Optical properties of inhomogeneous media

Joerger, Ralph; Gampp, R.; Heinzel, Andreas; Graf, Wolfgang; Köhl, Michael; Gantenbein, Paul; Oelhafen, P.

doi:10.1016/s0927-0248(98)00086-5

Cited by 34 publications

(15 citation statements)

References 10 publications

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“…10. Although the possible advantages of usage of nanosized gold caused by: decreased the energetic difference between the d-band threshold and the Fermi edge; 41 higher shift in the apparent Fermi level of the TiO 2 -Au composites to more negative potential 42 occurence of a metal-to-nonmetal transition 40b thus gold particles are expected to be semiconducting rather than metallic and a mechanism, based on semiconductorsemiconductor contact (in which photoexcited electrons are injected from gold into the titania CB creating separated electrons and holes which then undergo charge transfer reactions with adsorbates) can be considered; 43 Schottky junction formation (leading to Au-to-TiO 2 electron transfer) 43,44 are well known, our results show that titania modified with gold nanoparticles resulted in much higher  app than did titania modified with nanosized gold. It should be noted that  app is composed of two self-contained parts, i.e., efficiency of absorption and efficiency of electron-hole utilization.…”

Section: Mechanistic Studiesmentioning

confidence: 99%

“…51 If hypothesis (b) is correct, direct deposition of gold on the titania surface (electronic contact) would not be necessary, as LSPR is observed up to tens of nanometers from the gold nanoparticle. 41 However, preliminary 20 results suggest that direct electron transfer from gold to titania as the reaction rate was dramatically decreased by deposition of gold on the modified titania surface. The details will be published in a forthcoming paper.…”

Section: (2)mentioning

confidence: 99%

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Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Kowalska

Mahaney

Abe

et al. 2010

Phys. Chem. Chem. Phys.

518

419

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Fifteen commercial titania (titanium(IV) oxide; TiO 2 ) powders were modified with gold by photodeposition to prepare photocatalysts that work under irradiation with light in the visible range (vis). The gold-modified titania (Au/TiO 2 ) powders were characterized by diffuse reflectance spectroscopy (DRS), field-emission scanning electron microscopy (FE-SEM), scanning transmission microscopy (STEM) and X-ray powder diffraction analysis (XRD). It was shown that all tested powders could absorb visible light with an absorption maximum at localized surface plasmon resonance (LSPR) wavelengths (530-600 nm) and that the size and shape of gold nanoparticles determined absorption ranges.The photocatalytic activity of Au/TiO 2 powders was examined both under ultraviolet and vis irradiation (mainly >450 nm) for acetic acid and 2-propanol photooxidation. It was found that the activity depended strongly on gold and titania properties, such as particle size and shape, surface area and crystalline form. Under vis irradiation, large rutile particles loaded with gold particles of a wide range of sizes showed the highest level of photocatalytic activity, possibly due to greater light absorption ability in a wide wavelength range resulting from transverse and longitudinal LSPR of rod-like gold particles. Action spectrum analyses showed that visible light-induced oxidation of organic compounds by aerated gold-titania suspensions was initiated by excitation of LSPR absorption of gold. Although photocatalytic activity of nanosized gold particles under vis irradiation with a wavelength of ca. 430 nm and catalytic activity of goldmodified titania during dark reaction were also found, it was shown that the activities of 2 Au/TiO 2 particles originated from activation of LSPR of gold by light of wavelength of 530-650 nm. Participation of molecular oxygen as an electron acceptor and titania as a conductor of electrons was suggested by comparison with results obtained under deaerated conditions and results obtained using a system containing gold-deposited silica instead of gold-titania, respectively. On the basis of these results, the mechanism of visible light-induced oxidation of organic compounds on gold-titania is proposed. IntroductionTitanium(IV) oxide (TiO 2 ; titania) is an inexpensive particulate material that is readily available and has substantial photocatalytic activity, stability toward inorganic and organic compounds and non-toxicity. 1 However, one drawback of titania is that it can only be excited by ultraviolet light, i.e., with wavelengths shorter than ca. 400 nm.Therefore, only a very small portion of solar radiation (3-5%) can be utilized to drive chemical reactions. 2 Thus, extension of its absorption wavelength range to the visible region (vis) is an important issue. Another important issue is improvement of quantum efficiency, i.e., an efficiency of utilization of the photoexcited state of photocatalysts, since an electronic excited state of titania is deactivated by recombination of electrons and holes to lower qu...

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Section: Mechanistic Studiesmentioning

confidence: 99%

Section: (2)mentioning

confidence: 99%

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Kowalska

Mahaney

Abe

et al. 2010

Phys. Chem. Chem. Phys.

518

419

View full text Add to dashboard Cite

show abstract

“…Indeed here we consider the case of an ideal system with a fixed composition although carbon concentration decreases from the surface to the bulk in the real case. Nevertheless the use of such an approximation is justified by the effective medium theory and has already been used to predict optical properties of inhomogeneous media [17]. Results for k = 600 nm are shown in Fig.…”

Section: Simulation Of Reflectivity Of Mo X C 1àx Layer On Pure Momentioning

confidence: 99%

Study of optical properties of MoxC1−x films

Temmerman¹,

Ley²,

Boudaden³

et al. 2005

Journal of Nuclear Materials

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“…This reflects on the binding energy and optical properties of the nanoparticles. [21][22][23][24] The binding energy between the nanoparticles and the surface of the CNP was qualitatively estimated by imaging the CNP before and after inserting it into a living cell (HeLa human cancerous cell line). SEM analysis has shown that the nanoparticles remain on the surface of the CNP (data not shown).…”

Section: Functionalization Of Carbonmentioning

confidence: 99%

Effects of Deposition Conditions on the Structure and Chemical Properties of Carbon Nanopipettes

Vitol¹,

Schrlau²,

Bhattacharyya³

et al. 2009

Chemical Vapor Deposition

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Carbon nanopipettes (CNPs) are integrated devices combining a nanometer-size carbon tip with a glass pipette. The carbon tip is produced by catalytic CVD. In this paper, it is demonstrated that the structure of the CNPs can be controlled by varying the synthesis parameters. Increased carbon graphitization is observed as the synthesis temperature increases from 890 8C to 950 8C. A similar effect is achieved by lowering the carbon precursor (methane) concentration from 60% to 20%. Changes in the amount of catalyst do not have a significant effect on the carbon graphitization. At the same time, CNPs with relatively large amounts of hydrogen bonds on the surface are obtained by using a high methane concentration. This finding is used to facilitate the functionalization of the CNPs with gold nanoparticles.

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Optical properties of inhomogeneous media

Cited by 34 publications

References 10 publications

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Visible-light-induced photocatalysis through surface plasmon excitation of gold on titania surfaces

Study of optical properties of MoxC1−x films

Effects of Deposition Conditions on the Structure and Chemical Properties of Carbon Nanopipettes

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