Research And Application Of New Luminsecent Materials And Technologies

Carbon-based quantum dots (CDs) mean the nano-materials composed of mainly carbon element and present some unique optical properties. CDs mainly include carbon quantum dots (CQDs) and graphene quantum dots (GQDs). CQDs are usually carbon nano-particles with diameters less than 10 nm, while GQDs refer to single-layer or multi-layer graphene nanosheets with a diameter of less than 100 nm. Compared with the traditional quantum dots (QDs), CDs have many advantages, such as low cost, hydrophilic property, optical stability, good biocompatibility, and exhibit great potential applications in the fields of chemical sensing and biological imaging. Therefore, CDs have become a hot topic. This thesis includes three parts:(1) Non-toxic organics were used as the precursor to prepare functionalized GQDs with good biocompatibility and high fluorescence quantum yield (FLQY). And the obtained functionalized GQDs were applied for the detection of iron ions (Fe3+). (2) The effects of concentration of GQDs, pH value of solution, functional groups of GQDs on the FL behaviors of GQDs were investigated. (3) GQDs-MnO2 composite materials were synthesized and used in detection of some biological molecules.The thesis consists of the following four chapters.In chapter 1, the definition, basic properties, advantages, present status and development prospect of CDs have been firstly introduced. Furthermore, the purpose and significance of the research was put forward.In chapter 2, citric acid and L-cysteine were used as the precursors to prepare nitrogen and sulfur co-doped GQDs (N,S-GQDs) with high FLQY (60%), using a thermal decomposition method. The widths of the resulting N,S-GQDs range from 5-9 nm with an average width of about 7 nm, while the heights N,S-GQDs range from 0.5-3.5 nm with an average height of about 1.5 nm. Under 365 nm UV light, the resulting N,S-GQDs emit strong blue fluorescence, which can be quenched obviously by Fe3+. Accordingly, an N, S-GQDs based fluorescence sensor for detection of Fe3+ was finally developed. The sensor for Fe3+ shows a wide linear response range (4×106-1.5×10-4 M) and an acceptable detection limit (1.0×10-6 M, S/N= 3).In chapter 3, the single-layer GQDs (S-GQDs) prepared by chemical oxidizing XC-72 carbon black were chosen as a model to investigate the effect of some factors (concentration of S-GQDs, pH value of the solution, functional group) on the fluorescence behaviors of the S-GQDs.In chapter 4, GQDs and potassium permanganate were used to synthesize GQDs-MnO2 composite materials. The materials showed weak fluorescence due to the quenching effect of MnO2 on the fluorescence signal of GQDs. The weak fluorescence of GQDs-MnO2 can be increased by glutathione and L-cysteine due to the fact that MnO2 can decomposed by the thiol groups. Accordingly, a novel fluorescence sensor was developed for the detection of glutathione and L-cysteine based on the increased fluorescence signal. The linear response range of glutathione was from 8×10-7M to 8×10-5M, and the detection limit was 0.8 μM (S/N= 3), while the linear response range of L-cysteine was from 4×10-6 M to l×10-4 M, and the detection limit was 2×10-6 M (S/N= 3).