Gelation And Structure Dependent Colorimetic Fluoride Anion Sensing Behavior Of Hydrazide Derivatives

The low molecule organogel(LMOG) is one type of soft matter with aggregation of gelator and solvent, which is based on the three–dimensional network formed by weak non-covalent bond, such as hydrogen bonding, π-π interaction and van der Waals force. The LMOG is thermally reversible and very sensitive to the external change. Hence by altering the preparation condition such as mix related matter in, change the solvent or the cooling mode, the gel properties could be transformed. Furthermore, the highly modificability of gelator make the sensing of external changes of stimulation happen. By altering the functional group, the LMOG could transform to small molecule intelligent responsing organogel which could response to various of Physical and chemical stimuli, such as light, molecule, ion, ultrasound, electromagnetic field, mechanical force and p H etc., hence this kind of material have been paid a lot of attention. Considering the relevant literatures and the former research in our group, the present thesis research the properties of a geltor, aimed at explore the influence of ultrasound on the aggregation structure, the driving force of self-assembly and the mechanical properties of organogel. Besides we mainly focus on the relationship of the structure of the hydrazide derivatives with its colorimetric anion sensing abilities by contrast three hydrazide derivatives` sensing behaviors.1. We observed the gel of R8-NO2 in ethanol with different density by fluorescence reflection microscopy,transmission electron microscope and scanning electron microscope, detected the structure of aggregations with the XRD and FT-IR test,by analysis these results a conclusion was drawn, that there exist one kind of spheroidal aggregate and two types of fiber, one of them is formed by spheroidal aggregate and the other is formed by gelator derectly. And the gel grown in-5℃ was studied by the SEM、XRD、FT-IR and rheological test, by comparing with the test outcome of the gel grown in room temperature, we found that higher condensate depression can increase the quantities of the fibers and gathered spheroidal aggregation, but the mechanical property and intermolecular forces doesn’t change. Such result could prove the correctness of the theory which is about the forming process of gel of R8-NO2 in Et OH. We also study the influence of ultrasound on the property of the gel of R8-NO2 in Et OH. By the SEM and rheology test, we found the morphology were changed and the mechanical properties of the gel were significantly raised. The XRD result was similar with test result of the solution. We draw a conversion as follows: the ultrasound augment the opportunity of spheroidal aggregations, and consequently promote the forming of fiber.2. We have studied the anion response behavior of N6, B6 and M6 the three hydrazide derivatives with different terminal substituents in DMSO solution. As a consequence, the compound B6 with phenyl groups and M6 with methyl groups can allow highly selective and rapid colorimetic fluoride detection, whereas the compound N6 with terminal nitro substituent can respond to F-, Ac O- and H2PO4-. This is due to the nature of the terminal substitute that has a profound influence on the acidity of these symmetric dihydrazide derivatives. The UV-vis spectroscopy and 1H NMR titration experiments proved that the series of hydrazide derivatives response to fluoride ion in same mechanism with the reported C8, i.e. the interaction of F- with NH deprotonate the sensor molecule, result in the intermolecular charge transfer effect occurred, the electron distribution under gone a realignment, and as a consequences the color of solution or gel has change.3. Two hydrazide based small molecule intelligent responsing organogel, TC6 and C10, with different number of hydrazide groups were synthesized and their anion responsive behaviours were studied. The milk-white gel of TC6 in 1,2-dichloroethane collapse to bright yellow solution when F- were added, and the fluorescence emission spectrum test shown that the aggregation induced enhanced emission of the gel was reduced since the fluoride anion response occurred. And the Ac O- can’t destroy the gel completely. Besides the solution of C10 in DMSO can realize highly selective and rapid colorimetic fluoride detection. The UV-vis spectroscopy and 1H NMR titration experiments indicated that TC6 and C10 share the same anion sensing mechanism with other compounds introduced above. According to these results we can draw a conclusion that less hydrazide derivative means better fluoride anion sensing ability. The results might offer guidance and provide the basis for designing colorimetric anion sensors with excellent selectivity.