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Photo-Annealing of Merocyanine Aggregates
摘要： In this work we elucidate the fundamental difference between aggregate formation of donor-π-acceptor merocyanines in their electronic ground and excited states. While increasing the π-bridge size favors formation of π-stacked aggregates in the dark, irradiation with visible light causes reorientation of the dyes to form prototype H-aggregates with compensating dipole moments. This photo-annealing changes the supramolecular structure and its UV-vis spectroscopic properties dramatically, thus being of importance for the function of active layers composed of these dyes. Aggregates of the ground state dyes are bound cooperatively through ππ-London dispersion interactions and hydrogen bonds between the polar α-cyano-carboxylic acid groups. However, charge transfer upon photoexcitation leads to repulsion of the polar acid groups. Electronic excitation of the dyes approximately doubles the ground state dipole moment, thus driving molecular reorientation into prototype H-aggregate structures. We show that this photo-induced supramolecular rearrangement can disrupt the large polymeric aggregates formed in the dark. The photo-induced supramolecular structural changes reported in this work will influence the performance of optoelectronic devices composed of these structures and must be controlled to avoid morphological decomposition of active layers upon operation.
关键词： merocyanines,photo-annealing,H-aggregates,supramolecular structure,UV-vis spectroscopy,dipole moments,aggregate formation
更新于2025-09-23 15:21:21
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Aggregate Formation of BODIPY-Tethered Oligonucleotides That Led to Efficient Intracellular Penetration and Gene Regulation
摘要： Exogenous nucleic acids showed low e?ciency regarding cellular uptake and low stability in biological conditions; therefore, a number of techniques have been developed to improve their basic properties. One of the best solutions is the application of nanosized particles consisting of oligonucleotides that penetrate the cell membrane without any additives and exhibit high stability in cells. In this report, we employed a simple approach to address the basic properties of nanoparticles of oligonucleotides in biological systems. We prepared BODIPY-labeled oligonucleotides that carried an exclusive modi?cation at the strand end. BODIPY shows high hydrophobicity and ?uorescent emission; therefore, the oligonucleotides formed nanosized aggregates in aqueous solution and their behaviors in cells or tissues were easily revealed that aggregate formation was tracked. Detailed experiments indispensable for the oligonucleotides via scavenger-receptor-mediated endocytosis. In addition, the aggregates provided an e?cient gene regulation in living cells and tumor tissues transplanted into mice.
关键词： gene regulation,aggregate formation,BODIPY,cellular uptake,amphiphilic oligonucleotides
更新于2025-09-16 10:30:52