Dye-sensitized TiO2 Nanotube Research Articles

Evaluation of visible-light driven photocatalytic reaction by porphyrin coupled TiO2 nanotubes obtained via rapid breakdown anodization

The perceived attraction of nanotubular TiO2 in diverse applications has brought the researchers attention to focus on various aspects of nanotube synthesis and modification. In this work, the visible light activity of dye sensitized TiO2 nanotubes obtained in powder form via rapid breakdown anodization was investigated. Tetra (4-carboxy phenyl) porphyrin (TCPP) was used as a visible light sensitizing component on phase pure anatase TiO2 nanotubes (ATiNT). The effect of introducing two different anchoring groups between the dye and TiO2 nanotubes on photocatalytic activity was investigated. The visible light photocatalytic efficiency of the prepared ATiNT/TCPP composites was tested on a pharmaceutical compound, famotidine (FAM) in order to avoid degradation through photosensitization. For the given amount of TCPP load on ATiNT, the presence of a lengthy anchoring group between TCPP and ATiNT had a negative influence on the photocatalytic activity. Direct oxidation through visible-light-generated holes in the ATiNT/TCPP composite appeared to be the most significant pathway for FAM photocatalysis.

Dye-sensitized TiO2 nanotube membranes act as a visible-light switchable diffusion gate.

Here we report that both-end open anodic TiO2 nanotube membranes, after sensitization with a Ru(ii)-based dye, exhibit visible-light switching properties for flow-through the nanotube channels. Under illumination, the gate is in an open state providing ∼four-times faster permeation of small molecules through the membrane compared to a dark state. Switching is reversible with no apparent dye degradation being observed. Gating is possible not only of permeating dye molecules but also of nanoprobes such as polystyrene nanospheres. Supported by quantitative modelling, we attribute the switching mechanism to light-induced changes of the charge distribution at the dye/TiO2 interface which in turn alters the hydrodynamics within the anodic tube membranes. This demonstrates that these simple dye-sensitized nanotube membranes can be used as an optically addressable flow-through gate in nanofluidics.

Hole-induced polymerized interfacial film of polythiophene as co-sensitizer and back-electron injection barrier layer in dye-sensitized TiO2 nanotube array

In this work, we demonstrate that an ultra-thin film of polythiophene deposited interfacially via hole-induced polymerization on the surface of dye-sensitized TiO2 nanotube array acts as co-sensitizer, and hinders back-electron transfer in a DSSC. Consequently, the dark current, and the recombination reactions can be suppressed, leading to an improved number of electron density at the TiO2 array electrode. Thus, an enhanced photocurrent, and power conversion efficiency of the device is achieved. This logical concept is experimentally justified, and the device, after polythiophene interfacial treatment, demonstrates an enhanced power conversion efficiency by the factor of 39.19%.

BIAN-Fluorene Copolymer Bearing Ruthenium Pendant as Sensitizer of Titanium Nanotubes for Photocatalytic Hydrogen Evolution

We describe ruthenium coordinated n-type polymer material as a sensitizer for TiO2 nanotubes for visible light driven photocatalytic production of hydrogen. The dye is a novel ruthenium coordinated BIAN (bisiminoacenaphthene)-Fluorene (2,7-Diethynyl-9,9-dioctyl-9H-fluorene) polymer. Photoresponse of the material was observed by measuring the changes in the open circuit potential voltage which showed a vertical drop of 0.57 V in the potential. From the I-V characteristics, the maximum value of photocurrent observed in the presence of visible light was 245 μA. The monitoring of rate of H2 evolution exhibited as high as 3.75 μmol/hour of H2 with the dye sensitized TiO2 nanotubes at a low bias potential of 0.15V (vs Ag/AgCl), compared to only 2.1 μmol/hour in case of bare TiO2 nanotubes even at higher bias potential of 0.5V. This shows the material has got the potential as a photocatalyst in the photoelectrochemical splitting of water.

Characterization of N719 Dye Desorption on TiO<sub>2</sub> Nanotube Arrays Used for Dye-Sensitized Solar Cells

In this work, we developed a method to quantitative analyze the absorption and desorption of N719 dye on TiO2 nanotube arrays. TiO2 nanotube arrays were fabricated by anodizing titanium foils in an organic electrolyte using a two-electrode configuration with a platinum mesh as the counter electrode. TiO2 nanotube arrays were then annealed under 450 °Cfor 3 hours and immersed in N719 dye solution for 24 hours. The dye-sensitized TiO2 nanotube arrays were soaked in an electrolyte solution and stored in a dark closed vessel for 76 days. Then they were desorbed by KOH solution (pH=10). According to UV-visible absorption spectra and Lambert-Beer's law, the desorption rate of N719 dye on 9 µm thick TiO2 nanotube arrays was calculated to be 36%. The results provide a valuable reference to study the dye desorption and stability of the dye-sensitized solar cells.

Highly-ordered dye-sensitized TiO2 nanotube arrays film used for improving photoelectrochemical electrodes

Thin titanium oxide nanotube arrays (TNAs) films were synthesized by anodization of titanium foil in an aqueous dimethyl sulfoxide solution using a platinum foil counter electrode. TNAs up to 6.8 μm in length, 120 nm in inner pore diameter, and 20 nm in wall thickness were obtained by 40 V potentials anodization for 24 h. Their microstructures and surface morphologies were characterized by XRD, TEM, SAED and UV-vis spectroscopy. The photoelectrochemical properties of as-prepared unsensitized and dye-sensitized TNAs electrodes were examined under simulated solar light (AM 1.5, 100 mW/cm2) illumination. The results showed that the photocurrent of the dye-sensitized TNAs electrodes reached 6.9 mA/cm2, which was 6 times more than that of the dye-sensitized TiO2 nanoparticles (TNPs) electrodes. It implied that the electron transport process and the charge recombination suppression within TNAs electrodes were much more favorable in comparison with that in the TNPs electrodes. Electrodes applying such kind of titania nanotubes will have a potential to further enhance the efficiencies of TNAs-based dye-sensitized solar cells.

Hydrogen Sensing Properties of Dye-Sensitized TiO<sub>2</sub> Nanotube Array

A dye-sensitized TiO2 nanotube array (DST) was fabricated by electrochemical anodization in an aqueous organic electrolyte and immersed into ethanol containing N719 dye. The crystal phase and microstructure of the TiO2 nanotube array (TNTA) were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The UV-Vis spectra of the DST were characterized by diffuse reflectance spectra (DRS). The hydrogen sensitivity of the as-prepared sample was tested at room temperature under Xe-lamp (simulated solar light) irradiation. It was found that the sensor was highly sensitive to low concentrations of hydrogen as an application in air quality control.

Visible-Light Photocatalyst of Tetramethoxyphenylporphyrin Sensitized TiO<sub>2</sub> Nanotube

This paper investigated the performance of photocatalysts of TiO2 nanotubes sensitized by photosensitizers of tetramethoxyphenylporphyrin(TMPP) for producing H2 from water under visible light. This photocatalyst might have a smaller band gap (2.6 eV). The investigation shows that a photosensitized catalyst combined TiO2 nanotube with TMPP can be used to extend the absorption of solar light region and enhance the efficiency of energy conversion, and the quantity of H2 evolution is 1.427 L m-2h-1g-1. It was a way to apply the dye sensitized TiO2 nanotubes photocatalyst in the visible light for clean energy.

Dye-Sensitized TiO2 Nanotube Solar Cells with Markedly Enhanced Performance via Rational Surface Engineering

Highly ordered anodic TiO2 nanotube arrays fabricated by electrochemical anodization were sensitized with ruthenium dye N-719 to yield dye-sensitized TiO2 nanotube solar cells. Rational surface tre...

Dye-Sensitized TiO2 Nanotubes with Ag Nanoparticles

The present work examines the deposition of Ag nanoparticles on anodic TiO2 nanotubes in order to improve solar energy conversion by increasing the optical absorption of dye. Ag nanoparticles are successfully deposited on TiO2 nanotube layers. The size of nanoparticles is increased when amorphous TiO2 nanotubes are crystallized and the tube diameter is increased. Photocurrent for dye-sensitized TiO2 nanotubes is increased by the deposition of Ag nanoparticles, but the increment is decreased during dye-sensitization. This may be ascribed to the dissolution of Ag nanoparticles during the sensitization and the decreased plasmon resonance effect by thickening the dye layer on Ag nanoparticles.

Dye-Sensitized TiO2 Nanotubes with Ag Nanoparticles

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Dye-sensitized TiO2 nanotube solar cells: fabrication and electronic characterization

TiO2 nanotubes (TNTs) with large aspect ratio and large specific surface area were prepared from P25 (Nippon Aerosil) and applied to dye-sensitized titanium dioxide solar cells (DSSCs). Optimization of fabrication conditions, i.e., pH of the starting paste, sintering temperature for the TiO2 electrodes, electrolyte compositions of DSSCs gave the high conversion efficiency with improved open circuit voltage (V(oc)) and fill factor (FF) when compared to DSSCs made of P25. The evaluation of dye adsorption and the photo-injected electron transport such as electron diffusion coefficient (D) and electron lifetime (tau) in TNTs electrodes revealed that the higher efficiency resulted from increase of electron density with keeping much longer tau in TNTs electrodes than in P25 electrodes.