The Preparation Of Carbon Dots And Their Application In Environmental Analysis

Carbon dots (CDs) were found in recent years which have high fluorescent, they are nano-materials with zero dimension because of their three dimensions are within the nanoscale. CDs not only have the traditional semiconductor quantum dots like excellent optical performance, but also have low toxicity, good biological compatibility, good chemical stability and the advantages of simple synthetic. CDs as a novel fluorescent nano-material have more superior performance than the conventional fluorescent materials. So carbon dots have important application value in optoelectronic devices, fluorescent probe biological detection, biological imaging, biosensors, medical diagnosis, metal cation and anion analysis and catalytic fields.In this paper, an environmental-friendly and low-cost hydrothermal method was developed for preparation of high fluorescent CDs with the plant of Jinhua bergamot and black fungus as a carbon source. Then we exploded the CDs’ selectivity and sensitivity for metal ion as a fluorescent probe. The main contents of this article are as follows:(1) An environmental-friendly, low-cost and high fluorescent hydrothermal method was developed for preparation of water-soluble fluorescent CDs with the plant of Jinhua bergamot as a carbon source. The prepared CDs were well-dispersed characterized by TEM (transmission electron microscope);-CO-NH-and C=O functional groups were in the surface of the CDs characterized by FT-IR (fourier transform infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy); under UV light (365 nm), the CDs could be seen blue fluorescence; the quantum yield is up to 50.78% and the lifetime is 3.84 ns. The fluorescence intensity of the CDs is not affected by pH or ionic strength or time which has the high stability. The fluorescent CDs can be quenched by Hg2+ and Fe3+ in different conditions, respectively. Then we can effective, rapidly and low-cost to detect Hg2+ and Fe3+ in the environment. Fluorescence spectrophotometry was used to explore the impact conditions about the pH, reaction time, ionic strength between CDs and Hg2+ and Fe3+. And set up the method of quantitative detection of Hg2+ and Fe3+ with broad linear ranges of 0.01-100 μM for Hg2+ and 0.075～100 μM for Fe3+, as well as low detection limits of 5.5 nM (Hg2+) and 0.075 μM (Fe3+).(2) High fluorescent and will-dispersed CDs synthesized by hydrothermal method with black fungus and urea as carbon source. The CDs could quenched by Cu2+, so we can selectively to detect Cu2+. They will become more sensitive and specific to Cu2+after modified Ag in the surface of the CDs as-prepared. We can see that the Ag-CDs were well-dispersed and have a bigger particles compared with the CDs before modified by TEM (transmission electron microscope);-CO-NH-and-COOH functional groups were in the surface of the Ag-CDs characterized by FT-IR (fourier transform infrared spectroscopy) and XPS (X-ray photoelectron spectroscopy); under UV light (365 nm), the CDs could be seen blue fluorescence; the quantum yield is up to 15.8% and the lifetime is 7.76 ns. The fluorescence intensity of the Ag-CDs is not affected by pH or ionic strength or time which has the high stability. Fluorescence spectrophotometry was used to explore the impact conditions about the pH, reaction time, ionic strength between Ag-CDs and Cu2+. And set up the method of quantitative detection of Cu2+with broad linear ranges of 0.057-50μM, as well as low detection limits of 0.057 μM.