One-pot synthesis of AuAgPd trimetallic nanoparticles with peroxidase-like activity for colorimetric assays.

In this work, AuAgPd trimetallic nanoparticles (AuAgPd TNPs) with intrinsic and broad-spectrum peroxidase-like activity were synthesized through a one-pot method by co-reduction of HAuCl4, AgNO3, and Na2PdCl4 with NaBH4. The morphology and composition of AuAgPd TNPs were characterized. The peroxidase-like activity of AuAgPd TNPs were highly dependent on the composition and nanostructure of AuAgPd TNPs. Rationally designed AuAgPd TNPs could catalyze the oxidation of various chromogenic substrates including 3,3'5,5'-tetramethylbenzidine (TMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and o-phenylenediamine (OPD) by H2O2 to generate blue, green, and yellow products, respectively. Kinetic assays indicated that AuAgPd TNPs exhibited high affinity to H2O2. Then, sensitive colorimetric assays were developed for H2O2 detection by using ABTS, OPD, and TMB as chromogenic substrates, respectively. Lowest limit of detection (LOD) of 3.1 μM with wide linear range of 6-250 μM was obtained by using ABTS as substrate. Hydrogen sulfide ion (HS-) could effectively inhibit the peroxidase-like activity of AuAgPd TNPs. Thus, a selective colorimetric assay was further fabricated for HS- detection with LOD of 2.3 μM. This work provides an effective way for the synthesis of trimetallic nanozyme with peroxidase-like activity and also for tailoring their catalytic activity for desired use. Graphical abstract.