【作者】 王渭娜；

【导师】 房喻；

【作者基本信息】 陕西师范大学 ， 有机化学， 2003， 硕士

【摘要】 将具有特定性能的小分子组装于基片表面形成高度有序的结构，是制备功能薄膜材料的一种重要方法。这类薄膜材料的性质主要取决于三个因素：定向组装功能分子的特性，基质的特性以及连接功能分子与基质的分子链的特性。因此，通过改变基质的类型，优选功能分子的结构，调节连接臂的长度、柔性及其化学特性就有可能得到多种多样性能优良的功能薄膜材料。多环芳烃特有的疏水性和稠环平面结构决定了其在极性介质中易于形成激基缔合物(Excimers)，从而在表现出单体(Monomers)荧光发射特性的同时，也表现出激基缔合物荧光发射特性。激基缔合物荧光发射强度与单体荧光发射强度之比反映了体系中多环芳烃分子的簇集程度。通过设计实验，将多环芳烃共价组装于柔性高分子膜或刚性石英玻璃等基质表面，利用膜固定化多环芳烃的超分子行为及其对环境条件变化的依赖性，研究多环芳烃在体系中的荧光行为(主要是激基缔合物荧光与单体荧光强度之比，I_E／I_M)，可得到一系列荧光传感薄膜材料。显而易见，这类薄膜的传感特性主要表现为I_E与I_M的比值，而许多因素都会影响这一比值。例如：连接臂的长度、柔性，基片表面传感元素固定化密度，传感元素(多环芳烃)相互缔合形成激基缔合物的趋势大小(用参数P表示，P值应该介于0到1之间)，传感元素的激发百分率(光吸收效率)，传感元素量子产率和基片在溶剂中的溶涨性等。同时，还要考虑到只有当I_E与I_M之比在一个合适的范围时(通常介于0.5到2之间)，薄膜的传感性能才能最大程度地表现出来。所有这些因素都是这类传感薄膜材料在设计中需要考虑的问题，完全依赖实验搞清这些问题是不现实的。因此，通过理论模拟深入了解影响传感薄膜荧光行为的基本要素和影响规律对于指导新型传感薄膜材料设计具有重要的意义。 正是基于以上思想，本文采用Monte Carlo方法模拟研究了表面单层组装多环芳烃的荧光行为。 本论文首先就Monte Carlo模拟方法的由来、发展历史、求解问题的一般规则做了介绍，并把Monte Carlo方法和其他的分子模拟方法的作了比较，又对Monte Carlo模拟方法在高分子科学中的应用作了综合性的论述。 本论文的第一部分工作是对多环芳烃(传感元素)经由一刚性短臂单层组装在惰性基质表面的荧光行为进行了Monte Carlo模拟。考察了基片表面传感元素固定化百分率、传感元素激发百分率(光吸收效率)以及传感元素分子在介质中相互缔合形成激基缔合物趋势大小(用P表示，P值介于0到1之间)等因素对传感元素激基缔合物荧光发射强度与单体荧光发射强度之比(I_E／I_M)所产生的影响。研究结果表明，具有中等光吸收效率的多环芳烃适宜于作为传感元素，中等固定化密度的基片可能具有比较理想的传感性能。 本论文的第二部分工作是用 Monte Carlo方法模拟了惰性基片表面单层组装多环芳烃（传感元素）的荧光行为。考察了在不同长度的柔性连接臂情况下，基片表面传感元素固定化百分率、传感元素激发百分率（光吸收效率）以及传感元素分子在介质中相互缔合形成激基缔合物趋势大小（用P表示I值介于0到1之间）等因素对传感元素激基缔合物荧光发射强度与单体荧光发射强度之比（IE／IM）所产生的影响。结果表明，传感元素特性参数P的大小对薄膜传感特性影响相对较小。在不考虑量子产率的前提下，就惰性基片而言，要将IEha控制在0．5－2之间，连接臂的长度至少可在3到12之间调节，传感元素固定化百分率可控制在30％到70％之间。此外，传感元素的激发百分率也对薄膜的IE／IM产生显著影响。一般而言，低的激发百分率对应于较高的 IE／IM比值，但过低的激发百分率也伴随着弱的荧光发射。因此，要使传感薄膜发挥最好的传感特性，激发百分率也不可以太小。更多还原

【Abstract】 Assembly of molecules on thin films to form highly ordered architectures is one of the important approaches to prepare functional films. In addition to other advantages, molecules in assembled state are much easier to be made into devices. Thus, a series of sensing films based upon the supra-molecular behavior of aromatic compounds immobilized on substrate surfaces and its dependence to the composition of the medium have been successfully prepared recently. It was found that the properties and performances of the films depend upon various factors, including the nature of the sensing element (the molecule assembled), the way of immobilization, the nature of the substrate, and the density of the sensing element immobilized etc. To accelerate and deepen the studies, it was decided to carry out theoretical simulation of the sensing films based upon the proposed principle. All the work included in this dissertation is based upon the idea mentioned above.In the first section, the fluorescence behavior of a functional plate, of which the surface is functionalized by single layer immobilization of aromatic compounds (sensing elements), is simulated by Monte Carlo simulation method. The effects of the immobilization density of a sensing element, the excitation efficiency, and the association efficiency, P, which is a characteristic parameter of an aromatic compound, between the molecules of the sensing element on the ratio of the excimer emission to the monomer emission of the plate have been systematically examined. But the effects of the length and flexibility of a spacer are neglected, because in this simulation aromatic compounds are immobilized on a plate by short stiff spacer. It was demonstrated that, for a functionalized plate of a short stiff spacer in a polar solvent (in this case, the association tendency is strong, and P is close to 1), aromatic compounds of middle excitation efficiency might be suitable as sensing elements. In addition, the immobilization density of the sensing element should be controlled. A recommended value is about 50%.In the second section, the fluorescence behavior of a function plate, of which thesurface is functionalized by single layer immobilization of aromatic compounds (sensing elements), is simulated by Monte Carlo simulation method. The effects of the immobilization density of a sensing element, the excitation efficiency, and the association efficiency, P, which is a characteristic parameter of an aromatic compound, between the molecules of the sensing element on the ratio of the excimer emission to the monomer emission of the plate have been systematically examined. Different to the first section, the effects of the length and flexibility of a spacer are considered, because in this simulation aromatic compounds are immobilized on a plate by a flexible spacer and the length of the spacer are adjustable. It was demonstrated that the characteristic parameter P of a given sensing element has limited effect upon the film’s IE/IM ratios, for a sensing film of spacer length of 3-12, a IE/IM value between 0.5-2 may be obtained only when the density of the sensing element immobilized on the inert substrate is controlled between 30-70%. It is to be noted that lower photon excitation efficiency corresponds to a greater IE/IM values. But, too low excitation efficiency means weaker fluorescence, resulting in difficult in measurement, thereby, excitation efficiency should not be too low.更多还原