Synthesis And Characterization Of Metal Element In Situ Doped Carbon Dots Derived From Chitosan/Me(OH)_n

Carbon dots has received more and more attention due to good fluorescence stability,chemical inertness and biocompatibility.In order to improve the properties of carbon dots,metal elements doped carbon dots comes into being.However,the current method of metal elements doped carbon dots is always complicated and universality for different metal elements.The precursors of carbon dots are also derived from small molecules.Therefore,researches on synthesis method of metal elements in situ doped carbon dots derived from the natural biomass needs to be carried out.In this paper,chitosan/Me(OH)_n were used as precursors to synthesize metal elements in situ doped carbon dots derived from chitosan.The optical properties were investigated by UV-Vis absorption spectroscopy and fluorescence spectroscopy.Quntum yield,synthesis yield and metal element content of different metal elements doped carbon dots was characterized.The phase structure,element composition and bonding state of metal elements doped carbon dots were characterized by TEM,XRD,FTIR and XPS.The effects of Na2 EDTA treatment and pH on the fluorescence properties of Zn element doped carbon dots derived from chitosan(Zn-CDs)was studied.Zn-CDs were used as fluorescent probes,and their effects on cell imaging,zebrafish imaging and ion detection were explored.The results showed that seven kinds of metal elements in situ doped carbon dots were synthesized by hydrothermal carbonization using chitosan/Me(OH)_n complex hydrogel as precursors.Specifically: 1)transition metal elements in situ doped carbon dots: Zn element in situ doped carbon dots,Mn element in situ doped carbon dots,Fe element in situ doped carbon dots;(2)rare earth element in situ doped carbon dots: Er element in situ doped carbon dots and Nd element in situ doped carbon dots;(3)the bimetallic elements in situ co-doped carbon dots: Zn-Mn in situ co-doped carbon dots and Zn-Er in situ co-doped carbon dots.The Zn element content in Zn-CDs was the highest,which was 3.67 wt%.The yield of Zn-CDs was also the highest,at 3.41 wt%.In addition,the quantum yield of Zn-CDs was 14.8%,which was 171% higher than that of undoped carbon(CDs).Zn-CDs were predominantly amorphous carbon and contained hexagonal wurtzite type ZnO nanoparticles.The average diameter of Zn-CDs was 5.5 nm.The main elements were C,N,O and Zn,and the mass ratio of C: N: Zn was 84.6: 10.9 : 4.5.Besides,there were-NH2,-OH and other active groups in Zn-CDs.Na2EDTA treatment of Zn-CDs can increased the fluorescence intensity of 2.90 times,but stability of Na2 EDTA / Zn-CDs mixed solution was poor,easy to sink.In the pH range of 4-8,the fluorescence intensity fluctuation of Zn-CDs was less than 1.95%,and it had good fluorescence stability under weak and weak alkaline conditions.They could emitting green fluorescence in the blue light field.Zn-CDs were ingested into the liver and digestive tract of zebrafish after being ingested into the body by zebrafish.Zn-CDs showed selective fluorescence quenching effect on Hg2+.The fluorescence intensity of Zn-CDs increased linearly with the increase of Hg2+ concentration in the range of 10-100 n M Hg2+ concentration,and the detection limit was 3.3?M.It provideed an universal method for the synthesis of transition metal elements and lanthanide rare earth elements in situ doping carbon point derived from chitosan/Me(OH)_n.