Fluorescent Mesoporous Organic-inorganic Hybrid Silicas:Preparation,CPL Behavior And Explosives Detection

Mesoporous organic-inorganic hybrid silicas(OIHSs)with the aggregation-induced emission(AIE)function were prepared by introducing AIE groups into the OIHSs.The materials exhibit significant advantages in strong fluorescence,adjustable mesoscopic structure,high stability,excellent biocompatibility and easy functionalization.These OIHSs can be used in the biology,chemical sensing and circularly polarized luminescence(CPL)fields.Herein,fluorescent OIHSs were prepared through supramolecular templating approaches,and their applications in explosive detection and CPL were investigated.The study on helical luminescence nanomaterials is a frontier subject.Firstly,it was found that the mesoporous OIHSs with tetraphenylene(TPE)groups could be used as chemical sensors for explosive detection.Helical mesoporous OIHS nanofibers were synthesized by the polycondensation of TPE-containing triethoxysilane and 1,2-bis(triethoxysilyl)ethane in the presence of cetyltrimethylammonium bromide.The blue fluorescence was identified.These hybrid silicas exhibit sensitive fluorescence quenching response towards the nitroaromatic explosive,picric acid(PA).This is ascribed to the photoinduced energy transfer quenching process and the ordered mesoporous structure which helps guest molecules to enter the pores quickly.Secondly,the OIHSs with regular pore wall structures were prepared and their performance for explosives detection was investigated.Mesoporous OIHSs with blue fluorescence were prepared using an organosiloxane derived from tolane in the presence of a block copolymer,Brij56,under an acidic condition.The addition of xylene in the reaction mixtures facilitates the regular arrangement of the tolane group.The regular arrangement of organic functional groups hopefully improves the materials’ thermal stability.The hybrid material exhibits sensitive fluorescence quenching response to PA as a fluorescent sensor.Finally,the relationship between their CPL chirality and the stacking chirality of tolane groups was established based on the twisted tubular nanoribbons of tolane bridged OIHSs.The nanoribbons were prepared using the self-assemblies of chiral cationic lowmolecular-weight gelators as templates under different concentrations of ammonia and volume ratio of n-propanol/water.The OIHSs emit blue light under UV irradiation.The circular dichroism and CPL spectra revealed that the chirality was transferred successfully from the templates to the hybrid materials.The CPL handedness was mainly dominated by the stacking chirality of the tolane groups.