Role of Oxygen Vacancy Sites on the Temperature-Dependent Photoluminescence of SnO₂ Nanowires

Abstract

The role of oxygen vacancies in temperature-dependent photoluminescence of SnO2 nanowires was investigated by X-ray absorption spectroscopy. Two types of oxygen vacancies are present in the nanowires: at out-of-plane sites and at in-plane sites; both play crucial roles in the temperature dependence of the photoluminescence. Oxygen vacancies at in-plane sites participate in photon emission at low temperature, whereas those at out-of-plane sites result in photoluminescence at room temperature. Accordingly, the luminescence color changes from orange (630 nm, 1.93 eV) to green (515 nm, 2.4 eV) at 100 K. The color change is accompanied with a notable change in the oxygen K-edge X-ray absorption spectra. The scanning transmission X-ray microscopy results indicate that more oxygen vacancies at in-plane sites are present in the surface region than in the bulk region, whereas more oxygen vacancies at out-of-plane sites are present in the bulk region than in the surface region. Overall, the results demonstrate that oxygen-vacancy-mediated fluorescence properties of SnO2 nanowires are temperature-dependent; i.e., the photoluminescence mechanisms of the nanowires are mediated by oxygen vacancies at different sites, and the bicolor fluorescence originates from charge transfer between the states.

Stabilizing Oxidation State of SnO2 for Highly Selective CO2 Electroreduction to Formate at Large Current Densities

“…In addition, it is inevitable that the chemical structures of electrocatalysts are restructured with the reduction potential increasing during CO 2 RR tests . To probe this change, the Raman spectra of pre-catalysts after electro-reduction under the CO 2 RR condition (−0.8 V RHE in CO 2 -saturated 0.1 M KHCO 3 electrolyte for 720 s) reveal that the A 1g peak associated with the Sn–O bond is well reserved in Cu–SnO 2 , while it is largely weakened in Bi-, Pt–SnO 2 , and pure SnO 2 (Figure d) . Also, as shown in Figure e, the amount of O v in Cu–SnO 2 is obviously more than that in pure SnO 2 after CO 2 RR.…”

“…We further used isotope D 2 O electrolyte to confirm that the 1630 cm –2 peak corresponds to H 2 O only for Cu–SnO 2 but associates with both H 2 O and CO 2 RR intermediate *COOH for SnO 2 (Figure a). − More importantly, the peak at 1400 cm –2 on Cu–SnO 2 can be assigned to the OCHO* species, which is the key intermediate for formate formation. ,, In addition, Bi substitution induces a similar adsorption effect to Cu–SnO 2 , and Pt substitution can adsorb little *OCHO only at high cathodic potentials and display an intermediate adsorption ability more like pure SnO 2 (Figures S22c,d and S23). In in situ Raman spectroscopy, the peak located at 630 cm –1 ascribed to A 1g modes of the Sn–O bond can be a response to the oxidation state of SnO 2 . Clearly, this peak can be detected in this series of catalysts under cathodic potentials below −0.6 V RHE ; nevertheless, if the cathodic potential increases further, this peak then gradually disappears in pure SnO 2 , Bi–SnO 2 , and Pt–SnO 2 samples (Figures b and S24).…”

Green Biosynthesis of Tin Oxide Nanomaterials Mediated by Agro-Waste Cotton Boll Peel Extracts for the Remediation of Environmental Pollutant Dyes

“… 6 Among various nanomaterials, SnO 2 nanomaterials are considered an alternative source for degradation of water purification/environmental pollutants because they possess outstanding UV light absorption and generate reactive oxygen species (ROS) that lead to the degradation of environment pollutant dye molecules. 7 , 8 …”

“…Moreover, green synthesized nanomaterials are gaining interest in the research fields, environmental sciences, synthetic chemistry, nanobiotechnology, and material chemistry, respectively . Among various nanomaterials, SnO 2 nanomaterials are considered an alternative source for degradation of water purification/environmental pollutants because they possess outstanding UV light absorption and generate reactive oxygen species (ROS) that lead to the degradation of environment pollutant dye molecules. , …”

“…6 Among various nanomaterials, SnO 2 nanomaterials are considered an alternative source for degradation of water purification/environmental pollutants because they possess outstanding UV light absorption and generate reactive oxygen species (ROS) that lead to the degradation of environment pollutant dye molecules. 7,8 Tin oxide nanoparticles (SnO 2 NPs) are widely used in several fields such as photocatalytic activity, energy storage application, and organic transformation used as catalysts in various fields. 9 The literature reports the synthesis of SnO 2 NPs (SNPs) through multiple methods.…”