Construction Of Fluorescence Sensing Platform Based On Doped Carbon Dots And Its Application

Carbon quantum dots?CDs?are a new class of fluorescent carbon nanomaterials in recent years.Due to their small size,adjustable emission and excitation wavelengths,stable luminescent properties,good water solubility,simple synthesis method and surface functionalization,it has been widely concerned and applied in bioimaging and chemical biosensing fields.At present,the research of CDs mainly focuses on improving the quantum yield and emission wavelength regulation.In the past ten years,many efforts have been made to improve in the optical properties of CDs,however,the emission wavelength of reported CDs is mostly short wavelength,and the quantum yield?QY?is still relatively low.Therefore,in order to improve the QY of CDs and obtain ideal optical properties,this thesis plan to use a strategy of the heteroatoms doping?including metal atoms and non-metal atoms?to prepare a series of CDs with high QY.The morphology and structures of the prepared-CDs will be characterized detailed.In addition,their potential application in fluorescence sensing and fluorescent dying fields will be explored.The research contents mainly consist of the following three parts:1.A new rapid detection method for nimesulide?Nim?based on the boron?B?and nitrogen?N?co-doped carbon dots?B,N-CDs?as the fluorescence probe was developed firstly.The B,N-CDs were prepared by a facile hydrothermal treatment using ammonium citrate dibasic?AC?and bis?pinacolato?diboron?BPDB?as precursors.The as-prepared B,N-CDs exhibited good stability and strong blue fluorescence emission with a high quantum yield of68.89%and average diameter of 3.3 nm.The fluorescence of B,N-CDs was obviously quenched with the addition of nimesulide?Nim?.A good linear relationship between ln?F₀/F?and the concentration of Nim was obtained in the range of 0¹00?M,and the limit of detection was 125 nM.Furthermore,the proposed analysis method was successfully applied for the detection of Nim in pharmaceutical samples and recoveries ranged from 94.60%⁹6.73%.More remarkably,it was further found that the as-prepared B,N-CDs exhibited excellent solid-state fluorescence property and possessed potential application in invisible fluorescent ink for anti-counterfeiting and fluorescent dye.2.P,N-CDs were prepared by a one-pot hydrothermal method using ammonium citrate dibasic?AC?and ethylenediamine tetramethylene phosphonic acid?EDTMPA?as precursors.The as-prepared P,N-CDs exhibited strong blue fluorescence,high quantum yield?42.16%?,good stability performance?including salt tolerance,storage stability and photobleaching resistance?.The experimental results showed P,N-CDs could be used as fluorescent probe to detect TNP.The log F and TNP concentrations showed a good linear relationship in the range of 0.25-100?M with the detection limit of 100 nM.In addition,P,N-CDs possessed excellent solid-state luminescent properties,and which can be used as fluorescent recessive inks.3.Four kinds of metal?Mn,W,Nd and Mo?,nitrogen co-doped CDs?M,N-CDs?were prepared using AC and Tris as carbon sources and various metal salts as metal sources.Fourier transform infrared spectroscopy?FT-IR?and X-ray photoelectron spectroscopy?XPS?analysis revealed the presence of M-O bonds on the surface of CDs,verifying that Mn,W,Nd and Mo have been doped into CDs.Compared with undoped CDs,the QY of M,N-CDs were enhanced about 28%?Mn,N-CDs?,10%?W,N-CDs?,13%?Mo,N-CDs?and 52%?Nd,N-CDs?,respectively.More importantly,the fluorescence of Mn-CDs and W-CDs can be effectively quenched by Hg²⁺ion,based on this,we further construct the fluorescence sensors for Hg²⁺detection.The detection limits of Mn,N-CDs and W,N-CDs were 19 nM and 40 nM,respectively.