Benzene is the simplest aromatic hydrocarbon with a six-membered ring. It is one of the most basic structural units for the construction of π conjugated systems, which are widely used as fluorescent dyes and other luminescent materials for imaging applications and displays because of their enhanced spectroscopic signal. Presented herein is 2,5-bis(methylsulfonyl)-1,4-diaminobenzene as a novel architecture for green fluorophores, established based on an effective push-pull system supported by intramolecular hydrogen bonding. This compound demonstrates high fluorescence emission and photostability and is solid-state emissive, water-soluble, and solvent- and pH-independent with quantum yields of Φ=0.67 and Stokes shift of 140 nm (in water). This architecture is a significant departure from conventional extended π-conjugated systems based on a flat and rigid molecular design and provides a minimum requirement for green fluorophores comprising a single benzene ring.

Most targeting strategies of anticancer drug delivery systems (DDSs) rely on the surface functionalization of nanocarriers with specific ligands, which trigger the internalization in cancer cells via receptor-mediated endocytosis. The endocytosis implies the entrapment of DDSs in acidic vesicles (endosomes and lysosomes) and their eventual ejection by exocytosis. This process, intrinsic to eukaryotic cells, is one of the main drawbacks of DDSs because it reduces the drug bioavailability in the intracellular environment. The escape of DDSs from the acidic vesicles is, therefore, crucial to enhance the therapeutic performance at low drug dose. To this end, we developed a multifunctionalized DDS that combines high specificity towards cancer cells with endosomal escape capabilities. Doxorubicin-loaded mesoporous silica nanoparticles were functionalized with polyethylenimine, a polymer commonly used to induce endosomal rupture, and hyaluronic acid, which binds to CD44 receptors, overexpressed in cancer cells. We show irrefutable proof that the developed DDS can escape the endosomal pathway upon polymeric functionalization. Interestingly, the combination of the two polymers resulted in higher endosomal escape efficiency than the polyethylenimine coating alone. Hyaluronic acid additionally provides the system with cancer targeting capability and enzymatically controlled drug release. Thanks to this multifunctionality, the engineered DDS had cytotoxicity comparable to the pure drug whilst displaying high specificity towards cancer cells. The polymeric engineering here developed enhances the performance of DDS at low drug dose, holding great potential for anticancer therapeutic applications.

The preparation of fullerene fine crystals with uniform size and shape would permit the control of their specific electronic energy levels and the fabrication of materials with completely new properties. To this end, we have successfully fabricated, for the first time, shape-and sizecontrolled C 60 fine crystals using a reprecipitation method developed in our laboratory. The C 60 fine crystals obtained were clearly monodisperse and came in an interesting diversity of shapes such as spherical, rodlike, fibrous, disk, and octahedral. We were able to selectively control these sizes and shapes by simply changing the combination of solvents used and the reprecipitation conditions.

We have fabricated well-defined nanostructures such as SiO2-coated Ag nanoparticles (NPs) connected with quantum dots (QDs) (Ag/SiO2-QDs) so as to control the fluorescence enhancement induced by localized surface plasmon resonance. Namely, the distance between Ag NP and QD should be noted as a controllable model to investigate the fluorescence enhancement effect. Actually, highly monodispersed Ag NP as a core was first coated with five thicknesses of SiO2 as a shell, and then QDs were specifically adsorbed onto the surface of the amino-functionalized SiO2-coated Ag NPs. As a result, the fluorescence intensity increased with the shell thickness as a result of excitation enhancement. On the other hand, the fluorescence intensity decreased when the shell thickness became thinner because of the induced quenching. Therefore, the distance between Ag NPs and QDs should be optimized to control and enhance the fluorescence intensity.

Photoinduced charge separation and recombination processes in fine particles of octathiophene-C 60 and dodecathiophene-C 60 dyad molecules were investigated by the subpicosecond laser photolysis method. Sizes of the fine particle samples were estimated to be 60-140 nm using SEM observation and dynamic light scattering measurements. Charge separated states were generated within 1 ps upon the 150 fs laser excitation in both fine particle samples of the dyad molecules. Generation yields of the charge separated states were about a half of those of the corresponding dyad molecules in polar solvents, indicating the existence of the competitive deactivation pathways of the singlet excited states, such as exciton migration in each fine particle. On the other hand, the charge separated states deactivated via the two-step-decay processes. Direct charge recombination in a dyad molecule and indirect charge recombination after migration of radical cation (hole) and anion (electron) in fine particles were observed as fast and slow decay components, respectively. The faster charge recombination rates than those of previously reported for aniline-fullerene dyad cluster will result from high hole-mobility in the oligothiophene-moieties of the present dyad molecules composing fine particles.