The Surface Of Glass Fluorescent Molecules Immobilized, And Its Photophysical Behavior And Sensing Performance

Nitroaromatic compounds (NACs) are produced in large quantities for industrial uses in the preparation of dyes, drugs, perfumes, synthetic resins, pesticides, and so on. However, they are toxic and readily absorbed through the skin. Prolonged exposure in air containing NACs may cause serious damage to the central nervous system, impair vision, cause liver or kidney damage, anemia and lung irritation. Due to their wide use and great harm, leaching of NAcs could be an environmental disaster. A variety of methods such as gas chromatography (GC), liquid chromatography (LC), mass spectrometry (MS), electrochemistry and others have been developed for the analysis of NACs. However, complex sample handling, such as separation and concentration prior to analysis is needed, and furthermore, sometimes bulky and expensive instruments have to be used. Compared with others, fluorescent methods have gained lots of attention because of their great sensitivity, selectivity, multiple choices in signals or parameters, and low cost in instrumentation. As a film sensor, it could be re-usable and contamination free to the samples to be analyzed provided the film is properly fabricated.Among fluorescent film sensors, films with conjugated polymers as fluorescent active materials are very popular in the fluorescent sensing field because of their super-sensitivity. The exceptional sensitivity originates from the ability to create large signal amplification relative to small molecule chemosensors due to delocalization and rapid diffusion of excitons throughout the individual polymer chains, which is called "molecular wire effect" or "one point contact and multiple-point response effect". However, the limitations are also obvious. First of all, the sensors are commonly prepared by spin coating or dip coating one of the conjugated polymers on a solid substrate surface, physical combination in nature which is not, generally speaking, as strong as chemical combination. For this reason, leaching of the fluorescent compounds limits their uses in solution samples, because which may contaminate the systems to be analyzed via increasing the background fluorescence. Additionally, the thickness of the film is also an important factor that influences the sensing properties, which is attributed to steric hindrance to the permeation of the analytes within the films, and fluorescence self-quenching caused by energy migration among the conjugated polymer chains. So, the development of a new kind of fluorescent film sensor is of great importance.In the first part of our work, we decided to combine the advantages of monolayer films and conjugated polymers together in order to fabricate films with better sensing performances. A new fluorescent film was y fabricated through chemical assembly of oligo(diphenylsilane) on glass plate surfaces via a SAM's way. It was demonstrated that the fluorescence emission of the film is super-sensitive to the presence of NB in water phase, and the response is fast, reversible and almost interference free. The DL is 1.5×10-10 M, while other NACs and commonly found organic solvents show little effect upon the sensing process. Furthermore, the sensing process is reversible. All of these performances of the film ensure its potential uses in the simple and fast determination of trace amount of NB in aqueous phase.In the second part of this dissertation, another fluorescent film sensor has been developed via chemical immobilization of pyrene on glass plate. It was linked by 3-isocyanatopropyltriethoxysilane and 1,3-diaminopropane to the surface. Some of the films fabricated by our group before were sensitive to organic copper salts, which can be attributed to the "two-dimensional solution" model. So, we used a polar linker in order to fabricate a new kind of film sensor. We studied the contact angles, the excitation and emission spectrum of it, and also did some research on its solvent effects, sensing performances to Cu(Ac)2 in water and so on. Consequently, we have more deep knowledge on the structure of the molecules on the surface and photo physical chemistry behavior.