Nanostructured TiO2 Research Articles

Advanced Nanostructured Coatings Based on Doped TiO2 for Various Applications

For many years, TiO2-based materials and improving their properties in order to expand their application areas have been the focus of numerous research groups. Various innovative approaches have been proposed to improve the photocatalytic and gas-sensing properties of TiO2 nanostructures. In this review, we aim to synthesize the available information in the literature, paying special attention to the sol–gel technology, which is one of the most frequently used methods for TiO2 synthesis. The influence of dopants on the structural, morphological, optical, and electrical properties of TiO2 and the way to modify them in a controlled manner are briefly discussed. The role of shallow and/or deep energy levels within the TiO2 bandgap in the electron transport behavior of doped TiO2 is emphasized. Selected research on photocatalytic applications in water disinfection, wastewater treatment, and self-sterilizing coatings that contribute to improving the quality of human life and environmental preservation is highlighted. A survey of biosensors that are closely related to medical applications such as cancer detection, implantology, and osteogenesis is also provided. Finally, the pressing problems that need to be solved in view of the future development of TiO2-based nanostructures are listed.

Reduced TiO2 Nanotubes/Silk Fibroin/ZnO as a Promising Hybrid Antibacterial Coating.

The current research aims to elucidate the influence of reduction process of TiO2 nanostructures on the surface properties of a bioinspired Ti modified implant, considering that the interface between a biomaterial surface and the living tissue plays an important role for this interaction. The production of reduced TiO2 nanotubes (RNT) with lower band gap is optimized and their performance is compared with those of simple TiO2 nanotubes (NT). The more conductive surfaces provided by the presence of RNT on Ti, allow a facile deposition of silk fibroin (SF) film using the electrochemical deposition method. This hybrid film is then functionalized with ZnO nanoparticles, to improve the antibacterial effect of the coating. The modified Ti surface is evaluated in terms of surface chemistry, morphology and roughness, wettability, surface energy, surface charge and antibacterial properties. Surface analysis such as SEM, AFM, FTIR and contact angle measurements were performed to obtain topographical features and wettability. FT-IR analysis confirms that SF was effectively attached to TiO2 nanotubes surfaces. The electrochemical deposition of SF and SF-ZnO reduced the interior diameter of nanotubes from ~85 nm to approx. 50-60 nm. All modified surfaces have a hydrophilic character.

Insights into Chemical Bonds for Eliminating the Depletion Region and Accelerating the Photo-Induced Charge Efficient Separation toward Ultrasensitive Photoelectrochemical Sensing.

The empty-space-induced depletion region in photoelectrodes severely exacerbates the recombination of electron-hole pairs, thereby reducing the photoelectrochemical (PEC) analytical performance. Herein, the chemical bond that can suppress the potential barrier and overcome the high energy barrier of out-of-plane Ohmic or Schottky contact is introduced into the PEC sensor to eliminate the depletion region and dramatically promote the separation of electron-hole pairs. Specifically, three-dimensional (3D) hierarchically wheatear-like TiO2 (HWT) nanostructures featuring a large surface area to absorb incident light are crafted as the substrate. The facile carbonized strategy is further employed to engineer the Ti-C chemical bond, serving as the touchstone. The average PL lifetime of HWT-C (4.14 ns) is much shorter than that of the 3D HWT (8.57 ns) due to the promoting effect of the chemically bonded structure on carrier separation. Consequently, the 3D HWT-C covalent photoelectrode (600 μA/cm2) exhibits a 3.6-fold increase in photocurrent density compared with the 3D HWT (167 μA/cm2). Ultimately, the model analyte of the tumor marker is detected, and the linear range is 0.02 ng/mL-100 ng/mL with a detection limitation of 0.007 ng/mL. This work provides a basic understanding of chemical bonds in tuning charge separation and insights on strategies for designing high-performance PEC sensors.

Synergistic effect of surface oxygen vacancies and hydroxyl groups on Cu-doped TiO2 photocatalyst for hydrogen evolution

The intricate nature of the titanium dioxide (TiO2) photocatalytic system, influenced by Cu doping, often yields conflicting outcomes. This study addresses this complexity by examining the impact of Cu ion doping in nanostructured TiO2 to augment its photocatalytic efficacy in hydrogen generation from ethanol-water mixtures. The improved performance is primarily attributed to the generation of oxygen vacancies (Ovac) within the TiO2 lattice. By adjusting the thermal processing parameters, the chemical state of Cu is modulated to optimize photocatalytic performance. Solid-state nuclear magnetic resonance (SSNMR) and density functional theory (DFT) calculations confirm that the presence of Ovac and hydroxyl groups (OH−) surface species not only facilitates local spatial charge separation but also enhances light absorption, thereby improving photocatalytic hydrogen evolution reaction (HER) rate up to 20.2 mmol h−1 g−1 under UV light. Furthermore, a proposed mechanism involves the participation of Ovac and OH− species, supported by Mott-Schottky (M − S) plots and ultraviolet photoelectron spectroscopy (UPS), revealing that Cu–TiO2 exhibits a lower flat band potential (Efb) and smaller work function compared to TiO2. This research underscores the pivotal role of Cu ions and Ovac:OH− in advancing the photocatalytic activity of TiO2-based crystals, imparting noteworthy implications for sustainable hydrogen generation.

Effects of Rare Earth Doping on Structural and Electrocatalytic Properties of Nanostructured TiO2 Nanotubes/SnO2-Sb Electrode for Electrochemical Treatment of Industrial Wastewater

The solvothermal synthesis technique was employed to successfully fabricate a series of rare earth doped SnO2-Sb electrodes on the TNTs array substrate, serving as anode material for electrocatalytic degradation of phenol. The electrode doped with rare earth elements demonstrated superior electrocatalytic activity and stability in comparison to the undoped electrode. The influence of adding rare earth elements (i.e., Gd and Nd) into the precursor solution on the structural and property of TNTs/SnO2-Sb electrodes was studied in detail. The results obtained from SEM and XRD indicated that, compared to TNTs/SnO2-Sb-Nd, TNTs/SnO2-Sb-Gd exhibited a finer grain size due to the smaller ionic radius of the Gd element. This facilitated its incorporation into the SnO2 lattice interior and inhibited grain growth, resulting in a significant decrease in particle size for exposing more active sites. The influence mechanism of rare earth doping on electrochemical activity was investigated through XPS, EPR, LSV, EIS and Hydroxyl radicals (•OH) generation tests. The results demonstrated that the enhanced electrocatalytic activity can be attributed to an increased generation of oxygen vacancies on the electrode surface, which act as active sites for enhancing the adsorption of oxygen species and promoting •OH generation.

Bi-functional carbon foam/TiO2 composite absorber for solar steam generation and photocatalytic purification

Due to the population growth and environmental issues, the demand for clean water is still increasing. To address this problem, harvesting water from organic sewage by solar driven water evaporation is emerging as one of the most promising technologies with its attractive efficiency and negligible energy consumption. However, it still faces a typical defect as pollutants depositing on absorber, which usually limits the recyclability and causes a secondary pollution. In this work, we have provided a composite absorber by uniting carbon foam and nanostructured TiO2 for wastewater purification with dual function of solar steam generation and photocatalytic degradation. The composites selectively utilize the whole solar spectrum, in which low energy visible-near infrared (NIR) photons are transformed into heat by carbon foam, while high energy ultraviolet (UV) photon is converted into redox electron-hole pairs via TiO2. Besides, the combination of these two functional units reveals a synergistic incentive effect between photothermal and photocatalytic processes, based on the alleviated pollutant deposition and enhanced carrier separation. Under a simulated light of 1 kW m−2, the composite ultimately achieves a stable solar steam evaporation rate of 1.0334 kg m−2h−1, combining with a photocatalytic activity of degrading 87 % of MB after 2.5 h illumination.

Silver Nanoparticles/Titanium Dioxide Nanowires Photocatalyst Formation for Microplastic Removal Using Ultraviolet Radiation

Microplastic is the most problematic persistent pollutants in the environment despite of its unique properties for various life application. The objective is to investigate the feasibility and practicability of the nanostructured TiO2 coupling with noble metal in removal polypropylene (PP) microplastics. The TiO2 nanowires (NWs) were synthesized by thermal oxidation of Ti foil under various mixed oxidation environments. TiO2 NWs were successfully grown uniformly and with full coverage over the foil under the condition of ramping in KOH mist and soaking in water vapour at 700 °C for 120 minutes. Heterojunction photocatalyst of Ag/TiO2 NWs was formed using wet impregnation method. Small quantity of Ag nanoparticles (NPs) was attached onto the TiO2 nanowires. The photocatalytic efficiency of the synthesized Ag/TiO2 NWs photocatalyst was tested upon removal of PP microplastic from non-static water bodies under UV irradiation. Coupling Ag NPs with TiO2 NWs have better photocatalytic performance than those without Ag NPs from the reduction of weight loss and the possibility of presence of carbonyl group.

Direct synthesis of nanostructured TiO2 from inorganic metal salt for heterogeneous photocatalysis

Nowadays there is a great concern about the energy crisis and environmental pollution worldwide. As a result, advanced oxidative processes (AOPs) have been studied and used to degrade organic and recalcitrant compounds. Titanium dioxide (TiO2) is the most used for heterogeneous photocatalysis. In general, the TiO2 synthesis by organic routes needs a subsequent heat treatment to eliminate volatile compounds and to obtain the desirable photocatalytic phase. In this work, for the first time, the inorganic synthesis of TiO2 NPs using simple reagents and water was performed in a one-pot reaction and without further heat treatment in order to obtain a photocatalytic semiconductor. A 23 factorial design was used to evaluate the factors (independent variables) that influence the synthesis via controlled precipitation, that is, pH (2 and 8), temperature (25 and 50 °C), and reaction time (5 and 30 min). The NPs were characterized by XRD, FTIR, DTA/TG, BET/BJH techniques, and their photocatalytic performance was determined as the discoloration of methylene blue dye to show the potential degradation of organic matter. The photoactivity of NPs was measured for methylene blue dye decolorization under ultraviolet radiation (UVA, 360 nm). The XRD analysis showed anatase as the only phase for all samples. Ti-O-Ti bonds were observed by infrared analysis (FTIR) and the specific surface area of the samples, determined by N2 adsorption (BET), were 112–118 m2/g, double to that of P25 Evonik (SSA = 50 m2/g). The mass loss was 15–45% due to the presence of water in the samples. However, the non-calcined TiO2 NPs presented 90% degradation of the methylene blue dye (4 ppm) after 3 h under UV radiation (360 nm), showing that the post heat treatment is not necessary for photocatalytic performance. The rate constant for all samples were near 0.0133 min−1. The nanoparticles synthesized via controlled precipitation using a metal salt and ammonium hydroxide proved to be a viable and promising route, because there is no need of a subsequent heat treatment. The route is a fast, one-pot method to obtain photocatalytic TiO2 NPs using simple salts as precursors and water as solvent, without further heat treatment, for the degradation of organic matter.

One-step synthesis of various burr-like TiO2 nanostructures: Nanotubes, nanorods, nanotetrapods, nano-urchins

A one-step liquid phase precipitation method (LPD) was developed to synthesis burr-like TiO2 nanostructures at room temperature. Nanotubes, nanorods, nanotetrapods and nano-urchins with bur-surface were obtained. Growth mechanism was studied by comparing TiO2 obtained with different growth time. The growth of the TiO2 is accompanied with etching of the inner ZnO which resulted in a hollow nanostructure and assembly of TiO2 on both the outside and the inner side of the previously obtained hollow structures. The room-temperature operation, mass production, low cost and universality of this synthesis method could show potential in commercial production of TiO2 nanostructures.

Synthesis of amorphous titania nanostructures by pulsed-laser decomposition of liquid metal-organic precursor with post-annealing transformation into crystalline-layered TiO2 nanorods and nanospheres

Amorphous and non-stoichiometric titania nanoparticles and films are produced by pulsed-laser decomposition of a liquid titanium tetra-isopropoxide (TTIP) precursor bath. Nanoparticles are formed in the TTIP solution, where the submerged laser-induced plasma generates vaporized species that are rapidly quenched by the surrounding (chilled) liquid precursor. Additionally, relatively-dense films are formed on a glass substrate above the surface of the TTIP bath by vapor transport and condensation of pyrolyzed species. Interestingly, upon post-annealing at 400 °C (∼ 0.3 TM) in ambient air of the collected nanoparticles in the bath, a transformation of the amorphous non-stoichiometric titania nanoparticles occurs, producing novel anatase-TiO2 morphologies, such as crystalline-layered nanorods and onion-like nanospheres.Chemical analysis of the as-synthesized particles and films shows they are rich in oxygen and carbon relative to TiO2. As a result, an amorphous-to-crystalline phase transformation during heat treatment in air starts at the surfaces of the nanoparticles, irrespective of their morphologies, and propagates into the interior. During annealing, the in-situ reaction of trapped-in species likely yields gaseous products (e.g., CO, CH4, H2O) that diffuse out of the particles, leaving sufficient Ti and O to enable crystallization of anatase-TiO2.Preliminarily, enhanced photocatalytic activity is found for the novel TiO2 nanostructures for hydrogen production from water reduction with methanol as a sacrificial agent. Decreased band-gap energy and increased absorbance in both the high-energy (i.e., 200 nm – 250 nm) and low-energy (i.e., 340 nm – 440 nm) UV regions are measured compared to that of commercial anatase.

Influence of the Cu doping on the physical and H2 gas sensing properties of TiO2

Due to poor selectivity, existing H2 sensors based on pure TiO2 nanostructures do not exhibit good efficiency at low gas concentrations. Therefore, many studies are carried out to improve the gas sensor properties of TiO2s. In this study, the structural and H2 gas sensing parameters of Cu doped TiO2 thin films obtained by using sputtering method were investigated as a function of Cu doping. In the co-sputtering system, direct current (DC) and radio frequency (RF) sources were used to simultaneously deposit of the Ti (fixed at 100 W in DC) and Cu (25, 35 and 45 W in RF). The structural, optical and morphological properties of the films were discussed in the light of XRD, XPS, UV-VIS, SEM and AFM results. XRD results revealed that the produced thin films have anatase TiO2 structure and the crystallite sizes in the most dominant A(110) plane are in the range of 14–18 nm. According to XPS results, copper ratios in Cu25, Cu35 and Cu45 samples were calculated as 0.433%, 1.598% and 2.233%, respectively. It was also found that CuO and Cu2O formations were formed in addition to the anatase phase only in Cu45 sample from these films. It was determined from the 2D and 3D AFM images that the surface roughness values of the films decreased from 63.92 nm to 12.99 nm with increasing Cu doping. In addition to the structural properties of the produced films, hydrogen gas detection performances at 1000 ppm gas concentration and 200 °C temperature were investigated with the current sensitive gas sensing system. The results reveal that Cu doping significantly improves the H2 gas responses and response times of TiO2s. Among the films produced, the highest gas response (2284) and shortest times (τres:128s, τrec:129s) was obtained in Cu45 thin film. This increase in gas responses was explained by the oxygen vacancy model and the results are presented by comparing pristine TiO2 and other 3d transition metal doped TiO2s in the literature.

Chitosan biopolymer functionalized with graphene oxide and titanium dioxide with Escin metallic nanocomposites for anticancer potential against colon cancer

Our study produced GO-TiO2-chitosan-escin nanocomposites (GTCEnc), characterized them using physical and biological methods, and evaluated their potential as cancer treatment candidates. Standard protocols were used to produce GTCEnc. Nanocomposites are created using XRD, FTIR, UV–Vis, and PL spectroscopy analysis. The morphology and ultrastructure of nanocomposites were investigated using SEM and TEM. Nanocomposites containing TiO2, GO, chitosan, and escin nanostructures were characterized using diffraction, microscopy, and spectroscopy; the antimicrobial activity of GTCEnc was investigated. Various methods were used to test the anticancer activity of GTCEnc against COLO 205 cell lines, including MTT, EtBr/AO, DAPI, JC-1, Annexin-V/FITC, cell cycle analysis, and activation of pro-apoptotic markers, such as caspase-3, -8, and -9. The nanocomposites were cytotoxic to COLO 205 cells, with an IC50 of 22.68 μg/mL, but not to 293T cells. In cells treated with nanomaterials, cytotoxicity, nuclear damage, apoptosis induction, and free radical production were significantly increased. Our finding suggests that GTCEnc has potent anticancer and antibacterial activity in vitro because of its unique nanocomposite properties and antibacterial and anticancer activity in vitro. Additional research is required to understand the clinical efficacy of these nanocomposites.

Structural and Electromagnetic Signatures of Anatase and Rutile NTs and Sheets in Three Different Water Models under Different Temperature Conditions.

Experimental studies of TiO2 nanotubes have been conducted for nearly three decades and have revealed the remarkable advantages of this material. Research based on computer simulations is much rarer, with research using density functional theory (DFT) being the most significant in this field. It should be noted, however, that this approach has significant limitations when studying the macroscopic properties of nanostructures such as nanosheets and nanotubes. An alternative with great potential has emerged: classical molecular dynamics simulations (MD). MD Simulations offer the possibility to study macroscopic properties such as the density of phonon states (PDOS), power spectra, infrared spectrum, water absorption and others. From this point of view, the present study focuses on the distinction between the phases of anatase and rutile TiO2. The LAMMPS package is used to study both the structural properties by applying the radial distribution function (RDF) and the electromagnetic properties of these phases. Our efforts are focused on exploring the effect of temperature on the vibrational properties of TiO2 anatase nanotubes and an in-depth analysis of how the phononic softening phenomenon affects TiO2 nanostructures to improve the fundamental understanding in different dimensions and morphological configurations. A careful evaluation of the stability of TiO2 nanolamines and nanotubes at different temperatures is performed, as well as the adsorption of water on the nanosurface of TiO2, using three different water models.

Electrochemical characterization of conversion coatings of phosphates plus nanostructured TiO2 over magnesium in a simulated body fluid

Electrochemical characterization of conversion coatings of phosphates plus nanostructured TiO2 over magnesium in a simulated body fluid

Mesoporous TiO2 spheres with rich oxygen vacancies for enhanced photocatalytic hydrogen production

Developing efficient photocatalysts for H2 production holds great promise to enhance solar energy conversion. In this study, we present a facile strategy to enhance H2 production by simultaneously engineering Pt cocatalyst and oxygen vacancies (Vo) on mesoporous N doping TiO2, thereby developing efficient photocatalysts for solar energy conversion. Firstly, we employed a structure-directing agent-assisted approach to synthesize a series of mesoporous N doping TiO2 spheres, inducing Vo. Among the samples, the ammonium hydroxide-assisted variant (A-TiO2) exhibited the largest specific surface area of 52.9 m2 g−1 and Vo formation. Subsequently, the Vo-containing mesoporous N-TiO2 spheres (A-TiO2), when doped with 1 wt% Pt and employing methanol as a sacrificial agent, demonstrated remarkable performance. Under simulated sunlight irradiation, A-TiO2/Pt spheres exhibited an impressive hydrogen evolution rate of 14320.89 μmol g−1 h−1, surpassing the most of previously reported TiO2 nanostructures. Experimental studies have elucidated the synergistic effect of Pt nanoparticles and Vo on TiO2 in boosting the photocatalytic reaction. This offers a facile and scalable method for the synthesis of defective TiO2 photocatalysts, thus facilitating mass production and promoting their potential commercialization.

Green Synthesis of TiO2 Nanoparticles using Averrhoa Bilimbi Fruit Extract and their Applications in Photocatalytic Dye Degradation and Anti-bacterial Activities

Due to their numerous distinctive characteristics, nanostructured materials are currently a crucial topic of research. One of the most promising materials today are TiO2 nanostructures, which are one among the transition metal oxides. Due to the absence of any potentially dangerous ingredients and commercially viable procedure, green approaches of nanoparticle synthesis have significant benefit over traditional approaches. The present work reported, the photocatalytic as well as anti-bacterial activity of green synthesized titanium dioxide (TiO2-NPs). An aqueous fruit extract of Averrhoa bilimbi as a capping as well as reducing agent, is utilized for the synthesis of TiO2-NPs. The prepared TiO2-NPs have been characterized by spectral methods using powder XRD (X-ray diffraction) and FTIR (Fourier transforms infrared spectroscopy). Morphological characterization by SEM analysis showed that the synthesized was spherical structure with an average particle size of 60 nm. The photocatalytic dye degradation and anti-bacterial activity have been performed and the result revealed the impressive capability of TiO2-NPs. Hence, the current research work offers a futuristic outlook on a green photocatalysts for profound applications.

Plasmon-Sensitized Silica-Titanium Aerogels as Potential Photocatalysts for Organic Pollutants and Bacterial Strains.

Photocatalysis reactions are of great interest as an effective tool against the profusely increasing population of antibiotic-resistant bacteria species. In particular, the promising evidence on plasmon-sensitized titanium dioxide (TiO2) photocatalysis inspired us to investigate their antibacterial activity stemming from the photogenerated reactive oxygen species (ROS). Herein, TiO2 nanostructures were grown in situ within a silica (SiO2) aerogel matrix with high surface area and porosity, and their ROS-related phototoxic effects against Escherichia coli bacteria were investigated under solar- and visible-light irradiations. Photodegradation profiles obtained from Rhodamine B (RhB) organic dye used as a chemical probe proved that the types of ROS produced by SiO2/TiO2 aerogels varied depending on the electromagnetic spectrum portion that was used during material irradiation. Further, the SiO2/TiO2 aerogel matrix was decorated with silver-gold nanostars (Ag@Au NSs) to enhance its photocatalytic efficiency under visible light irradiations. Our design showed that plasmon-enriched composite aerogels efficiently boosted ROS production under visible light exposures and that the structures containing Ag@Au NSs showed a much more effective antibacterial effect compared to their counterparts.

TiO2-UV detection under different types of acids and rinsing process for films preparation

Titanium dioxide (TiO2) films were prepared by the sol–gel method under different types of acids. Effect of hydrochloric acid (HCl), nitric acid (HNO3) and nature-based solutions (NBS) under ultraviolet (UV) detection of films were investigated. Films were coated by dip coating on glass substrate. Moreover, TiO2 films were compared properties on water rinsing (Ri) and without rinsing (WRi) processes. The phase structure of prepared samples was characterized by means of X-ray powder diffraction (XRD). The results confirm that films were highly crystalline anatase TiO2 and free from other phases of titanium dioxide. For the optical property, the transmittance (%T) observed sharp rise in the violet-ultraviolet transition region and a maximum transmittance of ~80%. Photocurrents were measured under UV intensity of 260 mWcm–2 and DC bias voltage of -20 – 20 volts (V). The results observed that currents increased as bias voltage increased. Current - Voltage (I-V) curves observed different slopes under the different of acids and rinsing process. The photocurrent of TiO2-NBS-Ri was greater than TiO2-HCl-WRi and TiO2-HNO3-WRi of 10 and 20 times; respectively. These findings suggest that the significant effect of the acid and rinsing process on crystalline, morphological, optical, and electrical properties of nanostructured TiO2 films would be useful for applying the device in UV photoelectric detection.

Metode Sintesis Nanopartikel-TiO2 : A Review

Titanium dioxide is an important type of material that has been widely researched by experts. TiO2 can be used as a catalyst and in various other applications because it has unique electronic and optical properties. TiO2 compounds have been synthesized using various synthesis methods. The aim of this review is to summarize various types of TiO2 synthesis methods, morphology and crystallization of nanostructured TiO2. The research method used is literature study or literature study. The results of the reviews show that TiO2 can be synthesized by various methods, namely hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, electrodeposition, sonochemistry and microwaves. The crystal structure phase that is often found is the anatase phase.

Improvement of Photocatalytic Degradation of Titanium Dioxide Nanomaterials by Non-metal Doping

Semiconductor photocatalysis is a process that benefits from sunlight to start chemical reactions. In order to take advantage photocatalytic properties of semiconductors and to achieve better performance structural adjustment is needed. In this study, varying amounts of nitrogen were used to modify TiO2 nanostructures using the sol-gel method. The crystalline structure of the synthesized TiO2 nanostructures was studied using the X-ray diffraction (XRD) technique. X-ray photoelectron spectroscopy (XPS) was conducted to analyse the elemental composition of nanomaterials. XPS analyze confirms that nitrogen is introduced into the lattice of TiO2. The photocatalytic degradation of methylene blue (MB) under UV irradiation was employed to assess the photocatalytic performance of the samples. To evaluate degradation, the absorption of MB over time was measured using a UV-Vis spectrophotometer. As a result, the doping process has been found to improve the photocatalytic performance of TiO2, and 0.2% N doped TiO2 nanostructures demonstrated superior photocatalytic activity for photocatalytic degradation of MB.