Nano-scale minerals in-situ supporting CeO nanoparticles for off-on colorimetric detection of L-penicillamine and Cu ion.

Realizing the high value-added utilization of cheap minerals in environmental catalysis has important practical significance. Herein, four nano-scale minerals, namely halloysite (Hal) nanotubes, palygorskite (Pal) nanorods, and montmorillonite (Mon) and hydrotalcite (LDH) nanosheets, were selected for in-situ supporting CeO nanoparticles (NPs) by a facile one-pot hydrothermal method. Among various nanocomposites (NCs), CeO/Pal behaves the highest peroxidase-like activity, attributing to larger surface area for uniformly dispersing CeO NPs and more exposed active oxygen vacancy (O) defects. A novel off-on colorimetric strategy was constructed for detecting toxic L-penicillamine (LPA) and Cu ion with limit of detections (LODs) of 8.37 and 9.80 μM, respectively. Density functional theory (DFT) calculations show that the O defect on CeO(111) surface can catalyze the heterolytic cleavage of HO into HO and oxygen radical (•O), instead of being two hydroxyl radicals (•OH) on clean surface. It can also act as trapping site for O and HO adsorption, improving the oxygen affinity and hydrophilicity of CeO/Pal. This study provides a feasible strategy for designing mineral-based nanozymes and an insight into the possible catalytic mechanism.