Facile preparation and enhanced capacitance of the polyaniline/sodium alginate nanofiber network for supercapacitors

A porous and mat-like polyaniline/sodium alginate (PANI/SA) composite with excellent electrochemical properties was polymerized in an aqueous solution with sodium sulfate as a template. Ultraviolet-visible spectra, X-ray diffraction pattern, and Fourier transform infrared spectra were employed to characterize the PANI/SA composite, indicating that the PANI/SA composite was successfully prepared. The PANI/SA nanofibers with uniform diameters from 50 to 100 nm can be observed on scanning electron microscopy. Cyclic voltammetry and galvanostatic charge/discharge tests were carried out to investigate the electrochemical properties. The PANI/SA nanostructure electrode exhibits an excellent specific capacitance as high as 2093 F g(-1), long cycle life, and fast reflect of oxidation/reduction on high current changes. The remarkable electrochemical characteristic is attributed to the nanostructured electrode materials, which generates a high electrode/electrolyte contact area and short path lengths for electronic transport and electrolyte ion. The approach is simple and can be easily extended to fabricate nanostructural composites for supercapacitor electrode materials.     

Fabrication,characterization, and drug release study of vitamin C–loaded alginate/polyethylene oxide nanofibers for the treatment of a skin disorder

Pigmented purpuric dermatosis (PPD) is a skin disorder mainly seen in the lower limbs. The nanofibrous web has been shown to be an appropriate alternative for the treatment of skin diseases as a drug delivery vehicle. In this study, sodium alginate (SA)/polyethylene oxide (PEO) nanofibers containing vitamin C (VC) were fabricated using both blended electrospinning and core/shell electrospinning. The resultant nanofibers were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. Enhancing the VC content resulted in increasing the nanofibers diameter. Also, the degradation rate and drug release were investigated. Drug release was evaluated using the in vitro dissolution and permeation method. The degradation rate and the drug release of the core/shell nanofibers were found to be lower than those of the blended nanofibers. The drug release of the extended nanofibers followed a different pattern, indicating that the extension of the nanofibers could be a promising way to control the drug release.     

Polyaniline nanofibers: facile synthesis and chemical sensors

Polyaniline nanofibers with uniform diameters between 30 and 50 nm can be made in bulk quantities through a facile aqueous/organic interfacial polymerization method at ambient conditions. The nanofibers have lengths varying from 500 nm to several micrometers and form interconnected networks. Thin films made of the nanofibers have superior performance in both sensitivity and time response to vapors of acid (HCl) and base (NH3).     

微/纳米结构的聚苯胺及其浸润性研究

借助沉积聚合辅助的“无模板”法在玻璃基片上制备出水杨酸掺杂的微/纳米结构的聚苯胺.实验发现,微/纳米结构的形貌及其浸润性依赖于掺杂剂与单体的摩尔比和沉积时间.当低分子量的聚苯胺微米球和纳米球共存时,其沉积的表面呈现出高的疏水性(接触角θ=148.0°),这主要来源于微/纳米共存的结构导致高的表面粗糙度,能捕获更多的空气所致.FTIR,紫外-可见光谱和X光射线衍射表征了微/纳米球的分子结构及其结晶性.     

Nanostructured polyaniline sensors

The conjugated polymer polyaniline is a promising material for sensors, since its conductivity is highly sensitive to chemical vapors. Nanofibers of polyaniline are found to have superior performance relative to conventional materials due to their much greater exposed surface area. A template-free chemical synthesis is described that produces uniform polyaniline nanofibers with diameters below 100 nm. The interfacial polymerization can be readily scaled to make gram quantities. Resistive-type sensors made from undoped or doped polyaniline nanofibers outperform conventional polyaniline on exposure to acid or base vapors, respectively. The nanofibers show essentially no thickness dependence to their sensitivity.     

Fabrication,characterization and in vivo evaluation of dexpanthenol sustained-release nanofibers for wound healing

In this study, wound dressings consisting of dexpanthenol (Dex)-loaded electrospun nanofibers were fabricated using polyvinyl alcohol (PVA)/sodium alginate (SA), and chitosan as the core and the shell, respectively. Considering the remarkable properties of chitosan, it was used as a shell against drug release and to improve the thermal stability, and tensile strength of the scaffold. By comparing the thermogravimetric, and tensile strength results of nanofibers with and without shell, it was revealed that the presence of chitosan in the shell side could improve the thermal stability and increased the tensile strength by about three times. The isotherm models of dexpanthenol release from the PVA/SA/Dex-CS scaffold was best described by the Langmuir model. Besides, Fourier transform infrared, scanning electron microscopy, and X-ray diffraction techniques were performed to characterize nanofibers. Furthermore, an in vivo investigation of a wound dressing with dexpanthenol showed better healing compared to the wound dressings without dexpanthenol.     

Efficient method for fabrication of fluorescein derivative/PDAC composite nanofibers and characteristics of their photoluminescent properties

Electrospinning is a simple and cost-effective approach for the production of nanofibers and assemblies with controllable structures. In this work, the pure poly (diallyldimethylammonium chloride) (PDAC) nanofibers with smooth surface and uniform morphology were successfully fabricated by electrospinning. On this basis, fluorescein/PDAC, dibromofluorescein/PDAC, diidofluorescein/PDAC and fluorescein sodium/PDAC composite nanofibers were also fabricated using the same method. The average diameters of the pure PDAC nanofibers increased with the applied field strength and the amount of PDAC in the solutions; and the average diameters ranged from 280 to 450 nm. The morphology of pure PDAC nanofibers has been observed by scanning electron microscopy (SEM) and the photoluminescent properties of fluorescein derivative/PDAC composite nanofibers have been characterized by fluorescence microscopy.     

Preparation of antimicrobial sodium alginate with chito-oligosaccharide side chains

To provide sodium alginate (SA) with an antimicrobial property, we introduced chito-oligosaccharide (COS) via chemical bonding in a two-step procedure. We reacted COS with N-methylol acrylamide (NMA) with N-methylol groups to prepare acrylamidomethyl chito-oligosaccharide (COS–NMA). SA with COS side chains (SA–COS) was produced through a subsequent reaction of SA with COS–NMA. The chemical structure of SA–COS was confirmed by IR spectroscopy and ¹H NMR spectroscopy. With a two-step method, we successfully prevented insoluble-complex formation due to electrostatic attraction between chitosan and alginate. SA–COS showed excellent antimicrobial activity, with the growth of microorganisms completely suppressed by a small amount of COS (1.8 wt %). © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1810–1816, 2001     

Facile synthesis of polyaniline nanofibers using chloroaurate acid as the oxidant

This work demonstrated a facile route to the synthesis of polyaniline (PANI) nanofibers by polymerization of aniline using chloroaurate acid (HAuCl(4)) as the oxidant. The reduction of AuCl(4)(-) is accompanied by oxidative polymerization of aniline, leading to uniform PANI nanofibers with a diameter of 35 +/- 5 nm and aggregated gold nanoparticles which can precipitate from the liquid phase during the reaction. The resultant PANI nanofibers and gold particles were characterized by means of different techniques, such as UV-vis, FTIR spectroscopy, and scanning and transmission electron microscopy methods. It is found that the gold aggregates are capped with polyaniline, and the conductivity of the fibers is around 0.16 S/cm.     

Electrospinning Process of Thermo-sensitive Poly(N-isopropylacrylamide) /poly (2-acrylamido-2-methylpropanesulfonic acid) Nanofibers

Poly (N-isopropylacrylamide)/poly (2-acrylamido-2-methylpropanesulfonic acid) (PNIPAAm/PAMPS) nanofibers was prepared using the electrospinning technique. The electrospinning process parameters such as solution concentration, voltage, receiver distance and flow rate were determined by the orthogonal experiments. The appropriate electrospinning parameters were 7.0% of solution concentration, 10.0 kV of voltage, 20 cm of distance and 3.1 μL·min^?1 of flow rate, respectively. The major factor affecting the nanofibers diameter was the solution concentration and the diameter increased with the solution concentration. The Fourier-transform infrared spectroscopy (FTIR) was conducted to characterize the structure of the components for electrospinning. Scanning electron microscopy (SEM) was taken to observe the morphology, and the contact angle (CA) measuring was carried out to determine the wettability of the nanofibers with temperatures. The results of SEM observation showed that the surfaces of nanofibers were smooth with uniform fibrous diameters and without the formation of beads. The CA detections showed that the electrospun PNIPAAm/PAMPS nanofibers exhibited thermo-sensitivity of hydrophilicity at 20°C and hydrophobicity at 40°C.     

Nanofibers resulting from cooperative electrostatic and hydrophobic interactions between peptides and polyelectrolytes of opposite charge

We investigated whether cationic peptides that contain hydrophobic side chains were able to stabilize themselves via hydrophobic interactions between neighboring peptide molecules upon electrostatic binding to oppositely charged polyelectrolytes. The interaction mechanism was examined through a model system consisting of the anionic polyelectrolyte alginate and the cationic decapeptide ozarelix. The interaction resulted in the formation of highly ordered complexes that were noticeable upon visual inspection. These complexes were then investigated by microscopic techniques and shown to exhibit a branched network structure. Cryogenic-temperature transmission electron microscopy (cryo-TEM) and negative staining TEM revealed that the molecular interactions between alginate and ozarelix led to the formation of nanofibers. The rodlike nanofibers had a diameter distribution of 4-8 nm. Isothermal titration calorimetry was used to determine the thermodynamic parameters of the alginate-ozarelix interaction. The binding constant was found to be on the order of 10(6) M(-1), indicating a high binding affinity. The interaction of the peptide with the polyelectrolyte triggered profound changes in the conformation of ozarelix, which was confirmed by UV spectroscopy and circular dichroism. On the basis of these experimental results, a theoretical modeling study of the alginate-ozarelix interaction was conducted to gain a better molecular-level understanding of the complex structure. It revealed that, upon binding of ozarelix to alginate, new intermolecular and intramolecular aromatic interactions between the ozarelix molecules occurred. These interactions changed the conformation of the peptide, a modification in which the aromatic side chains played a major role. Our results indicate that the cationic peptides interact with the polyanions via electrostatic interactions, but are additionally stabilized via hydrophobic interactions. This binding mode may serve as a powerful tool to extend the duration of drug release in hydrogel drug delivery systems.     

Improved cellular response on multiwalled carbon nanotube-incorporated electrospun polyvinyl alcohol/chitosan nanofibrous scaffolds

We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.     

Mechanochemical Complexation between Deoxycholic Acid and Salicylic Acid

A complex between deoxycholic acid (DCA) and salicylic acid (SA) was prepared by grinding and coprecipitation methods. The resultant complex was characterized by means of powder X-ray diffractometry, IR spectroscopy and thermal analysis. The stoichiometry (DCA : SA 1 : 1) of the complex obtained by grinding was identical to that obtained by coprecipitation. The powder X-ray diffraction pattern of the DCA–SA complex differed from the typical pattern of DCA–guest complexes such as DCA–camphor and DCA–phenanthrene complexes. IR spectra suggested that a different kind of hydrogen bonding was formed in the crystal of the DCA–SA complex, compared with the other DCA–guest complexes. This was in good agreement with data from the crystal structure.     

Ag/ZnO纳米纤维的制备及光催化性能

采用静电纺丝技术及煅烧法制备了氧化锌纳米纤维, 然后采用水热法将银纳米颗粒负载到了氧化锌纳米纤维表面. 利用X射线衍射(XRD)、 X射线光电子能谱(XPS)、 能量色散X射线光谱(EDX)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等技术对合成的Ag/ZnO纳米纤维的结构和组成进行了表征. SEM结果表明, 直径在5~100 nm之间的银纳米颗粒附着在直径在80~330 nm之间的氧化锌纤维表面形成了异质结构. 以常见的有机污染物甲基橙、 亚甲基蓝和罗丹明B等为降解底物, 对Ag/ZnO纳米纤维的光催化性能进行了表征. 结果表明, 负载银纳米颗粒后, 复合催化剂的光催化性能明显提高.     

Synthesis and rheological investigation of self‐healable deferoxamine grafted alginate hydrogel

Deferoxamine grafted alginate (SA‐DFA) was successfully synthesized via amidation of sodium alginate with deferoxamine mesylate as determined by H‐NMR and elemental analysis. SA‐DFA with different graft yield was obtained by adjusting the ratio of sodium alginate and deferoxamine mesylate. It was found that aqueous solution of SA‐DFA could form hydrogel spontaneously due to hydrogen bonding interactions, which also endowed the SA‐DFA hydrogel with self‐healing capability. The healing efficiency of SA‐DFA hydrogels ranged from 53.64 to 90.16%. In addition, surface morphologies of SA‐DFA hydrogels before/after self‐healing process were demonstrated by SEM images. We anticipated that such self‐healable alginate hydrogel would be applied in the field of wound healing. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 856–865     

Simple fabrication of cellulose nanofibers via electrospinning of dissolving pulp and tunicate

This work demonstrates a simple fabrication of cellulose nanofibers by direct electrospinning of dissolved cellulose solutions. The hard- and softwood pulps and the outer mantles of tunicate were dissolved in a mixture of trifluoroacetic acid and dichloroethane by stirring and ultrasonication to give highly viscoelastic, clear solutions. These solutions were electrospun to form continuous nanofibers made of unsubstituted cellulose, which were confirmed by scanning electron microscopy (SEM) and IR spectroscopy. Statistical analysis of the SEM images of the nanofibers suggested that there are positive correlations between diameters of the nanofibers and concentration of the cellulose solution. The mean diameters of the nanofibers obtained from softwood pulp (DP of cellulose ≈ 1200) solutions were larger than those from hardwood pulp (DP of cellulose ≈ 500) at the same concentrations. This indicates that the DP of cellulose is one of the important parameters to control the diameters of the electrospun cellulose nanofibers.     

静电纺丝法制备煤基纳米碳纤维及其在超级电容器中的应用

以氧化处理的新疆库车原煤、聚丙烯腈(PAN)和N,N-二甲基甲酰胺(DMF)为原料,通过静电纺丝法制备了直径均匀的煤基纳米碳纤维前驱体,经高温碳化、CO2活化得到煤基超级电容器电极材料.使用X射线能谱仪、物理吸附仪、扫描电子显微镜、红外光谱仪和热分析仪等对前驱体及产物进行了表征.结果表明,原煤经过高锰酸钾氧化处理后,部分连接大分子的烷基链被打断,含氧基团明显增多,使原煤在DMF中的溶解度大幅提高.电化学测试结果表明,在电流密度为1 A/g时,煤基活化碳纤维的比电容为259.7F/g,在1000次循环充放电后比电容仍然保持99.2%.     

Evaluation and correlation of electrochemical and mechanical properties of PVA/SA nanofibres

The present study evaluates and correlates the morphology of poly (vinyl alcohol) (PVA) and sodium alginate (SA) nanofibres with their internal structure to determine dielectric and tensile properties for future applications as long-lasting and resistant cell scaffolds. This work generates electrospun nanofibres mixing SA concentration in a PVA solution cross-linked in calcium chloride media. The dielectric properties of the nanofibres that were obtained using electrochemical impedance spectroscopy (EIS) show that at higher amount of SA in the PVA/SA fibres, the cross-linking process occurs at shorter times, indicating the modification of the internal structure of the PVA/SA. The X-ray photoelectron spectra (XPS) demonstrate that the chemical composition of the nanofibres varies depending on the depth profile. The transmission electron microscopy (TEM) proves that the PVA/SA is formed as a core-shell coaxial nanofibre. The tensile testing demonstrates that with a higher SA concentration, the mechanical properties show brittleness.     

Electrospun nanofibers of poly（vinyl pyrrolidone）/Eu^3＋ and its photoluminescence properties

Nanofibers of poly（vinyl pyrrolidone） （PVP）/Eu^3＋ with diameters of 300-900 nm were prepared by using sol-gel processing and electrospinning technique. The products were characterized by scanning electron microscope （SEM）, Fourier transform infrared spectroscopy （FT-IR）, and photoluminescence （PL）. The results indicated that, Eu^3＋ was successfully embedded in the onedimensional hybrid nanofibers, and the PVP/Eu^3＋ hybrid nanofibers had favorable photoluminescence properties.     

Polyaniline Langmuir-Blodgett film based cholesterol biosensor

Cholesterol oxidase (ChOx) has been covalently linked to Langmuir-Blodgett (LB) monolayers of polyaniline (PANI)-stearic acid (SA) prepared onto indium-tin-oxide (ITO) coated glass plates via glutaraldehyde (Glu) chemistry. These ChOx/Glu/PANI-SA LB film/ITO electrodes have been characterized by FT-IR, cyclic voltammetry, and scanning electron microscopy, respectively. The results of response measurements carried out on these bioelectrodes using linear sweep voltammetry (LSV) reveal linearity from 25 to 400 mg/dL of cholesterol concentration with sensitivity of 88.9 nA mg(-1) dL. The linear regression analysis of bioelectrode reveals standard deviation and correlation coefficient of 0.737 microA and 0.9988, respectively. The low value of the Michaelis-Menten constant of these bioelectrodes obtained as 1.21 mM for the immobilized enzyme indicates increased interaction between ChOx and cholesterol in the PANI-SA LB film.