Apatite-coated titanium dioxide photocatalyst for air purification

Indoor-Light-Activated Blue TiO2-Molecule-WO3 Visible Photocatalyst for Antibacterial Performance against Escherichia coli

Currently used visible light catalysts either operate with high-power light sources or require prolonged periods of time for catalytic reactions. This presents a limitation regarding facile application in indoor environments and spaces frequented by the public. Furthermore, this gives rise to elevated power consumption. Here, we enhance photocatalytic performance with blue TiO2 and WO3 complexes covalently coupled through an organic molecule, 3-mercaptopropionic acid, under indoor light. Antibacterial experiments against 108 CFU/mL Escherichia coli (E. coli) suspensions were conducted under indoor light exposure conditions. They showed a sterilization effect of almost 90% within 70 min and nearly 100% after 110 min. The complex generates reactive oxygen species (ROS), such as •OH and O2•-, under natural air conditions. We also showed that h+ and •OH are important for sterilizing E. coli using common scavengers. This research highlights the potential of these complexes to generate ROS, effectively playing a crucial role in antibacterial effects under indoor light.

Effects of Synthesis Parameters on Structure and Antimicrobial Properties of Bacterial Cellulose/Hydroxyapatite/TiO2 Polymer-Ceramic Composite Material

Bacterial cellulose (BC) is a highly pure polysaccharide biopolymer that can be produced by various bacterial genera. Even though BC lacks functional properties, its porosity, three-dimensional network, and high specific surface area make it a suitable carrier for functional composite materials. In the present study, BC-producing bacteria were isolated from kombucha beverage and identified using a molecular method. Two sets of the BC hydrogels were produced in static conditions after four and seven days. Afterwards, two different synthesis pathways were applied for BC functionalization. The first method implied the incorporation of previously synthesized HAp/TiO2 nanocomposite using an immersion technique, while the second method included the functionalization of BC during the synthesis of HAp/TiO2 nanocomposite in the reaction mixture. The primary goal was to find the best method to obtain the functionalized material. Physicochemical and microstructural properties were analyzed by SEM, EDS, FTIR, and XRD methods. Further properties were examined by tensile test and thermogravimetric analysis, and antimicrobial activity was assessed by a total plate count assay. The results showed that HAp/TiO2 was successfully incorporated into the produced BC hydrogels using both methods. The applied methods of incorporation influenced the differences in morphology, phase distribution, mechanical and thermal properties, and antimicrobial activity against Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Proteus mirabilis (ATCC 12453), and Candida albicans (ATCC 10231). Composite material can be recommended for further development and application in environments that are suitable for diseases spreading.

Morphological Structures and Self-Cleaning Properties of Nano-TiO2 Coated Cotton Yarn at Different Washing Cycles

Titanium dioxide (TiO₂) has an extraordinary photocatalytic activity and it effectively provides self-cleaning properties for cotton products. With the presence of succinic acid, it helps the adherence of the TiO₂ nanoparticles on cotton surfaces. However, the ability of succinic acid to keep the TiO₂ adhered on cotton after washing is not yet fully understood. Therefore, this study aimed to investigate the effects of washing cycles on nano-TiO₂ coated cotton yarn with the aid of succinic acid on the morphological structures and self-cleaning properties. In this study, the nano-TiO₂ was synthesized using a hydrothermal method. The cotton yarn was coated with succinic acid and was later dipped in a nano-TiO₂ nanoparticles suspension. The nano-TiO₂ coated yarn samples then underwent the 5^th, 10^th, 15^th, and 20^th wash cycles and were tested for morphological structures and self-cleaning. The self-cleaning properties of the nano-TiO₂ coated yarn were determined using the depth of colour stain. The depth of the colour stain was presented as K/S value, where K and S are corresponded to the absorption and scattering coefficients of the stained fabric, respectively. From the analysis, our synthesized nano-TiO₂ had a size of 20-50 nm range with a band gap of 3.06 eV. After coating, the nano-TiO₂ coated cotton yarn changed in its morphological structure at 5^th, 10^th, 15^th, and 20^th wash cycles, respectively. At the 20^th wash cycle, the weight (%) of the Ti element continued to decrease up to 4.45%, reducing the photocatalytic activity with the K/S value close to the stained yarn, which was about 0.4. The 5^th wash cycle maintained a good photocatalytic activity with the K/S value of 0.06 near to the K/S value of the unstained cotton yarn. The presence of succinic acid in the nano-TiO₂ coated cotton yarn provided good self-cleaning properties up to the 15^th wash cycle. By undertaking this study, an enhanced cotton property has been developed that will benefit the textile and clothing industry. This nano-TiO₂ coated cotton the has potential to be used for daily apparel and sportwear.

Studies on safety and efficacy of particles containing a mixture of hydroxyapatite–argentum–titanium oxide (HAT) and sheets coated with HAT particles to be used in masks to improve nasal allergy: II. Cellular, in vivo, and clinical studies

Purpose

We report the manufacture of particles containing a mixture of hydroxyapatite–argentum–titanium oxide (HAT), followed by attachment to nonwoven polyester fabrics to produce HAT-coated sheets (HATS) for use in masks. The purpose of the present study was to perform cellular, in vivo, and clinical studies to further examine the safety of HATS for use in masks to improve nasal allergy.

Methods

Reverse mutation tests for HAT were performed using five bacterial strains. A cellular toxicity test was performed using a Chinese hamster cell line incubated with the HATS extracts. Skin reactions after intradermal administration were examined in rabbits. Skin sensitization tests in guinea pigs were performed using the HATS extracts. HAT was administered to the nasal cavity and conjunctival sac of the rabbits. An oral administration study was performed in rats. Finally, a human skin patch test was performed using the HATS.

Results

Reverse mutation tests showed negative results. The cellular toxicity test showed that the HATS extract had moderate cytotoxicity. The intradermal skin reaction and skin sensitization tests were all negative. The administration of HAT to the nasal cavity and intraocular administration showed negative results. No toxicity was observed after oral administration of HAT powder up to a dose of 2000 mg/kg. Finally, the skin patch test result was negative.

Conclusion

Although HAT showed moderate cytotoxicity, in vivo results indicated that HAT is safe because it does not come in direct contact with cells in normal usage, and HATS is safe when used in masks.

Photocatalytic activity of TiO2-P25@n-TiO2@HAP composite films for air depollution

We report on an elaboration of new composite photocatalysts (TiO₂-P₂₅@ n-TiO₂@HAP) based on grafted size-selected 5-nm titanium-oxo-alkoxo nanoparticles on P25-TiO₂ nanoparticles and HAP obtained by co-precipitation of salts. The 5-nm oxo-TiO₂ particles were prepared in a sol-gel reactor with rapid reagents micromixing. The photocatalytic test of ethylene degradation, in a continuous-flow fixed-bed reactor, showed an increase of the photocatalytic yield for the composite photocatalysts with an addition of HAP. This result was interpreted by a synergy between adsorption and photo-oxidation.

PMMA-TiO2 Fibers for the Photocatalytic Degradation of Water Pollutants

Titanium dioxide (TiO2) is a promising photocatalyst that possesses a redox potential suitable for environmental remediation applications. A low photocatalytic yield and high cost have thus far limited the commercial adoption of TiO2-based fixed-bed reactors. One solution is to engineer the physical geometry or chemical composition of the substrate to overcome these limitations. In this work, porous polymethyl methacrylate (PMMA) substrates with immobilized TiO2 nanoparticles in fiber forms were fabricated and analyzed to demonstrate the influence of contaminant transport and light accessibility on the overall photocatalytic performance. The influences of (i) fiber porosity and (ii) fiber architecture on the overall photocatalytic performance were investigated. The porous structure was fabricated using wet phase inversion. The core-shell-structured fibers exhibited much higher mechanical properties than the porous fibers (7.52 GPa vs. non-testability) and maintained the same degradation rates as porous structures (0.059 vs. 0.053/min) in removing methylene blue with comparable specific surface areas. The highest methylene blue (MB) degradation rate (kMB) of 0.116 min-1 was observed due to increases of the exposed surface area, pointing to more efficient photocatalysis by optimizing core-shell dimensions. This research provides an easy-to-manufacture and cost-efficient method for producing PMMA/TiO2 core-shell fibers with a broad application in water treatment, air purification, and volatile sensors.

Light Absorption Properties and Electronic Band Structures of Lead-Vanadium Oxyhalide Apatites Pb5 (VO4 )3 X (X=F, Cl, Br, I)

The Pb-V oxyhalide apatite compounds Pb₅ (VO₄ )₃ X (X=F, Cl, Br, I) were successfully synthesized using a facile solution method and studied with respect to their structural/optical characteristics and electronic band structures. UV-visible diffuse reflectance spectroscopy, electrochemical analysis and first-principles calculations showed that the synthesized apatites behaved as n-type semiconductors, with absorption bands in the UV-visible region that could be assigned to electron transitions from the valence band to a conduction band formed by hybridized V 3d and Pb 6p orbitals. Among the apatites examined, Pb₅ (VO₄ )₃ I had the smallest band gap of 2.7 eV, due to an obvious contribution of I 5p orbitals to the valence band maximum. Based on its visible light absorption capability, Pb₅ (VO₄ )₃ I generated a continuous anodic photocurrent under visible light (λ>420 nm) in a solution of 0.1 m NaI in acetonitrile.

Environmentally responsive and anti-bugs textile finishes - Recent trends, challenges, and future perspectives

Bugs, such as microorganisms and insects, are present in the environment and sometimes can be health-hazardous if the living environment is not maintained following proper hygienic regulations. In the present scenario of increasing public awareness, environmental consciousness, and growing demand for easy-care, and disinfected textiles, the manufacturing of protective and easy-to-care textiles has become a key necessity of the modern world. Comfortable, clean, hygienic, antimicrobial, and insect repelling properties of textile goods are gaining the accelerating research momentum as a basic requirement to produce multifunctional textiles. These functional finishes have numerous applications such as in-home textiles, bed nets, and tenting, camping gear as well as in military uniforms. Synthetic antimicrobial and insect repellents are quite effective against insects and microscopic organisms but are slightly toxic to the human being and the environment. To overcome these problems, researchers are considering natural agents for functional finishes, but their effectiveness is less durable to textile material. Besides needful advantages, the excessive use of dyes in finishing processes heavily required washing cycles and ultimately release various types of hazardous dyes or wasteful effluents in the environment. This review reports the chemical composition and recent developments in textile finishes, particularly antimicrobial and insect repellent textile finishes. A large number of commonly used antimicrobial agents (i.e. chitosan, zwitterionic compounds, silver and silver-based compounds, titanium dioxide nanoparticles, imidazolium salts, triclosan and quaternary ammonium salts) and insect repellent textile finishes (i.e. N‑N‑diethyl‑m‑toluamide, permethrin, cypermethrin, pyrethrum, picaridin, bioallethrin, citriodiol and essential oils) have been presented. Finally, the review is wrapped up with major research gaps/challenges, concluding remarks, and future opportunities in this area of research.

Single-site and nano-confined photocatalysts designed in porous materials for environmental uses and solar fuels

Silica-based micro-, meso-, macro-porous materials offer attractive routes for designing single-site photocatalysts, supporting semiconducting nanoparticles, anchoring light-responsive metal complexes, and encapsulating metal nanoparticles to drive photochemical reactions by taking advantage of their large surface area, controllable pore channels, remarkable transparency to UV/vis and tailorable physicochemical surface characteristics. This review mainly focuses on the fascinating photocatalytic properties of silica-supported Ti catalysts from single-site catalysts to nanoparticles, their surface-chemistry engineering, such as the hydrophobic modification and synthesis of thin films, and the fabrication of nanocatalysts including morphology controlled plasmonic nanostructures with localized surface plasmon resonance. The hybridization of visible-light responsive metal complexes with porous materials for the construction of functional inorganic-organic supramolecular photocatalysts is also included. In addition, the latest progress in the application of MOFs as excellent hosts for designing photocatalytic systems is described.

Combined ultrasonic and gamma-irradiation to prepare TiO2@PET-g-PAAc fabric composite for self-cleaning application

The grafting of polyacrylic acid (PAAc) onto the fabric of Poly(ethyleneterephthalate) (PET) was loaded with TiO₂ by a mixture sonication of TiO₂ dispersed in AAc dissolved in acetone solvent. Ultrasonic irradiation was utilized as a tool for a good dispersion of TiO₂ onto the PET fabric. The grafted PET fabrics with acrylic acid AAc monomer were successfully obtained using gamma-ray induced graft polymerization, the degree of grafting PET-g-PAAc fiber was 105%. The chemical compositions and crystal structure of grafted TiO₂@PET-g-PAAc fabrics were characterized by ATR-FTIR and XRD. It was found that loading of PET fiber with in TiO₂ particles showing the formation of anatase and rutile as performed by XRD. The thermal property of TiO₂@PET-g-PAAc was investigated by differential thermal analysis (DTA). The obtained result indicated the thermal property of the grafted TiO₂@PET-g-PAAc was increased. Image of scanning electron microscope (SEM) indicated the good adherent and good distribution of PAAc and TiO₂ with PET fabric. The self-cleaning property of TiO₂@PET-g-PAAc has been evaluated by using three kinds of dyes as models.

Controlling Photocatalytic Activity and Size Selectivity of TiO2 Encapsulated in Hollow Silica Spheres by Tuning Silica Shell Structures Using Sacrificial Biomolecules

Yolk-shell nanostructured photocatalyst which consists of inner core photocatalytic particles and outer silica shell exhibits high photocatalytic efficiency and molecular size selectivity due to the molecular sieving property of the outer shell. Creation of extended porosity in the shell endows it with improved adsorption properties and size selectivity toward targeted reactants. In this study, yolk-shell nanostructured photocatalyst consisting of TiO₂ NPs core and porous silica shell with controllable pore size was fabricated through a facile single-step dual-templating approach utilizing oil-in-water (O/W) microemulsions and amphiphilic protein molecules. Addition of optimum amount of protein (ovalbumin) as a sacrificial template together with O/W microemulsion during the synthesis led to the expansion of average pore size from 2.0 to 3.6 nm, while retaining TiO₂-encapsulated yolk-shell nanostructures. Photocatalytic degradation tests using gaseous 2-propanol and huge proteins as model substrates clearly revealed that the obtained material (TiO₂@HSS_pro) showed superior photocatalytic performances with both improved photocatalytic efficiency and molecular size selectivity due to the increased surface area and expanded pore diameter.

Fabrication of Photocatalytic Paper Using TiO2 Nanoparticles Confined in Hollow Silica Capsules

TiO₂ nanoparticles (NPs) encapsulated in hollow silica spheres (TiO₂@HSSs) show a shielding-effect that can insulate photocatalytically active TiO₂ NPs from the surrounding environment and thus prohibit the self-degradation of organic support materials under ultraviolet (UV)-light irradiation. In this study, photocatalytically active papers were fabricated by combining TiO₂@HSS and cellulose fibers, and their photocatalytic activities and durability under UV-light irradiation were examined. The yolk-shell nanostructured TiO₂@HSS, which has an ample void space between inner TiO₂ NPs and an outer silica shell, was synthesized using a facile single-step method utilizing an oil-in-water microemulsion as an organic template. The thus-prepared TiO₂@HSS particles were deposited onto a cellulose paper either by the chemical adhesion process via ionic bonding or by the physical adhesion process using a dual polymer system. The obtained paper containing TiO₂@HSS particles with high air permeability exhibited a higher photocatalytic activity in the photocatalytic decomposition of volatile organic compounds than unsupported powdery TiO₂@HSS particles because of the uniform dispersion on the paper with a reticular fiber network. In addition, the paper was hardly damaged under UV-light irradiation, whereas the paper containing naked TiO₂ NPs showed a marked deterioration with a considerably decreased strength, owing to the ability of the silica shell to prevent direct contact between TiO₂ and organic fibers. This study can offer a promising method to fabricate photocatalytically active papers with a photoresistance property available for real air cleaning.

In vivo bactericidal efficacy of the Ti6Al4V surface after ultraviolet C treatment

Background

Biomaterial-associated infections are one of the most important complications in orthopedic surgery. The main goal of this study was to demonstrate the in vivo bactericidal effect of ultraviolet (UV) irradiation on Ti6Al4V surfaces.

Materials and methods

An experimental model of device-related infections was developed by direct inoculation of Staphylococcus aureus into the canal of both femurs of 34 rats. A UV-irradiated Ti6Al4V pin was press-fit into the canal by retrograde insertion in one femur and the control pin was inserted into the contralateral femur. To assess the efficacy of UV radiation, the mean colony counts after inoculation in the experimental subjects and the control group were compared at different times of sacrifice and at different inoculum doses.

Results

At 72 h, the mean colony counts after inoculation in experimental femurs were significantly lower than those of the control group, with a reduction percentage of 76 % (p = 0.041). A similar difference between control and experimental pins was observed at 24 h using an inoculum dose <10⁴ colony-forming units (CFU), for which the reduction percentage was 70.48 % (p = 0.017).

Conclusion

The irradiated surface of Ti6Al4V is able to reduce early bacterial colonization of Ti6AlV pins located in the medullar channel and in the surrounding femur. The reductions depend on the initial inoculums used to cause infection in the animals and the greatest effects are detected for inoculums <10⁴ CFU.

Level of evidence

Not applicable.

Designed synthesis of hydroxyapatite nanostructures: bullet-like single crystal and whiskered hollow ellipsoid

Hydroxyapatite (HAp) nanostructures of whiskered hollow ellipsoid and bullet-like single crystal were synthesized under mild reaction conditions by using a template-free "one pot" synthetic method. Immersing calcium carbonate precursor into ammonium phosphate solution resulted in the HAp phase. Formed HAp crystals were characterized by X-ray diffraction and transmission electron microscopy techniques. The stability and phase composition of calcium carbonate influenced the morphology and crystallinity of HAp. The transformation of the most stable calcite precursor yielded the bullet-like HAp single crystal of 300-600 nm in length, ~40 nm in tip diameter and ~80 to ~100 nm in bottom diameter. The metastable vaterite precursor showed the formation of the whiskered hollow ellipsoid nanostructures composed of HAp nanorods of ~10 nm in diameter. The driving force for the whole transformation process was the difference in solubility of calcium carbonate and HAp. At the same time, Kirkendall effect and Ostwald ripening played important roles in the formation of the different HAp nanostructures.

Electrochemical analysis of the UV treated bactericidal Ti6Al4V surfaces

This research investigates in detail the bactericidal effect exhibited by the surface of the biomaterial Ti6Al4V after being subjected to UV-C light. It has been recently hypothesized that small surface currents, occurring as a consequence of the electron-hole pair recombination taking place after the excitation process, are behind the bactericidal properties displayed by this UV-treated material. To corroborate this hypothesis we have used different electrochemical techniques, such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization plots and Mott-Schottky plots. EIS and Mott-Schottky plots have shown that UV-C treatment causes an initial increase on the surface electrical conduction of this material. In addition, EIS and polarization plots demonstrated that higher corrosion currents occur at the UV treated than at the non-irradiated samples. Despite this increase in the corrosion currents, EIS has also shown that such currents are not likely to affect the good stability of this material oxide film since the irradiated samples completely recovered the control values after being stored in dark conditions for a period not longer than 24h. These results agree with the already-published in vitro transitory behavior of the bactericidal effect, which was shown to be present at initial times after the biomaterial implantation, a crucial moment to avoid a large number of biomaterial associated infections.

Photodecomposition of humic acid and natural organic matter in swamp water using a TiO(2)-coated ceramic foam filter: potential for the formation of disinfection byproducts

This paper reports on the photodecomposition of aqueous humic acid (HA) by a TiO(2)-coated ceramic foam filter (TCF) reactor and on the potential for the formation of disinfection byproducts (DBPs) upon chlorination of the photocatalytically treated solutions. This photocatalytic reactor can also be applied to the removal of natural organic matter (NOM) in swamp waters. The proposed photocatalytic reaction system was operated as per standardized methodologies. First, the ability of the TCF to decompose HA (a representative compound of NOM) was evaluated from the changes in the total organic carbon (TOC) and UV(254) with the reaction time. Remarkably, TOC removal and UV(254) values ranging from 44% to 61% and from 60% to 83%, respectively, were achieved. The potential for the formation of DBPs (total trihalomethane and total haloacetic acid) by chlorination of the phototreated solution was strongly dependent on the TOC removal and UV(254) values in the solution. The degree of photodecomposition of NOMs in the swamp water samples and the DBP formation potential showed similar trends as in the case of the standard solutions containing HA. The method used in this study could be effectively used to evaluate the efficiency of TCF for reducing HA and NOM, while suppressing the formation of DBP products.

Fast Synthesis of Rutile/Apatite Core/Shell Structured Photocatalyst in Simulated Body Fluid

The core/shell structured rutile/apatite was prepared by soaking rutile TiO2 (R-TiO2) microspheres into a simulated body fluid (SBF) only for 1 day. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and N2 adsorption measurements. XRD showed that the apatite content increased with prolonging the soaking time or increasing the SBF concentration. TEM and EDX demonstrated that apatite had been coated on the surface of R-TiO2 microspheres successfully. HRTEM indicated that the lattice spacings of 0.27 nm and 0.32 nm were assigned to (211) plane of apatite and (101) plane of R-TiO2, respectively.

Synthesis of Ag-TiO2 composite nano thin film for antimicrobial application

TiO2 photocatalysts have been found to kill cancer cells, bacteria and viruses under mild UV illumination, which offers numerous potential applications. On the other hand, Ag has long been proved as a good antibacterial material as well. The advantage of Ag-TiO2 nanocomposite is to expand the nanomaterial's antibacterial function to a broader range of working conditions. In this study neat TiO2 and Ag-TiO2 composite nanofilms were successfully prepared on silicon wafer via the sol-gel method by the spin-coating technique. The as-prepared composite Ag-TiO2 and TiO2 films with different silver content were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) to determine the topologies, microstructures and chemical compositions, respectively. It was found that the silver nanoparticles were uniformly distributed and strongly attached to the mesoporous TiO2 matrix. The morphology of the composite film could be controlled by simply tuning the molar ratio of the silver nitrate aqueous solution. XPS results confirmed that the Ag was in the Ag(0) state. The antimicrobial effect of the synthesized nanofilms was carried out against gram-negative bacteria (Escherichia coli ATCC 29425) by using an 8 W UV lamp with a constant relative intensity of 0.6 mW cm(-2) and in the dark respectively. The synthesized Ag-TiO2 thin films showed enhanced bactericidal activities compared to the neat TiO2 nanofilm both in the dark and under UV illumination.

Photocatalytic Mechanism of Action of Apatite-Coated Ag/Agbr/Tio2 on Phenol and Escherichia Coli and Bacillus Subtilis Bacteria Under Various Conditions

Multi-component photocatalysts based on apatite-coated Ag/AgBr/TiO2 were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-stal ic. The median ism for deactivation of bacteria in the dark can be related to the linkage between the phosphate group of the composite and the outer membrane of the cell. The photocatalytic destruction of bacteria under visible I ight indicates that attachment of the catalysts to the outer wall of the cell causes them to destroy effectively the cell wall and inner membrane by various reactive species such as OH, O2 - and 1O2. Thus this effect increases the photoactivity more than two-fold. Oxidation of phenol was also achieved under visible light- and UVA- irradiation using apatite-coated Ag/AgBr/TiO2 powders. Under UVA illumination, the ‘OH produced from the hole of the TiO2 valence band is responsible for the photodegradation of phenol, while under visible light, AgBr acts as the photoactive component of the catalyst, that can not produce’ OH and oxidize the phenol.

Performing a microfiltration integrated with photocatalysis using an Ag-TiO(2)/HAP/Al(2)O(3) composite membrane for water treatment: Evaluating effectiveness for humic acid removal and anti-fouling properties

Membrane filtration has been increasingly used for water treatment and wastewater reclamation in recent years. To further improve the effectiveness of membrane process and reduce membrane fouling, a highly reactive photocatalytic membrane, Ag-TiO(2)/hydroxiapiate (HAP, Ca(10)(PO(4))(6)(OH)(2))/Al(2)O(3), was employed to realize microfiltration (MF) coupling photocatalysis for surface water treatment. The effectiveness on the potential of membrane was investigated by removing humic acid (HA) test under different feed total organic carbon (TOC), light intensity and transmembrane pressure (TMP). The HA removal and anti-fouling property of as-prepared membrane was improved under UV irradiation, likely due to photocatalytic degradation of foulants along with filtration simultaneously. Under given feed water composition, increasing the light intensity resulted in increased removal of HA from aqueous solution. However, a limiting TMP seems to exist beyond which the increased HA removal cannot be sustained. Fouling behavior analysis indicated that the transition in fouling mode from initial pore blocking to cake filtration occurred much slower as UV irradiated. Furthermore, a superior efficiency on removal of trace organic contaminants, as well as milder flux reduction, was presented from surface water treatment, which demonstrated that the integrated system with enhanced performance is foreseen as an emerging technique for water treatment.

Rapid growth of hydroxyapatite nanoparticles using ultrasonic irradiation

A rapid, environmental friendly and low-cost method to prepare hydroxyapatite nanoparticles is proposed. In this method, hydroxyapatite is produced in a sonicated pseudo-body solution. The sonication time was found effective in the formation of the crystalline phase of nanoparticles. In our experimental condition, 15 min sonication resulted in the most pure hydroxyapatite phase. Also it was shown that growth temperature is a crucial factor and hydroxyapatite crystallizes only at 37 degrees C. The particles formed by sonication were generally smaller and more spherical than those obtained without sonication. Sonication increased the hydroxyapatite crystal growth rate up to 5.5 times compared to non-sonication condition. The comparison between the specific surface area of hydroxyapatite nanoparticles obtained by sonication and without sonication demonstrated that sonication increased the specific surface area from 63 m(2)/g to 107 m(2)/g and decreased the size of nanoparticles from 30 nm to 18 nm. Analysis on the pore structure demonstrated that the fractal structures obtained with and without sonication were considerably different.

Bactericidal behaviour of Ti6Al4V surfaces after exposure to UV-C light

TiO(2)-coated biomaterials that have been excited with UV irradiation have demonstrated biocidal properties in environmental applications, including drinking water decontamination. However, this procedure has not been successfully applied towards the killing of pathogens on medical titanium-based implants, mainly because of practical concerns related to irradiating the inserted biomaterial in situ. Previous researchers assumed that the photocatalysis on the TiO(2) surface during UV application causes the bactericidal effects. However, we show that a residual post-irradiation bactericidal effect exists on the surface of Ti6Al4V, not related with photocatalysis. Using a combination of staining, serial dilutions, and a biofilm assay, we show a significant and time-dependent loss in viability of different bacterial strains of Staphylococcus epidermidis and Staphylococcus aureus on the post-irradiated surface. Although the duration of this antimicrobial effect depends on the strains selected, our experiments suggest that the effect lasts at least 60 min after surface irradiation. The origin of such phenomena is discussed in terms of the physical properties of the irradiated surfaces, which include the emission of energy and changes in surfaces charge occurring during electron-hole recombination processes. The method here proposed for the preparation of antimicrobial titanium surfaces could become especially useful in total implant surgery for which the antimicrobial challenge is mainly during or shortly after surgery.

Photocatalytic activity of titanium dioxide modified concrete materials - influence of utilizing recycled glass cullets as aggregates

Combining the use of photocatalysts with cementitious materials is an important development in the field of photocatalytic air pollution mitigation. This paper presents the results of a systematic study on assessing the effectiveness of pollutant degradation by concrete surface layers that incorporate a photocatalytic material - Titanium Dioxide. The photocatalytic activity of the concrete samples was determined by photocatalytic oxidation of nitric oxide (NO) in the laboratory. Recycled glass cullets, derived from crushed waste beverage bottles, were used to replace sand in preparing the concrete surface layers. Factors, which may affect the pollutant removal performance of the concrete layers including glass color, aggregate size and curing age, were investigated. The results show a significant enhancement of the photocatalytic activity due to the use of glass cullets as aggregates in the concrete layers. The samples fabricated with clear glass cullets exhibited threefold NO removal efficiency compared to the samples fabricated with river sand. The light transmittance property of glass was postulated to account for the efficiency improvement, which was confirmed by a separate simulation study. But the influence of the size of glass cullets was not evident. In addition, the photocatalytic activity of concrete surface layers decreased with curing age, showing a loss of 20% photocatalytic activity after 56-day curing.

Antibacterial effect of apatite-coated titanium dioxide for textiles applications

An antibacterial activity of apatite-coated titanium dioxide (TiO2) against four types of bacteria (Staphylococcus aureus, Escherichia coli, methicillin-resistant Staphylococcus aureus (MRSA), and Micrococcus luteus) was investigated. Its antibacterial performance was observed under black light, visible light, and dark conditions. The number of viable bacteria decreased with irradiation time and became most prominent at 24 hours. Distortion of bacterial cells by the nanoparticles was demonstrated by scanning electron microscopy. Apatite-coated TiO2 was fixed on cotton textiles by dip-coat technique, and the antimicrobial properties of corresponding fabrics were then investigated. The effect of irradiation source on antimicrobial activity of coated cotton fabrics was examined, wherein black-light irradiation demonstrated higher antibacterial activity than either visible-light irradiation or dark conditions. Microbial populations of coated cotton fabrics decreased with increasing irradiation intensity. Coated cotton fabrics have been shown to be nontoxic to human dermal fibroblasts. Our findings suggest that the presence of apatite-coated TiO2 shows antibacterial activity in the presence of black light or visible light, suggesting its potential use in reducing the risk of microorganism transmission for textile applications.