Synthesis And Characterization Of Fluorescent Carbon Dots And Their Related Applications For Sensing

In recent years, fluorescent nanomaterials have been attracted numerous student’s ttentions, due to the wide range use of fluorescence probes in the field of chemical sensing, biological detection and cell imaging. Compared with tranditional fluorescent dyes, fluorescent nanomaterials not only have superior fluorescence properties, but also have the advantages of low toxicity and good biocompatibility. It provides a new research idea for biological testing, labeling and probes.. Recently, the fluorescent carbon dots(CDs) has gradually been an advanced research hotspot. CDs have gained tremendous attention, owing to their unique and tunable photoluminescence properties, exceptional physicochemical properties, high photostability, biocompatibility, and small size. Thus, based on the excellent characteristic of CDs, we seeked a kind of green environmentally carbon source material was been found. We explored one a new route to synthesize fluorescent carbon dots by a convenient and fast method, and researched the application of the CDs for environment detection, pharmaceutical analysis and function materials. The main contents are as follows:(1) An innovative and green strategy to synthesize carbon dots(CDs) has been successfully established for the first time. Significantly, the precursor of CDs and whole synthesis procedure were green, the CDs obtained here exhibited various advantages including high fluorescent QY, excellent photostability, non-toxicity and satisfactory stability. And the synthesis of CDs showed excitation-dependent emission character and infrared upconversion property. High resolution transmission electron microscope(HR-TEM) depicted that CDs were uniformly distributed with majority population at the size of 2 nm. Fourier Transform Infrared Spectroscopy(FTIR) revealed that there existing O-H, N-H, COOH groups and other functional group on the surface of CDs. Considering that Fe3+ can react with the group of CDs surfaces, we apply CDs as Fluorescent probes for Fe3+ determination. Fe3+ can combine with the CDs, leading to fluorescence quenching of CDs, and(F0-F)(fluorescent intensity decrease) value was in the linear relationship along with concentrations of Fe3+. Significantly, this new CDs described here were applied for cell imaging and fluorescent staining。(2) A new method for the synthesis of CDs was established by microwave method and further application of CDs to drug detection was studied. With rose petals powder as the carbon source, followed by reaction with phosphorus pentoxide, synthesis of fluorescent carbon dots by microwave. They possessed excellent properties, such as high salt tolerance and anti-photobleaching. Subsequently, we applied this type of CDs as fluorescent probes for sensitively and selectively assaying TC based on the mechanism that the energy of CDs was captured for forming new bonds between the surface groups of TC and CDs. This method could be applied for simple and rapid determination of TC in human urine, with recovery of 98.3%~102%, indicating the current approach may broaden ways for practically detecting TC in real samples.(3) Herein, we successfully prepared CDs based on cysteine serving as the carbon source, and further creatively synthesized reduced state carbon dots(r-CDs) via simply introducing NaBH4 into the solution of CDs. Significantly, this type of r-CDs innovatively played the role of a reducer for directly synthesizing AuNCs and AuNPs(AgNPs): firstly, using r-CDs, HAuCl4 and BSA, r-CDs–AuNCs were successfully synthesized, the r-CDs–AuNCs exhibited excitation and emission peaks at 375 and 630 nm respectively; we have successfully prepared AgNPs and AuNPs by using r-CDs without any additional reducing agent in the mild water bath. Further research confirms that the reductive groups on their surfaces providing r-CDs with excellent electron-donating capability, thereby facilitating the fast reduction of metal ions to corresponding metal nanoclusters or nanoparticles. Besides, this exploration may open a new scope of CD applications in synthesis of metal nanomaterials.In summary, we supposed that the research results describes above would be beneficial for us to understand deeply the their characters of CDs, and developed effective platforms for pharmaceutical analysis.