Supramolecular One-Dimensional n/p-Nanofibers

An Ultra-Long-Lived Triplet Excited State in Water at Room Temperature: Insights on the Molecular Design of Tridecafullerenes

Suitably engineered molecular systems exhibiting triplet excited states with very long lifetimes are important for high-end applications in nonlinear optics, photocatalysis, or biomedicine. We report the finding of an ultra-long-lived triplet state with a mean lifetime of 93 ms in an aqueous phase at room temperature, measured for a globular tridecafullerene with a highly compact glycodendrimeric structure. A series of three tridecafullerenes bearing different glycodendrons and spacers to the C60 units have been synthesized and characterized. UV/Vis spectra and DLS experiments confirm their aggregation in water. Steady-state and time-resolved fluorescence experiments suggest a different degree of inner solvation of the multifullerenes depending on their molecular design. Efficient quenching of the triplet states by O2 but not by waterborne azide anions has been observed. Molecular modelling reveals dissimilar access of the aqueous phase to the internal structure of the tridecafullerenes, differently shielded by the glycodendrimeric shell.

Protein-directed crystalline 2D fullerene assemblies

Water soluble 2D crystalline monolayers of fullerenes grow on planar assemblies of engineered consensus tetratricopeptide repeat proteins. Designed fullerene-coordinating tyrosine clamps on the protein introduce specific fullerene binding sites, which facilitate fullerene nucleation. Through reciprocal interactions between the components, the hybrid material assembles into two-dimensional 2 nm thick structures with crystalline order, that conduct photo-generated charges. Thus, the protein-fullerene hybrid material is a demonstration of the developments toward functional materials with protein-based precision control of functional elements.

Programmed Hierarchical Hybrid Nanostructures from Fullerene-Dendrons and Pyrene-Dendrons

The construction of fullerene (C₆₀ ) hierarchical nanostructures with the help of amphiphilic molecules remains a challenging task in nanoscience and nanotechnology. Utilizing the host-guest complex concept, sub-10 nm layered superstructures are constructed from a monofunctionalized C₆₀ dendron (C₆₀ D, guest) and tweezer-like pyrene dendron (PD, host). Since C₆₀ D and PD are asymmetric shape amphiphiles having liquid crystal (LC) dendrons, both C₆₀ D and PD construct head-to-head bilayer superstructures by themselves. From fluorescence titration experiments, it is realized that the host-guest complex shows 1:1 stoichiometric binding with a binding constant (K_sv = 2.45 × 10⁵ m^-1 ). Based on the morphological observations and scattering analyses, it is found that buckle-like asymmetric building blocks (C₆₀ D·PD) are self-assembled by the host-guest complex and construct multilayer hybrid nanostructures. The hierarchical hybrid nanostructures consist of the self-assembled C₆₀ D·PD bilayer with a 2D C₆₀ ·P nanoarray sandwiched between LC dendrons. This advanced strategy is expected to be a practicable and rational guideline for the fabrication of programmed hierarchical hybrid nanostructures.

Fullerene Cluster Assisted Self-Assembly of Short DNA Strands into Semiconducting Nanowires

Programmable, hierarchical assembly of DNA nanostructures with precise organisation of functional components have been demonstrated previously with tiled assembly and DNA origami. However, building organised nanostructures with random oligonucleotide strands remains as an elusive problem. Herein, a simple and general strategy, in which nanoclusters of a fullerene derivative act as stapler motifs in bringing ordered nanoscale assembly of short oligonucleotide duplexes into micrometre-sized nanowires, is described. In this approach, the fullerene derivative, by virtue of its amphiphilic structure and unique hydrophobic-hydrophilic balance, pre-assembles to form 3-5 nm sized clusters in a mixture of DMSO-phosphate buffer, which further assists the assembly of DNA strands. The optimum cluster size, availability of DNA anchoring motifs and the nature of the DNA strands controls the structure of these nanomaterials. Furthermore, horizontal conductivity measurements through conductive AFM confirmed the charge transport properties of these nanowires. The current strategy could be employed to organise random DNA duplexes and tiles into functional nanostructures, and hence, open up new avenues in DNA nanotechnology.

A π-gel scaffold for assembling fullerene to photoconducting supramolecular rods

Nonequilibrium self-assembly of molecules holds a huge prospect as a tool for obtaining new-generation materials for future applications. Crystallization of neutral molecules within a supramolecular gel matrix is one example in which two nonequilibrium processes occur orthogonal to each other. On the other hand, electronically interacting donor-acceptor two-component systems are expected to form phase-miscible hybrid systems. Contrary to the expectation, we report the behavior of a π-gel, derived from oligo(p-phenylenevinylene), OPVA, as a scaffold for the phase separation and crystallization of fullerene (C₆₀) to supramolecular rods with increased transient photoconductivity (φƩμ_max = 2.4 × 10^-4 cm² V^-1 s^-1). The C₆₀ supramolecular rods in the π-gel medium exhibited high photocurrent in comparison to C₆₀ loaded in a non-π-gel medium. This finding provides an opportunity for large-scale preparation of micrometer-sized photoconducting rods of fullerenes for device application.