Tuning Zn(II) selectivity by conjugating vitamin B6 cofactors over bovine serum albumin stabilized red-emitting silver nanoclusters

The red-emitting bovine serum albumin stabilized silver nanoclusters (BSA-AgNCs) were conjugated with the vitamin B6 cofactors pyridoxal 5 '-phosphate (PLP) and pyridoxal (PL). The deconvoluted bands in XPS revealed that the conjugation occurred due to the formation of imine-linkage between the vitamin B6 cofactors and the BSA functionalized over BSA-AgNCs. The TEM images supported the formation of pseudo-spherical shaped nanoaggregates upon conjugating vitamin B6 cofactor PLP over BSA-AgNCs. An emission band appeared at 532 nm after the conjugation of PLP or PL over the surface of BSA-AgNCs. The in situ formed nano-assembly PLP_BSAAgNCs and PL_BSA-AgNCs showed a significant fluorescent enhancement, respectively, at 490 nm and 481 nm in the presence of Zn2+. The complexation-induced fluorescence enhancement from PLP_BSA-AgNCs and PL_BSAAgNCs was reversed by adding a strong chelating agent EDTA. In addition, the fluorescence of PL_BSA-AgNCs was irreversibly quenched with the appearance of an emission band at 423 nm in the presence of Hg2+. The analytical performance and sensing mechanism of the developed nanoprobes PLP_BSA-AgNCs and PL_BSA-AgNCs were discussed, and the highly selective and sensitive nanoprobe PLP_BSA-AgNCs was applied for the quantification of Zn2+ in real samples.