SiO2 Nanofibers Research Articles

Three Birds with One Stone: An Integrated Cathode-Electrolyte Structure for High-Performance Solid-State Lithium-Oxygen Batteries.

Constructing solid-state lithium-oxygen batteries (SSLOBs) holds a great promise to solve the safety and stability bottlenecks faced by lithium-oxygen batteries (LOBs) with volatile and flammable organic liquid electrolytes. However, the realization of high-performance SSLOBs is full of challenges due to the poor ionic conductivity of solid electrolytes, large interfacial resistance, and limited reaction sites of cathodes. Here, a flexible integrated cathode-electrolyte structure (ICES) is designed to enable the tight connection between the cathode and electrolyte through supporting them on a 3D SiO2 nanofibers (NFs) framework. The intimate cathode-electrolyte structure and the porous SiO2 NFs scaffold combination are favorable for decreasing interfacial resistance and increasing reaction sites. Moreover, the 3D SiO2 NFs framework can also behave as an efficient inorganic filler to enhance the ionic conductivity of the solid polymer electrolyte and its ability to inhibit lithium dendrite growth. As a result, the elaborately designed ICES can simultaneously tackle the issues that limit the performance liberation of SSLOBs, making the batteries deliver a high discharge capacity and a long lifetime of 145 cycles with a cycling capacity of 1000 mAh g-1 at 60°C, much superior to coventional SSLOBs (50 cycles).

SiO2 nanofiber composite gel polymer electrolyte by in-situ polymerization for stable Li metal batteries

Gel polymer electrolytes (GPEs) are promising alternatives to liquid electrolytes applied in high-energy-density batteries. Here superior SiO2 nanofiber composite gel polymer electrolytes (SNCGPEs) are developed via in-situ ionic ring-opening polymerization of 1,3-dioxolane (DOL) monomers in SiO2 nanofiber membrane (PDOL-SiO2) for lithium metal batteries. The oxygen atoms of PDOL together with Si-O of SiO2 construct a more efficient channel for Li+ migration. Consequently, the lithium ion transference number (tLi+) and ionic conductivity (σ) at 30 °C of PDOL-SiO2 are 0.80 and 1.68 × 10−4 S/cm separately. PDOL-SiO2 manifests the electrochemical decomposition potentials of 4.90 V. At 0.5 mA/cm2, Li|PDOL-SiO2|Li cell shows a steady cycling performance for nearly 1400 h. LFP|PDOL-SiO2|Li battery can steadily cycle at 0.5 C with a capacity retention rate of 89% after 200 cycles. While cycling at 2 C, the capacity retention rate can maintain at 78% after 300 cycles. This contribution provides a innovative strategy for accelerating Li+ transportation via designing PDOL molecular chains throughout the SiO2 nanofiber framework, which is crucial for high-energy-density LMBs.

Form-stable phase change materials based on hierarchically channel-like silica nanofibrous mats for thermal energy storage

Hierarchical channel-like SiO2 nanofibrous mats were prepared via microemulsion electrospinning in combination with calcination for thermal energy storage. The interior channel number of SiO2 nanofibers was flexibly regulated by tuning the proportion of continuous phase to dispersion phase. Microemulsion electrospinning, as a method of single-spinneret electrospinning, makes it versatile, simple and convenient for the preparation of hierarchical SiO2 nanofibers with multi-channel structure and high porosity. Quinary fatty acid eutectics were encapsulated in multi-channel SiO2 mats to obtain form-stable phase change materials (FSPCMs). The results indicated the crystallization enthalpy and melting enthalpy of as-fabricated FSPCMs could be up to 115.7 and 112.9 J·g−1, respectively. After 40 thermal cycles, there is no significant difference for the phase change temperature and enthalpy of FSPCMs, revealing outstanding thermal cycling stability. The study proves that microemulsion electrospinning is exactly a straightforward and universal method to fabricate the supporting substance of FSPCMs.

Electronic nose based on hybrid free-standing nanofibrous mats for meat spoilage monitoring

Food safety and quality control have become nowadays a major priority for the sake of public health to protect consumers from the risks of foodborne diseases and food poisoning. For instance, in the case of the decomposition of meat protein, ammonia and biogenic amines content can be used as a parameter to evaluate meat quality. However, practical analytical methods for in loco evaluation of amines release by meat are still on demand. Herein, we report hybrid free-standing composite nanofibers as sensing platforms to identify volatile amines (ammonia, methylamine and trimethylamine), as one of the main components of the gas produced in the process of meat spoilage, and to monitor fish freshness at room temperature. For that purpose, SiO2:In2O3, SiO2:ZnO and SiO2 nanofibers, prepared by electrospinning followed by thermal treatment, were deposited onto interdigitated electrodes and then modified with polyaniline and poly(styrene sulfonate). Seven sensing units of distinct compositions were employed in an impedimetric electronic nose, and multidimensional projection was used to help in the discrimination of standard analytes as well as of analytes released during the deterioration of fish real samples. The frequency selection resulted in improved discrimination by multidimensional projection and the sensor array showed an excellent performance to be applied in fish spoilage monitoring.

Phase change materials with multiple energy conversion and storage abilities based on large-scale carbon felts

The application of organic phase change materials (PCM) was hindered in some areas due to the poor thermal and electrical conductivity, easy leakage during phase change process, and monotonous energy conversion model. To overcome these drawbacks, a large-scale commercial carbon felt (CF) covered with SiO2 nanofibers (SiO2@CF) was adopted to encapsulate the paraffin wax (SiO2@CF-ssPCM) using a multifunctional PCM composite. Based on the hierarchically porous framework and enhanced thermal conductivity (0.73 W/m·K) and electrical conductivity (4.95 S/m), the SiO2@CF-ssPCM exhibited good shape stability and high latent heat of 183.8 J/g. The solar-thermal conversion and electro-thermal conversion efficiency was up to 87.0% and 82.2%, respectively. It also showed superior thermal storage performance as thermal management materials and outstanding cycles stability as a wearable temperature control device. Thus, the SiO2@CF-ssPCM has a great potential application for the multiple energy conversion and storage abilities.

Deoxycholic acid-modified microporous SiO2 nanofibers mimicking colorectal microenvironment to optimize radiotherapy-chemotherapy combined therapy

Radiotherapy and chemotherapy remain the main therapeutics for colorectal cancer. However, due to their inevitable side effects on nomal tissues, it is necessary to evaluate the toxicity of radio-/chemotherapy regimens. The newly developed in vitro high throughput strategy is promising for these assessments. Nevertheless, the currently monolayer culture condition adopted in the preclinical screening processes in vitro has been proved not so efficient as in vivo since its poor physiological similarity to in vivo microenvironment. Herein, we fabricated microporous SiO2 nanofiber mats and further bioactivated with deoxycholic acid (DCA) to mimic the chemical signals in the colorectal cancer microenvironment for in vitro regimen assessment of radiotherapy and chemotherapy. The colorectal cancer cells contacted with the DCA-modified SiO2 nanofiber (SiO2-DCA NF) mats spatially, and the human intestinal epithelial cell on SiO2-DCA NF mats exhibited better x-ray and cisplatin tolerance. The distinguishable irradiation and drug tolerance of cells on SiO2-DCA NF mats indicated that the actual microenvironment of intestine might instruct colorectal cancer differently compared with the common biological experiments. The presented DCA-modified microporous SiO2 nanofibrous mats endowing a better mimicry of colorectal micro-environment, would provide a promising platform for in vitro assessment of radio-/chemotherapy regimens.

Understanding uptake kinetics and ion dynamics in microporous polymer gel electrolytes reinforced with SiO2 nanofibers

In the present study kinetics of electrolyte uptake by microporous polymer gel electrolyte (MPGEs) comprising PMMA polymer and various concentrations of SiO2 nanofibers has been reported. Dispersion of nanofibers in PMMA results in high porosity and less tortuosity in the composite membranes. Immobilization of 1 M LiClO4 in ethylene carbonate (EC) and diethyl carbonate (DEC) in the membranes result a high electrolyte uptake of 280. The optimum electrochemical properties have been observed with 5 wt% nanofibers, which show the maximum ionic conductivity of 8.4 × 10−3 Scm−1 at room temperature. The kinetic study of electrolyte uptake determines the regression coefficient (R2) for the various mathematical models. This regression coefficient analysis suggested that the uptake mechanism displayed by the nanocompoites is best fitted to the power law model. According to the power law analysis, the diffusion coefficients have been determined, which results a suitable corelation with the electrochemical studies of MPGEs.

Facile One-Step Deposition of Ag Nanoparticles on SiO2 Electrospun Nanofiber Surfaces for Label-Free SERS Detection and Antibacterial Dressing

The fabrication of highly active and free-standing surface-enhanced Raman scattering (SERS) substrates in a simple and low-cost manner has been a crucial and urgent challenge in recent years. Herein, SiO2 nanofiber substrates modified with size-tunable Ag nanoparticles were prepared by the combination of electrospinning and in situ chemical reduction. The results demonstrate the presence and uniform adsorption of Ag nanoparticles on the SiO2 matrix surface. The free-standing composite nanofibrous substrates show high-performance SERS response toward 4-mercaptophenol and 4-mercaptobenzoic acid, and the detection limit can be as low as 10-10 mol/L. Most importantly, the as-prepared substrate as a versatile SERS platform can realize label-free detection of bio-macromolecules of bacteria, i.e., Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, the substrates also possess outstanding antibacterial activities against S. aureus and E. coli. Briefly, the significance of this study is that size-tunable Ag nanoparticles can be decorated on SiO2 nanofiber surfaces with triethanolamine as a bridging and reducing agent through a one-pot reaction, and the as-prepared nanofibrous membranes are expected to act as a candidate for label-free SERS detection as well as antibacterial dressing.

Nanofiber induced enhancement of electrical and electrochemical properties in polymer gel electrolytes for application in energy storage devices

In this article, a significant study on ionic conduction properties of novel nanocomposite polymer gel electrolytes (NCPGEs) is carried out using poly (methyl methacrylate) (PMMA) with nanofibers of silica (SiO2) complexed with lithium perchlorate (LiClO4) by combining experimental work and computational modelling. The compositional variation of SiO2 nanofibers in polymer electrolytes induces a visible alteration in different characteristics like ionic conductivity, electrochemical stability, interfacial stability, surface morphology and optical properties. Among all the compositions, NCPGEs containing 5 wt% nanofibers exhibit maximum ionic conductivity of 4.6 × 10−3 Scm−1 at room temperature. Fourier Transform Infrared Spectroscopy (FTIR) has shown a better interaction between lithium ions (Li+) with carbonyl group of PMMA in presence of SiO2 nanofibers. X-ray photoelectron spectroscopy (XPS) has confirmed various interactions among different constituents in NCPGEs. A combined molecular dynamics (MD) simulation and density functional theory (DFT) show a stable interaction between polymer with nanofiber filler and Li salt.

Loss reduction in sharply bent optical nanofibers by coupling with Au nanoparticles

Bending losses of sharply bent optical nanofibers or nanowires coupling with Au nanoparticles (Au NPs) are investigated using a finite-difference time-domain (FDTD) method. Relying on the ultra-tight optical confinement of the Au NPs, bending losses of the sharply bent optical nanofibers or nanowires can be effectively reduced by attaching Au NPs to the inner edge of the bent nanofibers or nanowires. At 650-nm wavelength, a bending-loss reduction of 4.7 dB/90° is obtained for a 300-nm-diameter SiO2 nanofiber coupling with seven 140-nm-diameter Au NPs when the bending radius is 1.0 μm. Our results suggest a potential route to realizing sharply-bent optical nanofibers or nanowires with acceptable bending losses for constructing highly compact photonic integrated circuits or devices.

Porous SiO2 Nanofibers Loaded with CuO Nanoparticles for the Dosimetric Detection of H2S

Mesoporous SiO2 nanofibers were prepared by electrospinning dispersions of preformed SiO2 nanoparticles and infiltrated with soluble Cu compounds, forming CuO/SiO2 nanocomposites after heat treatme...

Fabrication of Ag modified SiO2 electrospun nanofibrous membranes as ultrasensitive and high stable SERS substrates for multiple analytes detection

Surface-enhanced Raman spectroscopy (SERS) is a powerful analytical tool, but how to obtain effective and versatile SERS substrates is still a challenge. Herein, a simple and efficient strategy to prepare SERS substrates with ultra-sensitivity, high stability and wide applicability is presented. SiO2 nanofibrous membranes were prepared by electrospinning and calcination, and modified with Ag nanoparticles. The results show that Ag nanoparticles decorated on SiO2 nanofibers evenly and tightly through chemical bonding. The as-prepared membranes exhibit high flexibility and thermostability. The electrospun nanofibrous membranes show an ultra-high sensitivity of 10−11 mol/L (an enhancement factor of 107) for small molecules, and the lowest detection limit near to 10−8 mol/L for pesticides thiram. It is also demonstrated that the substrates remain excellent SERS signal stability even after standing for 60 days (intensity decrease only for 21.7%). More importantly, the as-prepared substrates can be performed for quantitative detection of bacteria.

Conductive self-standing nanofiber fabric of fluorine-doped tin oxide prepared by electrospinning for use in flexible electronics

To realize a conductive substrate with heat resistance and flexibility for the application to flexible electronics, we aimed to reduce the resistance of the fluorine-doped tin oxide (FTO) ceramic nanofiber (NF) non-woven fabrics produced by the electrospinning method. Using NH4F and SnF2 as the raw materials for fluorine doping, the structure and electrical properties of FTO-NF non-woven fabric were compared. The non-woven fabrics obtained in both solutions were several cm square made by NFs with a diameter of 150~800 nm, and all NFs consisted of nanoparticles with a diameter of about 20 nm. The resistivity of the FTO-NF fabric could be reduced to $$5.19 ~\mathrm{\Omega \cdot cm}$$ by the improvements such as adding tin isopropoxide and mixing without using water for a solvent without making a precursor of FTO so that the raw material is uniformly adsorbed on the polymer in the solution. By considering the space occupancy of the NFs in the fabric, the minimum net resistivity of the FTO-NF fabric was estimated to be $$0.56 ~ \mathrm{\Omega \cdot cm}$$ . Since the obtained FTO fabric was brittle and cracked when bent, we made a prototype of a three-layer NF non-woven fabric composited with amorphous SiO2 NFs. The sheet resistance was $$6.4 ~\mathrm{k\Omega /sq}$$ , no cracks or breaks occurred even when wrapped around a glass rod with a diameter of 5 mm $$\phi$$ , and the rate of increase in the resistance after 100 bends could be suppressed to 4.9%.

Flexible hierarchical Pd/SiO2-TiO2 nanofibrous catalytic membrane for complete and continuous reduction of p-nitrophenol

Flexible and hierarchical nanostructured Pd/SiO2-TiO2 nanofibrous catalytic membranes were fabricated via combining electrospinning technique and a two-step hydrothermal method. The size and distribution of TiO2 nanorods immobilised on SiO2 nanofibrous membranes can be regulated via adjusting the dosage of TiCl3 solution in the first step hydrothermal process. When using an optimal TiCl3 solution dosage of 0.2 mL, a hierarchical structured Pd/SiO2-TiO2-0.2 nanofibrous catalytic membrane with uniformly dense TiO2 nanorods loaded on SiO2 nanofibers is obtained, and still shows good tensile strength and flexibility. The catalytic activity of Pd/SiO2-TiO2-0.2 increases 5 times as compared to Pd/SiO2-TiO2-0 in the reduction of p-nitrophenol (PNP) to p-aminophenol (PAP). The modification with TiO2 nanorods can provide more surface areas for loading the Pd nanoparticles, thereby increased active sites. The three-dimensional open-cell network stacked and assembled by thousands of SiO2 nanofibers and TiO2 nanorods enhances the contact between the reactants and Pd nanoparticles. Both aspects contribute the superior catalytic activity of Pd/SiO2-TiO2-0.2. Furthermore, a continuous and complete conversion of PNP to PAP can be stably operated over 240 min in a gravity-driven catalytic membrane reactor constructed by Pd/SiO2-TiO2-0.2.

Fabrication of ordered mesoporous POMs/SiO2–NH2 nanofibers for production of DFF from 5-HMF for cellulose wastewater resource recovery

5-hydroxymethylfurfural (5-HMF) is a biomass cellulose platform product that can be transformed into the valuable resource 2,5-diformylfuran (DFF). Polyoxometalates (POMs) have important applications in resource recovery technologies and cellulose wastewater treatment. Ordered mesoporous H5PMo10V2O40/SiO2–NH2 (wt%) nanofibers (HPMoV/meso-SiO2-NH2 (wt%)) were synthesized by the combining in-situ fabrication and electrospinning techniques, using H5PMo10V2O40 (HPMoV) and organic-silica as precursors. Aiming the recovery and transformation of 5-HMF, aerobic oxidation of 5-HMF was explored using these nanofibers as catalysts, while the best yield of DFF (90.0%) was obtained upon HPMoV/meso-SiO2-NH2 (23%) nanofibers after 8 h at 120 °C using oxygen (1.0 MPa). The selectivity to DFF was improved by changing the hydrophilicity of the HPMoV@SiO2 nanofibers to hydrophobicity by modifying SiO2 nanofibers with –NH2R compared to mesoporous SiO2 nanofibers, which allowed the formed DFF to be isolated. In the recycling test, HPMoV@SiO2–NH2 showed good performance, and no leaching of active sites from SiO2–NH2 due to the interactions between them occurred after 10 cycles. The production of DFF from the real cellulosic wastewater was obtained with 118% yield based on 5-HMF conversion by HPMoV/meso-SiO2-NH2 (23) and oxygen, which was contributed to the one-pot conversion of sugar, furan and 5-HMF in the wastewater.

Loading of Au/Ag Bimetallic Nanoparticles within and Outside of the Flexible SiO2 Electrospun Nanofibers as Highly Sensitive, Stable, Repeatable Substrates for Versatile and Trace SERS Detection.

In this paper, we propose a facile and cost-effective electrospinning technique to fabricate surface-enhanced Raman scattering (SERS) substrates, which is appropriate for multiple analytes detection. First of all, HAuCl4∙3H2O was added into the TEOS/PVP precursor solution, and flexible SiO2 nanofibers incorporated with gold nanoparticles (SiO2@Au) were prepared by electrospinning and calcination. Subsequently, the nanofibrous membranes were immersed in the tannic acid and 3-aminopropyltriethoxysilane solution for surface modification through Michael addition reaction. Finally, the composite nanofibers (Ag@T-A@SiO2@Au) were obtained by the in-situ growth of Ag nanoparticles on the surfaces of nanofibers with tannic acid as a reducing agent. Due to the synergistic enhancement of Au and Ag nanoparticles, the flexible and self-supporting composite nanofibrous membranes have excellent SERS properties. Serving as SERS substrates, they are extremely sensitive to the detection of 4-mercaptophenol and 4-mercaptobenzoic acid, with an enhancement factor of 108. Moreover, they could be utilized to detect analytes such as pesticide thiram at a low concentration of 10−8 mol/L, and the substrates retain excellent Raman signals stability during the durability test of 60 days. Furthermore, the as-fabricated substrates, as a versatile SERS platform, could be used to detect bacteria of Staphylococcus aureus without a specific and complicated bacteria-aptamer conjugation procedure, and the detection limit is up to 103 colony forming units/mL. Meanwhile, the substrates also show an excellent repeatability of SERS response for S. aureus organelles. Briefly, the prime novelty of this work is the fabrication of Au/Ag bimetallic synergetic enhancement substrates as SERS platform for versatile detection with high sensitivity and stability.

Chirality Detection by Raman Spectroscopy: The Case of Enantioselective Interactions between Amino Acids and Polymer-Modified Chiral Silica.

In chirality research area, it is of interest to reveal the chiral feature of inorganic nanomaterials and their enantioselective interactions with biomolecules. Although common Raman spectroscopy is not regarded as a direct chirality analysis tool, it is in fact effective and sensitive to study the enantioselectivity phenomena, which is demonstrated by the enantio-discrimination of amino acid enantiomers using the polydopamine-modified intrinsically chiral SiO2 nanofibers in this work. The Raman scattering intensities of an enantiomer of cysteine are more than twice as high as those of the other enantiomer with opposite handedness. Similar results were also found in the cases of cystine, phenylalanine, and tryptophan enantiomers. In turn, these organic molecules could be used as chirality indicators for SiO2, which was clarified by the unique Raman spectra-derived mirror-image relationships. Thus, an indirect chirality detection method for inorganic nanomaterials was developed.

Self-reinforcement of Light, Temperature-Resistant Silica Nanofibrous Aerogels with Tunable Mechanical Properties

Silica aerogels have attracted significant interest in thermal insulation applications because of their low thermal conductivity and great thermal stability, however, their fragility has limited their application in every-day products. Herein, a self-reinforcing strategy to design silica nanofibrous aerogels (SNFAs) is proposed using electrospun SiO2 nanofibers as the matrix and a silica sol as a high-temperature nanoglue. Adopting this approach results in a strong and compatible interfacial interaction between the SiO2 fibers and the silica sol, which results in the SNFAs exhibiting high-temperature-resistant and tunable mechanical properties from elastic to rigid. Furthermore, additional properties such as low density, high thermal insulation performance, and fire-resistance are still retained. The self-reinforcing method described herein may be extended to numerous other new ceramic aerogels that require robust mechanical properties and high-temperature resistance.

Preparation of Ag@PDA@SiO2 electrospinning nanofibrous membranes for direct bacteria SERS detection and antimicrobial activities

In this paper, a convenient method to fabricate flexible and free-standing surface-enhanced Raman scatting (SERS) substrates for direct bacteria detection without aptamer bonding is presented. SiO2 nanofibers were prepared via electrospinning and calcination by using tetraethyl orthosilicate as the precursor. Subsequently, it was coated with polydopamine (PDA) by self-polymerization. Finally, Ag@PDA@SiO2 nanofibrous membranes were obtained through in situ growth of Ag nanoparticles in Tollens’ reagents. The as-prepared Ag@PDA@SiO2 composite nanofibrous membranes were characterized by techniques of scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, energy-dispersive x-ray spectroscopy and thermo gravimetric analysis. The flexibility of the as-prepared nanofibrous membranes were verified simply through manual folding. Small molecule probes of 4-mercaptophenol (4-MPh) and 4-mercaptobenzoic acid (4-MBA) were chosen to investigate the SERS sensitivity of the as-prepared Ag@PDA@SiO2 as free-standing substrates. Furthermore, Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), as typical strains of Gram-negative and Gram-positive bacteria, were performed to directly SERS detection by dropping bacteria suspension onto the fibrous membranes without any previous treatment, such as aptamer combination. In addition, the antimicrobial properties of the as-prepared Ag@PDA@SiO2 electrospinning nanofibrous membranes were tested by inhibition zone and turbidity methods. The results show that Ag nanoparticles with an average diameter of 50 nm are uniformly deposited on the surface of electrospinning nanofibers, and the as-prepared Ag@PDA@SiO2 nanofibrous membranes are flexible. As SERS substrates, it shows a rather high detection limitation of 10−11 mol l−1 for 4-MPh and 4-MBA. More importantly, this substrate can be applied for bacteria label-free SERS detection, i.e., complicated procedures are avoided. Meanwihile, the as-prepared Ag@PDA@SiO2 nanofibrous membranes exhibit excellent antibacterial properties. Thus, it has application prospects in trace bacteria detection and water purification.

Polymer Template Synthesis of Flexible SiO2 Nanofibers to Upgrade Composite Electrolytes.

Flexible oxide ceramic films offer prospects for revolutionizing diverse fields such as energy and electronics, but their fabrication methods are typically elaborate and cannot be expanded. Here, we report a scalable strategy to fabricate flexible and robust SiO2 nanofiber films with controllable morphology using a sol-gel electrospinning method followed by low-temperature calcination. When applied to composite polymer electrolytes (CPEs) for solid-state batteries by filling polyethylene oxide into porous ceramic films, SiO2 nanofibers with large surface areas (51 m2·g-1) demonstrate strong Lewis interfacial interactions and isotropic ionic transfer channels that mitigate polymer crystallinity and Li+-concentration polarization, imparting high conductivity (1.3 × 10-4 S·cm-1 at 30 °C) and structural stability to the electrolytes. As a result, all-solid-state LiFePO4||Li shows great rate capability and long cycling stability with high discharge capacities of 159 and 132 mA·h·g-1 at 0.5C under 60 and 45 °C, respectively, demonstrating broad commercial prospects for the scale production of efficient solid electrolytes.