Portable device integrated with a MOF-on-MOF aggregation-induced emission nanozyme for dual-mode formaldehyde detection.

A zirconium-based MOF-on-MOF hybrid nanostructure (AIE-MOF@PCN-222, average size 3860 nm) was synthesized and characterized by SEM, TEM, XRD, XPS, FTIR, BET and TGA, which displays excellent peroxidase-like activity and stable aggregation-induced emission (AIE) properties. The dual-mode colorimetric-fluorescent sensing of formaldehyde relies on the synergistic mechanism of specific Schiff-base condensation, nanozyme catalysis and fluorescence resonance energy transfer (FRET). After parameter optimization, the sensor presents a linear response of 4-40 µM, with detection limits of 14.5 nM (colorimetric) and 1.78 nM (fluorescent). A 3D-printed portable device integrated with PDMS microfluidics was developed for on-site detection. In spiked shrimp and fish samples, the sensor achieves recoveries of 97.60-103.50% (colorimetric, RSD ≤ 2.95%) and 98.20-102.40% (fluorescent, RSD ≤ 3.12%), with relative errors below 1.51% relative to HPLC. This strategy provides a promising dual-mode platform with potential for portable HCHO screening in food matrices for HCHO detection in food matrices.