Geometrical Separation of Defect States in ZnO Nanorods and Their Morphology-Dependent Correlation between Photoluminescence and Photoconductivity

An understanding of the morphology-dependent correlation between photoluminescence and photoconductivity in nanostructured ZnO is important for elucidating the carrier dynamics and expanding its use in optoelectrical applications. In this study, we investigated this relationship using distinctly different ZnO nanorods with diameters greater than 100 nm, which were produced by a hydrothermal method. Furthermore, in order to study the effects of its defect states on the correlation, we thoroughly characterized the defect states of the ZnO nanorods in terms of the light-penetration depth during photoluminescence. The photoconductivities of the nanorods were measured using light sources with wavelengths of 355, 405, and 532 nm to confirm the influences of the visible-emission-generating defects on carrier transport. We found that the intensity of the near-band-edge emission was almost comparable to the amount of photocurrent generated under ultraviolet (UV) light; this could be attributed to the crystallinity of the inside of ZnO nanorods. However, the concentration of the surface defects resulting from the size and morphology probably had an effect, leading to the observed differences in the photocurrent sensitivity under low-intensity UV light, the dark current level, the amount of photocurrent under a specific wavelength of light within the visible range, and the persistent photoconductivity. The results of this study could aid research on carrier dynamics in nanostructured ZnO and further its use in optoelectronics

Effect of the Addition of Mesogenic Thiol Ligand Modified Gold Nanoparticles on the Thermal Stabilization of Blue Phases

<div><p>In this paper, we introduce surface modified gold nanoparticles with mesogenic thiol ligands in liquid crystal, for expansion of the temperature range of blue phases (BPs). We have used polarized optical microscope and UV-vis spectrophotometer to identify the thermal stabilization of BPs. The BPs range of nanoparticles doped liquid crystal is significantly dependent upon the addition amount of gold nanoparticles, and the molar ratios of attached ligands [4′-(10-mercaptodecyloxy)biphenyl-4-carbonitrile and dodecanethiol]. This study could provide a new and facile strategy to stabilize BPs, from the aspect of the surface modification of nanoparticles.</p></div

Nonmonotonic Size-Dependent Carrier Mobility in PbSe Nanocrystal Arrays

On the basis of a tight binding system-bath model, we investigated carrier mobility of PbSe nanocrystal (NC) arrays as a function of NC size and inter-NC separation. The size-dependent trend of calculated carrier mobilities are in excellent agreement with recent experimental measurements: electron mobility increased up to NC diameter of ∼6 nm and then decreased for larger NCs, whereas hole mobility showed a monotonic size-dependency. Carrier mobility increase was associated with reduced activation energy that governs charge-transfer processes. In contrast, the decrease in electron mobility for large NCs was found to be due to smaller electronic coupling. Control of inter-NC separation is crucial for mobility enhancement: the mobility may change by an order of magnitude when inter-NC separation varies by as little as 1 to 2 Å. We anticipate similar size-dependency of the mobility in other semiconductor NC arrays, although crossover diameter in which mobility reaches its maximum depends on the material

Optimally Functionalized Adhesion for Contact Transfer Printing of Plasmonic Nanostructures on Flexible Substrate

This paper demonstrates a facile method to achieve high yield and uniform fabrication for the transfer printing of nanoplasmonic structures on a flexible substrate by providing novel understanding on adhesion layers. The mercapto alkyl carboxylic acids and the alkyl dithiols are used as functionalized adhesion layers and further optimized by controlling the terminal group as well as the length and composition of the functionalization on flat and nanostructured gold surfaces. Our approach of optimized adhesion has been successfully implemented to the transfer printing of functionalized gold nanostructure arrays, thus producing much higher yield of 97.6% and uniform fabrication of nanostructures on a flexible substrate and enabling applications such as flexible nanoplasmonic devices and biosensing platforms

Selective stabilisation of blue phase liquid crystal induced by distinctive geometric structure of additives

<p>We successfully stabilised liquid crystalline blue phases (BPs) by introducing two suitable additives with different geometric molecular structures, linear-shaped cobalt oleate complex (Co-OL) or tetrahedral-shaped tetraoctadecylammonium bromide (TODAB), into a liquid crystal (mixture of 4ʹ-pentyl-4-biphenylcarbonitrile, JC-1041XX and chiral dopant). The BPs temperature range and phase sequence depending on the addition amount and shape of additives were systematically investigated to determine the optimal concentration and shape dependency required to achieve a stabilising effect for BPs. From the polarising optical microscope results, the BPs temperature range for all of the samples with additives was not only broadened but also shifted to room temperature compared to that of BPs without additives. The widest BPs temperature range was increased to 15.3°C by the addition of 3 wt% Co-OL. According to the UV-vis reflection spectroscopy results, the Co-OL has a more significant stabilisation effect on BP I than on BP II, and the widest BP I range increases to 11.0°C. On the other hand, TODAB is effective for BP II stabilisation with the broadest BP II range reaching 1.8°C. These selective stabilisation effects are attributed to the specific shape of additives that closely match the structures of the disclination lines of the BPs.</p

Room-Temperature Compressive Transfer Printing of Nanowires for Nanoelectronic Devices

Recently, there has been a growing interest in the controlled alignment and robust bonding process of nanowires (NWs) on nanoelectronic devices. In this paper, we developed an innovative process for the fabrication of NW-based devices by room-temperature and low-pressure compressive transfer printing of NWs, in which NWs could be simultaneously aligned and bonded onto the metal electrodes. In this process, chemically synthesized NWs were first transferred and aligned on an intermediate substrate by contact printing and then finally printed onto a target substrate with mechanically soft Au electrodes, which enables the embedding of aligned NWs under low-pressure (5 bar) and room-temperature condition. The resulting contact between NW and Au electrodes exhibits Schottky behavior and high mechanical bonding strength (>567 MPa). The electrical characteristics could be converted from Schottky to Ohmic contact through thermal annealing treatment at 250 °C for 5 min due to Cr diffusion and direct Cr-ZnO contact formation. The applications of the fabricated devices as ultraviolet (UV) and gas sensors were successfully demonstrated. Furthermore, NW-based electronic devices were fabricated on a flexible substrate by using this process and showed mechanical and electrical robustness under mechanical bending conditions

Additional file 1: of Hierarchical Nanoflowers on Nanograss Structure for a Non-wettable Surface and a SERS Substrate

A movie of wetting test on hierarchical nanoflowers on nanograss structures. (MP4 9294 kb

Phthalate Levels in Nursery Schools and Related Factors

Phthalate esters, which are known endocrine disruptors, are ubiquitously present throughout indoor environments. Leaching from building materials may be a major source of phthalate esters. In this study, we evaluated phthalate ester concentrations in dust samples from 64 classrooms located in 50 nursery schools and explored the critical factors affecting phthalate concentrations, especially with regard to building materials. Dust was sampled by a modified vacuuming method, and building materials were assessed using a portable X-ray fluorescence (XRF) analyzer to determine whether they contained polyvinyl chloride. Di-<i>n</i>-butyl phthalate (DBP), di­(2-ethylhexyl) phthalate (DEHP), and di-isononyl phthalate (DINP) were the most frequently detected phthalates. Of these, DEHP was the most abundant phthalate, with a geometric mean of 3170 μg/g dust, and concentrations were significantly correlated with the area of polyvinyl chloride (PVC)-verified flooring. DINP, which has not been well-reported in other studies, was the second-most abundant phthalate, with a geometric mean of 688 μg/g dust, and showed a critical relationship with the number of children in the institution and the agency operating the nursery school. This is the first study to verify the sources of phthalates with an XRF analyzer and to evaluate the relationship between phthalate concentrations and PVC-verified materials

Lodopyridones D − G from a marine-derived bacterium Saccharomonospora sp.

The intensive investigation of chemical components from the culture broth of the bacterium Saccharomonospora sp. CNQ-490 has yielded four new natural products, lodopyridones D − G (1 − 4) along with the previously reported compounds, lodopyridones A − C (5 − 7) and cotteslosin A (8). The planar structures of the lodopyridones D − G (1 − 4) were elucidated by interpreting the mass spectrometry, ultraviolet (UV) spectroscopy, and 1D and 2D nuclear magnetic spectroscopy (NMR) data, as well as comparing NMR data with those of the lodopyridones A − C (5 − 7).</p

Additional file 1: of Quad-phased data mining modeling for dementia diagnosis

Table of Contents. Table A: The list of selected variables from proposer module. Table B: The list of patient groups from descriptor module. (DOCX 35 kb