Photocatalytic performance of combustion-synthesized β and γ-Ga2O3 in the degradation of 1,4-dioxane in aqueous solution

Seshadri, H.; Cheralathan, M.; Sinha, Pranay Kumar

doi:10.1007/s11164-012-0610-1

Cited by 21 publications

(15 citation statements)

References 27 publications

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“…7−9 γ-Ga 2 O 3 has itself been studied for various applications in catalysis and compared with other Ga 2 O 3 polymorphs; for example, in the steam reforming of methanol 10 and the photocatalytic degradation of volatile organics. 11,12 Recently Lueangchaichaweng et al have reported the use of gallium oxide nanorods, largely the γ polymorph, as highly effective catalysts for epoxidation reactions of alkenes. 13 Interesting optical properties have also been a focus of recent attention for γ-Ga 2 O 3 : Chen et al described the formation of quantum dots with blue-green photoluminescence, 14 which Wang et al showed was particle-size controllable 15−17 and could be enhanced by inducing defects under reductive conditions.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The catalytic chemistry of γ-Al 2 O 3 has been widely investigated, and indeed its use as a catalyst support is commonplace . The solid solution γ-Ga 2 O 3 –γ-Al 2 O 3 has also been investigated for specific catalysis applications, and it is believed that preferential occupation of the tetrahedral sites by gallium leads to unique properties for the surface aluminum, such as in methane-selective catalytic reduction of NO, − and in the dehydrogenation of propene. − γ-Ga 2 O 3 has itself been studied for various applications in catalysis and compared with other Ga 2 O 3 polymorphs; for example, in the steam reforming of methanol and the photocatalytic degradation of volatile organics. , Recently Lueangchaichaweng et al have reported the use of gallium oxide nanorods, largely the γ polymorph, as highly effective catalysts for epoxidation reactions of alkenes . Interesting optical properties have also been a focus of recent attention for γ-Ga 2 O 3 : Chen et al.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Structural Disorder in γ-Ga₂O₃

et al. 2014

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Solvothermal oxidation of metallic gallium in monoethanolamine for 72 h at 240 °C yields a crystalline sample of γ-Ga 2 O 3 (∼30 nm crystallites). While Rietveld refinement (cubic spinel structure, Fd3̅ m; a = 8.23760(9) Å) reveals that Ga occupies two pairs of octahedral and tetrahedral sites (ideal spinel and nonspinel), it provides no information about their local distribution, which cannot be statistical owing to the short Ga−Ga contacts produced if neighboring ideal spinel and nonspinel sites are simultaneously occupied. To create an atomistic model to reconcile this situation, a 6 × 6 × 6 supercell of the crystal structure is constructed and refined against neutron total scattering data using a reverse Monte Carlo (RMC) approach. This accounts well for the local as well as long-range structure and reveals significant local distortion in the octahedral sites that resembles the structure of thermodynamically stable β-Ga 2 O 3 . 71 Ga solid-state NMR results reveal a octahedral:tetrahedral Ga ratio that is consistent with the model obtained from RMC. Nanocrystalline samples of γ-Ga 2 O 3 are produced by either a short solvothermal reaction (240 °C for 11 h in diethanolamine; ∼15 nm crystallites) or by precipitation from an ethanolic solution of gallium nitrate (∼5 nm crystallites). For these samples, the Bragg scattering profile is broadened by their smaller crystallite size, consistent with transmission electron microscopy results, and analysis of the relative Bragg peak intensities provides evidence that a greater proportion of tetrahedral versus octahedral sites are filled. In contrast, neutron total scattering shows the same average Ga−O distance with decreasing particle size, consistent with 71 Ga solid-state NMR results that indicate that all samples contain the same overall proportion of octahedral:tetrahedral Ga. It is postulated that increased occupation of tetrahedral sites within the smaller crystallites is balanced by an increased proportion of octahedral surface Ga sites, owing to termination by bound solvent or hydroxide.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterization of Structural Disorder in γ-Ga₂O₃

et al. 2014

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“…The nature of the remaining line at 231 cm –1 has not yet been clarified. It corresponds neither to the α-Ga 2 O 3 phase nor to the γ-Ga 2 O 3 or ε-Ga 2 O 3 phase . As a result, the presence of these allotropic phases in the microrods after thermal treatment is excluded.…”

Section: Resultsmentioning

confidence: 99%

Chemical Synthesis of β-Ga₂O₃ Microrods on Silicon and Its Dependence on the Gallium Nitrate Concentration

et al. 2020

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β-Ga 2 O 3 microrods have received in the last years an increasing interest for their integration into solar blind / UV photodetectors and gas sensors. However, their synthesis using a low temperature chemical route in aqueous solution is still under development and the physicochemical processes at work have not been elucidated yet. Here, we develop a double-step process involving the growth of α-GaOOH microrods on silicon using chemical bath deposition and their further structural conversion into β-Ga 2 O 3 microrods by post-deposition thermal treatment. It is revealed that the concentration of gallium nitrate has a drastic effect to tune the morphology, dimensions (i.e. diameter and length), and density of α-GaOOH microrods over a broad range, governing in turn the morphological properties of β-Ga 2 O 3 microrods. The physicochemical processes in aqueous solution are investigated by thermodynamic computations yielding speciation diagrams of Ga(III) species and theoretical solubility plots of GaOOH(s). In particular, the qualitative evolution of the morphological properties of α-GaOOH microrods with the concentration of gallium nitrate is found to be correlated with the supersaturation in the bath and discussed in the light of the standard nucleation and growth theory. Interestingly, the structural conversion following the thermal treatment at 900 °C in air results in the formation of pure β-Ga 2 O 3 microrods without any residual minor phases and with tunable morphology and improved structural ordering. These findings reporting a double-step process to form high quality pure β-Ga 2 O 3 microrods on silicon open many perspectives for their integration onto a large number of substrates for solar blind / UV photo-detection and gas sensing.

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“…31 The peak at 418 cm −1 can be the A 1g phonon of the sapphire substrate and/or the GaN phonon mode because both can appear at the same frequency. 31 It should be noted that the characteristic peaks of γ-Ga 2 O 3 located at 647 and 768 cm −1 were not found, 32 indicating that the oxygen composition inside the GaN:Zn(4) CQD nanocrystal lattice is negligible. The EDS mapping result (Figure 4, Figure S14, and Table S2) in conjunction with the XPS result suggests that the zinc dopants are likely to be on the surface of the nanocrystal.…”

Section: Chemistry Of Materialsmentioning

confidence: 99%