Titanium oxide xerogel films in porous aluminum oxide for photocatalytic application

Abstract

We have used the sol-gel method to synthesize titanium dioxide in the pores of an anodic aluminum oxide membrane. The samples were used for the test reaction of degradation of the organic dye rhodamine B. The concentration of the dye rhodamine B was monitored from the change in the absorption spectra in the 554 nm region, for an aqueous solution containing the dye and exposed to the emission from a mercury lamp. The synthesized samples of titanium oxide xerogel in the porous anodic aluminum oxide membrane are efficient photocatalysts for decomposition of organic dyes in an aqueous medium.Introduction. From the time photocatalytic decomposition of water on TiO 2 electrodes was discovered in 1972, photocatalytic oxidation of aqueous and gaseous contaminants has been studied intensively with the aim of solving the problem of environmental pollution [1][2][3][4]. Compared with other semiconductors, TiO 2 has found broad application due to its physical and chemical stability, corrosion resistance, low cost, and lack of toxicity. The TiO 2 bandgap width is 3.2 eV and 3.0 eV for anatase and rutile respectively [5]. Practically any organic compound can be oxidized on the surface of TiO 2 down to CO 2 and H 2 O, so design of photocatalysts based on TiO 2 to remove toxic organic substances from water and air is an important and quite realistic applied problem. Recently studies of catalytic processes using TiO 2 have been aimed at obtaining immobilized catalysts in the form of thin films with an extended surface and stable porous structure, making it possible to reduce energy costs associated with separation of reaction mixtures when using powdered catalysts [6].Accordingly, interest in photocatalysis has been focused on development of methods for synthesis of porous titanium oxide, such as anodizing titanium and obtaining semiconductor TiO 2 nanotubes for oxidative photoelectrochemistry [7], using pore-formers [8] and templates to form a regular mesoporous structure [9]. Films have been deposited both on the smooth surface of glass, metal, and silicon and also on the smooth surface obtained by etching borosilicate glass in hydrofluoric acid [8].Alternatively, to us it seems feasible to form a porous titanium oxide by the sol-gel method, using the tubular surface of porous anodic aluminum oxide as the base [10][11][12][13][14].Experimental Procedure. Samples of aluminum foil (99.99% pure) of thickness 0.2 mm were degreased in a solution based on potassium dichromate (3%) and sulfuric acid (80%) and, after washing and drying, were electrochemically polished in a mixture of ethanol and perchloric acid (5:1) at T ≤ 15

Recent Progress in the Fabrication and Optical Properties of Nanoporous Anodic Alumina

“…Due to all these properties, NAA has been used in various fields of research, including nanotechnology, material science, biotechnology, and biomedicine. The versatility of the NAA has been proven by applications such as photonic crystals [7], optical information encoding [8], high-density magnetic storage [9], solar cells [10,11], biosensing [12][13][14], nanopatterning masks [6,15], catalysis [16,17], gas sensing [18,19], drug delivery [20,21], filtration [22], photocatalysis [23], cancer therapy [24], fluorescence detection [25], boneimplant [26], and so on. The air-impregnated hydrophobic NAA has been found to be an efficient anticorrosive material [27], whereas the impregnation of the lubricant liquid such as oil into NAA resulted in omniphobicity [28] and improved corrosion resistance [29] and antibacterial resistance [30,31].…”

Current Trends in Nanoporous Anodized Alumina Platforms for Biosensing Applications

“…Keller et al have developed closely packed hexagonally arranged duplex structured NAA with pores and barrier type of oxide layer formation by anodic oxide coating through electrolytes [13]. The most popular fabrication method to synthesis NAA is electrochemical anodization, which has wide variety of applications in areas such as filtration process [14], biosensor [15,16], drug delivery [17], corrosion resistant [18], oxygen sensor [19], catalysis [20], photocatalytic [21], cancer therapy [22], refractometric [23], interferometric [24], DNA sensor [25], bone implant [26], separation [27], and fluorescence detection [28]. The growth of porous structure depends on the ionic transport in anodic oxides under the influence of electric field by anodic polarization in a suitable electrolyte.…”