In-situ growth of copper sulfide nanocrystals on multiwalled carbon nanotubes and their application as novel solar cell and amperometric glucose sensor materials

Single-crystalline copper sulfide (beta-Cu2S) nanocrystals (NCs) were grown in situ on multiwalled carbon nanotubes (MWCNTs) by the solvothermal method. The morphology of the Cu2S NCs was varied from spherical particles (av size=4 nm) to triangular plates (av size=12 nm) by increasing the concentration of the precursors. The lattice matching between Cu2S and the MWCNTs would be an important factor in the growth of Cu2S NCs on the MWCNTs. The solar cells and the amperometric glucose sensors fabricated using these Cu2S-MWCNT hybrid nanostructures respond more sensitively than those using the Cu2S NCs (or MWCNTs) alone. The utilization of the active Cu2S NCs through direct binding with the conductive MWCNTs would lead to excellent performance of these nanodevices.     

Photocurrent imaging of p-n junctions in ambipolar carbon nanotube transistors

We use scanning photocurrent microscopy (SPCM) to investigate the properties of internal p-n junctions in ambipolar carbon nanotube (CNT) transistors. Our SPCM images show strong signals near metal contacts whose polarity and positions change depending on the gate bias. SPCM images analyzed in conjunction with the overall conductance also indicate the existence and gate-dependent evolution of internal p-n junctions near contacts in the n-type operation regime. To determine the p-n junction position and the depletion width with a nanometer scale resolution, a Gaussian fit was used. We also measure the electric potential profile of partially suspended CNT devices at different gate biases, which shows that induced local fields can be imaged using the SPCM technique. Our experiment clearly demonstrates that SPCM is a valuable tool for imaging and optimizing electrical and optoelectronic properties of CNT based devices.     

Dry sol-gel polycondensation of hydrosilanes to organosilicas catalyzed by colloidal nickel nanoparticles

The dry sol-gel polycondensation at toluene in ambient air atmosphere of p-X-C6H4SiH3 (X = H, CH3, CH3O, F, Cl) to silica p-X-C6H4SiO15 in high yield, catalyzed by colloidal nickel nanoparticles in-situ generated from nickelocene(II), nickel(II) acetate, and bis(1,5-cyclooctadiene)nickel(0), is described. Similar catalytic activities were observed for the catalysts. Similarly, the dry sol-gel polyco-condensation p-X-C6H4SiH3 (X = CH3, CH3O, F, Cl):C6H4SiH3 (9:1 mole ratio) at toluene in ambient air atmosphere of was performed to yield co-silicas (p-X-C6H4SiO1.5)9(p-X-C6H4SiO1.5)1 in high yield using nickelocene. The co-gels with higher molecular weights and TGA residue yield were obtained when compared to the homogels. The highest yield, molecular weight, polydispersity index, and TGA residue yield were obtained for p-Cl-C6H4SiH3. Some degree of unreacted Si-H bonds still remained in the gel matrix because of steric bulkiness. All the insoluble gels adopt an amorphous structure with a smooth surface. A plausible mechanism for the dry sol-gel reaction was suggested.     

Nanocrystalline particle coatings on alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route

We have suggested ultrafine particle coating processes for preparing nanocrystalline particle coated alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route, which is environmentally friendly. The nanometric ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of alumina was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The synthetic crystalline size and morphology were greatly dependent on pH and temperature. By adding ammonium aluminum sulfate solution dispersed the alpha-alumina core particle in the ammonium hydrogen carbonate aqueous solution, nanometric AACH with a size of 5 nm was tightly bonded and uniformly coated on the core powder due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of aluminum oxide. The synthetic precursor rapidly converted to amorphous- and y-alumina phase without significant change in the morphological features through decomposition of surface complexes and thermal-assisted phase transformation. As a result, the nanocrystalline polymorphic particle coated alpha-alumina core powders with highly uniform distribution were prepared from the route of carbonate precipitation and thermal-assisted combustion.     

Soft-chemical synthesis and electrochemical characterization of multicomponent Mn(1-x-y)Co(x)Ni(y)O2 nanostructures

Nanostructured Mn(1-x-y)Co(x)Ni(y)O2 metal oxides are synthesized by one-pot hydrothermal reaction at low temperature. From powder X-ray diffraction and field emission-scanning electron microscopic analyses, it is found that the crystal structure and crystal morphology of the present materials are tunable by the control of the composition of precursor. 1D nanowires with alpha-MnO2-type structure are prepared with low substitution rate of Co and Ni, while the increase of substituent contents leads to the formation of delta-MnO2-structured 3D nanospheres consisting of 2D nanoplates. According to X-ray absorption near edge spectroscopy and chemical analyses, mixed valent Co(III)/Co(IV) and divalent Ni(II) ions are stabilized in the octahedral Mn sites of alpha-MnO2- and delta-MnO2-structures. The electrochemical measurements clearly demonstrate that the present nanostructured materials show promising electrode performances for lithium secondary batteries.     

Properties and interaction of cement with polymer in the hardened cement pastes added absorbent polymer

Ordinary Portland cement mixed with various amounts of absorbent polymer in the form of sodium acrylate ((–CH–)_nCOONa) have been studied. As the content of absorbent polymer increased, heat evolution of samples decreased up to 1.15 wt % of absorbent polymer addition and conversely increased over 1.75 wt %. Flexural strength of cement paste with absorbent polymer was improved more than 20%. As the content of absorbent polymer increased, the porosity values decreased and mean pore diameter shifted to small pore diameter region. Flexural strength of ordinary Portland cement paste had a linear correlation with non-evaporable water content but, that of cement paste with absorbent polymer deviated from a linear correlation with non-evaporable water content. The chemical difference between cement pastes with and without absorbent polymer was found by the inductively coupled plasma-atomic emission spectroscopy and the infrared spectroscopy. For the infrared spectra of absorbent polymer, bands at 1416 and 1560 cm^{– 1} were assigned to C–O single bond and C=O double bond respectively, namely, unidentate complex. As the curing time increased, the absorption bands near 1416 cm^{– 1} shifted to longer wave number and the absorption bands near 1560 cm^{– 1} to shorter wave number and finally bidentate complex was formed. Absorbent polymer released sodium ions to pore solution under the basic condition of pH 12.5–13.5 and became polyacrylic acid. Then some of these polyacrylic acid were crosslinked with others by calcium ions leached from cement grains. Calcium ion was regarded as a central charge connecting the negative parts in carbon-oxygen polarization of absorbent polymer' functional groups.     

Constitutive Photomorphogenic 1 Enhances ER Stress Tolerance in Arabidopsis

Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus.     

Barrier property by controlled laminar morphology of LLDPE/EVOH blends

Using the extrusion blown film process, we obtained linear low density polyethylene (LLDPE)/ethylenevinyl alcohol copolymer (EVOH) blends with an improved barrier property by generating a laminar structure of the dispersed phase in the matrix phase. This laminar morphology induced by drawing and blowing was found to result in a significant decrease in toluene permeability with only 10 wt% EVOH. Effects of compatibilizer content and processing parameters such as blending sequence, screw configuration, and stretch ratio on the toluene permeability and morphology of the blends were investigated. It was revealed that the optimum amount of compatibilizer, maleic anhydride grafted LLDPE, should be used to improve the barrier property of the LLDPE/EVOH blends with a well developed laminar structure. The blending sequence had a significant influence on the permeability of the blends. The blend films exhibited a more pronounced laminar structure when all blend components were simultaneously melt blended in a single screw extruder. In addition, the screw configuration designed to impart a low shear stress and the balanced stretching in the machine and transverse directions were more favorable processing conditions in obtaining high barrier blends.     

Computational investigation on the flow characteristics in beam dyeing process

Abstract

Ensuring uniform addition of coloring material to the fabric is an essential requirement in the textile dyeing process. Beam dyeing machine consists of a special beam, the barrel of which is evenly perforated with holes. The dye liquor is forced into the fabric material through this beam. For uniform fabric coloring, an equal distribution of the dye liquor through the porous beam has to be ensured. The present methodology employs theoretical and computational fluid dynamics aspects of beam dyeing process to obtain better performance. The analysis of a beam with a single row of branches shows that nonuniformity increases with an increase in inlet mass flow. Further beam flow distribution with and without fabric are studied for different parameters, such as branch diameter, inlet mass flow rate, operating conditions, and flow reversal. The present results provide guidelines to improve the levelness of the dye distribution in the fabric material.     

Thermal error analysis for a CNC lathe feed drive system

The development of high-speed feed drive systems has been a major issue in the machine tool industry for the past few decades. The resulting reduction in the time needed for tool changes and the rapid travel time can enhance productivity. However, a high-speed feed drive system naturally generates more heat and resultant thermal expansion, which adversely affects the accuracy of machined parts. This paper divides the feed drive system into two parts: the ball screw and the guide way. The thermal behavior model for each part is developed separately, in order to estimate the position errors of the feed drive system caused by thermal expansion. The modified lumped capacitance method (MLCM) and genius education algorithm (GEA) are used to analyse the linear positioning error of the ball screw. Thermal deformation of the guide way affects straightness and introduces angular errors, as well as affecting linear positioning. The finite element method is used to estimate the thermal behavior of the guide way. The effectiveness of the proposed models is verified through experiments using a laser interferometer.