SPR-Enhanced Detection of Isopropanol Vapor Using Au/MIP-Coated Optical Fiber Sensor

Isopropanol (IPA) is a common volatile organic compound (VOC) linked to lung cancer. This study presents an experimental validation of a highly sensitive and selective method for detecting IPA vapor. The method employs a molecularly imprinted polymer (MIP) functionalized on a thin gold (Au) film, which is coated over a small section of no-core fiber (NCF). The sensitivity of the MIP-coated sensor with surface plasmon resonance (SPR) facilitated by the thin gold layer is experimentally compared with the MIP-coated bare NCF. The fabricated sensors were tested with various VOCs, including acetone, methanol, ethanol, and IPA, to evaluate their selectivity. The sensors demonstrated selective detection of IPA at parts per million (ppm) levels at room temperature. Our results show that the Au/MIP sensor exhibits seven times higher sensitivity (0.014 nm/ppm) compared to the bare fiber coated only with the MIP layer (0.002 nm/ppm), along with a limit of detection (LOD) of 82.41 ppm. Control experiments suggest that the combined effect of the MIP and the gold film significantly enhances the performance of the optical fiber sensor. These findings highlight the potential of this sensor for noninvasive exhaled breath measurement of VOC biomarkers.