Application Of Doped Carbon Quantum Dots In Fluorescence And Colorimetric Analysis

As a new type of carbon nanomaterial,carbon quantum dots?CDs?have the advantages of low toxicity,high fluorescence stability and excellent biocompatibility.It has received extensive attention in the fields of analytical chemistry,bioimaging,biomarkers and catalysis.The main contents of this paper are as follows.?1?Mn-doped carbon quantum dots?Mn-CDs?were successfully prepared by one-step hydrothermal method using 1-?2-pyridylazo?-2-naphthol?PAN?as carbon source and MnCl₂ as dopant.The fluorescence emission peak of the prepared Mn-CDs is located in the ultraviolet region?Em 360 nm?,and the fluorescence quantum yield is as high as 83.2%.Due to the good spectral overlap between then characteristic absorption?356 nm?of 2,4.6-trinitrophenol?TNP?and fluorescence emission pwak of Mn-CDs,TNP could quenching the fluorescence of Mn-CDs thought inner filter effect?IFE?.Further,the absorption peak of the other nitrobenzene compound hardly overlaps with the fluorescence emission peak of Mn-CDs,so that no IFE is generated.Based on this IFE,a new TNP high sensitivity and high selectivity fluorescence sensing method was developed.The parameters of the fluorescence sensing method were optimized and the selectivity and analytical performance of the sensing method were evaluated.The detection limit?3??was 12 nM,the relative standard deviation?RSD?was 2.6%?c=50?M,n=11?,with a linear range of 0.1 to 200?M.This developed method has been successfully applied to the detection of trace TNP in environmental water samples.?2?Chlortetracycline hydrochloride?CTC?has a characteristic absorption at 350nm at pH 6.0,Which has a large spectral overlap with the fluorescence emission peak of Mn-CDs.Under the optimized experimental conditions,the fluorescence emission intensity?log I₀/I?of Mn-CDs at 360 nm is linear with the concentration of CTC in the presence of CTC.where I₀ and I are the fluorescence intensities of Mn-CDs with and without CTC,respectively.The detection limit?3??for the CTC detected by the fluorescence method was 10 nM,and the relative standard deviation?RSD?was 2.1%?c=50?M,n=11?,with a linear range of from 0.1 to 200?M.Among a series of tetracycline molecules,chlortetracycline hydrochloride?CTC?can be degraded under alkaline conditions at room temperature.The CTC degraded product showed fluorescent properties,had a strong absorption peak at 340 nm,which had a large overlap with the emission peak of Mn-CDs.By further verification,the mechanism of action between CTC degraded product and Mn-CDs is the fluorescence resonance energy transfer mechanism?FRET?.Base on the above,a new method for determining CTC is established.The detection limit?3??was 19 nM of the method,and the relative standard deviation?RSD?was 4.1%?c=2.0?M,n=11?,the linear range was 0.1¹0?M,and the linear regression was I₀/I=0.85702.C+0.9996??M?.?3?Carbon quantum dots?CDs?were successfully prepared within 1 min with o-aminophenol as the carbon source and the acid-base neutralization heat of diethylenetriamine?DETA?and concentrated nitric acid as the heat source.The prepared CDs showed strong hydrophobicity.CDs have the discoloration properties of solvents in different polar solvents.As the polarity of the organic solvent increases,the fluorescence emission peak of the CDs red shifts?500 nm to 560 nm?.Due to the high hydrophobicity of CDs,traces of water in organic solvents have a quenching effect on the fluorescence of CDs.Based on this quenching effect,a new method for the determination of trace amounts of water in isopropanol and acetone solvents was developed.The fluorescence and digital colorimetric sensing method of trace water in organic solvents was carried out by comparing fluorescent color photography of CDs solutions with a laser source?480 nm?.A linear equation was established for the water content of isopropanol and the change in fluorescence of CDs.Y_Gray=-12.878C+1354.82,the linear range is 2.5-25%,and the correlation coefficient is 0.9901.A linear relationship was developed for the change in acetone water content and CDs fluorescence color.Y_Gray=-18.620C+2498.64,correlation coefficient is 0.9944,linear range is 2.5-20%.The developed method was successfully applicated detection the water content in organic solution with both fluorescence and colorimetric procedure.