Abstract
In the present report, the generation of Tantalum oxyfluoride and oxynitride upon ammonolysis of the gel obtained from modified tantalum-alkoxo complexes is reported. To the best of our knowledge, this is the first report of the formation of tantalum oxyfluoride thin films via ammonolysis of the β-diketone modified tantalum-alkoxo complex [Ta(OEt)4(CF3COCH2COCH3)]m. The integration of nitrogen and fluorine in lattice sites of metal oxides leads to significant reduction in the bandgap, resulting in their activation under visible light. Moreover, in this report the effect of the modified alkoxide precursors and ammonolysis on the photophysical properties of Ta2O5 thin films have also been investigated and compared with the results obtained from films fabricated from unmodified tantalum (V) ethoxide. 1H NMR, 13C NMR and elemental analyses confirmed successful modification of tantalum (V) ethoxide to [Ta(OCH2CH3)4(CH3COCHClCOCH3)]m (1), [Ta(OCH2CH3)4(CF3COCH2COCH3]m (2) and [Ta(OCH2CH3)4 (CH3COC(CH3)2COCH3))]m (3). The fabrication of Ta2O5 thin films involved the spin casting of the gels of modified tantalum alkoxo complexes (processed by sol–gel method) on to glass substrate. X-ray photoelectron spectroscopy results show that nitrogen was incorporated into the ammonolyzed films fabricated from complex precursors (1) and (3), while the presence of fluorine as tantalum oxyfluoride was confirmed in the ammonolyzed film fabricated from complex (2) precursor. The optical characterization insinuate bandgap narrowing from 3.55 eV for undoped film prepared from tantalum (V) ethoxide to 3.47 eV for undoped film prepared from [Ta(OEt)4(CF3COCH2COCH3)]m and 3.05 eV for ammonolyzed film obtained from [Ta(OEt)4(CF3COCH2COCH3)]m precursor. Furthermore, enhanced photocatalytic efficiency of the films is demonstrated by degradation of methylene blue dye.
Highlights
The discovery of photocatalytic properties of titanium dioxide by Honda-Fujishima paved way for the development of technologies with a huge potential applicability towards environmental remediation such as purification of water via degradation of dyes and pesticides, oxidation of volatile organic compounds and CO2 reduction on various types of photocatalytic materials [1,2,3,4,5,6]
X-ray photoelectron spectroscopy results show that nitrogen was incorporated into the ammonolyzed films fabricated from complex precursors (1) and (3), while the presence of fluorine as tantalum oxyfluoride was confirmed in the ammonolyzed film fabricated from complex (2) precursor
All the films were prepared in duplicate, one set of films was calcined at 500 °C under oxygen flow for 1 hr while the other set of films was subjected to ammonolysis at the same temperature for same duration
Summary
The discovery of photocatalytic properties of titanium dioxide by Honda-Fujishima paved way for the development of technologies with a huge potential applicability towards environmental remediation such as purification of water via degradation of dyes and pesticides, oxidation of volatile organic compounds and CO2 reduction on various types of photocatalytic materials [1,2,3,4,5,6]. Thin films of group V metal oxides (Nb2O5 and Ta2O5) are of significant technological relevance owing to their excellent photophysical properties (comparable to that of benchmark photocatalyst) and favorable chemical, thermal, mechanical properties [11]. They have a number of other potential uses in advanced electronics as high-κ dielectric materials or as diffusion barriers [11,12,13,14,15] Recently, Ta2O5 has been established as a robust memristive material [16,17,18,19]. A comparative investigation of the effect of modified precursors and ammonolysis on structural, optical and photocatalytic properties of sol-gel derived tantalum pentaoxide thin films systematically prepared from β- diketones [3-Chloro-2,4pentanedione, 3,3-Dimethyl-2,4-pentanedione,1,1,1-Trifluoro-2,4pentanedione] substituted tantalum (V) ethoxide precursors has been discussed
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