Strongly coupled dye aggregates with tailored exciton properties may find their use in developing artificial light-harvesting and optoelectronic devices. Here, we report the control of tubular pseudoisocyanine (PIC) dye J-and H-aggregate formation with tunable exciton fluorescence using lithocholic acid (LCA) as a template. The LCA-templated PIC Jaggregate nanotubes formed at a higher LCA/PIC molar ratio (≥5:1) exhibit a sharp, red-shifted absorption band (at 555 nm), intense fluorescence (at 565 nm), and shorter lifetime (200 ps), all indicating their strong superradiance properties. In contrast, the H-aggregate nanotubes formed at a lower LCA/PIC molar ratio (2:1) exhibit a significantly blue-shifted absorption band (at 420 nm) and highly red-shifted fluorescence emission (at 600 nm) with enhanced lifetime (4.40 ns). The controlled switching of the optical properties of the PIC dye aggregates achieved by controlling the LCA/PIC molar ratio could serve as an important guideline for the design of organic photo-functional materials.

Photoluminescent one-dimensional hybrid nanostructured materials having outstanding inorganic−organic advantages are gaining significant attention on account of their intriguing applications in nanoscale optoelectronic devices, (bio)sensors, and energy harvesting and conversion technologies. Here, we first report on the development of highly photoluminescent lanthanide organic hybrid nanotubular assemblies through in situ incorporation of a trivalent lanthanide ion, terbium (Tb 3+ ), along with organic photosensitizers 2,3-dihydroxynaphthalene (DHN) or 1,10-phenanthroline (Phen) into the self-assembled nanotubes of sodium lithocholate (NaLC). Both the photosensitizers (DHN/ Phen) are effective in sensitizing intense narrow emission peaks of Tb 3+ on the nanotubes. Next, we utilize these luminescent lanthanides containing hybrid nanotubular assemblies as templates for spontaneous integration of strongly coupled pseudoisocyanine (PIC) dye J-aggregates with a sharp J-band absorption at 555 nm and strong fluorescence emission at 570 nm. The presence of the significant spectral overlap between the luminescence peak of Tb 3+ at 545 nm and the J-aggregate absorption band results in efficient cascade energy transfer from photosensitizers to Tb 3+ to the coherently coupled PIC dye J-aggregates. These NaLC nanotube-templated photosensitizer-Tb 3+ -J-aggregate hybrid systems have great potential for sensing and optoelectronic applications.

Amyloid aggregation of protein is linked to many neurodegenerative diseases. Identification of small molecules capable of targeting amyloidogenic proteins has gained significant importance. Introduction of hydrophobic and hydrogen bonding interactions through site-specific binding of small molecular ligand to protein can effectively modulate the protein aggregation pathway. Here, we investigate the possible roles of three different bile acids, cholic acid (CA), taurocholic acid (TCA), and lithocholic acid (LCA) with varying hydrophobic and hydrogen bonding properties in inhibiting protein fibrillation. Bile acids are an important class of steroid compounds that are synthesized in the liver from cholesterol. Increasing evidence suggests that altered taurine transport, cholesterol metabolism, and bile acid synthesis have strong implications in Alzheimer’s disease. We find that the hydrophilic bile acids, CA and TCA (taurine conjugated form of CA), are substantially more efficient inhibitors of lysozyme fibrillation than the most hydrophobic secondary bile acid LCA. Although LCA binds more strongly with the protein and masks the Trp residues more prominently through hydrophobic interactions, the lesser extent of hydrogen bonding interactions at the active site has made LCA a relatively weaker inhibitor of HEWL aggregation than CA and TCA. The introduction of a greater number of hydrogen bonding channels by CA and TCA with several key amino acid residues which are prone to form oligomers and fibrils has weakened the protein’s internal hydrogen bonding capabilities for undergoing amyloid aggregation.

The formation of nanobiohybrids through the immobilization of enzymes on functional nanomaterials has opened up exciting research opportunities at the nanobiointerfaces. These systems hold great promise for a wide range of applications in biosensing, biocatalytic, and biomedical fields. Here, we report the formation of a hybrid nanobiocatalytic system through the adsorption of cytochrome c (Cyt c ) on pluronic triblock copolymer, P123 (PEO- b -PPO- b -PEO), stabilized MoS 2 nanosheets. The use of pluronic polymer has helped not only to greatly stabilize the exfoliated MoS 2 nanosheets but also to allow easy adsorption of Cyt c on the nanosheets without major structural changes due to its excellent biocompatibility and soft protein-binding property. By comparing the catalytic activity of the Cyt c –MoS 2 nanobiohybrid with that of the free Cyt c and as-prepared MoS 2 nanosheets, we have demonstrated the active role of the nanobiointeractions in enhancing the catalytic activity of the hybrid. Slight structural perturbation at the active site of the Cyt c upon adsorption on MoS 2 has primarily facilitated the peroxidase activity of the Cyt c . As the MoS 2 nanosheets and the native Cyt c individually exhibit weaker intrinsic peroxidase activities, their mutual modulation at the nanobiointerface has made the Cyt c –MoS 2 a novel nanobiocatalyst with superior activity.