Porous Graphitic Carbons Containing Nitrogen by Structuration of Chitosan with Pluronic P123

Using Pluronic P123 as a structure-directing agent and chitosan as a carbon precursor, different porous carbons with remarkable morphologies such as orthohedra or spheres with diametrically opposite holes are obtained. These particles of micrometric size are constituted by the stacking of thin sheets (60 nm) that become increasingly bent in the opposite sense, concave in the upper and convex in the bottom hemispheres, as the chitosan proportion increases. TEM images, after dispersion of the particles by sonication, show that besides micrometric graphene sheets, the material is constituted by nanometric onion-like carbons. The morphology and structure of these porous carbons can be explained based on the ability of Pluronic P123 to undergo self-assembly in aqueous solution due to its amphoteric nature and the filmogenic properties of chitosan to coat Pluronic P123 nanoobjects undergoing structuration and becoming transformed into nitrogen-doped graphitic carbons. XPS analysis reveals the presence of nitrogen in their composition. These porous carbons exhibit a significant CO2 adsorption capacity of above 3 mmol g-1 under 100 kPa at 273 K attributable to their large specific surface area, ultraporosity, and the presence of basic N sites. In addition, the presence of dopant elements in the graphitic carbons opening the gap is responsible for the photocatalytic activity for H2 generation in the presence of sacrificial electron donors, reaching a H2 production of 63 μmol g-1 in 24 h.

Novel Trends in Lyotropic Liquid Crystals

We introduce and shortly summarize a variety of more recent aspects of lyotropic liquid crystals (LLCs), which have drawn the attention of the liquid crystal and soft matter community and have recently led to an increasing number of groups studying this fascinating class of materials, alongside their normal activities in thermotopic LCs. The diversity of topics ranges from amphiphilic to inorganic liquid crystals, clays and biological liquid crystals, such as viruses, cellulose or DNA, to strongly anisotropic materials such as nanotubes, nanowires or graphene oxide dispersed in isotropic solvents. We conclude our admittedly somewhat subjective overview with materials exhibiting some fascinating properties, such as chromonics, ferroelectric lyotropics and active liquid crystals and living lyotropics, before we point out some possible and emerging applications of a class of materials that has long been standing in the shadow of the well-known applications of thermotropic liquid crystals, namely displays and electro-optic devices.

Super Stability of Ag Nanoparticle in Crystalline Lamellar (Lc) Liquid Crystal Matrix at Different pH Environment

The symmetry concept in this paper is related to the natural self-assembly of noble metal nanoparticles in the long range periodic structure of liquid crystal (LC). The current study deliberates the effect of pH on the stability of nanoparticles (NPs) in the lamellar phase of a lyotropic LC environment. The LC was prepared by the mass ratio 0.33:0.22:0.45 for (HDTABr):1-pentanol:water. The LC containing silver nanoparticles (AgNPs) was prepared by replacing the water with Ag solution. The AgNPs were produced by the in situ preparation method in LC. The solution of AgNPs-LC was varied at different pH. The absorption intensities were determined by using ultra-violet spectroscopy (UV-vis). The surface potential and hydrodynamic particle size were determined by using Zeta-potential (measurements). The surface enhanced Raman spectroscopy (SERS) was carried out to enhance the Raman signals of 4-aminobenzenethiol (4-ABT) deposited onto AgNPs as substrate. It is found that all characterizations exhibited super stability for AgNPs dispersed in LC at pH = 3 to 12 with the optimum stability at pH = 5–6. The remarkable stability of NPs is an important indicator of the various applications in nanotechnology and nanoscience fields.

Urea-assisted cooperative assembly of phosphorus dendrimer–zinc oxide hybrid nanostructures

The interplay of phosphorus dendrimer–urea during sol–gel mineralization of soluble zinc precursors provides porous lamellar nanostructures.

Lyotropic Liquid Crystal Phases from Anisotropic Nanomaterials

Liquid crystals are an integral part of a mature display technology, also establishing themselves in other applications, such as spatial light modulators, telecommunication technology, photonics, or sensors, just to name a few of the non-display applications. In recent years, there has been an increasing trend to add various nanomaterials to liquid crystals, which is motivated by several aspects of materials development. (i) addition of nanomaterials can change and thus tune the properties of the liquid crystal; (ii) novel functionalities can be added to the liquid crystal; and (iii) the self-organization of the liquid crystalline state can be exploited to template ordered structures or to transfer order onto dispersed nanomaterials. Much of the research effort has been concentrated on thermotropic systems, which change order as a function of temperature. Here we review the other side of the medal, the formation and properties of ordered, anisotropic fluid phases, liquid crystals, by addition of shape-anisotropic nanomaterials to isotropic liquids. Several classes of materials will be discussed, inorganic and mineral liquid crystals, viruses, nanotubes and nanorods, as well as graphene oxide.

One-Step Synthesis of Hybrid Liquid-Crystal ZnO Nanoparticles: Existence of a Critical Temperature Associated with the Anisotropy of the Nanoparticles

Zinc oxide nanoparticles were obtained from the hydrolysis of an organometallic precursor in pure hexadecylamine. Interestingly, we demonstrate that the final (anisotropic or isotropic) shape of the nanoparticles is strongly correlated to the existence of a critical temperature. This suggests that the organization of the fatty amines is a paramount parameter in this synthesis. Moreover, the final hybrid ZnO materials systematically exhibit a liquid-crystal smectic phase, whereas no liquid-crystal phase was observed in the pristine reaction media. This simple process is, therefore, a direct and straightforward method to synthesize liquid-crystal hybrid materials.

Mesomorphic ionic hyperbranched polymers: effect of structural parameters on liquid-crystalline properties and on the formation of gold nanohybrids

Branched thermotropic liquid crystals were successfully obtained from ionic interactions between hyperbranched polyamidoamine and sodium dodecylsulfate. These complexes present columnar rectangular and lamellar thermotropic mesophases as demonstrated by polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering. The relationships between the structural characteristics of the polymers (size of the hyperbranched core, hyperbranched or dendritic nature of the core, and substitution ratio) and the mesomorphic properties were studied. In situ formation of gold nanoparticles was then performed. The templating effect of the liquid crystal mesophase resulted in the formation of isotropic nanoparticles, the size of which was dictated by the local organization of the mesophase and by the molar mass of the hyperbranched complex.

Liquid crystalline thermotropic and lyotropic nanohybrids

This review is meant to give the reader an insight into hybrids incorporating different types of nanoparticles, e.g. metallic or metal oxides, within different types of lyotropic and thermotropic liquid crystals, from relatively small calamitic molecules to the larger discotics and polymers. In particular, this review highlights the importance of nanoparticle-liquid crystal interactions in accessing hybrid materials that exhibit synergetic properties.