Mesoporous Nanofibers Research Articles

BiVO4@TiO2 core–shell hybrid mesoporous nanofibers towards efficient visible-light-driven photocatalytic hydrogen production

We report designed BiVO4@TiO2 core–shell hybrid mesoporous nanofibers for efficient photocatalytic hydrogen production under visible irradiation.

Influence of calcination on the morphology and crystallinity of titanium dioxide nanofibers towards enhancing photocatalytic dye degradation

The development of titanium dioxide (TiO2) nanostructures with superior morphology and crystallinity is crucial for the photocatalytic degradation of textile dyes. This study highlights the evolution in the morphology and crystallinity of electrospun TiO2 nanofibers using polyvinylpyrrolidone (PVP) support in relation to applied calcination temperature, and their influence towards the photocatalytic dye degradation performance of the material. Results showed distinct differences in the thermal decomposition patterns of (PVP) on the fiber surface and the inner core, where it is dependent on the presence of oxygen. These differences drastically affect the morphology of the obtained fibers especially its surface area and porosity. Crystallinity of the embedded TiO2 particles increases with higher calcination temperature which contributes to higher photocatalytic performance. Highly mesoporous nanofibers with crystalline anatase TiO2 particles, together with fiber diameter of 118.3 ± 6.30 nm and surface area of 72.3219 m2 g−1 are obtained at 500 °C. The combination of these properties produced the best photocatalytic dye degradation rate constant of 0.080 29 min−1 and 0.0543 min−1 for methylene blue and methyl orange respectively. The performance can be attributed to a combination of high particle crystallinity and fiber porosity and surface area.

Fabrication of Carbonaceous Nanotubes and Mesoporous Nanofibers as Stable Anode Materials for Lithium-Ion Battery

The morphologies and pore architectures of carbon nanostructures could be precisely controlled via a self-assembly process. This work presented resorcinol-formaldehyde resin-silica composite nanofibers, which were synthesized through a sol–gel method under the help of costructure directing agent (CSDA) (S)-β-citronellol and n-hexanol. The self-assembly process and the nanostructure of obtained composite nanofibers were changed by adding different CSDA. After carbonization and getting rid of silica, carbonaceous nanotubes and mesoporous nanofibers were obtained, respectively. Their electrochemical performance was tested as anode materials for lithium-ion batteries (LIBs). Stable discharge capacities of 574.3 mA h g–1 for carbonaceous nanotubes and 609.9 mA h g–1 for mesoporous carbonaceous nanofibers after 300 cycles were achieved at current density of 0.1 A g–1. Thus, a facile method of designing and fabricating excellent carbon anode candidates for LIBs was provided.

Indium-doped ZnO mesoporous nanofibers as efficient electron transporting materials for perovskite solar cells

We introduce a viable electrospinning route for the development of highly porous indium-doped (In-doped) ZnO nanofibers as electron transporting materials (ETMs) in perovskite solar cells (PSCs) for the first time ever. The nanofibers ETMs with optimal thickness leads to highly efficient and hysteresis-free PSCs with an average power conversion efficiency (PCEavg) of 16.03% and a best power conversion efficiency (PCEbest) of 17.18%, thanks to high porosity and high crystallinity of the nanofibers, better infiltration of the absorber and rapid charge transport characteristics due to indium (In) doping. Furthermore, the modification of In-doped ZnO nanofibers ETMs, by coating a thin layer of a polymer polyethyleneimine (PEI) further enhances the PCEavg to 16.86% (PCEbest = 18.69%) by effectively reducing the energy barrier for electron extraction due to a reduced work function. This study reveals that In-doped ZnO nanofibers are the best ETMs for generating the inexpensive and high efficiency PSCs with long-term stability.

Poly(styrene-block-methylmethacrylate) derived electrospun mesoporous nanofibers

Mesoporous materials are of great interest in fields of catalysis, biosensing, gas sensing and adsorption due to their high specific surface area as compared to macroporous materials and lower pore diffusion resistance when compared to microporous materials. The microphase separation property of block copolymers can be used to obtain mesoporous materials by selectively etching one of its polymer blocks. In this study, we have successfully demonstrated the synthesis of mesoporous poly (styrene-block-methylmethacrylate) (PS-b-PMMA) nanofibers using electrospinning. Morphology of these PS-b-PMMA fibers obtained by electrospinning depends on a number of process as well as solution parameters which were tuned to obtain long uniform and continuous fibers as confirmed by field emission electron microscopy. The nanofibers thus obtained were thermally annealed to assist the phase separation. Later the fibers were exposed to ultraviolet radiation followed by etching with a weak acid to remove the degraded polymer block leading to mesoporous PS-b-PMMA nanofibers, as confirmed by transmission electron microscopy. We also demonstrate the direct synthesis of porous PS-b-PMMA fibers driven by the rapid vaporization of the highly volatile solvent. A comprehensive study of the effect of electrospinning solvent and annealing and etching conditions on the specific surface area, porous structure including pore volume and pore size distribution is carried out using the nitrogen adsorption-desorption isotherms and the small angle X-ray scattering (SAXS). We also analyzed the mesoporous nature of PS-b-PMMA nanofibers using fractal dimension analysis.

Mesoporous Nanofibers Mediated Targeted Anti-cancer Drug Delivery

ABSTRACTTumor tissue has different acidity compared to normal tissue. Localized drug delivery that release chemotherapeutic medications upon stimulation via pH changes is a promising strategy in cancer therapy for adjuvant therapies after surgical resection to reduce the risk of local recurrence. In this study, a mesoporous nanofibrous system with acidic pH-triggered “caps” has been for the first time developed for localized on-demand drug release to target tumor cells, without biological damage to normal cells while maintaining their structural integrity to support future tissue regeneration. Specifically, polyacrylic acid (PAA) was grafted on electrospun mesoporous silica nanofibers (MSFs) and the obtained PAA-MSFs allowed efficient drug loading at neural pH and on-demand releasing at acidic cancer subcellular compartments, based on pH-dependent electrostatic interactions associated with protonation/deprotonation of PAA. The The hybrid mesoporous nanofibers a low cytotoxicity to normal cells and a high killing efficiency to cancer cells. The system demonstrated a great potential as tumor targeting drug delivery system.

Template-free synthesis of MgO mesoporous nanofibers with superior adsorption for fluoride and Congo red

MgO mesoporous nanofibers were obtained by a template-free electrospinning method. The unique bumpy-structure was obtained on the surface of nanofibers that could enhance the surface area and provide more active sites for adsorption. The formation mechanism of the bumpy-structure has been investigated. The as-prepared MgO nanofibers with a high surface area of 194.17 m2 g−1 exhibited excellent adsorption capacities for fluoride of 237.49 mg g−1. Furthermore, the MgO nanofibers showed selective adsorption for different organic dyes and have superior adsorption capacity for Congo red (4802.27 mg g−1). The adsorption processes for both fluoride and Congo red were systematically investigated, which were found to follow the pseudo-second-order kinetic model. By comparison with the reported fabrication routes and adsorption capacities of mesoporous MgO, the synthesis process is simple, controllable and template-free, and the superior adsorption performance provided a potential adsorbent for the removal of fluoride and Congo red in wastewater treatment. The high surface area of the MgO mesoporous nanofibers might also promote its application in basic catalysis and other fields.

Pt-In2O3 mesoporous nanofibers with enhanced gas sensing performance towards ppb-level NO2 at room temperature

Pt-loaded In2O3 mesoporous nanofibers (NFs) have been prepared by electrospinning, followed by a facile reduction method. The sample obtained by adding tea saponin into the spinning solution, sample In-TS, displays a more than 4 times higher specific surface area, value of 86.9 m2 g−1, than that of conventionally prepared samples. The loading with small-sized Pt nanoparticles (NPs) determines excellent gas sensing performance towards NO2 down to ppb level (Rg/Ra = 2.8 to 10 ppb and 23.9–1 ppm) at room temperature (RT), by that significantly lowering the power consumption. The reason is that the open pores and channels on the mesoporous NFs generated by the foaming agent not only promote the adsorption and desorption of NO2 molecules on the sensing layers, but also improves the transduction function of the sensors by ensuring that there are no parts of the fiber that are not accessible to the gases. The introduction of Pt to the mesoporous NFs could accelerate the dissociation of absorbed oxygen and the active surface reactions in NO2 owing to the catalytic property and chemical sensitization of well-dispersed Pt NPs. Due to the unique gas sensing performance, sample In-TS-Pt has a prospect for applications in low-concentration NO2 detection at RT.

Direct chitin conversion to N-doped amorphous carbon nanofibers for high-performing full sodium-ion batteries

Currently, renewable and low-cost electrode materials are being intensively pursued to meet the development of sustainable electrochemical energy-storage systems. Chitin, which is the second most abundant biopolymer throughout the natural world and can be sourced cheaply from the exoskeletons of arthropods and shells of cephalopods, has many attractive properties such as renewability, nontoxicity, intrinsically fibrous structure and high nitrogen content. In this study, nitrogen-doped amorphous carbon nanofibers (NACF) fabricated by direct pyrolysis of chitin, were used as the anode material in sodium-ion batteries (SIBs) for the first time. The NACF electrode delivered a high reversible capacity of 320.6mAhg−1 with excellent rate capability and long cyclability. The superior electrochemical performance can mainly be attributed to synergistic effects of the unique one-dimensional mesoporous nanofibers facilitating the transmission of electrons/electrolyte, and the N-doped amorphous nanostructure increasing electrical conductivity and number of active sites. Furthermore, a sodium-ion full cell was constructed by coupling the NACF electrode with a Prussian blue cathode, and it delivered 115mAhg−1 while retaining 90% of the capacity after 200 cycles. Our work will hopefully inspire the research community to explore other advanced materials with value-added attributes that can be generated by appropriate treatment of renewable bio-waste.

A Highly Efficient and Robust Cation Ordered Perovskite Oxide as a Bifunctional Catalyst for Rechargeable Zinc-Air Batteries.

Of the various catalysts that have been developed to date for high performance and low cost, perovskite oxides have attracted attention due to their inherent catalytic activity as well as structural flexibility. In particular, high amounts of Pr substitution of the cation ordered perovskite oxide originating from the state-of-the-art Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) electrode could be a good electrode or catalyst because of its high oxygen kinetics, electrical conductivity, oxygen capacity, and structural stability. However, even though it has many favorable intrinsic properties, the conventional high-temperature treatment for perovskite synthesis, such as solid-state reaction and combustion process, leads to the particle size increase which gives rise to the decrease in surface area and the mass activity. Therefore, we prepared mesoporous nanofibers of various cation-ordered PrBa0.5Sr0.5Co2-xFexO5+δ (x = 0, 0.5, 1, 1.5, and 2) perovskites via electrospinning. The well-controlled B-site metal ratio and large surface area (∼20 m2 g-1) of mesoporous nanofiber result in high performance of the oxygen reduction reaction and oxygen evolution reaction and stability in zinc-air battery.

Electrospun Iron-Based Fibers for Use in MEMS Sensors

This letter reports on the characterization of iron containing nanofibers using a polyvinyl alcohol (PVA)-based solution in a batch electrospinning processing method. Variation of iron content within the pre-fiber solution, and characterization of fiber size and porosity are important for the use of these nanomaterials in sensing. Simulated non-porous fibers are compared with nanofibers obtained utilizing this method. Pre-calcination (thermal) fibers had diameters of 243 nm on average with a standard deviation of ±43 nm and a standard error of ±4.53 nm. Fabrication of mesoporous iron-based nanofibers was achieved after the calcination of the iron/PVA fibers. With the calcination process, we produced fibers with 32-nm diameters, and a standard deviation of ±12 nm and a standard error of ±1.41 nm. The error between model and experimental results is 37.5% for producing Fe3O4 fibers. This error percentage and oversized dimensions suggest near total conversion to Fe3O4 occurring due to calcination as well as creating mesoporous fibers. [2017-0014]

Formation of Core‐Shell Mesoporous Ceramic Fibers

AbstractCeramic Fe–Al–O nanofibers with a core‐shell architecture were obtained by electrospinning. The fibers consist of an Fe–Al–O core with novel lamellar‐like mesopores and an Fe‐rich shell. A mechanism of this unique core and shell formation is outlined and confirmed. The described mesoporous nanofibers are highly promising for new research and applications involving catalysis, sensing and absorption of mobile components on the accessible porous core surface.

Fabrication of PdOx loaded highly mesoporous WO3/TiO2 hybrid nanofibers by stepwise pore-generation for enhanced photocatalytic performance

Highly mesoporous WO3/TiO2 nanofibers were fabricated through the combination of an advanced electrospinning strategy in the presence of porogenic agent and the subsequent heat treatment. It was found that the introduced porogenic agent of diisopropyl azodiformate (DIAD) within the precursor solution plays a crucial role on the formation of highly mesoporous WO3/TiO2 nanofibers, enabling their mesopores tunable. The obtained mesoporous nanofibers from the stepwise decomposition of DIAD and polymer skeleton possess more homogeneous and smaller pore sizes in their morphology and thus a higher surface area than that obtained without porogenic agent. The highest surface area can reach 92.3m2g−1, which is ca. 5 times larger than that of the pure TiO2 nanofibers obtained without DIAD addition. These highly mesoporous WO3/TiO2 nanofibers were further modified by PdOx nanoparticles via photodeposition. The as-fabricated mesoporous PdOx/WO3/TiO2 hybrid nanofibers exhibit excellent photocatalytic activity and significant stability towards acetaldehyde decomposition compared to the conventional nanofibers under visible light and UV–vis light irradiation. The present work suggests a facile preparation of PdOx loaded mesoporous WO3/TiO2 nanofibers, which may provide new solution to prepare the inorganic nanofibers with highly mesoporous structure.

Mesoporous Ag@TiO2 nanofibers and their photocatalytic activity for hydrogen evolution

We reported the exploration of Ag@TiO2 mesoporous nanofibers with significantly improved photocatalytic performance.

Single-Handed Helical Polybissilsesquioxane Nanotubes and Mesoporous Nanofibers Prepared by an External Templating Approach Using Low-Molecular-Weight Gelators.

Chiral low-molecular-weight gelators (LMWGs) derived from amino acids can self-assemble into helical fibers and twisted/coiled nanoribbons by H-bonding and π–π interaction. Silica nanotubes with single-handed helices have been prepared using chiral LMWGs through sol–gel transcription. Molecular-scale chirality exists at the inner surfaces. Here, we discuss single-handed helical aromatic ring-bridged polybissilsesquioxane nanotubes and mesoporous nanofibers prepared using chiral LMWGs. This review aims at describing the formation mechanisms of the helical nanostructures, the origination of optical activity, and the applications for other helical nanomaterial preparation, mainly based on our group’s results. The morphology and handedness can be controlled by changing the chirality and kinds of LMWGs and tuning the reaction conditions. The aromatic rings arrange in a partially crystalline structure. The optical activity of the polybissilsesquioxane nanotubes and mesoporous nanofibers originates from chiral defects, including stacking and twisting of aromatic groups, on the inner surfaces. They can be used as the starting materials for preparation of silica, silicon, carbonaceous, silica/carbon, and silicon carbide nanotubes.

Enhanced visible-light responsive photocatalytic activity of N-doped TiO2 thoroughly mesoporous nanofibers

Improving the photocatalytic efficiency of TiO2 semiconductor is crucially important and highly desired for its practical applications. In the present work, aiming to broaden the photoresponse window and limit the photocatalyst aggregation, we reported the exploration of N-doped TiO2 thoroughly mesoporous nanofibers with high purity in morphology via a foaming-assisted electrospinning strategy. The foaming agents and urea were introduced in the raw materials to create the mesopores and incorporate the N dopants into the conventional solid TiO2 nanofibers, respectively, which could be accomplished simultaneously over one-step calcination process. The synergetic combination of N dopants and one-dimensional mesoporous nanostructure allow the TiO2 fibers to exhibit significantly enhanced visible-light photocatalytic activity toward the Rhodamine B and hydrogen evolution, as compared to those of N-doped solid and intrinsic thoroughly mesoporous counterparts, suggesting their promising applications in water purification and energy supply.

Highly Efficient Photocatalytic Hydrogen Evolution in Ternary Hybrid TiO2/CuO/Cu Thoroughly Mesoporous Nanofibers.

Development of novel hybrid photocatalysts with high efficiency and durability for photocatalytic hydrogen generation is highly desired but still remains a grand challenge currently. In the present work, we reported the exploration of ternary hybrid TiO2/CuO/Cu thoroughly mesoporous nanofibers via a foaming-assisted electrospinning technique. It is found that by adjusting the Cu contents in the solutions, the unitary (TiO2), binary (TiO2/CuO, TiO2/Cu), and ternary (TiO2/CuO/Cu) mesoporous products can be obtained, enabling the growth of TiO2/CuO/Cu ternary hybrids in a tailored manner. The photocatalytic behavior of the as-synthesized products as well as P25 was evaluated in terms of their hydrogen evolution efficiency for the photodecomposition water under Xe lamp irradiation. The results showed that the ternary TiO2/CuO/Cu thoroughly mesoporous nanofibers exhibit a robust stability and the most efficient photocatalytic H2 evolution with the highest release rate of ∼851.3 μmol g(-1) h(-1), which was profoundly enhanced for more than 3.5 times with respect to those of the pristine TiO2 counterparts and commercial P25, suggesting their promising applications in clean energy production.

Hierarchical ZSM-5 by 90° twin intergrowth of mesoporous nanofibers: Synthesis and application in methanol/propanal to hydrocarbon reaction

Hierarchical ZSM-5 with tri-modal porosity was prepared and tested in methanol/propanal to hydrocarbon reaction. 90° twin intergrowth of ZSM-5 nanofibers (TIZSM-5) was successfully synthesized with a simple organic, 1,6-bis(methylpiperidinium)hexyl dibromide, as single template. Such TIZSM-5 has a large crystal size (10 μm × 10 μm), open macropore system, and uniform Al distribution. Smaller mesopore with size around 10 nm was then introduced into TIZSM-5 through simple desilication. The resulting hierarchical ZSM-5 is characterized by inter-connected and tri-modal porosity throughout the crystal. Catalyst evaluation indicated the prepared hierarchical ZSM-5 shows excellent catalytic performance in methanol/propanal to hydrocarbon reaction. The catalyst lifetime was 60% longer when compared to the state of art mesoporous ZSM-5 prepared from 8014 by desilication in MTH reaction.

Freestanding hematite nanofiber membrane for visible-light-responsive photocatalyst

Freestanding mesoporous hematite (α-Fe2O3) nanofiber membranes were successfully fabricated by sol–gel electrospinning process using ferratrane precursor for use as a high-performance material for visible-light-responsive photocatalyst. Non-porous nanofiber membranes spun on the heated collector at 300°C were crystalline α-Fe2O3 phase. Upon calcination, pure mesoporous nanofiber membranes were obtained even at a low temperature of 400°C. The photocatalytic membrane calcined at 400°C showed the highest efficiency for methylene blue (MB) degradation under visible-light irradiation. The synergetic effects of higher surface area, pore volume and pore diameter promoted the photocatalytic efficiency for MB degradation under visible light. The utilization of photocatalyst in the form of membrane could not only solve the problems of catalyst separation and recovery, but also produce high photodegradation efficiency for both systems without and with hydrogen peroxide even at a catalyst loading as low as 0.04g/L. No appreciable loss in photocatalytic activity was observed and structural integrity was retained, even after five cycles of photodegradation, which predicted the stability and reusability of these nanofiber membranes for practical use in environmental applications.

Mesoporous Carbon Nanofibers Embedded with MoS2 Nanocrystals for Extraordinary Li-Ion Storage.

MoS2 nanocrystals embedded in mesoporous carbon nanofibers are synthesized through an electrospinning process followed by calcination. The resultant nanofibers are 100-150 nm in diameter and constructed from MoS2 nanocrystals with a lateral diameter of around 7 nm with specific surface areas of 135.9 m(2) g(-1) . The MoS2 @C nanofibers are treated at 450 °C in H2 and comparison samples annealed at 800 °C in N2 . The heat treatments are designed to achieve good crystallinity and desired mesoporous microstructure, resulting in enhanced electrochemical performance. The small amount of oxygen in the nanofibers annealed in H2 contributes to obtaining a lower internal resistance, and thus, improving the conductivity. The results show that the nanofibers obtained at 450 °C in H2 deliver an extraordinary capacity of 1022 mA h g(-1) and improved cyclic stability, with only 2.3 % capacity loss after 165 cycles at a current density of 100 mA g(-1) , as well as an outstanding rate capability. The greatly improved kinetics and cycling stability of the mesoporous MoS2 @C nanofibers can be attributed to the crosslinked conductive carbon nanofibers, the large specific surface area, the good crystallinity of MoS2 , and the robust mesoporous microstructure. The resulting nanofiber electrodes, with short mass- and charge-transport pathways, improved electrical conductivity, and large contact area exposed to electrolyte, permitting fast diffusional flux of Li ions, explains the improved kinetics of the interfacial charge-transfer reaction and the diffusivity of the MoS2 @C mesoporous nanofibers. It is believed that the integration of MoS2 nanocrystals and mesoporous carbon nanofibers may have a synergistic effect, giving a promising anode, and widening the applicability range into high performance and mass production in the Li-ion battery market.