Preparation Of Luminescent Probes Based On Carbon Dots And Study Of Luminescence Properties

Carbon dots(CDs),a new class of carbon nanomaterials with with sizes below 10 nm,have attracted considerable attention.They show fascinating advantages including small size,excellent water solubility,good biocompatibility,low cytotoxicity,high photostability,tunalble excitation and emission fluorescence,ease to achieve surface functionalization and so on.Due to the excellent properties,CDs could be used in a wide range of applications,such as analytical sensing,bioimaging,photocatalysis and so on.This work focuses on the synthesis and fluorescence performance of fluorescent CDs through hydrothermal process,calcination and reflux method.The obtained CDs were used for bioimaging,heavy metal ion detections and photocatalyst design.The main contents of this paper are listed as follows:1.This experiment firstly synthesized CDs through hydrothermal method:CD1 prepared by adipic acid and triammonium citrate could be used as a fluorescent probe for sensitive detection of Hg2+.It shows good linear relationship for Hg2+ detection in the range of 4 ?M to 18 ?M.Furthermore,CD1 were applied to intracellular sensing and imaging of Hg2+ as a consequence of the fluorescence properties and the established low-toxicity.CD2' were synthesized 'by hydrothermal treatment of carbopol 934 and diethylenetriamine.Through the metal-ligand interaction,the prepared CDs can highly sensitive and selective detection of Co2+ in the range of 0-40?M.The color changes(from transparent to brown)of the solution can be clearly seen with naked eye.Moreover,the CDs are also successfully utilized for monitoring natural water quality about Co2+ contents.CD3 were synthesized from citric acid anhydrous and 4,7,10-trioxa-1,13-tridecanediamine.The fluorescence of CNDs quenched by dopamine demonstrates that electrostatic interaction and hydrogen bonding have taken place.With the addition of Al3+ or GSH,the CD3 were released and their fluorescence recovered.This CD3 based sensing platform exhibited potential applications in the field of biology and food analysis.2.Then calcination was used to synthesize hydrophobic CDs4.The result CD4 can be well dispersed in organic solvent.And CD4 can be used for Hg2+ detection in ethanol with high selectivity and sensitivity.Then CD5 which can be dispersed both in water and organic solvent were synthesized by simply modifying CD4 with long-chain cationic surfactant.Then we designed a FRET system for detecting Al3+ by using CD5 and morin(MR),in which the CD5 served as donor and MR-A13+ as acceptor.Being associated with low toxicity and good biocompatibility,the method was also applied for intracellular imaging Al3+ in cells.3.We synthesized CD6 by one-step potassium hydroxide-assisted reflux method from dextrin.The obtained CDs shows strong blue fluorescence under 365 nm UV light and upconversion fluorescence at near infrared light.The CDs can be used as a dual-functional fluorescent probe for 2,4,6-trinitrophenol(TNP)and Fe3+ using down and upconversion fluorescence as excitation sources.The fluorescence response changes linearly with TNP and Fe3+ concentration in the range of 0-50 j}M and 8-40?M.4.At last we applied CDs in the field of photocatalyst.Because of the excellent fluorescence properties of CDs prepared by hydrothermal,calcined and reflux method mentioned above,these CDs can be used to broaden the light range of the photocatalyst using and enhance their catalytic efficiency.Herein,W03 was doped with CDs through a simple hydrothermal method to enhance the I photocatalytic activity.The photocatalytic performances of the result CDs/WO3 under visible light irradiation were reported.It had higher photocatalytic activity than pure WO3 and CD1 alone,and the photo degradation efficiency of MB reaches 100%after 0.5 h.In addition,· we used CD6 to decorate graphitic carbon nitride(C3N4)via a facile impregnation-thermal method.Under visible light irradiation,the prepared CD6/C3N4 has a higher degradation rate than pure C3N4 and CD6.We also give the possible mechanism for the high photocatalytic activity of these photocatalysts.