Preparation And Properties Of Two Photon Absorbing Nanocomposites Composed Of Organic Dye And Noble Metal

Two-photon absorption (TPA) behavior shows advantage in terms of excellent spatial resolution, deep tissue penetration, low interference of spontaneous fluorescence and photo-toxicity, for its promising applications in biological fields such as fluorescence sensing and two-photon excited fluorescence microscopy. Organic/noble metal nanohybrids can be defined as that organic and metal materials are integrated into ones through nanotechnology, which combines high stability of noble metal with the superiority of inorganic nanoparticles such as structural modification and nano-effects. This type of materials is prone to adjust and optimize the optical properties, which provide potentially application for two-photon microscopy imaging in living cells. In the present study, a series of novel organic dyes bearing TPA properties are designed and synthesized. Then, functional organic/metal nanohybrids are prepared from organic dyes coordinating to metal nanoparticles based on coordination chemistry theory in the presence of some biomolecules. Following, reveal the mechanisms of interaction between the organic-inorganic components and the optimization of optical properties, At last, research the potentially application for two-photon microscopy imaging in living cells, such as HepG2. The main contents of the deseration are as follows:(1)Preparation, optical properties and two-photon microscopy imaging of the Ll-Au-DNA nanohybridL1-Au-DNA nanohybrid is constructed through an ICT fluorophore-carbazole derivative (abbreviated as L1) coupled with gold nanoparticles (NPs) under the guidance of calf thymus DNA (ct-DNA). The coupling interactions between components at the interface, which results in a dramatically blue-shift of single-photon absorption and fluorescence and blue-shift of two-photon excited fluorescence. The coupling effect in the nanohybrid also leads to enhancement of nonlinear optical properties, including two-photon absorption (TPA) cross section (8) and two-photon absorption coefficient (β). The mechanisms of interaction’hot spot’ at the interface, charge transfer and enhance of TPA properties were investigated by time-resolved fluorescence measurement and Raman scattering experiment. The enlargements of TPA cross section and biocompatibility due to the existence of ct-DNA, which are proven to be potentially useful for two-photon microscopy imaging in living cells.(2)Preparation, optical properties and antibacterial effect of L2-AgnanohybridA D-π-A type carbazole derivative (E)-2-cyano-3-(9-ethyl-9H-carbazol-3-yl) acrylic acid (abbreviated as L2) was designed, which coupled with sliver nanoparticle (NPs) by in-situ composition. The coupling interactions between organic/inorganic components of the nanohybrid, which leads to an energy transfer process and further results in blue-shifted single-photon absorption, red-shifted one or two-photon excited fluorescence and increased FL lifetime. The coupling effect in the nanohybrid also leads to enhancement of nonlinear optical properties, including two-photon absorption (TPA) cross section (8) and two-photon absorption coefficient (β).The results of theoretical calculation and experimental data revealed the existence of MLCT process at the interface. The metal to ligand charge transfer (MLCT) at the metal and the organic interface was the main driving force for the optimization of optical properties. Further, enhanced antibacterialeffect of L2-Ag nanohybrids was observed on both gram-negative bacterium Escherichia coli and gram-positive bacterium Staphylococcus aureus, compared to either pure Ag NPs or pure L2.(3)Synthesized a series of organic dyes with D-π-A structure and investigated its photophysical properties.Three cyanoacetic acid derivatives L2-L4 with D-π-A (D=donor, A=acceptor) structure accompanied with intramolecular charge transfer (ICT) process, were systematically synthesized and characterized (through FT-IR,1H-NMR and 13C-NMR). The systematic study includes ICT process and optical properties were carried out through changing donating groups. The investigation of self-assemble in the nanoscale, which revealed that L2 showed a rod-like structure, L3 showed a rhombic structure and L4 showed a massive structure. The crystal structures of L3 and L4 were determined and shown that the weak intermolecular interactions played a leading role in the self-assembly process at nanometer scale.