Shuzhang Xiao

Amphiphilic diarylethene as a photoswitchable probe for imaging living cells.

This communication reports a unique example of water-soluble and fluorescent-switchable amphiphilic diarylethene. This compound performs stable vesicle aggregation in water and shows aggregation-dependent emission in its open form. The fluorescence can be effectively switched by alternating between UV and visible light irradiation. This compound thus can stain KB cells for switchable living cell imaging with excellent resistance to fatigue.

Hydrogen bonding assisted switchable fluorescence in self-assembled complexes containing diarylethene: controllable fluorescent emission in the solid state

Switchable supramolecular self-assemblies based on the interaction between pyridine group containing diarylethene unit (BTEPy) and carboxylic acids were designed and fabricated in this report. Fluorescent enhancement was observed in all of these assembled systems not only in solution, but also in the solid state as well as in the nanoparticles. A clear red-shift emerged in the solid film of the assembled system with BTEPy as a single fluorophore. Fluorescent photochromic organic nanoparticles were also realized in this system. When BTEPy interacted with a proton donor containing a BODIPY dye, the “concentration quenching” problem in the solid state was alleviated due to the hydrogen bond formation and an energy transfer process, with a 65 nm blue shift of the fluorescence. The solid state fluorescence of all these assemblies was effectively switched by alternating irradiation with UV and visible light. Moreover, with the separate wavelengths of writing, reading and erasing cycles in the BODIPY system, control of the fluorescence intensity in a reversible manner without causing destruction in readout capability was realized. The formation of hydrogen bonds between the pyridine group and carboxylic acids of these components was verified by FT-IR, XPS and 1H NMR.

Stabilization of the mesomorphic phase in a self-assembled two-component system

We reported here the two-component self-assembling building blocks capable of forming lyotropic liquid crystal and liquid-crystalline physical gel. One of the components has a molecular characteristic of C(3)-symmetrical trisureas containing three azobenzene groups, which can form liquid-crystal phase in a temperature range of 133-215 degrees C. Another one has a trisamide core, which can self-aggregate to fibrous network through hydrogen bonds of amide moieties. The mixture of these two components performs lyotropic liquid crystal as well as liquid-crystalline physical gel in a temperature range larger than that of sole compound, suggesting that the cooperation of hydrogen bonds between these components stabilizes the mesophase of the assembly. The mechanism of formation of the mesophase was investigated by infrared spectra and small-angle X-ray scatterings.