Ti-containing Mesoporous Silica Thin Films Research Articles

Controlled Synthesis and Surface Hydrophilic Properties of Ti-Containing Mesoporous Silica Thin Films Using Various Structure-Directing Agents

Transparent Ti-containing mesoporous silica thin films (Ti-MSTFs) have been successfully prepared on quartz substrates by a sol–gel/spin-coating method using various structure-directing agents (SDAs) with different chain lengths. Characterizations of their porous structures and local environments of Ti-oxide moieties in the silica framework were performed by XRD, XAFS, and FT-IR measurements, which revealed that all Ti-MSTFs had mesoporous structures and tetrahedrally coordinated Ti-oxide moieties. Their surface wetting properties were investigated by water contact angle measurements. Interestingly, water contact angles of Ti-MSTFs change depending on the length of the hydrophilic domains of the employed SDA, indicating that the surface wettability can be precisely controlled by varying the types of the SDA. Moreover, Ti-MSTFs act as a photocatalyst for the degradation of organics, such as methylene blue dyes and oleic acid, in which photocatalytic activities were influenced by the porous structure and su...

Design of superhydrophobic surfaces by synthesis of carbon nanotubes over Co–Mo nanocatalysts deposited under microwave irradiation on Ti-containing mesoporous silica thin films

The superhydrophobic surface has been designed by the synthesis of carbon nanotubes (CNTs) on Ti-containing mesoporous silica thin films (Ti-MSTFs) with Co-Mo binary nanocatalysts. The active Co-Mo catalysts have been successfully deposited on Ti-MSTFs under microwave irradiation. SEM and TEM observations after CNT synthesis revealed that surfaces of Ti-MSTFs were densely covered with CNTs having a diameter of 15 nm. Raman spectra indicated that the undesired structural defects in the carbon network of the synthesized CNTs, which would lead to the formation of hydroxyl groups, were scarce. Interestingly, hydrophobic properties of samples after CNT synthesis were enhanced with increasing titanium concentration of Ti-MSTF, and the water contact angle reached up to 165° on Ti-MSTF with a titanium concentration of 10 at%. The combination of dispersed titanium oxide moieties within the silica frameworks and the microwave irradiation made a great contribution to deposit active Co-Mo catalysts responsible for the formation of well-dense CNTs.

Low-temperature synthesis of highly hydrophilic Ti-containing mesoporous silica thin films on polymer substrates by photocatalytic removal of structure-directing agents

Download options Please wait... Article information DOI https://doi.org/10.1039/C0JM01404D Article type Paper Submitted 11 May 2010 Accepted 29 Sep 2010 First published 20 Oct 2010 Download Citation J. Mater. Chem., 2011,21, 236-241 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Low-temperature synthesis of highly hydrophilic Ti-containing mesoporous silica thin films on polymer substrates by photocatalytic removal of structure-directing agents Y. Horiuchi, H. Ura, T. Kamegawa, K. Mori and H. Yamashita, J. Mater. Chem., 2011, 21, 236 DOI: 10.1039/C0JM01404D To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Yu Horiuchi Haruhisa Ura Takashi Kamegawa Kohsuke Mori Hiromi Yamashita

Design of superhydrophilic surfaces on metallic substrates by the fabrication of Ti-containing mesoporous silica thin film

Ti-containing mesoporous silica thin films (Ti-MSTFs) have been prepared on Al and Al–Mg alloy substrates via a sol–gel/spin-coating method including two different processes for removal of a structure directing agent (SDA). One is calcination and the other is photocatalytic removal under UV-light irradiation utilizing photocatalysis of tetrahedrally coordinated titanium oxide moieties within the silica framework. Characterizations of mesoporous structures and local structures of titanium oxide moieties were performed by FT-IR, XRD, and UV–vis measurements. Water contact angle measurements revealed that highly hydrophilic surfaces were successfully formed on both metallic substrates by coating with Ti-MSTFs. These surfaces also exhibited photoinduced superhydrophilic properties under UV-light irradiation.

Coating of Transparent Ti-containing Mesoporous Silica Thin Films on Quartz and Aluminum Alloy Substrates for Fabrication of Highly Hydrophilic Surfaces

The fabrication of transparent Ti-containing mesoporous silica thin films (Ti-MSTFs) showing highly hydrophilic properties was achieved on quartz and Al alloy substrates by using a sol–gel/spin-coating technique. The presence of the mesoporous structure and titanium oxide species which exist in an isolated and tetrahedrally-coordinated state within the silica framework was observed by XRD and DRUV–vis measurements. The surface wettability on the Ti-MSTFs was also investigated based on the water contact angle measurement. Water contact angles on Ti-MSTFs on quartz and Al alloy substrates were extremely low values of 5° and 8° even under dark conditions, respectively, which were much smaller than those on original substrates. These observations indicate that highly hydrophilic surfaces were formed both on quartz and Al alloy substrates by coating with Ti-MSTFs. It can be interpreted that the capillary condensation due to the mesoporous structure and the presence of isolated titanium oxide species as adsorption sites of water contributed to the appearance of the high hydrophilicity. Furthermore, the irradiation of UV-light led to the decrease in water contact angles on Ti-MSTFs and it was found that Ti-MSTFs exhibited the photoinduced superhydrophilic properties.

Size-controlled synthesis of silver nanoparticles on Ti-containing mesoporous silica thin film and photoluminescence enhancement of rhodamine 6G dyes by surface plasmon resonance

Silver nanoparticles having a narrow size distribution were synthesized on Ti-containing mesoporous silica thin film (Ti-MSTF) using a simple photo-assisted deposition (PAD) method. Their particle sizes were successfully controlled by changing the photo-irradiation time during the deposition and average particle sizes at irradiation times of 1, 5 and 24 h were determined to be 2.7, 4.7 and 7.6 nm, respectively. The XPS depth profile analysis indicated that silver nanoparticles mainly exist not on the surface but in the thin film. UV–vis absorption spectra of these films showed an absorption band in the visible-wavelength region attributed to the surface plasmon resonance of silver nanoparticles. Rhodamine 6G (R6G) dye molecules were further embedded on Ti-MSTF after silver nanoparticle deposition. Photoluminescence properties of R6G dyes on these thin films were enhanced due to surface plasmon excitation from silver nanoparticles and the photoluminescence intensity reached up to 3 times as high as that achieved without silver nanoparticles. It was proven that the silver nanoparticle size had a strong influence on these enhancement effects.

Preparation of nano-sized Pt metal particles by photo-assisted deposition (PAD) on transparent Ti-containing mesoporous silica thin film

We have investigated a novel technique for the preparation of nano-sized Pt metals on Ti-containing mesoporous silica (TMS) thin film by photo-assisted deposition (PAD). The transparent TMS thin film was prepared on a quartz plate through sol—gel/spin coating. XRD, UV-Vis and Ti K-edge XAFS measurements revealed the formation of isolated Ti oxide species with a tetrahedral-coordination geometry in the silica framework. Deposition of Pt metal precursor on TMS thin film under UV-light irradiation, followed by reduction with molecular hydrogen, afforded a transparent thin film (Pt/TMS). The formation of highly dispersed nano-sized Pt metals having narrow size distributions was determined by Pd LIII-edge XANES and TEM analysis. The TMS and Pt/TMS thin films have been demonstrated to exhibit a strong hydrophilic property, even before UV irradiation, compared to the common mesoporous silica and TiO2 thin films. After UV-light irradiation, the contact angle of water droplet on the TMS and Pt/TMS thin films became extremely lower, indicating the appearance of the photo-induced super-hydrophilic property.

Investigation of local structures and photo-induced surface properties on transparent Me(Ti, Cr)-containing mesoporous silica thin films

Using a sol–gel/spin coating method, the transparent metal(Ti, Cr)-containing mesoporous silica thin films could be prepared on quarts plates. In the case of the Ti-containing mesoporous silica (TMS) thin film, the formation of isolated and tetrahedrally-coordinated Ti oxide species in the frameworks was confirmed by XRD, UV–vis, and Ti K-edge XAFS measurements. The TMS thin film has been proved to exhibit a strong hydrophilic property even before UV irradiation compared to the common mesoporous silica and TiO 2 thin films. After UV-light irradiation, the contact angle of water droplet on the TMS thin film become extremely lower, indicating the appearance of the photo-induced super-hydrophilic property. We have also synthesized the transparent Cr-containing mesoporous silica (CMS) thin film containing tetrahedrally-coordinated Cr oxide species, which showed the super-hydrophilic property even under visible light irradiation. By using the polymerization ability of the isolated Cr oxide species under UV light irradiation, the polyethylene phase was successfully formed on the surface of the CMS thin film. It was demonstrated that the surface property of the CMS was converted into hydrophobic while keeping its transparency. The single-site Cr oxide moieties are responsible for the photo-induced surface reaction as well as controlling the surface hydrophilic–hydrophobic properties.

Photo-induced super-hydrophilic property and photocatalysis on transparent Ti-containing mesoporous silica thin films

The transparent Ti-containing mesoporous silica thin films can be prepared on quartz plate using a spin-coating sol–gel method. The spectroscopic characterization has revealed that the Ti-containing mesoporous silica thin films contain isolated and tetrahedrally-coordinated titanium oxide moieties in the frameworks. Compared with the common mesoporous silica thin films, these Ti-containing mesoporous silica thin films have demonstrated a strong hydrophilic surface property even before UV-irradiation. After UV-light irradiation, the contact angle of water droplet on the Ti-containing mesoporous silica thin films became lower, indicating the appearance of the super-hydrophilic property. Under UV-light irradiation Ti-containing mesoporous silica thin films also exhibited highly selective activity for the photocatalytic oxidation of propylene. The isolated and tetrahedrally-coordinated titanium oxide moieties are responsible for these photo-induced surface reactions.

Synthesis of transparent Ti-containing mesoporous silica thin film materials and their unique photocatalytic activity for the reduction of CO 2 with H 2O

The transparent Ti-containing mesoporous silica thin film materials having two different types of hexagonal and cubic pore structures with a thickness of about 50 μm and a lateral size of a few centimeters were successfully synthesized by the solvent evaporation method from tetramethoxysilane (TMOS), vinyltrimethoxysilane (VTMOS), titanium tetra( iso-propoxide) (TIP), and octadecyltrimethylammonium chloride (C 18TAC). The films were converted to Ti-containing nanoporous silica thin films by subsequent calcinations in air at 823 K, while the highly ordered mesostructures and macroscopic morphology were retained after the surfactant removal by calcination. The films with hexagonal and cubic symmetry were obtained by changing the composition of the starting mixtures. Various spectroscopic measurements of these films clearly showed that Ti ions are present in the silica networks as a tetrahedrally coordinated Ti-oxide species with a high dispersion state. Thus, developed transparent Ti-containing thin films were used as photocatalysts for the reduction of CO 2 with H 2O to evaluate their unique and high photocatalytic activity. UV irradiation of these films in the presence of CO 2 and H 2O led to the formation of CH 4 and CH 3OH as well as CO and O 2 as minor products, their yields increasing linearly against irradiation time, indicating that these films operate as efficient photocatalysts to proceed such a difficult reaction catalytically at 323 K. Furthermore, the films having hexagonal pore structure exhibited higher photocatalytic activity than the Ti-MCM-41 powdered catalyst even with the same pore structure.

Direct synthesis and characterization of Ti-containing mesoporous silica thin films

Using acetylacetone as the hydrolysis-retarding agent, titanium has been directly incorporated into mesoporous silica thin films by a dip-coating method for the first time. Evidence from the ultraviolet–visible (UV–Vis) absorbance spectra, high-resolution electron microscopy (HREM), energy dispersion spectrum (EDS) and electron probe X-ray microanalysis (EPMA) indicated that Ti atoms were homogeneously dispersed in the siliceous framework and existed in the form of a Ti–O–Si bond. The increase of the film's basal spacing accompanied with an increase of Ti content was also observed.