Preparation, Fluorescence Properties And Applications Of Some Thin Sensing Films Based Upon Supramolecular Interactions

Assembly of molecules on thin films to form highly ordered architectures is one of the important approaches to prepare functional films. This technology has been the focus of intense interest of many scientists due to their potential applications in creation of novel electronic, photo-electronic and sensing materials. Like the assembling of supramolecules, those molecules immobilized on the surface of a film can associate to form supramolecule too, and the structure would change along with the surround situation. Due to chemically bound to the substrate surface, the rotation and mobility of the molecules in immobilized state would be very different from those in free state. Modification of the surface of a filmwith right molecules may make it sens i t ive to some special analytes. Some novel device may be created as sensors or information storage materials. Such functional films are dependent upon a number of factors, including the nature of the molecules assembled, the nature of the substrate, and the nature of the linker etc. All the work included in this dissertation are based on the idea mentioned above.In the first section, Pyrene (Py) and (3 -cyclodextrin ( p-CD) were immobilized on the surface of chitosan (CS) film. Fluorescence studies revealed that the immobilized Py may be included in the cavity of its neighboring (3-CD. This structure makes the fluorescence emission of the cavity not be quenched by commonly used quenchers, including copper, cobalt and some other transition metal salts, KI and acrylamide. However, addition of nitromethane quenched the emission dramatically. Considering the high selectivity and sensitivity, great reversibility and stability, wide dynamic range, and long storage time, it was proposed that this novel films could be appl i cable to the sensing of ni trome thane in some energetic fuels.In the second section, a novel nitrite sensing film has been prepared by chemical immobilization of Py onto an aminiated quartz plate surface. Fluorescence excitation, emission measurements and fluorescence quenchingstudies demonstrated that the immobilized Py exists mainly in isolated state, rather than aggregated state. The profile and intensity of the emission of the plate are hardly affected by the presence of common chemicals including fluorescence quenchers likeTlNO.,, Cu(NO,)2, and CH3N02. Changing in pH values from 2 to 8 has little effect upon the emission. Introduction of a small amount of nitrite, however, quenches the fluorescence emission significantly. The quenching is very pH dependent and is totally reversible. This makes it a potential sensing materials for nitrite.In the third section, the device of an ultra-thin film fluorescence sensor with polyamino-chain naphthyl group modified onto a quartz plate surface has been prepared. It was found that in the fluorescence spectrum of device either in aqueous or in organic solvents there were both monomer and excimer emission peaks. The fluorescence quenching of the sensor by different metallic cations was studied in both aqueous and organic media. The studies reveal that the characters of the chain which bridge the surface and the function molecule may play a very important role in the aggregation of the terminated function molecule, and the conformation of the chain in solution is very different from that attached on the surface.