Preparation Of Rare Earth-polymer Hydrogels And Application Of Fluorescent Probes

Lanthanide luminescent materials have been widely used in optoelectronic devices,solar cells,biology and medicine due to their unique light-emitting characteristics,such as good light stability,large stokes shift and long light-emitting life.However,lanthanide metal ions generally do not luminescence or luminescence very weakly,so it is difficult to form luminescent materials singly.In order to enhance the luminescent properties of lanthanide ions,lanthanide ions are often introduced into other materials to prepare composite materials,such as nanocomposite luminescent materials,Si O₂aerogel composites,organic silicon hybrid materials and organic-inorganic hybrid materials.Recently,hydrogels have concerned because of their biocompatibility and flexible processing properties.In particular,luminescent hydrogels have shown great vitality in fluorescence sensing,imaging,information encryption and other fields due to their versatility and unique optical properties.Luminescent hydrogels are formed by doping lanthanide metal ions into the hydrogels,and the application value of the hydrogels is further expanded.In this paper,biodegradable and non-toxic biomacromolecules such as sodium alginate,gelatin and agar were introduced to prepare a variety of flexible and elastic luminescent hydrogels via a simple free radical polymerization method,and a series of characterizations（such as stress strain,SEM,TG and fluorescence analysis）were carried out.Based on the good luminescent property of the material,the fluorescent probe can be used as a fluorescent probe for toxic metal cations(such as Fe³⁺,Cu²⁺,Ag⁺and Pr³⁺),anions(such as Cr₂O₇^2-and F^-)and organic micromolecules（such as pyridine and dimethyl sulfoxide）.At the same time,aspartic acid（Asp）,glutathione（GSH）,ofloxacin（OFLX）,diclofenac sodium（DS）and salicylic acid can be detected in real time.The main sections of the paper are as follows:（1）Preparation,characterization and application of PAAm/SA(Eu³⁺-OFLX/Tb³⁺-DPA)/(Tb³⁺-Eu³⁺)-DPA hydrogels.The luminescent hydrogel is mainly formed by the free radical polymerization of acrylamide,the strong hydrogen bond interaction between acrylamide and sodium alginate and the entanglement between chains.The sodium alginate provides a COO^-group coordinated with lanthanide ions Tb³⁺or Eu³⁺,and then the strong luminescence behavior of the hydrogel is realized under the action of the antenna effect of the corresponding ligand.PAAm/SA/Eu³⁺/OFLX hydrogel is an acid-base sensitive luminescent material,which can respond to different p H value.So it can realize the encryption and decryption process of information in the presence of hydrochloric acid solution with p H=3 and triethylamine solution with p H=8.In addition,since an aqueous solution of L-aspartic acid among amino acids shows strong acidity,the luminescent hydrogel can be an ideal choice for detecting L-aspartic acid.The PAAm/SA/Tb³⁺/DPA luminescent hydrogel is a fluorescent probe with high sensitivity and high selectivity for Ag⁺,so the PAAm/SA/Tb³⁺/DPA luminescent hydrogel can be used for the detection and identification of Ag⁺.The PAAm/SA/(Tb³⁺-Eu³⁺)/DPA luminescent hydrogel formed with the volume ratio of Tb³⁺and Eu³⁺solution of 1:1 has good sensitivity to pyridine in organic small molecules,so the luminescent hydrogel can be used as a fluorescence probe of pyridine.（2）Preparation,characterization and application of PAAm/Gelatin/SA(Eu³⁺-TTA)/(Tb³⁺-Aba)hydrogels.The luminescent hydrogel is mainly formed by the free radical polymerization of acrylamide,the strong hydrogen bond interaction among acrylamide,gelatin and sodium alginate and the entanglement between chains.The addition of sodium alginate is mainly to provide COO^-groups coordinated with Tb³⁺or Eu³⁺and the addition of gelatin further enhances the toughness and rigidity of the hydrogel.PAAm/Gelatin/SA/Eu³⁺/TTA luminescent hydrogel is sensitive to Cu²⁺,and can realize real-time detection of Cu²⁺through fluorescence quenching.The fluorescence of the hydrogel quenched by Cu²⁺can be recovered after soaking in the aqueous solution of GSH.Therefore,it can also be used as a fluorescent probe of GSH,which is a good method to distinguish the same type of amino acids.The PAAm/Gelatin/SA/Tb³⁺/Aba luminescent hydrogel has the advantages of fast response and high sensitivity to Cr₂O₇^2-,and can be used as a fluorescent probe of Cr₂O₇^2-to realize the efficient recognition of Cr₂O₇^2-.（3）Preparation,characterization and application of PAAm/Agar/SA/Tb³⁺/Aba hydrogel.The luminescent hydrogel is mainly prepared by free radical polymerization of acrylamide,strong hydrogen bond and entanglement among chains interaction among acrylamide,agar and sodium alginate.The addition of sodium alginate provides a coordination environment for lanthanide ions,and the incorporation of agar greatly enhances the toughness and rigidity of the hydrogel and improves the mechanical property of the hydrogel.PAAm/Agar/SA/Tb³⁺/Aba luminescent hydrogel is sensitive to Pr³⁺and diclofenac sodium（DS）,and can detect and recognize Pr³⁺and DS through fluorescence quenching.Salicylic acid can provide rare earth Tb³⁺coordination sites and sensitize Tb³⁺because of its carboxyl and hydroxyl groups in its structure.Therefore,PAAm/Agar/SA/Tb³⁺hydrogel can be used as a fluorescent probe of salicylic acid,which is an effective method to distinguish salicylic acid and its analogues.（4）Preparation,characterization and application of PAAm/PAMPS/Eu³⁺@Lap/TTA nanoluminescent dual network hydrogel.The hydrogel is formed by free radical copolymerization of polyacrylamide and poly（2-acrylamide-2-methylpropanesulfonic acid）sodium.The introduction of rare earth Eu³⁺ions successfully exchanged Na⁺on the nano clay and the photoluminescence behavior of the hydrogel can be realized without the introduction of coordination groups.The light-emitting hydrogel is sensitive to acid and base,and can achieve the on-off behavior of hydrogel fluorescence in the atmosphere of formic acid and triethylamine.In addition,the PAAm/PAMPS/Eu³⁺@Lap/TTA hydrogel can also detect and recognize Cu²⁺through its quenching response to fluorescence.At the same time,the hydrogel whose fluorescence is quenched by Cu²⁺can also be used as the fluorescent probe of small molecule DMSO to realize the real-time detection of DMSO.