| The process of the two-photon absorption (TPA) possesses two key features: absorbing longer wavelength with lower energy but emitting shorter wavelength and better spatial resolution in three dimensions especially the axial depth discrimination. So researchers have made lots of efforts on the TPA materials and their applications recently, and the application on biology attracts more and more attentions, especially after the invention of novel microscopy based on two-photon excited fluorescence. In contrast, the materials used as biological fluorescent probes are still conventional single-photon fluorescent molecules whose TPA cross-section and fluorescence quantum yield are so low that limiting the applications of two-photon fluorescent technology in biology, so design and synthesis two-photon molecules with appropriate water-solubility and large TPA cross-section are very important.Two-photon polymerization is another powerful technology which has recently been applied to generate three-dimensional micro-structures and photonic devices. But the photo-polymerization mechanism remains unclear, and the development of the two-photon polymerization technology is hindered in respect that the relationship between the structure and property is also unclear and the effective initiators are still rare, so exploring the mechanism has a vital significance.Based on these above, our group have made lots of efforts and obtained some certain progresses. The main content and results of this thesis are listed as follows:1. Taking the carbazole as the parent substance, simultaneously further considering the water-soluble, relative better TPA cross-section and the fluorescence quantum yield, I have designed and synthesized two new compounds (PVEC and BPVEC) by introducing hydroxyl, then the physical and optics properties have also been charactered. The results showed that they are better water-soluble, and although polar solvent can quench the fluorescence intensity, we still observed the two-photon fluorescence phenomenon in water; moreover, The TPA cross-section of BPVEC is as high as 155GM measured by Z-scanning technology and they have a potential application serving as the biological fluorescence probe.2. The influence of environment (such as PH, solvent and K~+) to the optical properties of the compounds (MVEC and BMVEC), the spectrum changes with mutually affects between the compounds and the nucleotide, DNA had been studied by our group. Based on these, this thesis shows the further research on the dyeing and imaging in living cells of the root of plant with BMVEC. The results show that it has a better cell permeability.3. Take the research on the mechanism of single-photon polymerization done before as an example, through the spectrum changes with mutually affects between the initiator and monomer, we proposed that an exciplex has formed between the BBAS (initiator) and TMPTMA (monomers) after absorbing photons. And the radical signal has been detected by electron spin resonance (ESR) in the mixture contains BBAS and CN97E60 after being excited with 600nm laser light. It comes to a conclusion that two-photon initiator with a D-π-D structure induced a radical photo-polymerization. |
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