Abstract
SnO2 nanocrystals were prepared by precipitation in dodecylamine at 100 °C, then they were reacted with vanadium chloromethoxide in oleic acid at 250 °C. The resulting materials were heat-treated at various temperatures up to 650 °C for thermal stabilization, chemical purification and for studying the overall structural transformations. From the crossed use of various characterization techniques, it emerged that the as-prepared materials were constituted by cassiterite SnO2 nanocrystals with a surface modified by isolated V(IV) oxide species. After heat-treatment at 400 °C, the SnO2 nanocrystals were wrapped by layers composed of vanadium oxide (IV-V mixed oxidation state) and carbon residuals. After heating at 500 °C, only SnO2 cassiterite nanocrystals were obtained, with a mean size of 2.8 nm and wrapped by only V2O5-like species. The samples heat-treated at 500 °C were tested as RhB photodegradation catalysts. At 10−7 M concentration, all RhB was degraded within 1 h of reaction, at a much faster rate than all pure SnO2 materials reported until now.
Highlights
The results of the characterization will be exposed, in order to build up a plausible model of the final material structure, and to show how it is developed from the as-prepared stage through the various heat-treatments, which were necessary for thermal and chemical stabilization of the materials
Rietveld refinement indicated that the mean SnO2 grain size of the pure 400 °C sample was 3.0 ± 0.5 nm, while for SnO2-V2O5 the size did not reach such value even after heating at 500 °C
The collected experimental data pointed to a peculiar structure after heating at 500 °C, with SnO2 nanocrystals embedded into V2O5-like layers
Summary
During the heat-treatment up to 400 °C, the oleic acid ligands are removed to large extent and/or decomposed (FTIR, thermal analyses and XPS), but the more naked surfaces do not favor SnO2 sintering and/or appreciable V migration into the cassiterite structure, not even at high temperatures (XRD data of Fig. 4).
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