Multicolor-Luminescence Including White Light by Photomodulation of Supramolecular Assemblies in Aqueous Media

Abstract

Photo-responsive supramolecular systems offer intriguing functional aspects which have led to their applications in diverse fields such as optoelectronics and biomedicine. However, the modulation of the luminescence output in a spatiotemporal fashion by photo-controlled transformation still remains a challenging task. Herein, we report the controlled regulation of the emission color of supramolecular assemblies of amphiphilic cyanostilbenes (CSs) in water through in situ photomodulation employing UV and sunlight. Due to their aggregation-induced emission (AIE) features, the CS chromophores in the supramolecular assemblies exhibited bright greenish-yellow emission. Photoirradiation predominantly led to the formation of a cyclized product exhibiting aggregation-caused quenching (ACQ) features and having efficient cyan-blue emission in water but severely quenched emission in the solid state. Hence, starting from a unicomponent scaffold, photomodulation provided tunable emission ranging from greenish-yellow to cyan-blue including white light in water. Furthermore, using the contrasting AIE and ACQ behavior of the components in the photoirradiated mixtures, we were able to design rewritable fluorescent inks and encryption in solid films indicating the practical utility of these systems.

Efficient energy transfer in heparin-based co-assemblies of donor–acceptor cyanostilbenes

“…1). Such weak emission is characteristic of monomeric cyanostilbenes 24,25,30,31 and this was further supported by the lifetime data (Table S1, ESI†). The large Stokes shifts (∼198 nm) suggested a twisted intramolecular charge transfer (TICT) emission character of these pre-twisted molecules.…”

“…Presumably, the shorter lifetime component resulted from the TICT states 35,36 of these pre-twisted CS molecules. 30,31 On the other hand, the component with the longer lifetime can be attributed to the excimeric emission. 37 Classical TICT molecules such as (dimethylamino)benzonitrile is known to exhibit excimeric emission in its dimeric state.…”

Efficient light harvesting in self-assembled organic luminescent nanotubes

“…1) was earlier reported by us. [43][44][45]53 We have shown previously that in aqueous buffer, 12CS12 and 10CS10 (Fig. 1) aggregated signicantly at low micromolar concentrations to produce supramolecular polymeric nanobers (referred as SP10 and SP12, respectively).…”

“…1) aggregated signicantly at low micromolar concentrations to produce supramolecular polymeric nanobers (referred as SP10 and SP12, respectively). [43][44][45] Their aggregation was characterized by the appearance of greenish-yellow excimeric emission (average lifetime: 4.3-6.97 ns) at 540-545 nm (Fig. S1a and b, ESI ‡) and this excimeric emission was not observed in the derivatives with n-hexyl or lower chain lengths.…”

“…1, right panel). [43][44][45] This provided a sensitive and selective method for the detection of the polyanion in aqueous buffer, serum, and plasma. 44 Cyanostilbenes (CSs) are known for their enhanced emission properties in the aggregated state (AIE: aggregationinduced emission) and have been employed in functional materials including luminescent assemblies, optoelectronic materials, and bioimaging probes.…”