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ABSTRACT: Transcutaneous implants that penetrate through the depth of the skin are used in numerous clinical applications, including prosthetics and dental implants. Favorable interactions between the implant surface and the respective skin layers are critical for the long-term success of transcutaneous implantable devices, hence, it is essential to understand the physiologic response elicited by skin-biomaterial interactions. Recent studies have shown that material surfaces that provide topographic cues at the nanoscale level may provide one possible solution to enhanced biomaterial integration, thus preventing biomaterial rejection. In this study titania nanotube arrays were fabricated using a simple anodization technique as potential interfaces for transcutaneous implantable devices. The in vitro functionality of human dermal fibroblasts and epidermal keratinocytes were evaluated on these nanotube arrays (diameter 70-90 nm, length 1-1.5 μm). Cellular functionality in terms of adhesion, proliferation, orientation, viability, cytoskeletal organization, differentiation and morphology were investigated for up to 4 days in culture using fluorescence microscope imaging, a cell viability assay, indirect immunofluorescence and scanning electron microscopy. The results reported in this study indicate increased dermal fibroblast and decreased epidermal keratinocyte adhesion, proliferation and differentiation on titania nanotube arrays.
Acta biomaterialia 03/2011; 7(6):2686-96. · 3.98 Impact Factor
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Journal of Biomedical Materials Research Part A 01/2011; · 2.63 Impact Factor
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ABSTRACT: Solid-state dye-sensitized solar cells (SS-DSCs) offer the potential to make low cost solar power a reality, however their photoconversion efficiency must first be increased. The dyes used are commonly narrow band with high absorption coefficients, while conventional photovoltaic operation requires proper band edge alignment significantly limiting the dyes and charge transporting materials that can be used in combination. We demonstrate a significant enhancement in the light harvesting and photocurrent generation of SS-DSCs due to Förster resonance energy transfer (FRET). TiO(2) nanotube array films are sensitized with red/near IR absorbing SQ-1 acceptor dye, subsequently intercalated with Spiro-OMeTAD blended with a visible light absorbing DCM-pyran donor dye. The calculated Förster radius is 6.1 nm. The donor molecules contribute a FRET-based maximum IPCE of 25% with a corresponding excitation transfer efficiency of approximately 67.5%.
Nano Letters 07/2010; 10(7):2387-94. · 13.20 Impact Factor
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ABSTRACT: Highly ordered vertically oriented TiO(2) nanotube arrays fabricated by electrochemical anodization offer a large surface area architecture with precisely controllable nanoscale features. These nanotubes have shown remarkable properties in a variety of applications including, for example, their use as hydrogen sensors, in the photoelectrochemical generation of hydrogen, dye-sensitized and solid-state heterojunction solar cells, photocatalytic reduction of carbon dioxide into hydrocarbons, and as a novel drug delivery platform. Herein we consider the development of the various nanotube array synthesis techniques, different applications of the TiO(2) nanotube arrays, unresolved issues, and possible future research directions.
Physical Chemistry Chemical Physics 03/2010; 12(12):2780-800. · 3.57 Impact Factor
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ABSTRACT: We report on the formation of titanium dioxide nanotube arrays having the largest known pore size, approximately 350 nm diameter. The nanotube arrays are synthesized by Ti foil anodization in a diethylene glycol electrolyte containing low (0.5-2%) concentrations of hydrofluoric acid. The large pore size nanotube arrays are achieved with extended anodization durations of approximately 120 h, with the anodization duration showing a more significant effect on pore diameter than the anodization voltage. It appears that the combined effects of hydrofluoric acid content and anodization duration determine the lateral etching rate of the nanotubes, leading to the larger pore size nanotubes.
Langmuir 01/2010; 26(1):417-20. · 4.19 Impact Factor
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ABSTRACT: BiVO4 thin films comprised of ordered arrays of pyramidal-shaped nanowires vertically oriented to a fluorine doped tin oxide coated glass substrate have been successfully fabricated by seed-mediated growth in an aqueous BiVO4 suspension. The effect of the growth temperature, 40 to 95 °C, pH, stirring and reaction time on the resulting BiVO4 film morphology was investigated using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy with a growth mechanism proposed. We consider the effects of film morphology in application to photoelectrochemical water splitting.
12/2009;
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ABSTRACT: In this study, TiO(2) nanotubes of various dimensions were used to elute albumin, a large protein molecule, as well as sirolimus and paclitaxel, common small molecule drugs. The nanotubes controlled small molecule diffusion for weeks and large molecule diffusion for a month. Drug eluted from the nanotubes was bioactive and decreased cell proliferation in vitro. Elution kinetics was most profoundly affected by tube height. This study demonstrates that TiO(2) nanotubes may be a promising candidate for a drug-eluting implant coating.
Nano Letters 04/2009; 9(5):1932-6. · 13.20 Impact Factor
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The Journal of Physical Chemistry B 11/2008; · 3.70 Impact Factor
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ABSTRACT: We detail anodic oxidation variables affecting the fabrication of vertically oriented TiO2 nanotube arrays using an electrolyte of dimethyl sulfoxide (DMSO) containing either hydrofluoric acid (HF), potassium fluoride (KF), or ammonium fluoride (NH4F). Various anodization variables including F- ion concentration, voltage, anodization time, water content, and previous use of the electrolyte can be combined to achieve nanotube arrays with length and morphology relevant to required applications. Using an anodization potential of 60 V with an electrolyte of 2% HF in DMSO, 70 h duration, nanotubes are achieved having a length of 101 μm, inner diameter 150 nm, and wall thickness 15 nm for a calculated geometric area of 3475. The weak adhesion of the DMSO fabricated nanotubes to the underlying oxide barrier layer and low tube-to-tube adhesion facilitates their separation for applications where dispersed nanotubes are desired. We examine the photoelectrochemical properties of 45 μm long nanotube arrays, crystallized by annealing at 580 °C for 6 h in oxygen gas, tested under UV (320−400 nm) and solar simulated light (AM 1.5) illumination.
08/2007;
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ABSTRACT: The fabrication of highly-ordered TiO2 nanotube arrays up to 134 µm in length by anodization of Ti foil has recently been reported (Paulose et al 2006 J. Phys. Chem. B 110 16179). This work reports an extension of the fabrication technique to achieve TiO2 nanotube arrays up to 220 µm in length, with a length-to-outer diameter aspect ratio of ≈1400, as well as their initial application in dye-sensitized solar cells and hydrogen production by water photoelectrolysis. The highly-ordered TiO2 nanotube arrays are fabricated by potentiostatic anodization of Ti foil in fluoride ion containing baths in combination with non-aqueous organic polar electrolytes including N-methylformamide, dimethyl sulfoxide, formamide, or ethylene glycol. Depending upon the anodization voltage, the inner pore diameters of the resulting nanotube arrays range from 20 to 150 nm. As confirmed by glancing angle x-ray diffraction and HRTEM studies, the as-prepared nanotubes are amorphous but crystallize with annealing at elevated temperatures.
Nanotechnology 01/2007; 18(6):065707. · 3.98 Impact Factor
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ABSTRACT: Described is the fabrication of self-aligned highly ordered TiO(2) nanotube arrays by potentiostatic anodization of Ti foil having lengths up to 134 mum, representing well over an order of magnitude increase in length thus far reported. We have achieved the very long nanotube arrays in fluoride ion containing baths in combination with a variety of nonaqueous organic polar electrolytes including dimethyl sulfoxide, formamide, ethylene glycol, and N-methylformamide. Depending on the anodization voltage, pore diameters of the resulting nanotube arrays range from 20 to 150 nm. Our longest nanotube arrays yield a roughness factor of 4750 and length-to-width (outer diameter) aspect ratio of approximately 835. The as-prepared nanotubes are amorphous but crystallize with annealing at elevated temperatures. In initial measurements, 45 mum long nanotube-array samples, 550 degrees C annealed, under UV illumination show a remarkable water photoelectrolysis photoconversion efficiency of 16.25%.
The Journal of Physical Chemistry B 09/2006; 110(33):16179-84. · 3.70 Impact Factor
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ABSTRACT: Described is the fabrication and hydrogen gas sensing properties of self-aligned highly-ordered TiO2 nanotube arrays having lengths up to 222 μm with a length-to-outer diameter aspect ratio of ∼1,500. The nanotube arrays are made by potentiostatic anodization of Ti foil in fluoride ion containing baths in combination with a variety of non-aqueous organic polar electrolytes including formamide, N-methylformamide, dimethyl sulfoxide, and ethylene glycol. The inner pore diameters of the resulting nanotube arrays range from 20 nm to 150 nm depending upon the anodization voltage. The as-prepared nanotubes are amorphous and show no gas-sensing capabilities. The nanotube arrays crystallize upon annealing at elevated temperatures, ∼550 °C, and subsequently demonstrate excellent hydrogen gas sensing capabilities but suffer from significant response and recovery times.
Sensor Letters 08/2006; 4(3):334-339. · 0.82 Impact Factor
