nature. The underneath detailed mechanism is also discussed in the paper. © 2020 Elsevier B.V.