Aligned 1-D Nanorods of a π-Gelator Exhibit Molecular Orientation and Excitation Energy Transport Different from Entangled Fiber Networks

Theoretical studies of molecular orientation and charge recombination in poly-paraphenylenevinylene light-emitting diodes

Poly-paraphenylenevinylene (PPV), a material used in organic light-emitting diodes (OLEDs), for which improving the efficiency is an important issue. In general, the molecular orientations of organic compounds in the crystal form are an essential factor determining electron and hole transfer, which are closely related to the efficiency of OLEDs. We have investigated the effects of the rotation of each molecule and the intermolecular distance in the dimer system of PPV, which consists of donor and acceptor molecules, on its charge-recombination process by performing constrained density functional calculations. Starting from the structure of the crystal, it was clarified that the rotation of the donor decreases the charge-recombination factor, to nearly zero, while that of the acceptor increases it to about 10(6) s(-1). We found that this is caused by the repulsive interaction between the donor and acceptor molecules and the formation of a transport pathway resulting from the acceptor rotation.

Vortex-aligned fullerene nanowhiskers as a scaffold for orienting cell growth

A versatile method for the rapid fabrication of aligned fullerene C60 nanowhiskers (C60NWs) at the air-water interface is presented. This method is based on the vortex motion of a subphase (water), which directs floating C60NWs to align on the water surface according to the direction of rotational flow. Aligned C60NWs could be transferred onto many different flat substrates, and, in this case, aligned C60NWs on glass substrates were employed as a scaffold for cell culture. Bone forming human osteoblast MG63 cells adhered well to the C60NWs, and their growth was found to be oriented with the axis of the aligned C60NWs. Cells grown on aligned C60NWs were more highly oriented with the axis of alignment than when grown on randomly oriented nanowhiskers. A study of cell proliferation on the C60NWs revealed their low toxicity, indicating their potential for use in biomedical applications.

Synthesis of Peptide-Based Hybrid Nanobelts with Enhanced Color Emission by Heat Treatment or Water Induction

We demonstrate that an inorganic lanthanide ion (Tb(3+)) or organic dye molecules were encapsulated in situ into diphenylalanine (FF) organogels by a general, simple, and efficient co-assembly process, which generated peptide-based hybrid nanobelts with a range of colored emissions. In the presence of a photosensitizer (salicylic acid), the organogel can serve as an excellent molecular-donor scaffold to investigate FRET to Tb(3+). More importantly, heat treatment or water induction instigated a morphology transition from nanofibers to nanobelts, after which the participation of guest molecules in the FF assembly was promoted and the stability and photoluminescence emission of the composite organogels were enhanced.

Tuning soft nanostructures in self-assembled supramolecular gels: from morphology control to morphology-dependent functions

Supramolecular gels are one kind of important soft material, in which small low-molecular weight compounds self-assemble into various nanostructures through non-covalent interactions to immobilize the solvents. While there are many important fundamental issues related to the gelation process, such as the design of the gelator, synergism of various non-covalent interactions between gelators, gelator-solvents, the balances between gelation and crystallization and so on, the self-assembled nanostructures forming during gelation are very interesting. These nanostructures have many unique features, such as the flexibility to respond to external stimuli, morphological diversity, ease of fabrication in large quantities, and so on. This review highlights some important features in tuning the nanostructures in the supramolecular gels from their morphological diversity, morphology control, morphology conversion, and morphology-depended functions.

Energy transfer within responsive pi-conjugated coassembled peptide-based nanostructures in aqueous environments

Steady-state and time-resolved photophysical measurements demonstrate energy transfer within π-conjugated peptide nanostructures composed of oligo-(p-phenylenevinylene)-based donor units and quaterthiophene-based acceptor units in completely aqueous environments. These peptide-based assemblies encourage energy migration along the stacking axis, thus resulting in the quenching of donor emission peaks along with the development of new spectral features reminiscent of acceptor emission. These spectral changes were observed even at minute amounts of the acceptor (starting at 1 mol%), suggesting that exciton migration is involved in energy transport and supporting a funnel-like energy transduction mechanism. The reversibility of nanostructure formation and the associated photophysical responses under different conditions (pH, temperature) were also studied. This unique material design incorporates two different semiconducting units coassembled within peptide nanostructures and offers a new platform for the engineering of energy migration through bioelectronic materials in aqueous environments.

Synthesis and structural analysis of tungsten-carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through pyridine coordination

Synthesis, structural analysis and basic optical properties of tungsten carbonyl dimers bridged with oligo(2,5-dialkoxy-1,4-phenylene vinylene)s through coordination with pyridine have been explored.

A “keto–enol tautomerization”-based response mechanism: a novel approach to stimuli-responsive supramolecular gel

By “keto–enol tautomerization”, gelator G3 can be self-assembled into a stable organogel (OG3) accompanied by strong aggregation induced emission (AIE). OG3 could dual-channel sense S²⁻ with specific selectivity via reversible sol–gel transition and fluorescent changes.

π-Conjugated polymer anisotropic organogel nanofibrous assemblies for thermoresponsive photonic switches

The present work demonstrates one of the first examples of π-conjugated photonic switches (or photonic wave plates) based on the tailor-made π-conjugated polymer anisotropic organogel. New semicrystalline segmented π-conjugated polymers are designed with rigid aromatic oligophenylenevinylene π-core and flexible alkyl chain along the polymer backbone. These polymers are found to be self-assembled as semicrystalline or amorphous with respect to the number of carbon atoms in the alkyl units. These semicrystalline polymers produce organogels having nanofibrous morphology of 20 nm thickness with length up to 5 μm. The polymer organogel is aligned in a narrow glass capillary, and this anisotropic gel device is further demonstrated as photonic switches. The glass capillary device behaves as typical λ/4 photonic wave plates upon the illumination of the plane polarized light. The λ/4 photonic switching ability is found to be maximum at θ = 45° angle under the cross polarizers. The orthogonal arrangements of the gel capillaries produce dark and bright spots as on-and-off optical switches. Thermoreversibility of the polymer organogel (also its xerogel) was exploited to construct thermoresponsive photonic switches for the temperature window starting from 25 to 160 °C. The organic photonic switch concept can be adapted to large number of other π-conjugated materials for optical communication and storage.

Experimental Conditions to Obtain Photopolymerization Induced Phase Separation Process in Liquid Crystal-Photopolymer Composite Materials under Laser Exposure

We analyze the experimental conditions necessary to obtain a photopolymerization induced phase separation process inside liquid crystal-photopolymer composite materials. Composites stored for 24 hours perform poorly in hologram recording but a good result is obtained if they are used recently prepared. We use a procedure combining heat and sonication to disarrange the liquid crystal structures formed during storage of the composite. We also propose incoherent light treatment after recording the hologram in order to evaluate if the phase separation evolved correctly during hologram recording.

A self-assembled π-conjugated system as an anti-proliferative agent in prostate cancer cells and a probe for intra-cellular imaging

Herein, self-assembled π-conjugated systems derived from renewable resource are reported as a probe for intra-cellular imaging and an anti-proliferative agent for PC3 cells.

Micrometer long oriented one-dimensional wires and two-dimensional sheets from a bis-urea functionalized dialkoxynaphthalene organogelator

Fabrication of 1D wires and 2D sheets of organogelator DAN-U at an air–water interface below the critical gelation concentration is reported here.