Organic isocyanide-adsorbed gold nanostructure: a SERS sensory device for indirect peak-shift detection of volatile organic compounds

Abstract

Organic isocyanide adsorbed on a noble metal nanostructure can be used as a platform for a volatile organic compound (VOC) sensor operating via surface-enhanced Raman scattering (SERS). This is possible since the NC stretching band of organic isocyanides such as 2,6-dimethylphenylisocyanide (2,6-DMPI) is very susceptible to the surface potential of Au onto which 2,6-DMPI is assembled. The surface potential of Au nanoparticles is even subject to change by VOCs, which can be easily monitored by the SERS of 2,6-DMPI. Thereby, under the flow of CCl₄ vapor at a partial pressure of 12.8 kPa, for instance, the NC stretching band is blue-shifted by up to 20 cm⁻¹ within 30 s, corresponding to a potential change of +0.56 V. Conversely, under the flow of butylamine at 12.8 kPa, the NC stretching band is red-shifted, instead of being blue-shifted, by as much as 12 cm⁻¹. At lower partial pressures, even a blue- or red-shift of 1 cm⁻¹ was reproducibly measured at a partial pressure of 125 mPa, corresponding to 6.5 ppm for CCl₄, suggesting that the present detection limit is superior to the results obtained via other techniques, especially those operating based on gold nanoparticles and aggregates.