Ultraviolet excitation of photoconductivity in thin films of sol–gel SnO2

Geraldo, Viviany; Scalvi, Luís Vicente de Andrade; Morais, Evandro Augusto de; Santilli, Celso Valentim; Miranda, Paulo B.; Pereira, T. J.

doi:10.1016/j.jeurceramsoc.2005.03.149

Cited by 15 publications

(11 citation statements)

References 13 publications

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“…Figure 2 depicts an example of reduction-oxidation processes occurring in a photocatalytic process, in the presence of water and oxygen. The formation of active species responsible [9] Red Bi 2 O 3 2.7 [10] Yellow TiO 2 (rutile) 3.1 [11] White TiO 2 (anatase) 3.2 [12] White ZnO 3.2 [13] White SnO 2 3.8 [14] Grey…”

Section: Type Of Em Radiationmentioning

confidence: 99%

Development and potential of new generation photocatalytic systems for air pollution abatement: an overview

Lim¹,

Zhou²,

Wang³

et al. 2009

Asia-Pacific J Chem Eng

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Photocatalysis is the process by which various undesired substrates are reduced or oxidised on the surface of a photoresponsive material when exposed to a sufficiently energetic irradiation source. Together with other processes like photolysis and ozonation, photocatalysis forms a larger, important group of technologies known as Advanced Oxidation Processes or AOPs.This short review begins with an introduction to the fundamental processes and entities involved in general semiconductor photocatalysis. Various major air pollutants are considered, along with their health effects and traditional means of abatement. Recent advances in photocatalytic materials (including the use of novel materials other then titania), together with heterogeneous photoreactor design (in particular, of the flow-type) are then described. Concluding remarks are included, along with some recommendations for possible future work. 

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Section: Type Of Em Radiationmentioning

confidence: 99%

Development and potential of new generation photocatalytic systems for air pollution abatement: an overview

Lim¹,

Zhou²,

Wang³

et al. 2009

Asia-Pacific J Chem Eng

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“…[2][3][4][5][6] To satisfy the requirements of this wide field of applications, growing efforts have been made on the preparation of ATO films by using the sol-gel process. [5][6][7][8][9][10][11][12][13][14] This process has the advantages of making possible ͑i͒ coatings on large areas with an easy control of the doping level and ͑ii͒ achieving a good homogeneity without using expensive and complex equipment when compared with other film deposition techniques.…”

Section: Introductionmentioning

confidence: 99%

“…Such accessible internal nanoporosity is desirable for surface reactions of adsorbed species, thus improving the sensitivity of the SnO 2 -based gas sensor, 4 and allows for the creation of a microelectrochemical reactor chamber for specific electrocatalytic transformations, while the transparency of the final material provides the opportunity for tunable optical display devices. 5,14 Because of this nanosized nature of the pore structure, the lowest value of the resistivity of sol-gel derived ATO films exceeds by more than 1 order of magnitude those obtained by other deposition methods. [6][7][8][9][10][11][12] There are many experimental evidences indicating that the addition of group V elements, that are used as electron donor doping in order to increase the conductivity of SnO 2 -based materials, affects also the film nanostructure and its stability upon firing.…”

Section: Introductionmentioning

confidence: 99%

Dynamical scaling properties of nanoporous undoped and Sb-dopedSnO2supported thin films during tri- and bidimensional structure coarsening

et al. 2007

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The coarsening of the nanoporous structure developed in undoped and 3% Sb-doped SnO 2 sol-gel dip-coated films deposited on a mica substrate was studied by time-resolved small-angle x-ray scattering ͑SAXS͒ during in situ isothermal treatments at 450 and 650°C. The time dependence of the structure function derived from the experimental SAXS data is in reasonable agreement with the predictions of the statistical theory of dynamical scaling, thus suggesting that the coarsening process in the studied nanoporous structures exhibits dynamical self-similar properties. The kinetic exponents of the power time dependence of the characteristic scaling length of undoped SnO 2 and 3% Sb-doped SnO 2 films are similar ͑␣ Ϸ 0.09͒, this value being invariant with respect to the firing temperature. In the case of undoped SnO 2 films, another kinetic exponent, ␣Ј, corresponding to the maximum of the structure function was determined to be approximately equal to three times the value of the exponent ␣, as expected for the random tridimensional coarsening process in the dynamical scaling regime. Instead, for 3% Sb-doped SnO 2 films fired at 650°C, we have determined that ␣Ј Ϸ 2␣, thus suggesting a bidimensional coarsening of the porous structure. The analyses of the dynamical scaling functions and their asymptotic behavior at high q ͑q being the modulus of the scattering vector͒ provided additional evidence for the two-dimensional features of the pore structure of 3% Sb-doped SnO 2 films. The presented experimental results support the hypotheses of the validity of the dynamic scaling concept to describe the coarsening process in anisotropic nanoporous systems.

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“…As shown in this paper, crystallites generated by our sol-gel dip-coating route have nanoscopic dimensions. Therefore a considerable amount of crystallites is present in the material, which makes electron scattering at grain boundaries the most relevant mechanism to the film conductivity 13,14 . The physics of electronic conduction in these films is peculiar and rather unknown.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

et al. 2010

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The absorption edge and the bandgap transition of sol-gel-dip-coating SnO2 thin films, deposited on quartz substrates, are evaluated from optical absorption data and temperature dependent photoconductivity spectra. Structural properties of these films help the interpretation of bandgap transition nature, since the obtained nanosized dimensions of crystallites are determinant on dominant growth direction and, thus, absorption energy. Electronic properties of the bulk and (110) and (101) surfaces are also presented, calculated by means of density functional theory applied to periodic calculations at B3LYP hybrid functional level. Experimentally obtained absorption edge is compared to the calculated energy band diagrams of bulk and (110) and (101) surfaces. The overall calculated electronic properties in conjunction with structural and electro-optical experimental data suggest that the nature of the bandgap transition is related to a combined effect of bulk and (101) surface, which presents direct bandgap transition

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Ultraviolet excitation of photoconductivity in thin films of sol–gel SnO2

Cited by 15 publications

References 13 publications

Development and potential of new generation photocatalytic systems for air pollution abatement: an overview

Development and potential of new generation photocatalytic systems for air pollution abatement: an overview

Dynamical scaling properties of nanoporous undoped and Sb-dopedSnO2supported thin films during tri- and bidimensional structure coarsening

Evaluation of bulk and surfaces absorption edge energy of sol-gel-dip-coating SnO2 thin films

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