Fluorescence “turn-off–on” approach for the detection of niflumic acid and ammonium persulfate using 2,3-dialdehyde starch-cysteine-molybdenum nanoclusters as a nanosensor

Abstract

Herein, fluorescent molybdenum nanoclusters are synthesized by using Schiff base 2,3-dialdehyde starch-cysteine derivative as a ligand and 2,3-dialdehyde starch-cysteine Schiff base (DCSB) protected molybdenum nanoclusters (MoNCs) are named as “DCSB-MoNCs”. The as-synthesized fluorescent DCSB-MoNCs were stable and exhibited blue fluorescence under excitation at 365 nm. The as-prepared DCSB-MoNCs were narrowly and homogeneously distributed with a mean size of 2.80 ± 1.10 nm. The fluorescence of DCSB-MoNCs is significantly quenched by niflumic acid through non-covalent interactions DC Schiff derivative. Upon the addition of ammonium persulfate (APS) to MoNCs, the non-covalent interactions are cleaved between DCSB-MoNCs and niflumic acid, resulting in restoration the fluorescence of DCSB-MoNCs. In this, niflumic acid acts as both analyte and quencher by using DCSB-MoNCs as a nanosensor, showing a good linear response in the range of 0.005–10 µM with a limit of detection (LOD) of 2.2 nM. Then, “turn off–on” mechanism was established for sensing of APS, exhibiting a wider linear response in the range of 25–55 µM. The developed nanoclusters were successfully applied to detect niflumic acid drug in biological samples (blood plasma and urine) and industrial wastewater.