Thiourea enhanced oxidase-like activity of CeO2/CuxO nanozyme for fluorescence/colorimetric detection of thiourea and glutathione.

A novel fluorescence/colorimetric dual-mode sensor, based on enhancement of the oxidase-like activity of CeO 2 /Cu x O nanozyme towards the oxidation of o -phenylenediamine (OPD) induced by thiourea (TU), has been proposed for TU detection. The catalytic activity enhancement on CeO 2 /Cu x O can be attributed to the strong electron-donation ability of TU, which promoted hydroxyl radical generation and amplified OPD oxidization with enhanced dual-signal readout. By integrating a portable paper-chip and smartphone system, this CeO 2 /Cu x O-OPD system achieved on-site visual colorimetric analysis of TU. The dual-mode sensor demonstrated high sensitivity and specificity in recognizing TU, with a detection limit (LOD) of 1.90 μM and a linear range (LR) 2.5–80 μM in fluorescent mode; as well as an LOD of 6.69 μM and an LR 10–250 μM in colorimetric mode. Furthermore, the CeO 2 /Cu x O-TU-OPD system has been designed for dual-mode glutathione (GSH) detection with enhanced sensitivity, achieving an LOD of 0.19 μM and an LR 0.5–10 μM in fluorescent mode; as well as an LOD of 1.24 μM and an LR 1.25–25 μM in colorimetric mode. Additionally, GSH discrimination (fluorescent mode) was successfully achieved in different biological samples, showing good consistency with the standard method. The recoveries ranged from 96.8 % to 116.7 % in serum samples and from 97.3 % to 107.7 % in cell lysates, with RSDs less than 2 %. This work not only introduced a novel approach to enhance oxidase-like activity of nanozymes but also provided an efficient field-suitable tool for enhanced dual-mode response towards TU and GSH. [Display omitted] • CeO 2 /Cu x O nanozyme was synthesized via a deep eutectic solvent strategy with l -proline as a ligand. • A dual-mode fluorescence/colorimetric sensor was developed for thiourea and glutathione detection. • The on-site visual colorimetric sensing was achieved by integrating a portable paper-chip and smartphone system. • TU interact with CeO 2 /Cu x O nanozyme to facilitate redox couples' circulation and enhance ·OH generation. [ABSTRACT FROM AUTHOR]