NIR sensing of Zn(ii) and subsequent dihydrogen phosphate detection by a benzothiazole functionalized ninhydrin based receptor

Abstract

A benzothiazole functionalized ninhydrin based chemosensor (L₁), exhibits selective naked eye detection of biologically important zinc ions (from light yellow to orange) accompanied by a ‘turn-on’ fluorescence emission response in the near infra-red (NIR) region. Most importantly, Zn²⁺ ion induced ‘turn-on’ fluorescence emission is also preserved in the presence of Cd²⁺ and most of the other competing metal ions which clearly suggests the high sensitivity of the chemosensor towards Zn²⁺. The Job's plot suggests 1 : 1 binding of the L₁ with the Zn²⁺ ion with a detection limit of 6 nM. Detailed ¹H NMR titrations were also conducted to understand the binding behaviour of L₁ towards the Zn²⁺ ion. The ‘L₁–Zn²⁺ ensemble’ further shows a ratiometric response to H₂PO₄⁻ among other competitive anions and nucleotides in the same experimental conditions.