Study Of Functionalized Silsesquioxanes And Fluorescent Probe For Detection Of Al³⁺

In recent years, as an important materials to connect the organic polymers and inorganic materials, polyhedral oligomeric silsesquioxanes (POSS) have attracted a great deal of attention. As novel kinds of nano-particles, POSS exhibite a peculiar molecular structure. POSS is based on inorganic Si-O-Si frameworks and organo-functional groups are attached to the silicon atoms. This nanometer scale molecular hybrid structure endows POSS excellent performance. Consequently, POSS has important scientific significance and practical value.At present, environmental pollution has become a global hot topic. The qualitative identification and quantitative detection of toxic substances which existe in the environment are one of the important tasks for chemistry. Among the toxic substances, the metal cations are important pollutants because of their toxicity can lead to non-reversible damage to human and the earth’s river systems. On account of the reason, the study on environmental monitoring has attracted large attention. Therefore, a highly selective and sensitive chemosensor for the detection of metal cations is urgently needed. Fluorescent probes are excellent sensors for the detection of metal cations because of their good selectivity and high sensitivity. Rhodamine is a suitable fluorophore because of its excellent photophysical properties, such as long emission and absorption wavelengths, high fluorescence quantum yields and excellent photostability.In this study, phenylsilsesquioxanes and y-aminopropylsilsesquioxanes were synthesized by the acid-catalyzed hydrolytic condensation of phenyltriethoxysilane and y-aminopropyltriethoxysilane. The yields of the POSS product were about70%and25%, respectively. This synthetic method with the advantage of short reaction period was high yield, low cost and simple operation. Further studies of phenyl-POSS were carried out to obtain nitro-substituted and amino-substituted phenyl-POSS. The methods with high yields were low cost and easy to operate, and the reaction time was shortened to48hours.Based on the mechanism of trigger, we designed and synthesized a novel fluorescent sensor as a tool for the selective detection of aluminum ions. The molecule structure of probe was confirmed by NMR, FT-IR and MS. The qualitative identification and quantitative detection behavior were studied by UV absorption spectra and fluorescence emission spectra. The proposed response mechanism of the probe toward Al3+was also studied by NMR and theoretical calculation. The results indicate that the probe can recognized Al3+ions with highly selective and sensitive. Other than that, UV absorption intensity and the fluorescence intensity of the probe indicates a linear response with respect to A13+concentration.