Evolution of Nanocrystallinity in Periodic Mesoporous Anatase Thin Films

Choi, Sung Yeun; Mamak, Marc; Speakman, Scott A.; Chopra, Naveen; Ozin, Geoffrey A.

doi:10.1002/smll.200400038

Cited by 92 publications

(100 citation statements)

References 22 publications

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“…to obtain titania films with high surface area, uniform pore size, and a glassy or nanocrystalline framework, which could strongly influence the intrinsic properties of titania films. 31 Lamellar, cubic, and hexagonal structures of titania films have been studied previously. 32,33 Importantly, if the mesoporous coatings are to be used as surface drug delivery systems, the pores should be interconnected through the thickness of the coating.…”

Section: Discussionmentioning

confidence: 99%

Mesoporous titanium dioxide coating for metallic implants

et al. 2011

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A bioactive mesoporous titanium dioxide (MT) coating for surface drug delivery has been investigated to develop a multifunctional implant coating, offering quick bone bonding and biological stability. An evaporation induced self-assembly (EISA) method was used to prepare a mesoporous titanium dioxide coating of the anatase phase with BET surface area of 172 m(2)/g and average pore diameter of 4.3 nm. Adhesion tests using the scratch method and an in situ screw-in/screw-out technique confirm that the MT coating bonds tightly with the metallic substrate, even after removal from bone. Because of its high surface area, the bioactivity of the MT coating is much better than that of a dense TiO(2) coating of the same composition. Quick formation of hydroxyapatite (HA) in vitro can be related to enhance bonding with bone. The uptake of antibiotics by the MT coating reached 13.4 mg/cm(3) within a 24 h loading process. A sustained release behavior has been obtained with a weak initial burst. By using Cephalothin as a model drug, drug loaded MT coating exhibits a sufficient antibacterial effect on the material surface, and within millimeters from material surface, against E.coli. Additionally, the coated and drug loaded surfaces showed no cytotoxic effect on cell cultures of the osteoblastic cell line MG-63. In conclusion, this study describes a novel, biocompatiblemesoporous implant coating, which has the ability to induce HA formation and could be used as a surface drug-delivery system.

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Section: Discussionmentioning

confidence: 99%

Mesoporous titanium dioxide coating for metallic implants

et al. 2011

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“…19,42 X-ray diffraction of separately annealed samples was carried out with a Philips PW1830 Generator 3a.…”

Section: Wide-angle X-ray Scatteringmentioning

confidence: 99%

Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO₂crystallisation

Guldin

Hüttner

Tiwana

et al. 2011

Energy Environ. Sci.

118

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Anatase TiO 2 is typically a central component in high performance dye-sensitised solar cells (DSCs). This study demonstrates the benefits of high temperature synthesised mesoporous titania for the performance of solid-state DSCs. In contrast to earlier methods, the high temperature stability of mesoporous titania is enabled by the self-assembly of the amphiphilic block copolymer polyisoprene-block-polyethylene oxide (PI-b-PEO) which compartmentalises TiO 2 crystallisation, preventing the collapse of porosity at temperatures up to 700 • C. The systematic study of the temperature dependence on DSC performance reveals a parameter trade-off: while high temperature annealed anatase consisted of larger crystallites and had a higher conductivity, this came at the expense of a reduced specific surface area.While the reduction in specific surface areas was found to be detrimental for liquid-electrolyte DSC performance, solid-state DSCs benefitted from the increased anatase conductivity and exhibited a performance increase by a factor of three.

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“…Also, it would be desirable to crystallographically align the nanocrystals around the mesopores to optimize certain physical properties. [16] Both requirements were achieved through our soft-epitaxy methodology. Using higher, appropriate concentrations of the KLE block copolymer, the surfactant acted as porogen in the EISA procedure.…”

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confidence: 99%

Surfactant‐Mediated Generation of Iso‐Oriented Dense and Mesoporous Crystalline Metal‐Oxide Layers

et al. 2006

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The fabrication of thin layers of a transition-metal oxide with 3D oriented crystallites has substantial importance for industrial applications, for example, semiconductor technology. [1,2] Chemical vapor deposition [3] and molecular beam epitaxy [4] onto single-crystalline substrates are widely used fabrication techniques but they suffer from elaborate preparation setups. Most of the currently applied concepts to generate layers of oriented crystals involve the deposition of molecular species from the gas phase [5] (pulsed laser deposition, molecular beam epitaxy) or the liquid phase [6] (liquid phase epitaxy)on suitable single-crystalline surfaces. In these processes the crystals grow in a direction that is dictated by the lattice planes of the substrate exposed to the surface, and the substrate has to match the lattice parameter of the oxide (epitaxy). Solution-processing (SP) routes have been proposed as a versatile and facile alternative, especially for transition-metal oxides applying sol-gel reactions, because of the evident advantages of "beaker" chemistry and liquid-coating processing. [7][8][9] However, up until now SP has required single-crystalline substrates to achieve oriented crystallization, which represents a substantial limitation and complication. Therefore, it is not commonly expected and it has not been reported yet that crack-free layers of transition-metal oxides with a high degree of crystallographic orientation can be formed from aqueous solutions on arbitrary substrates.[10] Furthermore, the recently introduced class of mesoporous metal oxides could solely be prepared with a random distribution of nanocrystals within the pore walls. Here, we report a general, straightforward surfactant-mediated methodology for the preparation of dense and even well-ordered mesoporous films of transition-metal oxides with crystallographically oriented crystals (MoO 3 , Nb 2 O 5 , Ta 2 O 5 , V 2 O 5 , perovskites etc.) on noncrystalline substrates such as glass. In order to understand the underlying principles for this surprising finding, we performed a systematic study on a broad series of metal oxides (TiO 2 , CeO 2 , SnO 2 , etc.) to understand the relationship between the crystallographic orientation and the unit-cell characteristics of the different oxides. Interestingly, our studies revealed that this effect generally occurs for metal oxides with certain anisotropic unit-cell features, which is exemplified here in detail for MoO 3 and Nb 2 O 5 . It is justified to term this new surfactantmediated crystallization phenomenon "soft epitaxy", following the previously introduced polymer-controlled nucleation and crystallization of different inorganic salts as powders with various macroscopic 3D crystal structures. [11] As key element, our straightforward soft-epitactic process uses a surfactantmediated oriented nucleation from surfaces, starting from aqueous-ethanolic or water-free solutions, depending on the respective oxide. In essence, the approach involves dip-coating polar, wettable substrates (e.g.,...

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Evolution of Nanocrystallinity in Periodic Mesoporous Anatase Thin Films

Cited by 92 publications

References 22 publications

Mesoporous titanium dioxide coating for metallic implants

Mesoporous titanium dioxide coating for metallic implants

Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO₂crystallisation

Surfactant‐Mediated Generation of Iso‐Oriented Dense and Mesoporous Crystalline Metal‐Oxide Layers

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Evolution of Nanocrystallinity in Periodic Mesoporous Anatase Thin Films

Cited by 92 publications

References 22 publications

Mesoporous titanium dioxide coating for metallic implants

Mesoporous titanium dioxide coating for metallic implants

Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO2crystallisation

Surfactant‐Mediated Generation of Iso‐Oriented Dense and Mesoporous Crystalline Metal‐Oxide Layers

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Improved conductivity in dye-sensitised solar cells through block-copolymer confined TiO₂crystallisation