In photoswitches that undergo fluorescence switching upon ultraviolet irradiation, photoluminescence and photoisomerization often occur simultaneously, leading to unstable fluorescence properties. Here, we successfully demonstrated reversible solid-state triple fluorescence switching through "Pump-Trigger" multiphoton manipulation. A novel fluorescence photoswitch, BOSA-SP, achieved green, yellow, and red fluorescence under excitation by pump light and isomerization induced by trigger light. The energy ranges of photoexcitation and photoisomerization did not overlap, enabling appropriate selection of the multiphoton light for "pump" and "trigger" photoswitching, respectively. Additionally, the large free volume of the spiropyran (SP) moiety in the solid state promoted reversible photoisomerization. Switching between "pump" and "trigger" light is useful for three-color tunable switching cell imaging, which can be exploited in programmable fluorescence switching. Furthermore, we exploited reversible dual-fluorescence switching in a single molecular system to successfully achieve two-color superresolution imaging.
Monodisperse polymer hemispheres
have been fabricated by seed emulsion
polymerization of isobutyl methacrylate (iBMA) and acrylic acid (AA)
using linear polystyrene (PSt) colloids as seeds, followed by the
selected washing of alcohol/water. The morphological investigation
performed by scanning electron microscopy (SEM) and transmission electron
microscopy (TEM) indicates that polymer colloids are monodisperse
round spheres and hemispheres before and after postpolymerization
ethanol washing, respectively. Fluorescent microscopy demonstrates
that the polymer colloids consist of hydrophobic cores and hydrophilic
surfaces. Super-resolution imaging reveals that the thickness of the
hydrophilic surface layer in polymer colloids is below 100 nm. The
seed emulsion polymerization process was characterized by a fluorescent
spectrophotometer and fluorescent microscopy based on the aggregation-induced
emission (AIE) mechanism. The fluorescent intensity of AIE-active
probes in polymer colloids increases as of emulsion polymerization
proceeds. During seed emulsion polymerization, it is observed in the
SEM images that polymer colloids are isotropic round spheres. Under
a fluorescent microscope, however, one half of each polymer colloid
shows much stronger fluorescence than the other half, which indicates
that the microphase separation inside each polymer colloid occurs,
causing anisotropic distribution of the chemical composition. It is
of particular interest that the postpolymerization washing process
determines the final shape of the polymer colloids. After the ethanol/water
washing process to partially dissolve the hydrophilic polymers, the
round polymer colloids are compressed into uniform anisotropic hemispheres
as a result of the asymmetric distribution of the chemical composition
in polymer colloids, which provides a promising alternative to prepare
novel topological polymer colloids.
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