Reusable Schiff base functionalized silica as a multi-purpose nanoprobe for fluorogenic recognition, quantification and extraction of Zn~(2+) ions

摘要

Nowadays, sole recognition of targeted species is not sufficient to quantify or recover it from environmental samples. Therefore, current challenge in the management of crucial species is to improve or design sensing probes which are able to recognize, quantify as well as recover it from various assays. Herein, a Schiff base chemosensor SB has been modulated to SB-Silt after incorporating hydrolysable units for its covalent grafting on silica surfaces. Interestingly, despite fluorogenic insensitivity of SB towards metallic species, SB-Silt was found to be highly efficient for the recognition and quantification of Zn~(2+) ions. Furthermore, functionalization of nanosilica with SB-Silt produced a multi-functional nanoprobe SB®SNPs for monitoring Zn~(2+) ions. The 'turn ON' fluorescence emission in SB-Silt and SB@SNPs (at 437 nm and 457 nm, respectively) in the presence of Zn~(2+) ions enabled the detection upto 6.8 nM and 0.17 µM (LODs), respectively. The maximum adsorption capacity (Q_m) of SB@SNPs for Zn~(2+) ions was determined to be 167.2mgg~1. Moreover, the SB-Silt-Zn~(2+) conjugate (formed by the interaction of SB-Silt and Zn~(2+) ions) exhibited a complete quenching of fluorescence (at 437 nm) accompanied with continuous red shifting of emission wavelength to 517 nm in the presence of hydrogen phosphate (upto 4 equiv.). Overall, the developed material is highly efficient, sensitive, selective, reusable and easily separable, and hence can be used as a multifunctional nanoprobe.