Deep eutectic solvent-enabled green synthesis of gold nanoparticle-decorated ZIF-L composites for colorimetric detection of trimethoprim.

Developing environmentally friendly synthesis strategies for metal-organic frameworks (MOF) and their hybrid nanocomposites is critical to creating sustainable, high-performance materials for analytical sensing applications. In this study, a gold nanoparticle-decorated ZIF-L (ZIF-L/Au) composite was synthesized via a deep eutectic solvent (DES)-assisted green synthesis, thereby providing enhanced stability and improved dispersion of Au nanoparticles and minimizing the use of hazardous organic solvents. The DES-stabilized ZIF-L/Au composite exhibited strong peroxidase-like activity toward ABTS˙+ radical scavenging, effectively decolorizing it from green to transparent. Notably, the presence of trimethoprim (TMP) inhibited this catalytic decolorization, leading to a concentration-dependent restoration of the green color. Under optimized conditions, the ZIF-L/Au composite enabled colorimetric detection of TMP with high sensitivity and selectivity, with a limit of detection of 4.38 nM. This work provides a sustainable strategy for constructing functional MOF-based hybrid nanomaterials and demonstrates their strong potential for practical, on-site monitoring of antibiotic residues.