Convenient colorimetric-fluorescent dual-mode recognition of I− in agricultural products and visual determination of Hg2+ in drinking beverages using Ag-Pt bimetal quantum dot nanozyme

Conveniently and efficiently monitoring I − and Hg 2+ in agricultural products or drinking beverages for the protection of human health is currently a great challenge. With this aim, a Ag-Pt bimetal quantum-dot nanozyme boosted by bioactive folic acid (FA@Ag-Pt QDs) was first developed for multichannel monitoring of I − and Hg 2+ in this work using a two-step liquid-phase reduction method. Not only did the present FA@Ag-Pt QDs possess superior peroxidase-like activity with Michaelis constant ( K m ) and maximal reaction rate ( V max ) of 0.01 mM/2.95 × 10 −8  M·s −1 and 1.15 mM/3.88 × 10 −8  M·s −1 , respectively, trace Hg 2+ or I − could exclusively alter their enzyme-mimic performance with obvious color changes from blue to colorless or dark blue. I − could also strengthen the inherent fluorescence property of FA@Ag-Pt QDs. When applied for visual monitoring of I − and Hg 2+ in real beverages or iodine-containing agricultural products, the detection recoveries were 93.9 %–105.3 % and 96.8–104.3 % with low detection limits of 6.56 × 10 −8 mol/L and 4.00 × 10 −10 mol/L (S/N = 3), respectively. The recovery and detection limit for fluorescent detection of I − were 95.8 %–104.1 % and 1.75 × 10 −8 mol/L (S/N = 3), respectively. The mechanisms driving the improved peroxidase-like activity of FA@Ag-Pt QDs and their selective monitoring of Hg 2+ and I − were illustrated in detail. The proposed FA@Ag-Pt QDs will act as an efficient sensor for the practical multichannel monitoring of Hg 2+ and I − , with superior catalytic signal amplification.