Preparation,Characterization And Application Of Organic Modified Chitosan/Rare Earth Multifunctional Materials

The 4f electron configuration of rare earth elements is very special.Therefore,its luminescent properties are also very excellent,which broadens the practical application of rare earth complexes.Rare earth hybrid materials are usually prepared by introducing rare earth complexes into some matrices.The material has the characteristics of a large Stokes shift,sharp fluorescence characteristic peak,high color purity,and adjustable luminescent color.Therefore,it has excellent luminescence properties and is widely used in the field of fluorescence sensors.On the other hand,chitosan is a kind of biological macromolecule with extremely wide sources.It has good plasticity and biocompatibility and is easy to be degraded.It is a material that does not pollute the environment.However,the poor solubility of chitosan in neutral aqueous solution and many organic solvents limits its potential applications.Therefore,this paper uses organically modified chitosan as raw material,which is easier to dissolve in water than chitosan and easier to form complexes with rare earth elements.In addition,the current research shows that the biocompatibility and mechanical properties of rare earth hybrid materials,such as brittleness,are poor.In order to meet the application of rare earth luminescent materials with toughness and stretchability as the main conditions,such as tissue engineering and soft devices,luminescent hydrogels with excellent mechanical properties are urgently needed.Therefore,in this paper,six hydrogel materials with excellent luminescent properties and excellent mechanical properties were prepared by a simple and environmentally friendly method,and these materials were characterized and analyzed in detail.This paper contains the energy spectrum,scanning electron microscopy,mechanical properties test,thermogravimetric analysis and fluorescence,thermogravimetric analysis,and fluorescence spectroscopy.The results showed that the rare earth complexes were evenly distributed in the luminescent hydrogel,and the prepared luminescent hydrogel had excellent mechanical properties,good thermal stability,and excellent luminescent properties.In view of the excellent luminescent properties of hydrogel materials,we used it as a sensor for the detection and recognition of organic reagents and antibiotics,etc.,indicating that when the luminescent hydrogel material is used as a sensor,the detection limit is low,and the sensitivity is high.The research in this paper is mainly divided into the following parts:（1）Preparation and application of microfibrillated cellulose/organic modified chitosan/rare earth luminescent hydrogel materials（MFC-PC-Eu-TTA/MFC-PC-Tb）.There are two steps to preparing luminescent hydrogels.Firstly,epichlorohydrin was selected as the crosslinking agent in the experiment,and the organically modified chitosan and microfibrillated cellulose were crosslinked to form a three-dimensional network hydrogel by cross-linking.Then,the rare earth ions(Eu³⁺or Tb³⁺)are coordinated with the carboxyl functional groups on the pyridine ring of the organic modified chitosan so that the rare earth ions are connected with the relevant functional groups in the three-dimensional network of the hydrogel material in a coordination bond manner,thereby obtaining a rare earth complex covalently doped hydrogel luminescent material.The luminescent hydrogel material has excellent properties.When used for the detection of common organic reagents,it was found that the material can be used to detect organic aldehydes（formaldehyde,benzaldehyde,and glutaraldehyde）and styrene reagents and has strong selectivity,high sensitivity,recyclability,and anti-interference.（2）Preparation and application of gelatin/polyacrylamide/organic modified chitosan/rare earth luminescent hydrogel materials（Gelatin-PAAm-PC-Eu-TTA/Gelatin-PAAm-PC-Tb）.Firstly,acrylamide formed a polyacrylamide polymer chain by free radical polymerization,and the formed polyacrylamide and organically modified chitosan chain formed a network structure by physical crosslinking.Secondly,gelatin was used as raw material in the experiment,and the gelatin network structure was made by dissolution-cooling.Finally,a double network hydrogel was prepared by physical entanglement between the polyacrylamide-organic modified chitosan and gelatin networks.Rare earth europium ions(Eu³⁺)or terbium ions(Tb³⁺)form coordination with carboxyl functional groups of organically modified chitosan so that rare earth ions are connected to the three-dimensional hydrogel network in the form of coordination bonds to obtain rare earth complexes covalently doped hydrogel luminescent materials.The luminescent hydrogel material has excellent properties.When used as a sensor for the detection of commonly used antibiotics,it was found that it could be used to detect tetracycline and oxytetracycline.In addition,the material can also detect commonly used organic reagents,such as aniline.When testing organic reagents and antibiotics,it was found that the hydrogel material had strong selectivity and anti-interference.（3）Preparation and application of polyvinyl alcohol/organically modified chitosan/rare earth luminescent hydrogel materials（PVA-PC-Eu-TTA/PVA-PC-Tb）.This paper obtained a polyvinyl alcohol-organic modified chitosan network structure by chemical crosslinking polyvinyl alcohol and organically modified chitosan with epichlorohydrin as the chemical crosslinking agent.Then,rare earth europium ions(Eu³⁺)or terbium ions(Tb³⁺)were used to coordinate with the carboxyl functional groups of organically modified chitosan so that rare earth ions were linked to the hydrogel network in the form of coordination bonds to obtain rare earth complex covalently doped hydrogel materials.The luminescent hydrogel material has excellent properties and can be used to detect nitrofuran antibiotics.In addition,the material can be used in common organic tests sensors,such as detecting aromatic organic reagents,acetylacetone,and trifluoro acetylacetone.When examining organic reagents and antibiotics,it was found that the hydrogel material had strong selectivity and anti-interference.