Physicochemical Properties Of TiO2 Research Articles

An updated review of industrially relevant titanium dioxide and its environmental health effects

Titanium dioxide (TiO2) is a metal oxide that occurs naturally when titanium reacts with airborne oxygen. It has various attractive and beneficial properties, such as thermal stability, photocatalysis potential, and resistance to ultraviolet radiation. As a result, it is widely used in industrial processes and commercial products. The physicochemical properties of TiO2 can vary depending on the material's primary particle size, crystallinity, and formulation. Different properties have been found to cause different toxicological responses. While most studies have focused on the effects of exposure to nano-TiO2, little attention has been given to other relevant TiO2 materials. In this review, we examine the toxicological profile of both titanium dioxide nanoparticles and pigmentary TiO2. This review aims to provide reliable information on titanium dioxide toxicity for public and private stakeholders to use in risk assessments.

The Effect of Titanium Oxyfluoride Morphology on Photocatalytic Activity of Fluorine-Doped Titanium(IV) Oxide

Titanium oxyfluoride (TiOF2) is a metastable product that can be obtained in a fluorine-rich environment. This material can also be a valuable precursor in the synthesis of titanium(IV) oxide (TiO2). However, the effect of TiOF2 morphology on the physicochemical properties of TiO2 has not been studied so far. In this work, single-phase TiOF2 was prepared by a solvothermal method. The as-synthesized samples exhibited a variety of morphologies, including different shapes and crystallite sizes. These materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS), surface area measurements, thermal gravimetric analysis (TGA) and UV–vis diffuse reflectance spectroscopy (DR/UV–vis). Furthermore, TiOF2 samples were used as precursors in the synthesis of fluorine-doped titanium(IV) oxide and applied in photocatalytic phenol degradation under UV-vis light. The experiments showed that the crystallite size of the precursor, as well as the number of fluoride ions used in the synthesis, were the predominant factors that affected the photocatalytic activity of the final photocatalyst.

Physicochemical properties of TIO2, ZrO2, Fe3O4 nanocrystalline adsorbents and photocatalysts

Physicochemical properties of TIO2, ZrO2, Fe3O4 nanocrystalline adsorbents and photocatalysts

Antibacterial and Biological Behavior of TiO2 Nanotubes Produced by Anodizing Technique.

Titanium dioxide nanotubes combine the geometrical properties of a tubular structure with the physico-chemical properties of TiO2. The nanotubes improve the surface characteristics of a material such as titanium, which possesses high mechanical resistance, and low density, enhancing its use for biomedical devices. The nanotubular layer increases the device's interaction with cells. In this paper, we discuss various aspects of the anodizing technique to obtain ordered nanotubes and careful control of the process parameters to obtain highly ordered TiO2 nanotubes. Also, we review the biological activity of TiO2 nanotubes, the effect of nanotube size on bioactivity, and the antibacterial effect of TiO2 nanotubes without doping. Finally, novel applications of TiO2 nanotubes employed as a biomaterial are discussed.

Morphology-dependent titanium dioxide nanoparticle-induced keratinocyte toxicity and exacerbation of allergic contact dermatitis.

Titanium dioxide (TiO2) nanoparticles are commonly found in consumer products, such as sunscreens, and human dermal exposures are relatively high. Research suggests potential differences in the toxicity of anatase and rutile crystalline forms of TiO2. Additionally, transition metal dopants are frequently used to enhance physicochemical properties of TiO2, and the toxicity of these nanoparticles are not extensively studied. Therefore, this work examined the keratinocyte toxicity and in vivo skin allergy responses after treatment with 30 nm anatase, 30 nm rutile, or <100 nm Mn-doped TiO2 nanoparticles. After a 24-hour exposure, there were no differences in keratinocyte cytotoxicity; however, Mn-doped TiO2 nanoparticles induced significant in vitro ROS generation and in vivo skin swelling responses in a model of allergic contact dermatitis.

CTAB modified TiO2 supported on HZSM-5 zeolite for enhanced photocatalytic degradation of azophloxine

A thin layer of titanium dioxide was supported on HZSM-5 zeolite via a sol-gel route. Cetyltrimethyl ammonium bromide (CTAB) was used to improve the porosity of the supported anatase TiO2. The influences of CTAB on the physicochemical properties of TiO2(n)/HZSM-5 composites were examined. The SEM and TEM images proved the loading of TiO2 layer on the surface of HZSM-5 zeolite. The absorption edge of TiO2(n)/HZSM-5 composite prepared using CTAB moved to longer wavelength region, and the bandgap energies of the composites were approximately 3.0 eV. Both the surface area and the pore volume of TiO2(n)/HZSM-5 composites were enlarged after using CTAB. Micropores were produced in the TiO2 layer after removing CTAB during the calcination process. The number of hydroxyl radicals produced under irradiation was in accordance with photocatalytic activity of the composites, and the photoluminescence intensity was also related to photocatalytic activity of the composites. The TiO2(3)/HZSM-5 sample obtained using 3 g CTAB had the maximum activity. The first order reaction rate constants for azophloxine degradation were 0.02823, 0.01842 and 0.01456 min−1 for TiO2(3)/HZSM-5, TiO2(0)/HZSM-5 and TiO2, respectively. The major organic groups in azophloxine molecule were degraded on TiO2(3)/HZSM-5 after 90 min of reaction.

The magnetism of titanium-defected undoped rutile TiO2: first-principles calculations.

The physicochemical properties of TiO2 are largely dependent on the defects. Here, using first-principles calculations, we report a systematic investigation of the magnetic properties of Ti-defected rutile TiO2 systems. The results of our calculations show that the VTi concentration can significantly affect the size of the magnetism, and that the magnetism weakens with decreasing VTi concentration. Studies of phonon dispersion curves show that systems with lower VTi concentrations of 8.33% and 6.25% are kinetically stable. Further detailed calculations on the Ti11O24 system indicate that the magnetism mainly originates from four of the six nearest-neighbor O atoms to the Ti vacancy, but much less from the other two. The magnetic ground states are discussed, and the results show that for the Ti11O24 system, the ferromagnetic (FM) state of the four nearest-neighbor O atoms to the Ti vacancy is the magnetic ground state, and for the Ti22O48 system, the FM state of the two vacancies is the magnetic ground state. In addition, our calculations also indicate that the magnetic properties of Ti-defected TiO2 can be tuned via strain engineering. In general, this metal-defected TiO2 represents a novel kind of semiconductor. Research into the magnetic properties reported in this paper can enrich theoretical knowledge in this area and provide more potential candidates for TiO2-based materials.

New Materials Based on Cationic Porphyrins Conjugated to Chitosan or Titanium Dioxide: Synthesis, Characterization and Antimicrobial Efficacy.

The post-functionalization of 5,10,15-tris(1-methylpyridinium-4-yl)-20-(pentafluorophenyl)porphyrin tri-iodide, known as a highly efficient photosensitizer (PS) for antimicrobial photodynamic therapy (aPDT), in the presence of 3- or 4-mercaptobenzoic acid, afforded two new tricationic porphyrins with adequate carboxylic pending groups to be immobilized on chitosan or titanium oxide. The structural characterization of the newly obtained materials confirmed the success of the porphyrin immobilization on the solid supports. The photophysical properties and the antimicrobial photodynamic efficacy of the non-immobilized porphyrins and of the new conjugates were evaluated. The results showed that the position of the carboxyl group in the mercapto units or the absence of these substituents in the porphyrin core could modulate the action of the photosensitizer towards the bioluminescent Gram-negative Escherichia coli bacterium. The antimicrobial activity was also influenced by the interaction between the photosensitizer and the type of support (chitosan or titanium dioxide). The new cationic porphyrins and some of the materials were shown to be very stable in PBS and effective in the photoinactivation of E. coli bacterium. The physicochemical properties of TiO2 allowed the interaction of the PS with its surface, increasing the absorption profile of TiO2, which enables the use of visible light, inactivating the bacteria more efficiently than the corresponding PS immobilized on chitosan.

Photoactive catalysts for effective water microbial purification: Morphology-activity relationship

Significant enhancement in the performance of antibacterial bioactive materials in water purification has historically been achieved through the use of optimized nanostructured systems. This report demonstrates the dependance of the antibacterial performance of Titania on its morphology and the method of synthesis for the application of water microbial purification. In this regard, TiO2 with different morphologies, including nanoparticles (NPs), nanofibers (NFs) and nanotubes (NTs), were synthesized using different techniques and their antimicrobial properties were studied. Upon UV irradiation, hydrothermally synthetized-TiO2 NTs showed the highest efficiency among the other architectures in deactivating E. coli (∼96.7%). Several factors play a significant role in determining the antibacterial activity of TiO2. These factors were examined and analysed in this report, including the crystalline phase, surface hydroxyls, physicochemical properties of TiO2 as well as experimental conditions.

Physicochemical properties of TiO2–SiO2 xerogel modified by hydrogen peroxide

How the specific surface area and the amorphous-to-crystalline titania phase ratio in TiO2–SiO2 (14 mol % TiO2) xerogels change during the fivefold repeated cycles comprising the hydrogen peroxide treatment of the xerogel followed by drying and calcining of the binary material, was traced by the BET method, X-ray powder diffraction, and IR spectroscopy.

Efficiency enhancement of dye-sensitized solar cells by use of ZrO2-doped TiO2 nanofibers photoanode

Due to the good stability and convenient optical properties, TiO2 nanostructures still the prominent photoanode materials in the Dye Sensitized Solar Cells (DSCs). However, the well-known low bandgap energy and weak adsorption affinity for the dye distinctly constrain the wide application. This work discusses the impact of Zr-doping and nanofibrous morphology on the performance and physicochemical properties of TiO2. Zr-doped TiO2 nanofibers (NFs), with various zirconia content (0, 0.5, 1, 1.5 and 2wt%) were prepared by calcination of electrospun mats composed of polyvinyl acetate, titanium isopropoxyl and zirconium n-propoxyl. For all formulations, the results have shown that the prepared materials are continuous, randomly oriented, and good morphology nanofibers. The average diameter decreased from 353.85nm to 210.78nm after calcination without a considerable influence on the nanofibrous structure regardless the zirconia content. XRD result shows that there is no Rutile nor Brookite phases in the obtained material and the average crystallite size of the sample is affected by the presence of Zr-doping and changed from 23.01nm to 37.63nm for TiO2 and Zr-doped TiO2, respectively. Optical studies have shown Zr-doped TiO2 NFs have more absorbance in the visible region than that of pristine TiO2 NFs; the maximum absorbance is corresponding to the NFs having 1wt% zirconia. The improved spectra of Zr-doped TiO2 in the visible region is attributed to the heterostructure composition resulting from Zr-doping. The absorption bandgaps were calculated using Tauc model as 3.202 and 3.217 for pristine and Zr (1wt%)-doped TiO2 NFs, respectively. Furthermore, in Dye-sensitized Solar Cells, utilizing Zr (1wt%)-doped TiO2 nanofibers achieved higher efficiency of 4.51% compared to the 1.61% obtained from the pristine TiO2 NFs.

Continuous microwave flow synthesis (CMFS) of nanosized titania: Structural, optical and photocatalytic properties

In this study we have used continuous microwave flow synthesis (CMFS) technique to synthesize nanosized titania (TiO2). The effect of microwave power (MwP) on the physicochemical properties of TiO2 has been evaluated. Particle morphology and degree of crystallinity were studied using TEM and XRD respectively. The specific surface area was quantified by using BET method and catalytic degradation of methylene blue (MB) was also measured. The UV–vis studies identified a red-shift in the energy bandgap (Eg= 2.95eV) of TiO2 and the photoluminescence (PL) study revealed a significant reduction in the surface oxygen defects under the influence of increased MwP. This study has demonstrated that, due to the visible region Eg, TiO2 nanoparticles can be used effectively as a photocatalyst and as photovoltaic solar cell material.

Effect of a Chelating Agent on the Physicochemical Properties of TiO2: Characterization and Photocatalytic Activity

In the current study, it was found that the physiochemical properties of TiO2 are effected with formic acid as a chelating agent in a sol–gel process. From XRD studies it was revealed that due to the chelation of formate group with titanium precursor, anatase/brookite mixture of 86:14 is obtained while the control sample which has been prepared without formic acid showed pure anatase at 400 °C. FTIR studies indicated that, the formate group favored a monodentate mode of coordination with titanium precursor under the effect of addition of increasing amount of formic acid, while under the effect of increasing titanium precursor content the formate group is chelated with titanium atoms in a bidentate bridging mode. In addition, from the FTIR study it was demonstrated that increasing the amount of water in the hydrolysis step, a reduction in the intensity of the carboxylate (COO−) stretches was observed indicating that the titania formate bridging complex becomes weaker, resulting in a weakened titanium gel network structure which could readily collapse during calcination favoring early rutile formation. Raman spectroscopy showed that as a result of sample composite nature and presence of oxygen vacancies as demonstrated by PL analysis causes the broadening and frequency shifting of the Raman bands. Photocatalytic studies demonstrated that the formic acid modified sample composed of anatase/rutile mixture of 94:6 calcined at 600 °C show significantly higher catalytic activity compared to the control sample prepared under similar conditions. Kinetic analysis show first order kinetics for the decomposition of methylene blue, a rate constant (kapp) of 0.074 min−1 was obtained with anatase/rutile (94:6) mixture which is even higher than the Degussa P25 (0.067 min−1).

Highly Selective Deethylation of Rhodamine B on Prepared in Supercritical Fluids

Pure phase anatase TiO2nanoparticles with sizes of 5–8 nm and varying crystallinity were synthesized in supercritical isopropanol/water using a continuous flow reactor. Their photodegradation of rhodamine B (RhB) was evaluated under visible light irradiation. The as-prepared TiO2nanoparticles show much higher photodegradation efficiencies than commercial Degussa P25 TiO2. Moreover, the photodegradation of RhB on the as-prepared TiO2follows a different process from that on P25 TiO2, quicker N-deethylation and slower cleavage of conjugated chromophore structure. Based on PXRD, TEM, and BET measurements, these two photodegradation properties have been explained by the physicochemical properties of TiO2.

Physicochemical properties of TiO2 (anatase) prepared by the centrifugal thermal activation of hydrated titanium dioxide

The physicochemical properties of titania (anatase) prepared from hydrated titanium dioxide by centrifugal thermal activation (CTA) at 140–700°C were studied. It was found that the microstructure and the texture parameters of anatase prepared by the above method were considerably different from those of the samples prepared by the traditional thermal decomposition of titanium hydroxide. The conditions of centrifugal activation exerted a considerable effect on the structure and the texture parameters of the resulting anatase. The crystal structure of anatase prepared at a temperature lower than 650°C was imperfect, and it approached a regular structure only at a temperature of >650°C. At temperatures higher than 300°C, the samples of TiO2 prepared using CTA were characterized by higher specific surface areas, fine pore structures, and comparable mesopore volumes, as compared with the samples prepared by commonly used synthetic methods.

Physicochemical Properties of the Dispersion of Titanium Dioxide in Organic Media by Using Zetametry Technique

The study of the physicochemical properties of solids dispersed in organic media, and especially the dispersion of titanium dioxide (TiO2) particles, is very important in many industrial processes. The aim of this study is to determine the acid-base behavior of TiO2 particles dispersed in organic media by measuring their zeta potential by electrophoresis technique. After normalized the electron donor (DN′)and acceptor numbers (AN′)of organic solvents, we applied our new method to determine the donor (DN S ′) and acceptor numbers (AN S ′) of TiO2 by using a Mathematica program. The effect of pretreatment temperature on physicochemical properties of TiO2 was also studied. Results obtained showed that DN S ′ values of TiO2 are comprised between 36 and 47 (or 14 and 19 kcal/mol) and AN S ′ values comprised between 10 and 17.

Evaluation of Titanium Dioxide as a Pharmaceutical Excipient for Preformulation of a Photo-Labile Drug: Effect of Physicochemical Properties on the Photostability of Solid-State Nisoldipine

To characterize the photocatalytic activity of TiO2 via solid-state reaction, the relationship between the physicochemical properties and photocatalytic activity of TiO2 was investigated and estimated from the results of photodegradation of nisoldipine. The photodegradation of nisoldipine was significantly enhanced by addition of TiO2. Two degradation products, nitroso-phenylpyridine derivative and nitro-phenylpyridine derivative, were formed. The degree of photocatalytic activity of TiO2 was quite different between the various types of TiO2 investigated, even when the crystalline phase was the same. As a result of the investigations into the relationship between the photocatalytic activity and physicochemical properties of TiO2, it was found that for the rutile form the photocatalytic activity has good correlation with specific surface area of TiO2, but poor correlation with water loss on drying of TiO2. However, for the anatase form, the photocatalytic activity has good correlation with water loss on drying of TiO2, but poor correlation with specific surface area. Moreover, it was found that the crystallinity of TiO2 has a moderate correlation with the photocatalytic activity of both crystal forms of TiO2. These results suggest that a degree of photocatalytic activity of TiO2 depends on the various physicochemical properties of each type of TiO2 investigated.