Preparation And Characterizations Of Carbon Dots

Carbon nano dots(CNs)have attracted lots of attention these years because of their biocompatibility and convience in prereration.In this paper,electrochemical and hydrothermal preparation methods are used for preparing CNs.The effect of CNs as energy donor on DNA hybridization,reactants on CNs' properties and aggregation on fluorescent properties of CNs were studied.Details as follows:1.Carbon electrode was used as working electrode and counter electrode and silver/silver chloride(Ag/AgCl)as a reference electrode.The CNs with green fluorescence were prepared by oxidation of carbon electrode.The CNs were characterized by transmission electron microscopy(TEM)and atomic force microscopy(AFM).The prepared CNs are used for energy donor,by connecting the Cy3 labeled single stranded DNA with a cationic polymer which is short for PDADMAC.In other words,negatively charged CNs and Cy3 labeled single stranded DNA form a sandwich structure through the electrostatic interaction in the presence of the cationic polymer,PDADMAC.A sensing platform for DNA hybridization based on FRET has been designed and demonstrated using CNs as a donor.2.Using hydrothermal method,triethyl phosphonoacetate and phophous acid as reactants to prepare phosphorous doped and water-soluble fluorescent CNs.When the concentration of fluorescent CNs increases,the peaks of fluorescence peak shifts to red.On contrast,when the concentration of fluorescent CNs decreases,the fluorescence peak shifts to blue.The observed fluorescence peak's red shift is due to the aggregation of CNs.3.In this work,we found thst the fluorescent properties of nitrogen doped CNs can be controlled by choosing reactants.We choose citric acid or glucose as carbon source,4,7,10-trioxy-1,13-tridecylenediamine or dopamine as nitrogen source to make four different kinds of CNs.After CNs were characterized by transmission electron microscopy(TEM)and atomic force microscopy(AFM).In conclusion,apart from optical properties,the electrochemical properties of CNs can be controlled by reactants,such as sensitivity in pH and photovoltaic property.The CNs prepared in the presence of TTDDA possess much stronger photoluminescence than those prepared in the presence of dopamine.However,the CNs obtained with dopamine show better pH sensitivity due to the existence of dopamine/dopamine analogues that are electron acceptors.These results clearly demonstrate that optical and other physicochemical properties of CNs can be tuned by the use of appropriate reaction precursors and provide us a new way to control the properties of carbon dots.4.By hydrothermal method,choose ethidium bromide which has electrochemical properties as the only reactant,to prepare CNs which also have electrochemical properties.The fluorescence peak of carbon dots is at 510nm and does not vary with the excitation wavelength change.The cyclic voltammetry test results show that when the pH is 0.54,the CNs have a reduction peak at-0.63.With pH increasing,the reduction peak moves positively.We can use the change to detect pH in solutions.