Studies On Preparation,Characterization And Application Of Novel Nitrogen Doped Fluorescence Carbon Quantum Dots

Carbon quantum dots（CDs）are quasi spherical nanoparticles with a particle size of less than 10 nm.CDs are deemed a better candidate than semiconductor nanomaterials from both environmental and health concerns for their alluring photoluminescent properties,good water solubility,excellent biocompatibility and low toxicity.In this paper,CDs have been studied from the following aspects:1.Nitrogen-doped CDs（N-CDs）have been synthesized using wool as raw material via pyrolysis and microwave treatment,providing a green way for the production of N-CDs without the use of toxic/expensive solvents and starting materials.The prepared N-CDs exhibit exceptional advantages including high fluorescent quantum yield（22.5%）,excellent biocompatibility,low toxicity,and satisfactory chemical stability.Depending on these superior properties,the N-CDs have been applied in multicolor bioimaging,patterning,and biosensing.Imaging of living cells has been observed with high resolution using N-CDs as a probe,which validates their use in imaging applications and their multicolor property in the living cell system.Additionally,the obtained N-CDs have been used as fluorescent inks for drawing luminescent patterns,showing favorable application in anticounterfeit and optoelectronic dimensions.Most strikingly,the as-prepared N-CDs could visualize Fe³⁺ fluctuations in living cells with negligible autofluorescence based on their high sensitivity and selectivity detection for Fe³⁺ ions with a linear range of 0.1–10 μM and a detection limit of 10 nM.2.Green-fluorescent nitrogen-doped carbon nanodots（N-CDs）have been fabricated by hydrothermal treatment of oolong tea.As-prepared N-CDs exhibit bright green fluorescence,excellent biocompatibility,low toxicity,and considerable optical stability.By virtue of these outstanding properties,the N-CDs have been utilized to intracellular Cu²⁺ imaging and paper-based Cu²⁺ sensing.Confocal fluorescent imaging of HepG2 cells indicates that obtained N-CDs could visualize Cu²⁺ fluctuations in living cells without autofluorescence interference based on their high selective and sensitive detection for Cu²⁺ ions in aqueous solution with a linear range of 0.01–75 μM and a detection limit of 2 nM.In addition,N-CDs stained paper-based sensor strips have been prepared for user-friendly and convenient Cu²⁺ determination.