Adjusting the Electronic and Optical Properties of Mesoporous MCM-41 Materials by Ti Doping

• Solid mesoporous materials with ordered pore structures can be used for catalysis, genome sequencing, and drug delivering etc. The common method of synthesizing Ti doped mesoporous silica is to use costly ethyl silicate and tetrabutyl titanate as inorganic sources. In this work, however, low cost water glass and TiCl4 were used as the inorganic sources. Pore structures were studied by small angle X-ray diffraction, transmission electron microscopy, and N-2 adsorption-desorption. This Ti doped mesoporous material has binary mesopore structures with preferable pore sizes of 2.60 and 3.85 nm, respectively. Results from the ultraviolet-visible spectroscopy as well as density functional calculation employing a screened hybrid functional indicate that the mespore matrix contains tetrahedral coordinated Ti dopants (Ti-Si) and oxygen vacancies (V-O). The electron transitions from occupied V-O to the unoccupied Ti-Si contribute to the red-shift of the optical absorption edge. The hybrid potential describes fairly accurately the electronic structure and optical absorption, and we find an overall good qualitative agreement with the experimental characterization.

Nyckelord

Mesoporous Materials

Chemical Synthesis

First-Principles Calculation

Hybrid Functional

Density Functional

Optical Absorption

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