Silica Nanofibers Research Articles

Fabrication, Design and Characterization of 1D Nano-Fibrous SiO2 Surface by a Facile and Scalable Method

In this paper, new 1D nano-fibrous SiO2 with functionalized surfaces is prepared. First, the effect of dispersion on the morphology and the surface properties of the silica SiO2 compounds are investigated. Second, energy dispersive spectrometer (EDS) and variable pressure scanning electron microscope (VP-SEM) show typically pure and fibrous texture on the surface of SiO2. Third, the presence of the bridging oxygen stretching vibration Si-O-Si, as well as the increase in the intensity ratio between Si-OH band and Si-O-Si are revealed by (FTIR) spectroscopy. Furthermore, X-ray diffraction (XRD) validates the conservation of the SiO lattice after chemical treatment through the KOH for both dispersed and non-dispersed samples. In addition, the shift of the XRD main peak (101) is in good agreement with the FTIR results showing the shift of Si-O-Si peak and the increase in the intensity ratio of Si-OH/Si-O-Si. The dispersed SiO2 sample exhibits a promising functionalized surface with satisfactory results in terms of silica nanofibers crystallinity and chemical composition. As a result, gigh resolution transmission electron microscopy (HR-TEM) data corroborate the claim of the presence of SiO2 nanofibers on the surface from 20 nm to 250 nm. New nano-fibrous SiO2 surfaces will be used to improve interfacial bonding strength between SiO2 compounds and polymer (or organic materials).

Engineering Biomimetic Extracellular Matrix with Silica Nanofibers: From 1D Material to 3D Network.

Biomaterials at nanoscale is a fast-expanding research field with which extensive studies have been conducted on understanding the interactions between cells and their surrounding microenvironments as well as intracellular communications. Among many kinds of nanoscale biomaterials, mesoporous fibrous structures are especially attractive as a promising approach to mimic the natural extracellular matrix (ECM) for cell and tissue research. Silica is a well-studied biocompatible, natural inorganic material that can be synthesized as morpho-genetically active scaffolds by various methods. This review compares silica nanofibers (SNFs) to other ECM materials such as hydrogel, polymers, and decellularized natural ECM, summarizes fabrication techniques for SNFs, and discusses different strategies of constructing ECM using SNFs. In addition, the latest progress on SNFs synthesis and biomimetic ECM substrates fabrication is summarized and highlighted. Lastly, we look at the wide use of SNF-based ECM scaffolds in biological applications, including stem cell regulation, tissue engineering, drug release, and environmental applications.

Anamorphic beam shaping system designed to optimize irradiance distribution in the Cofiblas process for glass nanofibers production

Glass fibers play a key role as reinforcements in composite materials, where increasing mechanical properties at affordable costs are required in applications such aerospace, automotive and wind turbine manufacturing. The production of glass nanofibers augurs a substantial enhancement of their performance. However, although different techniques are currently used to produce glass, polymer or carbon nanofibers, none of them is practical to continuously produce solid, non-porous and separated glass nanofibers with capability to feasibly scaling up for mass production. The continuous fiberizing by laser melting (Cofiblas), makes possible to obtain ultrafine fibers with virtually infinite length.Here, we provide a deep analysis on the influence of the laser beam shaping system on the performance of the Cofiblas technique. Two different optical systems are compared: the first one consists of a beam-splitter coupled to a set of mirrors and spherical lenses. While the second one, is based on an anamorphic system comprising a simple combination of cylindrical and spherical lenses. Both configurations are evaluated and compared in several sets of experiments with the main target of obtaining continuous glass nanofibers with the smallest diameter. The anamorphic system generates an elliptical Gaussian distribution of the laser beam irradiance, which increases the energy absorbed by the preform. As a result, continuous silica nanofibers with diameters 84.5% smaller are obtained with the anamorphic system, compared with the optical system constituted by spherical lenses.

THE INFLUENCE OF ELECTRICAL VOLTAGE ON FORMATION OF SILICA NANO FIBER WITH ELECTROSPINNING METHOD

Silica nanofibers have been successfully fabricated using electrospinning method. Silica solution was prepared with molar rasio of tetraethyl orthosilicate (TEOS): ethanol: aquabides:hydrogen chloride (HCl) of 1 : 10 : 3 : 0.04. Polyvinyl alcohol ( PVA) of 10% was added to solution. The solutions were then mixed with a ratio of silica: PVA solution of 2: 3 ml. The functional group of silica/PVA was characterized by Fourier transform Infrared Spectroscopy (FTIR). Morphology and elements analysis was tested by Scanning Electron Microscopy - Energy Dispersive Spectroscopy (SEM - EDS). The functional groups of silica/PVA solution formed are –OH, C-H, CH 2 , C=O, Si-O, and Si-O-Si which indicate the occurrence of cross-linking between silica and PVA. The functional groups shown in the solution are still visible on the silica nanofibers in the presence of C, O, and Si elements in the EDS results of the nanosilica fibers. The surface morphology shows that the silica nanofibers are more continuous and the beads are relatively less with increasing electrospinning voltage. The average fiber diameter by taking into account the estimated standard deviation, shows a graph with a linear trend and increasing the applied electrospinning voltage. Silica nanofibers with diameter range (80-150) nm are obtained

Micronewton nanofiber force sensor using Brillouin scattering.

We present a new class of force sensor based on Brillouin scattering in an optical nanofiber. The sensor is a silica nanofiber of a few centimeters with a submicron transverse dimension. This extreme form factor enables one to measure forces ranging from 10 μN to 0.2N. The linearity of the sensor can be ensured using the multimode character of the Brillouin spectrum in optical nanofibers. We also demonstrated non-static operation and a competitive signal-to-noise ratio as compared to commercial force sensor resistor.

Study of laser induced temperature variation in silica nanofibers

After presenting a theoretical modelling based on the heat equation, we show two different experiments to measure the laser induced temperature variation in silica nanofibers in air, a direct one and an indirect one based on Brillouin scattering, leading to an estimated value of the convective parameter h.

Operating range of efficient Raman converters based on nanofibers immersed in different liquids

We present the operating range of Raman wavelength converters based on silica nanofibers immersed in liquids for the design of all fibered wavelength converters. This range is bounded on the lower limit by the pump energy necessary to reach the Raman threshold and on the upper limit by the laser induced breakdown of the nanofiber. These breakdown energies are measured in the ns regime for different liquids (water, ethanol, isopropanol) and for air. We finally define guidelines that open the way to a new family of low-cost compact and efficient all-fibered Raman converters that can be directly inserted in optical fibered networks with very low losses.

Continuous-wave generation of photon pairs in silica nanofibers using single-longitudinal- and multilongitudinal-mode pumps

In this paper, we describe experimental observation and characterization of emission of photon pairs through four-wave mixing (FWM) in a silica nanofiber, with high coincidence to accidental ratio (CAR, at best greater than 20 000 in the cw regime at pump power 24 mW and 40 000 in the pulsed regime at pump power \ensuremath{\approx}150 \ensuremath{\mu}W) and high pair emission rate (above 1 MHz in the pulsed regime with CAR around 100 at pump power \ensuremath{\approx}7 mW), despite residual presence of Raman spontaneous scattering (in the vicinity of the 12th silica Raman band) on the idler side. Moreover, these pairs of photons are observed with either a single-longitudinal-mode source or a multimode source (as well as a pulsed source) showing a factor of 2 increase of emission rate with the multimode source thanks to its random temporal fluctuation coupled to the quadratic response of FWM.

Cesium ion adsorption and desorption on electrospun mesoporous silica nanofibers immobilized with Prussian blue

To fabricate an efficient Cs ion adsorbent and prevent unexpected loss of Prussian blue (PB) colloidal particles during use, PB was immobilized on the surface of electrospun mesoporous silica nanofibers (MSFs) via a newly developed method of double exposure to Fe (III) ions. To introduce PB on MSFs, the MSFs were functionalized with ethylenediamine moiety to bind to Fe (III) ions, which would firmly anchor PB. MSFs were pretreated with Fe (III) ions and exposed to K4 [Fe(II) (CN)6] to form PB. We found that this process did not provide a sufficient PB amount on the MSFs. To increase the PB amount, after initial PB formation, the MSFs were treated with Fe (III) ions again so that the unreacted K4 [Fe(II) (CN)6] remaining on the MSFs could become PB. An investigation of the adsorption isotherms and kinetics of the nanofibrous adsorbent indicated that monolayer chemisorption had occurred. The maximum Cs ion adsorption capacity using the method of double exposure to Fe (III) ions was determined to be 14.66 mg/g, which was higher by a factor of 2.24 than the case that was not prepared by this method. Cs ions were selectively adsorbed over other cations and could be removed in both acidic and basic conditions, presumably because of the robust MSFs.

Solution Blow Spun Silica Nanofibers: Influence of Polymeric Additives on the Physical Properties and Dye Adsorption Capacity.

The physical properties of porous silica nanofibers are an important factor that impacts their performance in various applications. In this study, porous silica nanofibers were produced via solution blow spinning (SBS) from a silica precursor/polymer solution. Two polyvinylpyrrolidone (PVP, Mw = 360,000 and 1,300,000) were chosen as spinning aids in order to create different pore properties. The effect of their physical properties on the adsorption of methylene blue (MB) in an aqueous solution was explored. After forming, the nanofibers were calcined to remove the organic phase and create pores. The calcined nanofibers had a large amount of micro and mesopores without the use of additional surfactants. The molecular weight of the PVP impacted the growth of silica particles and consequently the pore size. High Mw PVP inhibited the growth of silica particles, resulting in a large volume of micropores. On the other hand, silica nanofibers with a high fraction of mesopores were obtained using the lower Mw PVP. These results demonstrate a simple method of producing blow spun silica nanofibers with defined variations of pore sizes by varying only the molecular weight of the PVP. In the adsorption process, the accessible mesopores improved the adsorption performance of large MB molecules.

Synthesis of PVA/SiO2 Nanofibers by Electrospinning Method for Supercapacitor Separators

In this research, polyvinyl alcohol (PVA)/silica nanofibers have been synthesized using electrospinning technique. Solutions of sodium silicate (Na2SiO3) in water and PVA flakes were blended and then processed by electrospinning method to obtain PVA/silica nanofibers. The effect of silica concentration on the resulting morphology and diameter of as-spun nanofibers were investigated by using scanning electron microscopy (SEM). The electrolyte uptake and retention of the as-spun nanofibers were measured. The silica concentration has an effect on the resulting nanofibers, where an increase in silica concentration resulted in a decrease on the diameter of the fibers. The manufactured nanofibers have an average diameter of 200-300 nm. The electrolyte uptake and retention values are also affected by the concentration of the silica in the electrospun solution, with the electrolyte uptake and retention values decreasing with the increase in silica concentration. The best values obtained are 151% for electrolyte uptake and 60% for electrolyte retention, which shows potential for PVA/silica nanofibers as an alternative material for supercapacitor separators.

Helical mesoporous organic–inorganic hybrid silica nanofibers prepared using a TPE-based silane for explosive detection

Helical mesoporous organic–inorganic hybrid silica nanofibers with blue fluorescence were synthesized by co-condensation of 1,2-bis(triethoxysilyl)ethane and tetraphenylethylene (TPE)-containing triethoxysilane with aggregation-induced emission (AIE) property. The pore channels of the hybrid silicas were arranged in a hexagonal structure. Lamellar mesopores were identified on the surfaces of the nanofibers. The fluorescence quantum yields increased with increasing the TPE weight ratio. These hybrid silicas exhibit sensitive fluorescence quenching responses towards the nitroaromaticexplosivepicric acid. This is ascribed to the ordered mesoporous structure which helps guest molecules to enter the pores quickly and interact with TPE chromophore.

Tailoring Nanonets‐Engineered Superflexible Nanofibrous Aerogels with Hierarchical Cage‐Like Architecture Enables Renewable Antimicrobial Air Filtration

AbstractPurification of pathogenic air has become an essential part of infection prevention and control. Most present air filters can hardly achieve excellent air filtration performance and the effective inactivation of the airborne pathogens at the same time. Herein, a bottom‐up approach is reported upon to construct cage‐like structured superflexible nanofibrous aerogels (CSAs) with renewable antimicrobial properties by combining electrospun silica nanofibers, bacterial cellulose nanofibers, and the hydrophobic SiOSi elastic binder. The following efficient grafting of N‐halamine compounds endows the CSAs with biocidal function. The resultant aerogels exhibit intriguing features of high porosity, hydrophobicity, superelasticity, foldability, renewable chlorination ability (>5400 ppm), high filtration performance toward PM0.3 (>99.97%, 189 Pa), and excellent antibacterial and antiviral activity (6 logs reduction within 5 min contact), enabling the aerogels to intercept and inactivate the pathogenic contaminants in air. The successful synthesis of CSAs provides a new possibility to design high‐performance air filtration materials for public health protection.

Laser-Induced Damage in Silica Nanofibers in Air and Immersed in Different Liquids in the Nanosecond Regime

Thanks to their unique optical properties, silica nanofibers are used in a growing number of applications. Moreover, the possibility of immerging them in various media adds another interesting feature to these devices. However, as for all optical components, nanofibers are limited by the optical damage that can be induced by a laser. In this Letter, we present for the first time to our knowledge Laser-Induced Damage Threshold (LIDT) measurements of silica nanofibers in air and in three common liquids (ethanol, isopropanol, and water). The experiments were performed in the nanosecond regime with a pump source emitting at the wavelength of 532 nm. Different nanofiber radii (from 220 nm to 450 nm) and two nanofiber lengths (2 cm and 8 cm) were tested. We firstly present the experimental setup and protocol. A significant number of samples were realized, and the results were highly repeatable. We also showed that immerging a nanofiber in a liquid substantially enhanced the LIDT, the most important increase having been obtained for nanofibers immersed in water for which the LIDT energy was almost multiplied by a factor of 2 compared with air ( 0.38 μJ in air vs 0.71 μJ in water for a radius of 350 nm). This property offers a new degree of freedom to widen the field of applications of nanofibers, where high peak powers are needed.

Surfactants assisted SiO2-Cu@Fe2O3 nanofibers: Ultra efficient photocatalyst for photodegradation of organic compounds and transesterification of waste edible oil to biodiesel

The researchers are trying to synthesize such materials which have desirable stability, high efficiency and cost effective. In the present work, SiO 2 -Cu@Fe 2 O 3 nanofibers were synthesized by a novel protocol in which tween-80 and cetyltrimethylammonium bromide was used as a surfactant. The photodegradation of dyes and transesterification of waste edible oil to biodiesel had been investigated. Copper nanoparticles were relatively well dispersed over the surfaces of silica and iron oxide nanofibers with the diameter of 20 nm and Fe 2 O 3 and SiO 2 composite mesopores with a high specific surface area (116 m 2 /g). Photocatalytic degradation of Methylene blue (MB) and rhodamine B (Rhod B) dyes has been tested against As-synthesized SiO 2 -Cu@Fe 2 O 3 nanostructures. At optimum processing conditions SiO 2 -Cu@Fe 2 O 3 displayed a far higher effectiveness of reaction and dyes degradation than many others. A comparative kinetic study of the reduction of dyes (MB and Rhod B) in the presence and absence of nanocatalyst shows the efficiency of synthesized SiO 2 -Cu@Fe 2 O 3 . Furthermore, the reusability of the as-prepared composite was measured and there is no considerable catalytic activity loss even after 5 cycles. The efficiency of SiO 2 -Cu@Fe 2 O 3 was tested both in light and dark. The visible light efficiency of SiO 2 -Cu@Fe 2 O 3 nanofibers against the said dyes were several time higher than in dark. The degradation patterns at a temperature range of 30 °C were so well equipped with a 1st order kinetic framework and proposed a dyes reaction mechanism. The synthesized nanofibers were also applied as a catalyst against transesterification of waste edible oil to biodiesel. The results indicated that 98% biodiesel production was obtained in a 7 h reaction time, and 70 °C reaction temperature. On the basis of the above high efficiency further research is required on the said nanofibers to investigate their hidden applications. • Preparation of SiO 2 -Cu@Fe 2 O 3 nanofibers by new method. • Photocatalytic​ degradation of methylene blue and Rhodamine B. • Catalytic conversion of waste edible oil to biodiesel. • Investigated different factors effecting the catalytic activity.

Long-term optical transmittance measurements of silica nanofibers

Optical nanofibers are highly attractive tools that are used in an increasing number of applications. However, at these radii typically smaller than the wavelength, the optical field is highly sensitive to dusts that rapidly degrade the optical transmittance, which is an issue for their use and storage. In this work we propose and characterize simple and efficient solutions. The chosen nanofiber radius is 500 nm. Firstly, we make systematic and long-term measurements (over several months) of nanofiber optical transmittance at 1.5 μm in two protected environments that can be easily found in almost any laboratory and differing by their levels of cleanliness. We show that the rate of decrease of the optical transmittance is very low when the nanofiber is put in a simple protection box and ten times lower when the nanofiber is put in an airtight box. Secondly, the repetition of these measurements gives a mean value of this rate of −5.2 × 10−2%/day in the protection box and −6.3 × 10−3%/day in the airtight box. Thirdly, we perform the optical transmittance measurements on two nanofiber lengths (2 cm and 7 cm) and show that there is no significant difference on the rate of degradation between the two lengths. These results also enable to predict the value of the optical transmittances after several months or even years, which is a key parameter for most of the applications using nanofibers.

Electrospun mesoporous silica nanofibers decorated with titanium dioxide nanoparticles for a repeatable photocatalysis

Mesoporous silica nanofiber (MSFs) were used as support material for TiO2 to fabricate nanofibrous photocatalysts for more versatile use of colloidal TiO2 nanoparticles. The MSFs were prepared by electrospinning and TiO2 nanoparticle were successfully introduced onto the MSF surface (MSF-TiO2) through a sol-gel reaction with the TiO2 precursor. The MSF-TiO2 retained the mesoporous structure and showed a large specific surface area. The combined effects of adsorption and photodegradation of methylene blue (MB) dye were investigated to determine the total removal performance of MSF-TiO2. MSF-TiO2 was found to efficiently remove MB through both effects. It should be noted that repeated use of MSF-TiO2 after regeneration was possible mainly because of the supported nanofibers. In addition, MSF-TiO2 was successfully used as a photocatalyst in the oxidative coupling of benzylamine. The MSF photocatalyst having a large specific surface area is a promising candidate for use in various applications, because it can be easily separated and recovered, and it also presents a high catalytic activity.

Energy Dissipation and Asymmetric Excitation in Hybrid Waveguides for Routing and Coloring.

The delivery of optical signals from an external light source to a nanoscale waveguide is highly important for the development of nanophotonic circuits. However, the efficient coupling of external light energy into nanophotonic components is difficult and still remains a challenge. Herein, we use an external silica nanofiber to light up an organic-inorganic hybrid nanowaveguide, namely, a system composed of a polymer filament doped with MoS2 quantum dots. Nanofiber-excited nanowaveguides in a crossed geometry are found to asymmetrically couple excitation signals along two opposite directions, with different energy dissipation resulting in different colors of the light emitted by MoS2 quantum dots and collected from the waveguide terminals. Interestingly, rainbow-like light in the hybrid waveguide is achieved by three-in-one mixing of red, green, and blue components. This heterodimensional system of dots in waveguide represents a significant advance toward all-optical routing and full-color display in integrated nanophotonic devices.

Electrospinning synthesis of porous boron-doped silica nanofibers for oxidative dehydrogenation of light alkanes

The discovery of the high activity and selectivity of boron-based catalysts for oxidative dehydrogenation (ODH) of alkanes to olefins has attracted significant attention in the exploration of a new method for the synthesis of highly active and selective catalysts. Herein, we describe the synthesis of porous boron-doped silica nanofibers (PBSNs) 100–150 nm in diameter by electrospinning and the study of their catalytic performance. The electrospinning synthesis of the catalyst ensures the uniform dispersion and stability of the boron species on the open silica fiber framework. The one-dimensional nanofibers with open pore structures not only prevented diffusion limitation but also guaranteed high catalytic activity at high weight hourly space velocity (WHSV) in the ODH of alkanes. Compared to other supported boron oxide catalysts, PBSN catalysts showed higher olefin selectivity and stability. The presence of Si−OH groups in silica-supported boron catalysts may cause low propylene selectivity during the ODH of propane. When the ODH conversion of ethane reached 44.3%, the selectivity and productivity of ethylene were 84% and 44.2% gcat−1 s−1, respectively. In the case of propane ODH, the conversion, selectivity of olefins, and productivity of propylene are 19.2%, 90%, and 76.6 μmol gcat−1 s−1, respectively. No significant variations in the conversion and product selectivity occurred during 20 h of operation at a high WHSV of 84.6 h−1. Transient analysis and kinetic experiments indicated that the activation of O2 was influenced by alkanes during the ODH reaction.

Reed Leaves Inspired Silica Nanofibrous Aerogels with Parallel-Arranged Vessels for Salt-Resistant Solar Desalination.

Sufficient and clean freshwater is still out of reach for billions of people around the world. Solar desalination from brine is regarded as one of the most promising proposals to solve this severe crisis. However, most of the reported evaporators to date still suffer from the decreasing evaporation rate caused by salt crystallization accumulated on their surface. Here, inspired by the vascular tissue structure, transpiration, and antifouling function of reed leaves, we design biomimetic hierarchical nanofibrous aerogels with parallel-arranged vessels and hydrophobic surfaces for highly efficient and salt-resistant solar desalination. Foldable vessel walls and flexible silica nanofibers give the reed leaf-inspired nanofiber aerogels (R-NFAs) excellent mechanical properties and enable them to withstand repeated compression. Besides, the R-NFAs can efficiently absorb sunlight (light absorption efficiency: 94.8%) and evaporate the brine to vapor, similar to reed leaves (evaporation rate: 1.25 kg m-2 h-1 under 1 sun). More importantly, enabled by the hydrophobic surfaces and parallel-arranged vessels, the R-NFAs can work stably in high-concentration brine (saturated, 26.3 wt %) under high-intensity light (up to 6 sun), demonstrating potent salt resistance. It is expected that R-NFAs with combined antisalt pore and surface structures will provide a designed concept for salt-resistant solar desalination.