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Long-term creative approaches have been considered in the design of molecular probes to overcome the quenching effect of important dyes in an aqueous medium. Using the rational donor–acceptor based design principle, we demonstrate herein the different fluorescence states of a non-conjugated symmetrical perylene-azacrown ether system in a solution, from the molecular to the aggregated states. The ethylene-spacer is exceptionally capable of fluorescence enhancement, even in the aggregated state (organic nanoparticle, ONPs, 44 nm), overcoming the quenching effect on changing the solvent from tetrahydrofuran to water. The ONPs with crown ether receptors at the surface show colloidal stability in an aqueous solution. Furthermore, an improved fluorescent state is developed via ONPs–polymer (protamine, Pro) hybridization. Supramolecular interactions between the crown ring and the guanidinium group in Pro play an important role in the ONPs–Pro hybrid formation. The decorated fluorescent hybrid state is finally used as a nano-probe for sensing heparin via the turn-OFF mechanism. The decoration method is further generalized by recognition of the nucleotides. Herein, we detail the bottom-up approach to the molecular design and development of the different fluorescent states of a useful probe. Most excitingly, this new approach is very general and adaptive to facile detection. [ABSTRACT FROM AUTHOR]

Recognition directed spontaneous assembly formation has been used to build-up a sensory system with perylene bis-guanidinium (PBG), which presented great response towards chiral guest sensing. Based on structural modification in the chiral guest molecules, PBG can selectively recognize dibenzoyl tartaric acid (DBTA) among the other tartaric acids (TA), resulting in an explicit read-out of molecular information via the generation of characteristic induced circular dichroism spectra for the d- and l-enantiomers. The binding ability depends only on the substituents in the TA and the local guidance plays an important role in structure formation. The bulky substituents in TA can lead to induced chirality in the cofacial perylene stacks by generating an active angle between the successive transition dipoles. The induced helical sense was found to exhibit efficient chiral amplification with a sigmoidal change (i.e. according to a sergeants-and-soldiers effect) in the enantiomeric excess plot. The diversity in physical properties was further examined by the preparative method. Compared to the simple mixing method, the heating–cooling method is able to show aggregation induced fluorescence enhancement, which was used to fabricate highly efficient fluorescent solid in a supramolecular manner from a perylene-based dye. [ABSTRACT FROM AUTHOR]

Herein, we report the in situ transmission electron microscopy observation of the deformation and fracture processes of an epoxy resin thin film containing silica nanoparticles under tensile strain. Under tensile strain, the dispersed silica nanoparticles in the composite arrest the progress of the crack tip and prevent crack propagation. Concomitantly, the generation and growth of nanovoids at the epoxy matrix/nanoparticle interfaces were clearly observed, particularly in the region near the crack tip. These nanovoids contribute to the dissipation of fracture energy, thereby enhancing the fracture toughness. We also analyzed the local distributions of the true strain and strain rate in the nanocomposite film during tensile testing using the digital image correlation method. In the region around the crack tip, the strain rate increased by 3 to 10 times compared to the average of the entire test specimen. However, the presence of large filler particles in the growing crack suppressed the generation of strain, potentially contributing to hindering crack growth.

A combination of cobalt(II) complexes and pyridine ligands carrying organic spins, aminoxyl and carbene, provided single-molecule magnets with Stotal = 3/2 in diluted frozen solutions.