Flexible bipyramid-AuNPs based SERS tape sensing strategy for detecting methyl parathion on vegetable and fruit surface

In present study, a simple and effective surface enhanced Raman scattering (SERS) tape sensing strategy based on bipyramid gold nanoparticles (BP-AuNPs) was developed for sensitive and selective monitoring of methyl parathion residues on vegetable and fruit surface through a simple sampling-and-detection procedure. BP-AuNPs were synthesized by a seed meditated method and systematically characterized using transmission electron microscope (TEM), UV-vis spectrometer, selected area electron diffraction (SAED) and X-Ray diffraction (XRD). The as-synthesized BP-AuNPs showed excellent Raman enhancement effect because their sharp ends provide high electric field enhancement, as revealed by electrodynamic simulations. Also the localized plasmon resonance of the BP-AuNPs matches well with the NIR (785 nm) laser of portable Raman spectrometer, thus maximizing the Raman signal. Two standard SERS probe molecules Rhodamine 6G (R6G) and crystal violet (CV) were first used to prove the effective SERS detection on the model solid (silicon) surface using the BP-AuNPs based tape sensing strategy. The SERS sensor was then applied to detect methyl parathion on surface of cucumbers, tomatoes and apples. A detection limit of ng/cm(2) level was easily achieved. The studies have demonstrated that the BP-AuNPs based SERS tape sensing platform can be potentially used to monitor the trace amount of chemical hazards for food and agricultural safety.