Silica Nanofibers Research Articles

Silica nanofiber membrane with high reflectivity and low absorptivity for high-energy laser protection (29.0 kW/cm2)

To safeguard against high-energy continuous wave laser, the chosen strategy is a robust reflection to restrict heat generation instead of thermal protection. Based on this, the SiO2 nanofiber membranes (0.12 g/cm3) with nearly 100% reflectivity and an extremely low absorption coefficient, were fabricated by electrospinning under the optimal parameters and calcinating at 600-1000 °C. The membranes, with a thickness of 4 mm, exhibit the best laser protection property reported to date. Under laser irradiation of 29.0 kW/cm2, they remain intact and achieve a steady state after 10 s with a rear temperature of only 700 °C because the necessary conditions for excellent laser protection property—the absence of highly absorbing groups, moderate fiber stacking density, presence of fiber stacking structure, chemical inertness, and specific thickness—are all met. In addition, excellent mechanical properties, including a tensile strength of 16.6 MPa (normalized value through equivalent solid materials for comparison purposes), a compressive strength of 0.07 MPa, and good bending performance, provide guarantees for their practical applications.

Fabrication of single-ion conductive quasi-solid-state electrolyte membrane for high-performance lithium-ion batteries

The aim of this work is to develop new quasi-solid-state electrolyte materials for lithium-ion batteries (LIBs) to improve their safety and comprehensive electrochemical performance. Herein, helical mesoporous silica nanofibers were synthesized by a sol–gel method. After grafting lithium salt onto their surfaces, a single-ion conductor (SL) was obtained. Then, using poly(vinylidene fluoride-co-hexafluoropropylene) as the polymer matrix, SL as the filler, a porous composite film was prepared by solution casting method. After soaking organic electrolyte with low concentration Li salt till saturation, one quasi-solid-state electrolyte membrane (PSLE) was achieved. It showed high electrolyte adsorption rate of 660 % and good thermal stability. A high lithium-ion transfer number of 0.85 indicated typical single-ion conductivity. Moreover, a high electrochemical stability window of up to 5.5 V and an ionic conductivity of 2.5 × 10−3 S·cm−1 at 25 °C were gained. The assembled LFP|PSLE|Li battery exhibited excellent rate performance and cycle stability, indicating that the PSLE has great application prospect in solid-state LIBs.

Randomizing the growth of silica nanofibers for whiteness

In colloids, the shape influences the function. In silica, straight nanorods have already been synthesized from water-in-oil emulsions. By contrast, curly silica nanofibers have been less reported because the underlying growth mechanism remains unexplored, hindering further morphology control for applications. Herein, we describe the synthetic protocol for silica nanofibers with a tunable curliness based on the control of the water-in-oil emulsion droplets. Systematically decreasing the droplet size and increasing their contact angle, the Brownian motion of the droplets intensifies during the silica growth, thus increasing the random curliness of the nanofibers. This finding is supported by simplistic theoretical arguments and experimentally verified by varying the temperature to finely tune the curliness. Assembling these nanofibers toward porous disordered films enhances multiple scattering in the visible range, resulting in increased whiteness in contrast to films constructed by spherical and rod-like building units, which can be useful for, e.g., coatings and pigments.

MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

HighlightsThe SiO2 nanofiber membranes and MXene@c-MWCNT6:4 as one unit layer (SMC1) were bonded together with 5 wt% PVA solution.When the structural unit is increased to three layers, the resulting SMC3 has an average electromagnetic interference SET of 55.4 dB and a low thermal conductivity of 0.062 W m−1 K−1.SMCx exhibit stable electromagnetic interference shielding and excellent thermal insulation even in extreme heat and cold environment.

Synthetic silica fibers of different length, diameter and shape: synthesis and interaction with rat (NR8383) and human (THP-1) macrophages in vitro, including chemotaxis and gene expression profile

BackgroundInhalation of biopersistent fibers like asbestos can cause strong chronic inflammatory effects, often resulting in fibrosis or even cancer. The interplay between fiber shape, fiber size and the resulting biological effects is still poorly understood due to the lack of reference materials.ResultsWe investigated how length, diameter, aspect ratio, and shape of synthetic silica fibers influence inflammatory effects at doses up to 250 µg cm-2. Silica nanofibers were prepared with different diameter and shape. Straight (length ca. 6 to 8 µm, thickness ca. 0.25 to 0.35 µm, aspect ratio ca. 17:1 to 32:1) and curly fibers (length ca. 9 µm, thickness ca. 0.13 µm, radius of curvature ca. 0.5 µm, aspect ratio ca. 70:1) were dispersed in water with no apparent change in the fiber shape during up to 28 days. Upon immersion in aqueous saline (DPBS), the fibers released about 5 wt% silica after 7 days irrespectively of their shape. The uptake of the fibers by macrophages (human THP-1 and rat NR8383) was studied by scanning electron microscopy and confocal laser scanning microscopy. Some fibers were completely taken up whereas others were only partially internalized, leading to visual damage of the cell wall. The biological effects were assessed by determining cell toxicity, particle-induced chemotaxis, and the induction of gene expression of inflammatory mediators.ConclusionsStraight fibers were only slightly cytotoxic and caused weak cell migration, regardless of their thickness, while the curly fibers were more toxic and caused significantly stronger chemotaxis. Curly fibers also had the strongest effect on the expression of cytokines and chemokines. This may be due to the different aspect ratio or its twisted shape.

Mineralized black phosphorus @ silica nanofiber multi-scale enhanced hydrogel coating for fire protection of polyurethane foams

Hydrogel, as a multifunctional engineering material, has attracted much attention for its flame-retardant applications. However, the low thermal stability of hydrogels results in the formation of a weak protective layer with weak adhesion, which limits their application. Therefore, through careful design, we successfully combined calcium phosphate nanocrosslinked points, silica nanofiber networks, and black phosphorus sheets to construct a multiscale reinforcing body. This reinforcement not only significantly improves the overall strength of the material, but also imparts excellent fire resistance properties. Furthermore, we combined this reinforcement with intrinsic flame-retardant precursors to construct a hydrogel with high fire resistance. This hydrogel coating not only effectively resists flame attacks, but also exhibits excellent mechanical properties, thus addressing the shortcomings of conventional hydrogel coatings in terms of fire resistance and mechanical properties. When used to coat RPUF materials, the hydrogel-coated RPUF composites showed a 23.6% reduction in the peak heat release rate (pHRR), a 45% reduction in total smoke production (TSP), and a 27 s extension in time to ignition (TTI). The hydrogel coating was found to be effective at inhibiting the spread of fire. In addition, the molecularly designed intrinsic flame-retardant hydrogel coating has good adhesion to RPUF and other substrates, which is sufficient for practical applications. The coatings have sustained fire protection and are suitable for a range of flame-retardant applications. This innovative design provides new ideas and methods for developing high-performance flame-retardant hydrogel coatings.

Composite Aerogel Scaffolds Containing Flexible Silica Nanofiber and Tricalcium Phosphate Enable Skin Regeneration.

Poor hemostatic ability and less vascularization at the injury site could hinder wound healing as well as adversely affect the quality of life (QOL). An ideal wound dressing should exhibit certain characteristics: (a) good hemostatic ability, (b) rapid wound healing, and (c) skin appendage formation. This necessitates the advent of innovative dressings to facilitate skin regeneration. Therapeutic ions, such as silicon ions (Si4+) and calcium ions (Ca2+), have been shown to assist in wound repair. The Si4+ released from silica (SiO2) can upregulate the expression of proteins, including the vascular endothelial growth factor (VEGF) and alpha smooth muscle actin (α-SMA), which is conducive to vascularization; Ca2+ released from tricalcium phosphate (TCP) can promote the coagulation alongside upregulating the expression of cell migration and cell differentiation related proteins, thereby facilitating the wound repair. The overarching objective of this study was to exploit short SiO2 nanofibers along with the TCP to prepare TCPx@SSF aerogels and assess their wound healing ability. Short SiO2 nanofibers were prepared by electrospinning and blended with varying proportions of TCP to afford TCPx@SSF aerogel scaffolds. The TCPx@SSF aerogels exhibited good cytocompatibility in a subcutaneous implantation model and manifested a rapid hemostatic effect (hemostatic time 75 s) in a liver trauma model in the rabbit. These aerogel scaffolds also promoted skin regeneration and exhibited rapid wound closure, epithelial tissue regeneration, and collagen deposition. Taken together, TCPx@SSF aerogels may be valuable for wound healing.

Brake Fluid Condition Monitoring by a Fiber Optic Sensor Using Silica Nanomaterials as Sensing Components.

In the automotive industry, there has been considerable focus on developing various sensors for engine oil monitoring. However, when it comes to monitoring the condition of brake fluid, which is crucial for ensuring safety, there has been a lack of a secure online method for this monitoring. This study addresses this gap by developing a hybrid silica nanofiber mat, or an aerogel integrated with an optical fiber sensor, to monitor brake fluid condition. The incorporation of silica nanofibers in this hybrid enhances the sensitivity of the optical fiber glass surface by at least 3.75 times. Furthermore, creating an air gap between the glass surface of the optical fiber and the nanofibers boosts sensitivity by at least 5 times, achieving a better correlation coefficient (R2 = 0.98). In the case of silica aerogel, the sensitivity is enhanced by 10 times, but this enhancement relies on the presence of the established air gap. The air gap was adjusted to range from 0.5 mm to 1 mm, without any significant change in the measurement within this range. The response time of the developed sensor is a minimum of 15 min. The sensing material is irreversible and has a diameter of 2.5 mm, making it easily replaceable. Overall, the sensor demonstrates strong repeatability, with approximately 90% consistency, and maintains uncertainty levels below 5% across specific ranges: from 3% to 6% for silica aerogel and from 5% to 6% for silica nanofibers in the presence of an air gap. These findings hold promise for integrating such an optical fiber sensor into a car's electronic system, enabling the direct online monitoring of brake fluid quality. Additionally, the study elucidates the effect of water absorption on the refractive index of brake fluid, as well as on the silica nanomaterials.

Bound states in the continuum in circular waveguides: toward the on-chip integration of nanofiber on silicon platform.

In previously reported researches on bound state in the continuum (BIC) waveguides, almost all of them are demonstrated with top-down fabrication procedures, leading to inconvenience for post-manipulation and size tuning. Nanofibers with circular cross sections are the fundamental components to transport energy due to their intrinsic advantages of high flexibility and adjustability, which is replaceable and can be readily manipulated over size and position on the substrate. In this work, we explore the possibility of achieving on-chip integration of silica nanofiber onto a silicon-on-insulator platform. By constructing additional leakage channels in coupled nanofiber waveguides, coherently destructive interferences are successfully achieved. The heavy leakage losses from the low-index nanofiber to a high-index silicon substrate are completely eliminated with BIC, and the propagation length of the nanofiber waveguide is significantly improved.

Fabrication of elastic SiO2 aerogels with prominent mechanical strength and stability reinforced by SiO2 nanofibers and polyurethane for oil adsorption

The separation of oil from wastewater and materials for oil absorption are highly demanded in the modern industrialization. For these purposes, silica aerogels with high hydrophobicity and surface aera and low density are promising candidates for oil absorption, but limited by the poor mechanical strength and structure stability during the usage. In this study, we presented a novel compressive silica aerogel by silica nanofiber (SNF) reinforcement and subsequent hydrophobic polyurethane strengthening via moisture curing (PSAG). The obtained PSAG exhibits unique core/shell fibrous reinforcement and prominent crosslinked network structure. The porous PSAG has a porosity of 81.06 % and density of 0.43 g cm−3 at solid content of 20 %. The hydrophobic PSAG shows an impressive sorption capacity towards CH2Cl2 (11.2 g g−1), THF (5.5 g g−1) and acetone (3.8 g g−1), being able to separate 100 % of oils from an immiscible oil–water mixture. The PSAG shows exceptional resistance to acidic and alkaline conditions and has high flexibility and desirable reusability in repeatedly oil adsorption. Most importantly, the mechanical strength of SAG can be improved to 0.27 MPa of PSAG at prepolymer solid content of 20 %, and no cracking or deformation were observed after 50 cycles. Additionally, the PSAG shows impressive thermal insulation and flame retardancy performance in the air, which should have potential application as insulator for the solar evaporation for the purification of wastewater. This work provides new understanding and insight for further design and optimization of polyurethane-based reinforced aerogels.

Synthesis of flexible, strong, and lightweight oxide ceramic nanofibers via direct electrospinning of inorganic sol for thermal insulation

Oxide ceramic nanofibers are widely used in aerospace and civil facilities due to their superior thermal stability and fire resistance. Currently, electrospinning, one of the important methods for preparing oxide ceramic nanofibers, must rely on adding organic polymers to impart spinnability to inorganic sols. However, these organic polymers will inevitably leave hole flaws in the ceramic nanofibers due to thermal decomposition during the subsequent ceramization process, seriously damaging their mechanical properties. Here, a direct electrospinning strategy for inorganic sol through hydrolyzation–polycondensation rate modulation is proposed, which gets rid of the dependence of spinnability of inorganic sol on organic polymer. Taking silica nanofibers as an example, it exhibits excellent flexibility and mechanical strength (tensile stress up to 1.4 MPa), as well as thermal insulation properties (thermal conductivity as low as 0.0551 W m−1 K−1 at 300 °C). This work provides new insights into developing other high–performance oxide ceramic materials.

Machine learning assisted dual-functional nanophotonic sensor for organic pollutant detection and degradation in water

This study presents a dual-functional thin film, known as Ag nanoparticles decorated, ZnO nanorods coated silica nanofibers (AgNP-ZnONR-SNF), which demonstrates remarkable capabilities in both water purification and organic pollutants sensing. The 3D fibrous structure of ZnONR-SNF provides a large surface-area-to-volume ratio for piezo- and photo-catalytic degradation of organic pollutants under UV irradiation, achieving over 98% efficiency. Ag nanoparticles decorated on ZnONR-SNF form “hot-spot” that significantly enhance the surface-enhanced Raman spectroscopy (SERS) signal, resulting in an enhancement factor of 1056 and an experimental detection limit of 1 pg mL−1. Furthermore, a machine learning algorithm is developed for the qualitative and quantitative detection of multiple contaminants, achieving high accuracy (92.3%) and specificity (89.3%) without the need for preliminary processing of Raman spectra. This work provides a promising nanoengineering solution for water purification and sensing with improved detection accuracy, purification efficiency, and cost-effectiveness.

Flexible crystalline zinc doped silica nanofibers with superior wettability and remediation for oily wastewater

Construction of ceramic fibrous membranes with good mechanical property and separation performance for the remediation of surfactant stabilized emulsions at high-temperature or complex environment is on great demand, yet still a challenge. Herein, the zinc ions doped silica (ZSO) nanofibrous membranes with expectable flexibility and superior selective wettability is prepared via a facile sol–gel electrospinning technique. The doping of zinc ions in silica nanofibers induced the obvious variation in crystalline and surface roughness structure, which were directly relevant to the mechanical properties and wettability of the resultant ZSO nanofibrous membranes. The advantageous features favored the ZSO membranes with excellent surfactant stabilized oil-in-water emulsion separation performance, including the separation efficiency of >98 %, the permeation flux of ∼3900 L m−2 h−1 driven by gravity, outstanding chemical stability, and good reusability within 10 cycles. In addition, the rationally designed micro-/nano-structured composite ceramic fibrous membranes displayed significant improvements on structural stability, mechanical property, and prominent separation performance towards emulsions at high temperature (∼95 °C) and nanoparticle-containing wastewater. The clarification of the relationship among crystalline structure, surface roughness, mechanical properties, and application performance would facilitate the fabrication of filtration materials used in the fields of oil-spill cleanup, seawater destination, and wastewater remediation.

Parallel fabrication of silica optical microfibers and nanofibers

Parallel fabrication of silica optical microfibers and nanofibers

Rapid and non-destructive nanofiber diameter measurement using Spontaneous Four Wave Mixing

We will present a rapid and non-destructive technique for the measurement of the mean diameter of a silica nanofiber using the wavelength position of the signal peak in a spontaneous four wave mixing experiment. The nanofiber diameter can be characterized in a range going at least from 650 to 1250nm. Several nanofibers were characterized, and the measured diameter show a good accordance with the one obtained using a Scanning Electron Microscope. The technique is simple to use and has even the potential to be implemented in situ in order to realize a diameter measurement during the pulling of the nanofiber for a better control of the final diameter of the nanofiber.

Electrospun‐SiO2‐Nanofiber‐Reinforced Cellulose Aerogel Loaded with ZIF‐67 for Air Filtration and Formaldehyde Adsorption

AbstractIndoor air pollution, which is detrimental to the human respiratory, nervous, and cardiovascular systems, is of increasing concern because considerable time is spent indoors. Thus, there is an urgent need to develop improved methods for controlling indoor air pollution. In this study, electrospinning and freeze‐drying methods are used to prepare a cellulose–silica nanofiber (C‐SNF) aerogel loaded with zeolitic imidazolate framework‐67 (ZIF‐67) for use in indoor air purification systems. The C‐SNF aerogel doped with 0.75 wt.% SiO2 nanofiber (SNF) exhibits a maximum compressive stress of 8.7 MPa, which is higher than that (6.4 MPa) of a pure cellulose aerogel. The compressive modulus of the aerogel exceeds 85% of its original value after 100 compression cycles. The C‐SNF aerogel exhibits a filtration efficiency of 99.91% against 0.3 µm salt particles at 32 L min−1, which is higher than that of the pure cellulose aerogel (51.25%). Moreover, a stable removal efficiency of 99.92% toward 2.5 µm particulate matter (PM2.5) is observed after ten cycles. Notably, the addition of ZIF‐67 to C‐SNF (ZIF‐67@C‐SNF) aerogel by in situ growth method resulted in a porosity of 92.3% and formaldehyde removal of 93.75%. The ZIF‐67@C‐SNF aerogel can be used in various applications including indoor‐air and adsorptive‐filtration masks.

Elastic 3D-Printed Nanofibers Composite Scaffold for Bone Tissue Engineering.

Loading nanoparticles into hydrogels has been a conventional approach to augment the printability of ink and the physicochemical characteristics of scaffolds in three-dimensional (3D) printing. However, the efficacy of this enhancement has often proven to be limited. We amalgamate electrospun nanofibers with 3D printing techniques to fabricate a composite scaffold reminiscent of a "reinforced concrete" structure, aimed at addressing bone defects. These supple silica nanofibers are synthesized through a dual-step process involving high-speed homogenization and low-temperature ball milling technology. The nanofibers are homogeneously blended with sodium alginate to create the printing ink. The resultant ink was extruded seamlessly, displaying commendable molding properties, thereby yielding scaffolds with favorable macroscopic morphology. In contrast to nanoparticle-reinforced scaffolds, composite scaffolds containing nanofibers exhibit superior mechanical attributes and bioactivity. These nanofiber composite scaffolds demonstrate enhanced osteoinductive properties in both in vitro and in vivo evaluations. To conclude, this research introduces a novel 3D printing approach where the fabricated nanofiber-infused 3D-printed scaffolds hold the potential to revolutionize the realm of 3D printing in the domain of bone tissue engineering.

Silica Nanofibers with Enhanced Wettability and Mechanical Strength for Bone Tissue Engineering: Electrospinning without Polymer Carrier and Subsequent Heat Treatment

AbstractThe unique properties of silica, such as biocompatibility and the ability to promote cell growth, demonstrate favorable results in different applications such as drug delivery, biomedical applications, and tissue engineering (TE). Electrospinning has emerged as a method for creating a substrate with a high surface area and structural resemblance to natural extracellular matrices. A common method of fabricating silica nanofibers (SNFs) for TE involves hybrid silica/ polymer nanofibers, which require calcination to remove the polymer and obtain pure silica. This study aimed to use the sol‐gel precursor tetraethyl orthosilicate (TEOS) to fabricate pure SNFs through electrospinning and investigate calcination's effect on their morphology, thermal behavior, mechanical properties, wettability, and porosity. The findings indicated that the calcination process reduced Young's modulus, wettability, and porosity, which may influence the applications of SNFs in TE. Nanofibrous mats with high Young's modulus can play a crucial role in providing mechanical support for tissue repair. Additionally, high porosity and wettability can facilitate cell attachment and growth by improving nutrient and oxygen transport to the cells. This study provides valuable insights into the potential use of pure SNFs and highlighted the effects of heat treatment on their properties.

Robust synthesis of free-standing films comprising conjugated microporous polymers nanotubes for water disinfection

Water environmental pollution especially caused by bacteria, viruses and other microorganisms always would accelerate the spread of infectious diseases and has been one of the issues highly concerned by the World Health Organization for a long time. The development of novel antibacterial materials with high activity for water cleanness was of great importance for public health and ecological sustainable development. In this work, we developed two really free-standing conjugated microprous polymers (CMPs) film with large size and processibility by a simple and convenient solid surface-assisted polymerization between bromo- and aryl-acetylene monomers. With the solid interfacial orientation from silica nanofibers, the resulting CMPs film exhibited nanotube-liked morphology with BET surface area of 379.5 m2 g−1 and 480.1 m2 g−1. The introduction of antibacterial isocyanurate and acetanilide group into polymer skeleton brings the resulting CMPs film intrinsically antimicrobial capability and durability. The growth of E. coli can be completely inhibited by the resulting CMPs film even after several cycles. Our work was suggested to provide a new route for rational design of CMPs film or membrane with antibacterial activity for water treatment and sterilization.

Design and Fabrication of Electrospun PLA-Based Silica-Modified Composite Nanofibers with Antibacterial Properties for Perspective Wound Treatment.

The aim of this study was to develop a novel amikacin (AMI) delivery system with prolonged release based on composite electrospun nanofibers of PLA supplemented with AMI-loaded Si nanoparticles of different morphology. The resultant materials were characterized in terms of their physical properties (scanning electron microscopy, Brunauer-Emmett-Teller analysis, thermogravimetric analysis, water contact angle). High-Performance Liquid Chromatography was used to determine the AMI content in the liquid fractions obtained from the release study. The results show that nanofibers of fumed silica exhibited an aggregated, highly porous structure, whereas nanofibers of mesoporous silica had a spherical morphology. Both silica nanoparticles had a significant effect on the hydrophilic properties of PLA nanofiber surfaces. The liquid fractions were investigated to gauge the encapsulation efficiency (EE) and loading efficiency (LE) of AMI, demonstrating 66% EE and 52% LE for nanofibers of fumed silica compared to nanofibers of mesoporous silica nanoparticles (52% EE and 12.7% LE). The antibacterial activity of the AMI-loaded nanofibers was determined by the Kirby-Bauer Method. These results demonstrated that the PLA-based silica nanofibers effectively enhanced the antibacterial properties against the Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae.