The optical properties of PVA/TiO2 composite nanofibers

The electrospun nanofibers emerge several advantages because of extremely high specific surface area and small pore size. This work studies the effect of PVA nanofibers diameter and nano‐sized TiO₂ on optical properties as reflectivity of light and color of a nanostructure assembly consisting polyvinyl alcohol and titanium dioxide (PVA/TiO₂) composite nanofibers prepared by electrospinning technique. The PVA/TiO₂ composite spinning solution was prepared through incorporation of TiO₂ nanoparticles as inorganic optical filler in polyvinyl alcohol (PVA) solution as an organic substrate using the ultrasonication method. The morphological and optical properties of collected composites nanofibers were highlighted using scanning electron microscopy (SEM) and reflective spectrophotometer (RS). The reflectance spectra indicated the less reflectance and lightness of composite with higher nanofiber diameter. Also, the reflectance and lightness of nanofibers decreased with increasing nano‐TiO₂ concentration. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphology enhancement of TiO2/PVP composite nanofibers based on solution viscosity and processing parameters of electrospinning method

In this work, different sol solutions with various titanium tetraisopropoxide (TIP)/glacial acetic acid ratios in 2‐propanol with 5 wt % poly(vinyl pyrrolidone) (PVP) (M_w = 360,000 g/mol) were prepared and electrospun. Composition of the prepared sols and as‐spun TiO₂/PVP nanofibers were determined by Fourier transform infrared and Raman spectroscopy methods. Morphology of the electrospun TiO₂/PVP nanofibers was studied by scanning electron microscopy and transmission electron microscopy (TEM) techniques. Rheometry measurements of the sol solutions showed decrease of viscosity upon the addition of TIP to the polymer solutions with constant polymer and acid concentrations. The sol solution having the lowest viscosity (at shear rate 10 s^?1) but the highest TIP/glacial acetic acid ratio showed beaded nanofibers morphology when electrospun under 10 and 12 kV applied voltage while injection rate, needle tip to collector distance, and needle gauge were kept constant. However, smooth electrospun TiO₂/PVP composite nanofibers with the average nanofibers diameters (148 ± 79 nm) were achieved under the same condition when applied voltage increased to 15 kV. TEM micrographs of the electrospun TiO₂/PVP nanofiber showed that the TiO₂ particles with continuous structure are formed at the middle of the nanofiber and distributed along its axis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46337.     

Studies on the synthesis of electrospun PAN‐Ag composite nanofibers for antibacterial application

We have successfully synthesized polyacrylonitrile (PAN) nanofibers impregnated with Ag nanoparticles by electrospinning method at room temperature. Briefly, the PAN‐Ag composite nanofibers were prepared by electrospinning PAN (10% w/v) in dimethyl formamide (DMF) solvent containing silver nitrate (AgNO₃) in the amounts of 8% by weight of PAN. The silver ions were reduced into silver particles in three different methods i.e., by refluxing the solution before electrospinning, treating with sodium borohydride (NaBH₄), as reducing agent, and heating the prepared composite nanofibers at 160°C. The prepared PAN nanofibers functionalized with Ag nanoparticles were characterized by field emission scanning electron microscopy (FESEM), SEM elemental detection X‐ray analysis (SEM‐EDAX), transmission electron microscopy (TEM), and ultraviolet‐visible spectroscopy (UV‐VIS) analytical techniques. UV‐VIS spectra analysis showed distinct absorption band at 410 nm, suggesting the formation of Ag nanoparticles. TEM micrographs confirmed homogeneous dispersion of Ag nanoparticles on the surface of PAN nanofibers, and particle diameter was found to be 5–15 nm. It was found that all the three electrospun PAN‐Ag composite nanofibers showed strong antibacterial activity toward both gram positive and gram negative bacteria. However, the antibacterial activity of PAN‐Ag composite nanofibers membrane prepared by refluxed method was most prominent against S. aureus bacteria. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Facile Fabrication of TiO2/SrTiO3 Composite Nanofibers by Electrospinning for High Efficient H2 Generation

Using electrospinning, specially prepared Ti and Sr precursor TiO₂/SrTiO₃ composite nanofibers were successfully fabricated. This would ensure the close and uniform contact between TiO₂ and SrTiO₃, which significantly contributes to the electrons transfer at the interface between the two semiconductors with different band gaps. Meanwhile, the long fibrous structure of TiO₂/SrTiO₃ composite nanofibers would further ease the electron transfer, enlarge the specific surface area, and enhance the light absorption capability thus leading to the improvement of photocatalytic efficiency. Because of the above‐mentioned advantages, the TiO₂/SrTiO₃ composite nanofibers exhibited higher photocatalytic H₂ generation efficiency over bare TiO₂ nanofibers in a water/methanol sacrificial reagent system under the irradiation of UV light.     

Preparation of novel nano/submicrofiber catalyst containing nano‐TiO2 particles

A novel Nano/submicrofiber catalyst was prepared via electrospinning technology from poly (vinyl pyrrolidone) (PVP) and nano‐TiO₂. First, nano‐TiO₂ particles were added into the mixture of ethanol and deionized water, the mass ratio of ethanol and deionized water was 1 : 1, the TiO₂ suspension was obtained after 1 h with ultrasonic treatment and centrifugal effect, Then PVP was added into the above‐mentioned suspension and the content of PVP in the sol was 28%. The TiO₂/PVP solution was electrospun with different voltage. The effects of the content of TiO₂ and electrospinning voltage on diameter of nano/submicrofiber were studied. The nano/submicrofiber catalyst was characterized by scanning electron microscopy, transmission electron microcopy, X‐ray diffraction, and Fourier transform infrared. The results show that the diameter of nano/submicrofiber increases with an increase of the content of nano‐TiO₂ and decreases with the increase of electrospinning voltage. The analytical result showed that the nano‐TiO₂ particles were well dispersed in the matrix of PVP, moreover, the crystal type of nano‐TiO₂ was a mixture of anatase and rutile and the diameter of nano‐TiO₂ particles in the nano/submicrofiber is in the range of 20–60 nm and the nano‐TiO₂ particle was monodisperse, and the nano‐TiO₂ particle and PVP molecule was connected by a hydrogen bonding. This nano/submicrofiber catalyst has a high efficiency on degradation on CH₂O. 56.8 percent of CH₂O was degraded under ultraviolet radiation in 80 min when the content of nano‐TiO₂ is 20% in nano/submicrofibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and characterization of wollastonite/titanium oxide nanofiber bioceramic composite as a future implant material

In this study, novel composites consisting of electrospun titanium dioxide (TiO₂) nanofibers incorporated into high-purity wollastonite glass ceramics were prepared as materials for use in hard tissue engineering applications. These materials were characterized and investigated by means of physical, mechanical and in vitro studies. The proposed composite showed greater densification and better mechanical characteristics compared to pure wollastonite. The influence of densification temperature and TiO₂ content was investigated. Typically, TiO₂/wollastonite composites having 0, 10, 20 and 30 wt% metal oxide nanofibers were sintered at 900, 1100 and 1250 °C. The results indicated that increasing TiO₂ nanofibers content leads to increase the bulk density, compressive strength and microhardness with negligible, high and moderate influence for the densification temperature, respectively. While porosity and water adsorption capacity decreased with increasing the metal oxide nanofibers with a considerable impact for the sintering temperature in both properties. Moreover, bone-like apatite formed on the surface of wollastonite and wollastonite/TiO₂ nanofibers soaked in simulated body fluid (SBF). All these results show that the inclusion of TiO₂ nanofibers improved the characteristics of wollastonite while preserving its in vitro bioactivity; hence, the proposed composite may be used as a bone substitute in high load bearing sites.     

Effect of nanoclay on the thermal,mechanical, and crystallization behavior of nanofiber webs of nylon‐6

Nylon‐6 and nanoclay/nylon‐6 composite nanofibers were prepared by electrospinning technique, in which formic acid was used as a solvent for good solubility of nylon‐6. The diameter of nylon‐6 and nanoclay/nylon‐6 nanofibers was below 350 nm and had smooth surfaces. The DSC heating curves of nylon‐6 and composites nanofibers show two endotherm behaviors, T_m1 (about 214°C) and T_m2 (about 220°C), corresponding to the melting events of γ‐form and α‐form crystals, respectively. The WAXs study showed that the γ‐crystalline phase predominantly present in both nylon‐6 and nanoclay/nylon‐6 nanofibers. The mechanical properties of the nanoclay/nylon‐6 composite nanofibers were higher than neat nylon‐6 electrospun nanofibers, which was decreased as the quantity of the clay increased. It might be due to the aggregation of nanoclay at high concentration. The thermal properties of the composite nanofibers were higher than neat nylon‐6 nanofibers. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Solid‐state synthesis and characterization of polyaniline/nano‐TiO2 composite

Polyaniline/nano‐TiO₂ composites with the content of nano‐TiO₂ varying from 6.2 wt % to 24.1 wt % were prepared by using solid‐state synthesis method at room temperature. The structure and morphology of the composites were characterized by the Fourier transform infrared (FTIR) spectra, ultraviolet‐visible (UV–vis) absorption spectra, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical performances of the composites were investigated by galvanostatic charge–discharge measurement, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results from FTIR and UV–vis spectra showed that the composites displayed higher oxidation and doping degree than pure PANI. The XRD and morphological studies revealed that the inclusion of nano‐TiO₂ particles hampered the crystallization of PANI chains in composites, and the composites exhibited mixed particles from free PANI particles and the nano‐TiO₂ entrapped PANI particles. The galvanostatic charge–discharge measurements indicated that the PANI/nano‐TiO₂ composites had higher specific capacitances than PANI. The composite with 6.2 wt % TiO₂ had the highest specific capacitance among the composites. The further electrochemical tests on the composite electrode with 6.2 wt % TiO₂ showed that the composite displayed an ideal capacitive behavior and good rate ability. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

In situ polymerized nanocomposites of poly(butylene succinate)/Tio2 nanofibers: molecular weight,morphology, and thermal properties

In this study, the nanocomposites of poly(butylene succinate) (PBS) and TiO₂ nanofibers were first synthesized via in situ polymerization. Molecular weight, morphology, and thermal properties of the nanocomposites were characterized. As the weight percentage of TiO₂ nanofibers increased from 0 to 2%, the molecular weight of PBS in the nanocomposites decreased gradually compared with that of pure PBS. In morphology, the nanocomposites were constituted by free PBS and PBS‐grafted TiO₂ nanofibers (PBS‐g‐TiO₂), which were proved by the Fourier transform infrared, scanning electron microscopy (SEM), and transmission electron microscopy. In addition, the SEM demonstrated the strong interfacial interaction and homogeneous distribution between TiO₂ nanofibers and PBS matrix. The thermal properties determined by differential scanning calorimetry and thermogravimetric analysis included the increasing of cold crystallization temperatures, the melting temperatures, and the thermal stability. Besides, the crystallinity and the rate of crystallization of the nanocomposites were enhanced, which were also observed by the X‐ray diffraction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Magnetic‐field‐assisted electrospinning highly aligned composite nanofibers containing well‐aligned multiwalled carbon nanotubes

Composite nanofiber meshes of well‐aligned polyacrylonitrile (PAN)/polyvinylpyrrolidone (PVP) nanofibers containing multiwalled carbon nanotubes (MWCNTs) were successfully fabricated by a magnetic‐field‐assisted electrospinning (MFAES) technology, which was confirmed to be a favorable method for preparation of aligned composite nanofibers in this article. The MFAES experiments showed that the diameters of composite nanofibers decreased first and then increased with the increase of voltage and MWCNTs content. With the increase of voltage, the degree of alignment of the composite nanofibers decreased, whereas it increased with increasing MWCNTs concentration. Transmission electron microscopy observation showed that MWCNTs were parallel and oriented along the axes of the nanofibers under the low concentration. A maximum enhancement of 178% in tensile strength was manifested by adding 2 wt % MWCNTs in well‐aligned composite nanofibers. In addition, the storage modulus of PAN/PVP/MWCNTs composite nanofibers was significantly higher than that of the PAN/PVP nanofibers. Besides, due to the highly ordered alignment structure, the composite nanofiber meshes showed large anisotropic surface resistance, that is, the surface resistance of the composite nanofiber films along the fiber axis was about 10 times smaller than that perpendicular to the axis direction. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41995.     

Fabrication and Properties of Electrospun PAN/LA–SA/TiO2 Composite Phase Change Fiber

A stabilized matrix to accommodate phase change materials is essential in the application and functioning of phase change materials. In this study, lauric–stearic acid eutectics and TiO₂ were doped with polyacrylonitrile solution to electrospin a composite phase change nanofibers. The surface morphology indicated typical nanofibrous structure of polyacrylonitrile/lauric–stearic/TiO₂ composite nanofibers, and the diameter of fiber increased with the increase in lauric–stearic eutectic mass ratio. Differential scanning calorimetry analysis showed the temperature of melting peak of polyacrylonitrile/lauric–stearic/TiO₂ nanofiber was around 25°C, which was lower than that of pure lauric–stearic eutectics. Latent heat value of the composite fibers gradually increased with the increase in lauric–stearic mass ratio. Thermal cycle test and thermogravimetric analysis showed that polyacrylonitrile/lauric–stearic/TiO₂ composite fibers were reversible thermal energy storage materials with good thermal stability below 100°C.     

Electrospinning silica/polyvinylpyrrolidone composite nanofibers

Small diameter nanofibers of silica and silica/polymer are produced by electrospinning silica/polyvinylpyrrolidone (SiO₂/PVP) mixtures composed of silica nanoparticles dispersed in polyvinylpyrrolidone solutions. By controlling various parameters, 380 ± 100 nm diameter composite nanofibers were obtained with a high silica concentration (57.14%). When the polymer concentration was low, “beads‐on‐a‐string” morphology resulted. Nanofiber morphology was affected by applied voltage and relative humidity. Tip‐to‐collector distance did not affect the nanofiber diameter or morphology, but it did affect the area and thickness of the mat. Heat treatment of the composite nanofibers at 200°C crosslinked the polymer yielding solvent‐resistant composite nanofibers, while heating at 465°C calcined and selectively removed the polymer from the composite. Crosslinking did not change the nanofiber diameter, while calcined nanofibers decreased in diameter (300 ± 90 nm) and increased in surface area to volume ratio. Nanofibers were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40966.     

Photocatalytic activities of electrospun tin oxide doped titanium dioxide nanofibers

SnO₂ doped TiO₂ electropsun nanofiber photocatalysts were successfully prepared by means of electrospinning process. The surface morphology, structure and optical properties of the resultant products were characterized by field-emission electron microscopy (FE-SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), UV–vis spectroscopy, photoluminescence (PL) and cathodoluminescence (CL) techniques. The utilized physiochemical analyses indicated that the introduced SnO₂ doped TiO₂ nanofibers have a smooth surface and uniform diameters along their lengths. The photocatalytic performance of the composite nanofibers was tested for degradation of methylene blue (MB) and methyl orange (MO) dye solution under ultraviolet (UV) irradiation. Under the UV irradiation, the photocatalytic reaction rate in case of utilizing SnO₂-doped TiO₂ nanofibers was rapidly increased than that of the pristine TiO₂ nanofibers. Overall, this study demonstrates cheap, stable and effective material for photocatalytic degradation at room temperature.     

Co‐electrospun composite nanofibers of blends of poly[(amino acid ester)phosphazene] and gelatin

Electrospinning is known as a simple and effective fabrication method to produce polymeric nanofibers suitable for biomedical applications. Many synthesized and natural polymers have been electrospun and reported in the literature; however, there is little information on the electrospinning of poly[(amino acid ester)phosphazene] and its blends with gelatin. Composite nanofibers were made by co‐dissolving poly[(alaninoethyl ester)_0.67(glycinoethyl ester)_0.33phosphazene] (PAGP) and gelatin in trifluoroethanol and co‐electrospinning. The co‐electrospun composite nanofibers from different mixing ratios (0, 10, 30, 50, 70 and 90 wt%) of gelatin to PAGP consisted of nanoscale fibers with a mean diameter ranging from approximately 300 nm to 1 µm. An increase in gelatin in the solution resulted in an increase of average fiber diameter. Transmission electron microscopy and energy dispersive X‐ray spectrometry measurements showed that gelatin core/PAGP shell nanofibers were formed when the content of gelatin in the hybrid was below 50 wt%, but homogeneous PAGP/gelatin composite nanofibers were obtained as the mixing ratios of gelatin to PAGP were increased up to 70 and 90 wt%. The study suggests that the interaction between gelatin and PAGP could help to stabilize PAGP/gelatin composite fibrous membranes in aqueous medium and improve the hydrophilicity of pure PAGP nanofibers. Copyright © 2009 Society of Chemical Industry     

Photocatalytic Deposition of Silver Nanoparticles onto Organic/Inorganic Composite Nanofibers

Summary: In this work, silver nanoparticles were embedded in electrospun organic/inorganic composite nanofibers consisting of PAN and TiO₂ through photocatalytic reduction of the silver ions in silver nitrate solutions under UV irradiation. The morphology and diameter of PAN/TiO₂ composite nanofibers could be controlled by varying the initial contents of TiO₂ in the spinning solution. From TEM images and UV‐Vis spectra, it has been confirmed that monodisperse silver nanoparticles with a diameter of ≈2 nm were deposited selectively upon the titania of the as prepared composite nanofibers. The amount of Ag nanoparticles embedded on composite nanofibers was greatly influenced by the amount of TiO₂ in composite nanofibers, reflecting the role of titania as the inorganic stabilizer and photocatalyst.

Morphology of silver nanoparticles embedded on PAN/TiO₂ composite nanofibers.     

Study of the effect of rutile/anatase TiO2 nanoparticles synthesized by hydrothermal route in electrospun PVA/TiO2 nanocomposites

Mixed rutile–anatase TiO₂ nanoparticles were synthesized by hydrothermal treatment under acidic conditions and incorporated into poly(vinyl alcohol) (PVA). These nanocomposites were electrospun to produce nanofibers of PVA/TiO₂, which were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The photocatalytic degradation of Rhodamine B and degradation of the polymer by UV‐C lamps were also investigated. The results showed that TiO₂ nanoparticles did not change the morphology and thermal behavior of the nanofiber polymer, but were effective in modifying the UV absorption of PVA without reducing its stability. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Solar reflectance,surface adhesion,and thermal conductivity of wood/natural rubber composite sheet with Tio2/polyurethane topcoat for roofing applications

Effects of titanium dioxide (TiO₂) dosage in polyurethane (PU) coating and PU coating thickness on solar reflectance, surface adhesion, crack resistance to bending, and thermal conductivity of wood/(natural rubber) (WNR) composite sheet were studied before and after prolonged UV aging. The TiO₂ powder content added to the PU coating was varied from 0 to 15 parts per hundred parts of PU. The average PU coating thickness on the WNR composite sheet was altered from 127 ± 10 to 315 ± 10 μm. The experimental results suggested that the solar reflectance slightly increased with increasing TiO₂ powder but did not change upon varying the PU coating thicknesses. The presence of TiO₂ in the PU coating caused a slight decrease in thermal conductivity because of porosities occurring due to the presence of voids, but increasing the TiO₂ powder content in the coating resulted in a progressive increase in thermal conductivity of the composite sheet. In a UV‐accelerated weathering tester (UVB 313 nm), the lightness of the PU coating slightly increased owing to PU discoloration, whereas the solar reflectance, PU/WNR layer adhesion, and crack resistance to bending remained unaffected with increasing UV aging time. J. VINYL ADDIT. TECHNOL., 18:184–191, 2012. © 2012 Society of Plastics Engineers     

Anionic nylon 6/TiO2 composite materials: Effects of TiO2 filler on the thermal and mechanical behavior of the composites

The nylon 6‐based composite materials containing untreated and surface‐treated TiO₂ particles with 3‐aminopropyltriethoxysilane (APTEOS), as coupling agent were prepared by in situ anionic polymerization of ε‐caprolactam in the presence TiO₂ as a filler using the rotational molding technique. The thermal behavior and mechanical properties of the neat nylon 6 and its composites were investigated using various techniques such as differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), a tensile and flexural test and impact strength. Experimental results revealed that both untreated and surface‐modified TiO₂ had distinct influence on the melting temperature (T_m), crystallization temperature (T_c), and degree of crystallinity (α_DSC), thermal stability, storage modulus (E′), and loss factor (tan δ), and mechanical properties of nylon 6 matrix. Dynamical mechanical analysis indicated that addition of TiO₂ particles into nylon 6 matrix increased both the storage modulus and the glass transition temperature. The corresponding values of nylon 6 composites with modified filler were higher than that of nylon 6 composite with untreated TiO₂ particles. Tensile and flexural characteristics of the nylon 6 composites were found to increase while the elongation at break and impact strength with increase in TiO₂ concentration relative to neat nylon 6. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Effect of calcination temperature of TiO2 on the crystallinity and the permittivity of PVDF‐TrFE/TiO2 composites

Composite membranes of poly(vinylidene‐trifluoroethylene)/titanium dioxide (PVDF‐TrFE/TiO₂) were prepared by the solution cast method. The crystallization behavior and dielectric properties of the composites with TiO₂ calcined at different temperatures were studied. Transmission electron microscopy and X‐ray diffraction (XRD) results showed that the TiO₂ nanoparticles calcined at different temperatures were well dispersed in the polymer matrix and did not affect the structure of the PVDF‐TrFE matrix. XRD and differential scanning calorimeter measurements showed that the crystallinity of PVDF‐TrFE/TiO₂ composites increased as the addition of TiO₂ with different calcination temperatures. The dielectric property testing showed that the permittivity of PVDF‐TrFE/TiO₂ membrane increased rapidly with the increase of TiO₂ content and the calcination temperature of TiO₂ at constant TiO₂ content, but the dielectric loss did not change much. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

PPV/TiO2 hybrid composites prepared from PPV precursor reaction in aqueous media and their application in solar cells

In this work, poly(phenylene vinylene) (PPV) and TiO₂ nanocomposites containing different amounts of TiO₂ were prepared through PPV precursor reaction in aqueous media. The TiO₂ components were introduced into the systems by two methods, i.e. through in situ sol-gel reaction or by mixing commercially available TiO₂ nanoparticles with the PPV precursor before reaction. The composite prepared by mixing commercially available TiO₂ nanoparticles shows perfect crystal character of the anatase TiO₂, but TiO₂ particles severely agglomerate in the PPV matrix. The composite prepared by introducing TiO₂ nanoparticles through the sol-gel reaction shows uniform nanoscale dispersion of anatase TiO₂ in PPV matrix. The UV-vis and FL spectroscopic analyses confirm the formation of the TiO₂/PPV composites and reveal the enhanced PL quenching effect as the TiO₂ content increases. The PPV/TiO₂ composites can show significant photovoltaic response. Better photovoltaic performance is observed for the solar cells prepared by using the in situ sol-gel reaction method.