孙俊奇
论文题目：纳米结构三维组装与功能化研究
作者简介：孙俊奇，男，1975年02月出生，1998年09月师从于吉林大学沈家骢教授和张希教授，于2001年06月获博士学位。
摘 要
自组装多层膜的研究已经引起了来自不同领域的科学家的广泛兴趣。到现在为止，数不清的物质，包括带电荷和不带电荷的物质，已经被科学家们利用种种手段组装入膜。自组装多层膜主要存在于气/液或液/固界面上，且很容易通过层状组装技术来获得。1991年，Decher发展了一种基于阴阳离子静电作用为推动力的制备多层膜的方法，由此揭开了自组装超薄膜制备与研究的新篇章.
多层膜研究的一个重要目标就是：了解结构与功能间的关系，并最终实现多层膜制备中功能的集成。在多层膜的研究中，下述问题应引起人们的注意：（1）单层膜的构筑，因为单层膜是构成多层膜的基元；（2）相邻层（界面）间的扩散控制；（3）单层膜的厚度调控；（4）图案化多层膜的制备；（5）多层膜中的相转移问题；（6）层间的能量和电荷转移；（7）膜的稳定性，等。本论文的研究工作主要围绕着三个方面展开：（1）将电活性的含有锇配合物的聚（4-乙烯基吡啶）阳离子（PVP-Os）与葡萄糖氧化酶交替沉积，实现了酶与电极间的较为容易的电子转移。进一步，以PVP-Os为电活性物质，通过与导电的磺化聚苯胺或Au微粒交替沉积，实现了化学修饰电极的优化。（2）将静电组装技术和膜间的原位化学反应相结合，发展了一种制备共价键和多层膜的方法。它可很容易地实现含有磺酸基团和羧酸基团的带电物质的稳定组装。（3）将静电组装技术和电泳技术相结合，发展了一种电场诱导的层状组装技术，它是一种简便易行的、可在基片水平方向控制多层膜沉积的有效方法。这种技术可用于制备横向可控的、结构复杂的多层膜图案化结构。
聚(4-乙烯基吡啶)锇配合物(PVP-Os)是一类电化学性质优异的聚电解质。在本论文的第二章，以PVP-Os作为聚阳离子，于石英和金表面，制备了PVP-Os与葡萄糖氧化酶（GOD）的静电沉积多层膜。循环伏安实验表明以此多层膜为修饰电极成功实现了葡萄糖氧化酶到电极表面的电子转移。PVP-Os起到了电子转移中介体的作用。此种方法可望用来制备新型的葡萄糖传感器。通过静电组装技术，电活性的聚阳离子PVP-Os还可以和聚阴离子聚（4-苯乙烯磺酸钠）（PSS）或磺化聚苯胺（PAPSAH）在金电极上组装，获得多层膜。这样修饰的金电极可以催化亚硝酸根的还原。将不导电的PSS换成导电的PAPSAH，电极上电子的传输将变得容易得多，而且所获得的修饰电极对亚硝酸根有更好的电化学响应。这说明，通过与导电的对离子化合物组装，可以在一定程度上优化化学修饰电极的性能。进一步，将PVP-Os与表面荷负电的Au微粒交替组装，制备了PVP-Os/Au修饰的电极，与PVP-Os/PSS修饰的电极相比，它有两个优点：(1)PVP-Os/Au上的电子传输更快，这是由Au微粒的良好导电性决定的；(2)PVP-Os/Au电极上负载的电活性PVP-Os的量多，这是由金微粒造成的膜的大的粗糙度决定的。这说明，结合于多层膜中的电活性物质性质的发挥强烈地依赖于其所在组装体中的存在方式，通过选用导电的聚苯胺或金微粒与电活性物质组装，可以大大提高所制备的化学传感器的性能。这种思路提供了一种提高化学修饰电极性能的新途径。
在第三章中，我们发展了一种制备共价键合多层膜的新方法。选择带正电荷的重氮树脂和带负电荷的聚（4-苯乙烯基磺酸钠），先制备它们的静电组装多层膜，再将此多层膜置于紫外光下，诱导重氮基团与磺酸盐基团之间的光化学反应，生成磺酸酯，便制得了共价键合的多层膜。它充分利用了层状静电组装的简单性这一特点，并结合了重氮基团与磺酸基团在膜内的光化学反应，使膜内的离子键转变成共价键，从而使膜的稳定性大大提高。就制备共价键合的多层膜而言，此技术具有以下特点：它兼具有层状静电组装操作简单的特点，同时也允许共价键合的单层膜的厚度在纳米尺度范围内进行调控。由于所使用的DAR具有感光性，这种技术可望用来制备稳定的、纳米级的图案化表面。通过将光反应性的重氮树脂与含有磺酸基团的小分子染料交替沉积，并利用重氮基团与磺酸基团之间的光化学反应，成功地制备了共价键合的小分子染料多层膜，使小分子染料在膜中的稳定性大大提高。由于在膜中进行的光反应的不彻底性，使得我们可以对所得的多层膜结构进行进一步的调整。一种方法是通过在DAR/小分子染料多层膜上覆盖几层光反应性的DAR/PSS膜，可以进一步提高膜中小分子的稳定性；另一种是，通过溶剂刻蚀，脱附掉部分未以共价键结合的小分子染料，在膜上制造出便于离子或底物传输的“人造通道”，使得此类膜在化学修饰电极方面具备了潜在的应用前景。用层状组装技术，制备了DAR/PAA多层膜，其成膜推动力既包括静电作用，又包括氢见作用。在紫外光照下，膜中与重氮基团相连的苯环和羧酸盐基团反应生成羧酸酯，提高了膜的稳定性。它进一步拓宽了利用层间光化学反应提高膜稳定性这一技术的应用范围。
在第四章中，基于电泳技术和静电层状组技术，成功地发展了一种电场诱导的层状组装技术。以带正电荷的PDDA和带负电荷的巯基乙酸修饰的CdTe微粒为模型化合物，此技术成功地实现了PDDA/CdTe微粒在ITO和金表面的选择性沉积，制备了基于不同尺寸CdTe微粒为发光物质的双色发光器件。考虑到静电组装技术的对物质选择的广泛性和带电荷物质在给定电场下的稳定性，电场诱导的层状组装技术将会适用于一系列的包括聚电解质、有机小分子、无机/有机纳米微粒、生物分子等在内的物质的选择性沉积。静电层状组装技术不仅适用于带电物质在导电基底上的选择性吸附，而且也适合于将一些不易用静电组装技术成膜的物质在借助电场的帮助下组装成膜。
Nanostructures and Functionalization of
Three-dimensional Assemblies
Abstract
The research of
self-assembled multilayer films has attracted attention of scientists from all
areas in recent years. Numerous materials, including charged and uncharged
materials have been incorporated into multilayers by exploiting various
techniques. In general, self-assembled multilayer films exist at the interfaces
of gas/liquid or liquid/solid and are easy to achieve by self-assembly
techniques. In 1991, G. Decher developed a way to fabricate multilayer
structures which makes full use of the electrostatic interaction between
cationic and anionic groups as driving force. This technique has been proven to
be a rapid and experimentally very simple way to produce complex layered
structures with precise control of layer composition and thickness. It has been
regarded as an important milestone for the research of multilayer films. One of
the most important goals in the research of multilayer film is to understand
the structure-function relationship and ultimately
integrate nano-architecture and functions in one self-assembling system. Some basic
problems remaining in thin film research should attract the attention of
researchers: (a) monolayer and multilayer architecture, including composite
films, (b) diffusion controlled interfaces, (c) control over the monolayer
thickness, (d) patterning formation, (e) phase transition, (f) charge and
energy transfer between layers, (g) stability, etc. The research work of this
dissertation mainly focuses on three aspects: (1) to fabricate multilayer films
composing of cationic poly(4-vinylpyridine) complex with Os (PVP-Os) and
anionic glucose oxidase (GOD) on a Au electrode and realize the successful
electron transfer between GOD and the electrode surface. Furthermore, to
assemble PVP-Os with conductive polyanionic poly[aniline-co-N-(3-sulfopropl)aniline]
or Au particles and developed a way to optimize the resulted chemically modified
electrodes. (2) To combine the layer-by-layer self-assembly technique with
in-situ photoreaction and develop a simple way to fabricate covalently attached
multilayer films. This way is suitable for preparing covalently attached
multilayer films using building blocks containing sulfonate and carboxylic acid
groups. (3) To combine the layer-by-layer self-assembly technique with
electrophoretic technique and develop an electric directed layer-by-layer
assembly technique (EFDLA). It has the ability to easily control the deposition
of charged materials in the horizontal direction of the substrate. This
technique is particularly suitable for the fabrication of multilayer pattern
surfaces with complex structures.
Poly(4-vinylpyridine) complex with Os (noted PVP-Os) is a kind of excellent electroactive polycation. In chapter 2, we have prepared multilayer films composing of PVP-Os and GOD on quartz and Au surfaces. Cyclic voltammetry shows that successful electron transfer can be realized between the redox centers of GOD and the electrode surface where PVP-Os acts as electron relay beween GOD and electrode surface. A glucose sensor could be produced based on this concept of introducing electron relay to facilitate the electron transfer. Electroactive PVP-Os can alternately assemble with
poly(4-styrenre sulfonate)
(PSS) and poly[aniline-co-N-(3-sulfopropl)aniline] (PAPSAH) on Au
surfaces. Thus modified Au electrode is capable of catalyzing the reduction of
nitrite. It has been proven that when inconductive PSS was replaced with
conductive PAPSAH, the electron transfer on the electrode can become more rapid
and the response of the electrode to nitrite can become better. All these
results show that by carefully selecting the conductive counter polyion during
multilayer fabrication, the property of the resulted chemically modified
electrode can be optimized to some extent. Positively charged PVP-Os can
alternately assemble with negatively charged Au particles on Au surfaces. The
electrode containing Au particles showed two advantages over the PVP-Os/PSS
electrode: (i) faster electron transfer due to the high conductivity of Au
particles and; (ii) larger amount of the electroactive PVP-Os can be loaded due
to the rougher surface caused by Au nanoparticles. All these results
demonstrated that properties of the electroactive materials incorporated in
multilayer films depend largely on how they exist in the assemblies. By
alternately depositing the electroactive materials with conductive PAPSAH or Au
particles, the capability of the chemically modified electrode can be improved
greatly. This provides a way to optimize the way for the fabrication of
chemically modified electrodes.
In chapter 3, we have
developed a novel way to produce covalently attached multilayer films. We select
polycationic diazo-resins (DAR) and polyanionic PSS as the building blocks due
to the well-known photoreaction between diazonim and sulfonate groups. The
procedure for the fabrication of covalently attached multilayer film is simple
and demonstrated below: first, multilayer film of DAR/PSS was fabricated in a
layer-by-layer self-assembly fashion. Then the so-obtained film was exposed
under UV irradiation for a given time to induce the complete photoreaction
between DAR and PSS. In this way, covalently attached multilayer film can be
obtained. This technique makes full use of the simplicity of layer-by-layer
self-assembly technique and the photoreaction property of diaozonium connected
phenyl and sulfonate groups. The interaction in-between layers was converted
from ionic interaction to covalent bonds and the stability of the film could be
improved greatly. From the point of view to fabricate covalently attached
multilayer, this technique was mainly characterized by two advantages: it owes
all the advantages of ionic self-assembly technique such as simple in
operation, meanwhile, it allows to fabricate covalently attached films with
thickness adjusted in nanometer scale. Because DAR used is a kind of
photo-sensitive material, it is thus anticipated that this technique would
provide a way to fabricate stable, nanometer sized patterning surfaces. By
alternately depositing DAR with sulfonate-containing small organic dye
molecules, stable entrapment of small dye molecules in multilayer assemblies
can be realized. Due to the incompleteness of the photoreaction in the film, it
allows us to further adjust the structure of the covalently attached films. One
is to cover additional photoreactive layers of DAR/PSS upon DAR/dye assemblies,
which will improve the stability further. The other is to desorb the unreacted
dyes in covalently attached DAR/dyes assemblies by etching the assemblies in a
proper solvent. In this way, “man-made channels” can be made within the film,
which makes it have potential application in chemically modified electrodes. By
using layer-by-layer self-assembly technique, DAR can assemble successfully
with poly(acrylic acid) (PAA) to produce multilayer film. The driving force for
the film assembly is a combination of electrostatic interaction and hydrogen
bonds. When exposed under UV irradiation, diazonium and acrylate groups can
react with each other and the interaction within DAR/PAA multilayer assemblies
can be converted into covalent bonds. The stability of DAR/PAA assemblies can
be improved greatly. This further extends the application of this technique.
In chapter 4, we have developed an electric filed directed layer-by-layer assembly technique (EFDLA) which combines the layer-by-layer self-assembly technique and electrophoretic technique. By selecting polycationic PDDA and thiolglycolic acid covered negatively charged CdTe particles as model materials, we have demonstrated the success of this EFDLA technique in realizing selective deposition of PDDA/CdTe on ITO and Au surfaces. By selectively depositing CdTe particles with different size on different strips, we have fabricated two-pixel light emitting devices. When considering the wide range of materials which are suitable for layer-by-layer self-assembly technique and their stability under a given electric field, any charged species, including polyelectrolytes, orgnic small molecules, organic/inorganic particles, biological molecules, etc could realize the selective assembly by using this EFDLA technique.
EFDLA technique can realize not only the selective deposition
of charged materials, but also the successful deposition of materials with the
assistance of electric field which can not be deposited by the freely
layer-by-layer self-assembly technique.
