自组装式密堆积的胶体单层膜

本文介绍了一种没有使用任何特殊实验装置的、简单和方便的技术用来制备胶体晶体。我们研究了有机硅氧烷(Si(OR)4)在氢氧化铵和乙醇为媒介中的水解和缩合反应,尤其着重于研究氢氧化铵的浓度大小、温度高低和正硅酸乙酯(TEOS)对化学反应产生的影响。通过粒度表征发现,颗粒粒径大小与氢氧化铵浓度成正比,与TEOS浓度成反比。在同一氢氧化铵浓度下,温度高低与粒径大小成反比。本文在不同实验标准下制备二氧化硅颗粒,得到的可重复性误差小于12%。为了得到不同的表面化学性质,在表面硅烷化反应中使用带有四种不同化学基团的有机硅烷(苯基、十二烷基、氨基和氟基)。对合成颗粒所采用的表征手段有:热重分析(TGA)、傅里叶变换红外光谱(FT-IR)和Zeta电位测量。本实验以倾斜角为9°度的角度法制备密堆积的胶体单层膜,研究了悬浮液体积、体积分数、沉积溶剂和颗粒表面化学对其产生的影响。最后,本研究认为,当阵列的颗粒直径是550 nm时,实验最理想的条件是:使用50μl乙醇作为沉积溶剂,经过十二烷基改性的体积分数0.1%的二氧化硅颗粒悬浮液。     

蒸发自组装法制备聚苯乙烯胶体晶体

采用乳液聚合法制得亚微米级聚苯乙烯单分散微球,并用蒸发自组装法在乳液气-液界面进行自上而下的层层组装,制得了厚度在450μm以上的三维有序胶体晶体。结果表明,影响胶体晶体有序性的关键因素是对蒸发速度的控制,促使胶体晶体规则排列的最主要作用力为溶液的毛细管力。在胶体晶体组装末期,随着溶剂量的减少,空间阻力逐渐增大,微球对流能力下降,造成胶体晶体的有序性降低。     

SiO2胶体晶体垂直沉积自组装方法的改进

采用垂直沉积技术及相应的改进方法,使用化学合成的400 nm单分散二氧化硅微球自组装制备了胶体晶体薄膜。通过扫描电镜与分光光度计对样品的微观结构与透过光谱进行了表征,并对比研究了不同的垂直沉积方法对胶体晶体的影响。结果表明,通过温度与流量控制两种改进手段,均能制备具有六方密堆结构周期排列的胶体晶体薄膜。在垂直沉积过程中适当的升高温度有利于降低胶体粒子的用量,而通过流量控制的垂直沉积技术则可以有效缩短自组装时间。通过调节蠕动泵改变液面与基板的相对运动速度,或者调控温度改变胶体溶液的蒸发速率,可在材料表面形成单层或多层的胶体晶体薄膜。改进的垂直沉积技术将有望应用于快速沉积大面积、高质量的胶体晶体材料。     

SiO2胶体颗粒的三维有序自组装

由SiO2胶体颗粒的三维有序自组装可以得到面心立方三维结构,它具有折射率周期性变化的特点。它的制备涉及胶体化学、材料科学等学科的前沿领域。其自组装方法包括胶体颗粒的沉降自组装、胶体颗粒在物体限制下的自组装、胶体颗粒的连续对流自组装和利用胶体颗粒表面电性质的自组装。本文对这些组装方法进行了介绍。     

聚苯乙烯光子晶体的制备及其在传感中的应用

以基于毛细作用的垂直沉积法将单分散的二氧化硅胶体微球自组装成光子晶体．在二氧化硅光子晶体的多孔结构里填充聚苯乙烯甲苯溶液,经甲苯挥发,通过氢氟酸处理去除二氧化硅模板,制备出精美的聚苯乙烯光子晶体．研究表明：保留了模板有序多孔结构的聚苯乙烯能被用来作为敏感膜,这使得其在基于折射率变化的传感应用中具有潜在的价值．     

简单对流自组装制备层数可控有序阵列（英文）

利用简单的方法和较少的胶体乳液,在没有任何特殊设备的情况下制备出了二维和三维的有序阵列。通过控制胶体乳液浓度获得了层数可控的胶体晶体有序阵列。通过使用现有成膜模型模拟沉积行为揭示胶体晶体阵列在生长过程中控制冷凝蒸发过程的机理,对自组装过程中颗粒转移和溶剂蒸发之间的平衡细节进行了详细的讨论。利用阵列横截面的SEM显微照片来观测样品的厚度和均匀性,通过反射光谱来观察样品的光学性质。     

简单对流自组装制备层数可控有序阵列

利用简单的方法和较少的胶体乳液,在没有任何特殊设备的情况下制备出了二维和三维的有序阵列.通过控制胶体乳液浓度获得了层数可控的胶体晶体有序阵列.通过使用现有成膜模型模拟沉积行为揭示胶体晶体阵列在生长过程中控制冷凝蒸发过程的机理,对自组装过程中颗粒转移和溶剂蒸发之间的平衡细节进行了详细的讨论.利用阵列横截面的SEM显微照片来观测样品的厚度和均匀性,通过反射光谱来观察样品的光学性质.     

磁性微球的制备及应用

磁性微球在生物医学和分离工程等多个领域都有广泛的应用,如固定化酶、靶向药物载体、核磁共振成像、细胞标记及分离、核酸和蛋白质分离纯化、环境治理等.近年来随着纳米新材料及制备工艺的不断创新,磁性微球的制备及应用都取得了大量进展.磁性微球的制备方法主要可以分为4类:(1)包裹法,在微球生成的同时将磁性纳米颗粒包裹在微球基质内,又可以细分为异质聚合法、乳化-溶剂挥发法、膜乳化和微流控技术、反相悬液-交联法、Stober法、聚合诱导胶体聚集法等;(2)模板组装法,在模板微球内部或表面组装磁性纳米颗粒,包括溶胀法、吸附法和静电自组装法等;(3)模板原位生成法,在模板微球的内部或表面原位生成磁性纳米颗粒,包括共沉淀、沉淀-氧化法、有机前驱体热分解法等;(4)溶剂(水)热法,以有机溶剂或水为介质,密闭体系中的反应物在一定的温度和溶液的自生压力下反应得到磁性微球.本文按照制备方法对近几年来磁性微球领域的研究进展进行了总结,包括反应原理、磁性微球的性质、表面功能化和应用介绍.     

表面富含羧基的单分散交联聚合物微球的快速自组装制备胶体晶的研究

在20～70℃范围内,用垂直沉积的方法可使表面富含羧基的单分散交联聚合物微球在不同的基底上快速自组装成三维有序的胶体晶.不同粒径的微球形成的胶体晶其光禁带峰位不同,因此可调控不同波长的光在胶体晶中的传播.利用紫外-可见光谱研究了胶体晶的光禁带峰位与组成其微球粒径之间的关系.结果表明,随着构成胶体晶微球粒径的增大,胶体晶光禁带峰位发生了红移,而随着入射光角度的增大,胶体晶的光禁带峰位发生了蓝移.利用原子力显微镜和扫描电子显微镜研究了其它条件对聚合物微球有序排列的影响,发现聚合物微球在pH值为3.0～13.0范围内可以形成三维有序自组装胶体晶.这是由于在不同的pH值下,聚合物微球表面发生羧基化及去羧基化反应,导致在自组装过程中微球之间和微球与介质之间作用力的变化     

悬浮液气-液界面二元胶体颗粒的漂浮组装机理

提出一种在悬浮液气-液界面漂浮组装亚微米单分散聚苯乙烯(PS)微球和纳米SiO2颗粒二元胶粒晶体的新方法, 并系统研究了漂浮组装机理. 研究表明, 聚苯乙烯微球和二氧化硅两种胶体颗粒在悬浮液气-液界面的漂浮组装是以PS微球的组装为主导的. 在一定PS微球相浓度范围内, 悬浮液中PS 微球与SiO2颗粒的初始体积配比基本不影响PS微球有序组装的形成. PS微球粒径在150-500 nm时易于形成有序排列, 较小或较大粒径的PS微球难以形成有序排列. SiO2颗粒的组装是一种以PS微球为“基底”的沉积过程. 二元胶粒晶体中SiO2颗粒的体积分数由其在混合悬浮液中的相浓度所决定.     

有机非线性光学晶体NPP的AFM研究

有机二阶非线性光学活性晶体的分子设计和晶体工程是复杂而又引人注目的课题．有机非线性光学晶体N一忡硝基苯基）－LWe脯氨醇（NPP）是一个极为成功的自］子山．由于在＊＊P分子中引入了含手性碳原子和可形成分子间氢键的电子给体脯氨醇，使得其分子跃迁偶极矩与单科P21晶体结构的二重轴之间的夹角为586”．接近于理论优化值（54．74”），因此，＊＊P具有很高的宏观二阶非线性光学活性，其粉末二次谐波强度为尿素的150倍．自1984年首次报导以来，对它的晶体生长门和物理性质已进行了广泛深入的研究．原子力显微镜（＊＊M）能够以极高…     

Comparison of epithelial and fibroblastic cell behavior on nano/micro-topographic PCL membranes produced by crystallinity control

In this study, the relationship between the cellular morphology and the material surface topography was investigated. Poly(ε-caprolactone) (PCL) membranes were prepared in a wide range of surface wettabilities by means of crystallinity-controlled solvent casting process. Membrane surfaces were characterized by atomic force microscope (AFM), scanning electron microscope (SEM), and static/dynamic water contact angle measurements. It was found that solvent evaporation and non-solvent (methanol) addition to the solvent (THF) are the most decisive parameters to change the surface topography. The non-solvent addition and the decrease in solvent evaporation temperature from room temperature to -20 °C caused increased polymeric chain mobility and crystallization time. Such changes in crystallization parameters led to the formation of micro/nano-sized features on the membrane. Cell culture studies indicated that in contrast to Madin Darby kidney (MDBK) epithelial cells, L929 mouse fibroblast preferred rough and porous surfaces.     

Patterning in rapidly evaporated polymer solutions: formation of annular structures under evaporation of the poor solvent

Patterning in the intensively evaporated polymer solutions based on polystyrene and poor solvent (acetone) was investigated. SEM and AFM studies demonstrated that annular elements of the surface topography are formed in this case, in contrast to the honeycomb patterns obtained under the evaporation of the good solvent (chloroform). The authors suggest that the theory of viscous dewetting developed by de Gennes explains the phenomenon satisfactorily.     

Trapping Nanostructures on Surfaces through Weak Interactions

The assembly of imidazole‐functionalized phenanthroline‐strapped zinc porphyrins (ZnPorphen) with alkyl or polyethylene glycol (PEG) side chains was studied in solution and by AFM after casting on highly oriented pyrolytic graphite (HOPG) or mica. The nature of the solvent and its evaporation time influenced the morphology of the objects observed. On HOPG, short rods of about 100 nm were observed after fast evaporation of solutions of the alkyl derivatives in CHCl₃, THF, or pyridine, whereas islands of aligned rows of longer wires were obtained from methylcyclohexane (MCH). Slow evaporation of MCH led to a three‐dimensional assembly. The PEG porphyrin assembled into short wires on HOPG or fibers on mica after slow evaporation of solutions in THF. This study shows the role of surface–molecule interactions in the interfacial assembly of ZnPorphen derivatives and contributes to understanding the parameters that control their noncovalent assembly into molecular wires on a surface.     

Retardation of water evaporation by less-defective mixed monolayers spread from bulk solids onto water surface

From AFM observation of transferred films on mica, it has been found that mixed monolayers of hexadecanol with poly(vinyl stearate) give a film with a less-defective and flat surface by spreading from bulk solids of those mixtures onto a water surface without using any organic solvent. As a result, those mixed monolayers have a considerably larger effect on retardation of water evaporation in comparison with those spread from the solution of the mixtures. After the saturated surface pressure of the mixed monolayer spread from the bulk solids, an enhanced effect on retardation of water evaporation was found, accompanied by the preferential spreading of hexadecanol and the gradual reduction of defects in the mixed monolayer.     

Characteristics of thin cellulose ester films spin-coated from acetone and ethyl acetate solutions

Spin-coated films of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB) and carboxymethylcellulose acetate butyrate (CMCAB) have been characterized by ellipsometry, atomic force microscopy (AFM) and contact angle measurements. The films were spin-coated onto silicon wafers, a polar surface. Mean thickness values were determined by means of ellipsometry and AFM as a function of polymer concentration in solutions prepared either in acetone or in ethyl acetate (EA), both are good solvents for the cellulose esters. The results were discussed in the light of solvent evaporation rate and interaction energy between substrate and solvent. The effects of annealing and type of cellulose ester on film thickness, film morphology, surface roughness and surface wettability were also investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The influence of UV-radiation on hyaluronic acid and its blends with addition of collagen and chitosan

In this paper, the results regarding the influence of UV-irradiation with 254?nm wavelength on the surface and mechanical properties of hyaluronic acid, hyaluronic acid/collagen and hyaluronic acid/collagen/chitosan mixtures are presented. For this study, thin films were prepared by solvent evaporation from solution of HA and mixtures made from HA/Coll and HA/Coll with 30% addition of chitosan. The surface properties of films were investigated by AFM and using contact angle measurements, allowing the calculation of surface free energy and its components. Mechanical properties of films made of biopolymeric blends before and after UV-irradiation have been investigated by mechanical testing machine.     

Characterization of counterion and surface influence on micelle formation using tapping mode atomic force microscopy in air

Cylindrical micelles prepared in aqueous solutions from cationic surfactants octadecyl trimethylammonium (OTA+) or cetyltrimethylammonium (CTA+) and parachlorobenzoate (PCB) counterion were successfully imaged after evaporation of water using tapping mode atomic force microscopy (TM-AFM) onto very smooth gold and glass substrates. With the help of the obtained topography AFM images, it was shown that the micellar structures are preserved on gold substrates after evaporation of the solvent despite the new set of stresses due mainly to capillary forces and dehydration. The influence of the substrate on the resulting micellar morphology observed in air was investigated for these two materials: cylindrical micelles were evidenced as loosely adherent on gold surface in the presence of parachlorobenzoate (PCB) and identical, geometrically speaking, to those known to exist in aqueous solutions. In this situation, topographic AFM images allowed us to determine accurately their geometrical characteristics such as diameter and length in the nanometer range. On the other hand, AFM images obtained in air on glass surfaces revealed micellar structures that are different from those existing in the bulk of the solution. Indeed, bilayer-type micelles with a thickness close to twice the surfactant monomer expected length were observed, indicating that the well-established and strong influence of glass on micelle geometry at the glass/solution interface is maintained after evaporation of water. These results have been analyzed on the basis of positive charge of gold deduced from electrochemical impedance spectroscopy (EIS) and Raman spectroscopy measurements on one hand and of the negative charge of glass on the other hand. Although these results appeal to new theoretical considerations dealing with dynamics of evaporation of micellar solution drops and/or with counterion contributions to macromolecular interactions in aqueous solutions and in air, this new AFM imaging method appears to be the more adequate one to image and measure the micelles formed in the presence of water.     

非对称双嵌段共聚物薄膜在平板受限和溶剂蒸发下自组装行为的分子模拟研究

采用模拟退火和Monte Carlo方法研究体相形成柱状相的双嵌段共聚物薄膜在平板受限和溶剂蒸发条件下的自组装,特别关注柱状相形貌的取向.对于平板受限下的薄膜,研究了表面选择性、溶剂选择性和膨胀程度对柱状相取向的影响.对于溶剂蒸发的薄膜,研究了表面选择性和薄膜厚度对柱状相取向的影响,并讨论了柱状相取向的机理.结果表明,薄膜内存在中性溶剂时形成垂直柱形貌的表面选择性范围较小;存在亲长嵌段的溶剂时形成垂直柱形貌的表面选择性范围较大.溶剂蒸发后薄膜生成垂直柱形貌的参数范围较热退火下增大;柱状相取向取决于蒸发过程中体系由球状相演化为柱状相时的薄膜厚度与体相周期的匹配性.     

Effect of rubbing load on nanoscale charging characteristics of human hair characterized by AFM based Kelvin probe

The manageability and feel of human hair is significantly affected by its surface charge. Understanding and developing ways to control charge build up is hence highly beneficial. Previous studies have looked at static charging characteristics of hair on a macroscale. In this study, static charging characteristics of hair are studied on the nanoscale with an AFM. Hair is charged by rubbing a control area on its surface with an AFM tip, to which a small voltage bias is applied. The resulting charge distribution is characterized by measuring the surface potential of the control area in situ with AFM based Kelvin probe microscopy. The rubbing load is progressively increased, and the effect of this increase on the charge build up is assessed. Virgin, damaged and conditioner treated hair samples are studied for a better understanding of charge build up and dissipation. Relevant mechanisms are discussed.