08.09.2008

Synthesis and electronic behaviors of TiO₂/carbon clusters/Cr₂O₃ composite materials

^aDepartment of Applied Chemistry, Faculty of Science and Engineering, Kinki University, 3-4-1 Kowakae, Higashiosaka, Osaka 577-8502, Japan ^bMolecular Engineering Institute, Kinki University, 11-6 Kayanomori, Iizuka, Fukuoka 820-8555, Japan

Received 11 February 2008;

revised 22 May 2008;

accepted 27 May 2008.

Available online 31 May 2008.

Abstract

Nano-structured TiO₂/carbon clusters/Cr₂O₃ composite material has been successfully obtained by the microwave treatment of a TiO(acac)/Cr(acac)₃/epoxy resin complex. The compositions of the composite materials were determined using ICP, elemental analysis and surface characterization by SEM–EDX, TEM and XRD. ESR spectral examinations suggest the possibility of an electron transfer in the process of TiO₂ → carbon clusters → Cr₂O₃ with an oxidation site at TiO₂ particles and a reduction site at Cr₂O₃ particles. The preliminary experimental results show that the calcined materials could decompose methylene blue under visible-light irradiation.

Keywords: Nano-structures; Polymers; Carbon clusters; Titanium dioxide; Electron transfer

PACS classification codes: 71.20.Rv; 71.20.Nr; 72.80.Tm; 73.63.Bd; 74.25.Jb

Article Outline

1. Introduction
2. Experimental 2.1. Reagents 2.2. Synthesis of complexes 2.3. Microwave-treated calcinations of complexes 2.4. Characterization and property evaluation
3. Results and discussion 3.1. Characterization of the materials 3.2. Electronic nature of the calcined materials
4. Conclusions
References

Fig. 2. XRD patterns of calcined materials: (a) Ic's, (b) IIc's and (c) IIIc's.

Fig. 3. TEM images of calcined materials: (a) Ic's, (b) IIc's and (c) IIIc's.

Fig. 4. ESR spectra of calcined material Ic-4 in the presence of 1,4-benzoquinone and 1,4-hydroquinone.

Fig. 5. ESR spectra of calcined material IIc-4 in the presence of 1,4-benzoquinone and 1,4-hydroquinone.

Fig. 7. Relationship between the amounts of decomposed methylene blue and the reaction time in the presence of Ic-6, IIc-6 and IIIc-6 under the visible-light irradiation and/or in the dark.

Scheme 2. Schematic energy level diagram for TiO₂, carbon clusters and Cr₂O₃ and plausible electron transfer process in the composite materials (V.B. is valence band, C.B. is conduction band and E_g is band gap energy).