Dependence of the Work Function of TiO<sub>2</sub> (Rutile) on Crystal Faces, Studied by a Scanning Auger Microprobe

Imanishi, Akihito; Tsuji, Etsushi; Nakato, Yoshihiro

doi:10.1021/jp0668403

Cited by 130 publications

(117 citation statements)

References 32 publications

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“…The barrier height could theoretically be calculated from the electron affi nity of rutile TiO 2 (100) and the work function of Au(111). Since the reported values for the former [ 26,27 ] and the latter [ 28 ] are 4.08 and 5.31 eV, respectively, the theoretical barrier height is calculated to be 1.23 eV. The difference between the calculated and experimentally obtained values could be explained in terms of the difference between the surface in vacuum and the epitaxial interface with a certain mismatch.…”

Section: Doi: 101002/admi201400066mentioning

confidence: 90%

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

Kazuma

Tatsuma

2014

Adv Materials Inter

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Nb-doped rutile TiO 2 (100), unless otherwise noted) in the presence of a Na [AuCl 4 ] aqueous solution mixed with ethanol (refer to SI for details of the experiments). Electrons in the TiO 2 valence band (VB) are excited by UV light to the conduction band (CB), and holes are generated in the VB. Au 3+ ions are reduced to Au NPs by the excited electrons, and ethanol, a sacrifi cial electron donor, is oxidized by the holes simultaneously. In addiation to polydisperse spheroids (diameter ≈20-110 nm, height/diameter ≈0.5), truncated triangular nanoplates (sides ≈60-280 nm, height ≈7-16 nm) consisting mainly of Au(111) faces were deposited ( Figures 1 a, S2a). Similar NPs were also deposited on a non-doped rutile TiO 2 (100) ( Figure S2b) and the NPs exhibited LSPR-based extinction in the visible and NIR regions (500-1600 nm) ( Figure S2c).We evaluated photoinduced surface potential changes of the sample with KFM (Nanonavi Station/E-sweep, SII Nanotechnology) in non-contact mode at a scan rate of ≈0.5−1.0 Hz by using a gold-coated silicon cantilever (SI-DF3-A, SII Nanotechnology) with a normal spring constant of 3 N m −1 and tip curvature radius of 30 nm. Tip was scanned at a constant distance (10 nm) from the sample surface. The sample was irradiated with s-polarized light, and the incident angle was 45°. Measurements were performed in a closed KFM chamber after the chamber was degassed (≤3.0 Pa) and refi lled with dry N 2 gas (including 0.3 ppm O 2 and 1.0 ppm H 2 O) until atmospheric pressure was reached, to avoid dissociation of oxygen from the TiO 2 surface under high vacuum.[ 20 ] In a KFM measurement, an offset bias voltage ( V off ) is applied between the sample and the tip so as to cancel out the electrostatic force between them. The surface potential of the sample vs. tip ( E sample vs. tip ) equals − V off . In the present work, the potential of a clean Pt plate vs. tip ( E Pt vs. tip ) is measured and the potential of the sample surface is reported in reference to that of Pt ( E sample = E sample vs. tip -E Pt vs. tip ). Incidentally, E Pt vs. tip was not changed by light irradiation, suggesting that the photoinduced potential change of the tip was negligible. On the basis of a fi nite-difference time-domain (FDTD) calculations, LSPR of the KFM tip is excited only in the 400−600 nm region. Therefore, the results for TiO 2 excitation by UV light and Au nanoplate excitation by NIR light are not affected by the tip plasmon. In addition, electric fi eld is not localized at the tip under s-polarized light, and it is known that PICS occurs at sites where electric fi eld is localized. [ 15,16 ] When the TiO 2 substrate without Au NPs was excited by 310 nm UV light from a Hg-Xe lamp (0.48 mW cm −2 ), the surface potential of TiO 2 ( E TiO2 ) shifted uniformly by about +280 mV ( Figure S3), whereas topographic images remained unchanged. Since the average exciton lifetime in TiO 2 (<1 ns) [ 21 ] is much shorter than the average interval of photon incidence (13 μs even for a 10 4 nm 2 region), the observed potentia...

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Section: Doi: 101002/admi201400066mentioning

confidence: 90%

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

Kazuma

Tatsuma

2014

Adv Materials Inter

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“…An alternative UC of the composite was also considered, where the zigzag line of graphene runs parallel to the A cell vector of rutile (110). Here the smallest identi ed commensurate unit cell ( commensurate de ned here as having mismatch under 5%) comprised of an 8 × 5…”

Section: Unit Cell Constructionmentioning

confidence: 99%

Electronic Structure and Charge Transfer in the TiO₂ Rutile (110)/Graphene Composite Using Hybrid DFT Calculations

Gillespie

Martsinovich

2017

J. Phys. Chem. C

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Composite systems of TiO 2 with nanocarbon materials, such as graphene, graphene oxide and carbon nanotubes, have proven to be e cient photocatalyst materials. However, detailed understanding of their electronic structure and the mechanisms of the charge transfer processes is still lacking. Here, we use hybrid density functional theory calculations to analyse the electronic properties of the ideal rutile (110)-graphene interface, in order to understand experimentally observed trends in photoinduced charge transfer. We show that the potential energy surface of pristine graphene physisorbed above rutile (110) is relatively at, enabling many possible positions of graphene above the rutile (110) surface. We verify that tensile and compressive strain has negligible e ect on the electronic properties of graphene at low levels of strain. By analysing the band structure of this composite material and the composition of the valence and conduction band edges, we show that both the highest occupied states and the lowest unoccupied states of this composite are dominated by graphene, and that there is also a signi cant contribution of Ti orbitals to the two lowest unoccupied bands. We suggest that a transition from graphene-dominated occupied bands to mixed graphene and TiO 2 -based unoccupied bands is responsible for the experimentally observed photoinduced charge transfer from graphene to TiO 2 under visible light irradiation; however, the most stable state for an excess (e.g. photoexcited) electron is localised on the carbon orbitals, which make up the lowest-energy conduction band. This separation of photogenerated electrons and holes makes TiO 2 -graphene an e cient photocatalyst material.

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“…Zakres natężeń wysokich pól elektrycznych (emisji polowej) jest od dołu ograniczony natężeniem krytycznego pola elektrycznego Eth (threshold field), powyżej którego zaczyna się przewaga emisji polowej i możliwe jest wykreślenie prostej F-N. Parametry prostej: nachylenie i rzędna stanowią podstawę do wyliczenia wartości współ-czynników wzmocnienia pola elektrycznego β i powierzchni emisyjnej α. Parametry emisyjne wszystkich emiterów zestawiono w tabeli II. Dla wszystkich obliczeń przyjęto pracę wyjścia rutylu (TiO2) równą φ = 4,2 eV [12]. Niestabilna emisja Ślady na anodzie Duże prądy *Eth-krytyczne natężenie pola elektrycznego, β -współczynnik wzmocnienia pola elektrycznego, α -powierzchnia emisyjna.…”

Section: Charakterystyki Emisyjne I = F(e)unclassified

Wpływ przygotowania powierzchni na elektronową emisję polową powłok TiO2 natryskanych plazmowo z zawiesin

Znamirowski

Kozerski

Łatka

et al. 2015

Przegląd Spawalnictwa

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StreszczenieW pracy badano elektronową emisję polową z powłok TiO2 na podłożach ze stali austenitycznej. Powłoki natryskiwano plazmowo z użyciem zawiesin. Zawiesiny sporządzano na bazie mieszaniny alkoholu etylowego 50% i wody 50%. Powierzchnie próbek toczono lub poddawano obróbce strumieniowo-ściernej. Stwierdzono, że emitery polowe natryskane na powierzchnie poddane wcześniej obróbce strumieniowo-ściernej charakteryzują się lepszą stabilnością emisji elektronowej.Słowa kluczowe: natryskiwanie plazmowe z zawiesin; powłoki TiO2; mikrostruktura; elektronowa emisja polowa AbstractThe electron field emission of TiO2 coatings on substrates made of austenitic steel has been investigated. Plasma sprayed coatings using suspensions. The suspensions were prepared based on a mixture of 50% ethyl alcohol and 50% water. The surfaces of the samples machined or subjected to abrasive blasting. It has been found that the field emitters been sprayed onto the surface before blasting, they have better stability of electron emission.Keywords: suspension plasma spraying, TiO2 coatings, microstructure, field electron emission WstępNatryskiwanie plazmowe z użyciem zawiesin (ang. suspension plasma spraying), SPS, jest badane i stosowane w ostatnich latach szczególnie intensywnie ze względu na interesujące własności powłok jakie można uzyskać przy użyciu tej metody. Metoda ta polega na użyciu ciekłej zawiesiny proszku jako materiału dodatkowego i umożliwia stosowanie proszku o wymiarach submikronowych lub nanometrycznych. Faza ciekła służy jako medium transportujące bardzo drobne cząsteczki proszku i pozwala na wprowadzenie ich w centralną część strumienia plazmy. Schemat procesu SPS przedstawia rysunek 1.Transport i podawanie zawiesiny może być realizowane przez różne układy. Najczęściej wykorzystuje się prosty i tani system pneumatyczny, w którym prędkość wstrzeliwania zawiesiny kontroluje się poprzez wartość ciśnienia sprężonego powietrza (rys. 1). Z kolei zastosowanie pomp perystaltycznych wymaga użycia sterowników elektronicznych, jednak jest bardziej precyzyjne oraz daje możliwość wykonania powłok gradientowych [1].Powłoki natryskiwane plazmowo z zawiesin, w porówna-niu do konwencjonalnych odpowiedników charakteryzują

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Dependence of the Work Function of TiO₂ (Rutile) on Crystal Faces, Studied by a Scanning Auger Microprobe

Cited by 130 publications

References 32 publications

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

Electronic Structure and Charge Transfer in the TiO₂ Rutile (110)/Graphene Composite Using Hybrid DFT Calculations

Wpływ przygotowania powierzchni na elektronową emisję polową powłok TiO2 natryskanych plazmowo z zawiesin

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Dependence of the Work Function of TiO2 (Rutile) on Crystal Faces, Studied by a Scanning Auger Microprobe

Cited by 130 publications

References 32 publications

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO2 Interface

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO2 Interface

Electronic Structure and Charge Transfer in the TiO2 Rutile (110)/Graphene Composite Using Hybrid DFT Calculations

Wpływ przygotowania powierzchni na elektronową emisję polową powłok TiO2 natryskanych plazmowo z zawiesin

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Dependence of the Work Function of TiO₂ (Rutile) on Crystal Faces, Studied by a Scanning Auger Microprobe

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

In Situ Nanoimaging of Photoinduced Charge Separation at the Plasmonic Au Nanoparticle‐TiO₂ Interface

Electronic Structure and Charge Transfer in the TiO₂ Rutile (110)/Graphene Composite Using Hybrid DFT Calculations