Fluorescence Emission Of Film Research Articles

Cholesterol modified OPE functionalized film: fabrication, fluorescence behavior and sensing performance

A novel oligo(p-phenyleneethynylene) with cholesterol on its side chains (CHOL-OPE) was designed and synthesized. Film 1 and Film 2 were fabricated by immobilizing, separately, the oligomer as prepared and its control, OPE, which contains no side chains, on glass plate surfaces via utilization of a self-assembled monolayer (SAMs) technique. Fluorescence studies revealed that the profile of the fluorescence emission spectrum of Film 1 is dependent upon the composition of a mixture of THF and water. In contrast, Film 2 shows no such effect. Sensing performance studies demonstrated that the fluorescence of Film 1 is super-sensitive to the presence of 2,4,6-trinitrophenol (picric acid, PA), and sensitive to 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT) and nitrobenzene (NB) in the aqueous phase, whereas the nitroaromatics (NACs) as studied show little effect on the fluorescence emission of Film 2. The results from fluorescence quenching studies and the fact that copper salts (copper nitrate and copper acetate) show no detectible effect on the fluorescence emission of Film 1 show that the oligomer and the short linker, connecting the oligomer and the substrate, of the CHOL-OPE functionalized film may adopt a compact structure. Interestingly, the sensing process is fully reversible and free of interference from commonly found compounds, including methanol, THF, toluene, dichloromethane, ammonia, HCl, NaOH, NaCl, copper salts and seawater, etc. Fluorescence lifetime measurements revealed the static nature of the quenching process. The superior sensing performance of Film 1 for the analytes in the aqueous phase guarantees that the film may have the potential to be developed into a sensor device for the detection of PA and other NACs in groundwater.

A novel picric acid film sensor via combination of the surface enrichment effect of chitosan films and the aggregation-induced emission effect of siloles

A novel fluorescent film was fabricated by doping the aggregates of hexaphenylsilole (HPS) into a chitosan film. It was demonstrated that the fluorescence emission of the film is stable, sensitive and highly selective to the presence of picric acid (PA). The detection limit for PA is about 2.1 × 10−8 mol/L. Introduction of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), nitrobenzene (NB), phenol, benzene, toluene, methanol, ethanol, and zinc nitrate (Zn(NO3)2) had little effect upon the fluorescence emission of the film. The selectivity of the film was attributed to the specific electrostatic association effect of the protonated substrate film to picrate anion and the screening effect of the film to the interferents. The network structure of the substrate film is also favourable for the stabilization of the fluorescence emission of the hybrid film, by preventing the further aggregation of silole aggregates. Fluorescence lifetime measurements revealed that the quenching is static in nature. Furthermore, the quenching process is fully reversible. Considering the simplicity of the preparation and the outstanding performance of the hybrid film, it is anticipated that it could be developed into a real-life PA sensor.