TiO2 Nanoflowers Research Articles

Nanowires-Assembled TiO2 Nanorods Anchored on Multilayer Graphene for High-Performance Anodes of Lithium-Ion Batteries.

Multilayer graphene (MLG) prepared via ultrasonic exfoliation has many advantages such as its low-cost and defect-free nature, high electronic conductivity, and large specific surface area, which make it an apt conductive substrate for TiO2 composites. To synthesize graphene/TiO2 hybrids, traditional methods that greatly depend on the chemical bond of oxygen-containing functional groups on graphene with titanium cations are not applicable due to the absence of these functional groups on MLG. In this work, a facile chemical method is developed to directly deposit TiO2 on the MLG surface without the introduction of chemically active groups. With this method, four types of TiO2 materials, that is pure anatase TiO2 nanoparticles, a mixture of anatase TiO2 nanoparticles and rutile TiO2 nanoflowers, pure rutile TiO2 nanoflowers, and pure rutile TiO2 nanorods, are homogeneously anchored on the MLG surface by controlling the amount of HCl in the reactant. Interestingly, the rutile TiO2 nanorods in the TiO2/MLG composite are assembled by many TiO2 nanowires with an ultra-small diameter and ultra-long length, which provides a better synergetic effect for high performances as LIB anodes than other composites. A specific capacity of 631.4 mAh g−1 after 100 cycles at a current density of 100 mA g−1 is delivered, indicating it to be a valuable LIB anode material with low cost and high electrochemical performances.

Construction of 3D TiO2 nanoflower for deep catalytic oxidative desulfurization in diesel: Role of oxygen vacancy and Ti3+

To prevent SOx emission and produce low-sulfur diesel oil, we develop a 3D assembly TiO2 nanoflower catalyst with controllable oxygen vacancies for oxidative desulfurization (ODS) in diesel oil. The roles of oxygen vacancy (OV) and associated Ti3+ in TiO2 are fully discussed: the increased OV and Ti3+ are beneficial for the promoted chemical adsorption of peroxy groups, from − 0.5 eV to − 1.26 eV; also facile to the reduction of the energy barriers of O-O and O-H bonds cleavage, respectively by 1.38 eV and 1.24 eV, thus greatly boosting the generation of hydroxyl radicals·OH and superoxide radicals·O2-. Besides, the ODS reaction undergoes two possible pathways, the mechanism and the kinetics are investigated. Above all, the 100% ODS rate can be obtained in only 30 min under optimal conditions, showing a promising perspective of oxygen vacancy engineering for converting hazardous sulfides into high-value chemicals.

Evaluating Different TiO2 Nanoflower-Based Composites for Humidity Detection.

Unique three-dimensional (3D) titanium dioxide (TiO2) nanoflowers (TFNA) have shown great potential for humidity sensing applications, due to their large surface area-to-volume ratio and high hydrophilicity. The formation of a composite with other materials could further enhance the performance of this material. In this work, the effect of different types of composites on the performance of a TNFA-based humidity sensor was examined. NiO, ZnO, rGO, and PVDF have been explored as possible composite pairing candidates with TiO2 nanoflowers, which were prepared via a modified solution immersion method. The properties of the composites were examined using field emission electron spectroscopy (FESEM), X-ray diffractometry (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) analysis, Hall effect measurement, and contact angle measurement. The performance of the humidity sensor was assessed using a humidity sensor measurement system inside a humidity-controlled chamber. Based on the result, the combination of TiO2 with rGO produced the highest sensor response at 39,590%. The achievement is attributed to the increase in the electrical conductivity, hydrophilicity, and specific surface area of the composite.

Fabrication Approach Impact on Solar-to-Hydrogen Evolution of Protonic Titanate-Derived Nano-TiO2

In terms of the traditional thermal transformation of TiO2 from protonic titanate, herein, we study the impact of the fabrication method of protonic titanate on photocatalytic hydrogen evolution of the derived TiO2 nanostructure. Present synthesis of TiO2 nanostructures involves the structure engineering of protonic titanate with four different synthesis strategies and a subsequent calcination process for conversion of TiO2 nanoflakes (hollow structure), nanorods, nanowires, and nanoflowers. Indeed, the TiO2 nanoflakes exhibit the highest H2 evolution rate of 3.63 mmol·g–1·h–1 among the four different TiO2 photocatalysts. With involvement of 3 wt % Pt, the corresponding H2 production rate of the TiO2 nanoflakes increases to 22.55 mmol·g–1·h–1, which is 3.18, 5.68, and 2.01 times higher than that of nanorods, nanowires, and nanoflowers, respectively. The band structure and photo/electrochemical analysis results propose that the negative conduction band position, fast photoinduced charge carrier separation, and abundant active sites contribute to excellent photocatalytic hydrogen evolution upon the TiO2 nanoflakes.

Porous TiO2/Carbon Dot Nanoflowers with Enhanced Surface Areas for Improving Photocatalytic Activity.

Electron–hole recombination and the narrow-range utilization of sunlight limit the photocatalytic efficiency of titanium oxide (TiO2). We synthesized carbon dots (CDs) and modified TiO2 nanoparticles (NPs) with a flower-like mesoporous structure, i.e., porous TiO2/CDs nanoflowers. Among such hybrid particles, the CDs worked as photosensitizers for the mesoporous TiO2 and enabled the resultant TiO2/CDs nanoflowers with a wide-range light absorption. Rhodamine B (Rh-B) was employed as a model organic pollutant to investigate the photocatalytic activity of the TiO2/CDs nanoflowers. The results demonstrated that the decoration of the CDs on both the TiO2 nanoflowers and the (commercially available AEROXIDE TiO2) P25 NPs enabled a significant improvement in the photocatalytic degradation efficiency compared with the pristine TiO2. The TiO2/CDs nanoflowers, with their porous structure and larger surface areas compared to P25, showed a higher efficiency to prevent local aggregation of carbon materials. All of the results revealed that the introduced CDs, with the unique mesoporous structure, large surface areas and loads of pore channels of the prepared TiO2 NPs, played important roles in the enhancement of the photocatalytic efficiency of the TiO2/CDs hybrid nanoflowers.

Microwave Treatment of Calcium Phosphate/Titanium Dioxide Composite to Improve Protein Adsorption.

Calcium phosphate has attracted enormous attention as a bone regenerative material in biomedical fields. In this study, we investigated the effect of microwave treatment on calcium phosphate deposited TiO2 nanoflower to improve protein adsorption. Hierarchical rutile TiO2 nanoflowers (TiNF) fabricated by a hydrothermal method were soaked in modified simulated body fluid for 3 days to induce calcium phosphate (CAP) formation, followed by exposure to microwave radiation (MW). Coating the dental implants with CAP/TiNF provides a means of improving the biological properties, as the structure, morphology, and thickness of the composites can be controlled. The composites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), field emission transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR), respectively. The composites were identified to be composed of aggregated nano-sized particles with sphere-like shapes, and the calcium phosphate demonstrated low crystallinity. The ability of bovine serum albumin (BSA) to adsorb on MW-treated CAP/TiNF composites was studied as a function of BSA concentration. The Sips isotherm was used to analyze the BSA adsorption on MW-treated CAP/TiNF composites. The MW-treated samples showed high protein adsorption capacity, thereby indicating their potential in various biomedical applications.

Porous Copper Foam‐Based Plasmonic Nanocrystals Modified 3D Semiconductor Nanoflowers for Multifold, Recyclable, and Portable Detection of Environmental Contaminant

AbstractA multifunctional solid‐state surface‐enhanced Raman scattering (SERS) nanoarray exhibiting superior detection sensitivity with high stability and reproducibility has been a hotspot since it provides multiple analyses and on‐site detection platform. Herein, porous Cu foam‐based plasmonic nanocrystals modified 3D mixed phase TiO2 nanoflowers heterojunction for the effective photodegradation under visible‐light exposures is fabricated. Firstly, TiO2 nanoflowers composed of many upright one‐dimensional TiO2 nanopillars possess the merits of a large specific surface area and optical absorption. These nanopillars not only restrain the recombination of electron‐hole pairs by shortening the diffusion length of minority carrier to the TiO2 surface, but also are favorable for the carrier transport in the one‐dimensional nanostructure. Secondly, the introduction of plasmonic nanocrystals with localized surface plasmon resonance effect will boost the overall photoabsorption of TiO2 nanopillars and strengthen the electromagnetic field around the Ag nanocrystals, thus promoting the SERS effect. Under visible‐light excitation, the hot electrons generated by the nonradiative transition of Ag nanocrystals (≈50 nm) transfer to TiO2 to participate in the photocatalytic reaction, which improves the degradation efficiency of pollutants. The ultrasensitive and recyclable substrates displayed by this platform may lay a foundation for rapid detection analysis on environment toxicity when coupled with a portable Raman device.

TiO2 nanoflower photocatalysts: Synthesis, modifications and applications in wastewater treatment for removal of emerging organic pollutants

Titanium dioxide (TiO2) has been considered as one of the most promising photocatalysts nanomaterials and is being used in a variety of fields of energy and environment under sunlight irradiation via photocatalysis. Highly efficient photocatalytic materials require the design of the proper structure with excellent morphology, interfacial structures, optical and surface properties, etc. Which are the key points to realize effective light-harvesting for photocatalytic applications. Hierarchical TiO2 based nanoflower structures (i.e., 3D nanostructures) possess such characteristics and have attracted much attention in recent years. The uniqueness of TiO2 nanoflowers (NFs) with a coarse texture and arranged structures demonstrates higher photocatalytic activity. This review deals with the hydrothermal synthesis of 3D TiO2 NFs and effect of shape/size as well as various key synthesis parameters to improve their optoelectronic and photocatalytic properties. Furthermore, to improve their photocatalytic properties, various strategies such as doping engineering and heterojunction/nanocomposite formation with other functional nanomaterials have been discussed followed by their potential applications in photocatalytic degradation of various emerging pollutants discharged into the wastewater from various sources. Importance of such 3D nanoarchitecutres and future research in other fields of current interest in environments are discussed.

Self-assembled titanium-deficient undoped anatase TiO2 nanoflowers for ultralong-life and high-rate Li+/Na+ storage

Anatase TiO2 is a promising safe and high-rate anode for Li- and Na-ion batteries owing to its moderate redox potential and multi-dimensional ion diffusion paths. However, the capacity, rate and cycle life of anatase TiO2 are severely hindered by the low Li+/Na+ diffusion coefficients. Ti vacancies have been predicted to significantly improve Li+ diffusion kinetics by previous theoretical calculations. However, experimental evidence is still lacking because the existing methods to create Ti vacancies commonly rely on aliovalent doping, i.e., the co-existence of Ti vacancies and foreign anions precludes revelation of the true role and contribution of Ti vacancies alone. The current work reports the synthesis of mesoporous flower-like titanium-deficient anatase TiO2 (TDAT). The formation mechanisms of the Ti vacancies and the micro-architectures are tentatively discussed. Its undoped nature allows elucidation of the unambiguous roles of Ti vacancies on Li+/Na+ storage. Electrochemical results show high capacity, high rate and ultra-long cycle stability for both Li+/Na+ storage in TDAT. DFT calculations reveal that the presence of Ti vacancies results in reduced energy barrier for Li+/Na+ intercalation, enhanced diffusion kinetics, additional Li+/Na+ storage sites and diffusion pathways. For Na+ storage, it achieves a high capacity of 219.9 mAh g−1 at 50 mA g−1, and superior stability over ultra-long 15,000 cycle test at 2000 mA g−1. This work complements with the prevailing view of anion vacancy for improved Li+/Na+ storage.

Efficient Photocatalytic Degradation of the Persistent PET Fiber-Based Microplastics over Pt Nanoparticles Decorated N-Doped TiO2 Nanoflowers

Efficient Photocatalytic Degradation of the Persistent PET Fiber-Based Microplastics over Pt Nanoparticles Decorated N-Doped TiO2 Nanoflowers

CuOx clusters decorated TiO2 for photocatalytic oxidation of nitrogen in air into nitric oxide under ambient conditions

Photocatalytic nitric oxide (NO) synthesis from air is an attractive way to supersede the conventional nitrogen fixation manufacturing technique accompanied by high energy requirements and greenhouse gas emission. The development of efficient photocatalysts for direct solar-driven N2 oxidation to NO without external thermal assistance is highly challenged. Here, CuOx clusters decorated TiO2 nanoflowers with various copper contents are constructed and used for solar-driven air reaction into NO under ambient conditions. When the copper content is 1 wt%, the sample shows the optimal performance with a yield rate of 35.0 mmol m−2 h−1 (7.7 μmol h−1) and an apparent quantum efficiency of 1.77% at 365 nm. A series of in situ and ex situ characterizations reveal Cu2O species and TiO2 support form direct Z-scheme heterojunction over 1%Cu-TiO2. This heterojunction can promote the adsorption and activation of nitrogen and oxygen reactants, leading to the performance enhancement of NO photosynthesis from air. Also, we proposed a possible NO photosynthesis reaction pathway over 1%Cu-TiO2.

A novel (Ti/Ce)UiO-X MOFs@TiO2 heterojunction for enhanced photocatalytic performance: Boosting via Ce4+/Ce3+ and Ti4+/Ti3+ redox mediators

Titanium-substituted cerium-oxo-based UiO MOFs with terephthalate linkers modified by various groups (–Br, –NH2, –NO2) or their derivatives (N-heterocyclic or biphenyl groups) were combined with titanium dioxide in a multistep route to obtain a core-shell-like architecture. DFT simulations showed that Ce- and bimetallic Ti/Ce-MOFs exhibited different charge compensation. Extended characterization revealed the formation of heterojunctions between the (Ti/Ce)UiO-X MOFs and TiO2 nanoflowers, suitable band edge positions, and high specific surface area and porosity, which resulted in effective electron transfer and excellent photocatalytic activity. The photoactivity of the (Ti/Ce)UiO-X@TiO2 composites for hydrogen production or phenol degradation varied according to the order –NH2 > biphenyl > –N– > –H > –Br > –NO2 > pristine TiO2 or –Br > –NH2 > –NO2 > –N– > –H > biphenyl > pristine TiO2. The photocatalytic hydrogen production rate of (Ti/Ce)UiO-66-NH2@TiO2 was 4724 and 19.3 μmol·gcat–1 after 4 h of UV–Vis and visible light irradiation, which were 79 and 19 times higher than that of pristine rutile, respectively.

Crystal Facet Engineering of TiO2 Nanostructures for Enhancing Photoelectrochemical Water Splitting with BiVO4 Nanodots

HighlightsTwo types of BiVO4/TiO2 heterostructure photoanodes comprising TiO2 nanorods (NRs) and TiO2 nanoflowers (NFs) with different (001) and (110) crystal facets, respectively, were designed.The higher photoactivity of BiVO4/TiO2 NFs than BiVO4/TiO2 NRs was attributed to the improvement of charge separation by the TiO2 NFs.The formation of type II band alignment between BiVO4 nanodots and TiO2 NFs expedited electron transport and reduced charge recombination.

TiO2 nanoflowers@Au@MnO2 core-shell composite based on modified Ti foil for flexible supercapacitor electrode

Flexible supercapacitors have received increasing attention due to its portable, flexibility, lightweight and stability. Herein, the flexible supercapacitor electrode with core-shell structure is prepared by in-situ growth of 3D TiO2 nanoflowers on activated Ti foil and uniform coating of Au film and MnO2 nanowires. The porous Ti conductive substrate is achieved by adjusting HCl-KOH corrosion time, thereby providing more channels for charge transport. Free-standing 3D structure of TiO2 NFs provides more surface area to facilitate ions intercalation/deintercalation. Au thin film plays a pivotal role in enhancing conductivity of Ti/TiO2 substrate and adhesion of MnO2 nanowires. The TiO2 NFs@Au@MnO2 composite electrode performs an excellent specific capacitance (1322.5 F g−1 at 1 A g−1) and satisfying cycling stability (86.3% capacity retention after 2000 cycles). Additionally, the assembled solid-state symmetric supercapacitor also displays superior electrochemical performance (223.75 F g−1 at 0.5 A g−1), favourable rate capability (85.8% capacity retention after 2000 cycles) and remarkable flexibility. The combination of 3D architecture nanocomposite electrode with other carbon-based materials will open up a prospect for developing flexible asymmetric supercapacitors.

Fabrication of multifunctional photoelectrodes by strategic placement of monofunctional heterojunction nanoparticles in the centrifuge-based thin film assembly

The work demonstrates the ability to fabricate a multifunctional photoelectrode by the centrifugation-based deposition method using lateral and longitudinal placements of monofunctional heterojunction units. Two composite variants of gC3N4, namely FCN (Fe2O3/gC3N4) and CCN (Co2O3/gC3N4), have been prepared through the solid-state co-synthesis method. Scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction analysis have been used to analyze the constitution of these composites. Stable dispersions of these materials have been prepared in propan-2-ol by ultrasonication and have been used to deposit thin films on TiO2 nanoflower array-based substrates to form various heterojunction specimens, including FCNH (Fe2O3/gC3N4/TiO2), CCNH (Co2O3/gC3N4/TiO2), and MLH (Co2O3 + Fe2O3/gC3N4/TiO2). After that photocatalytic (PC) and photoelectrochemical (PEC) measurements were carried out to ascertain the PEC activities of the fabricated heterojunction specimens, and a comparison was drawn vis-à-vis the control specimen, gC3N4/TiO2 heterojunction. PC and PEC analyses have found that the heterojunction specimen CCNH outperformed all other heterojunction specimens in terms of the generated photocurrent density. It was found that in sample MLH, the lateral placement of Fe2+ alongside Co2+ suppressed the activity of the latter. It shows the capability of the centrifugation-based technique for the easy fabrication of multifunctional photoelectrodes.

Electro-catazone treatment of ozone-resistant drug ibuprofen: Interfacial reaction kinetics, influencing mechanisms, and degradation sites

Electro-heterogeneous catalytic ozonation (E-catazone) is a promising advanced oxidation process using a unique TiO2 nanoflower (TiO2-NF)-coated porous Ti anode. This study investigated interfacial reaction kinetics and the influencing mechanism of E-catazone degrading ozone-resistant drug ibuprofen. An elementary reactions library of the E-catazone process was established. The kinetic rate of key interfacial reactions under different operation parameters was quantitatively resolved. It was found that parameters such as current, initial pH, O3 concentration, and flowrate mainly affect •OH formation and ibuprofen removal via influencing three key interfacial reactions including anodic TiO2-NF surface hydroxylation, subsequent TiO2-NF‒OH/O3 heterogeneous catalysis, and cathodic generation of H2O2. In addition, the degradation pathways and sites of ibuprofen were also predicted via theoretical chemistry calculation, showing that •OH attacked C(12), C(11), or C(6) atom of the benzene ring in the ibuprofen via a radical adduct formation pathway. The results of this study will guide the application of the E-catazone process in the efficient removal of ozone-resistant drugs.

Synthesis, characterization and dielectric properties of rutile TiO2 nanoflowers

In this work, rutile TiO2 nanoflowers with high crystallinity were produced by using an appropriate and a low-cost hydrothermal method. The crystallographic properties, crystalline phase, quality and defects, surface morphology, optical and electronic properties of TiO2 nanoflowers were analyzed by means of instrumental analysis. The crystallite grain size D of the nanoflowers was estimated as 20.90 nm. The optical features of TiO2 nanoflowers were analyzed by using photoluminescence (PL) spectra and UV–visible diffuse reflectance spectrum. The forbidden band gap of the nanoflowers was found to be 3.6 eV. This study calculates the dielectric constants of the TiO2 nanoflowers using Wemple and DiDomenico’s single-oscillator model.

Albumin adsorption on microwave-treated titanium dioxide for dental implant materials

Surface modification of biomedical implants is an established strategy to improve osseointegration. TiO2 nanoflowers (TNF) were deposited on a titanium substrate by hydrothermal technique followed by microwave radiation at 700 W for 5–15 min. Microwave-treated samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy, and Raman spectroscopy to determine their physicochemical characteristics. The XRD and Raman results showed crystalline rutile TiO2. The surfaces of microwave-treated TNF were hydrophilic with split hierarchical structure. The Sips isotherm was used to analyze BSA adsorption on microwave treated TNF samples. The microwave treatment enhances protein adsorption capacity.

Solvent-induced synthesis of hierarchical TiO2 nanoflowers with tunable morphology by monolayer self-assembly for probing the photocatalytic performance

Solvent-induced synthesis of hierarchical TiO2 nanoflowers with tunable morphology by monolayer self-assembly for probing the photocatalytic performance

Performance of Pt–MoS2 co-modified 3-dimensional TiO2 nanoflowers in photocatalytic water splitting reaction

Performance of Pt–MoS2 co-modified 3-dimensional TiO2 nanoflowers in photocatalytic water splitting reaction