Metal self-reducing triggered green etching for the CuO@Ag composite synthesis and its application in high-sensitive lateral flow immunoassay

• The CuO@Ag composite was synthesized by metal self-reducing triggered green etching. • Flower-like morphology of the CuO@Ag improved its binding ability with antibodies. • The CuO@Ag has excellent photothermal conversion efficiency. • The dual-mode immunosensor can achieve high-sensitive detection of clenbuterol . Photothermal materials has aroused extensive attention for building multi-signal immunosensors. Herein, a metal self-reducing triggered green etching strategy was employed for the synthesis of CuO@Ag nanoparticles (NPs) with high photothermal conversion efficiency and better antibody coupling efficiency. The flower-like morphology of the CuO@Ag NPs has improved its binding ability with antibodies, which enables them to serve as the multifunctional signal label of the lateral flow immunoassay (LFIA). Then, a colorimetric-photothermal dual-mode LFIA (CuO@Ag-based LFIA) was designed for the highly sensitive detection of clenbuterol hydrochloride (CLE). After direct, the CuO@Ag NPs endowed T-line to be irradiated by an 808 nm laser to obtain photothermal signal owing to their strong photothermal conversion efficiency of CuO@Ag. Under optimal conditions, the detection limits of the CuO@Ag-based LFIA are 0.205 ng mL −1 and 0.131 ng mL −1 under colorimetric and photothermal modes, respectively, which are 13 and 20 times sensitive than that of the conventional AuNP-based LFIA. Additionally, the LFIA was assessed by measuring CLE in food samples with recovery rates ranging from 86.37 % to 103.72 % and coefficient of variations (CVs) ranging from 2.52 % to 9.64 %. Consequently, this work provides qualitative-quantitative point-of-care testing (POCT) approach and has important reference value for other facile, green, and low-cost synthesis of composite signal labels in the LFIA system.