One-Dimensional Titanium Dioxide Nanomaterials: Nanowires, Nanorods, and Nanobelts

Recent advances in catalytic systems in the prism of physicochemical properties to remediate toxic CO pollutants: A state-of-the-art review

Carbon monoxide (CO) is the most harmful pollutant in the air, causing environmental issues and adversely affecting humans and the vegetation and then raises global warming indirectly. CO oxidation is one of the most effective methods of reducing CO by converting it into carbon dioxide (CO₂) using a suitable catalytic system, due to its simplicity and great value for pollution control. The CO oxidation reaction has been widely studied in various applications, including proton-exchange membrane fuel cell technology and catalytic converters. CO oxidation has also been of great academic interest over the last few decades as a model reaction. Many review studies have been produced on catalysts development for CO oxidation, emphasizing noble metal catalysts, the configuration of catalysts, process parameter influence, and the deactivation of catalysts. Nevertheless, there is still some gap in a state of the art knowledge devoted exclusively to synergistic interactions between catalytic activity and physicochemical properties. In an effort to fill this gap, this analysis updates and clarifies innovations for various latest developed catalytic CO oxidation systems with contemporary evaluation and the synergistic relationship between oxygen vacancies, strong metal-support interaction, particle size, metal dispersion, chemical composition acidity/basicity, reducibility, porosity, and surface area. This review study is useful for environmentalists, scientists, and experts working on mitigating the harmful effects of CO on both academic and commercial levels in the research and development sectors.

ALD coating of centrifugally spun polymeric fibers and postannealing: case study for nanotubular TiO2 photocatalyst

This work describes the synthesis of highly photocatalytically active TiO2 tubes (TiTBs) by combining centrifugal spinning and atomic layer deposition (ALD). Poly(vinyl pyrrolidone) (PVP) fibers were first produced by centrifugal spinning and subsequently coated with TiO2 with various film thicknesses in a fluidized bed ALD reactor. After annealing of the TiO2 ALD coated PVP fibers, TiO2 tubes (TiTBs) with excellent textural properties and diameters in the range from approx. 170 to 430 nm were obtained. The morphology and structure of all TiTBs were investigated by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller analysis (BET). Liquid phase photocatalysis was conducted to determine the photocatalytic activity of the TiTBs. The photocatalytic activity of the TiTBs obtained after 50 TiO2 ALD cycles (degradation rate 0.123 min-1) was twice that of the reference TiO2 P25. The underlying reasons for the remarkable photocatalytic performance were textural properties of the resulting tubes along with suitable crystallinity, embedded within the 1D tubular morphology. The herein presented proof-of-concept approach paves a way for the processing of various polymeric fibers into various tubular nanostructures.

Tuning the shape and crystal phase of TiO2 nanoparticles for catalysis

Synthesis of TiO₂ nanoparticles with tunable shape and crystal phase has attracted considerable attention for the design of highly efficient heterogeneous catalysts. Tailoring the shape of TiO₂, in the crystal phases of anatase, rutile, brookite and TiO₂(B), allows tuning of the atomic configurations on the dominantly exposed facets for maximizing the active sites and regulating the reaction route towards a specific channel for achieving high selectivity. Moreover, the shape and crystal phase of TiO₂ nanoparticles alter their interactions with metal species, which are commonly termed as strong metal-support interactions involving interfacial strain and charge transfer. On the other hand, metal particles, clusters and single atoms interact differently with TiO₂, because of the variation of the electronic structure, while the surface of TiO₂ determines the interfacial bonding via a geometric effect. The dynamic behavior of the metal-titania interfaces, driven by the chemisorption of the reactive molecules at elevated temperatures, also plays a decisive role in elaborating the structure-reactivity relationship.

Mitochondria-targeted graphene for advanced cancer therapeutics

There have been numerous efforts to develop targeted therapies for treating cancer. The non-specificity of 'classical' cytotoxic chemotherapy drugs and drug resistance remain major challenges in cancer dormancy. Mitochondria-targeted therapy is an alternative strategy for the treatment of numerous cancer types and is heavily dependent on the ability of the anticancer drugs to reach the tumor mitochondria in a safe and selective manner. Over the past two decades, research efforts have provided mechanistic insights into the roles of mitochondria in cancer progression and therapies that specifically target cancer mitochondria. Given that several nanotechnology-driven strategies aimed at therapeutically targeting mitochondrial dysfunction are still in their infancy, this review considers the cross-disciplinary nature of this area and focuses on the design and development of mitochondria-targeted graphene (mitoGRAPH), its immense potential, and future use for selective targeting of cancer mitochondria. This review also provides novel insights into the strategies for preparing mitoGRAPH to destroy the cell powerhouse in a targeted fashion. Targeting mitochondria with graphene may represent an important therapeutic approach that transforms therapeutic interventions. STATEMENT OF SIGNIFICANCE: Mitochondria-targeted therapy represents a major advance for treating several medical conditions. At this time, no nanoparticles (NPs) or nanocarriers are clinically available, which are capable of spatial targeting and controlled delivery of drugs to mitochondria. NPs-based approaches have revolutionized the field of targeted therapy and have demonstrated efficacy for delivering drugs selectively to mitochondria. These NPs show limited results in pre-clinical animal models due to their adverse side effects and inadequate therapeutic outcomes. Over the past decade, graphene has emerged as a potential anticancer agent and has shown great potential in targeting tumor mitochondria in a safe and targeted fashion. This review considers recent advances in the use of mitochondria-targeted graphene (mitoGRAPH) in chemotherapy, photodynamic therapy, photothermal therapy, and combination therapies.

Rational synthesis and lithium storage properties of hierarchical nanoporous TiO2(B) assemblies with tailored crystallites and architectures

In comparison to the common anatase, rutile and brookite phases, the bronze phase TiO₂ (TiO₂(B)) is rarely prepared, and obtaining unique TiO₂(B) structures, especially those with complex configurations remains a great challenge. This work presents a completely new synthetic approach for fabricating hierarchical nanoporous TiO₂(B) assemblies with tailored crystallites and architectures via the reaction between tetrabutyl titanate and normal fatty acids. Three different kinds of normal fatty acids, i.e., pentanoic acid, hexanoic acid, and nonanoic acid were utilized as the sole solvent. After a simple solvothermal treatment, nanoporous TiO₂(B) microspheres constructed by [001]-elongated ultrathin nanorods, randomly aggregated ultrafine nanocrystals, and crystallographically oriented nanocrystals were successfully produced separately. Further investigation revealed that the morphology of the hierarchical assemblies could be modified by using foreign substrates to adjust the growth dynamics of TiO₂(B) crystals. As a good illustration, by introducing graphene nanosheets into the tetrabutyl titanate-pentanoic acid system, nanosized [001]-elongated-ultrathin-nanorod-constructed nanoporous TiO₂(B) assemblies were obtained, which exhibited superior performance as an anode in Li-ion batteries. This work can not only shed new light on TiO₂(B) crystallization, but also provide an effective solution for the rational design of complex TiO₂(B) micro-/nanoarchitectures for desired applications.

Rutile TiO2 single crystals delivering enhanced photocatalytic oxygen evolution performance

Owing to their scientific and technological importance, the development of highly efficient photocatalytic water oxidation systems with rapid photogenerated charge separation and high surface catalytic activity is highly desirable for the storage and conversion of solar energy. A promising candidate is rutile phase titanium dioxide (TiO2), which has been widely studied over half a century. Specifically, oriented single-crystalline TiO2 surfaces with high oxidative reactivity would be most desirable, but achieving these structures has been limited by the availability of synthetic techniques. In this study, a facile and green synthetic approach was developed for the first time to synthesize rutile TiO2 single crystals with regulable reductive and oxidative facets. Glycolic acid (GA) and sodium fluoride (NaF) are used as the crucial and effective phase and facet controlling agents, respectively. The selective adsorption of F- ions on the facets of rutile TiO2 crystals not only plays a key role in driving the nucleation and preferential growth of the crystals with desired facets but also significantly affects their photocatalytic gas evolution reactivity. With heat treatment, the highly stable F--free rutile TiO2 single crystals with a high percentage of oxidative facets exhibit a superior photocatalytic gas evolution rate (≈116 μmol h-1 per 0.005 g catalyst), 8.5 times higher than that of previous F--containing samples.

Recent developments in the synthesis of chemically modified nanomaterials for use in dielectric and electronics applications

Polymer nanocomposites (PNC) have attracted enormous scientific and technological interest due to their applications in energy storage, electronics, biosensing, drug delivery, cosmetics and packaging industry. Nanomaterials (platelet, fibers, spheroids, whiskers, rods) dispersed in different types of polymer matrices constitute such PNC. The degree of dispersion of the inorganic nanomaterials in the polymer matrix, as well as the structured arrangement of the nanomaterials, are some of the key factors influencing the overall performance of the nanocomposite. To this end, the surface functionalization of the nanomaterials determines its state of dispersion within the polymer matrix. For energy storage and electronics, these nanomaterials are usually chosen for their dielectric properties for enhancing the performance of device applications. Although several reviews on surface modification of nanomaterials have been reported, a review on the surface functionalization of nanomaterials as it pertains to polymer dielectrics is currently lacking. This review summarizes the recent developments in the surface modification of important metal oxide dielectric nanomaterials including Silicon dioxide (SiO₂), titanium dioxide (TiO₂), barium titanate (BaTiO₃), and aluminum oxide (Al₂O₃) by chemical agents such as silanes, phosphonic acids, and dopamine. We report the impact of chemical modification of the nanomaterial on the dielectric performance (dielectric constant, breakdown strength, and energy density) of the nanocomposite. Aside from bringing novice and experts up to speed in the area of polymer dielectric nanocomposites, this review will serve as an intellectual resource in the selection of appropriate chemical agents for functionalizing nanomaterials for use in specific polymer matrix so as to potentially tune the final performance of nanocomposite.

Hydrothermal Synthesis of K2Ti6O13 Nanotubes/Nanoparticles: A Photodegradation Study on Methylene Blue and Rhodamine B Dyes

The degradation of methylene blue and rhodamine B dyes using potassium hexatitanate nanoparticles (KTNPs) and potassium hexatitanate nanotubes (KTNTs) synthesized via a hydrothermal method as efficient photocatalysts under UV light irradiation was investigated. The kinetics of degradation was determined for the two different catalysts--KTNPs and KTNTs--by monitoring the optical absorption of the dyes. The as-synthesized KTNPs were found to be spherical in shape with an average particle size of ∼36 ± 1.7 nm, whereas the KTNTs evidenced a tubular hollow structure with ∼7 nm internal diameter and ∼12 nm external diameter, as perused by structural and morphological studies. The larger surface area of KTNTs showed a greater impact on the photodegradation of dyes manifesting their high potential as compared to KTNPs under UV irradiation, and the reusability studies showed more than 90% (KTNTs) and 80% (KTNPs) degradation of the dyes even after the fourth cycle elucidating their stability.

Synthesis and Transformation of Hollow Rutile Titania Wires by Single Spinneret Electrospinning with Sol-Gel Chemistry

The work described below was carried out to understand how to control the morphology of nanostructured titania calcined from electrospun nanofibers. This is the first report of hollow rutile nanofibers synthesized from electrospun nanofibers with short calcination time. Titanium isopropoxide was incorporated into the nanofibers as the titania precursor. The electrospinning technique was used to fabricate ceramic/polymer hybrid nanofibers. The electrospun nanofibers were then calcined to produce rutile titania nanofibers with different morphologies (hollow or solid nanofibers), which were characterized by SEM and TEM. The initial concentration of ceramic precursor and the calcination time were shown to control the morphology of the nanofiber. The hollow morphology was only obtained with a concentration of the precursor within a certain level and with short calcination times. The heat treatment profile contributed to particle growth. At longer times, the particle growth led to the closure of the hollow core and all the nanofibers resembled strings of solid particles. A formation mechanism for the hollow nanofibers is also proposed.

Nanosurfacing Ti alloy by weak alkalinity-activated solid-state dewetting (AAD) and its biointerfacial enhancement effect

Nanoscale manipulation of material surfaces can create extraordinary properties, holding great potential for modulating the implant-bio interface for enhanced performance. In this study, a green, simple and biocompatible nanosurfacing approach based on weak alkalinity-activated solid-state dewetting (AAD) was for the first time developed to nano-manipulate the Ti6Al4V surface by atomic self-rearrangement. AAD treatment generated quasi-periodic titanium oxide nanopimples with high surface energy. The nanopimple-like nanostructures enhanced the osteogenic activity of osteoblasts, facilitated M2 polarization of macrophages, and modulated the cross-talk between osteoblasts and macrophages, which collectively led to significant strengthening of in vivo bone-implant interfacial bonding. In addition, the titanium oxide nanopimples strongly adhered to the Ti alloy, showing resistance to tribocorrosion damage. The results suggest strong nano-bio interfacial effects, which was not seen for the control Ti alloy processed through traditional thermal oxidation. Compared to other nanostructuring strategies, the AAD technique shows great potential to integrate high-performance, functionality, practicality and scalability for surface modification of medical implants.

Recent advances in nanomaterials for therapy and diagnosis for atherosclerosis

Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation in arteries, leading to narrowing and thrombosis. It affects the heart, brain, and peripheral vessels and is the leading cause of mortality in the United States. Researchers have strived to design nanomaterials of various functions, ranging from non-invasive imaging contrast agents, targeted therapeutic delivery systems to multifunctional nanoagents able to target, diagnose, and treat atherosclerosis. Therefore, this review aims to summarize recent progress (2017-now) in the development of nanomaterials and their applications to improve atherosclerosis diagnosis and therapy during the preclinical and clinical stages of the disease.

Nanocomposites containing titanium dioxide for environmental remediation

Titania is considered to be one of the most versatile material in its nanoform. Scientific community looks towards it to address various pressing global problems. One such problem is aquatic pollution arising from organic chemicals such as dyes, pesticides, antibiotics etc. due to industrial, domestic and agricultural activities. Titania proves to be very effective to address this problem owing to its superior photocatalytic properties. In this review, we will review the recent advances in titania-based nanocomposites. The recent advances discussed in this review include synthesis of titania, modification of titania, exploration of various supports such as silica, carbon, graphene etc., that is documented to enhance its environmental remediation properties.

TiO2 Nanowires with Doped g-C3N4 Nanoparticles for Enhanced H2 Production and Photodegradation of Pollutants

With the rapid consumption of fossil fuels, along with the ever-increasing environmental pollution, it is becoming a top priority to explore efficient photocatalysts for the production of renewable hydrogen and degradation of pollutants. Here, we fabricated a composite of g-C₃N₄/TiO₂ via an in situ growth method under the conditions of high-temperature calcination. In this method, TiO₂ nanowires with a large specific surface area could provide enough space for loading more g-C₃N₄ nanoparticles to obtain C₃N₄/TiO₂ composites. Of note, the g-C₃N₄/TiO₂ composite could effectively photocatalyze both the degradation of several pollutants and production of hydrogen, both of which are essential for environmental governance. Combining multiple characterizations and experiments, we found that the heterojunction constructed by the TiO₂ and g-C₃N₄ could increase the photocatalytic ability of materials by prompting the separation of photogenerated carriers. Furthermore, the photocatalytic mechanism of the g-C₃N₄/TiO₂ composite was also clarified in detail.

One-step preparation of C-doped TiO2 nanotubes with enhanced photocatalytic activity by a water-assisted method

In this paper, C-doped TiO₂ nanotubes were prepared in one-step by adding sucrose to water-assisted crystallization solution. The photocatalytic activity was obviously enhanced due to the decrease of the energy band gap after doping.

Synergistic antibacterial activity of physical-chemical multi-mechanism by TiO2 nanorod arrays for safe biofilm eradication on implant

Treatment of implant-associated infection is becoming more challenging, especially when bacterial biofilms form on the surface of the implants. Developing multi-mechanism antibacterial methods to combat bacterial biofilm infections by the synergistic effects are superior to those based on single modality due to avoiding the adverse effects arising from the latter. In this work, TiO2 nanorod arrays in combination with irradiation with 808 near-infrared (NIR) light are proven to eradicate single specie biofilms by combining photothermal therapy, photodynamic therapy, and physical killing of bacteria. The TiO2 nanorod arrays possess efficient photothermal conversion ability and produce a small amount of reactive oxygen species (ROS). Physiologically, the combined actions of hyperthermia, ROS, and puncturing by nanorods give rise to excellent antibacterial properties on titanium requiring irradiation for only 15 min as demonstrated by our experiments conducted in vitro and in vivo. More importantly, bone biofilm infection is successfully treated efficiently by the synergistic antibacterial effects and at the same time, the TiO2 nanorod arrays improve the new bone formation around implants. In this protocol, besides the biocompatible TiO2 nanorod arrays, an extra photosensitizer is not needed and no other ions would be released. Our findings reveal a rapid bacteria-killing method based on the multiple synergetic antibacterial modalities with high biosafety that can be implemented in vivo and obviate the need for a second operation. The concept and antibacterial system described here have large clinical potential in orthopedic and dental applications.

Facile synthesis of ultralong hydroxyapatite nanowires using wormlike micelles as soft templates

Ultralong hydroxyapatite nanowires were synthesized by formation of an entangled long wormlike micelle structure in a three-phase reaction system.

A rutile TiO2 nanobundle as a precursor of an efficient visible-light photocatalyst embedded with Fe2O3

A rutile nanobundle was synthesized via a layered titanate’s conversion at room temperature and used as a precursor of a mesoporous rutile embedded with a tiny Fe2O3 cocatalyst to improve the visible-light photocatalytic activity.

Photocatalytic degradation of microcystin-LR by modified TiO2 photocatalysis: A review

Microcystin-LR (MC-LR), the most toxic and commonly encountered cyanotoxin, is produced by harmful cyanobacterial blooms and potentially threatens human and ecosystems health. Titanium dioxide (TiO₂) photocatalysis is attracting growing attention and has been considered as an efficient, environmentally friendly and promising solution to eliminate MC-LR in the aquatic ecosystems. Over recent decades, scientific efforts have been directed towards the understanding of fundamentals, modification strategies, and application potentials of TiO₂ photocatalysis in degrading MC-LR. In this article, recent reports have been reviewed and progress has been summarized in the development of heterogeneous TiO₂-based photocatalysts for MC-LR photodegradation under visible, UV, or solar light. The proposed photocatalytic principles of TiO₂ and destruction of MC-LR have been thoroughly discussed. Specifically, some main modification methods for improving the drawbacks and performance of TiO₂ nanoparticle were highlighted, including element doping, semiconductor coupling, immobilization, floatability amelioration and magnetic separation. Moreover, the performance evaluation metrics quantum yield (QY) and figure of merit (FOM) were used to compare different photocatalysts in MC-LR degradation. The best performance was seen in N-TiO₂ with QY and FOM values of 2.20E-07 molecules/photon and 1.00E-11 mol·L/(g·J·h). N-TiO₂ or N-TiO₂-based materials may be excellent options for photocatalyst design in terms of MC-LR degradation. Finally, a summary of the remaining challenges and perspectives on new tendencies in this exciting frontier and still an emerging area of research were addressed accordingly. Overall, the present review will offer a deep insight for understanding the photodegradation of MC-LR with modified TiO₂ to further inspire researchers that work in associated fields.

Efficient light harvesting in perovskite layer via three-dimensional TiO2 nanobranched nanorod scaffold

A comparative study was done on three types of TiO2 thin film morphology, i.e., mesoporous nanoparticles, nanorods, and nanobranched nanorods thin films, as the scaffold for the perovskite solar cell. The performances of the perovskite-coated thin films were compared in terms of charge carrier extraction, charge transport, and solar energy harvesting via photoluminescence and UV–vis spectroscopies. TiO2 nanobranched nanorods thin film showed better photovoltaic performance than those of mesoporous nanoparticles and nanorods thin films. The better optical properties of nanobranched nanorods thin film as the scaffold is ascribed to its unique morphological advantages, i.e., remarkable specific surface area along with high-speed pathways for charge carriers. These characteristics lead to great, compact, and uniform perovskite loading, excellent electron transport property, and desired light harvesting performance, which are preferable features for promoting the efficiency of the perovskite solar cells. This paper introduces an outstanding scaffold for fabrication of high-performance perovskite solar cells.

Porous TiO2 Film Immobilized with Gold Nanoparticles for Dual-Polarity SALDI MS Detection and Imaging

Surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) has become an attractive complementary approach to matrix-assisted laser desorption/ionization (MALDI) MS. SALDI MS has great potential for the detection of small molecules because of the absence of applied matrix. In this work, a functionalized porous TiO₂ film immobilized with gold nanoparticles (AuNPs-FPTDF) was prepared to enhance SALDI MS performance. The porous TiO₂ films were prepared by the facile sol-gel method and chemically functionalized for dense loading of AuNPs. The prepared AuNPs-FPTDF showed superior performance in the detection and imaging of small molecules in dual-polarity modes, with high detection sensitivity in the low pmol range, good repeatability, and low background noise compared to common organic MALDI matrixes. Its usage efficiently enhanced SALDI MS detection of various small molecules, such as amino acids and neurotransmitters, fatty acids, saccharides, alkaloids, and flavonoids, as compared with α-cyano-4-hydroxycinnamic acid, 9-aminoacridine, and the three precursor substrates of AuNPs-FPTDF. In addition, the blood glucose level in rats was successfully determined from a linearity concentration range of 0.5-9 mM, as well as other biomarkers in rat serum with SALDI MS. More importantly, the spatial distribution of metabolites from the intact flowers of the medicinal plant Catharanthus roseus was explored by using the AuNPs-FPTDF as an imprint SALDI MS substrate in dual-polarity modes. These results demonstrate wide applications and superior performances of the AuNPs-FPTDF as a multifunctional SALDI surface with enhanced detection sensitivity and imaging capabilities.

Role of Metal Ion-Linked Multilayer Thickness and Substrate Porosity in Surface Loading, Diffusion, and Solar Energy Conversion

Metal ion-linked multilayers offer an easily prepared and modular architecture for controlling energy and electron transfer events on nanoparticle, metal oxide films. However, unlike with planar electrodes, the mesoporous nature of the films inherently limits both the thickness of the multilayer and subsequent diffusion through the pores. Here, we systematically investigated the role of TiO₂ nanoparticle film porosity and metal ion-linked multilayer thickness in surface loading, through-pore diffusion, and overall device performance. The TiO₂ porosity was controlled by varying TiO₂ sintering times. Molecular multilayer thickness was controlled through assembling Zn^II-linked bridging molecules (B = p-terphenyl diphosphonic acid) between the metal oxide and the Ru(bpy)₂((4,4'-PO₃H₂)₂bpy)]Cl₂ dye (RuP), thus producing TiO₂-(B_n)-RuP films. Using attenuated total reflectance infrared absorption and UV-vis spectroscopy, we observed that at least two molecular layers (i.e., TiO₂-B₂ or TiO₂-B₁-RuP) could be formed on all films but subsequent loading was dependent on the porosity of the TiO₂. Rough estimates indicate that in a film with 34 nm average pore diameter, the maximum multilayer film thickness is on the order of 4.6-6 nm, which decreases with decreasing pore size. These films were then incorporated as the photoanodes in dye-sensitized solar cells with cobalt(II/III)tris(4,4'-di-tert-butyl-2,2'-bipyridine) as a redox mediator. In agreement with the surface-loading studies, electrochemical impedance spectroscopy measurements indicate that mediator diffusion is significantly hindered in films with thicker multilayers and less porous TiO₂. Collectively, these results show that care must be taken to balance multilayer thickness, substrate porosity, and size of the mediator in designing and maximizing the performance of new multilayer energy and electron management architectures.

Implementation of ferroelectric materials in photocatalytic and photoelectrochemical water splitting

As a promising technology for sustainable hydrogen generation, photocatalytic (PC) and photoelectrochemical (PEC) water splitting have gathered immense attention over a half-century. While many review articles have covered extensive research achievements and technology innovations in water splitting, this article focuses on illustrating how the ferroelectric polarization influences charge separation and transportation in photocatalyst heterostructures during PC and PEC water splitting. This article first discusses the fundamentals of PC and PEC water splitting and how these electrochemical processes interact with the ferroelectric polarization-induced interfacial band bending, known as piezotronics. A few representative ferroelectric material-based heterogeneous photocatalyst systems are then discussed in detail to illustrate the effects of polarization, space charge region, and free charge concentration, which are critical factors determining the ferroelectric influences. Finally, a forward looking statement is provided to point out the research challenges and opportunities in this promising interdisciplinary research field between ferroelectrics and electrochemistry for clean energy applications.

Effect of Fe-doping on bending elastic properties of single-crystalline rutile TiO2 nanowires

Transition-metal-doping can improve some physical properties of titanium dioxide (TiO₂) nanowires (NWs), which leads to important applications in miniature devices. Here, we investigated the elastic moduli of single-crystalline pristine and Fe-doped rutile TiO₂ NWs using the three-point bending method, which is taken as a case study of impacts on the elastic properties of TiO₂ NWs caused by transition-metal-doping. The Young's modulus of the pristine rutile TiO₂ NWs decreases when the cross-sectional area increases (changing from 246 GPa to 93.2 GPa). However, the elastic modulus of the Fe-doped rutile NWs was found to increase with the cross-sectional area (changing from 91.8 GPa to 200 GPa). For NWs with similar geometrical size, the elastic modulus (156.8 GPa) for Fe-doped rutile NWs is 24% smaller than that (194.5 GPa) of the pristine rutile TiO₂ NWs. The vacancies generated by Fe-doping are supposed to cause the reduction of elastic modulus of rutile TiO₂ NWs. This work provides a fundamental understanding of the effects of transition-metal-doping on the elastic properties of TiO₂ NWs.

All-Solid-State Lithium Ion Batteries Using Self-Organized TiO2 Nanotubes Grown from Ti-6Al-4V Alloy

All-solid-state batteries were fabricated by assembling a layer of self-organized TiO₂ nanotubes grown on as anode, a thin-film of polymer as an electrolyte and separator, and a layer of composite LiFePO₄ as a cathode. The synthesis of self-organized TiO₂ NTs from Ti-6Al-4V alloy was carried out via one-step electrochemical anodization in a fluoride ethylene glycol containing electrolytes. The electrodeposition of the polymer electrolyte onto anatase TiO₂ NTs was performed by cyclic voltammetry. The anodized Ti-6Al-4V alloys were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of the anodized Ti-6Al-4V alloys were investigated by cyclic voltammetry and chronopotentiometry techniques. The full-cell shows a high first-cycle Coulombic efficiency of 96.8% with a capacity retention of 97.4% after 50 cycles and delivers a stable discharge capacity of 63 μAh cm⁻² μm⁻¹ (119 mAh g⁻¹) at a kinetic rate of C/10.

Complex cytotoxicity mechanism of bundles formed from self-organised 1-D anodic TiO2 nanotubes layers

The present study reports on a comprehensive investigation of mechanisms of in vitro cytotoxicity of high aspect ratio (HAR) bundles formed from anodic TiO₂ nanotube (TNT) layers. Comparative cytotoxicity studies were performed using two types of HAR TNTs (diameter of ∼110 nm), differing in initial thickness of the nanotubular layer (∼35 μm for TNTs-1 vs. ∼10 μm for TNTs-2). Using two types of epithelial cell lines (MDA-MB-231, HEK-293), it was found that nanotoxicity is highly cell-type dependent and plausibly associates with higher membrane fluidity and decreased rigidity of cancer cells enabling penetration of TNTs to the cell membrane towards disruption of membrane integrity and reorganization of cytoskeletal network. Upon penetration, TNTs dysregulated redox homeostasis followed by DNA fragmentation and apoptotic/necrotic cell death. Both TNTs exhibited haemolytic activity and rapidly activated polarization of RAW 264.7 macrophages. Throughout the whole study, TNTs-2 possessing a lower aspect ratio manifested significantly higher cytotoxic effects. Taken together, this is the first report comprehensively investigating the mechanisms underlying the nanotoxicity of bundles formed from self-organised 1-D anodic TNT layers. Except for description of nanotoxicity of industrially-interesting nanomaterials, the delineation of the nanotoxicity paradigm in cancer cells could serve as solid basis for future efforts in rational engineering of TNTs towards selective anticancer nanomedicine.

Effect of aspect ratios of rutile TiO2 nanorods on overall photocatalytic water splitting performance

The spatial separation of reduction and oxidation reaction sites on the different facets of a semiconductor is an ideal and promising route for overall photocatalytic water splitting due to efficient charge carrier separation. Rutile TiO2 has separate oxidation and reduction crystal facets and can be used to achieve direct splitting of pure water under ultraviolet (UV) light irradiation. In order to improve the rate of water oxidation reaction, the ratio of different crystal facets of rutile should be regulated controllably. However, the preparation of rutile TiO2 architecture has been limited by the availability of synthetic techniques. In this study, rutile TiO2 nanorods with various aspect ratios were accurately prepared in the presence of Cl- anions and H+ cations, which were found to play a crucial role in forming the morphology of rutile TiO2 nanorods. In addition, the mechanism involving the growth of rutile TiO2 nanorods with different aspect ratios is proposed. Rutile TiO2 nanorods with a high proportion of oxidative (111) facets provided higher overall water splitting reactivity.

Recent advances in the synthesis of hierarchically mesoporous TiO2 materials for energy and environmental applications

Because of their low cost, natural abundance, environmental benignity, plentiful polymorphs, good chemical stability and excellent optical properties, TiO₂ materials are of great importance in the areas of physics, chemistry and material science. Much effort has been devoted to the synthesis of TiO₂ nanomaterials for various applications. Among them, mesoporous TiO₂ materials, especially with hierarchically porous structures, show great potential owing to their extraordinarily high surface areas, large pore volumes, tunable pore structures and morphologies, and nanoscale effects. This review aims to provide an overview of the synthesis and applications of hierarchically mesoporous TiO₂ materials. In the first section, the general synthetic strategies for hierarchically mesoporous TiO₂ materials are reviewed. After that, we summarize the architectures of hierarchically mesoporous TiO₂ materials, including nanofibers, nanosheets, microparticles, films, spheres, core-shell and multi-level structures. At the same time, the corresponding mechanisms and the key factors for the controllable synthesis are highlighted. Following this, the applications of hierarchically mesoporous TiO₂ materials in terms of energy storage and environmental protection, including photocatalytic degradation of pollutants, photocatalytic fuel generation, photoelectrochemical water splitting, catalyst support, lithium-ion batteries and sodium-ion batteries, are discussed. Finally, we outline the challenges and future directions of research and development in this area.

Insights into Theranostic Properties of Titanium Dioxide for Nanomedicine

Titanium dioxide (TiO2) nanostructures exhibit a broad range of theranostic properties that make them attractive for biomedical applications. TiO2 nanostructures promise to improve current theranostic strategies by leveraging the enhanced quantum confinement, thermal conversion, specific surface area, and surface activity. This review highlights certain important aspects of fabrication strategies, which are employed to generate multifunctional TiO2 nanostructures, while outlining post-fabrication techniques with an emphasis on their suitability for nanomedicine. The biodistribution, toxicity, biocompatibility, cellular adhesion, and endocytosis of these nanostructures, when exposed to biological microenvironments, are examined in regard to their geometry, size, and surface chemistry. The final section focuses on recent biomedical applications of TiO2 nanostructures, specifically evaluating therapeutic delivery, photodynamic and sonodynamic therapy, bioimaging, biosensing, tissue regeneration, as well as chronic wound healing.