Synthesis Of Novel Carbon Dots And Their Applications In Analysis

As a class of novel fluorescent nanomaterials, carbon dots（CDs） have attracted tremendous attentions in recent years owing to their captivating properties such as excellent photostability, favorable biocompatibility, low toxicity, good water solubility, and robust chemical inertness and so on. In order to develop and expand the application of CDs, a great deal of work has been done on the synthesis of novel CDs and investigation of their application. Nowadays, various CDs have been synthesized and applied in a wide range of applications including bio-imaging, drug delivery, photodynamic therapy, catalysis, and sensing. However, there were only few species of CDs have been reported and fundamental theory of CDs needs to be perfected, which seriously limited their development and applications. Aptamers are DNA or RNA oligonucleotides which can specifically bind to target molecules. Aptamers possess strong affinity with targets similar to the interaction between antigen and antibodies, and aptamers possess great advantages over antibodies in stability, such as low-cost, and easy synthesis and labeling. There are many aptamer-based assay methods have been developed in recent years for the selective sensing of a variety of target molecules, but few aptasensor employes carbon dots as fluorescent probe. Compared with traditional fluorescent sensor, CDs-based aptasensor exhibits greater potential due to their superiority in chemical inertness, ease of functionalization and resistance to photobleaching.In this paper, several natural materials were employed as carbon source for the synthesis of functionalized CDs via one-step hydrothermal treatment. These prepared carbon dots display excellent fluorescence properties, great biocompatibility, high stability and good water-solubility. Combined with other materials such as DNA and gold nanoparticles, we mainly study their application in biosensor. The specific contents are as follow:1、Novel fluorescent nitrogen and sulfur co-doped carbon dots（N,S,C-dots） were synthesized by hydrothermal treatment of garlic. It was confirmed that the prepared fluorescent nanodots were doped with nitrogen and sulfur in the format of pyridinic-N, pyrrolic-N and thiophene-S. The N,S,C-dots displayed strong fluorescence with quantum yield of 13%, and the fluorescence can be efficiently quenched by Fe³⁺. Based on the results, Fe³⁺ sensor was successfully developed and utilized to detect Fe³⁺ in environmental waters with excellent sensitivity and repeatability. Eventually, the carbon dots were applied for cell imaging, demonstrating their potential toward diverse applications.2、A novel N-CDs were synthesized by the hydrothermal treatment of pancreatin. The prepared N,C-dots were utilized as fluorescent probe and assembled on aptamer/AuNPs by electrostatic interactions. The fluorescence of the N-CDs was quenched by AuNPs due to fluorescent resonance energy transfer from N-CDs. When AFB₁ was added to the assay solution, specific interactions between AFB₁ and the aptamer caused release of the N,C-dots. The fluorescence of the N,C-dots recovered and the intensity increase could be used to calculate the amount of AFB₁ added. The assay exhibits super-high sensitivity and selectivity. A novel aptasensor is thus successfully constructed; it provides an efficient way for sensitive AFB₁ sensing. In addition, we demonstrated that the proposed method may be used for the development of other aptamer based highly efficient sensors in other fields.3、A novel iron-containing carbon dots（Fe-CDs） were synthesized by a one-pot hydrothermal treatment of PEI and Hemin. By XPS and XRD results, it is found that the prepared carbon dots were doped mainly with nitrogen, and trace amounts of iron element, which combined the fluorescent feature of carbon dots with the peroxidase activity of hemin, displayed potential application in fluorescent and catalytic sensor. In addition, the Fe-CDs exhibited excellent water-solubility which improved application of hemin in aquoes solution（Hemin is poorly soluble in water）. Herein the Fe-CDs were utilized to develop colorimetric and fluorescent sensor for the detection of dopamine（DA） based on the H2O2 mediated catalytic oxidation of TMB. The proposed method provided a new strategy for the detection of DA...