Ultrasensitive detection of trinitrotoluene by Fe3O4@mTiO2/P-ATP-TNT/Au@Ag SERS sensor via synergetic effect

Abstract

A novel SERS sensor based on Fe₃O₄@mTiO₂/P-ATP-TNT/Au@Ag magnetic nanoparticles (NPs) is reported for the first time to detect trace trinitrotoluene (TNT) explosive. Firstly, the mesoporous Fe₃O₄@mTiO₂ magnetic NPs were synthesized and functionalized by P-ATP. Due to the increased surface area, the mesoporous TiO₂ was conducive to P-ATP loading. Upon addition of TNT, the electronic resonance-active P-ATP-TNT complex formed through a charge transfer process from the electron-rich amino group of P-ATP to the electron-deficient aromatic ring of TNT. After that, introducing Au@Ag to Fe₃O₄@mTiO₂/P-ATP-TNT NPs, the P-ATP-TNT complex largely enhanced the SERS signal in the presence of trace TNT. In addition, the SERS enhancement was also provided by Au@Ag and Fe₃O₄@mTiO₂/P-ATP-TNT NPs plasmon resonance. The detection limit of TNT was as low as 10⁻¹² M in deionized water, which was much lower than the maximum concentration of 88 nM allowed by the US Environmental Protection Agency (EPA). More importantly, Fe₃O₄@mTiO₂/P-ATP-TNT/Au@Ag SERS substrate was further studied to detect TNT in real systems, such as lake water and liquor, using a portable-Raman spectrometer.