TiO2 nanoparticles were modified with a porphyrin derivative, 5-[4-benzoic acid]-10,15,20-tris[3,5-di-tert-butylphenyl]-21H,23H-porphyrin (H2P-COOH), and fluorescein derivatives, 9-[2-(3-carboxy-9,10- diphenyl)anthryl]-2,7-difluoro-6-hydroxy-3H-xanthen-3-one (DPAX-COOH) and 2′,7′-difluorofluorescein (FL-COOH). The dye-modified TiO 2 nanoparticles were deposited on nanostructured OTE/SnO2 (OTE: optically transparent electrodes) together with nanoclusters of fullerene (C60) from acetonitrile/toluene (3:1, v/v) using an electrophoretic deposition technique. The dye-modified TiO2 composite electrodes [OTE/SnO2/(dye + C60)n] have broad as well as high absorbance properties in the visible region, exhibiting the photo response under visible light excitation using I3-/I- redox couple. The incident photon to photocurrent efficiency (IPCE) for these electrodes increases in order: OTE/SnO2/(H2P)n < OTE/SnO 2/(H2P-COO-TiO2)n < OTE/SnO 2/(H2P-COO-TiO2 + C60). The IPCE value can be further improved by replacing H2P-COOH with a fluorescein derivative containing an electron donor moiety: DPAX-COOH (DPA: diphenylanthracene). The maximum IPCE value (42%) is obtained for OTE/SnO 2/(DPAX-COO-TiO2 + C60)n under the bias of 0.2 V vs. SCE.
Bibliographical noteFunding Information:
This work was partially supported by a Grant-in-Aid (No. 16205020) and by a COE program of Osaka University (Integrated Ecochemistry) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan. PVK acknowledges the support from the Office of Basic Energy Science of the US Department of the Energy. This is contribution No. NDRL 4608 from the Notre Dame Radiation Laboratory and from Osaka University. We are grateful to Dr. Yuji Wada, Osaka University, for helping preparation of TiO 2 nanoparticles modified with dyes.
- Light energy conversion
- TiO nanoparticles