Layer Of TiO2 Nanoparticles Research Articles

A versatile superhydrophilic/air-superoleophobic glass fiber membrane: Fabrication and application in oil/water separation

Superwetting materials have received extensive interest owing to their potential for efficient oil/water separation. Herein, a superhydrophilic-superoleophobic glass fiber membrane was fabricated through a simple spraying coating method. The membrane was coated with a composite layer of methyltrimethoxysilane (MTMS), fluorosurfactant (FS-50) and TiO2 nanoparticles. Accordingly, both hydrophilic groups (i.e., -OH) and oleophobic groups (i.e., fluorinated groups) were distributed on the membrane, and its surface roughness was improved by TiO2. The contact angles of water and oil on the coated membrane were 0° and 156.8° in air, respectively. By virtue of its selective permeability, it demonstrated separation efficiencies larger than 99.2 % for oil/water mixtures, which remained 98.7 % after 40 separation cycles. Furthermore, its separation efficiencies for oil-in-water emulsions were over 98.3 %, which remained 98 % after 10 separation cycles. Owing to its strong superoleophobicity, it displayed prominent anti-oil-fouling performance both in air and underwater. Besides, presence of TiO2 endowed it with photocatalytic capability, enabling it to recover from organic dye pollution. Moreover, the coated membrane maintained superoleophobic after 10 sandpaper-abrading or squeezing cycles. It also exhibited excellent stability under acid/alkali/salt conditions. The study provided new insights for constructing superwetting materials and an effective strategy for oil/water separation.

An amperometric stability study of titanium dioxide nanoparticle layer on interdigitated electrode contact based on morphology, structure, and surface-induced response

This paper investigates the amperometric stability of a Titanium Dioxide (TiO2) nanoparticle layer on an interdigitated electrode (IDE) to develop stable electronic devices. The devices were tested with varying numbers of spin-coat layers and annealing temperatures to achieve a TiO2 nanoparticle layer with high crystallinity. Device fabrication involved coating a TiO2 solution onto a silicon dioxide (SiO2) wafer with an IDE photomask. The devices were characterized using a Field-emission Scanning Electron Microscope (FESEM) and X-ray Diffractometer (XRD) to verify the crystallinity of the TiO2. Current-voltage (I-V) curves and real-time current measurements were also conducted to analyze the electrical properties of the device. FESEM results indicate that increasing the number of spin-coat layers and annealing temperature enhances the clarity of the spherical shape of TiO2 nanoparticles and produces highly crystalline nanoparticles, as confirmed by XRD analysis. In terms of electrical analysis, the device exhibited a sharp increase in current, maintaining a range of 2.5 nA to 10 nA. This concludes that the TiO2 device is highly sensitive, with excellent repeatability and response time, making it suitable for practical applications.

Coaxial electrospinning synthesis free-standing Sn/TiO2 flexible carbon fibers with sheath/core structure for advanced flexible lithium/potassium-ion batteries

Flexible Sn/TiO2 carbon nanofiber (ST-NCF) composites were constructed by doping TiO2 into tin-based carbon nanofibers via coaxial electrospinning. Sn/TiO2 carbon nanofiber was directly used as an anode for Lithium-ion Batteries (LIBs) and Potassium-ion Batteries (PIBs), which show exceptional electrochemical performances. The layered sheath/core structure of the material lead to its good electrochemical properties, where the core Sn carbon nanofiber was encapsulated by the sheath layer of TiO2 nanoparticles. In addition to enhancing its electrical conductivity, the outer TiO2 and N-doped carbon fiber matrix also provide a buffer zone for volumetric strain during charging and discharging. The fiber core Sn and sheath TiO2 form a heterojunction interface on the two-dimensional tube surface, which increases the diffusion rate of ions and electrons. After 100 cycles, TiO2-NCF and ST-NCF-40%TBT (40% TBT indicates the percentage of TiO2 in shell solution to the total composition of shell spinning solution) show capacities of 386.6 mAh g−1 and 1336 mAh g-1, respectively, at 0.5A g-1. After 2000 cycles, ST-NCF-40%TBT in LIBs displayed a high capacity of 299 mAh g-1 at 10 A g-1. After 350 cycles at 1A g-1, the capacity of ST-NCF-40%TBT in PIBs is reserved at 307 mA h g-1. Due to the superior mechanical flexibility of ST-NCF-40%TBT films, it will be a promising anode candidate for flexible LIBs and PIBs.

Black titania coated glass fiber as a photo absorber in interfacial solar steam generation under harsh condition

Interfacial solar steam generation (ISSG) is one of the promising solutions in the field of water filtration, desalination, and solvent recovery. For the industrial applications of the technology, there is a need for developing highly durable, thermally stable, and inert light absorbers. Therefore, this work addresses this issue by synthesizing black Titania (B–TiO2) via vacuum annealing and depositing it on glass fiber (GF) via vacuum filtration with an ethyl cellulose binder. According to the characterization techniques analyses, the change of colour is attributed to the occurrence of oxygen vacancies in the surface layers of TiO2 nanoparticles during vacuum annealing. The deposition parameters were optimized for achieving a maximum solar-weighted light absorptance of 95.7%. The optimized B–TiO2 GF was applied for the steam generation experiments and achieved the evaporation rate of 1.53 kg m−2 h−1, which corresponds to solar-steam conversion efficiency of 97.7 % under standard measurements condition of AM 1.5 G sun and ambient temperature and relative humidity of 20 °C and 40% respectively. Thanks to the high durability and chemical inertness of B–TiO2 GF it was applied for water filtration in extreme conditions of acidic/alkaline water and high-sun illumination (up to 35-sun). Worth noting that for high-sun experimentation there is a need to use a binder to improve particle attachment to the glass fibers.

Study of dual Z-scheme photocatalytic response of TiO2/Ag/ZnO coating on plasma-modified cotton fabric for self-cleaning application

An innovative approach was adopted to improve the photocatalytic response of nanoparticle-coated cotton fabric for self-cleaning application. Fabrics with layers of TiO2, Ag, and ZnO nanoparticles were assessed for photodegradation of Rhodamine B, methyl orange, and methyl red. A dual-scheme charge transfer method was designed for the photocatalytic activity of TiO2/Ag/ZnO nanoparticles on cotton fabric. To produce the multilayer structure of nanoparticles, the fabric was first functionalized with atmospheric pressure nonthermal plasma and then sonochemically coated with TiO2/Ag/ZnO in a layered form. The plasma functionalization enhanced the stability of TiO2/Ag/ZnO nanoparticles on the fabric. It was revealed that a combination of Ag, TiO2, and ZnO nanoparticles produced a Schottky barrier among the silver metal and metal oxides (TiO2 and ZnO), resulting in enhanced photocatalytic properties. Methyl red underwent the highest photocatalytic degradation of 93% over the designed photocatalyst-coated fabric after 120 min of light exposure. This study provides a promising strategy for improving the photocatalytic self-cleaning efficacy of nanocoated fabrics.

Efficiency enhancement and chrono-photoelectron generation in dye-sensitized solar cells based on spin-coated TiO2 nanoparticle multilayer photoanodes and a ternary iodide gel polymer electrolyte

The effect of the thickness of a multilayer TiO2 photoanode on the performance of a dye-sensitized solar cell (DSC) made with a polyethylene oxide-based gel polymer electrolyte containing ternary iodides and performance enhancer 4-tert-butylpyridine is studied. Multilayer photoanodes consisting of up to seven layers of TiO2 nano-particles (13 nm and 21 nm) are prepared by spin coating of successive layers. XRD results confirm the predominant presence of the anatase phase of TiO2 in the multilayer structure after sintering. The SEM images reveal the formation of a single TiO2 film upon sintering due to merging of individually deposited layers. The photocurrent density (JSC) and the efficiency increase with the number of TiO2 layers exhibiting the maximum efficiency and JSC of 5.5% and 12.5 mA cm−2, respectively, for the 5-layered electrode of total thickness 4.0 µm with a 9.66 × 10–8 mol cm−2 surface dye concentration. The present study introduces a method of determining the rate of effective photoelectron generation and the average time gap between two successive photon absorptions where the respective results are 1.34 molecule−1 s−1 and 0.74 s for the most efficient cell studied in this work.

Adsorption of yttrium by the sodium-modified titanium dioxide: Kinetic, equilibrium studies and investigation of Na-TiO2 radiation resistance

The adsorption of yttrium cations from an aqueous solution of YCl3 by sodium-modified titanium dioxide (Na-TiO2) was investigated. The Na-TiO2 was obtained by impregnating Na+ cations into the surface layer of TiO2 nanoparticles. The synthesis of nanoparticle TiO2 was performed by a liquid-phase sol–gel method, using the aqua complex of [Ti(OH2)6]3+‧3Cl− as a precursor. Nanoheterostructured Na-TiO2 is an anatase modification of TiO2. The amount of incorporated sodium cations on the TiO2 surface is about 6%. The surface area of Na-TiO2 is 239 m2‧g−1; the volume of mesopores is 0.098 cm3‧g−1; that of micropores is 0.054 cm3‧g−1. Yttrium ion adsorption was investigated under batch conditions. Complexometric titration and mas-spectrometric analysis determined the initial and equilibrium concentration of yttrium. The radiation resistance of Na-TiO2 to the influence of beta irradiation was investigated as well. For this purpose, the radiation of β−-particles of the 90Sr-90Y source “Sirius” was used. The flux of β− – particles was 2.1 ‧ 108 electrons/sm2‧s; the maximal energy of incident electrons was 2.28 MeV. It was shown that the investigated adsorbent has a high adsorption capacity toward yttrium cations. The maximum adsorption is about 259 mg/g. The adsorption kinetic is fit well with the kinetic model based on the pseudo-second-order equation. The equilibrium adsorption of yttrium cations is described by Freundlich's theory with high reliability. The adsorbent is resistant to the influence of β− – irradiation. This is manifested in the invariance of its adsorption capacity toward yttrium cations after irradiation. Na-TiO2 is a promising material for the adsorption of yttrium and Rare Earth elements and can be used as the basis for the 90Y isotopic generator.

Performance Improvement of Dye-Sensitized Solar Cells with Pressed TiO2 Nanoparticles Layer

A simple and low-cost fabrication method of dye-sensitized solar cells (DSSCs) was developed to improve the structure and performance of the photoanode with the pressed layer and compact TiO2 thin film using spin coating, screen printing, and mechanical compression. In this study, four different TiO2 layers were adopted to fabricate photoanodes: a mesoporous TiO2 nanoparticles (NPs) layer, a pressed TiO2 NPs layer, a mesoporous TiO2 NPs layer on the TiO2 compact thin film, and a pressed TiO2 NPs layer on the TiO2 compact thin film. The compact thin film was deposited on the fluorine-doped tin oxide (FTO) glass via spin coating, while the mesoporous TiO2 NPs layer was deposited via the screen-printing method. The pressed TiO2 NPs layer was produced by compressing the mesoporous TiO2 NPs layer with a hydraulic press machine. When using the pressed TiO2 NPs layer for the photoanode of DSSC, the power conversion efficiency of DSSC was enhanced the most. The electron lifetime for DSSC with photoanodes based on the pressed TiO2 NPs and mesoporous TiO2 NPs layers were 8.217 and 6.287 ms, respectively. The power conversion efficiency of DSSC with photoanodes based on the pressed TiO2 NPs layer was 5.4%, while that based on the mesoporous TiO2 NPs layer was 4.08%. DSSC with photoanodes based on the pressed TiO2 NPs layer showed a significant increase in the power conversion efficiency by 36.16% compared to that based on the mesoporous TiO2 NPs layer.

Stable Quantum Dot Light-Emitting Diodes Employing TiO2 Nanoparticles as a Mixed Emission Layer

Colloidal quantum dots (QDs) have attractive optical and electrical characteristics for various applications in the display industry. They have superb properties including color tunability, which is achieved by controlling the particle size and solution processes used for quantum dot light-emitting diodes (QLEDs). Here we demonstrate high efficiency QLEDs that consist of a mixed layer of TiO2 nanoparticles (NPs) and QDs. ZnO is the key material responsible for the promising results of the electroluminescence devices, which exhibited well-matched energy levels and robustness. In this report, Li-doped TiO2 NPs were synthesized under ambient conditions as an alternative electron transport layer (ETL) for QLEDs. A stable mixture of TiO2 NPs and QDs was prepared in chlorobenzene and then applied to QLEDs without a conventional ETL. QLEDs with such a simplified structure produce a maximum luminance of 123,311 cd/m<sup>2</sup> with a current efficiency of 40.5 cd/A. These results are comparable to those of conventional QLEDs. Additionally, the predicted T50 at 100 cd/m<sup>2</sup> was 1,420 h, based on the T50 at 1,600 cd/m<sup>2</sup>. These clearly indicate not only the promising results of the TiO2 NPs as an inorganic ETL, but also the remarkable performance of the simplified device with less layers. The reduction in fabrication steps using this solution-based process is also advantageous for next-generation display technology.

Low-Temperature Processed Brookite Interfacial Modification for Perovskite Solar Cells with Improved Performance.

The scaffold layer plays an important role in transporting electrons and preventing carrier recombination in mesoporous perovskite solar cells (PSCs), so the engineering of the interface between the scaffold layer and the light absorption layer has attracted widespread concern. In this work, vertically grown TiO2 nanorods (NRs) as scaffold layers are fabricated and further treated with TiCl4 aqueous solution. It can be found that a thin brookite TiO2 nanoparticle (NP) layer is formed by the chemical bath deposition (CBD) method on the surface of every rutile NR with a low annealing temperature (150 °C), which is beneficial for the infiltration and growth of perovskite. The PSC based on the TiO2 NR/brookite NP structure shows the best power conversion of 15.2%, which is 56.37% higher than that of the PSC based on bare NRs (9.72%). This complex structure presents an improved pore filling fraction and better carrier transport capability with less trap-assisted carrier recombination. In addition, low-annealing-temperature-formed brookite NPs possess a more suitable edge potential for electrons to transport from the perovskite layer to the electron collection layer when compared with high-annealing-temperature-formed anatase NPs. The brookite phase TiO2 fabricated at a low temperature presents great potential for flexible PSCs.

Stable construction of superhydrophobic surface on polypropylene membrane via atomic layer deposition for high salt solution desalination

A facile and effective strategy, integrating atomic layer deposition (ALD) with photo-deposition, is developed to fabricate uniform a superhydrophobic surface on the membrane for high salt solution desalination. More specifically, a titanium interlayer was prepared by accurately controlled ALD on polypropylene (PP) microporous membrane, then a superhydrophobic modification was constructed on titanium interlayer by covalent silica deposition with nano silane emulsion (NMES). The ALD can uniformly coat an ultrathin TiO2 nanoparticle layer on the PP membrane surface by chemical adsorption, and photo-deposition assembles a stable composite layer reacting with TiO2 nanoparticles. It shows that the contact angle of the PP/TiO2-NMES composite membrane is higher than 150°, which exhibited an excellent anti-wetting capacity in high salt (15 wt%) vacuum membrane distillation. Moreover, the chemically stable bonding between the superhydrophobic layer and the PP membrane made the composite membrane to demonstrate its stability in long-term scaling experiments. Our work provides a viable bottom-up synthesis scheme to tailer and optimizes the inorganic layer on the inert polymeric surface.

Manufacturing a TiO2-Based Semiconductor Film with Nanofluid Pool Boiling and Sintering Processes toward Solar-Cell Applications.

For the first time, nanofluid boiling was applied as a process for the creation of a semiconductor TiO2 nanoparticle film that can be deposited onto a conductive substrate (F-doped SnO2 glass: FTO). A steel-base device designed for pool boiling was used to deposit a TiO2-based nanofluid consisting of nanoparticles with an average size of about 20 nm. The boiling of the nanofluid directly on the FTO glass substrate allowed for the deposition of the nanoparticles onto the FTO surface. In principle, the surface responsible for transferring heat to the fluid can be covered with these nanoparticles when the nanofluid boils. Using the as-deposited films, crystal growth of the TiO2 nanoparticle was controlled by varying the strategies of the post-sintering profile. The maximum temperatures, periods, and ramping rates for the obtained samples were systematically changed. Scanning electron microscopy (SEM) revealed that a densely packed TiO2-nanoparticle layer was obtained for the as-deposited substrate via pool boiling. For the maximum temperature at 550 °C, the TiO2 grain sizes became larger (~50 nm) and more round-shaped TiO2 nanostructures were identified. Notably, we have demonstrated for the first time how the sintering of TiO2 nanoparticles proceeds for the nanoporous TiO2 films using high-resolution transmission electron microscopy (TEM) measurements. We found that the TiO2 nanoparticles fused with each other and crystal growth occurred through neighboring 2–4 nanoparticles for the 550 °C sample, which was proved by the TEM analysis that continuous lattice fringes corresponding to the (101) anatase phase were clearly observed through the entire area of some nanoparticles aligned horizontally. In addition, the loss of the TiO2 nanofluid (precursor solution) was completely avoided in our TiO2 deposition. Unlike the commonly used spin-coating method, nanofluid pool boiling would provide an alternative cost-effective approach to manufacture semiconductor layers for various applications, such as solar cells.

Enhanced visible photocatalytic performance of un-doped TiO2 nanoparticles thin films through modifying the substrate surface roughness

Titanium oxide (TiO2) has been widely utilized for application in environmental pollution due to its unique properties. However, large bandgap (3.2 eV) and low surface area of bulk TiO2 are the main properties that limit its photocatalytic applications. In this work, a thin layer of TiO2 (<200 nm) nanoparticles (NPs) on mechanically roughened glass substrates is deposited by a simple sol-gel method followed by a dip-coating process along with fast heating and sintering. The effect of substrate surface roughness on the morphology, hydrophilicity, and optical properties which results in a more electron-hole generation and consequently improved photocatalytic activity was investigated by different characterization techniques. The TiO2 layer on the roughest substrate (RMS = 76.90 nm) showed the smallest average NP size (3 nm) with the highest surface roughness (RMS = 121.00 nm) and hydrophilicity (74.5%) as well as strong optical absorption. This sample photodegraded the pollutant with an efficiency of 85% at a rate of 0.0054 min−1 under the illumination of the vis-light emitting diode (LED)-based source (440 and 590 nm). Therefore, an enhanced photocatalytic activity accompanied by recyclability was achieved by modifying the substrate surface roughness and thermal treatment in the process of synthesis. Conclusively, intrinsic defects and grain boundaries appear which behave as active areas for charge transfer in the photocatalytic process under visible irradiation. This research may provide an insight into the fabrication of highly efficient photocatalysts based on commonly used wide band gap materials to work in the absence of UV light.

A Simple and Ligand‐Free Synthesis of Light and Durable Metal‐TiO2 Polymer Films with Enhanced Photocatalytic Properties

AbstractThe photocatalytic efficiency of TiO2 can be increased by using co‐catalysts, such as metal nanoparticles, which act as electron sinks to suppress the recombination of photogenerated electron–hole pairs. The main challenge in preparing such systems is to create intimate contact between the metal and the TiO2 surface while still maintaining control over the morphology and distribution of the metal nanoparticles in the TiO2 matrix. Here lightweight TiO2 films are prepared by assembling a layer of TiO2 nanoparticles onto a thin polymer support, followed by physical vapor deposition of metal nanoparticles onto the TiO2 surface. Importantly the fabrication does not involve any chemical modifications to the surface of NPs, which allows spontaneous formation of strong chemical bonds between deposited metal and TiO2. Systematic optimization of this process gives materials 6× more catalytically active than the parent TiO2 films and up to 18× more catalytically active than commercial photoactive TiO2 glass. Moreover, the transparent, flexible, and robust polymer support enables the product films to be easily used for repeated photocatalytic reactions. Since the whole fabrication process is scalable and highly reproducible, this approach provides new opportunities for controlled synthesis of a new family of practical high‐performance metal‐ semiconductor hybrid photocatalysts.

Dielectric barrier discharge jet processed TiO2 nanoparticle layer for flexible perovskite solar cells

For attaining good-performance perovskite solar cells (PSCs), the carrier collection from the perovskite material to the transport layer plays a prominent role; herein, we demonstrate an atmospheric pressure plasma treatment technique to enhance the interface properties between the active perovskite layer and electron transport layer (ETL). A scan-mode low-temperature helium dielectric barrier discharge (DBD) jet is applied to process the TiO2 nanoparticle layers for the flexible n-i-p PSCs made on ITO-coated polyethylene naphthalate substrates. When the surface of TiO2 nanoparticle ETL is treated by the DBD jet at a scan rate of 2 cm s−1 and scan height of 5 cm by ten times, the photoelectrical conversion efficiency of the cell is enhanced from 12.30% to 13.66%. The performance improvement can be attributed to the increase of hydrophilic O–C = O functional groups on the surface of the TiO2 nanoparticle layer and the reduction of charge transfer resistance of the cell revealed by x-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, respectively. The results show that the low-temperature DBD jet treatment is a promising technique for processing flexible photovoltaic devices.

Interdigitated Electrode Biosensor Based on Plasma-Deposited TiO2 Nanoparticles for Detecting DNA.

Bioelectrodes mediated by metal oxide nanoparticles have facilitated the development of new sensors in medical diagnosis. High-purity TiO2 nanoparticles (NPs) were synthesized through thermal plasma and deposited directly on an interdigitated electrode. The surface of the TiO2-deposited electrode was activated with (3-aminopropyl) triethoxysilane (APTES) followed by fixing the single-stranded probe deoxyribonucleic acid (DNA) to fabricate the DNA biosensor. The structural properties of the deposited TiO2 nanoparticles were analyzed using a transmission electron microscope (TEM), X-ray diffraction (XRD), and a dynamic light scattering (DLS) system. The chemical composition and structural properties of the TiO2 nanoparticle layer and the fixed layer were analyzed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). E. coli O157:H7, a well-known pernicious pathogenic bacterial species, was detected as a target DNA of the prepared DNA biosensor, and the characteristics of DNA detection were determined by the current change using a picoammeter. The degree of binding between the probe DNA and the target DNA was converted into an electrical signal using the picoammeter method to quantitatively analyze the concentration of the target DNA. With the specificity experiment, it was confirmed that the biosensor was able to discriminate between nucleotides with mismatched, non-complementary, or complementary sequences.

Non-Enzymatic Glucose Biosensor Based on Highly Pure TiO2 Nanoparticles.

This study proposes a non-enzymatic glucose sensor fabricated by synthesizing high-purity TiO2 nanoparticles in thermal plasma and depositing it directly on a substrate and then depositing chitosan–polypyrrole (CS-PPy) conductive polymer films by electrochemical method. The structural properties of the deposited TiO2 nanoparticles were analyzed by X-ray diffraction (XRD) and dynamic light scattering (DLS) system. The chemical composition and structural properties of the TiO2 nanoparticle layer and the conductive polymer films were confirmed by X-ray photoelectron spectroscopy (XPS) spectra and scanning electron microscope (SEM). The glucose detection characteristics of the fabricated biosensor were determined by cyclic voltammetry (CV). CS-PPy/TiO2 biosensor showed high sensitivity of 302.0 µA mM−1 cm−2 (R2 = 0.9957) and low detection limit of 6.7 μM. The easily manufactured CS-PPy/TiO2 biosensor showed excellent selectivity and reactivity.

WO3 passivation layer-coated nanostructured TiO2: An efficient defect engineered photoelectrode for dye sensitized solar cell

Major loss factors for photo-generated electrons due to the presence of surface defects in titanium dioxide (TiO2) were controlled by RF-sputtered tungsten trioxide (WO3) passivation. X-ray photoelectron spectroscopy assured the coating of WO3 on the TiO2 nanoparticle layer by showing Ti 2p, W 4f and O 1s characteristic peaks and were further confirmed by X-ray diffraction studies. The coating of WO3 on the TiO2 nanoparticle layer did not affect dye adsorption significantly. Dye sensitized solar cells (DSSCs) fabricated using WO3-coated TiO2 showed an enhancement of ~10% compared to DSSCs fabricated using pristine TiO2-based photo-electrodes. It is attributed to the WO3 passivation on TiO2 that creates an energy barrier which favored photo-electron injection by tunneling but blocked reverse electron recombination pathways towards holes available in highest occupied molecular orbital of the dye molecules. It was further evidenced that there is an optimum thickness (duration of coating) of WO3 to improve the DSSC performance and longer duration of WO3 suppressed photo-electron injection from dye to TiO2 as inferred from the detrimental effect in short circuit current density values. RF-sputtering yields pinhole-free, highly uniform and conformal coating of WO3 onto any area of interest, which can be considered for an effective surface passivation for nanostructured photovoltaic devices.

Photocatalytic mechanism and performance of a novel wool flake–BiFeO3 nanosheet–TiO2 core–shell-structured composite photocatalyst

In this study, BiFeO3 (BFO) nanosheets ground from BFO particles were first incorporated with wool flakes to construct sandwich-like wool–BFO composites using the vibration-assisted ball milling technique in freezing conditions. The wool–BFO composites were then loaded with a thick layer of TiO2 nanoparticles to prepare the core–shell-structured wool–BFO–TiO2 composites using a hydrothermal synthesis process. The microstructure of the core–shell wool–BFO–TiO2 composites and its photocatalytic applications were systematically examined using a series of characterization methods. Trapping experiments and electron spin resonance spectra were also employed to judge the active radical species like superoxide radicals (·O2 −), singlet oxygen (1O2), holes (h+), and hydroxyl radicals (·OH) using benzoquinone, furfuryl alcohol, ethylenediamine tetraacetic acid, and tert-butanol as the scavengers, respectively. The photodegradation performance of the wool–BFO–TiO2 composites was measured using more resistant methyl orange (MO) dye as the pollutant model. In comparison with the wool–TiO2 or wool–BFO composites, the superior photocatalytic properties of the wool–BFO–TiO2 composites under visible light irradiation were attributed to the presence of mesopores and macropores, the large specific surface area and intimate interface between wool–BFO composites and TiO2 nanoparticles, the coexistence of Fe3+, Fe2+, Bi3+, Bi(3–x)+, Ti4+, and Ti3+species, and the strong visible light harvesting, thus leading to the fast separation of photogenerated electron–hole pairs. The wool–BFO–TiO2 composites could be used for the repeated photodegradation of organic pollutants and be recycled easily using a magnet. The active radical species of the wool–BFO–TiO2 composites were ·O2 − and 1O2 rather than ·OH and h+, which were involved in the photodegradation of MO dye under visible light irradiation.

Tailoring the Effects of Titanium Dioxide (TiO2) and Polyvinyl Alcohol (PVA) in the Separation and Antifouling Performance of Thin-Film Composite Polyvinylidene Fluoride (PVDF) Membrane.

In this study, thin-film composite (TFC) polyvinylidene fluoride (PVDF) membranes were synthesized by coating with titanium dioxide (TiO2)/polyvinyl alcohol (PVA) solution by a dip coating method and cross-linked with glutaraldehyde. Glutaraldehyde (GA) acted as a cross-linking agent to improve the thermal and chemical stability of the thin film coating. The incorporation of TiO2 in the film enhanced the hydrophilicity of the membrane and the rejection of dyes during filtration. The layer of TiO2 nanoparticles on the PVDF membranes have mitigated the fouling effects compared to the plain PVDF membrane. The photocatalytic performance was studied at different TiO2 loading for the photodegradation of dyes (reactive blue (RB) and methyl orange (MO)). The results indicated that the thin film coating of TiO2/PVA enhanced photocatalytic performance and showed good reusability under UV irradiation. This study showed that nearly 78% MO and 47% RB were removed using the TFC membrane. This work provides a new vision in the fabrication of TFC polymeric membranes as an efficient wastewater treatment tool.