Ag Nanoparticle-Decorated Mesoporous Silica as a Dual-Mode Raman Sensing Platform for Detection of Volatile Organic Compounds

Volatile organic compounds (VOCs) often cause serious harm to human health, environment, and industrial productions. The conventional methods for the detection of VOCs show low sensitivity, are time-consuming, and require laboratory-based analysis. Herein, we realized a portable and multiplex detection of atmospheric VOC species by integrating surface-enhanced Raman spectroscopy (SERS) and cavity-enhanced Raman spectroscopy (CERS). The Ag nanoparticle-decorated three-dimensional (3D) mesoporous silica gel with a pore size of about 6.5 nm was fabricated and utilized as an ideal SERS detection platform. The plasmonic Ag coated by SiO₂ was characterized as 3D hotspots for enhanced SERS signals, while a mesoporous SiO₂ structure with abundant silicon hydroxyl groups and optical resonance cavity provided the distinctive features for amplifying CERS signals. The enhanced SERS and CERS dual mode easily achieved the rapid, highly sensitive detection of various VOC molecules in situ, as well as superior signal reproducibility (relative standard deviation < 7.2%) and long-term stability. Combined with a portable Raman instrument, the SERS and CERS dual-mode sensor can be implemented for ultratrace detection of multiple toxic VOCs including toluene (68 ppm), benzene (56 ppm), chloroform (129 ppm), and acetone (161 ppm). Thanks to the super sensitivity, the sensor can be extended to the rapid detection of a small change of atmospheric VOC content and the multiplex detection of VOC gaseous mixtures under room temperature. Thus, the designed SERS and CERS dual-mode sensing platform opens a way to ultratrace detection of various toxic VOC gases and is promising in the sensitive monitoring of natural ecosystem conservation and human health.