Sensing of Zn(II) and nitroaromatics using salicyclaldehyde conjugated lysozyme-stabilized fluorescent gold nanoclusters

This manuscript presents new applications of the red-emitting lysozyme-stabilized gold nanoclusters (Lyso-AuNCs) in the field of fluorescent sensing. With the addition of salicylaldehyde (SA) to the solution of Lyso-AuNCs, the red-emission turned immediately to yellow, and the emission band at 650 nm was blue-shifted and enhanced significantly at 498 nm due to the formation of imine linkage between the -CHO group of SA and the-NH2 groups of the lysozyme coated on the surface of AuNCs. The nano-assembly SA conjugated Lyso-AuNCs (SA_Lyso-AuNCs) was applied as a nanoprobe for the fluorescent detection of metal ions and nitroaromatics. With the addition of Zn2+, the probe SA_Lyso-AuNCs showed selective turn-on fluorescence enhancement at 452 nm due to the complexation-induced aggregation of the nanoclusters, and the titration experiment inferred that the Zn2+ ions can be detected down to 1.37 x 10(-7) M. In contrast, when the nitroaromatics were added to the probe SA_Lyso-AuNCs, selective fluorescence quenching of the probe was observed at 650 nm and 498 nm in the presence of picric acid (PA) and para-nitrophenol (p-NP). The limit of detection of nitroaromatics PA and p-NP can be detected down to 2.90 x 10(-7) M and 3.59 x 10(-7 )M, respectively. Finally, the practical utility of the probe SA_Lyso-AuNCs was validated by quantifying PA and p-NP in the real water samples.