Ultra-fast and ultra-sensitive 2,4-dinitrotoluene vapor sensing using gold nanoparticle assembled SERS probes

摘要

Surface enhanced Raman scattering (SERS) amplifies the small Raman scattering cross section of molecules toward distinguishable signal. It has been advanced into an influential label-free nondestructive method to measure vibrational fingerprints of molecular structures directly. We report here the demonstration of vapor detection of 2,4-dinitrotoluene (2,4-DNT), a typical manufacturing impurity of trinitrotoluene (TNT) based explosives, using reproducible ultrasensitive SERS substrates, i.e., assembled gold nanoparticles (GNPs) synthesized by a UV photoreduction method. The estimated detection limit was achieved 0.4 attogram, which corresponds to a sub-ppb DNT concentration in air. The 2,4- DNT molecules was noticeable within a minute of exposure to the DNT vapor at room temperature. The detection time was as short as only 2 seconds with 12 mW 785 nm laser excitation at the SERS substrate. Our study shows that larger GNPs (~ 117 nm in diameter) with higher density, an enhancement factor of 5.6x106, exhibits the high sensitivity and the fast detection response, as compared to smaller and lower density GNPs. Dynamic depletion by laser heating indicates that our GNP based sensor is possible real time 2,4-DNT detection.