This work investigated the photoluminescence characteristics of TiO2 and discussed the relationship between the photoluminescence features of TiO2 and the photoassisted reaction of water/methanol mixture. It is found that anatase TiO2 displays a visible luminescence band centered at about 505 nm and rutile TiO2 mainly shows a near-infrared luminescence band centered at about 835 nm, which are respectively ascribed to the oxygen vacancies in anatase TiO2 and the intrinsic defects in rutile TiO2. The visible luminescence band is easily quenched by the Pt deposited on the surface of TiO2, while the near-infrared luminescence band is hardly influenced by the deposited Pt. It is suggested that the excited electrons trapped in the oxygen vacancies of anatase are facilely transferred to Pt to contribute to the photoassisted reaction, but the electrons trapped in the intrinsic defects of rutile are not.

Anatase and rutile TiO(2) were investigated with photoluminescence techniques under the weak excitation condition, where trap states play a vital role in carrier dynamics. The visible emission of anatase and near-infrared (NIR) emission of rutile both exhibit extremely long lifetimes up to milliseconds. The decay processes can be well described by the power-law decay which corresponds to the trapping-detrapping effect. These results indicate that the luminescence processes in both anatase and rutile TiO(2) have a close relationship with trap states. The visible emission band was assigned to the donor-acceptor recombination. Oxygen vacancies and hydroxyl groups mainly serve as the donor and acceptor sites, respectively. The NIR luminescence is originated from the recombination of trapped electrons with free holes, while the trapped electrons were formed through two paths, direct trapping or trap-to-trap hopping. The trap states in anatase and rutile TiO(2) may largely influence the photocatalysis process of TiO(2) and determine the photocatalytic activity under stationary illumination.

The anaerobic photocatalytic reaction of methanol on Pt/TiO 2 catalyst was studied by in situ Fourier transform IR and time-resolved IR spectroscopy. For the Pt/TiO 2 catalysts reduced at high temperature, the capacity of methanol adsorption decreases with the increase of the Pt loading, indicating that Pt particles or atoms occupy some of the active sites on TiO 2 for methanol adsorption. Surface species CH 2 O(a), CH 2 OO(a), and HCOO(a) are derived from the photocatalytic reaction of methanol on Pt/TiO 2 . The increase of gas-phase methanol or water accelerates the photoreaction and improves the activity of H 2 production. When the catalysts are exposed to methanol, the strong electronic absorption on nanosecond to second time scale is observed, indicating that a great amount of long-lived electrons are produced in TiO 2 -based photocatalysts after band gap excitation. The decay rate of the long-lived electrons correlates well with the activity of H 2 production. These results show that the long-lived electrons contribute to the H 2 generation and the decays of the long-lived electrons on millisecond to second time scale in Pt/TiO 2 are ascribed to the reaction for H 2 evolution: e tr -[Pt] + H + fH‚f1/2H 2 . The function of the molecularly adsorbed methanol or water is found to mediate the proton transfer on the TiO 2 surface. The activities of H 2 production under steady-state irradiation conditions were also measured, and it is deduced that the yield of the long-lived electrons could be responsible for the activity of H 2 production.

Ambipolar organic field‐effect transistors (OFETs) are produced, based on organic heterojunctions fabricated by a two‐step vacuum‐deposition process. Copper phthalocyanine (CuPc) deposited at a high temperature (250 °C) acts as the first (p‐type component) layer, and hexadecafluorophthalocyaninatocopper (F16CuPc) deposited at room temperature (25 °C) acts as the second (n‐type component) layer. A heterojunction with an interpenetrating network is obtained as the active layer for the OFETs. These heterojunction devices display significant ambipolar charge transport with symmetric electron and hole mobilities of the order of 10–4 cm2 V–1 s–1 in air. Conductive channels are at the interface between the F16CuPc and CuPc domains in the interpenetrating networks. Electrons are transported in the F16CuPc regions, and holes in the CuPc regions. The molecular arrangement in the heterojunction is well ordered, resulting in a balance of the two carrier densities responsible for the ambipolar electrical characteristics. The thin‐film morphology of the organic heterojunction with its interpenetrating network structure can be controlled well by the vacuum‐deposition process. The structure of interpenetrating networks is similar to that of the bulk heterojunction used in organic photovoltaic cells, therefore, it may be helpful in understanding the process of charge collection in organic photovoltaic cells.

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Various sized ZnS nanocrystals were prepared by treatment under H 2 S atmosphere. Resonance Raman spectra indicate that the electron-phonon coupling increases with increasing the size of ZnS. Surface and interfacial defects are formed during the treatment processes. Blue, green and orange emissions are observed for these ZnS. The blue emission (430 nm) from ZnS without treatment is attributed to surface states. ZnS sintered at 873 K displays orange luminescence (620 nm) while ZnS treated at 1173 K shows green emission (515 nm). The green luminescence is assigned to the electron transfer from sulfur vacancies to interstitial sulfur states, and the orange emission is caused by the recombination between interstitial zinc states and zinc vacancies. The lifetimes of the orange emission are much slower than that of the green luminescence and sensitively dependent on the treatment temperature. Controlling defect formation makes ZnS a potential material for photoelectrical applications.

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The relationship between the performance characteristics of organic field‐effect transistors (OFETs) with 2,5‐bis(4‐biphenylyl)bithiophene/copper hexadecafluorophthalocyanine (BP2T/F16CuPc) heterojunctions and the thickness of the BP2T bottom layer is investigated. Three operating modes (n‐channel, ambipolar, and p‐channel) are obtained by varying the thickness of the organic semiconductor layer. The changes in operating mode are attributable to the morphology of the film and the heterojunction effect, which also leads to an evolution of the field‐effect mobility with increasing film thickness. In BP2T/F16CuPc heterojunctions the mobile charge carriers accumulate at both sides of the heterojunction interface, with an accumulation layer thickness of ca. 10 nm. High field‐effect mobility values can be achieved in continuous and flat films that exhibit the heterojunction effect.