Fabrication and Analytical Application of Nitrogen Doped Multifunctional Carbon Dots

Author:Lu Zuo Zuo

Supervisor:dong chuan


Degree Year:2019





Carbon dots(CDs)as a important member of the carbon family,due to their outstanding manifestation such as photoluminescence properties,biocompatibility,catalytic activity,electronic properties and so on,have made important contributions in multidisciplinary fields,for example the chemical or environmental detection,biological sensing,disease diagnosis and treatment,photocatalytic and photoelectric device.Heteroatom doping is a feasibility strategy for the preparation of functionalized CDs,which can effectively adjust their inherent natures.It provides a new way to develop the new applications of CDs in different areas.Therefore,there is an increasing concern of the study of the properties and applications of heteroatom-doped CDs.In this paper,three kinds of nitrogen-doped multifunctional CDs with excellent properties were prepared.After the analysis of their properties,they were applied to the detection of metal ion,amino acid,antibiotics and environmental pollutants,cell imaging and MS matrix.Chapter 1: Carbon dots and its application are reviewed.Firstly,we outlined the luminescence properties of CDs,the classification and properties of doped CDs,especially the advantages of dopping nitrogen for the adjustment of CDs’ performance.Then,we introduced the research progress of CDs as the analysis and detection platform.The application of CDs in the field of spectral analysis such as fluorescent sensors,biological imaging,fluorescence drug carrier and optical diagnosis were emphasically summarized.Chapter 2: Nitrogen doped carbon dots(N-CDs)were prepared by one step microwave-assisted pyrolysis of the precursors with DL-malic acid as carbon source,ethanolamine as nitrogen source.Through the extensive characterization on morphology,chemical structures and optical properties of N-CDs,it was found that the obtained N-CDs exhibited fine dispersion in water,good luminescence stability,excellent biocompatibility and low toxicity,which can be applied for multicolor cell imaging.Besides,based on the dynamic fluorescence quenching of N-CDs by Fe3+,a Fe3+ fluorescence sensor with high selectivity and sensitivity was constructed.The linear range of the sensor is 6.0–200 μM and a limit of detection is 0.80 μM.Chapter 3: The blue fluorescent nitrogen doped carbon dots(CNDs)have been synthesized via one step microwave-assisted pyrolysis.The fluorescence of CNDs can be effectively quenched by Arg,due to the strong interaction between Arg and CNDs,then the fluorescence recovered upon addition of Cu2+.Meanwhile,the CNDs also can give dual responsive signals of a visible color change(yellow-pink-light yellow).Therefore,CNDs-based colorimetric and fluorescent dual-readout mode sensors were constructed and utilized for sequential detection Arg and Cu2+.The sensors displayed high sensitivity and selectivity toward Arg and Cu2+ with low detection limit 0.26 μM and 0.17 μM,respectively.Besides,CNDs also was extended to cellular imaging.An “AND” logic gate based on the fluorescence changes of CNDs has been constructed.Compared with single fluorescence detection,the visual detection characteristics of the sensor have more advantages in practical application.Chapter 4: The yellow fluorescent carbon dots(Y-CDs)with superior optical performance,good biocompatibility and low cytotoxicity were synthesized via one step hydrothermal treatment of o-phenylenediamine(o-PD)and 4-aminobutyric acid(GABA).The Y-CDs can be utilized to the direct monitoring the amount of fluoroquinolones(FQs)based on fluorescence static quenching owing to the specific interaction between FQs and Y-CDs.Then the fluorescence of this system can be effectively recovered upon addition of histidine(His).Hence,an “On-Off-On” multi-functional fluorescent sensing platform based on Y-CDs was designed for the detection of FQs and His.The sensors exhibited high sensitivity and selectivity toward three kinds of FQs and His with a low detection limit of 17-67 n M and 35 n M,respectively.Benefiting from these outstanding characters,the Y-CDs were successfully employed for trace detection of FQs in real samples such as antibiotic tablets and milk products.Furthermore,the application of Y-CDs in cell imaging was also explored.All of the above prove this multi-functional sensing platform presents great prospect in multiple applications such as biosensing and environmental monitoring.Chapter 5: The nitrogen-doped carbon dot(N-CDs)prepared in chapter 2 have good UV absorption capacity and solubility,which as a matrix can detect of environmental pollutants hydroxy-polycyclic aromatic hydrocarbons(OH-PAHs)by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS)in negative ion mode.The use of N-CDs matrix exhibited low matrix background interference and was beneficial to improve the signal response due to the specific π-conjugated polyaromatic structure and the doping of nitrogen atoms.The developed method was found to have good reproducibility and sensitivity.The N-CDs as a new matrix also was employed for the detection of OH-PAHs in real PM2.5 samples.The mass concentrations of Σ-hydroxy-pyrene,Σ-dihydroxy-anthraquinone and Σ-dihydroxy-benzo(a)pyrene on the collected PM2.5 samples ranged from 0.125 to 0.136 ng/m3,0.039 to 0.052 ng/m3 and 0.053 to 0.072 ng/m3,respectively.This work extends the application field of N-CDs and provides a good candidate of matrix for MALDI-TOF MS detection of small molecule compounds.