| Fluorescent carbon dots,as a new type of carbon nanomaterials,have been extensively investigated because of their tunable emission spectra,good photostability,excellent biocompatibility and good water solubility,which enable their application in biosensing and bioimaging.Previously,the synthesis methods of carbon dots used for the detection of hemoglobin and riboflavin were complex and require complicated experimental set-ups and high energy consumption.Thus,carbon dots synthesized at room temperature are of great significance.In this dissertation,blue-green luminescent carbon dots were synthesized at room temperature by base catalysis method from fructose,a renewable natural raw material.Then,they are successfully applied as highly-sensitive fluorescence probes for the direct detection of hemoglobin and riboflavin.The main discoveries in this dissertation are :1.Carbon dots were prepared using fructose and Na OH at room temperature.The structure of carbon dots was characterized by transmission electron microscopy and the average diameter is determined to be about 8.2 nm.The luminescence properties of the carbon dots were measured by using steady-state spectroscopy,showing that the fluorescence emission wavelength of the carbon dots is excitation-dependent,ranging from 450 nm to 520 nm.2.The synthetic carbon dots were used for the detection of hemoglobin,based on fluorescence quenching of carbon dots.The linear range of detection was 0-5μM with a detection limit of 243 n M.The biosensing mechanism was investigated by the Stern-Volmer equation,temperature-dependent fluorescence,the measurements of fluorescence lifetime and structure of hemoglobin.It is concluded that carbon dots can form nonfluorescent complexes with hemoglobin,quenching the fluorescence of carbon dots.3.The fluorescence intensity ratio of 530 nm to 450 nm linearly dependent on the concentration of riboflavin in the range from 0 μM to 5 μM,suggesting that the synthetic carbon dots can be used to dectect riboflavin with a limit of the detection of8.53 n M.Background interference and fluctuation under diverse conditions can be reduced by evaluating the ratio between the two emission band intensities at different wavelengths.The overlap between the absorption spectrum and the fluorescence emission spectrum showing that the mechanism for the detection of riboflavin is mainly the inner filter effect. |
