Nanofiber Template Research Articles

Large-scale conformal synthesis of one-dimensional MAX phases

MAX phases, a unique class of layered ternary compounds, along with their two-dimensional derivatives, MXenes, have drawn considerable attention in many fields. Notably, their one-dimensional (1D) counterpart exhibits more distinct properties and enhanced assemblability for broader applications. We propose a conformal synthetic route for 1D-MAX phases fabrication by integrating additional atoms into nanofibers template within a molten salt environment, enabling in-situ crystalline transformation. Several 1D-MAX phases are successfully synthesized on a large scale. Demonstrating its potential, a copper-based layer-by-layer composites containing 1% by volume of 1D-Ti2AlC reinforced phase achieves an impressive 98 IACS% conductivity and a friction coefficient of 0.08, while maintaining mechanical properties comparable to other Cu-MAX phase composites, making it suitable for advanced industrial areas. This strategy may promise opportunities for the fabrication of various 1D-MAX phases.

Constructing multifunctional polyvinyl alcohol composite hydrogels with human-like skin properties using polyaniline-coated boron nitride nanofibers

Flexible conductive nanofibers play a crucial role in constructing hydrogels with human-like skin properties. However, it is still a challenge to construct flexible conductive nanofibers with good comprehensive properties. In this paper, we prepare composite fibers with excellent comprehensive properties by coating polyaniline (PANI) on the surface of flexible boron nitride nanofiber (BNNFs) template. BNNFs-PANI/PVA multifunctional composite hydrogels are created through the integration of BNNFs-PANI as nanofillers with soft poly (vinyl alcohol) (PVA) matrix using a one-pot self-assembly method. The composite hydrogels exhibit outstanding plasticity, self-adhesion, and self-healing properties, with a self-healing efficiency reaching up to 96% within 120 s. Furthermore, the tensile strength of the composite hydrogels has been enhanced by 36%, with the elongation at break exceeding 1500%. The compressive strength of the composite hydrogels at 60% strain is increased by 62%. Beyond these mechanical and self-healing features similar to human skin, the composite hydrogels also can serve as electronic pen for painting on a touchable electronic screen, simulating the function of human skin. Moreover, the dynamic changes in the abundant conductive network contribute to the composite hydrogels’ high strain sensitivity. Compared with pure PVA hydrogels, it is improved by 29%. Notably, the strain sensitivity of the composite hydrogels is higher than that of most reported hydrogel sensors. Therefore, the composite hydrogels also can be employed as a real-time human motion sensor, capable of detecting and distinguishing various human movements. We believe that employing BNNFs as templates for crafting highly flexible and conductive nanofibers will foster the advancement of flexible conductive nanomaterials with comprehensive properties. Furthermore, the outstanding properties of the prepared composite hydrogels contribute to the ongoing development of conductive hydrogels with skin-like functionalities.

(Poster Award - 3rd Place) Photocatalysis of TiO2 Nanosheets Prepared by the Cellulose Nanofiber Template

Two-dimensional material inspired tremendous research interest by its unique structure and specific property different from bulk material, which could benefit various applications such as optics, electronics, and chemistry. However, most documented processes for 2D materials are complicated with a lengthy process. We introduced the cellulose nanofiber (CNF) extracted from agricultural waste rice straws, which inherently possesses many functional groups, e.g., hydroxyl group, and carboxylate group, making it a terrific template method candidate. Besides, aerogel composed of cellulose nanofiber provides many surface and layered structures that facilitate the adhesion of titanium isopropoxide to form a uniform coating layer, which hydrolyzed to TiO2. The cellulose nanofiber serves as a template and could be removed entirely in an easy thermal process by thermogravimetric analysis; meanwhile, we can transform the original amorphous TiO2 nanosheet into an anatase phase which is flavored in the photocatalyst field. Atomic force microscopy (AFM) results spotted a stacked ultrathin TiO2 nanosheet with a thickness of less than 5 nm for each layer, and the lateral size could reach micron size. For the RhB dye degradation test, TiO2 nanosheets could decompose the 10 ppm RhB solution within 30 mins with a reaction rate of 0.065 min-1. In conclusion, we combine the CNF template and hydrolysis process, proposing a simple 2D TiO2 nanosheets

High-entropy (FeCoNiCuZn)WO4 photocatalysts-based fibrous membrane for efficient capturing and upcycling of plastic

Catalytic upcycling of plastics is regarded as a promising way to alleviate environmental pollution and produce value-added products, while still facing huge challenges. Herein, we report a feasible strategy for synthesizing high-entropy photocatalysts-based fibrous membranes with a dual function of capturing and upcycling plastic. Polyacrylonitrile (PAN) nanofibers templates enable the growth of highly arranged high-entropy metal tungstates (FeCoNiCuZn)WO4, denoted XWO4. The effect of lattice distortion in XWO4 modulates the band gap structure and contributes to the upshift d-band center of XWO4. As a result, the modified anti-bonding state facilitates the upcycling of captured polylactic acid (PLA) towards acetic acid production, with an enhanced yield rate of 38.51 mg gcat.−1 h−1 and improved selectivity of 73 %. Thus, the developed NFs template strategy, a tunable electronic structure and exploration of the structure–function relationship provide insight into tailoring the structure and composition of HEMs for photocatalytic upcycling of plastic.

Directional assembly of multi-catalytic sites CoCu-MOFs with porous carbon nanofiber templates as efficient catalyst for microbial fuel cells

Designing catalysts with multi catalytic sites is considered as a promising way to solve the sluggish kinetics of the cathodic oxygen reduction reaction (ORR) and improve the performance of electricity generation in microbial fuel cells (MFCs). In this work, a novel hybrid porous electrocatalyst derived from metal-organic frameworks (MOFs) is successfully synthesized, which combines graphene-carbon coated CoCu alloy nanoparticles grown in vertical alignment on carbon nanofibers (CoCu@N-CNFs). Apart from this, CoCu@N-CNFs containing both Co-Nx and Cu-Nx coordination environments enhance oxophilicity, thereby boosting the intrinsic activity of ORR. As expected, CoCu@N-CNFs-1:1 exhibits a superior ORR half-wave potential (−0.545 V vs. Hg/HgCl2) and high limiting current density (10.09 mA cm−2), exceeding that of 20% Pt/C. Furthermore, the MFC equipped with CoCu@N-CNFs-1:1 catalyst achieves maximum power density and coulomb efficiency, which are 102% and 112% higher than Pt/C, respectively. Moreover, CoCu@N-CNFs-1:1 possesses high antibacterial capacity, inhibiting the biofouling on the cathode surface, which further ensures the effective and continuous occurrence of ORR at the triple-phase interface of MFCs.

Enhanced Electrochemical Performance in Ge/GeO2 Nanotubes Anode Derived from C/Ge Nanofibers

Hollow discontinuous Ge/GeO2 nanotubes are successfully prepared after the facile oxidization process in air, which are derived from the C/Ge core–shell nanofibers. Electrospinning and chemical vapor deposition techniques are used to fabricate the carbon nanofiber templates and the Ge shell electrode, respectively. Compared with the C/Ge nanocomposites, the Ge/GeO2 nanotube anode demonstrates improved electrochemical performance due to the enlarged surface area and enough space, which can effectively retard the Ge electrode large volume change during repeated cycling. Full‐battery Ge/GeO2||LiCoO2 is also configured and displays good Li‐ion storage ability.

Flow-through working electrode based on free-standing porous boron-doped diamond

Free-standing porous boron-doped diamond (fs-pBDD) was successfully fabricated and employed as a flow-through working electrode in flow injection analysis (FIA) experiments for the first time. fs-pBDD was fabricated by microwave plasma enhanced chemical vapour deposition growth of BDD on a SiO2 nanofiber template spin coated onto a silicon substrate in a multistep process, before being released by wet chemical etching of the silicon substrate. By means of cyclic voltammetry, the effective surface area of the fs-pBDD electrode was estimated to be 30.1 mm2. Fundamental performance parameters of the fs-pBDD electrode in an FIA system were determined utilising [Ru(NH3)6]3+/2+ redox probe. A detection potential of −0.3 V and the flow rate of 1.0 mL min−1 were selected as optimal and were further employed for recording concentration dependence, which was linear from 5 µmol L−1 to 750 µmol L−1. Limits of detection and quantification were assessed as 1.6 µmol L−1 and 5.3 µmol L−1, respectively. The obtained results thus proved functionality of the developed fs-pBDD as a perspective electrode material for use as an electrochemical detector for liquid-flow techniques.

Pt-decorated NiWO4/WO3 heterostructure nanotubes for highly selective sensing of acetone

The heterostructured NiWO4/WO3 nanotubes (Ni/W NTs) were synthesized by using a facile self-assembly method on the sacrificial polystyrene (PS) nanofibers templates. Then, the Pt-decorated NiWO4/WO3 (Pt@Ni/W) composite NTs were obtained through using an ultrasonic mixing method. The experimental results display that the order of gas-sensing performance is Pt@Ni/W>Ni/W>WO3. The 2wt.%Pt@Ni/W-5 NTs indicate the supreme acetone-sensing response (Rair/Rgas=58.4 at 100×10−6) at 375 °C, which is 10.6 and 1.53 times that of the WO3 and NiWO4/WO3 NTs, respectively. Additionally, the 2wt.%Pt@Ni/W-5 NTs also exhibit the dramatically high selectivity toward acetone against ethanol, methanal, methanol, NH3 and toluene. The Pt-decorated Ni/W NTs show the excellent responsivity and stability toward acetone, which is ascribed to the construction of heterostructured NiWO4/WO3 and the spill-over effect of Pt nanoparticles.

High-Performance IGZO Nanowire-Based Field-Effect Transistors with Random-Network Channels by Electrospun PVP Nanofiber Template Transfer.

A random network of indium–gallium–zinc oxide (IGZO) nanowires was fabricated by electrospun-polyvinylpyrrolidone (PVP)-nanofiber template transfer. Conventional electrospun nanofibers have been extensively studied owing to their flexibility and inherently high surface-to-volume ratio. However, solution-based IGZO nanofibers have critical issues such as poor electrical properties, reliability, and uniformity. Furthermore, high-temperature calcination, which is essential for vaporizing the polymer matrix, hinders their applications for flexible electronics. Therefore, sputter-based IGZO nanowires were obtained in this study using electrospun PVP nanofibers as an etching mask to overcome the limitations of conventional electrospun IGZO nanofibers. Field-effect transistors (FETs) were fabricated using two types of channels, that is, the nanofiber template-transferred IGZO nanowires and electrospun IGZO nanofibers. A comparison of the transmittance, adhesion, electrical properties, reliability, and uniformity of these two channels in operation revealed that the nanofiber template-transferred IGZO nanowire FETs demonstrated higher transmittance, stronger substrate adhesion, superior electrical performance, and operational reliability and uniformity compared to the electrospun IGZO nanofiber FETs. The proposed IGZO nanowires fabricated by PVP nanofiber template transfer are expected to be a promising channel structure that overcomes the limitations of conventional electrospun IGZO nanofibers.

Electrospun Amphiphilic Nanofibers as Templates for In Situ Preparation of Chloramphenicol-Loaded Liposomes.

The hydration of phospholipids, electrospun into polymeric nanofibers and used as templates for liposome formation, offers pharmaceutical advantages as it avoids the storage of liposomes as aqueous dispersions. The objective of the present study was to electrospin and characterize amphiphilic nanofibers as templates for the preparation of antibiotic-loaded liposomes and compare this method with the conventional film-hydration method followed by extrusion. The comparison was based on particle size, encapsulation efficiency and drug-release behavior. Chloramphenicol (CAM) was used at different concentrations as a model antibacterial drug. Phosphatidylcoline (PC) with polyvinylpyrrolidone (PVP), using ethanol as a solvent, was found to be successful in fabricating the amphiphilic composite drug-loaded nanofibers as well as liposomes with both methods. The characterization of the nanofiber templates revealed that fiber diameter did not affect the liposome size. According to the optical microscopy results, the immediate hydration of phospholipids deposited on the amphiphilic nanofibers occurred within a few seconds, resulting in the formation of liposomes in water dispersions. The liposomes appeared to aggregate more readily in the concentrated than in the diluted solutions. The drug encapsulation efficiency for the fiber-hydrated liposomes varied between 14.9 and 28.1% and, for film-hydrated liposomes, between 22.0 and 77.1%, depending on the CAM concentrations and additional extrusion steps. The nanofiber hydration method was faster, as less steps were required for the in-situ liposome preparation than in the film-hydration method. The liposomes obtained using nanofiber hydration were smaller and more homogeneous than the conventional liposomes, but less drug was encapsulated.

Perylenediimide/silver nanohybrids with visible-light photocatalysis enhanced antibacterial effect

Bacterial infections cause severe threats to human health. Silver nanoparticles (AgNPs) are promising antibacterial materials, but still confront poor colloidal stability and uncontrollable silver ion (Ag+) release. Here, a dye template strategy based on tunable perylenediimide (PDI) self-assembly is presented for constructing novel silver nanohybrids with visible-light photocatalysis enhanced antibacterial effect. Ultrasmall AgNPs are grown on diversiform topological PDI self-assembly-templates via in situ reduction to yield silver nanohybrids, achieving stable AgNPs dispersion. The developed fiber-like nanohybrids (BF@AgNPs) are endowed with photocatalytic ability by PDI nanofiber templates. Upon visible-light irradiation, BF@AgNPs generate reactive oxygen species via photocatalytic reaction, facilitating the AgNPs degradation to release Ag+ and concurrently exerting photocatalytic damage to bacteria. Consequently, the visible-light photocatalysis enhanced antibacterial effect of BF@AgNPs against Staphylococcus aureus and Escherichia coli is achieved via synergetic Ag+ release and photocatalytic performance. This work not only provides a versatile molecular assembly strategy for developing new powerful antibacterial materials, but also opens up a new way for dye functionalization.

Importance of Substrate-Particle Repulsion for Protein-Templated Assembly of Metal Nanoparticles.

We study the protein-directed assembly of colloidal gold nanoparticles on de novo designed protein nanofiber templates. Using sequential assembly on glass substrates, we attach positively charged gold nanoparticles to protein nanofibers engineered to have a high density of negatively charged surface residues. Using a combination of electron and optical microscopy, we measure the density of particle attachment and characterize binding specificity. By varying nanoparticle size and pH of the solution, we explore the importance of charge-dependent particle-fiber and particle-substrate interactions. We find an inverse correlation between particle size and attachment density to protein nanofibers, attributed to the balance between size-dependent electrostatic particle-fiber attraction and particle-substrate repulsion. We show pH-dependent particle attachment density and binding specificity in relation to the protonation fraction of each assembly layer. Finally, we employ hyperspectral scattering microscopy to draw conclusions about particle density and interparticle spacings of optically observable particle assemblies.

Electrohydrodynamic Processing of PVP-Doped Kraft Lignin Micro- and Nano-Structures and Application of Electrospun Nanofiber Templates to Produce Oleogels

The present work focuses on the development of lignin micro- and nano-structures obtained by means of electrohydrodynamic techniques aimed to be potentially applicable as thickening or structuring agents in vegetable oils. The micro- and nano-structures used were mainly composed of eucalyptus kraft lignin (EKL), which were doped to some extent with polyvinylpyrrolidone (PVP). EKL/PVP solutions were prepared at different concentrations (10–40 wt.%) and EKL:PVP ratios (95:5–100:0) in N, N-dimethylformamide (DMF) and further physico-chemically and rheologically characterized. Electrosprayed micro-sized particles were obtained from solutions with low EKL/PVP concentrations (10 and 20 wt.%) and/or high EKL:PVP ratios, whereas beaded nanofiber mats were produced by increasing the solution concentration and/or decreasing EKL:PVP ratio, as a consequence of improved extensional viscoelastic properties. EKL/PVP electrospun nanofibers were able to form oleogels by simply dispersing them into castor oil at nanofiber concentrations higher than 15 wt.%. The rheological properties of these oleogels were assessed by means of small-amplitude oscillatory shear (SAOS) and viscous flow tests. The values of SAOS functions and viscosity depended on both the nanofiber concentration and the morphology of nanofiber templates and resemble those exhibited by commercial lubricating greases made from traditional metallic soaps and mineral oils.

One-Pot Synthesis of Sulfonated Carbon/Palygorskite Solid-Acid Catalyst for the Esterification of Oleic Acid with Methanol

AbstractSulfonated carbon is a ‘green,’ solid-acid catalyst. For applications purposes, its surface area needs to be improved and its preparation needs to be made environmentally friendly. The objective of the present study was to provide a green and economical method of preparing a sulfonated carbon catalyst by using palygorskite (Plg) fiber as a support for sulfonated carbon. Sulfonated carbon/palygorskite solid-acid catalyst (SC-Plg) was synthesized via one-step carbonization-sulfonation by mixing palygorskite with sucrose as the carbon source and p-toluenesulfonic acid as the sulfonating agent. The catalyst was characterized by SEM, EDX, TEM, FTIR, and nitrogen adsorption-desorption isotherms. The results indicated that sucrose-derived carbon was loaded uniformly on the surface of Plg fibers and formed the SC-Plg catalyst. The inexpensive Plg fibers could replace sucrose-derived carbon and increase the surface area of the resulting catalyst. The SC-Plg shows significant catalytic performance and excellent stability when used in the esterification of oleic acid with methanol. The conversion of oleic acid reached 68.09%, even after five cycles. This work paves the way for the development of highly active, carbon-based, solid-acid composite catalysts using a natural Plg nanofiber template.

Preparation of CoB nanoparticles decorated PANI nanotubes as catalysts for hydrogen generation from NaBH4 hydrolysis

Magnetic agglomeration of CoB nanoparticles in the hydrogen production from the hydrolysis of NaBH4 aqueous solution always degrades their catalytic activity. This work aims at the rational development of robust supported CoB catalyst that is active and stable towards NaBH4 hydrolysis. In this study, PANI nanotubes derived from PS nanofiber templates are firstly synthesized by the polymerization of aniline followed by the template removal. CoB nanoparticles are then decorated into PANI nanotubes via an impregnation and chemical reduction method. It can be found that CoB nanoparticles can be confined into the internal surface of PANI nanotubes which improves the dispersion and anchored stability of CoB nanoparticles. The as-prepared CoB/PANI composite catalyst exhibits a high catalytic performance and recycling stability. The hydrogen production rate as high as 2300 ml. min−1. g − 1 is achieved and the activation energy was calculated to be only 37.75 kJ/mol. Meanwhile, CoB/PANI catalyst displays excellent stability in NaBH4 hydrolysis during five cycles. The experimental results indicated that as-synthesized CoB/PANI composite catalysts are very efficient towards hydrogen production from NaBH4 hydrolysis.

Bacterial Cellulose Network from Kombucha Fermentation Impregnated with Emulsion-Polymerized Poly(methyl methacrylate) to Form Nanocomposite.

The use of bio-based residues is one of the key indicators towards sustainable development goals. In this work, bacterial cellulose, a residue from the fermentation of kombucha tea, was tested as a reinforcing nanofiber network in an emulsion-polymerized poly(methyl methacrylate) (PMMA) matrix. The use of the nanofiber network is facilitating the formation of nanocomposites with well-dispersed nanofibers without using organic solvents or expensive methodologies. Moreover, the bacterial cellulose network structure can serve as a template for the emulsion polymerization of PMMA. The morphology, size, crystallinity, water uptake, and mechanical properties of the kombucha bacterial cellulose (KBC) network were studied. The results showed that KBC nanofibril diameters were ranging between 20–40 nm and the KBC was highly crystalline, >90%. The 3D network was lightweight and porous material, having a density of only 0.014 g/cm3. Furthermore, the compressed KBC network had very good mechanical properties, the E-modulus was 8 GPa, and the tensile strength was 172 MPa. The prepared nanocomposites with a KBC concentration of 8 wt.% were translucent with uniform structure confirmed with scanning electron microscopy study, and furthermore, the KBC network was homogeneously impregnated with the PMMA matrix. The mechanical testing of the nanocomposite showed high stiffness compared to the neat PMMA. A simple simulation of the tensile strength was used to understand the limited strain and strength given by the bacterial cellulose network. The excellent properties of the final material demonstrate the capability of a residue of kombucha fermentation as an excellent nanofiber template for use in polymer nanocomposites.

A Facile Strategy for Fabrication Lysozyme-Loaded Mesoporous Silica Nanotubes from Electrospun Silk Fibroin Nanofiber Templates.

This paper presents a facile and low-cost strategy for fabrication lysozyme-loaded mesoporous silica nanotubes (MSNTs) by using silk fibroin (SF) nanofiber templates. The “top-down method” was adopted to dissolve degummed silk in CaCl2/ formic acid (FA) solvent, and the solution containing SF nanofibrils was used for electrospinning to prepare SF nanofiber templates. As SF contains a large number of -OH, -NH2 and -COOH groups, the silica layer could be easily formed on its surface by the Söber sol-gel method without adding any surfactant or coupling agent. After calcination, the MSNTs were obtained with inner diameters about 200 nm, the wall thickness ranges from 37 ± 2 nm to 66 ± 3 nm and the Brunauer–Emmett–Teller (BET) specific surface area was up to 200.48 m2/g, the pore volume was 1.109 cm3/g. By loading lysozyme, the MSNTs exhibited relatively high drug encapsulation efficiency up to 31.82% and an excellent long-term sustained release in 360 h (15 days). These results suggest that the MSNTs with the hierarchical structure of mesoporous and macroporous will be a promising carrier for applications in biomacromolecular drug delivery systems.

Alignment of Au nanorods along de novo designed protein nanofibers studied with automated image analysis.

In this study, we focus on exploring the directional assembly of anisotropic Au nanorods along de novo designed 1D protein nanofiber templates. Using machine learning and automated image processing, we analyze scanning electron microscopy (SEM) images to study how the attachment density and alignment fidelity are influenced by variables such as the aspect ratio of the Au nanorods, and the salt concentration of the solution. We find that the Au nanorods prefer to align parallel to the protein nanofibers. This preference decreases with increasing salt concentration, but is only weakly sensitive to the nanorod aspect ratio. While the overall specific Au nanorod attachment density to the protein fibers increases with increasing solution ionic strength, this increase is dominated primarily by non-specific binding to the substrate background, and we find that greater specific attachment (nanorods attached to the nanofiber template as compared to the substrates) occurs at the lower studied salt concentrations, with the maximum ratio of specific to non-specific binding occurring when the protein fiber solutions are prepared in 75 mM NaCl concentration.

Synthesis of silver nanofiber transparent electrodes by silver mirror reaction with electrospun nanofiber template

ABSTRACT Electrospinning and silver mirror reaction (SMR) were combined to synthesize silver nanowire membrane. The best sheet resistance (Rs) and transmittance (T) values reach around 15 Ω/sq and 80% on PET, 37 Ω/sq and 81% on glass, respectively. In this method, Poly(acrylonitrile – co – phenylethylene) (P(AN-S)) nanofibers act as the templates and reduction of silver on the nanofibers surface act as seeds. In SMR process, silver deposited on the surface of nanofibers and developed into silver nanowires. The membrane was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The effects of spinning parameters and silver mirror reaction time on membrane properties were investigated. This process is easily controlled and it takes place at ambient condition, which gives a new opportunity for transparent conducting flexible electronics.

Hollow “graphene” microtubes using polyacrylonitrile nanofiber template and potential applications of field emission

We report a simple process to connect graphene sheets forming graphene hollow microtubes (GHMs), where the tube diameter can be adjusted in the 100–500 nm range by changing reaction conditions. We discovered that graphene sheets can be seamlessly linked to each other if C atoms are substituted for N atoms at the edges of the sheets during annealing of graphene oxide(G-O)-coated electrospun PAN carbon fibers in ammonia atmosphere. The G-O/carbon hybrid nanofibers framework served as a confining template around which graphene sheets curved to form tubular structures. The GHMs formed by this process are similar to (very) large diameter carbon nanotubes (CNTs) with relatively low curvature whose electron field-emission properties include a low turn-on voltage of 0.18 V/μm (at J = 10 μA/cm2), low threshold field of 0.35 V/μm (at J = 10 mA/cm2), and high field-emission stability. This process to produce GHMs can be scaled up to fabricate GHMs of variable diameter in bulk quantities.