Charge Separation Behavior Research Articles

Electrochemically Assisted Photocatalysis of Hybrid WO3/TiO2 Films: Effect of the WO3 Structures on Charge Separation Behavior

In this study, the photocatalysis of hybrid WO3/TiO2 films with different loadings of WO3 were investigated with and without potential bias. It was clearly indicated that hybrid WO3/TiO2 films show less photo-reactivity under only UV-irradiation, while more effective photocatalysis under potential bias than either TiO2 or WO3 by themselves, their photocatalytic performance depending on the loadings of WO3. In particular, a hybrid WO3/TiO2 film involving an amorphous-like WO3 phase plays a significant role in an enhancement of the electrochemically assisted photocatalysis.

Photoelectrochemical properties of hybrid WO3/TiO2 electrode. Effect of structures of WO3 on charge separation behavior

In this study, morphology, structure, fundamental absorption edge and photocurrent response of hybrid WO3/TiO2 films were investigated. It was found that the band gap excitation of WO3/TiO2 caused effective charge separation to generate high anodic photocurrent by the oxidation of oxalic acid, and, in particular, a WO3/TiO2 electrode having an amorphous-like WO3 phase exhibited higher photocurrent than either WO3 or TiO2 itself. We demonstrated differences of two types of composite films between amorphous-like WO3 and polycrystalline WO3 supported on TiO2 using energy band structures.

Photo-induced surface charge separation of highly oriented TiO 2 anatase and rutile thin films

Surface charge separation behavior of photo-generated carriers in highly oriented TiO 2 anatase and rutile films was investigated using a technique in which the transient surface charge is observed by laser pulse irradiation without metal contacts and an externally applied field. According to the measurements, the quantum efficiency of photo-generated holes transported toward the surface was determined as a function of incident laser energy. The photo-generated holes in anatase can be transported toward the surface for irradiation at the photon energy of its bandgap. The holes transported toward the rutile surface, however, were generated close to the surface for irradiation at the photon energy much higher than its bandgap.

Photoinduced electron transfer in GFP/viologen/TCNQ structured hetero-LB film

The photoinduced electron transfer rate in hetero-Langmuir–Blodgett (LB) films, composed of electron sensitizing protein and electron accepting organics, was investigated. The hetero-LB film was fabricated by sequentially depositing green fluorescence protein (GFP), viologen, and TCNQ, which functioned as an electron sensitizer, a relay, and an acceptor, respectively. To verify the hetero-LB film formation, surface morphologies of the GFP film and viologen/TCNQ LB film were observed by atomic force microscopy (AFM). The fast charge separation of the molecular interface was investigated by analyzing the time-resolved fluorescence decays of GFP homo-, GFP/viologen hetero- and GFP/viologen/TCNQ hetero-LB film using a time-correlated single photon counting (TCSPC) method. In GFP/viologen hetero-films, the fluorescence decay of excited GFP was faster than that in the GFP homo-film. Based on the decay of fluorescence the charge separation rates of excited GFP were calculated. The fluorescence lifetime and charge separation rate of the GFP/viologen/TCNQ hetero-LB film increased slightly compared to that of the GFP/viologen hetero-LB film as a result of the addition of the TCNQ layer, electron acceptor. On the basis of its molecular interface charge separation behavior, the proposed molecular array can be used as a component of the molecular photodiode.