SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: Nanoscale

28

Nanopaper is a flexible, transparent, and renewable substrate that is emerging as a replacement for plastic in printed “green” electronics. The underlying science of transparency of nanopaper is that the diameter of these fibers is much smaller than the light wavelength, which significantly decreases the light scattering as compared to regular fibers. Cellulose fibers have a hierarchical structure, which consists of numerous smaller fibers. In this manuscript, we demonstrate a nanopaper design with different fiber diameters, and conclude that the light transmittance and scattering depend on the fiber diameter and packing density. The optical properties of the nanopaper and their dependence on the cellulose fiber diameter are thoroughly explained through Chandrasekhar’s radiative-transfer theory and multiple scattering method simulations. The controllable optical properties of highly transparent nanopaper present an unprecedented opportunity for growth of next-generation optoelectronics.

Concepts: Scientific method, Optics, Light, Greek loanwords, Scattering, Fiber, Cellulose, Cellulose fiber

28

We have observed by NMR spectroscopy that the diffusive movement of a ruthenium-based Grubbs' catalyst increases during ring-closing metathesis as a function of the substrate concentration. This is one of the smallest single molecule motors to exhibit catalytically driven motion.

Concepts: DNA, Enzyme, Chemistry, Olefin metathesis, Molecular motor, Motor, Grubbs' catalyst, Robert H. Grubbs

28

For the realization of high-efficiency flexible optoelectronic devices, transparent electrodes should be fabricated through a low-temperature process and have the crucial feature of low surface roughness. In this paper, we demonstrated a two-step spray-coating method for producing large-scale, smooth and flexible silver nanowire (AgNW)-poly3,4-ethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS) composite electrodes. Without the high-temperature annealing process, the conductivity of the composite film was improved via the lamination of highly conductive PEDOT:PSS modified by dimethyl sulfoxide (DMSO). Under the room temperature process condition, we fabricated the AgNW-PEDOT:PSS composite film showing an 84.3% mean optical transmittance with a 10.76 Ω sq(-1) sheet resistance. The figure of merit Φ(TC) was higher than that obtained from the indium tin oxide (ITO) films. The sheet resistance of the composite film slightly increased less than 5.3% during 200 cycles of tensile and compression folding, displaying good electromechanical flexibility for use in flexible optoelectronic applications.

Concepts: Semiconductor, Solar cell, Indium tin oxide, PEDOT:PSS, Indium(III) oxide, Indium, Dimethyl sulfoxide, Transparent electrodes

28

Gold nanorods exhibit rich colours owing to the nearly linear dependence of the longitudinal plasmon resonance wavelength on the length-to-diameter aspect ratio. This property of Au nanorods has been utilized in this work for dyeing fabrics. Au nanorods of different aspect ratios were deposited on both cotton and silk fabrics by immersing them in Au nanorod solutions. The coating of Au nanorods makes the fabrics exhibit a broad range of colours varying from brownish red through green to purplish red, which are essentially determined by the longitudinal plasmon wavelength of the deposited Au nanorods. The colorimetric values of the coated fabrics were carefully measured for examining the colouring effects. The nanorod-coated cotton fabrics were found to be commercially acceptable in washing fastness to laundering tests and colour fastness to dry cleaning tests. Moreover, the nanorod-coated cotton and silk fabrics show significant improvements on both UV-protection and antibacterial functions. Our study therefore points out a promising approach for the use of noble metal nanocrystals as dyeing materials for textile applications on the basis of their inherent localized plasmon resonance properties.

Concepts: Ratio, Color, Aspect ratio, Ratios, Textile, Primary color, Silk, Tertiary color

28

The origin of the narrow particle size distributions obtained in the oleic acid-based synthesis of hexagonal phase β-NaREF(4) nanocrystals (RE = Sm, Eu, Gd, Tb) has been investigated. Compared to the standard synthesis, the growth conditions were simplified by using small purified particles of either α-NaREF(4) (cubic phase) or β-NaREF(4) (hexagonal phase) as single-source precursors, thereby avoiding the complications arising from the simultaneous presence of molecular educts and intermediately formed small particles. The study shows that α-phase as well as β-phase particles grow by Ostwald-ripening but narrow particle size distributions of the β-NaREF(4) product particles are only obtained when α-phase precursor particles are employed. Since the small particles are also formed as intermediate products in the standard synthesis of β-NaSmF(4), β-NaEuF(4), β-NaGdF(4) and β-NaTbF(4) particles, their crystal phase is an important parameter to obtain a narrow size distribution in these systems.

Concepts: Crystal, Crystallography, Particle size distribution, Crystal system, Particle, Liquid crystal, Crystallographic database, Atomic packing factor

28

We investigate the strain effect on the radiation hardness of hexagonal boron nitride (h-BN) monolayers using density functional theory calculations. Both compressive and tensile strains are studied in elastic domains along the zigzag, armchair, and biaxial directions. We observe a reduction in radiation hardness to form boron and nitrogen monovacancies under all strains. The origin of this effect is the strain-induced reduction of the energy barrier to displace an atom. An implication of our results is the vulnerability of strained nanomaterials to radiation damage.

Concepts: Physics, Hydrogen, Nitrogen, Carbon, Kinetic energy, Density functional theory, Materials science, Boron nitride

28

Gold nanorods with three different aspect ratios were prepared and their dual capabilities for two-photon imaging and two-photon photodynamic therapy have been demonstrated. These gold nanorods exhibit large two-photon absorption action cross-sections, about two orders of magnitude larger than small organic molecules, which makes them suitable for two-photon imaging. They can also effectively generate singlet oxygen under two-photon excitation, significantly higher than traditional photosensitizers such as Rose Bengal and Indocyanine Green. Such high singlet oxygen generation capability under two-photon excitation was ascribed to their large two-photon absorption cross-sections. Polyvinylpyrrolidone (PVP) coated gold nanorods displayed excellent biocompatibility and high cellular uptake efficiency. The two-photon photodynamic therapy effect and two-photon fluorescence imaging properties of PVP coated gold nanorods have been successfully demonstrated on HeLa cells in vitro using fluorescence microscopy and indirect XTT assay method. These gold nanorods thus hold great promise for imaging guided two-photon photodynamic therapy for the treatment of various malignant tumors.

Concepts: Protein, Oxygen, Cancer, Two-photon excitation microscopy, Aspect ratio, Singlet oxygen, Photodynamic therapy, Rose bengal

28

The advancement of mechanical actuators benefits from the development of new structural materials with prominent properties. A novel three-dimensional (3D) hydrothermally converted graphene and polypyrrole (G-PPy) hybrid electrochemical actuator is presented, which is prepared via a convenient hydrothermal process, followed by in situ electropolymerization of pyrrole. The 3D pore-interconnected G-PPy pillar exhibits strong actuation responses superior to pure graphene and PPy film. In response to the low potentials of ±0.8 V, the saturated strain of 3D G-PPy pillar can reach a record of 2.5%, which is more than 10 times higher than that of carbon nanotube film and about 3 times that of unitary graphene film under an applied potential of ±1.2 V. Also, the 3D G-PPy actuator exhibits high actuation durability with high operating load as demonstrated by an 11 day continuous measurement. Finally, a proof-of-concept application of 3D G-PPy as smart filler for on/off switch is also demonstrated, which indicates the great potential of the 3D G-PPy structure developed in this study for advanced actuator systems.

Concepts: Carbon, Carbon nanotube, Graphite, Actuator, Switch, Organic electronics, Polypyrrole, Linear actuator

28

We demonstrate self-aligned and high-performance liquid crystal (LC) systems doped with 1-dimensional (1D) chain-like clusters of CuInS(2) (CIS)-ZnS core-shell quantum dots (QDs). By changing the cell fabrication method of the LC-QD composites, we can selectively control the orientation of the LC molecules between the homogeneous and homeotropic states without conventional LC alignment layers. The homeotropic alignment of LCs was achieved by random dropcasting and the homogeneous alignment was performed using a capillary injection of LC-QDs due to the random or linear diffusion of QD clusters into ITO defects. The electrically compensated bend (ECB)- and vertically aligned (VA) mode LC displays (LCDs) containing our LC-QD composite both showed superior electro-optic (EO) properties. A 37.1% reduction in the threshold voltage (V(th)) and a 36.6% decrease in the response time were observed for ECB mode LCDs, and a 47.0% reduction in the V(th) and a 38.3% decrease in the response time were observed for VA mode LCDs, meaning that the proposed LC-QD composites have a great potential for the production of advanced flexible LCDs.

Concepts: Crystal, Matter, Atom, Liquid crystal display, Liquid crystal, Homogeneous alignment, Homeotropic alignment, Blue Phase Mode LCD

28

Two kinds of Cu(2)O-ZnO nano-heteroarchitectures were fabricated through a hydrothermal method. By utilizing polyethyleneimine (PEI) as a binding agent, ZnO nanoparticles were uniformly self-assembled onto Cu(2)O micro structures. Photoluminescence (PL), field emission and photocatalytic activities of the composite samples were investigated and compared with those of the pure Cu(2)O samples. The results reveal that ZnO nanoparticles combined on Cu(2)O microstructures remarkably changed the PL signals, and significantly enhanced the field emission and photocatalytic activities. The novel PL properties, enhanced field emission and photocatalysis activities are attributed to the electron transition and the inhibition of photo-induced electron-hole pairs recombination, which stem from interfacial defect states and energy band differentials at the interface of Cu(2)O and ZnO. The surface nano-protrusions, large surface area and better dye adsorption induced by ZnO nanoparticles are responsible for the field emission and photocatalysis improvements as well.

Concepts: Catalysis, Semiconductor, Titanium dioxide, Object-oriented programming, Surface area, Electronic band structure, Band gap, Electron hole