Synthesis and DFT calculation of microbe-supported Pd nanocomposites with oxidase-like activity for sensitive detection of nitrite.

[Display omitted] • PEI modification increased adsorption capacity of Pd(Ⅱ) and catalytic activity. • Synthesis of Pd/MMR from modified microbial residue was optimal at 25 °C. • DFT simulation revealed ROS generation mechanism from O 2 on Pd (1 1 1) surface. • Pd/MMR platform could sensitively and reliably detect nitrite. Nanozymes have emerged as the forefront of research in analytical sensing due to their promising applications. In this study, we utilized polyethyleneimine (PEI)-modified Pichia pastoris residue to synthesize microbial-based palladium nanocomposites (Pd/MMR) through simple in-situ reduction methods. The dispersed active sites of Pd nanoparticles with a size of 2.12 ± 0.49 nm that were supported by microbial biomass provided excellent oxidative enzyme-mimicking activity to Pd/MMR. The catalytic mechanism of Pd/MMR involved the combined action of 1O 2 , ·OH, and · O 2 –, and possible reaction pathways and corresponding energy barriers were also revealed using DFT calculations. We also established a quantitative detection platform for nitrite using Pd/MMR. The platform could detect nitrite at concentrations of 10–300 μM with a detection limit of 0.27 μM, and was successfully applied to detect nitrite in real samples. These findings serve as a reference for the synthesis and application of metal nanocomposites using microorganisms. [ABSTRACT FROM AUTHOR]