ZnO–Ag hybrids for ultrasensitive detection of trinitrotoluene by surface-enhanced Raman spectroscopy†
An efficient and green approach was used to fabricate novel and low-cost surface-enhanced Raman scattering (SERS) spectroscopy sensors based on 4-aminothiophenol (4-ATP) functionalized ZnO–Ag hybrid nanoflowers for the detection of explosives. Such SERS sensors exhibited high sensitivity to rhodamine 6G (R6G) at a low concentration of 10−12 M and an enhancement factor of over 4.12 × 106 was achieved. Moreover, the Raman-inactive trinitrotoluene (TNT) initiated the high Raman scattering of non-resonated 4-ATP through the formation of a π-donor–π-acceptor interaction between the π-acceptor, TNT, and the π-donor, the 4-ATP–Ag–ZnO complex, on the flower-like hybrids. Because this π-donor–π-acceptor interaction could effectively induce the “hot spots” for SERS, TNT concentrations as low as 5 × 10−9 M could be detected. Furthermore, other derivatives of TNT were also explored, and this sensor exhibited better selectivity for TNT than other similarly structured explosives. The low-cost hybrid SERS substrates presented good sensitivity and reproducibility for the analytes employed, demonstrating promising application in forensic science and homeland security.