TiO2 monolayer

Ishibashi, T, Uetsuka, H. and Onishi, H. (2004) An ordered retinoate monolayer prepared on rutile TiO2(110)./. Phys. Chem. B, 108, 17166-17170. 

The performance of the three sensitizers 22,8 and 56, which contain different degrees of protonation were studied on nanocrystalline TiO2 electrodes [80]. Figure 13 show the photocurrent action spectra obtained with a monolayer of these complexes coated on TiO2 films. 

The TiO2(110) surface can be modified to alter the surface chemistry of adsorbed methoxides. Recently Vohs et al. [73] have reported temperature programmed desorption studies of methanol on TiO2(110)-supported V2O5. Deposited monolayer films of vanadia converted some of the adsorbed methanol to formaldehyde and water, while multilayer films of vanadia on the TiO2(110) surface were found to be inactive for methanol oxidation. Furthermore, adsorption studies of formaldehyde indicated that formaldehyde production from... 

Since the parallel components of the dynamic dipole are active in RAIRS, it is possible to use the azimuthal dependence to obtain the orientation of the adsorbate at the surface. A similar technique has been applied to adsorbates on metals in HREELS measurements made off specular in order to observe parallel modes through impact or resonant scattering processes. This was first demonstrated for the Rh(CO)2 molecule on anisotropic TiO2(110) surface [72]. The results of this study also allow a test of the three layer model theory (Fig.5,6) as applied to S-polarised radiation. Fig. 11 shows the FT-RAIRS spectrum for 1/3 monolayer of Rh(CO)2 on Ti02(l 10) measured with P and S polarised radiation. 

The n-Si(100)/TiO2-St/ITO heterostructural cell appears to have two interfaces, w-Si(100)/TiO2-St and TiOj-St/ITO. This double-junction model can be represented by the equivalent circuit in terms of a pair of tunnel capacitors (Rl, Cl R2, C2) in series [12]. A schematic diagram of the Si(100)/TiO, St/ITO heterostructures is shown in Fig. 7. We have measured the SPS of the n-type and p-type silicon substrate with a TiOj-St LB monolayer (Fig. 6) deposited. In an -Si(100)/TiO2-St/ITO cell, the electrostatic potentials has the same orientation whether the junction is from an interface of i-Si(100)/TiO2-St or Ti02-St/IT0, and the electrostatic potential should be increased in the series Cl and C2, which causes enhancement of SPS. The SPS of four heterostructural cells are shown in Fig. 6. 

On the contrary, in the p-Si(100)/TiO2-St/ITO cell, the electrostatic potential was in the opposite direction, so the SPS values should be decreased in a series of junction capacitors. If TiO, can absorb photons and cause photogenerated electron-hole pairs, these electrons can be confined in the lower potential well, and the response values of SPS can be further decreased. The photovoltage response is decreased by about 40 and 5 times due to the deposition of the TiO -St monolayer on the hydrophobic and hydrophilic p-Si(lOO) surfaces, respectively. 

Table 11.11. Calculated (without zero-point correction) at monolayer coverage and experimental adsorption energies (per one water molecule) for H2O/TiO2(110) (kcal/mol), [790].

Peteket al. [148, 149] provided some indirect evidence that part of CH3OH was adsorbed at Tisc sites dissociatively. Using two-photon photoemission spectroscopy (2PPE), an empty wet electron state at about 2.3 0.2 eV above Fermi level (Ep) was detected on both reduced and stoichiometric rutile TiO2(110). However, in the case of H2O, this excited state could only be observed on reduced rutile Ti02(l 10) surfaces with simultaneous presence of monolayer water and bridging hydroxyls... 

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