Simulation study on discrete charge effects of SiNW biosensors according to bound target position using a 3D TCAD simulator

We introduce a simulation method for the biosensor environment which treats the semiconductor and the electrolyte region together, using the well-established semiconductor 3D TCAD simulator tool. Using this simulation method, we conduct electrostatic simulations of SiNW biosensors with a more realistic target charge model where the target is described as a charged cube, randomly located across the nanowire surface, and analyze the Coulomb effect on the SiNW FET according to the position and distribution of the target charges. The simulation results show the considerable variation in the SiNW current according to the bound target positions, and also the dependence of conductance modulation on the polarity of target charges. This simulation method and the results can be utilized for analysis of the properties and behavior of the biosensor device, such as the sensing limit or the sensing resolution.     

The work function of doped polyaniline nanoparticles observed by Kelvin probe force microscopy

The work function of polyaniline nanoparticles in the emeraldine base state was determined by Kelvin probe force microscopy to be ～270 meV higher than that of similar nanoparticles in the emeraldine salt state. Normal tapping mode atomic force microscopy could not be used to distinguish between the particles due to their similar morphologies and sizes. Moreover, other potential measurement systems, such as using zeta potentials, were not suitable for the measurement of surface charges of doped nanoparticles due to their encapsulation by interfering chemical groups. Kelvin probe force microscopy can be used to overcome these limitations and unambiguously distinguish between the bare and doped polyaniline nanoparticles.     

Stable cycling of double-walled silicon nanotube battery anodes through solid-electrolyte interphase control

Although the performance of lithium ion-batteries continues to improve, their energy density and cycle life remain insufficient for applications in consumer electronics, transport and large-scale renewable energy storage. Silicon has a large charge storage capacity and this makes it an attractive anode material, but pulverization during cycling and an unstable solid-electrolyte interphase has limited the cycle life of silicon anodes to hundreds of cycles. Here, we show that anodes consisting of an active silicon nanotube surrounded by an ion-permeable silicon oxide shell can cycle over 6,000 times in half cells while retaining more than 85% of their initial capacity. The outer surface of the silicon nanotube is prevented from expansion by the oxide shell, and the expanding inner surface is not exposed to the electrolyte, resulting in a stable solid-electrolyte interphase. Batteries containing these double-walled silicon nanotube anodes exhibit charge capacities approximately eight times larger than conventional carbon anodes and charging rates of up to 20C (a rate of 1C corresponds to complete charge or discharge in one hour).     

Electro-optical properties of nano-thickness polymer film

We report the electro-optical (E/O) characteristics of the Langmuir-Blodgett film of poly(vinylidene fluoride with trifluoroethylene) copolymers. The structural origin of E/O response of nano LB films was discussed with the result of temperature dependent E/O response at a temperature range from 20 to 100 degrees C. Thermal hysteresis of E/O response and the ferroelectric-paraelectric phase transition were observed at a 20 monomolecular layers Langmuir-Blodgett films.     

Structural, magnetic, infrared and Raman studies of La0.8Sr x Ca0.2-x MnO3 (0 ≤ x ≤ 0.2)

We report the results of magnetic, X-ray powder diffraction, infrared and temperature dependent Raman spectra of the La_0.8Sr _x Ca_0.2-x MnO₃ (0 ≤ x ≤ 0.2) manganite. The structure refinement using the Rietveld method indicates that the partial substitution of strontium for calcium (for x ≥ 0.15) modifies the orthorhombic structure of the CaMnO₃ perovskite towards a rhombohedral phase. Magnetic measurement confirms the increase in the Curie temperature from 180 K for La_0.8Ca_0.2MnO₃ to 307 K for La_0.8Sr_0.2MnO₃, respectively. It is argued that the substitution with the larger Sr²⁺ ion strengthens the double-exchange interaction and gives rise to the observed increase of transition temperatures. All manganites show two IR active vibrational modes around 400 and 600 cm^?1. Moreover, when x ≤ 0.1, the absorption band around 400 cm^?1 splits into two peaks. In addition, we have analyzed the frequencies and widths of the observed Raman modes as a function of temperature for all samples with various Sr content. The mode splitting is attributed to both magnetic ordering and large orthorhombic distortion in doped rhombohedral manganites.     

Controlled hydrothermal growth of multi-length-scale ZnO nanowires using liquid masking layers

In this study, we demonstrate a method for creating multi-length-scale ZnO nanowires in a controllable manner on diverse planar and curvilinear substrates by introducing immiscible liquid masking layers (LMLs) above and beneath a nutrient solution used in hydrothermal growth. The confinement of volatile reactants by the LMLs stabilizes the pH, which is an important parameter in determining the shape of the nanowires, to enable growth in a stable manner. The conformal wettability of the LMLs provides freedom in the choice of target substrates and allows for the possibility of mounting spatially moving stages without the use of a specially designed solid lid. Selective growth within the growth zone defined by the LMLs in a dynamic- and/or static-mode can create various types of ZnO nanowires with gradual or terraced length profiles in two- or three-dimensional geometries. For a device application, we developed cylindrical photodetectors with the configuration of Cr/ZnO seed/ZnO nanowires/poly(3-hexylthiophene-2,5-diyl)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) to show the ability to spatially modulate the photo-sensitivity by controlled hydrothermal growth of diverse length scales of ZnO nanowires using the LML method.     

Highly conductive and mechanically robust multiwalled carbon nanotube-polyamide nanocomposites via noncovalent functionalization

Journal of Materials Science - Electrically conductive multiwalled carbon nanotube (MWNT)/polyamide 6 (PA 6) nanocomposite films with high mechanical strength were fabricated by blending modified...