Search for: All records

The forthcoming generation of materials, including artificial muscles, recyclable and healable systems, photochromic heterogeneous catalysts, or tailorable supercapacitors, relies on the fundamental concept of rapid switching between two or more discrete forms in the solid state. Herein, we report a breakthrough in the “speed limit” of photochromic molecules on the example of sterically-demanding spiropyran derivatives through their integration within solvent-free confined space, allowing for engineering of the photoresponsive moiety environment and tailoring their photoisomerization rates. The presented conceptual approach realized through construction of the spiropyran environment results in ~1000 times switching enhancement even in the solid state compared to its behavior in solution, setting a record in the field of photochromic compounds. Moreover, integration of two distinct photochromic moieties in the same framework provided access to a dynamic range of rates as well as complementary switching in the material’s optical profile, uncovering a previously inaccessible pathway for interstate rapid photoisomerization.

The authors designed a structurally stable nano‐in‐nano (NANO²) system highly capable of bioimaging via an aggregation‐enhanced NIR excited emission and photoacoustic response achieved based on atomically precise gold nanoclusters protected by linear thiolated ligands [Au₂₅(SC_nH_2n+1)₁₈,n =4–16] encapsulated in discoidal phospholipid bicelles through a one‐pot synthesis. The detailed morphological characterization of NANO²is conducted using cryogenic transmission electron microscopy, small/wide angle X‐ray scattering with the support of molecular dynamics simulations, providing information on the location of Au nanoclusters in NANO². The photoluminescence observed for NANO²is 20–60 times more intense than that of the free Au nanoclusters, with both excitation and emission wavelengths in the near‐infrared range, and the photoacoustic signal is more than tripled. The authors attribute this newly discovered aggregation‐enhanced photoluminescence and photoacoustic signals to the restriction of intramolecular motion of the clusters’ ligands. With the advantages of biocompatibility and high cellular uptake, NANO²is potentially applicable for both in vitro and in vivo imaging, as the authors demonstrate with NIR excited emission from in vitro A549 human lung and the KB human cervical cancer cells.

The dynamic behavior of a macroscopic adhered hydrogel stabilized through controllable dynamic covalent interactions is reported. These interactions, involving the cross‐linked formation of a hydrogel through reaction of a diacylhydrazine precursor with a tetraformyl partner, increase as a function of time. By using a contact time of 24 h and different compounds with recognized aggregation‐induced emission features (AIEgens), it proves possible to create six laminated acylhydrazone hydrogels displaying different fluorescent colors. Blocks of these hydrogels are then adhered into a structure resembling a Rubik's Cube, a trademark of Rubik's Brand Limited, (RC) and allowed to anneal for 1 h. This produces a 3 × 3 × 3 block (RC) wherein the individual fluorescent gel blocks are loosely adhered to one another. As a consequence, the 1 × 3 × 3 layers making up the RC can be rotated either horizontally or vertically to produce new patterns. Ex situ modification of the RC or application of a chemical stimulus can be used to produce new color arrangements. The present RC structure highlights how the temporal features, strong versus weak adhesion, may be exploited to create smart macroscopic structures.

Photocyclized intermediate formation and quasi CC twisting are the dominant processes behind the AIE.