Synthesis Of Fluorescent Carbon Nanomaterials And Applications In Sensing And Bioimaging

As a new type of fluorescent carbon nanomaterials, Carbon-based Quantum Dots (CQDs) show good photoluminescence (PL) and excellent electronic properties, and display the application in electronic devices, sensors, bioimaging and bioanalysis. In fact, traditional organic dyes used to be labeling reagent for dyeing or modify cells and biological molecules to identifying and measuring in the field of bioanalysis, and semiconductor quantum dots play an important role in electronic devices and sensors. However, this kind of tradition organic dyes also show some shortdraws, such as short PL lifespan, poor biocompatibility, ease of decomposition and breakdown products usually poisonous and harmful, and difficult muli-color at the same time, all of these drawbacks limit its application in bioanalysis. And heavy metal atoms also appear in semiconductor quantum dots that limit their application in electronic device and sensors. Contrast, CQDs can be a new labeling reagent, because of its good biocompatibility, high fluorescence intensity, chemical stability, narrow and symmetric emission peak.In this report, some works have been done based on different producer to synthesize CQDs and explored the properties in photoluminescence. As following:(1)A simple, facile, and green hydro thermal method was developed in the synthesis of water-soluble nitrogen-doped carbon dots (N-CDs) from streptomycin. The as-prepared N-CDs displayed good water solubility, excellent chemical stability, uniform particles size, low cell viability, and can be used as fluorescent probes for cell imaging.(2) A simple, low-cost, green, and solvent-free method was developed for producing sulfur-and nitrogen-co-doped carbon nanoparticles (SNCNs) by one-pot solid-phase thermal treatment of glutathione. The as-prepared SNCNs show good water solubility, excellent chemical stability, high quantum yield, and can be used as an effective fluorescent sensing platform for label-free detection of Hg2+ with high selectivity and sensitivity, even with high concentrations of interference (i.e. other metal ions).(3) A sensitive and selective fluorescent biosensor was developed for the detection of MTX based on N, S-codoped fluorescent carbon nanodots (NSCDs). The NSCDs were prepared by a facile, simple, low-cost, and green thermal treatment of ammonium persulfate, glucose, and ethylenediamine. The as-prepared NSCDs displayed bright blue emission with a relatively high quantum yield of 21.6%, good water solubility, uniform morphology, and excellent chemical stability, compared to pure CDs. The fluorescence of NSCDs can be significantly quenched by methotrexate (MTX) via fluorescence resonance energy transfer (FRET) from NSCDs to MTX, which was used for highly selective and sensitive detection of MTX. Moreover, this method was explored for practical detection of MTX in human serum with satisfied results.(4) Oxygen and sulfur co-doped graphitic carbon nitride quantum dots (OS-GCNQDs) with uniform sizes were prepared by thermal treatment of citric acid and thiourea. The as-obtained OS-GCNQDs show strong blue photoluminescence (PL) with a relatively high quantum yield of 14.5%. Furthermore, OS-GCNQDs exhibit stable and specific concentration-dependent PL intensities in the presence of mercury (Ⅱ) ions. More importantly, OS-GCNQDs were applied for cell imaging with satisfactory biocompatibility, which are a potential fluorescent probe in biosensing and bioimaging applications.