Bi4B2O9晶体及其熔体结构的高温原位拉曼光谱研究

利用密度泛函理论计算了Bi₄B₂O₉晶体的常温拉曼光谱, 并通过与实验拉曼光谱对比, 对其振动模式进行了归属. 利用高温原位拉曼光谱研究了Bi₄B₂O₉从常温到750 ℃升温过程中微结构的变化. 随着温度的升高, 晶体的平均键长变长, 键角分布变宽, 熔化后晶体中的BiO₄和BiO₅多面体解体, BO₃构型则保持三配位不变. 运用量子化学从头算法模拟了Bi₄B₂O₉的熔体结构并与实验拉曼光谱进行了对比分析, 发现在Bi₄B₂O₉熔体中B原子团簇为孤立的BO₃构型, Bi ³⁺游离于BO₃之间, 并结合未参与形成BO₃的O原子起到平衡电荷的作用.     

Synthesis of mesoporous functional hematite nanofibrous photoanodes by electrospinning

Iron(III) oxide (hematite, Fe₂O₃) nanofibers, as visible light‐induced photoanode for water oxidation reaction of a water splitting process, were fabricated through electrospinning method followed by calcination treatment. The prepared samples were characterized with scanning electron microscopy, and three‐electrode galvanostat/potentiostat for evaluating their photoelectrochemical (PEC) properties. The diameter of the as‐spun fibers is about 300 nm, and calcinated fibers have diameter less than 110 nm with mesoporous structure. Optimized multilayered electrospun α‐Fe₂O₃ nanostructure mats showed photocurrent density of 0.53 mA/cm² under dark and visible illumination conditions at voltage 1.23 V and constant intensity (900 mW/cm²). This photovoltaic performance of nanostructure mats makes it suitable choice for using in the PEC water splitting application as an efficient photoanode. This method, if combined with appropriate flexible conductive substrate, has the potential for producing flexible hematite solar fuel generators. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and characterization of poly (acrylonitrile‐co‐acrylic acid) as precursor of carbon nanofibers

Synthesis of a co‐polymer of polyacrylonitrile (PAN) producing a carbon nanofiber out of PAN and co‐polymer of PAN and comparison between these products were examined. Free‐radical solution copolymerization of acrylonitrile (AN) with acrylic acid (AA) was studied. In this perspective, AA, and AN were used as a precursor for polymerization reactions; then copolymers were synthesized by using ammonium persulfate (APS) as an oxidant and carried in water/dimethylformamide (DMF) mixture. These polymers were used to obtain corresponding electrospun nanofibers. Synthesized P(AN‐co‐AA) was investigated by Fourier transform infrared spectroscopy‐attenuated total reflection (FTIR‐ATR) spectroscopy, and characteristic peaks for AN unit, AA were achieved. Thermal behavior was examined by using differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA), and results indicated that addition of monomers to AN unit reduced the Tg value of homopolymer PAN compared to P(AN‐co‐AA), which provides improvement to the cyclization and the formation of a thermally stable aromatic ladder polymer chain formation. In order to prevent the shrinkage and maintain the molecular orientation on nanofiber webs during stabilization, tension was applied to the samples, and thermal oxidation varies at 200–300°C for different duration of times. Surface morphology of the fibers was observed with scanning electron microscope (SEM), and average nanofiber diameter was found 550 nm, and after carbonization it was reduced to 320 nm for homopolymer PAN, and for poly(AN‐co‐AA) average nanofiber diameter was found as 220 nm and reduced to 130 nm, respectively. Copyright © 2016 John Wiley & Sons, Ltd.     

多孔碳纳米纤维负载Pd纳米颗粒用于增强电催化氧还原性能

采用溶剂热法合成了以锆为金属核心、2-氨基为配体的锆基金属有机骨架(UiO-66)纳米材料,通过静电纺丝技术制备出UiO-66自由分散的聚丙烯腈(PAN/UiO-66)纤维,可控热解得到多孔碳纳米纤维(porous carbon nanofibers,PCNFs),结合湿化学还原法在PCNFs表面沉积Pd纳米颗粒,得到PCNFs@Pd复合材料。通过扫描电子显微镜、透射电子显微镜、X射线衍射技术对其形貌、组成、结构进行表征;采用电化学工作站分别测试了PCNFs@Pd在0.1 mol·L^-1KOH和0.1 mol·L^-1HClO₄电解质中氧还原性能(oxygen reduction reaction,ORR)。结果表明,在PAN纤维中添加UiO-66显著提高了PCNFs@Pd(Pd负载量为0.34%)复合材料的ORR性能。相比40%Pt/C,在碱性电解质中,PCNFs@Pd复合材料展示出更低的Tafel斜率、更优异的循环稳定性和耐甲醇中毒性。在酸性电解质中也表现出类似20%Pt/C的催化活性和循环稳定性。     

Bruch’s-Mimetic Nanofibrous Membranes Functionalized with the Integrin-Binding Peptides as a Promising Approach for Human Retinal Pigment Epithelium Cell Transplantation

Background: This study aimed to develop an ultrathin nanofibrous membrane able to, firstly, mimic the natural fibrous architecture of human Bruch’s membrane (BM) and, secondly, promote survival of retinal pigment epithelial (RPE) cells after surface functionalization of fibrous membranes. Methods: Integrin-binding peptides (IBPs) that specifically interact with appropriate adhesion receptors on RPEs were immobilized on Bruch’s-mimetic membranes to promote coverage of RPEs. Surface morphologies, Fourier-transform infrared spectroscopy spectra, contact angle analysis, Alamar Blue assay, live/dead assay, immunofluorescence staining, and scanning electron microscopy were used to evaluate the outcome. Results: Results showed that coated membranes maintained the original morphology of nanofibers. After coating with IBPs, the water contact angle of the membrane surfaces varied from 92.38 ± 0.67 degrees to 20.16 ± 0.81 degrees. RPE cells seeded on IBP-coated membranes showed the highest viability at all time points (Day 1, p < 0.05; Day 3, p < 0.01; Days 7 and 14, p < 0.001). The proliferation rate of RPE cells on uncoated poly(ε-caprolactone) (PCL) membranes was significantly lower than that of IBP-coated membranes (p < 0.001). SEM images showed a well-organized hexa/polygonal monolayer of RPE cells on IBP-coated membranes. RPE cells proliferated rapidly, contacted, and became confluent. RPE cells formed a tight adhesion with nanofibers under high-magnification SEM. Our findings confirmed that the IBP-coated PCL membrane improved the attachment, proliferation, and viability of RPE cells. In addition, in this study, we used serum-free culture for RPE cells and short IBPs without immunogenicity to prevent graft rejection and immunogenicity during transplantation. Conclusions: These results indicated that the biomimic BM-IBP-RPE nanofibrous graft might be a new, practicable approach to increase the success rate of RPE cell transplantation.     

聚乳酸熔体纺丝、粘接和吸附性能的初步研究

针对制备香烟过滤嘴用丝束和过滤嘴棒的特殊需要,研究了聚乳酸的纺丝、粘接和吸附性能,通过流变学测量考察了各种加工因素对熔体流动性和可纺性的影响,特别是残留水分的影响,用分子量、DSC和力学性能测量跟踪了熔体纺丝和后加工过程.所获结果对确定聚乳酸树脂的规格范围,确定纺丝和后加工工艺,具有参考价值.     

ICP-AES测定锰矿中二氧化硅含量

试样经氢氧化钠和过氧化钠混合熔剂碱熔,再用酸浸提,干过滤后定容.采用ICP-AES测定锰矿中二氧化硅含量.本法测定锰矿标样(冶金部标准样品505)中二氧化硅含量,其测定结果的相对标准偏差RSD为1.08%,测定平均值为33.93%(标样推荐值为33.58%).     

Copolymerization of norbornene with methoxycarbonylnorbornene catalyzed by Ni{CF3C(O)CHC[N(naphthyl)]CH3}2/B(C6F5)3 catalytic system and good processability for Dry/Wet phase inversion and electrospinning technique

Copolymerization of norbornene (NB) with methoxycarbonylnorbornene (NB‐COOCH₃) was carried out with catalytic system of Ni{CF₃C(O)CHC[N(naphthyl)]CH₃}₂ and B(C₆F₅)₃ in toluene. The catalytic system exhibited higher activity 2.69 × 10⁵ (gpolymer/mol Ni h) for copolymerization of norbornene and methoxycarbonylnorbornene. The influence results of the comonomer feed content on the polymerization showed that the NB‐COOCH₃ has a very high insertion ratio in all copolymers, and the NB‐COOCH₃ content in copolymers can be controlled to be 7.9–77.6 mol % at content of 10–90 mol % of the NB‐COOCH₃ in the monomer feeds ratios. The reactivity ratios, r_NB‐COOCH3 = 0.578 and r_NB = 0.859, were determined by the Kelen–TÜdÕs method. Copolymers were processed by solution casting method, dry/wet phase inversion technique, and electrospinning. The films prepared by solution casting method showed good transparency in the visible region. The membranes processed by dry/wet phase inversion technique were microporous structures. The fibers diameters fabricated by electrospinning were about 3 μm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Atmospheric plasma treatment of pre‐electrospinning polymer solution: A feasible method to improve electrospinnability

The electrospinnability of polyethylene oxide (PEO) was manipulated by atmospheric plasma treatment of pre‐electrospinning solutions. Conductivity, viscosity, and surface tension of PEO solutions increased after plasma treatment, and the plasma effect remained longer when the solution concentrate increased. Both untreated and treated solutions were then electrospun, and the morphology of the resultant nanofibers was observed by SEM. Atmospheric plasma treatment improved the electrospinnability of PEO solutions and led to less beads and finer diameter distribution in the resultant nanofibers. Additionally, plasma treatment of the pre‐electrospinning solutions affected the crystal structure of resultant nanofibers. These results suggest that atmospheric plasma treatment is a feasible approach to improve the electrospinnability of polymer solutions and can used to control the structure of electrospun nanofibers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Morphology and physical properties of a novel Ramie‐PU blended nonwoven by electrospinning: The effect of cosolvent ratio

A novel macro/nano blended nonwoven with excellent physical properties was prepared by electrospinning polyurethane (PU) nanofibers onto the surface of ramie webs under different weight ratios of N,N‐dimethylacetamide (DMAc)/acetone cosolvents. The ratio of cosolvents has a significant influence on the morphology, tensile properties, resilience, and thermal properties of the resultant samples. Bead‐free and fine interconnected nanofibers were obtained with an increase of acetone content up to 60 wt%. The total physical properties of the blended nonwovens were optimal for a DMAc/acetone ratio of 40/60, in which the tensile load at break, extension at break and Young's modulus were 441, 54, and 256% higher than that of pure ramie web, respectively. The resilience of the blended nonwovens was ～20% higher than that of nonblended ramie web. The significant improvement of physical properties may be due to the good connection between PU nanofiber membranes and ramie webs and the molecular chain structure differences, interconnected structural differences, and high extensibility of PU nanofibers, according to the results of crystallization by differential scanning calorimetry (DSC) and morphological observation by scanning electronic microscopy (SEM). © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1–14, 2010