Preparation Of Biomass Polymer Dots By Microwave Hydrothermal Method And Its Application In Water Sample Detection

As an important branch of the field of carbon dots,polymer dots?PDs?have been widely studied in recent years.It is a kind of material whose nano structure is between carbon dots and polymers without carbonization process completely,even without carbonization process.The surface of PDs has rich polymer chain structure,which makes it have similar characteristics with polymers.It also has excellent fluorescence properties of carbon dots,is widely used in the fields of analysis and detection,biological imaging,LED devices preparation and so on.Although the sources of raw materials to make PDs are wide and the preparation methods are various,remains diffcult to scale preparation,and diffcult to prepare PDs with uniform particle size and similar properties in a short time,In the application,the detection methods based on PDs is mostly realized by fluorescence quenching,it leads to easy to be interfered and the accuracy is reduced.For these reason,we hope to select biomass raw materials that can be mass produced,and to prepare PDs by microwave hydrothermal method,we try to use the mechanism of fluorescence enhancement to realize the detection of analytes.The specific work is as follows:1.Using hydroxyethyl cellulose as the biomass polymer material for make PDs,and ethylenediamine as the crosslink agent,PDs with blue fluorescence was obtained by microwave hydrothermal reaction at 200?for 2 hours and dialysis purification.The experimental results show that,The optimal excitation wavelength and emission wavelength of PDs are 327 nm and 398 nm,respectively;The particle size distribution was narrow,and the average particle size was 1.9 nm;Moreover,Mn²⁺can selectively quench fluorescence of PDs in the form of static quenching.And we have successfully built a method for the determination of Mn²⁺in real water samples based on the fluorescence quenching of PDs.The linear range of the method is 5-100?M,the limit of detection is 0.75?M,and the recoveries are between 98.3%and101.3%.2.Using chitosan,a common biomass material,as raw polymer material for make PDs,and maleic acid as small molecule crosslinker,through the reaction of carboxyl group with hydroxyl group and carboxyl group with amino group under the microwave hydrothermal condition of 140?for 2 hours,the purpose of crosslinking linear polymer chitosan was achieved.Finally,PDs with green fluorescence was obtained.The particle size distribution of PDs are uniform,the average particle size was 2.1 nm,and the optimal excitation wavelength and maximum emission wavelength were 371 nm and 510 nm respectively.We found that levofloxacin can enhance the fluorescence of PDs,After adding Cu²⁺,the fluorescence of PDs can be restored through the interaction between Cu²⁺and levofloxacin.Based on this,we successfully constructed a"turn-on-off"detection system for detection of levofloxacin and Cu²⁺in water samples.The linear range of detect levofloxacin and Cu²⁺are 0-35?M and 0-100?M respectively,and the limit of detection are 0.19?M and 1.12?M respectively.