Preparation,Properties And Application Of Aggregation-Induced Emission Functionalized Hydrogels

As a dynamic system of porous polymers with high water content and easy functionalization,hydrogels have mechanical properties that can be matched with living tissues,excellent permeability,and good biocompatibility,showing extraordinary r esearch value and unique application prospects.Many hydr ogel materials not only have high optical transparency,but also their multi-phase,porous organic network structure is easy to integrate with luminescent functional units,which has become an i mportant class of optically desirable main materials in recent years,and thus a rich variety of luminescent functional hydrogels and their application technologies have been developed.On the other hand,aggregation-induced emission(AIE)is a novel,characteristic and special response fluorescence,which is gradually becoming one of the important frontiers in the design and development of new concept materials for light functionalization.AIE functional molecules do not fluoresce when dispersed,while their luminescence is greatly enhanced when aggregated,which overcomes the co ncentration quenching of traditional dyes and becomes one of the important strat egies for the development of efficient solid-state light-emitting devices and application technologies.In particular,AIE luminescence is highly sensitive to changes in the physical state of functional molecules,and the process is r eversible,which itself is a highly characteristic built-in intelligent response sensing mechanism.Based on the above statement,we believe that the introduction of aggreg ation-induced emission into hydrogel systems has the potential to expand the aggr egated fluorescence function of hydrogel systems with rich and adjustable colors and relatively high luminescence intensity.As a built-in fluorescence sensor,it can be used to visualize the dynamic changes and regulatory processes of hydrogels and promote the scientific understanding and application development of complex hydr ogels.Therefore,this thesis starts from the tetrazolium-modified AIE molecular system and its application technology developed by our group,combines the aggregation-induced emission functional unit with the transparent hydrogel,constructs the aggregation-induced emission functionalized hydrogel system,develops in situ visualization analysis and characterization means for the dynam ic change process of h ydrogel by using the AIE response fluorescence property.And we will also explores the in situ metal ion detection of fluorescent hydrogel,design and preparation of fluorescence-enhanced photonic crystal hydrogels,strengthening mechanism of hydrogel by Hofmeister effect.The main contents are as follows.(1)To address the needs of in situ detection of heavy metal pollution in groundwater,we designed and prepared hydrogel sensing films with fluorescent“turn-on” response of mercury ions using aggregation-induced fluorescent molecule TPE-4TA for functionalized doping of polyvinyl alcohol(PVA)hydrogels,and achieved selective and sensitive in situ quantitative detection of mercury ions in solution samples.Firstly,a mercury ion probe system based on mercury ion-tetrazolium ligand triggered aggregation-induced emission response was developed,and characterized and evaluated for responsiveness,selectivity,sensitivity and interference i mmunity in the solution state.Secondly,due to the alcohol solubility of the probe,it does not emit when doped in the hydrogel material,and we optimized the formulation and preparation scheme of the probe-PVA hydrogel-sensitive film.Finally,in situ detection of mercury ions in water samples was achieved using the hydrogel sensing film,which lowered the limit of detection for mercury ions(2 ppb,3 m L).The considerations and solution strategies for achieving aggregation-induced emission detection in multiphase hydrogel networks are also discussed i n the study,which is expected to promote the further development of portable AIE fluorescent hydrogel sensing films and their application conversion.(2)Aggregation-induced emission functionalized gelatin hydrogels were designed and prepared;further,the aggregation-induced emission functional unit was used as a built-in sensor in the hydrogel to establish a fluorescen t visualization analysis method for the dynamic changes of the hydrogel,and the mechanism of the Hofmeister effect during the salting-in and salting-out treatment of gelatin h ydrogels was explored.Gelatin hydrogel is a very important biomedical material,and its m echanical properties are highly correlated with the practical application effects.We developed a class of AIE dyes that specifically “turn-on” labeled gelatin,and used these AIE dye-protein complexes as pregel to construct aggregation-induced emission functionalized protein hydrogel systems.We found that AIE dyes act as a responsive built-in fluorescence sensor whose fluorescence intensity dynamics can,to some extent,reflect gel network dynamics in situ and in real time.We used this AIE fluore scent visualization strategy,together with other hydrogel characterization analyses,to investigate the dynamic processes of protein hydrogels after different salting agent treatments and their resulting Hofmeister effect,thus establishing a fluorescence analysis method to study the dynamic changes of hydrogels and providing a traceable technical guidance strategy for the implementation of schemes using salt treatments to strengthen hydrogel networks.We propose a mechanism by which different salt treatments modulate the internal morphology of hydrogels presenting AIE fluore scence differences,which can be used to achieve fluorescen t visualization of the Hofmeister effect in hydrogels.These studies demonstrate the potential of response fluorescence with AIE in studying the dynamic transformation process of hydrogel networks.(3)Aggregation-induced emission fluorescent protein hydrogels with photonic crystal complex structures were constructed using AIE dye-BSA protein complexes filled into inverse-opal Gel MA structures.The fluorescence properties of AIE flu orescent hydrogels regulated by the photonic crystal structure in different templates were characterized,and the enhancement effect of the aggreg ation-induced emission of the hydrogel by using the photonic crystal structure was preliminarily discussed.The photonic crystal templates were made by vertical deposition of silica micr ospheres prepared by the St(?)ber method,which showed bright structural colors;several AIE dyes that could be “turn-on” by BSA;the templates were filled into the AIE-BSA hydrogels after replacemet by Gel MA.It was found that the o rdered microstructure of photonic crystal has a significant enhancement effect on fluorescence,and the gain effect of fluorescence emission wavelength is best near the photonic forbi dden band,and there is a difference in the fluorescence lifetime from the same fluorescent h ydrogel tested in different photonic microstructures.We expect that the AIE fluore scent hydrogel material with photonic crystal structure can realize multimodal sensing for hydrogel material deformation process by using the synergistic modulation of structural color-AIE fluorescence,which is expected to eventually contribute to bi ological tissue mechanics analysis and tissue engineering application r esearch.