• Ag nanoparticle;
  • surface potential;
  • surface-enhanced Raman scattering;
  • 1,4-phenylenediisocyanide;
  • organic vapor

The NC stretching frequency in the potential-dependent surface-enhanced Raman scattering spectrum of 1,4-phenylenediisocyanide (1,4-PDI) is very sensitive to the electrode potential, and much the same peak shift is observed when an Au nanoparticle with mean diameter from 16 to 90 nm attached to 1,4-PDI-adsorbed gold nanogap system is exposed solely to organic vapors. This leads us to conclude that the surface potential of Au nanoparticles should change by as much as +0.57 and −0.34 V, respectively, in the presence of CCl4 and NH3 because of their respective electron-withdrawing and electron-donating properties, regardless of the size of Au nanoparticles in the gold nanogap system. Copyright © 2012 John Wiley & Sons, Ltd.