Electrostatic Self-Assembly of Polydiacetylene Nanocrystals: Nonlinear Optical Properties and Chain Orientation

An eco-friendly synthesis of novel 3,5-disubstituted-1,2-isoxazoles in PEG-400, employing the Et3N-promoted hydroamination of symmetric and unsymmetric 1,3-diyne-indole derivatives

PEG-400 proved to be a useful solvent for the mild and efficient synthesis of 3,5-disubstituted 1,2-isoxazoles derived from 1,3-diyne indoles. The scope and limitations of the reaction were also studied.

Polydiacetylenes: supramolecular smart materials with a structural hierarchy for sensing, imaging and display applications

While a large variety of conjugated polymers exist, polydiacetylenes (PDAs) remain a major research area among scientists due to their interesting optical, spectral, electronic, and structural properties. Heavily reviewed in regards to their stimuli responsive properties, much is known about the assortment of sensing and detection capabilities of PDAs. In this article, we look more upon the structural diversities of polydiacetylenes that have been achieved in recent years, particularly from a hierarchical perspective of 1, 2, and 3-dimensional configurations. In addition, we examine how these different dimensional arrangements of PDAs have heralded clear applications in several key areas. Successful integration of these stimuli-responsive "smart" materials into various geometries has required researchers to have a comprehensive understanding of both the fabrication and synthesis processes, as well as the signalling mechanism for the optical, fluorogenic or spectral transitions. The on-going discovery of new PDA formulations continues to provide interesting structural manifestations such as liposomes, tubes, fibres, organic/inorganic incorporated hybrids and composite structures. By highlighting some of the recent conceptual and technological developments, we hope to provide a measure of the current pace in new PDA derivative development as core components in efficient sensor, imaging and display systems.

Self-organization of a polymerizable bolaamphiphile bearing a diacetylene group and L-aspartic acid group

We report herein the self-organization of the polymerizable bolaamphiphile (noted, L-Asp-DA) that contains a diacetylene group and two L-aspartic groups. We found that L-Asp-DA can self-organize into stable fiberlike nanostructures at the mica-water interface. The micellar nanostructures of L-Asp-DA can be polymerized both in the bulk solution and in the film on UV irradiation, and the nanostructures of the L-Asp-DA micelles at the mica-water interface can be maintained after polymerization. The polymerized L-Asp-DA nanostructures can go through blue-red transition upon pH stimuli arising from the transformation of polydiacetylene skeleton. In addition, the concentration (above cmc) of L-Asp-DA has a great effect on the nanostructures. At a concentration of 3.2x10(-4) mol/L, L-Asp-DA can self-organize into stable fiberlike nanostructure at the mica-water interface, while cylindrical nanostructures self-organize at a concentration of 6.0x10(-4) mol/L. This work may provide a new approach for designing and fabricating molecular assemblies with controlled sizes and shapes, leading to the development of novel functional polymer nanostructure materials.

Interfacial self-assembled fabrication of petal-like CdS/ dodecylamine hybrids toward enhanced photoluminescence

We report a new available strategy for fabricating 2-dimensional petal-like CdS/dodecylamine (DDA) hybrids with enhanced photoluminescence (PL) by using a method of oil/water interfacial self-assembly. First, water-soluble CdS nanocrystals (NCs) were controllably prepared at the two-phase interface by injecting the Na2S solution into CCl4 phase. And then, the as-synthesized CdS NCs (ca. 4 nm) were transferred from the water to the CHCl3 phase under the direction of DDA. Finally, through the electrostatic interactions between the positively charged amino of DDA and the negatively charged the ligand of NCs surface, we have successfully fabricated petal-like CdS/DDA hybrids via the interfacial self-assembly between the as-synthesized CdS NCs and DDA. The properties of as-prepared CdS NCs and their hybrids were thoroughly investigated by ultraviolet-visible (UV-vis), transmission electron microscope (TEM), Fourier transform infrared spectra (FT-IR), photoluminescence (PL), scanning electron microscopy (SEM) measurements. We have found that these petal-like CdS/DDA hybrids after interfacial self-assembly exhibit good PL property and higher quantum yield.

Self-organization of polymerizable bolaamphiphiles bearing diacetylene mesogenic group

We report herein the synthesis of a series of polymerizable bolaamphiphiles containing a diacetylene group and mesogenic unit and their self-organization behaviors in bulk and at interface. The polymerizable bolaamphiphiles are noted as DPDA-n, where n refers to the spacer length of alkyl chain. DPDA-10 with suitable spacer length can self-organize into stable cylindrical micellar nanostructures, and these nanostructures have preferred orientation regionally when adsorbed at the mica/water interface. It is confirmed that the micellar nanostructure of DPDA-10 can be polymerized both in the bulk solution and in the film by UV irradiation. The emission property of DPDA-10 after UV irradiation has been significantly enhanced in comparison to that before polymerization, which may be due to the extension of the conjugated system arising from the transformation of the diacetylene group into polydiacetylene upon polymerization. In addition, the self-organization of DPDA-n is dependent on the spacer length. DPDA-7 with a short spacer length forms an irregular flat sheet structure with many defects; DPDA-15 with a long spacer length forms rodlike micellar structures. Thus, this work may provide a new approach for designing and fabricating organic functional nanostructured materials.

The preparation of CdTe nanoparticles and CdTe nanoparticle-labelled microspheres for biological applications

Different sizes of CdTe semiconductor nanoparticles were prepared in aqueous solution. These nanoparticles exhibit narrow fluorescence with full width at half-maximum (FWHM) of 35-45 nm that spans the visible spectrum, and they also have high PL quantum yield with high resistance to photodegradation. In addition, CdTe quantum dot (QD)-labelled microspheres, comprising polystyrene (PS) cores and CdTe/polyelectrolyte (PE) shells, were also prepared by the layer-by-layer technique in this paper. The optical properties of the CdTe nanoparticles and CdTe-labelled microspheres were investigated by UV-Visible absorption and luminescence spectroscopy, and fluorescence microscopy was employed for microscopic identification behaviour of the luminescent microspheres.

Tuning the size and optical properties in molecular nano/microcrystals: manifestation of hierarchical interactions

Intermolecular interactions, such as hydrogen bonding, dipolar and van der Waals, occurring in molecular crystals cover a range of magnitudes. As the crystal evolves from a relatively softer state in the nanoscopic size regime to a harder one in the microcrystalline and bulk solid state, the impact of the hierarchy of intermolecular interactions can be expected to emerge in a progressive fashion. The strongest interactions alone would be manifested at small sizes; as the crystal grows, the effect of the weaker ones will be added on, with the bulk crystals exhibiting the cumulative impact of the different interactions. We demonstrate this phenomenon through investigations of the solution, colloid, and solid state of a novel zwitterionic molecule based on the diaminodicyanoquinodimethane framework. A reprecipitation-digestion protocol is developed for the fabrication of nano/microcrystals of varying sizes. Microscopic and spectroscopic characterizations reveal tuning of the size and optical properties of this material. The optical absorption of the colloidal particles evolves with size towards that of the bulk solid, the emission showing a steady enhancement of intensity. Crystallographic investigations coupled with semiempirical computations provide a viable model to describe the range of observations in terms of the gradual accumulation of hierarchical intermolecular interactions.