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Flexible intelligent response devices are fabricated using several matrix materials. Among these, bacterial cellulose (BC) exhibits higher crystalline characteristics along with a higher degree of polymerization, elastic modulus, tensile strength, and water absorption. In this study, to further increase the response of fiber-based materials and expand their wearable applications, BC-based Janus fibers are prepared via wet spinning and used as fibrous intelligent response materials driven under photothermal stimulation. The BC-based Janus fibers exhibited excellent photothermal response with hydrophilic graphene oxide (GO)/BC as the actuation layer and hydrophobic graphene/BC as the supporting layer. When an infrared light was used to stimulate the GO side, the resulting dehydration and contraction of the GO side drove deformation. When the infrared stimulus was removed, the BC and GO quickly absorbed water and expanded owing to their favorable water-absorption properties. The material recovered its original straight shape, achieving reversible deformation. The experiment showed that the fibers prepared with 35 wt% GO and 100 wt% graphene exhibited a superior photothermal actuation performance compared to the BC fibers, GO/BC fibers, and graphene/BC fibers. When the actuation layer was exposed to infrared light for 27 s, the fibers started to bend upward along the illuminated section. After 55 s of exposure, the bending angle reached 135°. After the infrared light was turned off, the bent fibers returned to their original straight shape. [ABSTRACT FROM AUTHOR]

Recently, stretchable and wearable health monitoring equipment has greatly improved human's daily life, which sets higher demands for portable power source in stretchability, sustainability, and biocompatibility. In this work, we proposed a stretchable triboelectric nanogenerator (TENG) based on stretchable poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/porous carbon hybrid for oxyhemoglobin saturation (SpO2) monitoring. To combine advantages of carbon material for its high conductivity and organic electrode for its high stretchability, we spin-coated a solution of PEDOT:PSS/porous carbon onto a plasma-treated pre-stretched Ecoflex film to fabricate a stretchable electrode with rough surface. Due to its roughness and high potential difference with the dielectric material, the stretchable-electrode-based TENG exhibited better performance compared to the pristine TENG based on carbon or PEDOT:PSS material. The output voltage and current reached up to 51.5 V and 13.2 µA as the carbon concentration increased. More importantly, the performance further increased under large strain (100%) which is suitable for wearable systems. Finally, the device demonstrated its application potential for powering a flexible blood oxygen monitor. This simple and cost-effective method can enhance the stretchability and stability of organic/inorganic electrode-based TENG, which paves the development of high-performance stretchable TENG. [ABSTRACT FROM AUTHOR]

The flexible nitrogen (N) doped TiO2/C nanofibrous film (NTCf) was fabricated by a combination of electrospinning and annealing treatment. The BET surface area of the NTCf increases, reaches largest value, and then decreases slightly with increasing of N. And the NTCf-20 has a maximum BET surface area of 175.60 m2·g−1. These are beneficial to the absorption of dye by the photocatalyst. At the same time, the N doping could increase the light absorption of TiO2 and is favorable to the charges transfer of the carbon nanofibers, resulting in improving the photocatalytic activity of NTCf under visible light. As a result, all the NTCf showed excellent photocatalytic performance. Moreover, with the increase of N concentration, the photocatalytic activity of the NTCf increased, reaching the largest value before decreasing. And the highest photocatalytic degradation efficiency of Rhodamine B (RhB) was about 99.1% for 1 h by using NTCf-20. After that, the NTCf film was stuck on organza fabric to form a photocatalytic fabric by hot pressing. And the photocatalytic fabric with degradation efficiency of 98.5% was easily separated from the dye solution and possessed excellent reusability. It has huge potential application in pollutant disposal in flowing water. [ABSTRACT FROM AUTHOR]

ZnO/carbon-TiO2 core-sheath nanofibrous film was fabricated by a combination of electrospinning, tetrabutyl titanate (TBT) treatment and heated treatment. The results of field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction revealed that the wurtzite ZnO nanoparticles were successfully incorporated in carbon nanofibers (NFs) matrix without aggregation. And a uniform TiO2 layer consisting of anatase and rutile covered on the surface of the ZnO/C NFs. The ZnO/C-TiO2 core-sheath NFs film was used to photodegrade rhodamine B and exhibited the photocatalytic efficiency of 98.8%, which was much higher than that of ZnO NFs and ZnO/C NFs. This might be attributed to the ZnO/C-TiO2 core-sheath structure with high separation efficiency of photo-generated electrons and holes. Moreover, ZnO/C-TiO2 core-sheath NFs could be easily recycled without decrease of photocatalytic activity. [ABSTRACT FROM AUTHOR]

A facile strategy for synthesizing MnCo2O4/carbon (MCO/C) composite nanofibers is introduced in this work, in which MCO nanoparticles with an average size of about 40 nm are distributed uniformly in carbon nanofiber matrix by electrospinning and subsequent heat treatment. When adopted as anode for lithium-ion batteries (LIBs), MCO/C exhibits better lithium storage capabilities in comparison with bare MCO. The initial discharge/charge capacity of MCO/C is up to 1484/1140 mAh g−1 and can maintain a stable capacity of 933 mAh g−1 at 100 mA g−1 over 200 cycles. Meanwhile, a reversible capacity of 500 mAh g−1 can be retained even at a high current density of 2 A g−1 after 1000 long cycles. The superior electrochemical properties are mainly resulted from the conductive carbon matrix which can not only promote electron transfer but also act as a buffer to alleviate volume change of MCO during the lithiation/delithiation process. It is demonstrated that MCO/C nanofiber can be used as prospective anode materials for LIBs. [ABSTRACT FROM AUTHOR]

The eight kinds of fatty acid binary and ternary eutectics such as capric–lauric acid (CL), capric–myristic acid (CM), capric–palmitic acid (CP), capric–stearic acid (CS), capric–lauric–palmitic acid (CLP), capric–myristic–palmitic acid (CMP), capric–myristic–stearic acid (CMS), and capric–palmitic–stearic acid (CPS) were selected as solid–liquid PCMs in this paper. The innovative electrospun fatty acid binary eutectic/polystyrene/fatty acid ternary eutectic (i.e., CL/PS/CLP, CM/PS/CLP, CP/PS/CLP, CS/PS/CLP, CL/PS/CMS, CM/PS/CMS, CP/PS/CMS, CS/PS/CMS, CL/PS/CPS, CM/PS/CPS, CP/PS/CPS and CS/PS/CPS) and fatty acid ternary eutectic/polystyrene/fatty acid ternary eutectic (i.e., CLP/PS/CMP, CLP/PS/CMS, CLP/PS/CPS, CMP/PS/CMS, CMP/PS/CPS and CMS/PS/CPS) form-stable phase change composite fibrous membranes (PCCFMs) were fabricated by co-electrospinning. The morphological structure, phase change temperatures, and enthalpies were investigated by scanning electron microscope (SEM) and differential scanning calorimetry (DSC), respectively. The SEM images showed that the PS-based phase change composite fibers were collected to form form-stable PCCFMs with the average fiber diameter of about 335–640 nm. The DSC analysis indicated that the melting peak temperatures of electrospun PS-based form-stable PCCFMs can be adjusted to 15–25 °C with the temperature interval of 1 °C by combining the both of fatty acid binary and ternary eutectics into the PS supporting fibers. These PS-based form-stable PCCFMs can be recommended for potential low-temperature thermal energy storage applications to regulate temperature and satisfy the human thermal comfortability. [ABSTRACT FROM AUTHOR]

Water pollution caused by industrial discharges is a severe threat to our society. Thus, efficient and sustainable materials that can provide potential effective solutions are in high demand. The present work reports the development of a versatile strategy based on TEMPO-oxidized cellulose nanofibers (TOCN)/cationic guar gum (CGG) self-assembling hydrogels to remedy wastewater containing oil, heavy metal ions or organic dyes. The TOCN/CGG hydrogel-coated filter papers, prepared via a layer-by-layer deposition process, show a high oil/water separation efficiency (around 99%), with the coating amount of being as low as 0.032 g m−2 (dry mass). Through gravitational force only, the water flux can be as high as 443 L m−2 h−1. The as-prepared oil/water separation materials exhibited good recyclability. The monolithic TOCN/CGG hydrogel can also efficiently remove copper ions (Cu2+) and dyes (i.e. thioflavin T and methyl orange), based on an adsorption mechanism. The adsorption amount of Cu2+ can be as high as 498.5 mg g−1, while that of thioflavin T and methyl orange can be 430.2 mg g−1 and 134.3 mg g−1, respectively. The mass transfer driving force and the number of active binding sites are the two main factors affecting the adsorption process. This all-polysaccharide hydrogel system may be a promising potential for wastewater remedy, due to its facile/"green" preparation process and high performance, as well as the abundance and environmental-friendliness of its raw materials. [ABSTRACT FROM AUTHOR]

Five kinds of pure fatty acids such as capric acid (CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA) were selected to prepare quaternary eutectics of CA-LA-MA-PA, CA-LA-MA-SA, CA-LA-PA-SA, CA-MA-PA-SA and LA-MA-PA-SA as novel solid-liquid PCMs. Ag-coated electrospun polyurethane (PU) fibrous membranes selecting as supporting materials were then fabricated by depositing Ag nanoparticles on the surface of electrospun PU fibers through magnetron sputtering. Thereafter, a series of innovative form-stable PCMs based on the composites of Ag-coated PU fibrous membranes and quaternary eutectics were successfully prepared by physical absorption. Energy-dispersive X-ray analysis demonstrated that the Ag nanolayers were uniformly covered on the surface of PU fibers. Fourier transform infrared spectroscopy spectra suggested that there was no chemical reaction between quaternary eutectics and Ag-coated PU fibrous membranes. Scanning electron microscope images revealed that quaternary eutectics were adsorbed and encapsulated into three-dimensional porous network structures of Ag-coated PU fibrous membranes after physical absorption. Differential scanning calorimetry curves indicated that quaternary eutectics exhibited lower phase change temperatures compared with those of individual fatty acids and binary eutectics. Onset melting temperatures and enthalpies of Ag-coated composite fibrous membranes were in the range of about 14-29 °C and 95-118 kJ kg, respectively. These composite fibrous membranes had good thermal reliability, and their adsorption capabilities were around at 71-91%. Thermal performance tests showed that the quaternary eutectics/PU/Ag composite fibrous membranes processed higher heat transfer efficiency owing to the incorporation of the Ag nanolayers with excellent thermal conductivity. [ABSTRACT FROM AUTHOR]

In this paper, novel electrospun LA-PA/PET/Ag phase change composite fibers with different amount of Ag nanoparticles were prepared via the technique of electrospinning followed by UV irradiation method. The morphological structure, thermal energy storage properties, thermal energy storage and release rates of prepared LA-PA/PET/AgNO and LA-PA/PET/Ag composite fibers were investigated by scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), differential scanning calorimeter (DSC), and the measurement of melting and freezing times, respectively. The SEM images revealed that electrospun LA-PA/PET/AgNO and LA-PA/PET/Ag composite fibers possessed the smooth morphologies with cylindrical shape. The corresponding average fiber diameters gradually decreased with increasing content of the AgNO in the solutions, and slightly smaller than those of the LA-PA/PET composite fibers with oblate morphology and wrinkled surfaces. Yellow-brown coloration of electrospun LA-PA/PET/Ag phase change composite fibers were observed after UV irradiation treatment, which demonstrated that Ag ions were successfully reduced to Ag nanoparticles. The TEM images revealed that these reduced Ag nanoparticles were homogenously dispersed within the composite fibers. The results from DSC measurements indicated that the phase change temperatures and enthalpies of electrospun LA-PA/PET/Ag phase change composite fibers with different Ag content have not be influenced by the UVirradiation treatment. The thermal energy storage and release rates of electrospun LA-PA/PET/Ag phase change composite fibers were also improved due to the combination of reduced Ag nanoparticles. These UV-irradiated electrospun phase change composite fibers with excellent thermal energy storage properties can be acted as a novel form-stable PCMs for the applications related to storage and retrieval of thermal energy. [ABSTRACT FROM AUTHOR]

This paper demonstrated a novel magnetron sputtering method used for the improvement in thermal energy storage and retrieval rates of phase change materials (PCMs). The ten types of ternary fatty acid eutectics (i.e., CA-LA-MA, CA-LA-PA, CA-LA-SA, CA-MA-PA, CA-MA-SA, CA-PA-SA, LA-MA-PA, LA-MA-SA, LA-PA-SA and MA-PA-SA) were firstly prepared using five fatty acids such as capric acid (CA), lauric acid (LA), myristic acid (MA), palmitic acid (PA) and stearic acid (SA) and then selected as solid-liquid PCMs. Thereafter, magnetron sputter coating was used to deposit the functional silver (Ag) nanolayers onto the surface of electrospun polyacrylonitrile (PAN) nanofibrous mats serving as supporting skeleton. Finally, a series of composite PCMs were fabricated by adsorbing the prepared ternary eutectics into three-dimensional porous network structures of Ag-coated PAN membranes. The observations by EDX determined the formation of Ag nanolayers on the PAN nanofibers surface after magnetron sputtering. The SEM images illustrated that the Ag-coated PAN nanofibers appeared to have larger fiber diameter and rougher surface. Ag-coated PAN nanofibrous mats could effectively prevent the leakage of molten ternary eutectics and help maintain form-stable structure due to surface tension forces, capillary and nanoconfinement effects. The DSC results suggested that the phase change temperatures of the ternary fatty acid eutectics were obviously lower than those of individual fatty acids and their binary eutectics. The adsorption rates of ternary fatty acid eutectics in the composite PCMs were determined to be about 89-98 %. The thermal performance test indicated that the metallic coating of Ag dramatically improved the thermal energy storage and retrieval rates of the composite PCMs. [ABSTRACT FROM AUTHOR]

In the present work, a novel PAN-based form-stable composite phase change materials with the methyl stearate (MES) encapsulated in the supporting matrices of polyacrylonitrile (PAN) nanofibers were fabricated through electrospunning for the storage and retrieval of thermal energy. Influences of graphene oxide (GO) addition on the chemical properties, structural morphologies, mechanical properties, thermal energy storage properties, thermal stability, and thermal energy storage/retrieval rates of electrospun MES/PAN/GO phase change composite nanofibers were systematically investigated by FT-IR, FE-SEM, tensile testing, DSC, TG, and measurement of melting/freezing times, respectively. The results revealed that the incorporation of GO effectively enhanced the mechanical properties, thermal stability, as well as heat storage and release rates of the phase change composite nanofibers. The averaged tensile strength of electrospun MES/PAN/GO phase change composite nanofibers increased significantly by 573 % with 10 mass% loading of GO, while elongation at break had a maximum 107 % increment when adding 3 mass% of GO. The DSC results indicated that the electrospun PAN-based phase change composite nanofibers with various GO loadings had suitable phase transition temperatures with the latent heat ranging from about 92 to 109 kJ kg and exhibited good thermal reliability in terms of DSC measurements during 50 melting-freezing cycles. Moreover, the melting and freezing time were significantly decreased about 44 and 43 % for the MES/PAN/GO5, as well as 59 and 64 % for the MES/PAN/GO10 after introducing the GO into the composite nanofibers systems. [ABSTRACT FROM AUTHOR]

An innovative type of nanofibers-based form-stable composite phase change materials for the storage and retrieval of thermal energy was successfully prepared by encapsulating glycerol monostearate (GMS) into the porous structure of polyethylene terephthalate (PET)-supporting matrices on the nanoscale through electrospinning. The field-emission scanning electron microscopy and transmission electron microscopy images revealed that the composite nanofibers possessed desired morphologies with the average fiber diameters ranging from about 290 to 1000 nm which increased with the contents of GMS. The two phase separation (e.g., GMS phase and PET phase) was clearly observed from the images. When GMS content reached 60 %, the amount of the GMS distributing on the surface of the composite nanofibers was significantly increased during the electrospinning. The Fourier transform infrared spectroscopy spectrum proved that the PET supporting matrices were physically combined with GMS molecules. The differential scanning calorimetry analysis indicated that the GMS/PET composite nanofibers had reversible phase change behaviors, and the melting enthalpies increased from 32.63 to 66.99 kJ kg with increasing GMS amount. The TG results showed that both the onset thermal degradation temperature and charred residue of the GMS/PET composite nanofibers at 700 °C were higher than those of pristine GMS powder owing to the better thermal stability of the PET molecules. The tensile testing revealed that the averaged tensile strength and elongation at break of the all GMS/PET composite nanofibers varied from 3.29 to 10.30 MPa and from 2.42 to 42.30 %, respectively. [ABSTRACT FROM AUTHOR]

In the present work, polyamide6-room temperature ionic liquid (PA6-RTIL) composite nanofibers and membranes were successfully prepared for the first time by an electrospinning technique. The surface morphology, component analysis, mechanical properties, thermal properties and conductivity of the PA6-RTIL composite membranes were investigated by field-emission scanning electron microscope (FE-SEM), fourier transform infrared spectrometer (FT-IR), tensile testing, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and digit multimeter, respectively. The morphology, fiber diameter, mechanical strength of the obtained fibers can be controlled by changing experimental parameters for electrospinning, especially the content of RTIL in original electrospun mixture solution. The composite fibrous membranes showed ideal mechanical properties and significantly enhanced conductivity, which may be attributed to intrinsic high mechanical strength of PA6 and conductivity of RTIL. [ABSTRACT FROM AUTHOR]

The four binary fatty acid eutectics of capric-lauric acid (CA-LA), capric-myristic acid (CA-MA), capric-palmitic acid (CA-PA), and capric-stearic acid (CA-SA) were firstly prepared as solid-liquid phase change materials (PCMs); then, the composite phase change nanofibers consisting of CA-based binary fatty acid eutectic and polyethylene terephthalate (PET) were fabricated by electrospinning for thermal energy storage. The maximum mass ratios of fatty acid eutectics versus PET in the nanofibers could reach up to 2/1. The FE-SEM images revealed that the composite nanofibers possessed smooth and cylindrical morphological structure having diameters of about 100-300 nm. The fatty acid eutectic could be uniformly distributed in the three-dimension network structure of the PET nanofibers. The FT-IR results indicated that the fatty acid eutectic and PET had no chemical reaction and exhibited good compatibility with each other. The DSC measurements showed that the prepared composite nanofibers had appropriate phase transition temperatures (about 5-38 °C) based upon climatic requirement, whilst the phase change temperatures and the enthalpy values of the composite nanofibers could be adjusted by changing the contents and the types of binary fatty acid eutectics in the nanofibers. The TGA results suggested that the onset thermal degradation temperatures and charred residues at 700 °C of the composite nanofibers were lower than those of pure PET nanofibers, but higher than those of fatty acid eutectic, which were caused by the fact that the PET had better thermal stability than fatty acid eutectic. [ABSTRACT FROM AUTHOR]

Electrical voltage has a crucial effect on the nanofiber morphology as well as the jet number in the electrospinning process, while few literatures were found to explain the deep mechanism. Herein, the electrical field distribution around the spinning electrode was studied by the numerical simulation firstly. The results show that the electrical field concentrates on the tip of a protruding droplet under relatively low voltage, while subsequently turns to the edge of needle tip when the protruding droplet disappears under high voltage. The experimental results are well consistent with the numerically simulated results, that is, only one jet forms at low voltage (below 20 kV for PVDF-HFP and PVA nanofiber), but more than one jet forms under high voltage (two jets for PVDF-HFP nanofiber, four jets for PVA nanofiber). These more jets lead to (1) higher fiber diameter resulting from actually weaker electrical field for each jet and (2) wide distribution of fiber diameters due to unstable spinning process (changeable jet number/site/height) under high voltage. The results will benefit the nanofiber preparation and application in traditional single-needle electrospinning and other electrospinning methods. [ABSTRACT FROM AUTHOR]