Heating and cooling can induce reversible solid‐to‐liquid transitions of matter. In contrast, athermal photochemical processes can induce reversible solid‐to‐liquid transitions of some newly developed azobenzene compounds. Azobenzene is photoswitchable. UV light induces trans‐to‐cis isomerization; visible light or heat induces cis‐to‐trans isomerization. Trans and cis isomers usually have different melting points (Tm) or glass transition temperatures (Tg). If Tm or Tg of an azobenzene compound in trans and cis forms are above and below room temperature, respectively, light may induce reversible solid‐to‐liquid transitions. In this Review, we introduce azobenzene compounds that exhibit photoinduced reversible solid‐to‐liquid transitions, discuss the mechanisms and design principles, and show their potential applications in healable coatings, adhesives, transfer printing, lithography, actuators, fuels, and gas separation. Finally, we discuss remaining challenges in this field.
We have demonstrated an interesting approach for the one-pot synthesis of cupric oxide (CuO) nanourchins with sub-100 nm through a sequential dissolution-precipitation process in a water/ethanol system. The first stage produces a precursory crystal [Cu7Cl4(OH)10H2O] that is transformed into monoclinic CuO nanourchins during the following stage. Water is a required reactant for the morphology-controlled growth of different CuO nanostructures. When evaluated for their nonenzymatic glucose-sensing properties, these CuO nanourchins manifest higher sensitivity. Significantly, this water-dependent precursor transformation method may be widely used to effectively control the growth of other metal oxide nanostructures.
For the first time, a facile, one-pot water/ethanol solution-phase transformation of Cu2(NO3)(OH)3 precursors into bicomponent CuO hierarchical nanoflowers is demonstrated by a sequential in situ dissolution-precipitation formation mechanism. The first stage produces a precursory crystal (monoclinic Cu2(NO3)(OH)3) that is transformed into monoclinic CuO nanoflowers during the following stage. Water is a required reactant, and the morphology-controlled growth of CuO nanostructures can be readily achieved by adjusting the volume ratio between water and ethanol. Such a bicomponent CuO hierarchical nanoflower serving as a promising electrode material for a nonenzymatic glucose biosensor shows higher sensitivity and excellent selectivity. The findings reveal that the different Cu(x)M(y)(OH)(z) (M = acidic radical) precursors synthesized in a water/ethanol reaction environment can be utilized to obtain new forms of CuO nanomaterials, and this unique water-dependent precursor-transformation method may be used to effectively control the growth of other metal oxide nanostructures.
Photoresponsive polymers with multi-azobenzene groups are reviewed and their potential applications in photoactuation, photo-patterning, and photoinduced birefringence are introduced.
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