Thin-Layer Covalent Organic Framework-Coated Gold Superstructures for Label-Free Raman Spectroscopic Monitoring of Multiple Volatile Organic Compounds.

The detection of multiple volatile organic compounds (VOCs) encountered challenges such as sample complexity, signal reproducibility, sensitivity limitations, and interference resistance. Here, we prepared thin-layer COF-coated gold superstructures (GSP@COF) to capture and identify the fingerprint spectrum of the VOCs. The GSP@COF substrate ensured an even distribution of SERS hotspots, boosted signal intensity, and prevented nanoparticle aggregation, resulting in consistent and reliable analytical results, with less than 5% spatial variations in signal intensity. The substrate's low background signal and improved sensing capabilities allowed for clear detection of benzene ring conjugation peaks and subtle variations in Raman shifts for benzaldehyde, salicylaldehyde, pyridine, and other molecules. It demonstrated high anti-interference properties, with clear differentiation among various components observed through PCA analysis (PC1 + PC2 = 90.1%). Furthermore, the subsequent analysis revealed detection limits of 9.83 × 10-3 μg/m3 for pyridine, 2.08 × 10-3 μg/m3 for benzaldehyde, and 2.4 × 10-3 μg/m3 for salicylaldehyde, respectively, which were 1 to 2 orders of magnitude lower than those reported in other studies.