Chromium oxide loaded silica aerogels: Novel visible light photocatalytic materials for environmental remediation

Weerasinghe, Manindu N.; Klabunde, Kenneth J.

doi:10.1016/j.jphotochem.2013.01.002

Cited by 12 publications

(4 citation statements)

References 23 publications

(30 reference statements)

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“…Cr(VI) ions dispersed on oxide (typically, silica or alumina) supports have been the subject of considerable study due, in large part, to their roles as catalyst precursors in commercial Phillips ethylene polymerization and several commercial processes for light alkane dehydrogenation. , In addition, the materials are of interest as photo-oxidation catalysts because of their long excited state lifetimes and absorption in the visible. − Cr(VI)/SiO 2 has been characterized using a variety of spectroscopic techniques, including X-ray absorption spectroscopy (EXAFS and XANES), vibrational spectroscopies (Raman, resonance-Raman, and IR), and diffuse reflectance electronic spectroscopy. − Many studies have attempted to use UV–vis spectroscopy to distinguish different types of Cr sites as a function of loading. In particular, as the Cr loading increases, specific bands emerge that have been assigned to oligomeric species such as dichromates, Figure , as well as Cr 2 O 3 crystallites …”

Section: Introductionmentioning

confidence: 99%

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

et al. 2018

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The electronic structure of isolated Cr(VI) sites supported on silica was reinvestigated using multiple, complementary electronic spectroscopies applied to transparent xerogel monoliths. The absorption spectrum exhibits three previously reported peaks, at 22 800, 29 100, and 41 500 cm–1, as well as a previously unresolved band at ca. 36 900 cm–1. The emission is a long-lived red luminescence with λmax = 13 600 cm–1, emanating from the lowest excited state. Assignment of the excited states was facilitated using time-dependent density functional theory (TD-DFT) calculations performed on cluster models. All of the observed electronic transitions and their energies are accounted for by dioxoCr(VI) sites. The lowest energy observed excitation at 22 800 cm–1 populates a singlet excited state, while the emitting state is the corresponding triplet state, accessed by intersystem crossing from the singlet state. Spectroscopic bands observed at 29 100, 36 900, and 41 500 cm–1 were assigned, based on the TD-DFT calculation, to spin-allowed transitions that are consistent with emission polarization anisotropy measurements. Small variations in site symmetry at Cr result principally in inhomogeneous broadening of the spectral bands, as well as a red-edge effect in the photoemission spectrum. There is no evidence for a significant contribution from five-coordinate mono-oxoCr(VI) sites.

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Section: Introductionmentioning

confidence: 99%

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

et al. 2018

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“…Besides, Liu et al 7 introduced the manufacturing process of carbon foam (CF)/silica aerogel composites under conventional drying. The prepared composite had an average density value of around 0.43 g/cm 3 , while the ultimate compressive strength was nearly 10.17 MPa which was relatively high. At present, tremendous attention was paid to the enhancement effect on silica aerogel matrix composites doped with fibers.…”

Section: Introductionmentioning

confidence: 97%

“…Silica aerogel, a porous material which could dramatically change the world, had been applied in many industries such as adsorption, catalytic supports, catalysis, drug delivery, and thermal insulation. [1][2][3][4] However, the pure silica aerogels suffered from low mechanical robustness and high brittleness, which greatly limited their wide range of applications. Recently, many researchers put their effort into modifying the silica aerogel composite to improve the mechanical strength without sacrificing the thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

Mechanical and thermal properties of reticulated SiC aerogel composite prepared by template method

Chen

et al. 2019

Journal of Composite Materials

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A novel structure-controllable reticulated silicon carbide (SiC) skeleton-reinforced silica aerogel composites (SiC/aerogel) were fabricated successfully by template method. Three-dimensional SiC skeletons prepared by different deposition time were prepared via the chemical vapor deposition technology, and then the silica aerogel was induced by the sol–gel process. The test results showed that the mechanical properties increased and thermal conductivities decreased remarkably after impregnating reticulated SiC skeleton with silica aerogel. The SiC/aerogel-24 possessed the highest compressive strength of 0.82 MPa with the thermal conductivity of 0.1597 W/(m·K) at 600℃, while the SiC/aerogel-12 exhibited the lowest thermal conductivity of 0.1244 W/(m·K) and its compressive strength was 0.64 MPa. The present work reported a novel method to manufacture the structure-controllable reticulated SiC aerogel composite which could be used as a high-temperature super-thermal insulation material for the potential applications.

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“…These materials, which exhibit porosity between 95 and 99%, are comprised of a mesoporous nanostructure of interconnected particles having unique characteristics, such as high surface area, low density, and low thermal conductivity [1,2]. Various strategies have been used to develop composites of silica aerogels with a variety of dispersed nanostructures, such as TiO 2 , Pt, Au, RuO 2 , SnO 2 , and carbon nanotubes [3][4][5]. Therefore, it is possible to design new materials for a given application, combining the properties of silica aerogel with the desirable properties of the embedded material.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Conductive PPy/SiO₂ Aerogels Nanocomposites by In Situ Polymerization of Pyrrole

Müller

Pinheiro

Bendo

et al. 2015

Journal of Nanomaterials

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Electrical conductive nanocomposite aerogels were synthesized throughin situoxidative polymerization of pyrrole (Py) using ammonium persulfate (APS) as an oxidizing agent in SiO2gels. The effect of Py concentration on the electrical conductivity and physical and morphological properties of aerogels SiO2/PPy was evaluated. B.E.T. analysis indicated that the surface area of the composite SiO2/PPy decreases with increasing concentration of Py. CHN analysis showed an increase in the amount of PPy, from 13 wt.% to 23 wt.%, with increasing concentration of pyrrole synthesis. FTIR-ATR analysis of the composites revealed bands in the region of 1500–1400 cm−1, indicating the presence of the conductive polymer in the silica aerogel as well as the characteristic bands of Si-O-Si and Si-OH covalent bonds. TEM micrographs revealed the presence of particles of PPy with the increased size of the nanoparticles. The composites were successfully applied as passive components, in RC circuits, for low-pass frequency filters. The filters exhibited a cutoff frequency at approximately 435 Hz. The aerogels obtained in this work exhibited suitable electrical conductivity for use in various other applications in electronics.

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Chromium oxide loaded silica aerogels: Novel visible light photocatalytic materials for environmental remediation

Cited by 12 publications

References 23 publications

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

Mechanical and thermal properties of reticulated SiC aerogel composite prepared by template method

Synthesis of Conductive PPy/SiO₂ Aerogels Nanocomposites by In Situ Polymerization of Pyrrole

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Chromium oxide loaded silica aerogels: Novel visible light photocatalytic materials for environmental remediation

Cited by 12 publications

References 23 publications

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

Reassessment of the Electronic Structure of Cr(VI) Sites Supported on Amorphous Silica and Implications for Cr Coordination Number

Mechanical and thermal properties of reticulated SiC aerogel composite prepared by template method

Synthesis of Conductive PPy/SiO2 Aerogels Nanocomposites by In Situ Polymerization of Pyrrole

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Synthesis of Conductive PPy/SiO₂ Aerogels Nanocomposites by In Situ Polymerization of Pyrrole