| The content of small molecules or ions which have biological function are closely linked to human health, so it is of great significance to develop rapid, sensitive and effective method to detect small molecules or ions. So far, several analysis methods have been widely used, mainly including chromatography, mass spectrometry, electrochemical method, colorimetric method and fluorescent method. Compared with other techniques, fluorescence method is one of most prevalent and promising analytical method owing to their significant advantages such as high sensitivity, good selectivity, real-time monitoring, simplicity and nondestructive properties. In recent years, a series of nanomaterials with special physical and chemical properties have been developed, following the appearance and development of nanotechnology. These nanomaterials offers a new opportunity for the construction of fluorescent probe. Manganese dioxide (MnO2) nanomaterials are widely used in testing and cell imaging owning to their simple preparation, low cost, good biocompatibility and low toxicity, strong fluorescence quenching ability and being reduced by reductant. Herein, we chose manganese dioxide nanosheets as fluorescence quenching agent and recognition unit, while ruthenium complexes and carbon quantum dots as fluorescence reporters to design the fluorescence porbe for GSH and ferrous ion dectction.The main research aspects of this thesis are as follow:1. Studies on ferrous ion detection based on MnO2 nanosheets quenched ruthenium complexes. In this paper, we, for the first time, discover that MnO2 nanosheets can be reduced into Mn2+ by Fe2+. Inspired by this, we develope a novel sensitive and selective fluorescence probe based on MnO2 nanosheets quenched Ru(bipy)32+for label free probing ferrous ion. In this nanoprobe, Ru(bipy)32+ which is insensitive to iron is used as fluorescence reporter, MnO2 is used as fluorescence quenchers and as recognition units. The fluorescence probe is constructed by electrostatic interaction between negatively charged MnO2 nanosheets and positively charged Ru(bipy)32+. The fluorescence of Ru(bipy)32+ is quenched in the absence of Fe2+. Conversely, the quenched fluorescence can be restored in the presence of Fe2+ which change the MnO2 into Mn2+.The fluorescence probe exhibits a low background fluorescence signal and a high sensitivity to Fe2+ in aqueous solutions. Importantly, the nanoprobe exhibit sensitive responses toward Fe2+ in complicated biological environments. Therefore, the nanoprobe demonstrates its potential in biological analysis detection.2. Studies on glutathione detection based on MnO2 nanosheets quenched carbon quantum dots. The carbon quantum dots, emerging as a new class of photostable luminescent nanomaterials, have received much attention in bioimaging, fluorescence nanoprobe and drug delivery with improved properties in terms of relatively good biocompatibility, chemical stability, high quantum yield and low cost. In this work, we chose the nitrogen-doped carbon quantum dots (CQDs) as fluorescence reporters, while MnO2 nanosheets as fluorescence quenchers and recognition units. The fluorescence probe for GSH detection is constructed by electrostatic interaction between negatively charged MnO2 nanosheets and positively charged CQDs. The fluorescence of CQDs is quenched by MnO2 nanosheets in the absence of GSH. However, the quenched fluorescence can be restored in the presence of GSH, which transform the MnO2 to Mn2+. Based on the fluorescence recovery of the MnO2-CQDs nanoprobe triggered by GSH, this nanoprobe exhibit a low background fluorescence signal, high sensitivity, good selective and rapid response to GSH in aqueous solutions. Furthermore, the nanoprobe can be applied not only to distinguish the normal cells and cancer cells but also to monitor the expression level of GSH in living cells via the fluorescence imaging of the intracellular GSH. Such a nanoprobe demonstrates its potential in disease diagnosis in the future. |
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