The Fabrication Of Tough Smart Fluorescent Hydrogels And Their Application In Information Encryption And Zinc Ion Detection

Smart fluorescent hydrogels have a wide range of applications in smart switch information recording,flexible wearable devices,display and storage and sensors because of their good flexibility,biocompatibility,controllability and stimulus responsiveness.However,conventional smart fluorescent hydrogels generally suffer from weak mechanical strength,short service life and unstable properties.Therefore,it is an interesting task to develop tough smart fluorescent hydrogels.The introduction of sacrificable bonds in hydrogel networks is the main method for constructing tough hydrogels.In this work,smart fluorescent hydrogels with high strength,excellent luminescence properties and multiple stimulus responsiveness were prepared through the introduction of physical cross-linked networks,and their applications in multidimensional information encryption,storage and zinc ion detection were explored.This thesis includes the following three parts of work:1.N-Acrylglycinamide（NAGA）and 6-acrylamidopyridine（6APA）were used to fabricate dual physical cross-linked hydrogels with multiple hydrogen bonds and lanthanide metal coordination bonds by one-pot free radical polymerization and ion immersion.The synergistic effect of hydrogen bonding and lanthanide metal coordination bonding gives these hydrogels excellent mechanical properties,with tensile stress up to3.9 MPa,Young’s modulus 0.7 MPa and elongation at break up to 1500%.The lanthanide metal coordination bond not only confers excellent fluorescence properties to these hydrogels,but also allows the fluorescence colour of the hydrogels to be adjusted by changing the ratio of the two lanthanide metal ions.Due to the dynamic of the metal coordination bond,the fluorescent hydrogels exhibit a fluorescence response to acid/base without luminance fatigueat least five cycles,and time-dependent luminescence fading process of different lanthanide complexes.Thus,using the different fluorescence colours and the time difference in the fluorescence decay process,these fluorescent hydrogels can be used for maskless writing and multidimensional information storage,encryption and decryption.2.The organoluminescent groups 4’-（allyl-4-pyridyl）-2,2’:6’,2"-trypyridine perchlorate（PPTP）and NAGA were used to obtain as-prepared fluorescent hydrogel by one-pot free radical polymerisation,followed by immersing in ionic solution.A variety of transition metal ions were introduced by ionic immersion to obtain high-intensity intelligent fluorescent hydrogels with multiple hydrogen bonds and metal coordination bonds.In this system,by adjusting the strength of the coordination bonds between the transition metal ions and the terpyridyl,the rate of conversion of the chromogenic group monomers into dimers is then regulated,achieving the temporal regulation of the hydrogel fluorescent colour conversion（from blue to white to yellow to green）.The fluorescent hydrogel has a potential application in multi-layer information storage,multi-dimensional information encryption and decryption by 3D images and 2D codes.3.Fluorescent hydrogels with multiple hydrogen bonds and metal coordination bonds were obtained by one-pot free radical polymerisation of N-acrylglycinamide（NAGA）and methacrylic acid,followed by the introduction of Eu³⁺and terpyridine（TPy）by ionic solution immersion.The synergistic effect of metal-ligand bonding and multiple hydrogen bonds gives these hydrogels excellent mechanical properties,with fracture stresses and elongation at break up to 2.5 MPa and 1700%,respectively.At the same time,the"antenna effect"between TPy-Eu³⁺not only gives these hydrogels excellent fluorescence properties,but the dynamic reversibility of the metal coordination bonds also gives them a Zn²⁺-specific response.The P（NAGA-co-MAAc）/Eu/TPy（10）hydrogels exhibit fast fluorescence response（45 s）,high quenching constant(K_sv=3.26x 10³M^-1)values,low LOD for Zn²⁺（1.6μM）and excellent resistance to anionic and cationic interference.In addition,the characteristic red-violet fluorescence shift of the hydrogel can be observed by the naked-eye,enabling semi-quantitative naked eye detection of Zn²⁺.Furthermore,based on the relationship between R/G and Zn²⁺concentration relationship,this hydrogel can be used as a potential on-site kit for the quantitative detection of Zn²⁺in the aqueous environment in our daily life.