Photocatalytic Effect Of TiO2 Research Articles

Recycling of Glass Waste by Deposition of TiO2 for the Intensification of the Photocatalytic Effect in the Purification of Wastewater

In this study, the photocatalytic effect of TiO2 (1 wt. % and 3 wt. %) deposited on the surface of sintered cathode ray tube glass was examined, as well as its effect on an E. coli strain (BL21(DE3)). DTA analysis indicated the sintering temperature for samples to be 820 °C while scanning electron microscopy (SEM)showed an intimate contact and a strong interface between the support and photocatalyst. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) was employed to establish the chemical and bonding environment of the samples. The investigations of the bacterial viability were conducted using flow cytometry, a specific cellular viability assay, while bacterial growth was measured using the turbidimetric method. The experimental results show the influence of the TiO2 concentration on the bacterial inactivation process: higher concentrations (3% wt.) have a bactericidal effect in the long term, whereas lower concentrations (1% wt.) render them inactive for a shorter time in the exponential growth stage. The preliminary results were used to calculate the efficiency of microbial inactivation and the parameters of the kinetics of inactivation using ANOVA software. The results indicate that this material could be an effective solution for water disinfection.

Environmentally Friendly UV-Protective Polyacrylate/TiO2 Nanocoatings.

The development of coatings that maintain the attractive natural appearance of wood while providing ultraviolet (UV) protection is extremely important for the widespread use of wood products. In this study, the influence of different types (powder form and aqueous dispersions) of TiO2 in an amount of 1.0 wt% by monomer weight on the properties of environmentally friendly polyacrylate (PA)/TiO2 emulsions prepared by ex situ and in situ polymerization, as well as on the UV-protective properties of the coating films, was investigated. The results showed that the addition of TiO2 significantly affected the particle size distribution of PA and the viscosity of PA varied according to the preparation method. Compared with the ex situ preparation method, in situ polymerization provides better dispersibility of TiO2 nanoparticles in PA coating film, as well as a better UV protection effect and greater transparency of the coating films. Better morphology and transparency of nanocoating films were achieved by adding TiO2 nanofillers in aqueous dispersion as compared to the addition of TiO2 in powder form. An increase in the glass transition temperature during UV exposure associated with cross-linking in the polymer was less pronounced in the in situ-prepared coating films, confirming better UV protection, while the photocatalytic effect of TiO2 was more pronounced in the ex situ-prepared coating films. The results indicate that the method of preparation has a significant influence on the properties of the coating films.

Synthesis and characterization of Eu3+ doped TiO2 thin films deposited by spray pyrolysis technique for photocatalytic application

In this study, nanocrystalline TiO2: Eu3+ thin films are successfully formed by spray pyrolysis technique deposited on glass substrate. Structure, optical, electrical, surface morphology, and photocatalytic degradation of Methylene blue have been examined. The XRD analysis illustrate the tetragonal crystal structure of films with anatase phase and reduces crystallite size linearly with increasing Eu3+ concentration. The optical properties of the films are analyzed using transmittance and reflectance spectra, which are measured using UV–vis-NIR double-beam spectrophotometer. Optical properties such as refractive index (n), extinction coefficient (k), optical conductivity (σ) and Urbach energy (Eu) have been calculated as a function of Eu3+ concentration. Film thickness were evaluated using the refractive index dependence on wavelength. The films thickness were determined as 97.13, 122.62, 123.24, 117.14 and 128.25 nm, respectively, for Eu doped TiO2 at 0,4, 6, 8 and 10 wt % doping concentration. The band gap values raised from 3.29 to 3.42 eV with increasing the Eu3+ dopant concentration. The highest electrical conductivity was found to be 3.01 × 10−2(Ω·cm)−1 at high doping level with 10 wt% Eu3+. Scanning electron microscopy (SEM) analysis indicated consistent allocation of irregular and spherical shaped grains covering the substrate surface. The average grain size in range of 82.5—51.1 nm is observed and films show porous nature. The photocatalytic effect of TiO2: Eu3+ thin films is predicted from the degradation of methylene blue (MB) at room temperature under UV light irradiation. An enhancement in photocatalytic degradation observed by increasing the amount of Eu3+ due to increase in the (electron-hole) pair production and increase of film thickness. These results make TiO2: Eu3+ thin films as attractive candidate for photovoltaic cells and other optoelectronic device applications.

Radical Species Production and Color Change Behavior of Wood Surfaces Treated with Suppressed Photoactivity and Photoactive TiO2 Nanoparticles

The use of TiO2 nanoparticles for photoprotection comprise a side effect due to the photocatalysis of the nanoparticles under UV radiation. In this work we studied how the suppression of TiO2 photocatalytic activity may affect the production of phenoxy radicals and the color of wood surfaces exposed to UV radiation. The experimental work considered the modification of TiO2 nanoparticles to reduce its photoactivity and the use electron paramagnetic resonance to test free radical production. Wood samples were treated with the different TiO2 nanoparticles and the radical production and color changes were evaluated after UV exposure. Experimental results showed that in wood samples exposed to UV radiation the use of TiO2 with suppressed photoactivity yielded increased amounts of phenoxy radicals, in comparison to samples treated with photoactive TiO2. Similar results were obtained in terms of color change, where samples treated with suppressed photoactivity TiO2 showed significantly higher color changes values, after 2000 h of UV exposure, than samples treated with photoactive TiO2. These results suggest that in wood surfaces, the photocatalytic effect of TiO2 may be crucial on the performance of the nanoparticles as photoprotective treatment.

Photoelectrochemical sensing of dopamine using gold-TiO2 nanocomposites and visible-light illumination.

A photoelectrochemical (PEC) method was developed for the determination of dopamine. It is making use of a composite prepared from gold nanoparticles and TiO2 (type P25) and placed on a fluorine-doped tin oxide (FTO) electrode. The composites are used for photoelectrical detection with improved electron transfer efficiency for photoproduction and with improved photoelectrical conversion efficiency. This is due to the excellent electrical conductivity and surface plasmon resonance absorption by gold nanoparticles, and also by the photocatalytic effect of TiO2. Dopamine binds easily to the surface of the composites and acts as an electron donor. This electrode gives a strongly enhanced photocurrent which increases linearly in the 0.1 to 100μM dopamine concentration range and has a 23nM detection limit (at S/N = 3). The electrode was operated over 15cycles of light-on and light-off states every 20s under visible-light illumination, and the sensor indicates good stability. In addition, it is selective over several possible interferents including uric acid, L-cysteine, glutathione, ascorbic acid and glucose. Graphical abstract A new gold/P25 composite-based photoelectrochemical sensing scheme for dopamine is described. Under visible light irradiation, the photocurrent response is increased with the increasing concentration of dopamine (DA).

Outstanding Performance of Hole‐Blocking Layer‐Free Perovskite Solar Cell Using Hierarchically Porous Fluorine‐Doped Tin Oxide Substrate

AbstractPerovskite solar cells (PSCs) are of great interest in current photovoltaic research due to their extraordinary power conversion efficiency of ≈20% and boundless potentialities. The high efficiency has been mostly obtained from TiO2‐based PSCs, where TiO2 is utilized as a hole‐blocking, mesoporous layer. However, trapped charges and the light‐induced photocatalytic effect of TiO2 seriously degrade the perovskite and preclude PSCs from being immediately commercialized. Herein, a simplified PSC is successfully fabricated by eliminating the problematic TiO2 layers, using instead a fluorine‐doped tin oxide (FTO)/perovskite/hole–conductor/Au design. Simultaneously, the sluggish charge extraction at the FTO/perovskite interface is overcome by modifying the surface of the FTO to a porous structure using electrochemical etching. This surface engineering enables a substantial increase in the photocurrent density and mitigation of the hysteretic behavior of the pristine FTO‐based PSC; a remarkable 19.22% efficiency with a low level of hysteresis is obtained. This performance is closely approaching that of conventional PSCs and may facilitate their commercialization due to improved convenience, lower cost, greater stability, and potentially more efficient mass production.

Preparation and antimicrobial assay of ceramic brackets coated with TiO2 thin films.

ObjectiveDifferent methods have been utilized to prevent enamel demineralization and other complications during orthodontic treatment. However, none of these methods can offer long-lasting and effective prevention of orthodontic complications or interventions after complications occur. Considering the photocatalytic effect of TiO2 on organic compounds, we hoped to synthesize a novel bracket with a TiO2 thin film to develop a photocatalytic antimicrobial effect.MethodsThe sol-gel dip coating method was used to prepare TiO2 thin films on ceramic bracket surfaces. Twenty groups of samples were composed according to the experimental parameters. Crystalline structure and surface morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively; film thickness was examined with a surface ellipsometer. The photocatalytic properties under ultraviolet (UV) light irradiation were analyzed by evaluating the degradation ratio of methylene blue (MB) at a certain time. Antibacterial activities of selected thin films were also tested against Lactobacillus acidophilus and Candida albicans.ResultsFilms with 5 coating layers annealed at 700℃ showed the greatest photocatalytic activity in terms of MB decomposition under UV light irradiation. TiO2 thin films with 5 coating layers annealed at 700℃ exhibited the greatest antimicrobial activity under UV-A light irradiation.ConclusionsThese results provide promising guidance in prevention of demineralization by increasing antimicrobial activities of film coated brackets.

Introduction of KRI’s sol–gel technologies with reference to the shape classification of the materials

KRI has been successful in conducting many sol–gel related projects. In this article, we review KRI’s sol–gel projects that fall into the following four categories: zero dimensions (particle applications), one dimension (fiber applications), two dimensions (coating applications), and three dimensions (bulk applications). (1) Zero dimensions: at KRI, we have developed a new process to not only synthesize large-sized (over 10 µm) silica particles by using a microreactor device, but also synthesize core–shell particles that eliminate the photocatalytic effect of TiO2. (2) One dimension: KRI has developed the electrospinning deposition method which is a process used to form nanofibers by discharging raw material liquid from a syringe under high voltage. We have successfully formed polysilsesquioxane (PSQ) nanofibers for application in Li batteries as separators, as well as metal oxide nanofibers such as TiO2 and ZnO. (3) Two dimensions: KRI has developed organic–inorganic hybrid hard coatings. Recently, we have focused on PSQ materials for hydrophobic coatings and hydrophilic coatings. (4) Three dimensions: we have successfully developed large-sized silica glasses as well as organic–inorganic hybrids as transparent materials for bulk applications.

The hierarchical porous structure of substrate enhanced photocatalytic activity of TiO2/cementitious materials

Although the use of TiO2 photocatalyst on cementitious materials for air purification has been developing rapidly in the last decades, the photocatalytic effect of TiO2 is significantly diminished due to the low specific surface areas, poor gas diffusion and light transmission performance of cementitious substrates. This paper presents a novel hierarchical porous structure magnesium cementitious/TiO2 photocatalyst (FMOC/TiO2) to improve the photocatalytic effect and utilization rate of TiO2 in cementitious materials. The results revealed that the hierarchical porous structure of substrate was beneficial to the dispersion of TiO2, which provided more active TiO2 sites and large catalytic areas. The good gas diffusion and light transmittance performance of substrate improved the photocatalytic effect and utilization rate of TiO2 particles. The reaction rate of gaseous acetone in FMOC/T12 (∅50*3mm) surface was measured to be about 3.87 times higher than MOC/T12 (∅50*3mm). Additionally, FMOC/T12 (∅50*3mm) also exhibited an excellent re-use performance.

Bactericidal Activity of Aqueous Acrylic Paint Dispersion for Wooden Substrates Based on TiO₂ Nanoparticles Activated by Fluorescent Light.

The photocatalytic effect of TiO2 has great potential for the disinfection of surfaces. Most studies reported in the literature use UV activation of TiO2, while visible light has been used only in a few applications. In these studies, high concentrations of TiO2, which can compromise surface properties, have been used. In this work, we have developed an acrylic-water paint dispersion containing low TiO2 content (2 vol %) for the inactivation of microorganisms involved in hospital-acquired infections. The nanoparticles and the coating have been characterized using spectroscopic techniques and transmission electron microscopy, showing their homogenous dispersion in the acrylic urethane coating. A common fluorescent light source was used to activate the photocatalytic activity of TiO2. The paint dispersion showed antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The coating containing the TiO2 nanoparticles maintained good UV stability, strong adhesion to the substrate and high hardness. Therefore, the approach used is feasible for paint formulation aimed at disinfection of healthcare surfaces.

Micropatterning of non‐crystalline methylsilsesquioxane–titania hybrid films based on their structural changes with UV irradiation

AbstractNon‐crystalline, transparent methylsilsesquioxane–titania hybrid films for application in micropatterning were prepared from methyltriethoxysilane and titanium tetrabutoxide by the sol–gel method. The hybrid films were heat‐treated at 100 °C for 1 h and then irradiated with UV light using an ultrahigh‐pressure mercury lamp. The refractive index of the film increased as the amount of incorporated TiO2 increased. No changes in hardness were observed for the films lacking TiO2 during UV irradiation, whereas adding a small amount of TiO2 caused the hardness to increase significantly following UV irradiation. These changes in the physical properties of the films with UV irradiation were caused by the cleavage of Si–C bonds in the films induced by the photocatalytic effect of TiO2. On the basis of the changes in surface profiles, and optical, chemical, and mechanical properties induced by UV irradiation, it is concluded that the methylsilsesquioxane–titania films are promising for micropatterning by photolithography.

Structural analysis of TiO2 and TiO2-Ag thin films and their antibacterial behaviors

TiO2 (rutile and anatase) thin films was first prepared using reactive sputtering, in an Ar+O2 plasma. In the 2nd stage of the experiment, various amounts (3, 7, and 10 at. %) of Ag was doped into the rutile film in order to form TiO2-Ag thin films. These films were annealed for one hour in Ar atmosphere, at 300, 400, and 500 °C. The films' structures were then examined using X-ray diffractometry. FESEM (field-emission scaning electron microscopy) was used to investigate the surface emergence of Ag particles. As for the examination of optical band gaps and absorption of these films, UV-Vis-NIR photometer was used. The results show that, in as-deposited condition, the addition of Ag might disrupt the growth of crystalline structure and cause the formation of amorphous films. After annealing, it is found that the structure tends to become anatase phase which is a metastable phase between amorphous titanium oxide and rutile. More importantly, the absorption of the Ag-doped films would be enhanced in the visible-light range. Some of the enhancement is clearly due to plasmon resonance effect. The Ag-doped samples have shown some antibacterial effect in dark. When irradiated with light, the samples show a synergistic behavior combining the bactericidal effect of Ag ions and photocatalytic effect of TiO2.

Photocatalytic effect of TiO2 on hydrothermal gasification of glucose

The hybrid process of the hydrothermal gasification method and the TiO2 photocatalysis has been developed and tested for the gasification of glucose. TiO2 powder and those loaded with Pt or Ni were used as photocatalyst. 0.05 M glucose aqueous solutions suspending the photoctalysts were reacted by the flow-type reactor system in the dark or under near-UV illumination with pressure and temperature controlled to be 30 MPa and 350-450 °C, respectively. It was found that the evolutions of hydrogen and methane from glucose could be promoted by the photocatalytic action of TiO2 under hydrothermal conditions, which was further enhanced by supporting Pt and Ni on TiO2.

Preparation of MWCNT/TiO2 Composites by Using MWCNTs and Titanium(IV) Alkoxide Precursors in Benzene and their Photocatalytic Effect and Bactericidal Activity

In this present paper, we prepared MWCNT/TiO2 composites by using pre-oxidized multi-walled carbon nanotubes (MWCNTs) with different titanium alkoxide precursors in benzene solvent. The composites were comprehensively characterized by BET surface area, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and UV-Vis absorption spectroscopy. The photoactivity of the prepared materials, under UV irradiation, was tested using methylene blue (MB) in aqueous solution. Finally, according to the results of MB removal experiment, it can be considered that the MB degradation infect mainly caused by photocatalytic effect of TiO2. Furthermore, the bactericidal test of the composites was also determined. It was indicated that MWCNT/TiO2 composites with sunlight had greater effectiveness for B. cereus, S. aureus and E. coli than any other experimental conditions.

Photooxidation of M(CO)6 (M=Mo, W) adsorbed on TiO2

Photooxidation of M(CO) 6 (M=Mo, W) adsorbed on TiO 2 has been conducted from a viewpoint of the kinetics and mechanism of the reaction and the photocatalytic effect of TiO 2 . The reaction rate was first order with respect to the surface concentration of M(CO) 6 and zero order with respect to oxygen pressure. The photocatalytic effect of TiO 2 was suggested by the fact that the reaction rate of the W(CO) 6 /TiO 2 system was considerably greater than that of W(CO) 6 /NaY zeolite. The rate constant strongly depended on the TiO 2 employed and was delineated to a direct-allowed band-gap of the TiO 2 . The photocatalytic effects of TiO 2 are tentatively suggested to result from a strongly enhanced decarbonylation of M(CO) 6 by photoinduced valence band holes, followed by rapid reactions with anionic surface oxygen species.