中空载银纤维的银离子释放性能

银系纤维的抗菌性能主要来源于纤维表面或内部释放出来的银离子。采用电感耦合等离子体发射光谱仪对中空载银纤维的银离子释放性能进行测试分析,结果表明:中空载银纤维具有较为持久的释放性能,释放的银离子量随着浸渍时间的延长、浸渍温度的升高以及纤维本身载银量的增加而增加,随着纤维长度的增加而减少。     

纳米无机粒子选择性分布与迁移对聚合物共混物形态与性能的影响

综述了纳米无机粒子在聚合物合金中选择性分布的影响因素及纳米无机粒子在聚合物中分散的重要性,重点从相行为、相形态、力学性能、电学性能、流变行为、结晶和熔融行为以及光学性能等方面总结了近年来纳米无机粒子在聚合物共混物中的选择性分布与迁移对以聚合物共混物为基体的纳米复合材料的形态和性能的影响。特别强调了如何利用热力学和动力学因素调控纳米无机粒子在聚合物合金中的分布。     

聚乙二醇单酯的合成及其在高吸水性树脂中的交联作用

合成了正丁氧基聚乙二醇甲基丙烯酸酯交联剂 ,通过反相悬浮聚合考察了其对高吸水性树脂吸水性能的效果 ,探讨了聚乙二醇分子量等交联剂合成条件与用量对吸水性树脂性能的影响 ,发现聚乙二醇相对分子质量为 40 0～ 80 0时高吸水树脂吸水性能较好 ,吸水倍率为 35 0～ 5 0 0g/g ,吸盐水倍率超过 6 0g/g ,加压吸水倍率变化小     

Porous Superabsorbent Hydrogel Composites: Synthesis,Morphology and Swelling Rate

Summary: Novel porous hydrogel composites with very high swelling capacity and enhanced rate of water absorption were synthesized in aqueous media at room temperature under normal atmospheric conditions. The porosity was induced through either foaming conducted in the course of polymerization or non‐solvent dewatering of the as‐synthesized gels. Kaolin was incorporated as an inorganic component in the polymerization process. The foaming technique was used to form porosity using three systems of different porogens (porosity generators), i.e. sodium bicarbonate, acetone and their combination. The as‐synthesized gels were dried through oven drying and non‐solvent dewatering. Morphology and swelling rate of the superabsorbent hydrogel composites (SHCs) were studied versus either the porogen system or the drying method. It was found that the simultaneous polymerization‐foaming technique had great influence on the improvement of porosity, morphology of the porous structure and the rate of water absorption. It was also shown that the drying procedure had remarkable influence on preserving the preformed porosity. Methanol as a dewatering solvent produced SHCs with higher porosity and swelling rate in comparison with the porosity of the hydrogels dewatered in acetone. Our invented methodology including simultaneous polymerization and foam formation using dual‐porogen system and the subsequent methanol‐dewatering approach was found to be the most efficient, highly practical, and cost‐effective route for preparing improved superabsorbing hydrogel materials.

     

Complexes of Silver(I) Ions and Silver Phosphate Nanoparticles with Hyaluronic Acid and/or Chitosan as Promising Antimicrobial Agents for Vascular Grafts

Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes.     

Morphology and Mechanical Properties in Polymer Blends of Photocurable Polymer and Polycarbonate

Relationships between the morphologies and mechanical properties of binary blends of a photocurable polymer (2‐propenoic acid, (octahydro‐4,7‐methano‐1H‐indenediyl) bis(methylene)ester; DCA) and a linear polymer (poly(4,4′‐cyclohexylidene bisphenol carbonate); PCz) have been investigated. The blend films are prepared by in situ photopolymerization of homogeneous mixtures of a DCA‐monomer and PCz. The phase structure has been converted from a semi‐interpenetrating polymer networks (semi‐IPN) structure to a bicontinuous structure by controlling the cure temperature. Bicontinuous phase‐separated structures can be obtained by curing a wide range of compositions of 17–50 wt.‐% PCz at high temperatures. Miscible semi‐IPN structures are attained by means of photopolymerization below the glass transition temperature of the homogenous mixture before performing photoirradiation, such that magnetic relaxation measurements showed the blend to be miscible in the 10 nm order. The tensile strength and modulus reached a maximum in those blends having an intermediate vague phase structure between semi‐IPN and bicontinuous structures that have a strong interfacial interaction, which leads to incomplete phase decomposition in the PCz‐rich matrix phase. The maximum strength and modulus prepared under optimum condition are inferior to those of the individual components. In contrast, the elongation and break energy are greatly improved in those blends with bicontinuous structures having a diffused phase boundary.

DCA‐rich domain size in bicontinuous structure for DCA/PCz system, as a function of cure temperature; (□) 17 wt.‐% PCz, (○) 30 wt.‐% PCz, and (?) 50 wt.‐% PCz.     

银纳米粒子在木瓜蛋白酶固定化中的应用

通过超声条件下正硅酸四乙酯与g-氨丙基三乙氧基硅烷的同步水解,一步制备了带氨基的二氧化硅微球,并在其表面沉积了银纳米粒子. 以此负载银的二氧化硅微球作为载体固定木瓜蛋白酶,研究了银纳米粒子负载量对木瓜酶固定化的影响,考察了固定化木瓜蛋白酶的性能. 结果表明,当载体的银负载量为0.68%时,固定木瓜蛋白酶活回收率达到最高,比使用未负载银的载体提高了188%;该固定酶比游离酶具有更好的热稳定性,在重复使用20次后仍保持原有酶活的43%,4℃下储存2个月后酶活基本没有下降.     

Morphology,Electrical, and Rheological Properties of Silane‐Modified Silver Nanowire/Polymer Composites

Electrically conducting films containing AgNws, hydrophilic and hydrophobic resins were prepared. FT‐IR reveals that the interface between the AgNws and epoxy could be successfully modified by APTES. XPS shows that the AgNws were attracted by hydrogen bonds of ? NH₂ and ? NH? groups after APTES modification. SEM analysis shows that the AgNws were well dispersed in the resin. The AgNws were also blended with hydrophilic and acrylic resins, and the resulting blends were compared with AgNws/epoxy blends. Results show that AgNw/PVA‐resin films possess the lowest surface electrical resistance. The AgNw/PVA‐resin and silane‐modified AgNw/epoxy resin conductive films possess a similar electrical percolation threshold.

     

Morphology of polyacetylene and doped polyacetylene

A detailed study of the morphology of polyacetylene and iodine and arsenic pentafluoride doped polyacetylene has been carried out using scanning electron microscopy and transmission electron microscopy techniques. The results reveal a variety of fibrillar and rod-like morphologies for trans-polyacetylene. The samples retain this morphology upon doping, with, in many cases, a significant increase in the diameter of these structures. Larger increases in diameter were observed for the AsF₅ doped samples than in iodine doped samples. Energy dispersive X-ray analysis and back-scattered electron imaging were used to determine dopant distribution. Both iodine and arsenic distributions were uniform across the film surfaces to a resolution of 5000 Å. In addition, both dull and shiny sides of the films are shown to have approximately the same dopant concentration. This demonstrates that nonuniformity of the doping occurs, if at all, at a much finer scale. Finally, we have determined that small crystals, presumably arsenic trioxide, form on the surface of AsF₅ doped polyacetylene upon even moderate exposure to air.     

Effect of Polymer Crystallinity on Morphology in Ceramic Injection Molding

Many ceramic injection molding vehicles include semicrystalline polymers which characteristically adopt a spherulitic growth morphology. Usually the spherulites are rendered invisible by the opacity of the ceramic powder but in this study they are clearly visible. Polyoxymethylene (POM), has been used as the vehicle. The growth of the spherulites is shown to be dependent on cooling rate and hence on position in the molding. Furthermore, migration of low molecular weight additives by syneresis is shown to occur and to influence the crack path in the as-molded state. An unusual composite fractograph is shown in which fracture faces made after molding, after binder removal, and after sintering are contiguous. Only after molding does the crack path follow the spherulite boundaries; behavior that is also widely reported for unfilled POM.     

Fabrication and Characterization of Gelatin Stabilized Silver Nanoparticles under UV-Light

Silver nanoparticles (Ag-NPs) were successfully synthesized using the UV irradiation of aqueous solutions containing AgNO(3) and gelatin as a silver source and stabilizer, respectively. The UV irradiation times influence the particles' diameter of the Ag-NPs, as evidenced from surface plasmon resonance (SPR) bands and transmission electron microscopy (TEM) images. When the UV irradiation time was increased, the mean size of particles continuously decreased as a result of photoinduced Ag-NPs fragmentation. Based on X-ray diffraction (XRD), the UV-irradiated Ag-NPs were a face-centered cubic (fcc) single crystal without any impurity. This study reveals that the UV irradiation-mediated method is a green chemistry and promising route for the synthesis of stable Ag-NPs for several applications (e.g., medical and surgical devices). The important advantages of this method are that it is cheap, easy, and free of toxic materials.     

Silver Nanoparticles Biocomposite Films with Antimicrobial Activity: In Vitro and In Vivo Tests

Overuse of antimicrobials by the population has contributed to genetic modifications in bacteria and development of antimicrobial resistance, which is very difficult to combat nowadays. To solve this problem, it is necessary to develop new systems for the administration of antimicrobial active principles. Biocomposite systems containing silver nanoparticles can be a good medical alternative. In this context, the main objective of this study was to obtain a complex system in the form of a biocomposite film with antimicrobial properties based on chitosan, poly (vinyl alcohol) and silver nanoparticles. This new system was characterized from a structural and morphological point of view. The swelling degree, the mechanical properties and the efficiency of loading and release of an anti-inflammatory drug were also evaluated. The obtained biocomposite films are biocompatibles, this having been demonstrated by in vitro tests on HDFa cell lines, and have antimicrobial activity against S. aureus. The in vivo tests, carried out on rabbit subjects, highlighted the fact that signs of reduced fibrosis were specific to the C2P4.10.Ag1-IBF film sample, demonstrated by: intense expression of TNFAIP8 factors; as an anti-apoptotic marker, MHCII that favors immune cooperation among local cells; αSMA, which marks the presence of myofibroblasts involved in approaching the interepithelial spaces for epithelialization; and reduced expression of the Cox2 indicator of inflammation, Col I.     

Polymer-Metal Nanocomposites Containing Dual-Function Metal Nanoparticles: Ion-Exchange Materials Modified with Catalytically-Active and Bactericide Silver Nanoparticles

This work reports the results obtained by the development of two types of nanocomposite membranes containing metal nanoparticles prepared by applying the Intermatrix Synthesis technique for the synthesis of silver nanoparticles in the ion-exchange matrices of sulfonated polyethersulfone-Cardo and Nafion membranes. The stability (in terms of silver nanoparticles loss) of the polymer-metal nanocomposites was evaluated by using both ultrasonic and thermostatic baths and appeared to be appropriate for their practical applications. The dual-function nanocomposites were characterized in batch tests, first, by monitoring their catalytic activity in the reduction of p-nitrophenol to p-aminophenol and second, by evaluating their antibacterial efficiency towards E. coli. The results of the catalytic tests have shown that polymer-silver nanocomposites demonstrate remarkably better activity in comparison with their polymer-palladium nanocomposite analogues. The same nanocomposites have been shown to permit the complete disinfection of E. coli containing water within a short period of time.     

Surface Modification of Polyacrylonitrile Fibers and their Application in the Preparation of Silver Nanoparticles

The chelating functional polymer, polyacryloamidoxime (PAAmF), is formed on the surface of polyacrylonitrile fibers (PANF) by the surface modification method. The characteristics of PAAmF with different modification times are monitored by Fourier transform infrared (FTIR) spectroscopy. Scanning electronic microscopy (SEM) reveals that the surface of PAAmF/PANF is rougher than that of the pristine PANF. Additionally, amidoxime chelating groups on the surface of PANF are the coordination sites for chelating Ag⁺, at which nano-sized silver nanoclusters are grown, using the reduction method. Silver nanoclusters are identified by X-ray diffraction (XRD) and SEM microscopy. SEM photographs demonstrate that the Ag nanoclusters are arranged loosely on the surface of the PANF with a wider-size distribution of 24.9 nm under reduction conditions of pH=5 and 30 °C. However, the distribution of the sizes of the Ag nanoclusters shrinks to 23.5 nm at pH=7. As the reaction temperature is increased to 60 °C, the Ag nanoclusters aggregate to ~29.8 nm as observed by SEM.     

Bionanofactories for Green Synthesis of Silver Nanoparticles: Toward Antimicrobial Applications

Among the various types of nanoparticles and their strategy for synthesis, the green synthesis of silver nanoparticles has gained much attention in the biomedical, cellular imaging, cosmetics, drug delivery, food, and agrochemical industries due to their unique physicochemical and biological properties. The green synthesis strategies incorporate the use of plant extracts, living organisms, or biomolecules as bioreducing and biocapping agents, also known as bionanofactories for the synthesis of nanoparticles. The use of green chemistry is ecofriendly, biocompatible, nontoxic, and cost-effective. We shed light on the recent advances in green synthesis and physicochemical properties of green silver nanoparticles by considering the outcomes from recent studies applying SEM, TEM, AFM, UV/Vis spectrophotometry, FTIR, and XRD techniques. Furthermore, we cover the antibacterial, antifungal, and antiparasitic activities of silver nanoparticles.     

Silver Nanoparticles Mediate Differential Responses in Keratinocytes and Fibroblasts during Skin Wound Healing

With advances in nanotechnology, pure silver has been recently engineered into nanometer‐sized particles (diameter <100 nm) for use in the treatment of wounds. In conjunction with other studies, we previously demonstrated that the topical application of silver nanoparticles (AgNPs) can promote wound healing through the modulation of cytokines. Nonetheless, the question as to whether AgNPs can affect various skin cell types—keratinocytes and fibroblasts—during the wound‐healing process still remains. Therefore, the aim of this study was to focus on the cellular response and events of dermal contraction and epidermal re‐epithelialization during wound healing under the influence of AgNPs; for this we used a full‐thickness excisional wound model in mice. The wounds were treated with either AgNPs or control with silver sulfadiazine, and the proliferation and biological events of keratinocytes and fibroblasts during healing were studied. Our results confirm that AgNPs can increase the rate of wound closure. On one hand, this was achieved through the promotion of proliferation and migration of keratinocytes. On the other hand, AgNPs can drive the differentiation of fibroblasts into myofibroblasts, thereby promoting wound contraction. These findings further extend our current knowledge of AgNPs in biological and cellular events and also have significant implications for the treatment of wounds in the clinical setting.     

Morphology and Rheological Behaviors of Polycarbonate/High Density Polyethylene in situ Microfibrillar Blends

Summary: Polycarbonate (PC)/high density polyethylene (HDPE) in situ microfibrillar blends were fabricated by a slit die extrusion, hot stretching, and quenching process. Despite PC and HDPE having a high viscosity ratio, which is usually disadvantageous to fibrillation, the morphological observation indicated that the blends had well‐defined PC microfibrils. The size and amount of the PC fibrils were nonuniform through the thickness of the extrudate, and were also affected by the PC concentration and hot stretch ratio. There were coarse and dense fibrils in the core zone, while these fibrils became finer and reduced in number toward the surface. The melt flow rate (MFR) of the PC/HDPE microfibrillar blend decreased with the increase of PC concentration, but increased with the larger hot stretching rate (or hot stretching ratio, HSR). Besides, it was found that the fibrillar blend had better flowability than the common blend with spherical particles at the same PC concentration. Temperature was also an important factor influencing the MFR due to the temperature dependence of PC and HDPE viscosity, and the PC phase morphology. The PC microfibrils could not be preserved beyond 230 °C and transformed into spherical particles. The rheological behaviors at various shear rates were studied by capillary rheometer. The orientation of PC fibrils and HDPE molecules with higher shear rate led to a decrease in the viscosity of microfibrillar blend. The data obtained in this study can help construct the technical foundation for recycling and utilization of PC and HDPE waste by manufacture of microfibrillar blends in future work.

SEM micrograph of the PC/HDPE microfibrillar blend.     

载银介孔氧化硅防污剂的制备及其防污机理研究

采用化学法制备出载银介孔氧化硅(Ag-MSN)粉体,通过扫描电镜(SEM)和透射电镜(TEM)表征纳米材料的微观形貌和尺寸,利用X射线衍射(XRD)确定纳米材料的成分并结合公式确定纳米银的粒径;通过平板培养法和分光光度计法揭示载银介孔氧化硅对于海洋微生物(需钠弧菌)的抗菌效果和机理。将载银介孔氧化硅粉体作为主要颜料与有机硅树脂复合,得到具有一定抑菌性能的涂层。该研究成果将有助于揭示纳米银防污机理,并对绿色海洋防污剂的制备与应用起到重要的促进作用。     

高浓度∑Fe对硝酸银滴定法测定Cl-干扰的消除

采用硝酸银滴定法测定含高浓度铁离子溶液中的Cl-时,需要调整pH到6.5~10.5,产生氢氧化铁与氢氧化亚铁沉淀,影响滴定终点的判定,导致分析结果不准确。本研究在含不同高铁浓度模拟溶液中加入氢氧化铝胶体洗涤出铁离子,再用硝酸银滴定法分析Cl-浓度,结果显示在Cl-浓度20 mg/L时,相对偏差小于5%,浓度为200 mg/L时,相对偏差最大为1.03%,并把该方法应用在分析花岗岩铀矿浸出液中的Cl-浓度,与采用选择氯离子电极法分析结果对比,结果表明了这两种方法的分析结果相差不大。因此该方法消除高铁对硝酸银滴定法分析氯离子是可行的。