Regulation Of The Spectral Properties Of Carbon Nanodots And Their Sensing Application

Carbon nanodots(CNDs)are a new class of fluorescent nanomaterials.Due to their easy preparation,high quantum yield,high photostability,good biocompatibility and low cost,they have attracted great interest in energy devices,sensing and biological research fields.CNDs can act as fluorescent probes for detection of ions or small molecules.The sensing mechanism includes photoinduced electron transfer(PET),fluorescence resonance energy transfer(FRET),inner filter effect(IFE)and so on.Detection of a certain target molecule requires high sensitivity and selectivity,in this project,the sensing property of the CNDs was improved through regulation of their spectral properties,and the mechanism of sensing was investigated in detail.The thesis can be divided into three parts:1.Selective detection of acetone via inner filter effectA new kind of fluorescent probe using CNDs was constructed for detection of acetone.Taking advantage of the unique optical property of acetone,selective detection was achieved via inner filter effect with the detection limit of 0.13 vol%.Furthermore,a new kind of CND was prepared using ?-lactoglobulin(LG).The spectral overlap between the CNDs and acetone was increased,leading to higher sensitivity with the detection limit of 0.09 vol%.2.Investigation of the sensing mechanism of photoinduced electron transferCNDs with different amount of surface NH2 groups and different quantum yield were prepared for detection of Cu2+ in aqueous solution.The results of the experiments showed that,the photoluminescence quantum yield of the CNDs,rather than the surface groups,had greater influence on the sensitivity of CNDs toward Cu2+.And a possible explanation of this was proposed.3.Preparation of fluorescent thin films for detection of Cu2+ in solid stateFluorescent thin film was prepared through optimization of the concentration or mixing ratio of CNDs/alginate composite.Two kinds of CNDs with –COOH and –NH2 covered on their surfaces were prepared for comparison.In solution,the CNDs with NH2 groups showed higher sensitivity toward Cu2+.While in the thin film,CNDs with COOH groups showed better response.These results were consistent with the different mechanism in solid and liquid states proposed in references.