Fluorescence Behavior of Aromatic Compounds Immobilized on A Substrate Surface：A Monte Carlo Simulation

Recently，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. It is found that the properties and performances of the films depend upon various factors，including the nature of the sensing element，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 the theoretical simulation of the sensing films based upon the proposed principle. 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 the short stiff spacer. It is 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%.