Nanoscale

doi: 10.1039/c2nr90041fpmid: N/A

doi: 10.1039/c2nr90042dpmid: N/A

doi: 10.1039/c2nr90040hpmid: N/A

Lin, Ning; Huang, Jin; Dufresne, Alain

doi: 10.1039/c2nr30260hpmid: 22565323

Intensive exploration and research in the past few decades on polysaccharide nanocrystals, the highly crystalline nanoscale materials derived from natural resources, mainly focused originally on their use as a reinforcing nanophase in nanocomposites. However, these investigations have led to the emergence of more diverse potential applications exploiting the functionality of these nanomaterials. Based on the construction strategies of functional nanomaterials, this article critically and comprehensively reviews the emerging polysaccharide nanocrystal-based functional nanomaterials with special applications, such as biomedical materials, biomimetic optical nanomaterials, bio-inspired mechanically adaptive nanomaterials, permselective nanostructured membranes, template for synthesizing inorganic nanoparticles, polymer electrolytes, emulsion nano-stabilizer and decontamination of organic pollutants. We focus on the preparation, unique properties and performances of the different polysaccharide nanocrystal materials. At the same time, the advantages, physicochemical properties and chemical modifications of polysaccharide nanocrystals are also comparatively discussed in view of materials development. Finally, the perspective and current challenges of polysaccharide nanocrystals in future functional nanomaterials are outlined.

Adisa, Olumide O.; Cox, Barry J.; Hill, James M.

doi: 10.1039/c2nr00042cpmid: 22538768

We survey various molecular structures which have been proposed as possible nanocontainers for methane storage. These are molecular structures that have been investigated through either experiments, molecular dynamics simulations or mathematical modelling. Computational simulation and mathematical modelling play an important role in predicting and verifying experimental outcomes, but both have their limitations. Even though recent advances have greatly improved computations, due to the large number of atoms and force field calculations involved, computational simulations can still be time consuming as compared to an instantaneous mathematical modelling approach. On the other hand, underlying an ideal mathematical model, there are many assumptions and approximations, but such modelling often reveals the key physical parameters and optimal configurations. Here, we review methane adsorption for three conventional nanostructures, namely graphite, single and multi-walled carbon nanotubes, and nanotube bundles (including interstitial and groove sites), and we survey methane adsorption in other molecular structures including metal organic frameworks. We also include an examination of minimum binding energies, equilibrium distances, gravimetric and volumetric uptakes, volume available for adsorption, as well as the effects of temperature and pressure on the adsorption of methane onto these molecular structures.

Ifuku, Shinsuke; Saimoto, Hiroyuki

doi: 10.1039/c2nr30383cpmid: 22539071

Chitin nanofibers are prepared from the exoskeletons of crabs and prawns by a simple mechanical treatment after the removal of proteins and minerals . The obtained nanofibers have fine nanofiber networks with a uniform width of approximately 10–20 nm and a high aspect ratio. The method used for chitin -nanofiber isolation is also successfully applied to the cell walls of mushrooms. They form a complex with glucans on the fiber surface. A grinder, a Star Burst atomization system, and a high speed blender are all used in the mechanical treatment to convert chitin to nanofibers. Mechanical treatment under acidic conditions is the key to facilitate fibrillation. At pH 3–4, the cationization of amino groups on the fiber surface assists nano-fibrillation by electrostatic repulsive force. By applying this finding, we also prepared chitin nanofibers from dry chitin powder. Chitin nanofibers are acetylated to modify their surfaces. The acetyl DS can be controlled from 1 to 3 by changing the reaction time. An acetyl group is introduced heterogeneously from the surface to the core. Nanofiber morphology is maintained even in the case of high acetyl DS. Optically transparent chitin nanofiber composites are prepared with 11 different types of acrylic resins. Due to the nano-sized structure, all of the composites are highly transparent. Chitin nanofibers significantly increase the Young's moduli and the tensile strengths and decrease the thermal expansion of all acrylic resins due to the reinforcement effect of chitin nanofibers. Chitin nanofibers show chiral separation ability. The chitin nanofiber membrane transports the d-isomer of glutamic acid, phenylalanine, and lysine from the corresponding racemic amino acid mixtures faster than the corresponding l-isomer. The chitin nanofibers improve clinical symptoms and suppress ulcerative colitis in a DSS-induced mouse model of acute ulcerative colitis. Moreover, chitin nanofibers suppress myeloperoxidase activation in the colon and decrease serum interleukin-6 concentrations.

Quarta, Alessandra; Curcio, Alberto; Kakwere, Hamilton; Pellegrino, Teresa

doi: 10.1039/c2nr30271cpmid: 22572969

The use of inorganic nanoparticles in biomedicine, in particular in the field of diagnosis and therapy of human diseases, has rapidly grown in the last few decades. Water solubilisation of the nanoparticles, especially for particles synthesized in non-polar solvents, is an essential prerequisite for their biological exploitation. The encapsulation of surfactant coated nanoparticles into polymer shells represents one of the most suitable and most popular methods to make them water soluble. Herein we provide an overview of the amphiphilic polymer molecules used and the efforts undertaken to further tailor the surface of polymer coated nanoparticles with fluorescent dyes, chemical sensor molecules and small or large biomolecules for the preparation of bio-functional nanoprobes. Their biological implications, highlighting limitations and challenges, are also discussed.

Glukhova, Olga; Slepchenkov, Michael

doi: 10.1039/c2nr30477epmid: 22543701

Electronic and adsorptive properties of deformed graphene are investigated in the current work. Armchair and zigzag nanoribbons are the subject of the study. The axial compression was a deforming load. A calculation method for the local stress field was developed. This method was based on the quantum model of the finite graphene nanoribbon and empirical calculation method of the single atom energy. The stress field of the deformed ribbon was calculated by means of the suggested methodology. The effects of the atomic grid curvature on the adsorptive capacity of graphene and the hydrogenation process was investigated by means of the developed method. The prediction of the appearance of defects on covalent C–C bond breakdown is also performed.

Tian, He; Xie, Dan; Yang, Yi; Ren, Tian-Ling; Wang, Yu-Feng; Zhou, Chang-Jian; Peng, Ping-Gang; Wang, Li-Gang; Liu, Li-Tian

doi: 10.1039/c2nr30417apmid: 22562717

Due to the extremely high thermal conductivity and low heat capacity per unit area of graphene, it is possible to fabricate an efficient sound-emitting device based on the thermoacoustic effect with no mechanical vibration. In this paper, the fundamental performance of this new graphene sound-emitting device (G-SED) is investigated in terms of its static behavior. The sound amplitude mapping shows that the G-SED has good sound performance under 0.01 W. The sound frequency spectra measured at different distances and angles show that the G-SED has good sound directivity. It is possible to realize sound wave manipulation by using an array of G-SEDs. The relationship between the temperature of graphene and the sound frequency was investigated by a thermal imaging instrument. The fast transient sound response in real time was recorded by applying 60 μs short time multi-pulses and single-pulse. The stable sound emission at a constant sound pressure amplitude with low noise was observed for continuous operation under a fixed frequency over several hours. Such significant performances in this G-SED indicate broad applications, and shed light on the use of graphene in the field of acoustics.

Wang, Zhuoran; Ran, Sihan; Liu, Bin; Chen, Di; Shen, Guozhen

doi: 10.1039/c2nr30440fpmid: 22549639

A multilayer TiO2 nanorod-assembled cloth/nanorod array based electrode was fabricated by transferring different layers of TiO2 nanorod-assembled cloth (TNRC) onto nanorod array grown on the conducting FTO substrate (titania nanorod, TNR). Combining the superior electron transport characteristics of TNR and outstanding optical properties of TNRC, the nanostructured electrode composed of two layers of TNRC meets the optimized design for high quality dye-sensitized solar cells (DSCs) and self-powered UV detectors. The highest efficiency of 4.02% for DSC under AM 1.5 was achieved with a high short circuit current density of 9.81 mA cm−2, which was proved to be owing to the enhanced dye anchoring, light scattering and reduced charge recombination. For the photoelectrochemical (PEC) UV detector, the highest quantum efficiency of over 46% was obtained and a high photocurrent response of 0.271 mA cm−2 was observed, together with the excellent self-powered, fast response and “visible blind” characteristics. A perfect linear response to the changed low-power signal indicates great potential for practical applications.