On-chip surface-enhanced Raman scattering arrays for selective sensing of NO2 exhaust emissions from construction machinery

Nitrogen oxides from construction machinery exhaust pose a significant threat to the environment and human health. Therefore, effective capture and highly selective detection of NO 2 is of utmost importance. Surface-enhanced Raman scattering (SERS) is a spectroscopic technique that provides molecular fingerprint information and enables qualitative and quantitative analysis of molecules at extremely low concentrations. However, the application of SERS for gas molecules with small scattering cross sections, such as NO 2 , is still in its infancy. Based on this, a sensing device for capturing and selectively detecting NO 2 from construction machinery exhaust was developed. The device consists of a gas collection module and a Raman signal amplification module containing a 4, 4’-diaminodiphenyl disulfide (APDS) probe-modified flexible Au@PDMS chip. The Au@PDMS chip amplifies the Raman signals of molecules, while the APDS selectively and rapidly captures NO 2 . The proximal electron-rich nitrogen atom and the ortho-electron-poor aromatic hydrogen atom of the APDS probe form a stable six-membered ring complex with the N atom of NO 2 , and hydrogen bonding interactions occur between the H atom in APDS and the O atom in NO 2 . This ring complexation allows the Au@PDMS chip to capture NO 2 quickly and effectively, resulting in changes in SERS signals and facilitating quantitative analysis of NO 2 . Combined with the gas detection device, the chip can identify NO 2 within 5 min with a detection limit of 3.5 ppm. This sensor device has high selectivity for NO 2 detection in real exhaust gases and has great potential for practical detection of construction machinery exhaust gases.