Fluorescence visualization of the molecular assembly processes during solvent evaporation via aggregation-induced emission in a cyanostilbene derivative

Abstract

Initial stage of organic crystal formation during solvent evaporation was observed by using aggregation-induced enhanced emission, indicating fluorescence from J-aggregates was established prior to the increase in total intensity at 10 assembly process, which suggested that the kinetics of the transformation of J-aggregates into embryonic nuclei, and subsequently to crystal can be visualized by the fluorescence.Organic molecular materials have wide applications in electroluminescence, solar cells, and pharmaceutical products. 1, 2 15Intermolecular interactions are significant factors for the development of higher functionality in these applications. To optimize the interactions, it is necessary to understand molecular packing or polymorphism during crystal growth, including nuclei formation.3-5 To clarify crystal growth, there has been widely 20 studied by X-ray crystallography, infrared spectroscopy, nuclear magnetic resonance, and transmission electron microscopy 6 . 4Many organic molecules exhibit characteristic spectral changes that depend on their electronic states, how they assemble, their size, and their ambient environment. [7][8][9] In principle, fluorescence 25 spectroscopy can be used to probe the progress of molecular assembly on the scale of just a few molecules or that of a bulk process. Previously, we proposed that concentration-dependent changes in fluorescence spectra for pyrene 10 from Aldrich and used as received. CN-MBE-doped PMMA thin films with a PMMA concentration fixed at 2 wt% were prepared by drop-casting DCE solutions onto glass cover slips. Fluorescence spectra were recorded with a Shimadzu RF-5300PC fluorescence spectrophotometer. Droplet with 10 µL fluorescence 60 color and intensity, as well as the morphology of the crystals, were captured with an inverted fluorescence microscope (Olympus IX71), equipped with a UPlanFl 4×/0.13 PhL (Olympus) objective lens, a CCD camera (Sigma Koki SK-TC202USB-AT), and a USB 4000 (Ocean Optics) spectrometer, 65 which was not corrected for the wavelength dependence of the detectors. All experiments were performed at room temperature. spectra from 330-nm excitation of these films cast from DCE solutions. At concentrations <0.1 mol%, peak emission was observed at 440 nm, with a shoulder at 420−430 nm. At increased concentrations, the fluorescence peak shifts to 470 nm and narrows. Aggregate species were observed with the fluorescence 80 microscope at concentrations >1.0 mol% (Fig. ESI 1). Thus the spectral shift and narrowing of the fluorescence originated from CN-MBE J-aggregates. 15 To identify the emissive species at lower concentrations, excitation spectra of the CN-MBE/PMMA films were acquired (Fig. ESI 2), indicating the broad excitation 85 spectra at 355 nm for concentrations <0.1 mol% is most likely a

Facile fabrication of luminescent organic dots by thermolysis of citric acid in urea melt, and their use for cell staining and polyelectrolyte microcapsule labelling

“…During the formation of the O-dots, the distance between fluorophores decreases, and this should lead to some autoquenching. Earlier, a similar bathochromic shift in the emission spectra of monomeric fluorophores upon condensation in a polymer matrix was registered by Ito et al for perylene [44], a dibenzoylmethane boron complex [45] and a cyanostilbene derivative [46]. The latter paper also reported that the quantum yield of monomer fluorescence was higher than that of the aggregates.…”

Use of Aggregation‐Induced Emission for Selective Detection of Phase Transformation during Evaporative Crystallization of Hexaphenylsilole

“…In the present system, selective detection of the aggregated state is achieved by making use of the AIE phenomenon. As reported for the CN‐MBE system, temporal changes in the integrated fluorescence intensities are plotted in Figure c. The total fluorescence intensity increased significantly and monotonically after 60 s, and became constant after 180 s. The total fluorescence intensity can be dependent on the amount of HPS aggregates, amorphous and crystals, implying that changes in the fluorescence spectra and fluorescence intensity reflect the formation of aggregates.…”

“…Interaction with, or binding to, the amyloid fibril results in fluorescence enhancement; thus, ThT is a powerful tool for studying the kinetics of fibril formation. We have reported the aggregation dynamics corresponding to CN‐MBE crystal formation . A sigmoidal function can be used to obtain an estimate of the time required for the aggregation to level off: …”

Aggregation‐Induced Emission for Visualization in Materials Science

“…Excitingly, it has been reported that AIE molecules exhibit diverse behaviors in different solvents as a result of the variously restricted molecular motions. Based on these facts, the dynamic visualization of the evaporation process have been studied by using AIE molecules . Firstly, the fluorescent behaviors of AIE molecules in the presence of different water fractions in tetrahydrofuran (THF)/water mixtures have been studied.…”

“…Based on these facts, the dynamic visualization of the evaporation process have been studied by using AIE molecules. [63] Firstly,t he fluorescent behaviors of AIE moleculesi nt he presence of different water fractionsi n tetrahydrofuran (THF)/water mixturesh ave been studied. Ac alibration curve was drawn to show the monotonically increasing fluorescent intensity with increasing water fractions in the mixed solvents.…”