Preparation And Fluorescence Properties Of Carboxymethyl Chitosan

Carboxymethyl chitosan（CMCh）has a broad application prospect in wastewater treatment because of its good biodegradability,water solubility and adsorption.In addition,their unique structure gives them the property of self-fluorescence.This unconventional fluorescent material overcomes the disadvantage of aggregation suppression of fluorescence of traditional fluorescent materials.Therefore,Therefore,many researchers are interested in elucidating the luminescence mechanism.By studying the synthesis and physicochemical properties of CMCh,the understanding of luminescence mechanism has been further developed and new luminescent materials have been developed.In this study,CMCh was prepared by aqueous phase method.The effects of sodium hydroxide and chloroacetic acid content,reaction temperature and reaction time on CMCh substitution degree were investigated.The structure,degree of substitution,solubility and isoelectric point were characterized by FT-IR,¹H NMR and UV-Vis.In particular,the effects of CMCh substitution degree,CMCh concentration,ethanol ratio,solution p H value and heat treatment on the fluorescence intensity in vivo were studied.The results showed that the substitution degree of CMCh was improved with the increase of sodium hydroxide content and the prolongation of reaction time.The degree of substitution of CMCh was first increased and then decreased by increasing the amount of chloroacetic acid and increasing the reaction temperature.By characterizing the solubility of CMCh,we found that CMCh with high substitution degree had better solubility under alkaline condition（p H>7）,and its isoelectric point tended to move to low p H.At the same time,the higher the concentration of CMCh,the higher the p H value or the higher the heat treatment temperature,the stronger the spontaneous fluorescence intensity of CMCh solution.The higher the ethanol content,the higher the fluorescence intensity of CMCh,and then the lower.At the same time,Cd²⁺can significantly enhance the fluorescence of CMCh solution,and it is linear at a certain concentration of Cd²⁺.Using this point,Cd²⁺can be detected in aqueous media.During the study,we found that CMCh can also produce light in the thin film state.Different metal ions have different effects on the fluorescence intensity of CMCh films.Cd²⁺can amplify,Fe³⁺and Cu²⁺can extinguish.Therefore,the difference in brightness of CMCh films after immersion in different concentrations of Cd Cl₂solution can only be observed with an UV lamp.Therefore,CMCh membrane has a good application potential in the fields of fluorescence membrane sensor and heavy metal wastewater treatment.