The use of vibronic phenomena in adsorption phase for developing semiconductor gas sensors

Semiconductor sensor selectivity is of the highest importance for environment monitoring. Surface modifications and multi-sensor systems are widely used for improving selectivity in commercial sensors. Here, we present an experimental study aimed at showing the use of fine vibrational phenomena in species adsorbed on semiconductor surfaces increasing sensor selectivity. Dye molecules were adsorbed on single crystals of Ge and ZnO as well as polycrystalline ZnO and CdS films. We found that resonant vibrational energy transfer could occur from the photo-excited dye if gas molecules have corresponding vibration modes. This energy transfer controls both a luminescent signal from the dye and an electrical response from the semiconductor substrate. The sensor selectivity in this case is due to the overlapping of the rich vibrational spectra of the molecules. We show that water and naphthalene isotopes can be distinguished from each other in this way since they have different vibration frequencies, in contrast to the situation for traditional AchemiresistorsB. Selective sensors for specific gas molecules could be produced in this way by depositing on the semiconductor surface organic dye molecules with vibrational modes AtunedB to the vibrations of those gas molecules. Modern organic synthesis offers wide resources for building systems with the vibration modes selective to specific gas molecules. q2000 Elsevier Science B.V. All rights reserved.