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This work describes a novel technique for the measurement of inorganic arsenic in water by generating arsine gas and detecting the conductivity of moving protons, H+ (aqueous or aq), produced by the reaction: Ag+ (aq) + AsH3 (gas, g) → AgAsH2 (solid, s) + H+ (aq). The detection is based on an electrochemical gradient of protons in a confined porous substrate (filter paper) and measures the change in the conductance due to the higher mobility of H+ compared to other ions. The conductance was measured with a pair of silver electrodes attached to opposite sides of the substrate with a bipolar pulse conductance technique. The method is established in theory and in practice. The theoretical equation for conductance change shows that a constant increase in conductance is directly proportional to the As(total) concentration. The method is validated with a standard reference material and applied to the measurement of the groundwater sample. [ABSTRACT FROM AUTHOR]

In this work, in-plane thermal conductivity measurement was carried out on graphene-based papers. Graphene-based papers were fabricated using various processing techniques such as chemical vapor deposition (CVD), hot pressing of graphene slurry, and evaporation induced self-assembly. The prepared materials were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. In-plane thermal conductivity measurement was performed via a steady state thin film thermal conductivity apparatus. The in-plane thermal conductivity measurements show that the CVD based sample has the highest thermal conductivity. COMSOL Multiphysics was used to simulate the in-plane thermal conductivity of graphene-based papers. [ABSTRACT FROM AUTHOR]

A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 μm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate was strongly perturbed by protruding fibers of the base paper. Such fibers together with the surface topography of the base paper seem to be the major factors that control the leveling of toner and its penetration into a thinly coated paper substrate. [ABSTRACT FROM AUTHOR]

In this work, we describe the synthesis of novel electrically and magnetically dual-driven Janus particles for a handwriting-enabled twisting ball display via the microfluidic technique. One hemisphere of the Janus particles contains a charge control agent, which allows the display color to be controlled by applying a voltage and superparamagnetic nanoparticles, allows handwriting by applying a magnetic field to the display. We fabricated a twisting ball display utilizing these Janus particles and tested the electric color control and handwriting using a magnet. As a result, the display was capable of permitting handwriting with a small magnet in addition to conventional color control using an applied voltage (80 V). Handwriting performance was improved by increasing the concentration of superparamagnetic nanoparticles and was determined to be possible even when 80V was applied across the electrodes for 4 wt.% superparamagnetic nanoparticles in one hemisphere. This improvement was impossible when the concentration was reduced to 2 wt.% superparamagnetic nanoparticles. The technology presented in our work can be applied to low-cost, lightweight, highly visible, and energy-saving electronic message boards and large whiteboards because the large-size display can be fabricated easily due to its simple structure. [ABSTRACT FROM AUTHOR]

The present research experiments the applicability of x-ray texture analysis in investigating the properties of paper coatings. The preferred orientations of kaolin, talc, ground calcium carbonate, and precipitated calcium carbonate particles used in four different paper coatings were determined qualitatively based on the measured crystal orientation data. The extent of the orientation, namely, the degree of the texture of each pigment, was characterized quantitatively using a single parameter. As a result, the effect of paper calendering is clearly seen as an increase on the degree of texture of the coating pigments. The effect of calendering on the preferred orientation of kaolin was also evident in an independent energy dispersive spectrometer analysis on micrometer scale and an electron spectroscopy for chemical analysis on nanometer scale. Thus, the present work proves x-ray texture analysis to be a potential research tool for characterizing the properties of paper coating layers. [ABSTRACT FROM AUTHOR]

We report fabrication of reduced graphene oxide (rGO) films using chemical reduction by hydrazine hydrate and rGO paper-like samples using low temperature treatment reduction. Structural analysis confirms the formation of the rGO structure for both samples. Current-voltage (I-V) measurements of the rGO film reveal semiconductor behavior with the maximum current value of ~3×10-4A. The current for the rGO paper sample is found to be, at least, one order of magnitude higher. Moreover, bipolar resistance switching, corresponding to memristive behavior of type II, is observed in the I-V data of the rGO paper. Although precise values of the rGO film conductivity and the Seebeck coefficient could not be measured, rGO paper shows an electrical conductivity of 6.7×102S/m and Seebeck coefficient of -6μV/°C. Thus, we demonstrate a simplified way for the fabrication of rGO paper that possesses better and easier measurable macroscopic electrical properties than that of rGO thin film. [ABSTRACT FROM AUTHOR]