Photochemistry of textile azo dyes. Spectral characterization of excited state, reduced and oxidized forms of Acid Orange 7

Vinodgopal, K.; Kamat, Prashant V.

doi:10.1016/1010-6030(94)03810-4

Cited by 88 publications

(49 citation statements)

References 11 publications

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“…At a pH <7, the anion radical of Methyl Orange interacts with TiOH 2 + after the Nacation ionizes in solution [12]. Traces (c) and (d) show a lower The dye molecules adsorbed on the photocatalyst surface are excited by the light photons and produce the singlet excited state, as it has been previously reported by Kamat [13] for Acid Orange 7 and by Kiwi [14] …”

Section: Comparison Of the Photo-discoloration Kinetics Observed Withmentioning

confidence: 53%

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Stabilization mechanism of TiO2 on flexible fluorocarbon films as a functional photocatalyst

Mielczarski¹,

Mielczarski²,

Laub³

et al. 2006

Journal of Molecular Catalysis A: Chemical

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The repetitive discoloration kinetics of the azo-dye Methyl Orange (taken as a model organic compound) was followed under solar simulated radiation (90 mW/cm 2 ) to assess the performance of the TiO 2 /Tedlar ® composite photocatalyst. The influence of solution parameters on the photo-discoloration process: pH, dye concentration, applied light intensity and concentration of H 2 O 2 were systematically investigated. During the photocatalysis a modification occurs in the TiO 2 /Tedlar ® composite due to the TiO 2 interaction with the Tedlar ® film. Physical insight is given for the stabilization mechanism of the TiO 2 particles in the Tedlar matrix based on the data obtained by X-ray photoelectron spectroscopy (XPS). The F 1s peak of the Tedlar film indicates that the TiO 2 is loaded on the Tedlar fluoro-groups. The loading of TiO 2 on the 75 m thick Tedlar ® film was ∼0.9% (w/w) as determined by atomic absorption spectrophotometry (AAS). Attenuated total reflection infrared spectroscopy (ATRIR) shows no formation of additional bands within the photodiscoloration reaction. This shows that an efficient catalysis taking place on the TiO 2 /Tedlar ® surface. The rugosity (mean square roughness, rms) of the TiO 2 /Tedlar ® film was determined by atomic force microscopy (AFM) to be 19.7 nm. This value remained constant during long-term operation. Transmission electron microscopy (TEM) reports the thickness and coverage of TiO 2 Degussa P-25 on the Tedlar ® surface before and after photocatalysis.

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Section: Comparison Of the Photo-discoloration Kinetics Observed Withmentioning

confidence: 53%

“…The photosensitization by Methyl Orange of the TiO 2 /Tedlar leads to the formation of an azo-dye radical cation as documented in the literature [4,13,14]. On thermodynamic grounds Finally, the highest intensity of the N 1s peak at 399.5 eV was found after 3 h reaction.…”

Section: X-ray Photoelectron Spectroscopy (Xps) Of Tio 2 /Tedlar Filmsmentioning

confidence: 65%

Stabilization mechanism of TiO2 on flexible fluorocarbon films as a functional photocatalyst

Mielczarski¹,

Mielczarski²,

Laub³

et al. 2006

Journal of Molecular Catalysis A: Chemical

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“…The mechanism of azo dyes mediated by TiO 2 under light irradiation in the presence of O 2 as oxidant has been reported [12,[19][20][21]. The dye molecules are excited by the light photons and produce the singlet excited state as reported by Vinodgopal and Kamat [19] and by Bandara and Kiwi [20] …”

Section: X-ray Diffraction Measurements (Xrd) Of Parylene/ Tiomentioning

confidence: 92%

Photocatalytic discoloration of Methyl Orange on innovative parylene–TiO2 flexible thin films under simulated sunlight

Zhang

Keppner²,

Laub

et al. 2008

Applied Catalysis B: Environmental

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Parylene films loaded with TiO 2 are reported as photocatalysts in azo dye discoloration processes. The TiO 2 loading of the parylene film was 0.32% (w/w) and the amount of TiO 2 on the film was about two orders of magnitude below the TiO 2 added in suspension to discolore the same solution of Methyl Orange used as a probe. The parylene/TiO 2 films showed a similar activity in the presence of O 2 or H 2 O 2 during the discoloration of dyes. This shows the efficient role of O 2 as e cb À scavenger. The photonic efficiency of the parylene/TiO 2 film during the Methyl Orange discoloration was 0.04. Based on X-ray photoelectron spectroscopy (XPS) data, the TiO 2 particles loaded on the parylene film were shown to be at first encapsulated in the polymer. After the encapsulation is broken, the TiO 2 particles are fully exposed to the dye solution. The lack of surface intermediates like C-residues, N and S-species after the photocatalytic process implies an efficient decomposition of the dye at the catalyst interface. During the dye degradation carbonates and carboxylates were detected by XPS and Fourier transform infrared spectroscopy (FTIR) disappearing at the end of the discoloration process. Evidence is presented during the photocatalysis for the formation of a composite parylene/ TiO 2 film. The formation of this composite involves surface modification of parylene (partial lost of chlorine) in the outermost surface layer with concomitant densification of the TiO 2 particles on the parylene film. The parylene film presented a side with high rugosity and one with low rugosity attaching different amounts of TiO 2 in each case as observed by transmission electron microscopy (TEM). #

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“…This means the formation of surface species with oxidation state Ti(III) and Ti(IV) involving redox processes during the photocatalysis. The origin of the Ti(III) state may be related to photosensitization by Orange II by the LDPE-TiO 2 film and the formation of an azo-dye radical cation (Vinodgopal and Kamat, 1994) with concomitant charge transfer of the electron to TiO 2 e cb -/LDPE or Ti(III) in net sense as shown in Eq. (9) Orange II þ LDPEÀTiO 2 þ hn !…”

Section: X-ray Photoelectron Spectroscopy (Xps) Of Ldpe-tio 2 Filmsmentioning

confidence: 99%

“…The mechanism of azo dye degradation mediated by TiO 2 under light irradiation in the presence of O 2 has been reported and will not be dealt here (Vinodgopal and Kamat, 1994;Bandara and Kiwi, 1999). The dye molecules are excited by the light photons and produce the azo-dye singlet excited state as reported for azo dyes…”

mentioning

confidence: 99%

Preparation, stabilization and characterization of TiO2 on thin polyethylene films (LDPE). Photocatalytic applications

Zhang

Mielczarski

et al. 2007

Water Research

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Photochemistry of textile azo dyes. Spectral characterization of excited state, reduced and oxidized forms of Acid Orange 7

Cited by 88 publications

References 11 publications

Stabilization mechanism of TiO2 on flexible fluorocarbon films as a functional photocatalyst

Stabilization mechanism of TiO2 on flexible fluorocarbon films as a functional photocatalyst

Photocatalytic discoloration of Methyl Orange on innovative parylene–TiO2 flexible thin films under simulated sunlight

Preparation, stabilization and characterization of TiO2 on thin polyethylene films (LDPE). Photocatalytic applications

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