Preparation Of Polyaniline Functionalized Graphene Quantum Dots And Its Detection Of Cu²⁺

Graphene Quantum Dots(GQD)is a new type of carbon nanomaterials with excellent fluorescence properties.Compared with traditional semiconductor quantum dots,graphene quantum dots have good biocompatibility,low toxicity and high fluorescence quantum yield and it has been discovered to be used widely in the fild of environmental detection,biological imaging,the determination of heavy metal,fluorescence analysis,etc.In this paper,the nitrogen-doped graphene quantum dots were successfully prepared by hydrothermal synthesis using citric acid and urea as the resoruces of carbon and nitrogen respectively.Then the polyaniline functionalized graphene quantum dot nanocomposite(PANI-GQD)were prepared by a simple method of one step in-situ chemical oxidative polymerization of aniline.The optimal conditions for the synthesis of GQD and tubular PANI-GQD were obtained by varying the experimental factors.The structure and morphology of the prepared materials were analyzed by transmission electron microscopy,scanning electron microscopy,X-ray photoelectron spectroscopy,x-ray diffractometer,UV-visible absorption spectroscopy and fourier transform infrared spectrometer.The results show that the nitrogen-doped GQD with a particle size of 5 nm and the tube-formed PANI-GQD nanocomposite with an inner diameter of 60 nm and an outer diameter of 150 nm were successfully prepared.The fluorescence properties were characterized by fluorescence spectrophotometer.The results show that GQD exhibits excitation-independent fluorescence emission behavior.GQD have the strongest fluorescence emission intensity at 439 nm when the excitation wavelength is 350 nm.However,the PANI-GQD exhibits a fluorescence behavior of excitation-dependent.The maximum fluorescence emission peak position of PANI-GQD nanocomposite will be red-shifted with the excitation wavelength increasing.When the excitation wavelength is 420 nm,the strongest fluorescence emission intensity is exhibited at 500 nm.The fabricated tubular PANI-GQD is designed as a fluorescence sensor for the detection of Cu2+ in this paper.By investigating the factors which may affect the performance of the sensor,it was found that the optimal detection environment of the tubular PANI-GQD sensor is in the weakly acidic condition with pH=4.The sensor has high selectivity,anti-interference and sensitivity for the determinnation of Cu2+ in the PBS buffer of pH=4.And there is a good linear relationship between F/F0 and the concentration of Cu2+,when the concentration of Cu2+ is between 0.1?M-20?M.The limit of detection for Cu2+ can be reached 51nM by calcaulation.