不同表面性质聚电解质多层膜的制备及蛋白质吸附和血液相容性能

利用层层自组装方法制备了聚烯丙基铵盐酸盐(PAH)/聚苯乙烯磺酸钠(PSS)多层膜. 通过吸附或共价偶联, 在多层膜表面修饰了聚乙二醇(PEG)、牛血清白蛋白(BSA)或肝素, 通过石英晶体微天平(QCM)、椭圆偏振光谱和原子力显微镜(AFM)研究了多层膜的表面形貌及修饰方法对各种蛋白的吸附性能. 经修饰后的多层膜较基底膜的厚度均有所增大; 最外层经修饰后的多层膜吸附的BSA、纤维蛋白原及血浆蛋白的量较未修饰多层膜均有所减少. 采用SEM观察了血小板在多层膜上的黏附情况和形态变化, 计算了血小板的黏附率. 比较各多层膜的凝血酶原时间(PT), 发现修饰后的多层膜的凝血酶原时间均有所延长, 但各组间无显著性差异.     

冷冻干燥法制备天然高分子复合聚电解质纳米纤维

将壳聚糖(CS)溶液和透明质酸钠(SH)溶液共混,制备成CS-SH复合聚电解质溶液,并对溶液中所形成的胶粒进行了粒径分布和ZETA电位表征。用冷冻干燥法除去溶剂,制备了 CS-SH复合聚电解质纳米纤维膜。用FT-IR对其结构进行分析,并用SEM对其形貌进行了表征。并将复合聚电解质纳米纤维膜作为疏水性药物紫杉醇(PTX)的载药体系,研究了其药物释放行为。结果表明,PTX在该载体中的释放较为平缓,这可以延长药物的有效时间,降低给药次数,增强治疗效果,降低药物的毒副作用。     

聚(3-己基)噻吩/紫精掺杂聚氧乙烯体系的电双稳态存储特性研究

制备基于聚(3-己基)噻吩/(乙基紫精二高氯酸盐掺杂聚氧乙烯)(P3HT/(PEO+EV))双聚合物薄膜层的OFET型器件,研究P3HT/(PEO+EV)体系的电响应特性.结果表明该体系可以在+3 V的电压下由OFF态跃迁为ON态(写入信号),而在-3 V的电压下由ON态转换成为OFF态(擦除信号);在OFF和ON态转换之后,导电态能保持稳定,因此该体系具备良好的阻变电双稳态存储特性,开关电流比高达105.尽管器件ON态电流随时间表现出一定的衰减,在经过大约2800 s读取操作以后,体系仍然可以进行写入/擦除操作.采用共聚焦激光扫描显微镜技术研究体系的电存储机理,结果显示信号写入过程中P3HT层发出的荧光随着施加电压由S极向D极逐渐淬灭,淬灭过程大约需要0.167 s,这表明P3HT极化子在S电极生成,并在沟道内传递至D电极,传递速率大约是120 m/s;而信号擦除过程荧光快速恢复,表明P3HT极化子被还原成为本征态P3HT.     

Aggregation-induced emission of an aminated silole: A fluorescence probe for monitoring layer-by-layer self-assembling processes of polyelectrolytes

A new fluorescence technique for monitoring layer-by-layer self-assembling processes of polycations and polyanions is developed in this work. The fluorescent probe is a fluorogenic dye named 1,1-bis[p-(diethylaminomethyl)phenyl]-2,3,4,5-tetraphenylsilole (A₂HPS). Whereas fluorescence of a “normal” fluorophore is often quenched by aggregate formation, the protonated salt of A₂HPS, i.e., [H₂A₂HPS]²⁺, emits strong light in the suspensions of its nanoaggregates and in the solid films of its blends with poly(diallyldimethylammonium chloride) (PDDAC), thanks to its novel aggregation-induced emission (AIE) characteristics. When ([H₂A₂HPS]²⁺+PDDAC) cations and poly(styrenesulfonate) (PSS) anions were used to fabricate thin films via layer-by-layer deposition processes on quartz and glass substrates, the emission intensity of [H₂A₂HPS]²⁺ showed linear relationship with the number of ([H₂A₂HPS]²⁺+PDDAC)/PSS bilayers, due to the uniform co-deposition of [H₂A₂HPS]²⁺ cations into the PDDAC/PSS bilayers. This proves that the AIE fluorophore is an excellent probe for monitoring the layer-by-layer self-assembling processes of the polyelectrolytes on various substrates.     

Embedding copper nanoparticle-anchored conductive nano-blocks in polyelectrolyte

Conductive carbon nanotubes （CNTs） or alternatively polyaniline （PANI） nano-blocks was introduced into aqueous solutions of polyvinyl alcohol （PVA） and copper （II） salt, to assist the reduction of copper （II） ions and the anchoring of the resulting copper nanoparticles onto the conductive blocks. The mixture solutions of nano-blocks, copper （lI） salts and PVA were spin-coated onto the cathode surface, forming swollen cathode films （SCFs）. The copper （II） ions in the film assembled onto the surfaces of the conductive blocks and were then reduced under an appropriate voltage. It is important that the copper nanoparticles grew only on the surfaces of the conductive blocks. PVA which acted as the matrix of the composites played a role in stabilizing the resulting copper nanoparticles. Morphologies of these polymeric composite films were studied by various characterization methods. Moreover, the mechanism of migration of copper （II） ions, the formation of these polymeric composites, and the overall procedure were investigated in detail.     

Fabrication of microelectrodes using flow layer-by-layer self assembly of gold nanoparticles

Microelectrodes to be used in microfluidic devices were prepared from the layer-by-layer flow deposition of gold nanoparticles. Pre-designed microfluidic channels were used as templates for the flow driven deposition of the nanoparticles in sequence with poly (diallyldimethyl amonium chloride) (PDADMAC). The electrical resistivity of the gold nanoparticle assembly was found to be strongly dependant on the concentration of sodium citrate used in the gold nanoparticle synthesis. As the electrical properties of the film changed from insulating to conducting when decreasing the citrate concentration, a 4 point probe setup was used to measure the resistivity of the film. Near bulk conductivity (5.42 × 10⁻⁶ Ω cm) was achieved with only 10 layers of film. The thickness and morphology of the flow-printed multilayer microelectrode was characterized using atomic force microscopy (AFM) and a field emission scanning electron microscope (FE-SEM). To demonstrate its usefulness, the microelectrode assembly was then tested toward the detection of KCl in solution, having a concentration ranging from 1 to 20 mM using AC current detection in a simple setup. Good linearity and stability of the electrode confirmed that this method could be very convenient for the fabrication of microelectrodes for lab-on-chip applications.     

Enzyme-catalyzed modification of PES surfaces: reduction in adsorption of BSA, dextrin and tannin

The effect of pH on the build-up of polyelectrolyte multilayers, PEMs, composed by poly-L-lysine and heparin onto two different substrates, silica and gold, has been studied by means of ellipsometry and quartz crystal microbalance with dissipation, QCM-D. Ellipsometry results indicate that the dry mass grows exponentially with the number of layers, and that this amount is larger as the pH values are raised. From QCM-D data the viscoelastic properties of the multilayered structure have been obtained. These data reflect that PEMs become more viscoelastic as the pH values are increased for silica substrates, while for gold the highest viscoelastic behavior is obtained at neutral pH and the elastic behavior becomes dominant as the pH is further increased or decreased. By combining these two surface techniques it has been also possible to determine the solvent content in the multilayers and reach a deeper understanding of the internal structure.     

Early-stage flocculation kinetics of polystyrene latex particles with polyelectrolytes studied in the standardized mixing: Contrast of excess and moderate polyelectrolyte dosage

Standardized mixing procedure was applied to the analysis of flocculation of polystyrene latex (PSL) particles with polyelectrolytes. After confirming the initial enhancement of flocculation rate in the very beginning followed by abrupt stop with excess dosage, attention was shifted to the system of moderate dosage. In the former, effects of ionic strength were further analyzed to find the consistency with adsorption isotherm. In the latter, flocculation started slowly in the beginning, sometime slower than salt-induced rapid coagulation, however, the rate gradually increases in the middle stage. Often, the increased rate exceeds that of salt-induced rapid coagulation. This behavior emerged more clearly in the case of lower ionic strength. This is the indication that the rate of relaxation of polymer on the colloidal surface is a function of surface coverage and ionic strength. The ultimate degree of flocculation is usually higher than that observed for excess dosage. The size distribution of flocs was also examined, however, no clear difference between different experimental conditions was confirmed for the same degree of flocculation.     

NRET from naphthalene labels in multilayer shell wall on melamine formaldehyde microparticles fabricated with layer-by-layer self-assembly to pyrene-labeled polyelectrolyte in solution

Core-shell colloidal particles were prepared with the core of monodisperse melamine formaldehyde particles (MF) with a diameter of 3.5 μm. The shell deposited on the core by the layer-by-layer (LbL) self-assembly was made with a copolymer ANp3 of 2-acrylamido-2-methylpropanesulfonate sodium (AMPS) and 3 mol% naphthalene label monomer and poly(diallyldimethylammonium chloride) (PD). Nonradiative energy transfer (NRET) from the naphthalene labels deposited on the MF particles to pyrene labels at a polyelectrolyte APy3, a copolymer of AMPS and 3 mol% pyrene label monomer, or to an ionic pyrene probe 1-pyrenemethylamine hydrochloride (PyMeA · HCl) in water was observed. The NRET efficiency was expressed as the emission intensity ratio I/I₀ of naphthalene with and without existence of pyrene in the surrounding solution. With increasing pyrene concentration, I/I₀ decreased down to about 0.2 and the mechanism for this NRET from the inner naphthalene label to the pyrene labels in solution is still ambiguous.