Detection of a few of biogenic volatile organic compounds by means of Raman scattering of isocyanide-adsorbed gold nanostructures.

We demonstrate that the NC stretching band of 2,6-dimethylphenylisocyanide (2,6-DMPI) adsorbed on poly(ethylenimine)-capped Au film is very susceptible to the kind of biogenic volatile organic compounds (VOCs) exposed, suggesting that the isocyanide-adsorbed noble metal nanostructures can be used as a platform for a biogenic VOC sensor operating via surface-enhanced Raman scattering (SERS). Specifically, first we demonstrate that highly SERS-active Au films can easily be fabricated onto the inner surfaces of glass capillaries, being able to measure the SERS spectra of 2,6-DMPI facilely and thus to monitor the shift of its NC stretching band rapidly in response to a variety of biogenic VOCs including isoprene, farnesol, and (+)-α-pinene. Secondly, we are able to deduce from the NC stretching peak shifts that farnesol must act as an electron acceptor so as to increase the surface potential of Au nanoparticles, while isoprene and (+)-α-pinene are electron donors, resulting in the decrease in the surface potential of Au nanoparticles. To our knowledge, this is the first report, informing the applicability of SERS, though indirect, in the detection of biogenic VOCs.