Preparation Of Graphene Quantum Dots And Their Application In Ion Detection

Graphene quantum dots(GQDs),as novel and unique fluorescent nanomaterials,have the advantages of low toxicity,high fluorescence activity,excellent water solubility and photostability compared with semiconductor quantum dots and organic fluorescent dyes,and have potential applications in cell imaging,analytical detection and optical catalysis.In this paper,it mainly studies the preparation of graphene quantum dots and their applications in metal ion detection.The main contents are as follows:Boron-nitrogen co-doped graphene quantum dots(B,N-GQDs)were synthesized by bottom-up hydrothermal method using citric acid as carbon source,ethylenediamine as nitrogen source and phenylboric acid as boron source.The structures and properties of B,N-GQDs were studied by Transmission Electron Microscope(TEM),Atomic Force Microscope(AFM),Fourier Transform Infrared Spectrometer(FT-IR),X-ray Photoelectron Spectroscopy(XPS),Ultraviolet–Visible spectroscopy(UV-Vis),Photoluminescence Spectroscopy(PL)and fluorescence lifetime detection system.The results show that B,N-GQDs with high fluorescence quantum yield(QY=75%)and long fluorescence lifetime(?=12.86 ns)are successfully prepared.And the as-prepared B,N-GQDs exhibit size-uniform and multi-functional groups on the surface(-COOH,-OH,-NH_2,-B(OH)₂).What's more,it has good fluorescence stability at p H=5.0?10.0,[Na Cl]=0?1.0 mol/L and irradiation time<120 min.The prepared B,N-GQDs could detect both Hg²⁺and F^-ions in linear ranges of0.2?2.6?mol/L and 0.25?7.0 mmol/L,with detection limits of 0.16?mol/L and 0.18mmol/L,respectively,which were lower than the requirements for Hg²⁺(0.25?mol/L)and F^-(0.526 mmol/L)ions discharge from industrial wastewater in the Comprehensive Wastewater Discharge Standard.In addition,the effects of fourteen interfering metal ions and seven interfering anions on the detection of Hg²⁺and F^-ions by B,N-GQDs were determined,respectively.It was found that Mg²⁺,Ca²⁺and Fe³⁺ions could quench the fluorescence of B,N-GQDs,and other anions and cations did not affect the Hg²⁺and F^-ions detection processes.It could achieve accurate determination of Hg²⁺ion concentration by adding metal ion masking agent.What's more,the standard curves of Hg²⁺and F^-ions were used to determine the solution containing Hg²⁺and F^-ions.Compared with the known concentrations of Hg²⁺and F^-ions,the recoveries were 96.7-98.4%and 100.0-102.4%,respectively.The above shows that B,N-GQDs have high accuracy in detecting both Hg²⁺and F^-ion concentrations.3-aminophenylboronic acid modified graphene quantum dots(APBA-GQDs)were synthesized by top-down two-step hydrothermal method using graphene oxide as carbon source,hydrogen peroxide as strong oxidant and APBA as surface passivator.The structures and properties of APBA-GQDs were studied by TEM,AFM,FT-IR,XPS,UV-Vis and PL.It is found that the as-prepared B,N-GQDs exhibit high fluorescence quantum yield and uniform size.It have good fluorescence stability at p H=4.0?11.0,[Na Cl]=0?1.0 mol/L and irradiation time<120 min.