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TiO 2 nanomaterials, especially one-dimensional TiO 2 nanofibers fabricated by electrospinning, have received considerable attention in the past two decades, for a variety of basic applications. However, their safe use and easy recycling are still hampered by the inherently subpar mechanical performance. Here, we toughened polycrystalline TiO 2 nanofibers by introducing Al 3+ -species at the very beginning of electrospinning. The resultant long-and-continuous TiO 2 nanofibers achieved a Young's modulus of 653.8 MPa, which is ca. 25-fold higher than that of conventional TiO 2 nanofibers. Within each nanofiber, amorphous Al 2 O 3 -based oxide effectively hindered the coalescence of TiO 2 nanocrystals and potentially repaired the surface groves. The solid-state 17 O-NMR spectra further revealed the toughening strategy on a molecular scale, where relatively flexible Ti-O-Al bonds replaced rigid O-Ti-O bonds at the interfaces of TiO 2 and Al 2 O 3 . Moreover, the modified TiO 2 nanofibers exhibited superb sinter-resistance, without cracking over 900 °C, which was dynamically monitored by TEM. Therefore, flexible-in-rigid TiO 2 fibrous mats can be facilely folded into 3D sponges through origami art. As a potential showcase, the TiO 2 sponges were demonstrated as a duarable and renewable filtrator with a high filtration efficiency of 99.97% toward PM 2.5 and 99.99% toward PM 10 after working for 300 min. This work provides a rational strategy to produce flexible oxide nanofibers and gives an in-depth understanding of the toughening mechanism from the macro-scale to the molecular-scale.

Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Precious metals are widely used as catalysts in industry. It is of critical importance to keep the precious metal ions leached from catalysts at a level below one part per million (ppm) in the final products and to recycle the expensive precious metals. Here we demonstrate a simple and effective method for scavenging precious metal ions from an aqueous solution and thereby reduce their concentrations down to the parts per billion (ppb) level. The key component is a filtration membrane comprised of titania (TiO 2 ) nanofibers whose surface has been functionalized with a silane bearing amino or thiol group. When operated under continuous flow at a rate of 1 mL min -1 and at room temperature, up to 99.95 % of the Pd 2+ ions could be removed from a stock solution with an initial concentration of 100 ppm. This work offers a viable strategy not only for the removal of precious metal ions but also for recovering and further recycling them for use as catalysts. For example, the captured Pd 2+ ions could be converted to nanoparticles and used as catalysts for organic reactions such as Suzuki coupling in a continuous flow reactor. This system can be potentially applied to pharmaceutical industry and waste stream treatment., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Photoelectrochemical (PEC) nanomaterials are critical to producing clean oxygenation or value-added chemical production by utilizing sustainable solar energy, but are always limited by simultaneous integration of architectural engineering and electronic regulation in one structure. Directed by density functional theory (DFT) calculations and finite element analysis (FEA), the bio-inspired ivy-like Fe2O3 heterostructures with enriched oxygen defects on TiO2 nanofibers are designed for boosting PEC performances. Ivy-like Fe2O3 photo-sheets remarkably enhanced the light harvesting by multiple light-mater interactions. The oxygen vacancies on Fe2O3 photo-sheets could aid the photons catching and promote the reactivity at active sites. More importantly, demonstrated by a well-designed dynamic observation, the abundant tip-edges within ivy-like Fe2O3 photo-sheets enabled the surface of heterostructure with hydrophilic and aerophobic properties. The functionalized surface allowed the rapid desorption of produced bubbles and thus ensured a high density of unoccupied active sites for electrolyte accessing. Featured by these attributes, the Fe2O3@TiO2 nanofibers delivered an excellent photocurrent of 40.8 mA/mg, high donor density (1.2 × 1018 cm−3), and rapid oxygen production rate (1 mmol/(L·h)). This work demonstrates a new strategy on nano-structural design for enhancing light-harvesting and making a hydrophilic/aerophobic surface on low-dimensional oxide nanomaterial, holding great potential on designing high-performance PEC devices for producing survival source gas, carbon-neutral fuel, and valued-chemicals. [ABSTRACT FROM AUTHOR]

Up to now, the synthesis of non‐ligand‐capped 2D transition‐metal nanostructures remained big synthetic challenges. Herein, ultrathin and microporous AlOOH/Al2O3 nanosheets were topologically grown on the surface of TiO2‐based nanofibers by a water‐only hydrothermal strategy starting from electrospun Al2O3/TiO2 nanofibers. The TiO2 nanofibers lowered the surface energy for the sustained‐released aluminum species and thereby allowed them in situ hydrated to laminar AlOOH. The metastable AlOOH tended to dehydrate to Al2O3 simultaneously, leaving a well‐maintained 2D structure with sharp corners and steps, as well as enriched micropores. The nanosheets‐on‐nanofibers exhibited 2856–3370 mg/g of adsorption capacity toward RhB and an efficient removal efficiency over 70% at high throughput (30 mL/h). The promoted light‐harvesting by the perpendicularly attached nanosheets further endowed a significant photodegradation for RhB within 1 h. The presented green and facile approach toward the fabrication of 2D metal oxide nanostructures paves the way to a new variety of oxide nanomaterials. [ABSTRACT FROM AUTHOR]

In this work, shape manipulation in porous CeO2 nanofibers was successfully achieved by a simple electrospinning technology with high quality and high reproducibility. By simply tuning the electric field strength during electrospinning, the diameter of as-spun nanofibers composed of Ce(acac)3 and polyvinylpyrrolidone can be precisely controlled. As a result, the morphology of nanofibers can change from columnar to celery-like and belt-like structure. The formation mechanism of this intriguing diameter-dependent morphology can be assigned to the gradient evaporation of solvent across the nanofiber. After calcination at 500 °C, porous CeO2 nanofibers were obtained, showing unusually observed celery-like or belt-like morphologies. These intriguing CeO2 nanofibers exhibited good thermal stability in terms of phase structures and morphologies up to 700 °C. The fibrous CeO2 mats were active toward soot combustion with decreased activation energy, compared with commercial samples. Among three kinds of shapes, the fibrous CeO2 mats made of columnar-like nanofibers were endowed with the lowest activation energy of 120.1 kJ/mol, due to the most effective contact between soot and CeO2 surface, regardless a loose contact mode. [ABSTRACT FROM AUTHOR]

This paper reports a facile fabrication of N-doped graphene quantum dots (N-GQDs) showing controllable chemical properties through a hydrothermal treatment. The N-GQDs have a uniform size of 3.06 ± 0.78 nm and prefer the equilibrium shapes of circle and ellipse due to the minimization of edge free energy. The N/ C atomic ratio in N-GQDs can be precisely tailored in a range from 8.3 at% to 15.8 at% by simply controlling the concentration of N source (ammonium hydroxide). One order of magnitude quantum yield of 34.5% is achieved by N-GQDs, compared with the N-free GQDs, as the substitutional N has an essential role in more effective radiative emission. Excessive N dopants in N-GQDs can lead to photoluminescence quenching, through nonradiative transition back to the ground state. The N-GQDs are further found to be suitable as photocurrent conversion materials due to benign energy matching with anatase nanofibers, the ultrafast electron injection at their interface, and efficient electron transfer. This work provides an efficient and inspiring approach to engineering both chemical components and physical properties of N-GQDs, and will therefore promote their basic research and applications in energy conversion. [ABSTRACT FROM AUTHOR]

Pt/TiO 2 nanofibers (Pt/T-NFs) composite catalysts are prepared through the combination of an electrospinning technique with a reductive impregnation method. Obtained samples are analyzed by various techniques, such as transmission electron microscopy and X-ray diffraction, which reveal that 21 wt.% Pt/T-NFs sample has a homogeneous distribution of smaller Pt nanoparticles of about 4.5 nm in size on the TiO 2 nanofibers surface without large aggregations. Electrochemical studies are carried out using cyclic voltammetry, chronoamperometry and CO stripping voltammetry, which indicate that 21 wt.% Pt/T-NFs catalyst has higher electrochemical surface area and much better activity for methanol electro-oxidation. All Pt/T-NFs catalysts have enhanced stability and CO tolerance for methanol electro-oxidation than commercial Pt/C. The results suggest that Pt/TiO 2 nanofibers catalysts exhibit the better activity for methanol oxidation and are favorable for improving the tolerance to poisoning species. [ABSTRACT FROM AUTHOR]

Under the smart screening design, brittle oxide nanofibers are assembled into elastic aerogel by graphene crosslinkers, demonstrated with multifunction in efficient solar evaporation, space-efficient transporting, intriguing microplastic-removing from water, and reusing as thermal-insulating or smart sensing. [Display omitted] • Under smart simulation, ambient-derived elastic aerogel is assembled from fragments. • The evaporator harvests clean water from microplastic-pollutant powered by sunlight. • Multifunctional evaporator is reused as wearable cold-defending and smart sensing. Lightweight aerogel with functionally-elastic three-dimensional (3D) networks holds great promise, but their function realization is seriously plagued by weak assembling of building blocks with poor mechanical-stabilities. Herein, facile crosslinking brittle oxide nanofibers into elastic 3D fibrous aerogels was demonstrated based on smart screening of components and structures from nanoscale to macroscale in finite element analysis. By employing reduced graphene oxide (RGO) sheets as glues and air bubbles as templates, a simple approach to scalable synthesis of fibrous aerogels was developed. Despite involving rigid oxide element, the fibrous aerogel has good elasticity (under 1000-cycled compressions, withstanding − 196 to 700 °C), ultralow density (7.02 mg·cm−3), ultra-rapid photothermal conversion and water absorption. With these merits, it can efficiently evaporate water from microplastic-polluted seawater powered by solar, enable the vapor to be naturally condensated and harvested in well-designed electricity-free system. High solar-to-vapor efficiency over 100% (1 sun) and microplastic removal efficiency (∼100%) are achieved. Superior to reported evaporators, such elastic aerogel can be reused in wearable cold-defending and pressure sensing even after solar-evaporation. This work provides a universal strategy for smart-simulation designing and simple assembling multifunctional architectures even from brittle building-blocks, opening doors to new opportunities in many advanced applications. [ABSTRACT FROM AUTHOR]

• The surface uniformity of substrate was optimized toward sinter-resistant catalyst. • TiO 2 nanofibers were decorated with well-defined rutile nanorods as substrate. • 3 nm-Pt NPs were stabilized under sinter-promoting situations over 600 °C. • Pt NPs on the nanorods-decorated-TiO 2 nanofibers were active for soot oxidation. One of the most urgent concerns for supported catalysts is to enhance their thermal stability against sintering upon high temperatures (above 300 °C). In this work, we decorated the rough surface of TiO 2 nanofibers with a sheath of rutile nanorods to improve their surface uniformity and explored them as new reliable substrates to stabilize Pt nanoparticles without capping shell. During preparation, the surface-initiated grain growth facilitates the decorated TiO 2 crystals to transform into rutile nanorods, exposing rutile {1 1 1} and {1 1 0} facets. With the presence of TiO 2 nanofibers, these rutile nanorods were finely confined against coalescence and reconstruction upon 700 °C, offering reliable supports for stabilizing metal nanoparticles. Therefore, the diminished driving force for sintering enables the whole catalyst system to withstand temperatures up to 500 °C at an oxidative atmosphere. After calcination at 500 °C, the Pt on rutile nanorods-decorated-TiO 2 nanofibers exhibited nearly 3-times higher reaction rate constant (27.8 s−1·g−1·L−1) toward hydrogenation of 4-nitrophenol over those on unmodified TiO 2. Moreover, such a thermally stable catalyst was active for the oxidation of soot particulates, decreasing the conversion temperature and maintaining a small Pt size of 6.99 nm after the sinter-promoting exothermic oxidation. [ABSTRACT FROM AUTHOR]