Optical gas sensing properties of ZnO nanowires
Authors: Todros S., Baratto C., Comini E., Faglia G., Ferroni M., Sberveglieri G., Lettieri S., Setaro A., Santamaria L., Maddalena P.
Autors Affiliation: CNR – INFM, Department of Physics and Chemistry, University of Brescia, via Valotti 9, 25133 Brescia, Italy; CNR-INFM COHERENTIA Unity, Dipartimento di Scienze Fisiche, University of Napoli Federico II, Napoli, Italy
Abstract: New breakthroughs in preparation technology have given further impulse for developing chemical sensing devices based on nanostructured ZnO. Due to their peculiar characteristics and size effects, these materials often show novel physical properties. In this work, we studied the optical properties of ZnO nanowires, synthesized via evaporation-condensation (EC) process, by room temperature photoluminescence (PL) and Time Resolved PL analysis. ZnO PL spectrum shows an UV peak, attributed to free exciton, and a broad visible band, strongly depending on the preparation conditions in the range from green to yellow. UV photoluminescence of ZnO nanowires was studied in gaseous atmosphere, targeting mainly NO2 sensing applications. Continuous wave PL shows that a reversible modification is obtained upon exposure to low concentration of NO2. The effect of interfering species like ethanol and RH% has also been studied. Time-resolved PL shows small modifications of recombination rates due to introduction of NO2 not proportional to simultaneous changes in PL intensity. This behaviour supports the idea that NO2 molecules, chemisorbed on the ZnO surface, lead to suppression of radiative states.
KeyWords: Chemical sensing devices; Continuous Wave; Evaporation-condensation; Free excitons; Gaseous atmosphere; Interfering species; Low concentrations; Nano-structured; Optical gas sensing; PL intensity; PL spectra; Preparation conditions; Preparation technology; Radiative state; Recombination rate; Room-temperature photoluminescence; Sensing applications; Size effects; Time-resolved; UV photoluminescence; Visible band; ZnO; ZnO nanowires; ZnO surface, Chemical sensors; Chemisorption; Ethanol; Microsystems; Nanowires; Optical properties; Photoluminescence; Synthesis (chemical), Zinc oxideDOI: 10.1007/978-90-481-3606-3_32