Light‐Triggered Self‐Assembly of a Spiropyran‐Functionalized Dendron into Nano‐/Micrometer‐Sized Particles and Photoresponsive Organogel with Switchable Fluorescence

Abstract

The synthesis, self‐assembly, and spectroscopic investigations of spiropyran (SP)‐functionalized dendron 1 are reported. Under UV light irradiation, assembly of 1 into nano‐/microparticles occurs due to the transformation of the closed form of SP into the open merocyanine (MC) form. The formation of these nano‐/microparticles is confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) experiments in addition to the confocal laser scanning microscopy (CLSM) measurements. These nano‐/microparticles exhibit relatively strong red emission. It is interesting to note that the direct cooling of the toluene/benzene solution of 1 to 0 °C leads to gel formation. Multivalent π–π interactions due to the dendron in 1 may be the driving‐force for the gelation. The UV light irradiation cannot destroy the gel phase, and in fact, the gel–gel transition is successfully realized. The purple‐blue gel exhibits relatively strong red fluorescence; moreover, the fluorescence can be reversibly switched by alternating UV and visible light irradiation. The results clearly indicate that the MC form after aggregation becomes more stable and fluorescent.

Digital holographic microscopy of spiropyran‐based dynamic materials

“…Comparing the fluorescence spectra of Figure 1d and i, the PMMA film shows also a greater and slightly wider fluorescence intensity than the PLA film. As it is clear in Figure 1e and j, after illuminating the sample by UV radiation, a new absorption peak around 575 nm is observed, a finding which is in good agreement with transformation of SP form to the merocyanine (MC) form 13 . By using an excitation wavelength of 400 nm, the fluorescence spectrum from the range of 410 to 750 nm is recorded for two polymeric samples (Figure 1d and i).…”

Digital Holographic Microscopy of Spiropyran-Based Dynamic Materials ​

“…As it is clear in Figs. 3(e) and (j), after illuminating the sample by UV radiation, a new absorption peak around 575 nm is observed, a finding which is in good agreement with transformation of SP form to the merocyanine (MC) form 13 . By using an excitation wavelength of 400 nm, the fluorescence spectrum from the range of 410 to 750 nm are recorded for two polymeric samples (Figs.…”

Synthesis and solution behavior of triple stimuli-responsive micellar and hybrid janus nanoparticles

“…58 The first mechanism is related to the shift of the equilibrium of SP to MC when solvents are exchanged. This behavior has been reported for spiropyrans and spirooxazines 59,60 and has been verified by the appearance of new bands or the redistribution of the intensities or bands of the absorption spectra. The second mechanism is based on the interactions between the solute and solvents of different polarity.…”