Electric-field enhancement of molecularly imprinted sol-gel-coated Au nano-urchin sensors for vapor detection of plant biomarkers

Detection of plant volatile organic compounds (VOCs) provides a new approach for real-time, on-field crop growth monitoring in agriculture. Gold (Au) nano-urchins with branched tips were synthesized and deposited on glass slides with controlled densities to generate enhanced electronic hot spots. The refractive index (RI) sensing capability of the slides was investigated as a function of nano-urchin density. A molecularly imprinted sol-gel (MISG) solution was spin-coated on the slide having the optimum RI sensing capability to form the MISG@Au nano-urchin sensors. Four MISGs were developed for the detection of typical plant biomarker VOCs: cis-jasmone, limonene, alpha-pinene, and gamma-terpinene. The normalized response indicated that selectivity of the MISG@Au nano-urchin sensors to the corresponding template terpenes was generated. According to the principal component analysis (PCA), both of the peaks in the absorption spectrum took necessary effects on terpene detection and discrimination, which was attributed to the hot spots generated by the Au nano-urchins and their coupling effects.