Blue- and red-shifts of V2O5 phonons in NH3 environment by in situ Raman spectroscopy. (5th December 2017)

• Record Type: Journal Article
• Authors: Akande, Amos Adeleke; Machatine, Augusto Goncalo Jose; Masina, Bathusile; Chimowa, George; Matsoso, Boitumelo; Roro, Kittessa; Duvenhage, Mart-Mari; Swart, Hendrik; Bandyopadhyay, Jayita; Ray, Suprakas Sinha; Mwakikunga, Bonex Wakufwa
• Is Part Of: Journal of physics. Volume 51:Number 1(2018)
• Publication Date: 2017-12-05
• Subjects: V2O5 -- VO2 -- in situ Raman sensing -- blue-shift -- red-shift -- selectivity -- phonons; Physics -- Periodicals; 530
• DOI: 10.1088/1361-6463/aa98fe
• Languages: English
• ISSNs: 0022-3727

Abstract

Abstract: A layer of ~30 nm V2 O5 /100 nm-SiO2 on Si was employed in the in situ Raman spectroscopy in the presence of NH3 effluent from a thermal decomposition of ammonium acetate salt with the salt heated at 100 °C. When the layer is placed at 25 °C, we observe a reversible red-shift of 194 cm −1 V2 O5 phonon by 2 cm −1 upon NH3 gas injection to saturation, as well as a reversible blue-shift of the 996 cm −1 by 4 cm −1 upon NH3 injection. However when the sensing layer is placed at 100 °C, the 194 cm −1 remains un-shifted while the 996 cm −1 phonon is red-shifted. There is a decrease/increase in intensity of the 145 cm −1 phonon at 25 °C/100 °C when NH3 interacts with V2 O5 surface. Using the traditional and quantitative gas sensor tester system, we find that the V2 O5 sensor at 25 °C responds faster than at 100 °C up to 20 ppm of NH3 beyond which it responds faster at 100 °C than at 25 °C. Overall rankings of the NH3 gas sensing features between the two techniques showed that the in situ Raman spectroscopy is faster in response compared with the traditional chemi-resistive tester. Hooke's law, phonon confinement in ~51 nm globular particles with ~20 nm pore size and physisorption/chemisorption principles have been employed in the explanation of the data presented.