A novel fluorescent turn-on probe based on thiosemicarbazide-naphthalene for selectively detecting Zn²⁺

A new thiosemicarbazide-naphthalene-based fluorescent chemosensor FNC ((2-(furan-2-carbonyl)-N-(naphthalen-1-yl)hydrazine-1-carbothioamide)) for Zn²⁺ was synthesized and identified. FNC was applied to selectively detect Zn²⁺ with fluorescent turn-on response. The detection limit was determined to be 1.93 µM, which is much below the WHO standard (76.5 µM). The detecting mechanism of FNC to Zn²⁺ was revealed to bind FNC to Zn²⁺ in the proportion of 1: 1 by Job plot, ESI-mass and ¹H NMR titrations. DFT and TD-DFT calculations were performed for FNC and FNC-Zn²⁺, which provide insight into structural, electronic and photophysical properties.