Anatase Crystalline Structure Research Articles

Tailoring molecularly imprinted polymer on titanium-multiwalled carbon nanotube functionalized gold electrode for enhanced chlorophyll determination in microalgae health assessment.

A unique method for determining chlorophyll content in microalgae isdevised employing a gold interdigitated electrode (G-IDE) with a 10-µm gap, augmented by a nano-molecularly imprinted polymer (nano-MIP) and a titanium dioxide/multiwalled carbon nanotube (TiO2/MWCNT) nanocomposite. The nano-MIP, produced using chlorophyll template voids, successfully trapped chlorophyll, while the TiO2/MWCNT nanocomposite, synthesized by the sol-gel technique, exhibited a consistent distribution and anatase crystalline structure. The rebinding of procured chlorophyll powder, which was used as a template for nano-MIP synthesis, was identified with a high determination coefficient (R2 = 0.9857). By combining the TiO2/MWCNT nanocomposite with nano-MIP, the G-IDE sensing method achieved a slightly betterR2 value of 0.9892 for detecting chlorophyll in microalgae. The presented G-IDE sensor showed a significant threefold enhancement in chlorophyll detection compared withcommercially available chlorophyll powder. It had a detection limit of 0.917mL(v/v) and a linear range that spanned from10-6to 1mL. The effectiveness of the sensor in detecting chlorophyll in microalgae was confirmed through validation of its repeatability and reusability.

Enhancement mechanism of copper ions doped TiO2 substrates based on surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) is considered as one of the most attractive analytical tools, and it is necessary to develop more semiconductor substrates. Herein, copper ions-doped TiO2 (Cu-TiO2) nanoparticles (NPs) with different doping ratios were synthesized by a sol-hydrothermal method and used as semiconductor SERS substrates to explore the possible enhancement mechanisms. The synthesized Cu-TiO2 NPs show a cubic crystalline structure of anatase with a small particle size at 8 nm. We discussed the SERS enhancement ability of Cu-TiO2 substrates using crystal violet (CV) used as a probe. It can be found that there is a charge transfer (CT) effect between CV molecules and Cu-TiO2 substrates. In addition, Cu-TiO2 substrates exhibit the most SERS enhancement with an enhancement factor (EF) up to 2.4 × 104 at the Cu2+ doping ratio of 3 %, with a detection limit of 5 × 10–7 M. The experiments demonstrated that Cu-TiO2 NPs can be used as SERS substrates because of the CT route among the valence band, the surface state energy level, and the lowest unoccupied molecular orbital, which facilitates the development of semiconductor SERS substrates and provides a new perspective in exploring SERS enhancement mechanisms.

Characterization and Self-Cleaning Properties of Silk Fabric Coated by Chitosan-Xyloglucan/nano-TiO<sub>2</sub> Composite Film

In this study, Chitosan-Xyloglucan encapsulated Titanium dioxide was prepared by in-situ method for coating Silk fabric. FT-IR XRD characterized the functional groups and formation of crystallization of composite film. SEM analysis showed the immobilization of composite film on the surface of silk fabric. The coated silk fabrics were stained with methylene blue, and the stain removal efficiency was evaluated. The results showed that the composite film was deposited onto the silk fabric. The functional groups showed peaks around 1635 to 1636 and 400 to 500 cm-1 that indicate the presence of C=N groups of Chitosan-Xyloglucan and Ti-O groups of TiO2 on the composite, respectively. The XRD results indicated that the TiO2 prepared by the sol-gel method was an anatase crystalline structure. The mechanical properties showed the composite film was superior to the Chitosan-Xyloglucan, TiO2, and uncoated silk fabric. Finally, the methylene blue degradation capability was investigated. The coated silk fabric has insignificantly removing methylene blue stain than the untreated silk fabric, but it is noticeably repellent to stain.

Analyzing PEO anodization time to monitor coatings phases, composition, morphology, thickness, and microhardness during the growth of TiO2 pores on the CP-Ti surface

The objective of this study was to develop an oxide coating on commercially pure titanium using the plasma electrolytic oxidation (PEO) technique. During the surface treatment process, the time value was varied for 1, 10, 15, 30, 45, and 60 min. The PEO treatment was carried out at a limited current of 2.5 A and a voltage of 300 V. The coatings exhibit the anatase and rutile crystalline structures of TiO2. The coating produced for longer treatment times has higher concentrations of rutile, resulting in surface hardening. The thickness and the roughness of the coatings increased with the increase in treatment time, but there was a reduction in the size of the pores per unit area.

Unraveling crystalline phases, morphology, hardness, and adhesion of PEO anodic coatings on Ti-15Nb alloy surface

This study aims to create a coating of oxide (with Ca, P, and Mg) on the Ti-15Nb alloy using the plasma electrolytic oxidation (PEO) technique. The voltage value was varied during the surface treatment process (200, 250, and 300 V). The PEO treatment was performed using a limited current of 2.5 A for 60 s. The films have the anatase and rutile crystalline structures of TiO2, where rutile increases the hardness of the coatings. All coatings are hydrophilic in contact with distilled water and have poor adhesion to the substrate.

Effect of carbon nanotube incorporation on the photocatalytic activity of TiO2 nanotubes

Arrays of titanium dioxide (TiO2) nanotubes were prepared on commercially pure titanium (Ti) foils by anodic oxidation in a 0.5 M hydrofluoric acid (HF)-based electrolyte with multiwalled carbon nanotubes (MWCNTs) up to 0.035 g/l. The samples were annealed at 450°C for 1 h after anodic oxidation to form a crystalline anatase structure. The effect of MWCNT addition on the morphology and photocatalytic activity of the nanostructures was characterized by scanning electron microscopy, Raman spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence spectroscopy and methylene blue degradation tests. The results showed that MWCNTs were successfully incorporated into the titanium dioxide nanotube structure and significantly affected its photocatalytic activity. The best photocatalytic performance was achieved with the use of 0.025 g/l MWCNTs in the electrolyte composition. However, when the MWCNT content in the electrolyte increased, the electron–hole recombination rate and photon absorption ability of the structure deteriorated, resulting in a decreased photocatalytic activity.

Enhancing Gas Sensing Performance of TiO2-ZnO nanostructures: Effect of ZnO Concentration

Gas sensors based on titanium dioxide (TiO2) and zinc oxide (ZnO) nanocomposites are considered energy-saving devices that are utilized to find dangerous or harmful gases in an environment. The performance of nitrogen dioxide (NO2) gas sensors have been improved by spin-coating a TiO2 and TiO2:ZnO nanocomposite with varying concentrations (90TiO2:10ZnO, 70TiO2:30ZnO, and 50TiO2:50ZnO). To correlate structural properties with gas-sensing behavior, structural and morphological characterization has been done using FESEM, XRD, and EDX. Without any ZnO-specific crystalline phase, TiO2 X-ray diffraction was found to be indexed in the anatase crystalline structure. The ZnO is synthesized in the wurtzite phase with (002) orientation and has a smooth surface, according to the morphologies and crystalline structure of the films, which also indicated the presence of ZnO components with various crystallite sizes and lattice strains. Responses to NO2 are increased by low ZnO content. Additionally, at the average operating temperature of 250 oC, TiO2:ZnO shows a good response.

Intensive study of coating multilayer TiO2 nanoparticles thin films used for optoelectronics devices

High-performance of TiO2 nanoparticles (NPs) thin films were synthesized using spin coating technique deposited on a glass substrate. The effect of the several layers of films which have formed is studied on the structure, morphology, surface, optical and electrical characteristics. From the analysis using X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), raman spectroscopy, ultraviolet–visible spectrophotometer and impedance spectroscopy the obtained results show that anatase crystalline is obtained after annealing at 400 °C from TiO2 (NPs) in powder form. The surface of samples is uniform and the rms roughness is dependent on the number of layers and varied within the range 25.40–43.81 nm. The optical bandgap energy is obtained in the 2.9–3.2 eV range of multilayer TiO2 (NPs) thin films. The electrical characteristic analyzed as a function of temperature and frequency demonstrated a semiconducting behavior, and showed a decreased of resistance with the increase of temperature. The obtained activation energy based on impedance analysis is about 0.7 eV. It is showed that TiO2 deposited on the SnO2 glass substrate has anatase crystalline structure and their optical bandgap energy is about 3.0 eV. Electrical analysis shows semiconductor behavior over the explored temperature range from 400 °C.

Copper-/Zinc-Doped TiO2 Nanopowders Synthesized by Microwave-Assisted Sol–Gel Method

Using the microwave-assisted sol-gel method, Zn- and Cu-doped TiO2 nanoparticles with an anatase crystalline structure were prepared. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent and ammonia water as a catalyst. Based on the TG/DTA results, the powders were thermally treated at 500 °C. XRD and XRF revealed the presence of a single-phase anatase and dopants in the thermally treated nanoparticles. The surface of the nanoparticles and the oxidation states of the elements were studied using XPS, which confirmed the presence of Ti, O, Zn, and Cu. The photocatalytic activity of the doped TiO2 nanopowders was tested for the degradation of methyl-orange (MO) dye. The results indicate that Cu doping increases the photoactivity of TiO2 in the visible-light range by narrowing the band-gap energy.

Enhanced photocatalytic activity of TiO2 nanostructures produced by anodic oxidation of pre-deformed Cp–Ti

ABSTRACT Arrays of TiO2 nanotubes were prepared on pre-deformed commercially pure titanium (Cp–Ti) foils by anodic oxidation in 1 vol.-% HF-based electrolyte. Prior to the anodic oxidation, the samples were deformed by uniaxial tension and cold rolling at room temperature in three different strain levels. Following the anodic oxidation, the samples were annealed at 450°C to obtain crystalline anatase structure. Effects of the deformation on the produced nano structures were investigated by characterisation studies and photocatalytic activity tests including methylene blue degradation test, photoluminescence, and UV–Vis diffuse reflectance spectra analyses. The results showed that the induced strain has a remarkable effect on the nanotube morphology. It also led to a decrease in the crystallite size in the uniaxial tensioned and cold rolled titanium foils. As a result of the morphological and structural changes, the photocatalytic activity of the samples increased with cold rolling strain, and uniaxial tension strains up to a critical level.

A Modified Sol-Gel Synthesis of Anatase {001}-TiO2/Au Hybrid Nanocomposites for Enhanced Photodegradation of Organic Contaminants.

A sol-gel synthesis technique was employed for the preparation of anatase phase {001}-TiO2/Au hybrid nanocomposites (NCs). The scalable, schematic, and cost-efficient method was successfully modified using HF and NH4OH capping agents. The photocatalytic activity of the as-synthesized {001}-TiO2/Au NCs were tested over 2-cycle degradation of methylene blue (MB) dye and pharmaceutical active compounds (PhACs) of ibuprofen and naproxen under direct sunlight illumination at 35 °C and 44,000 lx. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed for the characterization of the as-prepared sample. The characterization results from the TEM, XPS, and XRD studies established both the distribution of Au colloids on the surface of TiO2 material, and the presence of the highly crystalline structure of anatase {001}-TiO2/Au NCs. Photodegradation results from the visible light irradiation of MB indicate an enhanced photocatalytic performance of Au/TiO2 NCs over TiO2. The results from the photocatalytic activity test performed under direct sunlight exposure exhibited promising photodegradation efficiencies. In the first cycle, the sol-gel synthesized material exhibited relatively better efficiencies (91%) with the MB dye and ibuprofen, while the highest degradation efficiency for the second cycle was 79% for the MB dye. Pseudo first-order photodegradation rates from the first cycle were determined to be comparatively slower than those from the second degradation cycle.

Photocatalytic and Antibacterial Properties of Doped TiO2 Nanopowders Synthesized by Sol-Gel Method.

For environmental applications, nanosized TiO2-based materials are known as the most important photocatalyst and are intensively studied for their advantages such as their higher activity, lower price, and chemical and photoresist properties. Zn or Cu doped TiO2 nanoparticles with anatase crystalline structure were synthesized by sol−gel process. Titanium (IV) butoxide was used as a TiO2 precursor, with parental alcohol as a solvent, and a hydrolysing agent (ammonia-containing water) was added to obtain a solution with pH 10. The gels were characterized by TG/DTA analysis, SEM, and XPS. Based on TG/DTA results, the temperature of 500 °C was chosen for processing the powders in air. The structure of the samples thermally treated at 500 °C was analysed by XRD and the patterns show crystallization in a single phase of TiO2 (anatase). The surface of the samples and the oxidation states was investigated by XPS, confirming the presence of Ti, O, Zn and Cu. The antibacterial activity of the nanoparticle powder samples was verified using the gram−positive bacterium Staphylococcus aureus. The photocatalytic efficiency of the doped TiO2 nanopowders for degradation of methyl orange (MO) is here examined in order to evaluate the potential applications of these materials for environmental remediation.

Fabrication and characterisation of ZnO@TiO2 core/shell nanowires using a versatile kinetics-controlled coating growth method

This study aims to provide a strategy for fabricating a scalable and reproducible ZnO@TiO2 heterostructure with precisely engineered TiO2 layer thickness by employing a simple wet chemical method to fabricate Zinc oxide nanowires (ZnO NWs) with a titanium oxide (TiO2) shell. It is also directed at investigating the impact of the reaction parameters: temperature, time and ammonia concentration, on the heterostructure, as well as the influence of photonic annealing on both ZnO NWs and ZnO@TiO2 heterostructure. Transmission, scanning electron microscopy, X-ray mapping and X-ray diffraction confirmed the ZnO@TiO2 heterostructure morphology, its shell thickness and presence of its elements. They also indicated that one hour was sufficient to produce the TiO2 shell at room temperature. In addition, both the reaction time and temperature did not impact on the TiO2 shell thickness. However, changing ammonia content from 300 µl to 400 µl significantly increased the TiO2 shell thickness from ∼2.5 nm up to ∼90 nm. The 2.5 nm shell showed an anatase crystalline structure whilst the thicker shells were mostly amorphous. X-ray photoelectron spectroscopy confirmed that the oxidation state of Ti was consistent with TiO2. Photoluminescence measurements showed a large improvement in the optical properties of ZnO NWs after forming the TiO2 shell, increasing the intensity of the UV band relative to the visible band by a factor of 4.5. The photonic annealing process showed a greater improvement by a factor of 7.1 for the ZnO@TiO2 heterostructure and tenfold for bare ZnO nanowires.

Photocatalytic Activity of Nanocoatings Based on Mixed Oxide V-TiO2 Nanoparticles with Controlled Composition and Size

V-TiO2 photocatalyst with 0 ≤ V ≤ 20 mol% was prepared via the sol–gel method based on mixed oxide titanium–vanadium nanoparticles with size and composition control. The mixed oxide vanadium–titanium oxo-alkoxy nanonoparticles were generated in a chemical micromixing reactor, coated on glass beads via liquid colloid deposition method and underwent to an appropriate thermal treatment forming crystallized nanocoatings. X-ray diffraction, Raman, thermogravimetric and differential thermal analyses confirmed anatase crystalline structure at vanadium content ≤ 10 mol%, with the cell parameters identical to those of pure TiO2. At a higher vanadium content of ~20 mol%, the material segregation began and orthorhombic phase of V2O5 appeared. The crystallization onset temperature of V-TiO2 smoothly changed with an increase in vanadium content. The best photocatalytic performance towards methylene blue decomposition in aqueous solutions under UVA and visible light illuminations was observed in V-TiO2 nanocoatings with, respectively, 2 mol% and 10 mol% vanadium.

Evaluation of Titanium Tetrachloride (TiCl₄) as an Alternative Coagulant and Characterization of Recovered TiO₂.

Titanium tetrachloride (TiCl₄) as an alternative coagulant to remove organic matters and nutrients from the effluent of the secondary wastewater treatment was evaluated by comparison of removal efficiency of total phosphorous to Al- and Fe-based coagulants. Also, the surface characteristics, elemental contents, and crystallinity of the TiO₂ produced from wastewater sludge flocculated with TiCl₄ coagulant were investigated depending on the calcination temperatures. The more dosages of coagulants were injected, the greater concentrations of the cations (Al+3, Fe+3, Ti+4) and hydrogen ions (H+) resulted in the lower pH. Also, TiCl₄ formed larger and heavier flocs than other coagulants and resulted in greater T-P removal efficiencies with reduced amounts of dosage. The phase change of anatase and rutile crystalline structures of TiO₂ incinerated from wastewater sludges of TiCl₄ coagulant was observed at relatively high calcination temperatures due to the existence of mixtures of organic matters, nutrients, and various impurities in the wastewater sludges of TiCl₄ coagulant. Both C and P atoms were found to be mainly doped in/on TiO₂ and the C and P atom originated from residual carbon of the settled organic matters and phosphorus nutrients present in effluents from sewage treatment plant, respectively. Therefore, 600-800 °C is the optimal calcination temperatures for TiO₂ produced from TiCl₄ coagulant flocculated with effluents from sewage treatment plant.

X-ray diffraction and microstructural analysis of Cu–TiO2 layers deposited by cold spray

Scientific research shows that copper, under appropriate conditions, has the properties of an antibacterial substance and acts as a bactericidal and bacteriostatic material. Another material that has antibacterial properties is titanium dioxide (TiO2). Avoidance of a crystal structure allows the formation of coatings with nanometric TiO2 powders using the low-pressure cold spray method. The paper presents results of qualitative X-ray diffraction phase analysis and research using the methods of transmission electron microscopy of composite Cu–TiO2 coatings, with different proportions of the modifying phase TiO2. Studies have shown that the conditions accompanying application in a cold gas environment do not initiate conversion from the amorphous phase into the crystalline structure of anatase.

Amorphous ZnO modified anatase TiO2 thin films templated by tripropylamine and their electrical properties

In the present study we report on a low cost synthesis of amorphous ZnO modified anatase TiO2 (40 and 20 mol% ZnO) thin films deposited via sol-gel spin coating technique on glass substrate. The effects of the composition on the structural, morphological and surface chemistry properties were discussed and correlated with the electrical behavior. Thus, by X-ray diffraction and Raman spectroscopy only TiO2 indexed in the anatase crystalline structure was identified without any ZnO characteristic crystalline phase. The surface chemistry assessed by X-ray Photoelectron spectroscopy highlighted the presence of Ti4+ in TiO2 as well as the presence of Zn2+ coordinated in the amorphous ZnO proved by the Auger ZnLMM transition shifted toward lower binding energies. The films are continuous, homogeneous with grain size below 20 nm and exhibit an intergranular porosity, as it was displayed by Scanning Electron Microscopy.The sensor signal towards CO exposure is strongly related to the amount of the ZnO amorphous phase formation. Thus, we found that a higher content of the ZnO amorphous phase leads to a lower sensitivity. The electrical and sensing measurements were performed in the temperature range (room temperature 400 °C), over the range of CO concentrations (0-2000 ppm). The sensor containing 20 mol.% amorphous ZnO exhibits a good sensitivity at ~300 °C for a low CO concentration .

Experimental evidences and theoretical calculations on phenanthrene degradation in a solar-light-driven photocatalysis system using silica aerogel supported TiO2 nanoparticles: Insights into reactive sites and energy evolution

Quantitative identification on reactive sites of target organic molecule during photocatalysis can help to get deep insight into the pollutant degradation pathway and energy evolution process. In this study, a new class of silica aerogel supported TiO2 (TiO2/SiO2) photocatalysts were fabricated via a two-step approach, and applied for adsorption and photocatalytic degradation of phenanthrene. Anatase crystalline structure was formed upon calcination at 400 and 600 °C, while mixed crystal interphases of anatase and rutile were generated at 800 °C (anatase:rutile = 0.67:0.33). The higher calcination temperature resulted in better crystallinity of TiO2, higher photocatalytic activity, and reduced adsorption affinity toward phenanthrene. TiO2/SiO2-800 (TiO2/SiO2 calcined at 800 °C) showed minimal phenanthrene uptake (~5.2%) but the strongest photocatalytic activity, and it was able to completely degrade phenanthrene within 3 h. The SiO2 aerogel component in the composite enabled the pre-concentration of phenanthrene on the photoactive sites, while the nanoscale mixed-phases of anatase and rutile of TiO2/SiO2-800 act as an efficient transfer medium for photo-induced charge carriers. Moreover, the formed Ti–O–Si linkage in TiO2/SiO2-800 induced formation of Ti3+ under solar light irradiation, promoting photoexcited electron trap and separation of electron-hole pairs. Based on the degraded phenanthrene intermediates/products, theoretical calculations according to the density functional theory (DFT) reveal that the atoms of phenanthrene with high electrophilic Fukui index (f-) are the most reactive sites towards the radicals. Potential energy surface profile for phenanthrene degradation further reveals the intermediates energy evaluation via radicals attack.

An environmentally friendly titania–silica core–shell nanoparticles coating for protection of tiled facade of cultural-historical buildings

The purpose of the current research was to synthesize and characterize a hydrophobic ultraviolet (UV) absorbent coating for protection of tiled facade of cultural-historical buildings. Considering the environmental and conservational issues for such applications, using toxic materials is limited. A silicone-based nanocomposite coating was prepared in which organically modified silicates (ormosil) and titania–silica core–shell nanoparticles were used as matrix and reinforcing phase, respectively. Nanocomposite coatings were prepared by sol–gel method. Hydroxy-terminated polydimethylsiloxane (PDMS-OH) and tetraethoxysilane (TEOS) were used to form the ormosil matrix. Titania nanoparticles in anatase crystalline phase were used. To control their photocatalytic activity, silica–titania core–shell nanoparticles were prepared. Nanocomposite coatings were applied on microscope slides and historic tiles by dip-coating and simple brushing. The coatings were characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), water contact angle measurements and photocatalytic activity measurements. The results revealed that a transparent hydrophobic coating of prepared ormosils could obtain by adding a maximum amount of 20 wt% of PDMS-OH to the initial sols without addition of highly toxic solvents and catalysts. The FT-IR spectra of ormosil gels exhibited Si–O–Si bond corresponding to silica gels. It also showed that PDMS formed covalent bonds to silica networks. The XRD patterns showed that titania maintained its anatase crystalline structure after core–shell treatment. TEM images of core–shell treated nanoparticles illustrated the formation of continuous silica shell with less than 4 nm thickness around titania cores. Water contact angle measurements on tiles showed an increase in contact angle from 30° to 97° after coating. The results of UV–Vis spectrophotometry confirmed that the continuous silica layer acted as a barrier between photocatalytic titania and Methylene blue. Overall, the best composition for obtaining an environmentally friendly, transparent, hydrophobic, and UV absorbing nanocomposite coating could contain 20 wt% of PDMS-OH and about 0.025 wt% of silica–titania core–shell nanoparticles.

Reusability in visible light of titanate nanotubes for the removal of organic pollutants: role of calcination temperature

ABSTRACT Titanate nanotubes (NTs) were synthesised by the hydrothermal method and later calcined at temperatures between 100–500°C. The calcined NTs were characterised and evaluated in the physicochemical adsorption of the safranin dye and photocatalytic degradation of caffeine. The materials calcined at low temperatures displayed a tubular structure and the H2Ti3O7 crystalline phase, which was transformed into anatase nanoparticles at 400°C. The NTs treated at 100°C showed the highest adsorption capacity (94%). Safranin was adsorbed through an ion-exchange mechanism, following the Langmuir isotherm and a pseudo-second-order kinetic model. While NTs calcined at lower temperatures were better for adsorption, the photocatalytic degradation of caffeine increased in samples calcined at higher temperatures with a maximum removal of 72%. The photocatalytic behaviour of the NT samples confirmed that the crystalline anatase structure in conjunction with structural OH groups enhanced the photocatalytic activity. The addition of isopropanol as a scavenger confirmed the important role played by the •OH radicals in the photocatalytic process. NTs calcined at 300°C were efficient for both adsorption and photocatalytic processes. Due to its efficiency, this sample was reused after dye adsorption for the photocatalytic degradation of caffeine under visible light due to its enhanced absorbance in the visible region. This research work shows the potential of NTs for wastewater purification.