Preparation And Application Of Novel Graphene And Graphene-like Quantum Dots

In this article,we synthesized and studied three kinds of novel quantum dots,One is graphene quantum dots?GQDs?directly generated from electrochemical oxidation of graphite electrode in alkaline alcohols;one is boron nitride quantum dots?BNQDs?prepared using liquid exfoliation-solvothermal treatment of bulk BN in three different solvents;one is as molybdenum disulfide quantum dots?MoS₂ QDs?using a facile solvothermal methods and the precursors were sodium sulfide?Na2S?and molybdenum chloride?MoCl3?.Herein,GQDs with an average diameter of?4.0 ± 0.2?nm and high crystallinity were simply produced from electrochemical oxidation of the graphite electrode in alkaline alcohols.The as-formed GQDs dispersion was colourless but it gradually changed to bright yellow when being kept at room temperature.Based on UV-Vis absorption spectra,fluorescence spectrophotometer,X-ray photoelectron spectroscopy?XPS?,Fourier transform infrared spectroscopy?FT-IR?and high-resolution transmission electron microscopy?HRTEM?,this colour change appeared to be due to oxygenation of surface species over time.Furthermore,the GQDs were used in specific and sensitive detection of ferric ion?Fe3+?as well as the lowest detected concentration of 1.8 ?M?S/N = 3?.The application of GQDs for Fe3+ detection in tap water was demonstrated.Finally,based on their good characteristics of low cytotoxicity and excellent biocompatibility,the GQDs were successfully applied to cell imaging.BNQDs were prepared using liquid exfoliation-solvothermal treatment of bulk BN in three different solvents.The photoluminescence of BNQDs was blue in ethanol?or N,N-Dimethylformamide?DMF??and green in N-methyl-2-pyrrolidone?NMP?under 365 nm UV irradiation,respectively.The quantum yields?QYs?and average lateral sizes of the BNQDs were 12.6% and 4.1 ± 0.2 nm,16.4% and 2.8 ± 0.3 nm,as well as 21.3% and 2.0 ± 0.2 nm in solvents of ethanol,DMF,NMP,respectively.The distinct sizes,QYs and optical properties of the BNQDs were found to have big effect on the polarity of these solvents.Different BNQDs can be chosen on-demand for versatile applications.For example,the green BNQDs were much more competitive than the blue ones when being served as a fluorescent sensing platform for label-free specific detection of ferric ions.While the blue ones in ethanol were much suitable for cell imaging and fiber staining.More importantly,electrochemiluminescence?ECL?property of the BNQDs was observed and studied for the first time using cysteine as a coreactant.The possible ECL response mechanism of the BNQDs system was also proposed.Herein,a facile bottom-up solvothermal method was proposed to synthesize MoS₂ QDs.The as-prepared MoS₂ QDs were highly photo-stable,low in cytotoxicity and exhibited blue fluorescence under UV-irradiation.The average size of the MoS₂ QDs was found to be 1.8 ± 0.2 nm.The possible generation mechanism of the MoS₂ QDs was also proposed and systematically studied.In addition,based on the good characteristics of low cytotoxicity and excellent biocompatibility of the as-prepared MoS₂ QDs,they were successfully applied to cell imaging.