Hydrolysis Of Titanium Butoxide Research Articles

Investigating the interfacial properties of halide perovskite/TiOx heterostructures for versatile photocatalytic reactions under sunlight.

Heterostructures of metal halide perovskites and TiOx are efficient photocatalytic materials owing to the combination of the advantages of each compound, specifically the high absorption coefficients and long charge-carrier lifetimes of perovskites, and efficient photocatalytic activity of TiOx. However, chemical reduction of CO2 using PNC/TiOx heterostructures without organic solvents has not been reported yet. Here, we report the first solvent-free reduction of CO2 using amorphous TiOx with embedded colloidal perovskite nanocrystals (PNCs). The combination was obtained by carrying out hydrolysis of titanium butoxide (TBOT) on the PNC surface without high-temperature calcination. We proposed a mechanism involving photoexcited electrons being transferred from PNCs to TBOT, enabling photocatalytic reactions using TiOx under visible-light excitation. We demonstrated efficient visible-light-driven photocatalytic reactions at PNC/TiOx interfaces, specifically with a CO production rate of 30.43 μmol g-1 h-1 and accelerated degradation of organic pollutants under natural sunlight. Our work has provided a simple path toward both efficient CO2 reduction and photocatalytic degradation of organic dyes.

Fabrication of photo-responsive moth eye-like patterned poly(vinyl alcohol) films selectively containing TiO2 nanoparticles in the microdome

Moth eye-like patterned poly(vinyl alcohol) (PVA) films selectively containing titanium dioxide (TiO2) nanoparticles in the microdome were fabricated using polystyrene honeycomb patterned porous film as a template in which TiO2 nanoparticles are pore-filled. The template was prepared by in situ pore filling of TiO2 nanoparticles by the modified breath figure method, wherein the hydrolysis of titanium butoxide was performed in the condensed water droplets as microreactors. The moth eye-like patterned PVA film selectively containing TiO2 nanoparticles in the microdome was transparent almost similar to the pristine PVA flat film. However, the film showed a reversible photochromism that changes to blue color by UV illumination and recovered by visible light. The obtained films may have potential applications in anti-reflective surfaces, photo-catalytic surfaces, opto-electronics, and photo-catalytic devices.

In-situ pore filling of TiO2 nanoparticles in honeycomb patterned porous films: A modified breath figure method

Polystyrene (PS) honeycomb patterned porous films filled with titanium dioxide (TiO2) nanoparticles were prepared by a modified breath figure method. The honeycomb patterned porous films filled with TiO2 nanoparticles were obtained by pouring titanium butoxide over partially dried PS solution during the fabrication of the PS films under humid conditions. TiO2 nanoparticles were obtained by the hydrolysis of titanium butoxide in the condensed micro water droplets at the PS solution/air interface. Morphology, elemental mapping, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, and UV−Visible analysis support the formation of TiO2 nanoparticles in the honeycomb patterned pores. XRD studies showed that the formed TiO2 nanoparticles are anatase. Photo-activity of the incorporated TiO2 nanoparticles was examined by the change of the water contact angle of the films before and after UV irradiation. Water contact angles was decreased by UV irradiation, implying the transformation of the surface from hydrophobic to hydrophilic due to the photo-induced wettability by TiO2.

Preparation of a p-n heterojunction BiFeO3@TiO2 photocatalyst with a core–shell structure for visible-light photocatalytic degradation

Magnetically separable bismuth ferrite (BiFeO3) nanoparticles were fabricated by a citrate self-combustion method and coated with titanium dioxide (TiO2) by hydrolysis of titanium butoxide (Ti(OBu)4) to form BiFeO3@TiO2 core–shell nanocomposites with different mass ratios of TiO2 to BiFeO3. The photocatalytic performance of the catalysts was comprehensively investigated via photocatalytic oxidation of methyl violet (MV) under both ultraviolet and visible-light irradiation. The BiFeO3@TiO2 samples exhibited better photocatalytic performance than either BiFeO3 or TiO2 alone, and a BiFeO3@TiO2 sample with a mass ratio of 1:1 and TiO2 shell thickness of 50–100 nm showed the highest photo-oxidation activity of the catalysts. The enhanced photocatalytic activity was ascribed to the formation of a p-n junction of BiFeO3 and TiO2 with high charge separation efficiency as well as strong light absorption ability. Photoelectrochemical Mott–Schottky (MS) measurements revealed that both the charge carrier transportation and donor density of BiFeO3 were markedly enhanced after introduction of TiO2. The mechanism of MV degradation is mainly attributed to hydroxyl radicals and photogenerated electrons based on energy band theory and the formation of an internal electrostatic field. In addition, the unique core–shell structure of BiFeO3@TiO2 also promotes charge transfer at the BiFeO3/TiO2 interface by increasing the contact area between BiFeO3 and TiO2. Finally, the photocatalytic activity of BiFeO3@TiO2 was further confirmed by degradation of other industrial dyes under visible-light irradiation.

Di(2-pyridyl)ketone stabilized titanium dioxide nanoparticles for the room temperature processed electron transporting layer in organic photovoltaics

Monodisperse TiO2 nanoparticles are obtained through hydrolysis of titanium butoxide in the presence of di(2-pyridyl)ketone (DPK) and para-toluenesulfonic acid. The DPK ligand stabilized the surface of the TiO2 nanoparticle through complexation with TiO2. DPK stabilized TiO2 (TNP-DPK) can be dispersed without aggregation in alcoholic solutions at concentrations higher than 1 M. The synthesized particles have 4–5 nm size and spherical shape at amorphous phase. The atomic force microscope image reveals that only 0.1 wt% of TNP-DPK solution can form a conformal and dense film on top of the active layer. The TNP-DPK solution is used for an electron transporting layer (ETL) in organic photovoltaics (OPV) that utilizing poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3,4-b]thiophene-)-2-carboxylate-2-6-diyl)] (PTB7-Th) as a photoactive layer. The power conversion efficiency of the OPV is significantly improved from 7.18% to 9.08% by inserting the TNP-DPK layer between photoactive layer and Al electrode. Based on the internal quantum efficiency and transient photo voltage experiments, the TNP-DPK layer is found to improve the charge collection efficiency and reduce the charge recombination at the active layer/electrode interface. These results clearly show that the solution processed TNP-DPK layer can play a role as an efficient ETL in OPVs.

Tailoring Imprinted Titania Nanoparticles for Purines Recognition

Molecular imprinted titania nanoparticles were developed for selective recognition of purines, for example, guanine and its final oxidation product uric acid. Titania nanoparticles were prepared by hydrolysis of titanium butoxide as precursor in the presence of pattern molecules. The morphology of synthesized nanoparticles is evaluated by SEM images. Recognition characteristics of imprinted titania nanoparticles are studied by exposing them to standard solution of guanine and uric acid, respectively. The resultant change in their concentration is determined by UV/Vis analysis that indicated imprinted titania nanoparticles possess high affinity for print molecules. In both cases, nonimprinted titania is taken as control to observe nonspecific binding interactions. Cross sensitivity studies suggested that imprinted titania is at least five times more selective for binding print molecules than competing analyte thus indicating its potential for bioassay of purines.

Template-free synthesis of mesoporous anatase titania hollow spheres and their enhanced photocatalysis

Monodispersed mesoporous anatase titania (TiO2) hollow microspheres with controllable morphology and size are prepared via thioglycolic acid (TGA) chemically induced self-assembly for the first time. The formation process of TiO2 hollow spheres consists of three steps: hydrolysis of titanium butoxide (TBT) forming Ti-oxo clusters followed by connecting TGA via hydrogen bonding, assembly of the Ti-oxo clusters to solid spheres, and transformation of the TiO2 solid spheres into hollow spheres through the synergistic effect of thermodynamic (Ostwald ripening process) and kinetic (gas release) factors. TGA molecules firstly provide acidic conditions slowing down the hydrolysis rate of TBT, then control the formation of solid spheres, and finally create hollow structures. The prepared TiO2 hollow sphere with mesoporous structure has a large specific surface area (292.20 m2 g−1). Photocatalytic degradation of methyl orange (MO) by the TiO2 hollow spheres after reflux treatment improves significantly, owing to removal of TGA molecules from the TiO2 hollow spheres. Moreover, photocatalytic water splitting of highly crystalline TiO2 hollow spheres decorated with Pt nanoparticles exhibits an impressive performance for producing H2 (0.477 mmol h−1).

Synthesis of mesoporous TiO2 spheres and aggregates by sol–gel method for dye-sensitized solar cells

Mesoporous microspheres of anatase TiO2 were synthesized by hydrolysis of titanium butoxide in butanol. The TiO2 micospheres were about 0.5μm in size, composed of primary nanoparticles of about 10nm, and the specific surface area increased by addition of triblock copolymer (Pluronic F127). TiO2 aggregates with irregular shape were formed by hydrothermal treatment. Before and after calcination, the crystallinity of TiO2 aggregates was high although the specific surface area decreased. The cell efficiency of TiO2 sphere electrode increased by F127 addition. Furthermore, TiO2 aggregate electrode exhibited an efficiency of 5.6%, which was much higher than those of TiO2 spheres with F127 and commercial TiO2 nanoparticles (P25) electrodes. It was confirmed that the high crystallinity of TiO2 was important to improve the photovoltaic properties as well as large surface area.

Fe-modified TiO 2 photocatalysts for the oxidative degradation of recalcitrant water contaminants

Fe–TiO 2 with enhanced photocatalytic oxidation activity was synthesized by hydrolysis of titanium butoxide. Sol–gel process leads to less active Fe–TiO 2 particles than bare TiO 2; meanwhile, the hydrothermal synthesis of Fe–TiO 2 seems to promote the stabilization of Fe 3+ in the TiO 2 structure promoting the photo-oxidation activity of TiO 2 towards the degradation of azo-dyes and the inactivation of Escherichia coli ( E. coli) in water. Photocatalysts were characterized by X-ray diffraction (XRD), diffusive reflectance spectrophotometry (DRS), and N 2 adsorption–desorption. The TiO 2 synthesized by the hydrothermal synthesis reaches the TiO 2 Degussa P-25 photo-oxidation activity towards the degradation of orange II. Furthermore, Fe loading of TiO 2 in hydrothermal synthesis improves remarkably the photoactivity of HT. The comparative performance of the photocatalysts towards the direct photo-oxidation of iodide, the photocatalytic degradation of orange II and the photocatalytic disinfection of water infected with E. coli suggested different mechanisms of oxidation: a surface-hole-oxidation mode for hydrothermally synthesized TiO 2 particles and a homogeneous phase oxidation mode promoted by OH radicals produced in the TiO 2 P25 surface.

Photocatalytic degradation of dodecyl-benzenesulfonate over TiO 2–Cu 2O under visible irradiation

A series of TiO 2–Cu 2O mixed oxides were prepared by the hydrolysis of titanium butoxide and reduction of copper acetate with hydrazine. These composite oxides were characterized by X-ray diffraction (XRD), inductively coupled plasma spectrometry (ICP), high-resolution transmission electron microscopy (HRTEM), N 2 adsorption and UV–vis techniques. Photocatalytic degradation of dodecyl-benzenesulfonate (DBS) under visible irradiation was performed, and effects of composition of catalysts and reaction conditions were studied. It was observed that TiO 2–Cu 2O composite oxides exhibited better photocatalytic activity than Cu 2O or TiO 2 alone. Among these composite oxides, the 5%TiO 2–Cu 2O displayed the highest activity, and the degradation percentage of DBS and COD reached 97.3% and 65%, respectively. In addition, it was found that the decomposition of DBS followed the first-order kinetics and the adsorption of DBS followed the Langmuir model. Oxygen in solution played a vital role in the elimination of COD.

Formation Mechanism of Amorphous TiO2 Spheres in Organic Solvents. 1. Roles of Ammonia

The roles of ammonia in the formation of monodisperse amorphous TiO2 spheres through hydrolysis of titanium butoxide in its homogeneous solution of a mixed solvent of butanol/acetonitrile with ammonia have been investigated. The hydrolysis of titanium butoxide was originally so fast as to finish almost instantly within a few seconds even in the absence of ammonia that the effect of ammonia as an accelerator of the hydrolysis of titanium butoxide was not observed. Instead, ammonia was found to play key roles as an accelerator of the precipitation of the hydrolysis product, as an inhibitor of the coagulation of the growing hydroxide particles, and as a promoter for production of highly spherical particles. All of these effects are deemed to be mainly due to the reduced affinity between butanol and the hydroxide monomer joined with ammonia through hydrogen bonding. In addition, ammonia was revealed to work as a powerful accelerator of the condensation of the hydroxide monomer, which proceeds not in the solution phase but only in the individual particles during aging after precipitation. The accelerated condensation by ammonia was explained in terms of the promoted release of hydroxide ion of the monomer in each particle by the nucleophilic coordination of ammonia to its titanium ion. These mechanisms widely applicable to other sol−gel systems of transition metal oxides as well have been discussed in comparison with silica particle systems.

Formation Mechanism of Amorphous TiO2 Spheres in Organic Solvents 2. Kinetics of Precipitation

This paper (Part 2) is a report on the kinetics of precipitation in a sol−gel system developed in Part 1 of this series for the formation of monodispersed amorphous TiO2 spheres through hydrolysis of titanium butoxide (TBO) in its homogeneous solution of a mixed solvent of butanol/acetonitrile (vol. ratio 1:1) with ammonia. The precipitation was performed by adding 5 cm3 of a composite solution of 1.0 M H2O and 0.20 M NH3 to 5 cm3 of 0.10 M TBO in 1 s and the following aging, under constant agitation at 25 °C. From Nielsenʼs chronomal analysis on the change of the electric conductivity of the system, 83% of the precipitation of the hydrolysis product was found to be completed by 2.5 s from the start of the admixing. The preceding hydrolysis of TBO was likely to have finished earlier than the start of the nucleation of the product particles, as revealed from the kinetic analysis on the hydrolysis and precipitation processes. The particle growth proceeded through a two-step process consisting of a very fast initial step finished at latest by 2.5 s and the following much slower one. The cause of the two-step process was explained in terms of the high initial reactivity of the particle surfaces prior to the adsorption of ammonia, as well as the possibility of precipitation of higher clusters under the extremely high supersaturation, and the following deactivation of the particle surfaces by retarded adsorption of ammonia. The second step was found to proceed in a third-order reaction-controlled kinetics supposedly by direct deposition of the trimer of hydrolysis product in equilibrium with the monomer and dimer. Finally, mechanisms of particle formation in relevant sol−gel systems of TiO2 and ZrO2 are discussed in the light of the present results.

Formation Mechanism of Amorphous TiO2 Spheres in Organic Solvents 3. Effects of Water, Temperature, and Solvent Composition

In a sol−gel system for the formation of spherical hydrous titania particles by hydrolysis of titanium butoxide (TBO) in a mixed solvent of n-butanol and acetonitrile with ammonia at 25 °C, effects of water content, temperature, and solvent composition have been studied. Water and ammonia were admixed with TBO in ca. 1 s, and the hydrolysis of TBO and about 80% of the subsequent precipitation of the hydrolysis product were completed earlier than 2.5 s in a standard homogeneous system with a butanol/acetonitrile (vol. ratio 1:1) solvent, as found in the preceding study of this series. In the standard system, dramatic size reduction was observed with increase in the content of water. The marked size reduction was explained in terms of enhanced nucleation of the hydrolysis product by the increase in supersaturation ratio due to the drop of the solubility of the hydrated hydrolysis product with the excess water. But, even though the temperature was raised up to 80 °C from 25 °C, the final mean particle size in the standard system (ca. 0.45 μm) was virtually left unchanged. From this striking result, it was concluded that the nucleation of the hydrolysis product started after the complete hydrolysis of TBO in the homogeneous system. The homogeneous system turned to a heterogeneous TBO emulsion system under agitation, when the temperature was lowered to 5 °C, the volume fraction of acetonitrile in the mixed solvent was raised to 0.6 or higher, or butanol was replaced by a higher alcohol such as hexanol or octanol. In the emulsion systems, titania particles were found to be formed in each solvent phase by dissolution of the TBO droplets, but their size distribution was broad due to constant nucleation near the surfaces of the TBO droplets. Also, dramatic reduction of the final particle size with the increasing fraction of acetonitrile was observed as well, as explained in terms of the constant nucleation near the surfaces of TBO droplets in addition to the lowered growth rate of the generated nuclei with the reduction of the solubility of the hydrolysis product due to the low affinity of acetonitrile to the butanol-solvated hydroxide monomer. A possibility of direct conversion of the alkoxide droplets to titania particles was also discussed.

Effects of Surfactant Composition and Concentration on Shape, Size and Photocatalytic Activity of TiO2 Nanoparticles

Various shapes and sizes, including spherical, cubic nanoparticles and hexagonal nanorods with the dimensions of 50-500nm, of TiO2 were prepared through hydrolysis of titanium butoxide in sol-gel method with the introduction of different surfactant composition and concentrations during preparation. Prepared TiO2 nanoparticles were studied for photocatalytic decomposition of methyl orange (MO) in fixed film batch reactors. The results showed that shape, size and photocatalytic activity of TiO2 depend not only on surfactant composition but also on surfactant concentration. Photocatalytic decomposition of MO followed the first order kinetic reaction. The analysis of reaction rate constants showed that the shape is more important than the size in determining the photocatalytic activity of shape- and size-controlled TiO2 nanoparticles. TiO2 nanorods had higher photocatalytic activities than spherical and cubic TiO2 nanoparticles.

Photoelectrochemical characterisation of TiO 2 thin films derived from microwave hydrothermally processed nanocrystalline colloids

Titanium dioxide (TiO 2) thin films fabricated with different TiO 2 colloids were characterised using photoelectrochemical techniques. TiO 2 colloids were firstly prepared via hydrolysis of titanium butoxide and peptisation process with no hydrothermal process (labelled as NP). The resulting colloids were then subjected to different hydrothermal processes, i.e., 15-h convection hydrothermal (labelled as CH) treatment; 5-, 10- and 15-min microwave hydrothermal treatment (labelled as M5, M10 and M15, respectively). The colloids were used to prepare TiO 2 thin films on conducting indium-doped tin oxide (ITO) substrates (i.e., CH, M15, M10, M5 and NP electrodes, respectively) using a controlled dip-coating technique. The experimental results demonstrate that the oxidation capacities of the electrodes for water and glucose are in the order of CH > M15 > M10 > M5 > NP. In contrast, the oxidation capacities of the electrodes for potassium hydrogen phthalate (KHP) are in the order of M15 > M10 > CH. It was also found that the CH electrode could be easily poisoned by high concentration of KHP, while microwave-processed electrodes (M15, M10 and M5) are immune from the KHP poisoning. The results presented demonstrate that microwave hydrothermal processing is a promising alternative method to the traditional convection hydrothermal treatment of colloids that provides electrodes with increased photocatalytic properties for the oxidation processes of adsorption-based organic compounds, such as KHP.

Rheological Measurements in Titania Gels Synthesized from Reverse Micelles

TiO2 sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant W o = [H2O]/[AOT] and changing R = [H2O]/[Ti(BuO)4]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol-gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters (G′, G″ and η*) as a function of time at different frequencies. The possibility to apply standard percolation theory was discussed. The application of two alternative growth models-either “fractal growth model” or “nearly linear growth model”-has been analysed.

Rheological measurements in titania gels synthesized from reverse micelles

TiO 2 sol and gel systems have been synthesized by hydrolysis of titanium butoxide in microemulsions W/O. Different systems compositions were prepared at constant W o=[H 2O]/[AOT] and changing R=[H 2O]/[Ti(BuO) 4]. Experimental measurements show a progressive increase of the viscosity with time, characteristic of a sol–gel transition. The rheology of the transition was studied by following the behavior of viscoelastic parameters ( G′, G″ and η*) as a function of time at different frequencies. The possibility to apply standard percolation theory was discussed. The application of two alternative growth models — either `fractal growth model' or `nearly linear growth model' — has been analysed.

Preparation of TiO2 Film through Hydrolysis of Titanium Butoxide and Interaction between Sensitizing Dyes and the Film

A method of preparation of stable, homogeneous and controlled thickness TiO2 film through hydrolysis of Ti(OC4H(9))(4) is introduced in detail. The structure and property of the film have been investigated by means of SEM and FT-IR techniques. The strong quenching effect between sensitizing dyes and TiO2 film is observed in their fluorescence spectra.

Alkoxy-derived fine powders of simple and complex oxides

Fine powders of ZrO2, ZrO2-Y2O3, BaTi1−xZr x O3 have been obtained by hydrolysis of alkoxides. For preparation of ZrO2-based materials precipitation from the partially hydrolyzed alkoxides solutions (sols) has been used. Barium titanate-based materials were obtained by hydroxide-alkoxide route with quick hydrolysis of titanium butoxide by excess of water on the first stage. The effect of the hydrolysis conditions on the size, shape, and specific surface area of the oxide powders has been discussed. Some considerations on comparison of the two hydrolytic techniques have been suggested.