Fabrication And Application Research Of Fluorescent Carbon Nanoparticles

Fluorescent carbon nanoparticles (CNPs) have received wide attention by researchers due to their excellent optical properties with excitation-tunable light emission, good fluorescence efficiency, and strong light resistance. Compared to traditional semiconductor quantum dots, CNP is the best alternative due to low cytotoxicity and excellent biocompatibility. In this work, the fluorescent CNPs were prepared by different synthesis methods. The optical properties of as-synthesized CNPs were characterized by several methods. And then the as-prepared CNPs were applied for metal ion detection and biological imaging.Chapter 1:We summarized the composition, properties, and function of CNPs. And on this basic we reviewed the research progress of the synthesis methods, optical and biological properties, and applications of CNPs.Chapter 2:A fast and facile approach to synthesize highly nitrogen (N)-doped carbon dots (N-CDs) by microwave-assisted pyrolysis of chitosan, acetic acid and 1,2-ethylenediamine (EDA) as the carbon source, condensation agent and N-dopant, respectively, is reported. The obtained N-CDs are fully characterized by elemental analysis, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction pattern (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption, and photo luminescence spectroscopy. Doping N heteroatoms benefits the generation of N-CDs with stronger fluorescence emission and a ?s as high as ca. 20.1%. As the emission of N-CDs is efficiently quenched by Fe3+, the as-prepared N-CDs are employed as a highly sensitive and selective probe for Fe3+detection. The detection limit can reach as low as 10 ppb, and the linear range is 0.050=1.8 ppm Fe3+. The as-synthesized N-CDs have been successfully applied for human renal carcinoma cells imaging and detecting Fe3+in biosystem.Chapter 3:Phosphorous and nitrogen co-doped carbon dots (P,N-CDs) with satisfactory quantum yield (9.42%) have been prepared through one-step acidic oxidation of pumpkin by H3PO4 at low temperature (90?). The as-prepared P,N-CDs share some desired properties such as narrow size distribution, high fluorescence ?s, yellow emission, ?cx-dependent fluorescence emission, large Stokes shift, good reversibility, excellent photostability, and cell membrane permeability. The P,N-CD displays a remarkable emission enhancement in the yellow fluorescence region (?em=550 nm) when the pH is increased from 1.5 to 7.4. The pKa value of P,N-CDs was found to be 4.17 and it shows linear response to the physiological range of pH 4.7-7.4, which is valuable for near-neutral cytosolic pH research. P,N-CDs hold these perfect properties and ultra-low toxicity, empowering their use in in vitro cell and in vivo zebrafish imaging. The confocal fluorescent microscopic images of subcellular distribution and the detection of pH in MCF-7 cells were achieved successfully, suggesting that P,N-CDs have excellent cell membrane permeability and are further applied successfully to monitor pH fluctuations in live cells with negligible autofluorescence.Chapter 4:Hollow fluorescent carbon nanoparticles (HC-NP) were synthesized by simply mixing glacial acetic acid (CH3COOH), water, and phosphorus pentoxide (P2O5). An as-synthesized HC-NP sample has been proved to be a relatively complex mixture, and its complexity can be reduced significantly by high-performance liquid chromatography. An unprecedented reduction in such complexity can reveal fractions of HC-NP with unique luminescence properties. The HC-NP fractions are fully anatomised by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), displaying their fragmentation mass ion features. The fractionated HC-NP show profound differences in emission quantum yield, allowing for brighter and red fluorescence HC-NP to be isolated from an apparent low quantum yield mixture. The all fractions show good photostability and have been demonstrated to be excellent probes for cellular imaging. In addition, the selected four fractions including red fluorescence HC-NP have been successfully applied for human breast adenocarcinoma cells imaging, inferring that they could only pass through cell membranes to reach the cytoplasm.Chapter 5:An innovative phosphorus-nitrogen dual doped hollow carbon dots (PNHCDs) has been fabricated by simply mixing glucose,1,2-ethylenediamine (EDA), and concentrated phosphoric acid (H3PO4). This is an automatic method without external heat treatment to rapidly produce large quantities of PNHCDs, in contrast to other syntheses of fluorescent carbon dots that required high temperature, complicated operations, or long reaction times. The as-prepared PNHCDs possess small size, abundant phosphate/hydroxyl/pyridinic/pyrrolic-like N groups, and hollow structure, endowing PNHCDs with fluorescent properties. The as-prepared PNHCDs was developed for anticancer drug nanocarrier. Doxorubicin (DOX), as a model anticancer drug, PNHCDs demonstrate a very high loading capacity (35.43 weight%) toward DOX benefited from the hollow cavity structure as well as the supramolecular ? stacking and electrostatic interactions between the DOX molecules and carbon shell. In addition, a responsive release of DOX from DOX loaded PNHCDs (PNHCDs-DOX) can be activated by lowering the pH from 7.4 to 5.0 due to the presence of pH-sensitive phosphate groups on PNHCDs and amino groups on DOX molecules. Furthermore, PNHCDs-DOX exhibits better antitumor efficacy than free DOX owing to its enhanced nuclear delivery in vitro and tumor accumulation in vivo, resulting in highly effective tumor growth inhibition and improving the rate of cancer therapy in clinical medicine.