Sol–gel preparation and photocatalysis of titanium dioxide

Novel Sol-Gel Synthesis of TiO2 Spherical Porous Nanoparticles Assemblies with Photocatalytic Activity

For this study, the synthesis of TiO₂ nanomaterials was performed via a novel sol-gel method employing titanium butoxide as a metal precursor, Pluronic F127 as a templating agent, toluene as a swelling agent, and acidic water or ethanol as the reaction solvents. The method was designed by tailoring certain reaction parameters, such as the sequence of toluene addition, magnetic stirring, the type of reaction solvent, and the calcination conditions. Analysis of the specific surface area and porosity was carried out via N₂ physisorption, whereas the morphological features of the solids were investigated via transmission electron microscopy. The crystalline structure of both the dried powders and the calcined materials was evaluated using X-ray diffraction analysis. It transpired that the different phase compositions of the solids are related to the specific synthesis medium employed. Under the adopted reaction conditions, ethanol, which was used as a reaction solvent, promoted the local arrangement of dispersed anatase particles, the specific arrangement of which does not lead to rutile transformation. Conversely, the use of water alone supported high-particle packing, evolving into a rutile phase. The photodegradation of Rhodamine B was used as a target reaction for testing the photocatalytic activity of the selected samples.

Water-Based Photocatalytic Sol–Gel TiO2 Coatings: Synthesis and Durability

The environmental impact of industrial technologies and related remediation methods are major research trend lines. Unfortunately, in the development of materials for wastewater treatment or air purification, hazardous reactants are often employed, reducing the overall beneficial contribution of such technology on the environment. We here synthesize stable titanium dioxide (TiO2) sols using a green route, with titanium tetraisopropoxide (TTIP) as precursor, water as solvent and acetic acid acting as catalyst, chelating agent and peptizing agent. The sol was deposited on glass by dip-coating and then analyzed using XRD, SEM and spectrophotometry. Wastewater purification ability was evaluated in the photocatalytic degradation of two organic dyes (Rhodamine B and Methylene Blue). Results on RhB showed > 85% degradation in 6 h maintained along a series of 7 tests, confirming good efficiency and reusability, and 100% in 3 h on MB; efficiency mostly depended on calcination temperature and layer thickness. High photodegradation efficiency was found in nonannealed samples, suggesting TiO2 nanoparticles crystallization during sol–gel production. Yet, such samples showed a gradual decrease in photoactivity in repeated tests, probably due to a partial release of TiO2 particles in solution, while on calcined samples a good adhesion was obtained, leading to a more durable photoactive layer.

Mesoporous Ti4O7 Spheres with Enhanced Zinc-Anchoring Effect for High-Performance Zinc-Nickel Batteries

Zinc-nickel batteries are promising competitors for next-generation power supply due to their benefits of high safety, high working voltage, and attractive rate performance. However, their practical applications are plagued by their poor cycling performance, stemming from uneven redistribution of zinc during cycling that results in dendrite formation and shape changes of the electrode. In this work, mesoporous Ti₄O₇ microspheres are prepared and are employed as additives of a zinc anode. Notably, the presence of mesopores provides abundant chemisorption sites for Zn(OH)₄^2- ions, inhibiting severe zinc redistribution in the electrode. Moreover, due to the good electrical conductivity and mesopores that serve as ion diffusion channels, the reaction reactivity and reversibility of the zinc electrode are greatly facilitated. As a result, the fabricated zinc-nickel battery with mesoporous Ti₄O₇ additives (ms-Ti₄O₇) exhibits an enhanced discharge capacity and a significantly prolonged cycling life. Even at a current of 10 A (∼138 mA cm^-2), the ms-Ti₄O₇-modified anode demonstrates stable operation for longer than 718 h (700 cycles) with a discharge voltage of 1.2 V, which is much longer than those of a ZnO anode (192 h, 117 cycles) and a Ti₄O₇-particle (p-Ti₄O₇)-modified battery (590 h, 443 cycles). Furthermore, due to the anchoring effect for Zn(OH)₄^2- and the uniform electric field, the effect of mesoporous Ti₄O₇ on inhibiting dendrite formation and shape change of the zinc electrode is highlighted.

Enhanced solar light photocatalytic and antimicrobial activity of green noble metal/TiO2 nanorods

Au/TiO2 and Pt/TiO2 nanocomposites have been processed using a green method. Au and Pt colloidal nanoparticles have been primarily synthesized by mixing their corresponding metal ions with an aqueous solution of corn husk extract, followed by anchoring on the as-synthesized TiO2 nanorods. The structural and morphological properties of green-prepared nanomaterials were systematically investigated by various techniques. The UV–VIS absorption measurements confirmed the formation of colloidal Au and Pt with λmax at 550 and 345 nm, respectively. TEM results show anchoring of spherical Au particles (40 nm) on TiO2 nanorods while smaller Pt particles have been observed on Pt/TiO2 composite. It has been shown that the highest visible light harvesting capability was earned for Au/TiO2 composite due to the surface plasmon resonance (SPR) of Au nanoparticles. The photocatalytic and antimicrobial activity of the nanomaterials was investigated for disinfection of Escherichia coli under solar light irradiation. The green synthesized nanocomposites showed enhanced solar light photocatalytic and antimicrobial activity. The best photocatalytic and antimicrobial activity was obtained for Au/TiO2. This evidences the enhanced SPR of Au nanoparticles and hence an enhancement in the solar light accessible by TiO2 so that a higher amount of reactive oxygen species can be generated, which enhances photocatalytic and antibacterial activity.

Photoreactor-Initiated Acetaldehyde Conversion Rate of a TiO2-Surface-Treated Alumina Photocatalyst Prepared Using the Sol–Gel Method

In this study, a TiO2–alumina photocatalyst was manufactured by coating a surface-treated alumina substrate with TiO2 sol using the sol–gel method, and the photolysis and conversion of acetaldehyde in the gas phase were evaluated. The effects of acetaldehyde flow rate (i.e., retention time), ultraviolet wavelength, moisture, and catalyst heat-treatment temperature on the conversion of acetaldehyde were investigated. The experiments confirmed that a decrease in flow rate (i.e., increase in retention time), increase in moisture level, and decrease in the ultraviolet wavelength of the light source increased the conversion rate of the gaseous acetaldehyde. Among the three heat-treatment temperatures (450, 650, and 850 °C) used in the catalyst manufacturing process, the catalyst treated at 650 °C had the highest acetaldehyde conversion rate. As a result of its increased acetaldehyde decomposition and photoefficiency, the newly manufactured TiO2–alumina photocatalyst is expected to be used alongside a photoreactor as an air-purifying filter. Furthermore, the photocatalyst surface treatment demonstrated herein can be adopted to fabricate various environmentally friendly materials in the future.

Interfacial Deposition of Titanium Dioxide at the Polarized Liquid-Liquid Interface

The interfacial polycondensation of titanium dioxide was studied at the bare and fiberglass membrane supported polarized liquid–liquid interface (LLI). Titanium dioxide synthesis was derived from the titanium (IV) tetrabutoxide (initially dissolved in the 1,2-dichloroethane) interfacial hydrolysis followed by its condensation. Experimental parameters, such as the pH of the aqueous phase and the influence of titanium alkoxide concentration in the organic phase on the electrochemical signal and material morphology, were investigated. The latter was achieved with fiberglass membranes used as the LLI support during TiO₂ interfacial deposition. Cyclic voltammetry was used for the in situ studies, whereas scanning electron microscopy, energy-dispersive X-ray spectroscopy, and infrared spectroscopy were used during ex situ examination. The interfacial polycondensation reaction could be studied using electrified LLI and resulted in the material being a TiO₂ film alone or film decorated with particles.

Flexible Stannum-Doped SrTiO3 Nanofiber Membranes for Highly Sensitive and Reliable Piezoresistive Pressure Sensors

Mechanically flexible ceramic fiber-based electronic skins are attractive materials ascribed to the features of monitoring signals of various physical parameters in a harsh environment, but the inherent brittleness of the ceramic fibers has limited their wide applications in emerging fields, such as fire-protecting clothing. Herein, a strategy to fabricate the flexible stannum(IV)-doped SrTiO3 (SSTO) nanofiber membranes by a facile sol-gel electrospinning method is reported. The calcination temperature and Sn4+ doping content play vital roles in regulating the crystalline and pore structures that are closely relevant to the flexibility and mechanical properties of the resultant SSTO nanofiber membranes. The as-prepared SSTO nanofiber membranes exhibited exceptional flexibility with an optimum tensile strength of 0.22 MPa, an elongation rate of 1.8%, and a Young's modulus of 13.3 MPa. Significantly, the flexible SSTO nanofiber-based piezoresistive sensors exhibited intriguing sensing performance toward pressure involving high sensitivity (2.24 kPa-1) in a low-pressure range (<400 Pa), fast response time (12 ms) and recovery time (32 ms), good durability (>1000 cycles), and excellent stability at different humidity levels and elevated temperatures. Furthermore, the sensor can also accurately monitor the signals of human motion such as finger bending, throat swallowing, and radial pulse. The fabrication of flexible ceramic nanofiber-based piezoresistive sensors would pave the way to fabricate wearable devices for fire-protecting clothing, personal healthcare, real-time human activity detection.

Flexible zirconium doped strontium titanate nanofibrous membranes with enhanced visible-light photocatalytic performance and antibacterial activities

Constructing flexible perovskite structured ceramic fibrous materials would potentially facilitate applications of photocatalysis, wearable devices, and energy storage. However, current perovskite structured ceramic fibrous materials were fragile with small deformation resistance, which have limited their wide applications. Herein, flexible zirconium doped strontium titanate (ZSTO) nanofibrous membranes were fabricated via combining sol-gel and electrospinning methods. The microstructures (pore and crystal) of ZSTO nanofibers were affected by zirconium doping contents and closely relevant to flexibility of resultant membranes. The probable mechanism for flexibility of ZSTO nanofibrous membranes was presented. Furthermore, the silver phosphate modified ZSTO (AZSTO) exhibited superior photocatalytic performance towards tetracycline hydrochloride (TCHC) and antibacterial performance towards Gram-negative and Gram-positive bacteria with visible-light irradiation, including 85% degradation towards TCHC within 60 min, >99.99% inhibition rate and > 3 mm inhibition zone against Gram bacteria. Furthermore, the·superoxide free radical (O₂^-) and holes played significant roles in the degradation of TCHC that verified by radical scavenger experiment. Additionally, the membranes exhibited good reusability over five cycles without tedious recycling operations needed for micro/nanoparticle-based catalysts. The successful fabrication of ZSTO nanofibrous membranes would provide a new insight into photocatalysts, antibacterial materials, and wearable device.

Reverse Micelle Strategy for the Synthesis of MnO x -TiO2 Active Catalysts for NH3-Selective Catalytic Reduction of NO x at Both Low Temperature and Low Mn Content

MnO _x -TiO₂ catalysts (0, 1, 5, and 10 wt % Mn nominal content) for NH₃-SCR (selective catalytic reduction) of NO _x have been synthesized by the reverse micelle-assisted sol-gel procedure, with the aim of improving the dispersion of the active phase, usually poor when obtained by other synthesis methods (e.g., impregnation) and thereby lowering its amount. For comparison, a sample at nominal 10 wt % Mn was obtained by impregnation of the (undoped) TiO₂ sample. The catalysts were characterized by using an integrated multitechnique approach, encompassing X-ray diffraction followed by Rietveld refinement, micro-Raman spectroscopy, N₂ isotherm measurement at -196 °C, energy-dispersive X-ray analysis, diffuse reflectance UV-vis spectroscopy, temperature-programmed reduction technique, and X-ray photoelectron spectroscopy. The obtained results prove that the reverse micelle sol-gel approach allowed for enhancing the catalytic activity, in that the catalysts were active in a broad temperature range at a substantially low Mn loading, as compared to the impregnated catalyst. Particularly, the 5 wt % Mn catalyst showed the best NH₃-SCR activity in terms of both NO _x conversion (ca. 90%) and the amount of produced N₂O (ca. 50 ppm) in the 200-250 °C temperature range.

Eco-Friendly Colloidal Aqueous Sol-Gel Process for TiO2 Synthesis: The Peptization Method to Obtain Crystalline and Photoactive Materials at Low Temperature

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is the peptizing agent. Indeed, depending on its acidic or basic character and also on its amount, it can modulate the crystallinity and morphology of TiO2. Colloidal aqueous TiO2 photocatalysts are mainly being used in various photocatalytic reactions for organic pollutant degradation. The as-synthesized materials seem to have equivalent photocatalytic efficiency to the photocatalysts post-treated with thermal treatments and the commercial Evonik Aeroxide P25, which is produced by a high-temperature process. Indeed, as-prepared, the TiO2 photocatalysts present a high specific surface area and crystalline phases. Emerging applications are also referenced, such as elaborating catalysts for fuel cells, nanocomposite drug delivery systems, or the inkjet printing of microstructures. Only a few works have explored these new properties, giving a lot of potential avenues for studying this eco-friendly TiO2 synthesis method for innovative implementations.

Synthesis and Characterization of Size-Controlled Titania Nanorods through Double Surfactants

A synthetic technique based on a two-step sol-gel hydrothermal method using cetyltrimethylammonium bromide (CTAB) and triblock copolymer PEO₁₀₆-PPO₇₀-PEO₁₀₆ (F127) as double surfactants with the assistance of three amines (ethylamine (EA), diethylamine (DEA), and triethylamine (TEA)) for fabrications of anatase titania nanorods is proposed. The formation and growth mechanisms of TiO₂ crystals are described. We discovered that crystal size reduces with an increase in the number of alkyl substituents on the nitrogen of amines because the steric hindrance of the bulky alkyl substituent around nitrogen suppresses the nucleation and crystal growth rate. The size of titania from 80 to 220 nm is modulated with concentrations of EA, DEA, and TEA. The amines are considered as catalysts for morphological evolution of TiO₂ crystals. The results indicate that the incorporation of double surfactants (F127-CTAB) has a dual role, acting as a chelating agent for titania against external forces and a capping agent inhibiting the three-dimensional growth of TiO₂ crystals.

Novel starch-mediated synthesis of Au/ZnO nanocrystals and their photocatalytic properties

A novel solution-solid synthesis method for preparation of ZnO and Au/ZnO composite nanocrystals using starch matrix has been developed and optimized. The process is characterized by simplicity, environmental compatibility and good performance. Nanocomposite samples with different gold content have been synthesized and studied with respect to their structure, size and shape of nanocrystals, thermal behavior, surface characteristics and optical properties, as well as their photocatalytic activity. We have found that modification of nanocrystalline ZnO with gold nanocrystals strongly influences the porosity of nanocomposites - less micro- and mesopores are formed, which results in a reduced specific surface area. The synthesized ZnO and Au/ZnO nanocrystals are active photocatalysts for the photocatalytic degradation of methylene blue (MB), as a model pollutant dye, in the UV region. There is a decrease in photocatalytic activity with an increase of the gold content in the nanocomposite photocatalyst. The degree of MB degradation obtained with a pure ZnO sample is comparable to that with the Au/ZnO photocatalyst with the lowest gold content 0.05 at. %. New and interesting result has been obtained relating to maximum specific (intrinsic) photocatalytic activity of 0.05 at. % Au/ZnO nanocrystals.

An electrochemical immunosensor modified with titanium IV oxide/polyacrylonitrile nanofibers for the determination of a carcinoembryonic antigen

A highly sensitive electrochemical carcinoembryonic antigen immunosensor based on TiO₂np/polyacrylonitrile nanofibers electrospun on the surface of the discharged battery coal electrode.

Fabrication of Ag3PO4/TiO2@molecular sieve (MS) ternary composites with remarkably enhanced visible light-responded photocatalytic activity and mechanism insight

In this study, Ag₃PO₄/TiO₂@molecular sieve (MS) ternary composites were fabricated via in-situ deposition and hydrothermal growth method for photocatalytic degradation of formaldehyde and sodium isobutyl xanthate (SIBX) under visible light irradiation. XRD, PL, UV-vis, UPS, SEM-EDS and XPS techniques were adopted to characterize the composite. The results show that the MS material was indexed as zeolite P and Ag₃PO₄-TiO₂ hybrid structure could improve the absorption of visible light and greatly inhibit the recombination of photogenerated charge carriers by introducing 3 times TiO₂. After evaluating the photocatalytic activity and kinetics model, it is found that photocatalytic activity is consistent with the apparent first-order kinetic model. The Ag₃PO₄/TiO₂-3@MS ternary composite under visible light irradiation appears the highest removal rate with 97.9% of formaldehyde and 96.7% of SIBX, respectively. Furthermore, the reusability of the photocatalyst was investigated by successive reuse. After five reuses, the removal rates reached 97.3% and 94.6% within 105 min for formaldehyde and SIBX, respectively. At last, the proposed mechanism of the photocatalytic reaction and the degradation routes of formaldehyde and SIBX were systematically discussed.

Simultaneous formation of Bi2O2(OH)(NO3)/BiOBr ultrathin hierarchical microspheres for effectively promoting visible-light-driven photocatalytic activity in environmental remediation

As a two-dimensional nanomaterial, bismuth oxybromide (BiOBr) have attracted tremendous interest in the area of visible-light photocatalysis since it can provide the internal electric field (IEF) through z-axis through its unique electronic band structure. However, the insufficient active sites and rapid recombination rate of charged carriers hamper the efficiency of the photocatalysis. To address these two major obstacles, an enticing strategy of constructing heterojunction was established by introducing Bi₂O₂(OH)(NO₃) (BiON) in BiOBr with the same precursor. Through a facile one-pot hydrothermal synthesis, two Sillén-type layered photocatalysts, with intimately constructed ultrathin heterostructure, was synthesized by the co-precipitation method. In this work, the formation of Bismuth-based heterojunction for charge separation is established by the excessive bismuth nitrate, which subsequently participates with the in situ growth of ultrathin hierarchical microspheres. By attenuating the thickness of BiOBr from 20 nm to 8 nm with the aid of BiON, the photogenerated charges could migrate to the active sites through shorter charge diffusion pathway. Also, the BiOBr and BiON act as an active bridge to promote the separation of electron-hole pairs, which also brings out more active sites due to its increased specific surface area. BiON/BiOBr ultrathin hierarchical microspheres exhibited enhanced visible-light photocatalytic activity for decontaminating several types of pollutants. Besides, the activity of as-prepared BiON/BiOBr was further evaluated by inhibiting the growth of kanamycin-resistant bacteria strains. This study presents a novel strategy to incorporate the crystalline bismuth hydrate nitrate into BiOBr to form ultrathin hierarchical microspheres with high surface area for environmental remediation.

Structural and spectroscopic study of Ho3+ -doped nanotitania host prepared using a sol-gel technique

Holmium (Ho³⁺ )-doped TiO₂ solid laser active materials with different concentrations (1, 3, 5, and 7 wt%) of Ho³⁺ ions were prepared using a sol-gel method. A structural study of the samples using X-ray diffraction (XRD) revealed the anatase phase of pure and doped TiO₂ calcined at 500°C, which is confirmed by (101), (004), (200), (105), (211), (204), (116), (220) and (215) diffraction peaks. XRD analysis showen a deformation along the c-axis of the anatase lattice constant with doping, and a random change in the grain size of the doped titania with respect to pure samples. The presence of the titania bonds (Ti-O-Ti) and (Ti-O) of pure and Ho³⁺ -doped samples were confirmed from the FTIR spectroscopy study of the samples. In addition, it was noted that bands around 1338, and 1339 cm^-1 belonging to 3, 5, and 7 wt% dopant concentrations, while no band for 1 wt% was observed. UV-Vis spectrophotometer and spectrofluorophotometer techniques were used to study the optical and spectroscopic characterizations of these samples. It was found that various fluorescence peaks for Ho³⁺ ions were observed in the UV-vis region under different pump wavelengths. This is a good indication of suitability of the material to be employed as a laser active medium.

Acceleration of ammonium phosphate hydrolysis using TiO2 microspheres as a catalyst for hydrogen production

Titania microspheres are considered an adequate material with low cost and easily attainable pathways, and can be utilized in photocatalytic H2 production to solve the energy crisis. Spherical porous titanium dioxide materials, with nanostructure composition, were chemically synthesized from titanate nanotubes via a simple hydrothermal technique, then added as a catalyst to accelerate the route of ammonium phosphate hydrolysis for hydrogen production. The mechanism of sphere formation from titanate nanotubes is elucidated in detail through the current study. The prepared materials were applied as a photocatalyst to facilitate the separation and transfer of photoinduced electrons, while preventing the recombination of electron-hole pairs. Experimental results show that the obtained microspheres possess significantly enhanced photocatalytic hydrogen (H2) production performance. The amount of photocatalytic hydrogen product using the microspheres is found to be ∼2.5 fold greater than that of titanate nanotubes. Analytical techniques such as field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HR-TEM), simulated visible solar light and X-ray diffraction (XRD) were used for the evaluation and characterization of the developed products, as well as the elucidation of the route of hydrolysis in the hydrogen production process.

Enhancement of Photocatalytic Oxidation of Glucose to Value-Added Chemicals on TiO2 Photocatalysts by A Zeolite (Type Y) Support and Metal Loading

TiO2-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO2 with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO2 nanoparticles and increasing the photocatalytic activity. Effects of the TiO2 dosage to zeolite ratio (i.e., TiO2/ZeY of 10, 20, 40, and 50 mol %) and the silica to alumina ratio in ZeY (i.e., SiO2:Al2O3 of 10, 100, and 500) were firstly studied. It was found that the specific surface area of TiO2/ZeY was 400–590 m2g−1, which was higher than that of pristine TiO2 (34.38 m2g−1). The good properties of 20%TiO2/ZeY photocatalyst, including smaller particles (13.27 nm) and high surface area, could achieve the highest photocatalytic glucose conversion (75%). Yields of gluconic acid, arabinose, xylitol, and formic acid obtained from 20%TiO2/ZeY were 9%, 26%, 4%, and 35%, respectively. For the effect of the silica to alumina ratio, the highest glucose conversion was obtained from SiO2:Al2O3 ratio of 100. Interestingly, it was found that the SiO2:Al2O3 ratio affected the selectivity of carboxylic products (gluconic acid and formic acid). At a low ratio of silica to alumina (SiO2:Al2O3 = 10), higher selectivity of the carboxylic products (gluconic acid = 29% and formic acid = 32%) was obtained (compared with other higher ratios). TiO2/ZeY was further loaded by metals using the microwave-assisted incipient wetness impregnation technique. The highest glucose conversion of 96.9 % was obtained from 1 wt. % Ag-TiO2 (40%)/ZeY. Furthermore, the bimetallic Ag-Cu-loaded TiO2/ZeY presented the highest xylitol yield of 12.93%.

The structure and self-regeneration performance of Salix psammophila-activated carbon modified by Ag and N co-doped TiO2

In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO₃ solution and coating it with an N-doped TiO₂ film to improve its self-regeneration performance in visible light. Ag⁺ was adsorbed and reduced to Ag nanoparticles by AC. Ti element only existed as Ti⁴⁺, and N element was incorporated into TiO₂ mainly in the form of interstitial nitrogen. The photodegradation of Ag-N-TiO₂-AC (AC coated with Ag and N co-modified TiO₂) was enhanced under visible light irradiation because of its three inherent structures: (1) Ag and N co-modified TiO₂ had a smaller average crystal size; (2) with a low bandgap (1.59 eV), the photoresponse region of Ag and N co-modified TiO₂ was greatly extended; (3) the lifetime of the photogenerated holes was increased. With the increase in the AgNO₃ dosage, the Ag-N-TiO₂-AC photodegradation increased, while its adsorption decreased. Because of these synergistic effects, 0.05Ag-0.1N-TiO₂-AC (where 0.05 is the dosage of AgNO₃, g) presented the best self-regeneration performance under visible light irradiation.

In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO₃ solution and coating it with an N-doped TiO₂ film to improve its self-regeneration performance in visible light.

Photocatalytic inactivation of Escherischia coli under UV light irradiation using large surface area anatase TiO2 quantum dots

In this study, high specific surface areas (SSAs) of anatase titanium dioxide (TiO2) quantum dots (QDs) were successfully synthesized through a novel one-step microwave-hydrothermal method in rapid synthesis time (20 min) without further heat treatment. XRD analysis and HR-TEM images showed that the as-prepared TiO2 QDs of approximately 2 nm size have high crystallinity with anatase phase. Optical properties showed that the energy band gap (E g) of as-prepared TiO2 QDs was 3.60 eV, which is higher than the standard TiO2 band gap, which might be due to the quantum size effect. Raman studies showed shifting and broadening of the peaks of TiO2 QDs due to the reduction of the crystallite size. The obtained Brunauer-Emmett-Teller specific surface area (381 m2 g-1) of TiO2 QDs is greater than the surface area (181 m2 g-1) of commercial TiO2 nanoparticles. The photocatalytic activities of TiO2 QDs were conducted by the inactivation of Escherischia coli under ultraviolet light irradiation and compared with commercially available anatase TiO2 nanoparticles. The photocatalytic inactivation ability of E. coli was estimated to be 91% at 60 µg ml-1 for TiO2 QDs, which is superior to the commercial TiO2 nanoparticles. Hence, the present study provides new insight into the rapid synthesis of TiO2 QDs without any annealing treatment to increase the absorbance of ultraviolet light for superior photocatalytic inactivation ability of E. coli.

Environment-Friendly Nanoporous Titanium Dioxide with Enhanced Photocatalytic Activity

Nanoporous TiO2 anatase was environment-friendly prepared using coffee husk extract (CHE) as bio-template instead of hazardous chemicals and solvents and ultrasonic waves. Caffeine and caffeic acid were found to be the main compounds in CHE to modify the morphology of TiO2. The properties of as-prepared titanium dioxide particles were determined by different characterization techniques. The results demonstrate the formation of a meso/macro-porous channel consisting of small TiO2 particles (8–10 nm). The as prepared green nanoparticles exhibited improved photocatalytic activity for the degradation of organic water pollutants with good recyclability. The enhancement in efficiency of green nanoporous TiO2 can be attributed to higher surface area and the presence of more active adsorption sites inside the pores. The current research provides for a low cost, safe, and eco-friendly way to produce efficient photocatalysts for remediation of polluted water.

Preparation and Characterization of Nanocrystalline TiO2 on Microsericite for High-Efficiency Photo-Energy Conversion of Methanol to Hydrogen

TiO2 and TiO2/sericite photocatalysts were successfully synthesized via the sol-gel method by adding a varying amount of acetic acid. The effect of acetic acid on TiO2 and TiO2/sericite photocatalysts was studied. The crystallite size, surface morphology, chemical composition, specific surface area, surficial functional groups, and light absorbance of the prepared photocatalysts were revealed by the analysis of X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometry (SEM-EDS), nitrogen adsorption-desorption isotherms by using BET theory (Brunauer–Emmett–Teller), Fourier-transform infrared spectroscopy (FTIR), and UV-Vis absorption spectrometry. Photo-energy conversion of methanol to hydrogen was also conducted over the prepared photocatalysts. The best hydrogen production was achieved by using the TiO2/sericite photocatalyst to give a hydrogen production rate of 1424 μmol/g·h in 6 h of UV-light irradiation.

Self-Regeneration Performance and Characterization of Silver-Containing Activated Carbon Fibers Coated by Titanium Dioxide

In this study, wood-based activated carbon fibers (WACF) were modified by Ag nanoparticles (AgNPs) and TiO₂ films. The coating of TiO₂ films decreased the AgNPs agglomeration and exfoliation on WACF. As the soaking concentration of AgNO₃ solution (S_conc) increased, AgNPs size and content increased, while the pore volume (especially micropore volume) of fibers reduced. However, at higher S_conc in the range of 0.2 to0.4 mol/L, only slight variations in AgNPs content and pore structure were observable for WACF/TiO₂/Ag (Ag-containing WACF coated by TiO₂ film). WACF/TiO₂/Ag-0.1 (0.1 was the soaking concentration of AgNO₃ solution, mol/L) represented the best self-regeneration performance under the visible light irradiation. The self-regeneration performance of WACF/TiO₂/Ag was determined by the synergistic effects of two factors: adsorption and photodegradation. The abundant pores of WACF/TiO₂/Ag-0.1 increased the methylene blue (MB) concentration of TiO₂ surrounding and facilitated the MB photodegradation. Meanwhile, their suitable Ag content enhanced MB photodegradation. Furthermore, the principal pathway of a chemical reaction between Ag⁺ and WACF was interpreted based on the data of surface elemental constituents and surface functional groups.

Zinc Porphyrin-Functionalized Fullerenes for the Sensitization of Titania as a Visible-Light Active Photocatalyst: River Waters and Wastewaters Remediation

Zinc porphyrin-functionalized fullerene [C60] derivatives have been synthesized and used to prepare titania-based composites. The electrochemical properties and HOMO and LUMO levels of the photosensitizers were determined by electrochemical measurements. Raman and IR techniques were used to study chemical groups present on the titania surface. Absorption properties of the composites were measured in the solid state by diffuse reflectance UV-Vis spectra (DRS). The zeta potential and aggregate sizes were determined using dynamic light scattering (DLS) and electrophoretic light scattering (ELS) techniques. Surface areas were estimated based on Brunauer–Emmett–Teller (BET) isotherms. The photocatalytic activity of the photocatalysts was tested using two model pollutants, phenol and methylene blue. The composite with the highest photocatalytic potential (1/TiO₂) was used for river and wastewater remediation. The photodegradation intermediates were identified by LC-UV/Vis-MS/MS techniques.

Photocatalytic Activity of Nanostructured Titania Films Obtained by Electrochemical, Chemical, and Thermal Oxidation of Ti6Al4V Alloy—Comparative Analysis

Three different Ti6Al4V surface oxidation methods have been applied to obtain three types of titania materials of different nanoarchitecture. Electrochemical oxidation of titanium alloy allowed for obtaining titania nanotubes (TNT), chemical oxidation led to obtain titania nanofibers (TNF), and thermal oxidation gave titania nanowires (TNW). My earlier investigations of these nanomaterials were focused mainly on the estimation of their bioactivity and potential application in modern implantology. In this article, the comparative analysis of the photocatalytic activity of produced systems, as well as the impact of their structure and morphology on this activity, are discussed. The activity of studied nanomaterials was estimated basis of UV-induced degradation of methylene blue and also acetone, and it was determined quantitatively according to the Langmuir–Hinshelwood reaction mechanism. The obtained results were compared to the activity of Pilkington Glass ActivTM (reference sample). Among analyzed systems, titania nanofibers obtained at 140 and 120 °C, possessing anatase and anatase/amorphous structure, as well as titania nanowires obtained at 475 and 500 °C, possessing anatase and anatase/rutile structure, were better photocatalyst than the reference sample. Completely amorphous titania nanotubes, turned out to be an interesting alternative for photocatalytic materials in the form of thin films, however, their photocatalytic activity is lower than for Pilkington Glass ActivTM.

Synthesis and Characterization of Titanium Dioxide Nanoparticles for Application in Enhanced Oil Recovery

In this study, titanium dioxide nanoparticles were synthesized for possible application in enhanced oil recovery. Sol-gel method was employed with titanium (IV) isopropoxide as the precursor. The prepared materials were characterized using Powder X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High-Resolution Transmission electron microscopy (HRTEM) and Brunauer–Emmet–Teller (BET) techniques. Reaction parameter such as calcination temperature was varied during the preparation to obtain the uniform TiO2 nanoparticles with the smallest particle size and high surface area. The results of study revealed that 400 °C is the optimum calcination temperature in preparing TiO2 nanoparticles producing the smallest crystallite and particle sizes. XRD results indicated that the nanoparticles have formed anatase phase at 400 °C and achieved low crystallite size of 7.27 nm with the smallest average particle size of 19.53 nm through FESEM and HRTEM observations. BET analysis had achieved the highest surface area 103.64 m2/g.

Amorphous TiO2 nanostructures: synthesis, fundamental properties and photocatalytic applications

In this review, we mainly highlight the advances made in the development of amorphous TiO₂ nanostructures for photocatalysts. Some perspectives on the challenges and new direction are also discussed.

Mesoporous plasmonic nanocomposites based on Au/Ag-TiO2 aerogels as SERS substrates

Au/Ag-TiO₂ mesoporous nanocomposite aerogels are special materials that can be applied as efficient surface-enhanced Raman spectroscopy (SERS) substrates, in order to detect low concentration of analytes from aqueous environments. At the same time, they benefit from structural and intrinsic properties of aerogels and TiO₂, respectively, and also the plasmonic effects of Au/Ag nanoparticles. Here, several composites of TiO₂ aerogel modified with various concentrations of Au, Ag, and a mixture of Au-Ag nanoparticles were prepared by applying two different methods of synthesis. The SERS detection efficiency of the nanocomposites was established by using the dye crystal violate (CV) as the test molecule. The lowest concentration of CV detectable by SERS, which was 10^-10 M, was found to depend on the method of synthesis, size, and type of the nanoparticles that were used in the nanocomposite structure. In addition, the morphological and structural characterizations of the nanocomposites were investigated through Brunauer-Emmet-Teller results, field emission scanning electron microscopy (FESEM), and transmission electron microscope images.

Influence of the Heat Treatment on the Particles Size and on the Crystalline Phase of TiO₂ Synthesized by the Sol-Gel Method

Titanium biomaterials’ response has been recognized to be affected by particles size, crystal structure, and surface properties. Chemical and structural properties of these nanoparticle materials are important, but their size is the key aspect. The aim of this study is the synthesis of TiO₂ nanoparticles by the sol-gel method, which is an ideal technique to prepare nanomaterials at low temperature. The heat treatment can affect the structure of the final product and consequently its biological properties. For this reason, the chemical structure of the TiO₂ nanoparticles synthesized was investigated after each heat treatment, in order to evaluate the presence of different phases formed among the nanoparticles. FTIR spectroscopy and XRD have been used to evaluate the different structures. The results of these analyses suggest that an increase of the calcination temperature induces the formation of mixed-crystalline-phases with different content of anatase and rutile phases. The results obtained by SEM measurements suggest that an increase in the particles size accompanied by a noticeable aggregation of TiO₂ nanoparticles is due to high temperatures achieved during the thermal treatments and confirmed the presence of different content of the two crystalline phases of titanium dioxide.

Ultrafast Light-Controlled Growth of Silver Nanoparticles for Direct Plasmonic Color Printing

A precision photoreduction technology for the ultrafast high-precision light-controlled growth of silver nanoparticles for printing plasmonic color images is presented. Ultraviolet (UV) patterns with about a million pixels are generated to temporally and spatially regulate the photoreduction of silver salts to precisely create around a million clusters of distinct silver nanoparticles on a titanium dioxide (TiO₂)-capped quartz substrate. The silver nanoparticle-TiO₂-quartz structure exhibits a Fano-like reflection spectrum, whose spectral dip can be tuned by the dimension of the silver nanoparticles for plasmonic color generation. This technology allows the one-step production of multiscale engineered large-area plasmonic substrates without the use of either nanostructured templates or additional nanofabrication processes and thus offers an approach to plasmonic engineering for a myriad of applications ranging from structural color decoration to plasmonic microdevices and biosensors.