Introduction of cellulose-cysteine Schiff base as a new ligand for the fabrication of blue fluorescent gold nanoclusters for the detection of indapamide drug

In this work, we synthesized a new ligand namely 2,3-dialdehyde cellulose-cysteine (DAC-Cys) Schiff base by using cellulose and L-cysteine as reagents. The as-synthesized DAC-Cys Schiff base was used as a stabilizing agent for the synthesis of water soluble highly blue fluorescent gold nanoclusters (DAC-Cys-AuNCs). The fluorescence emission intensity of DAC-Cys-AuNCs was quenched by the addition of indapamide drug. The sensing mechanism of the present method was investigated by using high-resolution transmission electron microscopy (HR-TEM), fluorescence lifetime and Fourier transform infrared spectroscopic (FT-IR) techniques. The DAC-Cys-AuNCs exhibited a good blue emission property, and are stable for weeks. The DAC-Cys-AuNCs was responded to indapamide by distinctive quenching of emission peak at 478 nm under excitation wavelength of 410 nm. The degree of fluorescence quenching is linear with increasing concentration of indapamide (0.10–100 μM) with a detection limit of 25 nM. Importantly, the quantitative assay of indapamide in its formulations and biofluids (plasma and urine) was successfully performed using DAC-Cys-AuNCs as a probe. The DAC-Cys-AuNCs-based analytical method paves a new and simple way to assay indapamide in real samples with high sensitivity and selectivity.