Synthesis Of Rhodamine Derivatives And Their Applications In Energy Transfer Systems And Super Resolution Microscopy

The energy transfer system and super resolution fluorescence microscopy are two major research topics, the former will help us understand the energy transfer process of photosynthesis, and the latter can facilitate the study of biological samples, specifically having a great significance to study the fine structure of the cells and interaction in cells. In this paper, we hope to explore the energy transfer system and super resolution fluorescence microscopy by synthesizing rhodamine derivatives, and to understand its intrinsic mechanism.Chapter 1 is mainly related to the background knowledge and theoretical basis. mainly divided into two parts, the fluorescence principle and the background knowledge of super resolution fluorescence microscopy. The fluorescence principle part includes:fluorescence excitation and emission, energy transfer, exciton, fluorescence lifetime and quantum yield, steady-state and time-resolved fluorescence spectroscopy and fluorescence spectrometer. And the Energy transfer part is divided into fluorescence resonance transfer energy (FRET) and electron exchange energy transfer. The exciton part contains Frekel exciton and Wannier-Mott exciton. The super resolution fluorescence microscopy part includes:the diffraction limit and super resolution fluorescence microscopic imaging technique. Among them, the super-resolution fluorescence microscopy imaging technology mainly introduces the stimulated emission depletion technique (STED), the structure light microscopy technique (SIM), the photo-activation localization microscopy technique (PLAM) and the stochastic optical reconstruction microscopy technique (STORM).In chapter 2, we demonstrate a highly fluorescent polymer consisting of repeating pendant dye molecules, difluoroboron dibenzoylmethane (BF2dbm), and an end-capped Rhodamine B (RhB) exhibits efficient energy transfer (EnT) owing to long-lived polymer excitons. External stimuli such as solvation and temperature can dramatically affect the efficiency of EnT and thus change the emission colour. Detailed theoretical calculations and ultra-fast laser spectroscopy studies on the donor-acceptor polymers reveal that in dilute solution intrachain BF2dbm aggregates lead to more forbidden and nearly degenerate singlet and triplet states. Thus these aggregate species serve as an exciton reservoir after photo-excitation, which is readily harvested by the RhB acceptor dye and contributes to the observed high EnT efficiency. The model system shows that very efficient EnT can be realized through long lived excited states in metal-free systems.In chapter 3, we can easily get a series of Rhodamine B derivatives with methyl terminated polyethylene glycol (RhB-4PEG. RhB-7PEG, RhB-10PEG, RhB-22PEG) using the esterification (DMAP and EDC·HCl as a catalyst). The photobleaching rate of Rhodamine B is very fast, after excitation about 2 s, the number of molecules which are in the "bright" state is very small, and then tends to be stable. Under the same experimental conditions, the photon number and the duty ratio of RhB, RhB-4PEG, RhB-22PEG show that with the increase of polyethylene glycol (PEG) unit number, the photon number and duty ratio of the Rhodamine B derivative increases first and then decreases. In the next work, we need to find a Rhodamine B derivative with suitable unit number of polyethylene glycol (PEG), making the photon number as much as possible while the duty ratio as small as possible, and achieving the optimization of super-resolution fluorescence images.