Preparation Of Carbon Dots Based On Acidic Ionic Liquids And Their Applications For The Detection Of Hg²⁺ And ClO^-

Carbon dots（CDs）,as a novel class of excellent carbon-based fluorescent nanomaterials,have attracted increasing attention because of their unique optical properties,non-toxicity,good water solubility,and easy surface functionalization.In recent years,these versatile carbon materials have been widely used in a many fields,such as bioimaging,drug delivery,chemical sensors,optoelectronics,and photocatalysis.At present,the facile,green,safe,and low-cost methods for fabrication of CDs with excellent optical properties are still need to be explored.Acidic ionic liquids with acidic functional groups in their cation or anion possess the advantages of mineral acid and ionic liquids,so that they are good catalysts and precursors for the preparation of CDs.In view of these reasons,the preliminary explorations were carried out on the application of acidic ionic liquids in the preparation of CDs.The main research contents and innovations are as follows:1.A moderate method was developed to synthesize water-soluble carbon dots by ionothermal treatment of cellulose with SO₃H-functionalized acidic ionic liquid as catalyst in 1-butyl-3-methylimidazolium chloride（[Bmim]Cl）.The preliminary explorations were carried out on the application of acidic ionic liquids as catalyst in preparation of CDs.Because of the presence of SO₃H-functionalized acidic ionic liquid,cellulose can be carbonized at relatively low temperature and atmospheric pressure.This method is safe,green,facile,and low-cost.The obtained CDs have excellent stability in high ionic strength,a certain degree of resistance to photobleaching,and excitation-dependent emission behavior.Moreover,the surface is rich of oxygenated groups,which make the CDs have good dispersity in water.2.A simple approach was developed to prepare nitrogen-doped carbon dots（N-CDs）by thermal treatment of 1,3-bis（carboxymethyl）imidazolium chloride and N-（2-hydroxyethyl）ethylenediamine.The effect of reaction time,reaction temperature,and mass ratio of precursors on the quantum yield（QY）of the N-CDs were investigated.The morphology,element composition,surface structure,and optical properties of the as-prepared N-CDs ware analyzed by transmission electron microscopy（TEM）,X-ray photoelectron（XPS）,fourier transform infrared（FTIR）spectra,UV-vis absorption,and fluorescence spectra,respectively.This method is facile and safe.The surface of obtainded N-CDs contains abundant –COOH,–OH,CONR,and –NH₂.The N-CDs have uniform morphology and blue fluorescence,and they possess good dispersity in water,fluorescent stability in high ionic strength,photostability,and excitation-dependent emission behavior.3.The as-prepared CDs were applied to sensitively and selectively detect the mercury（Ⅱ）ions and hypochlorite（ClO^-）in aqueous solution,respectively.In addition,the N-CDs prepared from 1,3-bis（carboxymethyl）imidazolium chloride and N-（2-hydroxyethyl）ethylenediamine can be used to detect ClO^-in the real samples with satisfactory recovery.