pH-tunable phosphorescence and light harvesting in cucurbit[8]uril host-guest assemblies.

Host-guest assemblies of halo-phenyl pyridine derivatives and cucurbit[8]uril (CB[8]) exhibited pH-responsive room temperature phosphorescence (RTP) in aqueous media. Moreover, they acted as efficient light-harvesting systems demonstrating triplet-singlet energy transfer to various acceptor dyes.

Contrasting luminescence in heparin and DNA-templated co-assemblies of dimeric cyanostilbenes: efficient energy transfer in heparin-based co-assemblies.

Dimeric cationic cyanostilbenes with peripheral alkyl chains demonstrated aggregation in aqueous media depending on the length of the hydrophobic segment and produced luminescent spherical nano-assemblies in the case of long alkyl chain derivatives. In the presence of heparin, a bio-polyanion that is routinely used as an anticoagulant, the self-assembled structures obtained from the amphiphilic dimers showed the formation of higher-order structures whereas the non-assembling dimers exhibited heparin-induced supramolecular structure formation. In both cases, a significant enhancement in the emission was observed.

Efficient light harvesting in self-assembled organic luminescent nanotubes.

Luminescent organic nanotubes derived from the co-assembly of cyanostilbene (CS) based cationic supramolecular polymers and bio-polyanion heparin, a known anticoagulant, have been utilized as highly efficient FRET (fluorescence resonance energy transfer) donors in aqueous media resulting in amplified acceptor emission in the orange-red and near-infrared (NIR). Energy transfer efficiencies higher than 80% and an ultra-high antenna effect of 150 were achieved even at high donor/acceptor ratios (500 : 1-100 : 1) translating to emission quenching of several hundred donors by one acceptor. Utilizing the temperature responsiveness of the FRET process, these systems were employed as ratiometric emission thermometers in the temperature range 20-90 °C.

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

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.

Cucurbituril Based Luminescent Materials in Aqueous Media and Solid State.

Cucurbit[n]urils, the pumpkin shaped macrocyclic host molecules possessing a hydrophobic cavity and two identical carbonyl portals, have drawn a lot of attention in recent years due to their high-affinity yet dynamic molecular recognition properties in water. The reversible and stimuli-responsive nature of their host-guest complexes imparts "smart" features leading to materials with intriguing optical, mechanical and morphological properties. In this review, we focus on the design of cucurbituril based luminescent materials in aqueous media as well in solid or film state.

Highly sensitive and ratiometric luminescence sensing of heparin through templated cyanostilbene assemblies.

The assembly of organic dyes on bio-molecular templates is an attractive strategy for the creation of bio-materials with intriguing optical properties. This principle is exploited here for the detection of polyanion heparin, a known anticoagulant, by employing di-cationic cyanostilbene derivatives with inherent aggregation induced emission (AIE) features. The cyanostilbene derivatives exhibited weak cyan-blue monomeric emissions in solutions but upon electrostatic co-assembly with heparin, formed highly luminescent clusters on the polyanion surface.

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through "turn-on" fluorescence response.

Bisimidazolium receptors, tagged with chromophoric pyrene at one end and linked to an -alkyl chain at the other, underwent self-assembly in aqueous media depending on the length of the alkyl segment. The amphiphilic derivatives having -decyl or longer chains, formed nano-assemblies with cyanic-green emission resulting from the stacked pyrene chromophores in the aggregates. The presence of positive surface charges on the multivalent aggregates led to ATP binding which was accompanied by a significant increase in the excimeric emission intensity.

High affinity heparin detection by multivalent supramolecular polymers through aggregation induced emission.

Amphiphilic di-cationic cyanostilbene derivatives with aggregation induced emission (AIE) features formed luminescent supramolecular polymers in aqueous media. They bind bio-polyanion heparin, a known anticoagulant, in a multivalent fashion through the formation of co-assemblies with highly enhanced greenish-yellow emission. Heparin detection in nanomolar concentrations in buffer and in medically relevant concentrations in human serum and plasma was achieved.

Tunable multi-color luminescence from a self-assembled cyanostilbene and cucurbit[7]uril in aqueous media.

Amphiphilic cyanostilbene 12CS12 underwent self-assembly in aqueous media and exhibited bright greenish-yellow emission in its aggregated state. Macrocyclic host cucurbit[7]uril (CB[7]) was found to encapsulate 12CS12 and the host-guest complex was an efficient bluish-cyan emitter. Variation of the 12CS12 and CB[7] ratio in their mixture generated multiple emission colors including near white light through the color mixing of these two emitting species.