Preparation of Au-TiO2 Hybrid Nano Particles in Silicate Film Made by Sol-Gel Method

TiO₂ nano particles with photo catalytic property were mixed with silica alkoxides solution with HAuCl₄/4H₂O. STS02 (purchased from Ishihara Sangyo Kaisha, Ltd.) was used as TiO₂ nano particles. The average size of TiO₂ nano particles was 7 nm in diameter. The gel film coated on glass substrate was heated and then HAuCl₄/4H₂O was thermally reduced at 390 degree. The coated silica gel film doped with HAuCl₄/4H₂O and TiO₂ nano particles was turned into light blue from colorless gel film after heat treatment. The optical absorption spectrum showed the absorption peak of the film heated at 390 degree shifted to at about 650 nm compare to SiO₂ film doped with Au nano particles without TiO₂ nano particles that had absorption peak at 542 nm. On the other hand, the film formed from coating solution incorporated TiAA (titanium tetraisopropoxide chelated by acetyl acetone) as TiO₂ source instead of TiO₂ nano particles had absorption peak at 550 nm. That means there was no effect on formation of Au nano particles when TiAA was incorporated. The average size of the particles was found to be about 23 nm in diameter by TEM observation. Furthermore EDX (Energy Dispersive X-ray Fluorescence Spectrometer) analysis of nano particles in the film indicated that Au-TiO₂ nano hybrid particles were formed. Simulation results also supported that the size in diameter of Au nano particles had little influence on the absorption coefficient of the silica film doped with Au nano particles.     

Investigation of Electron Behavior in Nano‐TiO2 Photocatalysis by Using In Situ Open‐Circuit Voltage and Photoconductivity Measurements

The in situ open‐circuit voltages (V_oc) and the in situ photoconductivities have been measured to study electron behavior in photocatalysis and its effect on the photocatalytic oxidation of methanol. It was observed that electron injection to the conduction band (CB) of TiO₂ under light illumination during photocatalysis includes two sources: from the valence band (VB) of TiO₂ and from the methanol molecule. The electron injection from methanol to TiO₂ is slower than that directly from the VB, which indicates that the adsorption mode of methanol on the TiO₂ surface can change between dark and illuminated states. The electron injection from methanol to the CB of TiO₂ leads to the upshift of the Fermi level of electrons in TiO₂, which is the thermodynamic driving force of photocatalytic oxidation. It was also found that the charge state of nano‐TiO₂ is continuously changing during photocatalysis as electrons are injected from methanol to TiO₂. Combined with the apparent Langmuir–Hinshelwood kinetic model, the relation between photocatalytic kinetics and electrons in the TiO₂ CB was developed and verified experimentally. The photocatalytic rate constant is the variation of the Fermi level with time, based on which a new method was developed to calculate the photocatalytic kinetic rate constant by monitoring the change of V_oc with time during photocatalysis.     

Photolysis and photocatalysis of ibuprofen in aqueous medium: characterization of by‐products via liquid chromatography coupled to high‐resolution mass spectrometry and assessment of their toxicities against Artemia Salina

The degradation of the pharmaceutical compound ibuprofen (IBP) in aqueous solution induced by direct photolysis (UV‐A and UV‐C radiation) and photocatalysis (TiO₂/UV‐A and TiO₂/UV‐C systems) was evaluated. Initially, we observed that whereas photocatalysis (both systems) and direct photolysis with UV‐C radiation were able to cause an almost complete removal of IBP, the mineralization rates achieved for all the photodegradation processes were much smaller (the highest value being obtained for the TiO₂/UV‐C system: 37.7%), even after an exposure time as long as 120 min. Chemical structures for the by‐products formed under these oxidative conditions (11 of them were detected) were proposed based on the data from liquid chromatography coupled to high‐resolution mass spectrometry (LC‐HRMS) analyses. Taking into account these results, an unprecedented route for the photodegradation of IBP could thus be proposed. Moreover, a fortunate result was achieved herein: tests against Artemia salina showed that the degradation products had no higher ecotoxicities than IBP, which possibly indicates that the photocatalytic (TiO₂/UV‐A and TiO₂/UV‐C systems) and photolytic (UV‐C radiation) processes can be conveniently employed to deplete IBP in aqueous media. Copyright © 2014 John Wiley & Sons, Ltd.     

硼铈共掺杂纳米TiO2光催化降解三氯杀螨醇和菊酯类农药

采用溶胶-凝胶法在钛酸丁酯水解过程引入硼酸、硝酸铈,制备具有光催化活性的硼铈共掺杂纳米二氧化钛（TiO2）,经XRD、TEM、FT-IR、UV-Vis-DRS表征晶体结构,在日光灯照射下,光催化降解三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯农药。结果表明：硼铈共掺杂的TiO2只有锐钛矿型,而纯的或掺铈的TiO2有含有锐钛矿型、金红石相和少量板钛矿型,UV-Vis-DRS测定结果表明硼铈共掺杂的TiO2禁带宽度变小,硼铈共掺杂的TiO2在可见光区吸光度高于掺杂铈和不掺杂的TiO2,在420nm~850nm有强的吸收;在同样光照下对三氯杀螨醇、高氟氯氰菊酯、氟戊菊酯的降解试验证明硼铈共掺杂纳米TiO2的光催化活性高于不掺杂或只掺杂铈的TiO2。     

Solgel-hydrothermal synthesis of Tb/Tourmaline/TiO2 nano tubes and enhanced photocatalytic activity

In this study, we synthesized Tb/Tourmaline/TiO₂ nano tubes (NTs) through a solgel-hydrothermal method. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectromicroscope, scanning electron microscopy, transmission electron microscopy and UV-vis diffuse reflectance spectroscopy. The resulting Tb/Tourmaline/TiO₂ NTs exhibited higher photocatalytic activity than pure TiO₂ and TiO₂ nano particles (NPs) in the degradation of menthyl orange under UV-light. Results revealed that doping rare earth element Tb could narrow the wide band gap of TiO₂ and tourmaline could trap the photogenerated electron of TiO₂ to inhibit the recombination of photogenerated electron-hole pairs.     

Use of a photocatalytic membrane reactor for the removal of natural organic matter in water: Effect of photoinduced desorption and ferrihydrite adsorption

The photocatalytic degradation of natural organic matter (NOM) would be an attractive option in the treatment of drinking water. The performance of a submerged photocatalytic membrane reactor (PMR) was investigated with regard to the removal of NOM and the control of membrane fouling. In particular, this work focused on the adsorption and desorption of humic acids (HA) and lake water NOM at the surface of TiO₂ photocatalyts and ferrihydrite (FH) adsorbents in the PMR for water treatment. The addition of FH particles with a large sorption capacity helped remove the NOM released from TiO₂ particles, but FH suspended in water affected the photocatalysis of lake water NOM with a low specific UV absorbance (SUVA) value. To prevent the UV light being scattered by FH without any photocatalytic activity, FH particles were attached to a submerged microfiltration (MF) membrane, which contributed to a greater removal of NOM during long-term PMR operation. The further removal of NOM from aqueous solution was achieved due to the synergistic effect of TiO₂ photocatalysis and FH adsorption in PMR while minimizing the influence of photoinduced desorption of NOM. No significant membrane fouling occurred when the submerged PMR was operated even at high flux levels (>25 L/m² h), as long as photocatalytic decomposition took place.     

TiO_2/SBA-15的快速合成法及其催化性能

本文针对传统方法合成TiO2/SBA-15的诸多不足,提出了一种简单而快速合成TiO2/SBA-15的方法。利用孔道内水解法快速合成了不同负载量的TiO2/SBA-15。利用XRD、N2-吸脱附、TEM和UV-Vis对样品的晶体结构、微观形貌、光学吸收特性进行了表征,并研究了不同TiO2负载量催化剂对罗丹明B(RhB)光降解活性的影响。结果表明:利用该方法合成的TiO2/SBA-15光催化活性优于传统浸渍方法合成的TiO2/SBA-15与工业上使用的TiO2纳米颗粒。     

Nanosized TiO<Subscript>2</Subscript> particles decorated on SiO<Subscript>2</Subscript> spheres (TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>): synthesis and photocatalytic activities

Nanosized TiO₂ and nano-anatase TiO₂ decorated on SiO₂ spherical core shells were synthesized by using a sol–gel method. The synthesized pure TiO₂ nano particle and TiO₂ grafted on SiO₂ sphere with various ratios have been characterized for their structure and morphologies by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrophotometry (FTIR) and transmission electron microscopy (TEM). Their surface areas were measured using the BET method. The photocatalytic activity of all nanocomposites was investigated using methylene blue as a model pollutant. The synthesized TiO₂/SiO₂ particles appeared to be more efficient in the degradation of methylene blue pollutant, as compared to pure TiO₂ particles.     

Improved Photodegradation of Organic Contaminants Using Nano‐TiO2 and TiO2–SiO2 Deposited on Portland Cement Concrete Blocks

The photocatalytic activity of TiO₂ nanoparticles (nano‐TiO₂) and its hybrid with SiO₂ (nano‐TiO₂–SiO₂) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol–gel precursor and then characterized using XRD, SEM and UV–Vis. The grain sizes were estimated by Scherrer's equation to be around 10 nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano‐TiO₂ and nano‐TiO₂–SiO₂ solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV–Vis irradiation using blocks coated with nano‐TiO₂–SiO₂. TiO₂/PCC and TiO₂–SiO₂/PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO₂–SiO₂/PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.     

Synergistic effect of sonolysis and photocatalysis in the degradation kinetics of effluent solution

In this study, degradation of the effluent solution using sonolysis, sonocatalysis, photocatalysis and sonophotocatalysis was investigated. For this purpose, an artificial effluent solution (AES) containing Acid Black 1 and Acid Blue 62 dyestuffs was prepared. The initial AES concentration, catalyst amount, light intensity and the power of ultrasound energy were chosen as the reaction parameters.The degradation rate of AES followed the pseudo-first order kinetics inconcentration of artificial effluent solution. The results showed that the sonophotocatalysis (US + UV + TiO₂) was more effective in the degradation than sonolysis (US), sonocatalysis (US + TiO2) and photocatalysis (UV + TiO₂) performed individually. The highest and lowest degradation rates were obtained in sonophotocatalytic process and sonolytic process (US), respectively. It was found also that the synergistic effect between sonolysis and photocatalysis processes is the main reason why the maximum degradation is achievable in the sonophotocatalytic process.     

Experimental study for adsorption and photocatalytic reaction of ethyl methylphosphonate molecule as organophosphorus compound adsorbed at surface of titanium dioxide under UV irradiation in ambient condition

The adsorption and photocatalytic degradation of Ethyl methylphosphonate (EMPA) on powdery TiO₂ film has experimentally investigated using attenuated total reflection-infrared Fourier transform spectroscopy (ATR-FTIR) in ambient condition. Characteristic IR frequency as P-O-C vibration mode as EtO was observed by EMPA adsorbed at the surface of TiO₂. By TiO₂ photocatalysis, the adsorbed EMPA was decomposed to methyl phosphonic acid and phosphoric acid. The increment of IR intensity of which is assigned to Ti–O-P-O-Ti of EMPA was accompanied with increasing the IR peak intensity assigned to MPA. About that, we suggest that the appearance of the Ti–O-P-O-Ti of EMPA by the TiO₂ photocatalysis is regarded as acceleration of the hydrolysis of EMPA by the surface OH groups of TiO₂. The plausible adsorption structure and the photocatalytic reaction mechanism of EMPA at the surface of TiO₂ photocatalyst were elucidated.

     

The protection effect of β-CD on DNA damage induced by ultrafine TiO2

Under the photocatalysis of 365 nm ultraviolet radiation, ultrafine TiO2 caused the oxidative damage of Teasy plasmid DNA. The damage was determined by gel-electrophoresis. Then, a different dose of β-CD was added to the reaction, and the damage was restrained. The rate of damage restraining reached 97% when the mass of β-CD was 4 times as that of TiO2. Through UV scan and IR spectroscopy, it was found that the Ti-O of ultrafine TiO2 was bound with -OH of β-CD cavum and the -OH on the surface of ultrafine TiO2 disappeared, so the formation of · OH was controlled. The ultrafine TiO2 has been widely used, but it was determined to be carcinogenic by some research. The protection effect of β-CD to DNA in the molecular level takes a new look on the surface modification of nano particles to decrease the toxic effect.     

Corrosion behavior of electroless Ni–P/TiO2 nanocomposite coatings

Composite Ni–P/nano‐TiO₂ coatings were prepared by simultaneous electroless deposition of Ni–P and nano‐TiO₂ on a low carbon steel substrate. The deposition was carried out from stirred solutions containing suspended nano‐TiO₂ particles. The Ni–P and Ni–P/nano‐TiO₂ coatings before and after heat treatment were characterized by X‐ray diffraction, scanning electron microscopy and energy dispersive X‐ray spectroscopy. The micro‐structural morphologies of the coatings significantly varied with the nano‐TiO₂ content. The corrosion resistance of as‐plated and heat‐treated Ni–P and Ni–P/nano‐TiO₂ coatings was investigated by anodic polarization, Tafel plots and electrochemical impedance spectroscopic (EIS) studies in 3.5% NaCl solution. Ni–P/nano‐TiO₂ coating exhibited superior corrosion resistance over Ni–P coating. Copyright © 2015 John Wiley & Sons, Ltd.     

Characterization of TiO2 Loaded on Activated Carbon Fibers and Its Photocatalytic Reactivity

In this paper, TiO2 loaded on activated carbon fibers （ACF） was prepared by a coating treatment, followed by calcination at different temperatures in air atmosphere. The photocatalyst developed was characterized by SEM, XRD, XPS and UV-Vis adsorption spectroscopy. It was observed from SEM images that TiO2 loaded on ACF was in the form of small clusters with nanometer size. As confirmed by XRD and XPS determinations, the crystalline pattern of immobilized TiO2 was still anatase-form after calcination, and the micrographic structure and surface properties of ACF have not been damaged by the deposition process and calcination at different temperatures. Photocatalytic degradation of methylene blue （MB） in aqueous .solution was investigated using TiOE/ACF as photocatalyst. The comparison of photolysis, absorption and photocatalysis was carded out. The results indicated that the photocatalysis process of combined photocatalyst showed much higher degradation rate than that of photolysis and absorption processes. In addition, the possibility of cyclic usage of the photocatalyst was also confirmed.     

Magnetic Titanium Dioxide Nanocomposites for Surface‐Enhanced Resonance Raman Spectroscopic Determination and Degradation of Toxic Anilines and Phenols

Mesoporous M‐TiO₂ NCs, functionalized by PATP, can capture toxic anilines and phenols by azo coupling. Loading these nanodevices with Ag NPs offers the possibility for a sensitive quantitative determination of target compounds by SERRS spectroscopy, which allows multiplex detection because of the specific vibrational fingerprints. Sensitivity and selectivity can be further enhanced by concentrating the hybrid particles by an external magnet and compound‐specific binding (anilines versus phenols). The bound toxic compounds can be degraded by TiO₂‐assisted photocatalysis after removal of the loaded hybrid particles from the sample solution with an external magnet. The degradation process can be enhanced in the presence of plasmonic Ag nanostructures.     

Efficiency of various semiconductor catalysts for photodegradation of Safranin-T

Semiconductor photocatalysis often leads to partial or complete mineralization of organic pollutants. In this study, photocatalytic degradation of Safranin-T, a hazardous textile dye, has been investigated using various semiconductors such as titanium dioxide (TiO₂), zinc oxide (ZnO), bismuth oxide (Bi₂O₃), cerium oxide (CeO₂), yttrium oxide (Y₂O₃), and zirconium oxide (ZrO₂). The experiments were carried out by irradiating the aqueous solution of Safranin-T containing photocatalysts with UV and air. Maximum decolorization of Safranin-T occurred with TiO₂ (99.8%), followed by ZnO (80.3%), Bi₂O₃ (57.1%), CeO₂ (13.1%), Y₂O₃ (12.2%), and ZrO₂ (10.2%). The rate of photocatalytic degradation varied with increasing concentration of Safranin-T. The equilibrium degradation data of Safranin-T by TiO₂ and ZnO were fitted to the Langmuir and Freundlich isotherm models. The Freundlich and Langmuir model showed satisfactory fit to the equilibrium degradation data for TiO₂ and ZnO, respectively. Photocatalytic degradation of Safranin-T followed pseudo second-order kinetics.     

Reducing Photoyellowing of Wool Using Nano TiO2

Wool is the most important animal fiber used in textile industries, but its photostability is very low. Scientists have searched for new ways to increase the photostability of wool. As TiO₂ nano particles have features suitable for new applications, the UV-blocking power of nano TiO₂ may be used for protecting fabrics against UV rays. Treatment of wool with TiO₂ can be effective for controlling photodegradation. This study focused on protecting wool fabric against UV rays using nano TiO₂. To this end, oxidized and raw wool were treated with citric acid as the cross-linking agent and different concentrations of nano TiO₂. The whiteness and yellowness of wool fabric samples were reported. XRD patterns proved the existence of TiO₂ nano-particles on the wool surface. Finally, the results revealed that nano TiO₂ is a suitable UV absorber on wool fabric and its effect depends on concentration.     

Photocatalytic ozonation for degradation of 2-sec-butyl-4,6-dinitrophenol (DNBP) using titanium dioxide: effect of operational parameters and wastewater treatment

The results of degradation efficiency of 2-sec-butyl-4,6-dinitrophenol (DNBP) in a batch system by various advanced oxidation processes revealed the order of TiO₂/UV/O₃ > TiO₂/O₃ > UV/O₃ > O₃ > UV/TiO₂. All processes followed pseudo-first order kinetics. The influence of operational parameters such as initial pH, initial concentration of DNBP, ozone and catalyst dosage on the TiO₂/UV/O₃ process, which was the most significant investigated method. The ozone dosage was found to have the noticeable impact on the process; however, initial pH and TiO₂ dosage were less effective. The mineralization of 40 mg/L of DNBP and petrochemical wastewater under the obtained optimal conditions was monitored by total organic carbon and chemical oxygen demand, respectively. The results demonstrated that the TiO₂/UV/O₃ process was a very effective method for degradation and mineralization of DNBP in aqueous solutions and industrial wastewater. The degradation intermediates were identified by GC–MS.     

Synthesis and Comparative Study of Nano-TiO2 Over Degussa P-25 in Disinfection of Water

Nanostructured TiO₂ crystals were synthesized by gel to crystalline conversion. The crystals obtained were anatase form of titania averaging in 30 nm particles with an intrinsic band gap of 3.1 eV. The photocatalytic behavior was evaluated for the bactericidal effect in water, contaminated with the indicator organism Escherichia coli. The 100% photoinactivation of E. coli was achieved within 60 min with suspended nano-TiO₂. The catalytic activity of synthesized nanosample was observed to be 2.6 times more than that of commercial TiO₂ sample referred to as Degussa P-25. The photoinactivation of E. coli was tested with irradiation source of different wavelengths to substantiate the influence of particle size and nano crystallinity on electronic band structure. The photoactivity of nano titania enhanced to 1.625 times when the source of irradiation shifted from 360 to 400 nm while Degussa P-25 showed no change.     

An Unexpected Fluctuating Reactivity for Odd and Even Carbon Numbers in the TiO2‐Based Photocatalytic Decarboxylation of C2‐C6 Dicarboxylic Acids

The degradation behaviours of five straight‐chain dicarboxylic acids (from ethanedioic acid to hexanedioic acid) were compared in aqueous TiO₂‐based photocatalysis. When all other conditions were identical, the degradation rates were found to fluctuate regularly with the parity of the number of carbon atoms. Dicarboxylic acids with an even number of carbon atoms (e‐DAs) always degraded more slowly than those acids with an odd number of carbon atoms (o‐DAs). This unusual fluctuation in the reactivity for the degradation of dicarboxylic acids by TiO₂‐based photocatalysis is very closely related to the different pre‐coordination modes of the acids with the photocatalyst. Attenuated total reflection FTIR (ATR‐FTIR) of e‐DAs labelled with ¹³C showed that both carboxyl groups of the acid coordinate to TiO₂ through bidentate chelating forms. In contrast, only one carboxyl group of the o‐DAs coordinated to TiO₂ in a bidentate chelating manner, whereas the other formed a monodentate binding linkage. The bidentate chelating form with bilateral symmetric coordination did not favour degradation. Isotope‐labelling experiments were performed with ¹⁸O₂ to observe the different ways in which incorporated oxygen entered the initial decarboxylated products of e‐ and o‐DAs. For the degradation of butanedioic acid, (45.9±0.5) % of the oxygen in the formed propanedioic acid came from H₂O, whereas for pentanedioic acid, (97.4±0.2) % of the oxygen in the formed butanedioic acid came from H₂O. Our results demonstrate that in TiO₂‐based photocatalysis, the reactivity of active species, such as ^. OH/h_vb⁺, is far from non‐selective and that the attacks of these active species on organic substrates are significantly affected by the coordination patterns of the substrates on the TiO₂ surface.