Arsonic Acid As a Robust Anchor Group for the Surface Modification of Fe₃O₄

In order to use iron oxide nanoparticles (Fe₃O₄) in various applications, a surface modification that provides colloidal stability and additional functionality to the nanoparticles is necessary. For the modification of the nanoparticle surface with ligand molecules, the ligand molecule should contain an anchor group that has a strong affinity for the surface. However, currently used anchor groups have shown some problems such as low affinity and stability as well as reactivity with the surface. In this study, arsonic acid (RAsO­(OH)₂) was investigated as a novel anchor group. It was possible to introduce azide groups on the surface of iron oxide nanoparticles using 4-azidophenylarsonic acid, and the desired functional molecules could be chemically attached to the surface via copper-catalyzed azide–alkyne cycloaddition (click chemistry). By quantifying and comparing the amount of attached anchors on the surface, it was found that arsonic acid displays better affinity than other currently used anchors (catechol, carboxylic acid). Furthermore, we examined the binding reversibility, long–term anchoring stability, and anchoring stability at various pH values. It was revealed that arsonic acid is a stable anchor in various conditions

Surface Coating of Gradient Alloy Quantum Dots with Oxide Layer in White-Light-Emitting Diodes for Display Backlights

Recently, quantum dots (QDs) have been successfully developed as efficient color converters for light-emitting diodes (LEDs) display due to excellent optical properties of QDs. Herein, we demonstrate a new approach to form metal oxide layers (or metal oxide coating) on the exterior surface of gradient alloy QDs (the most advanced chemical architecture QDs developed thus far wherein the lattice parameter from the core to shell is changing in a gradient fashion) in order to improve the photochemical stability and photoluminescence efficiency. The resulting CdO-treated QDs are incorporated into polymer matrix films to fabricate a backlight unit as a part of display panel wherein CdO-treated gradient alloy QDs are utilized as color converters upon the blue-LED excitation. The fabricated 9.7 in. iPad 2 tablet liquid crystal display panel exhibited an excellent uniformity in terms of CIE chromaticity, luminance, and bright variation and superb durability test results (maintenance of ca. 110% brightness compared to initial value even after 3 weeks of operation)

Highly efficient Blue-Emitting CdSe-derived Core/Shell Gradient Alloy Quantum Dots with Improved Photoluminescent Quantum Yield and Enhanced Photostability

Highly efficient blue-emitting CdSe-derived core/shell gradient alloy quantum dots (CSGA QDs) with photoluminescence quantum yield (PL QY) of ca. 90% have been synthesized through a facile “one-pot” approach. CdSe nuclei are initially formed as core and gradient alloy shells such as CdSe_<i>x</i>S_1–<i>x</i>/ZnSe_<i>y</i>S_1–<i>y</i> simultaneously encapsulate the preformed CdSe core in an energy-gradient fashion eventually followed by coating with ZnS shells due to the faster precursor reaction kinetics of Cd and Se compared to analog of Zn and S. During the formation of core/shell structure, red-shifting of absorption/emission peaks followed by blue-shifting of analogues were observed due to the intradiffusion of sulfur anion to CdSe luminescent center. In this gradient architecture, interfacial lattice strain can be effectively alleviated, and thus high PL QY (ca. 90%) and enhanced photochemical stability can be achieved. The synthesized blue-emitting gradient alloy QDs with superior optical properties tunable in the range of 450–490 nm can be used for highly efficient blue-emitters and potentially applicable for the fabrication of white-light LEDs

Rapid Imaging of Latent Fingerprints Using Biocompatible Fluorescent Silica Nanoparticles

Fluorescent silica nanoparticles (FSNPs) are synthesized through the Stöber method by incorporating silane-modified organic dye molecules. The modified fluorescent organic dye molecule is able to be prepared by allylation and hydrosilylation reactions. The optical properties of as-prepared FSNPs are shown the similar optical properties of PR254A (allylated Pigment Red 254) and have outstanding photostability. The polyvinyl­pyrrolidone (PVP) is introduced onto the surface of FSNP to enhance the binding affinity of PVP-coated FSNP for latent fingerprints (LFPs) detection. The simple preparation and easy control of surface properties of FSNPs show potential as a fluorescent labeling material for enhanced latent fingerprint detection on hydrophilic and hydrophobic substrates in forensic science for individual identification

Variation in Crystalline Phases: Controlling the Selectivity between Silicon and Silicon Carbide via Magnesiothermic Reduction using Silica/Carbon Composites

Magnesiothermic reduction of various types of silica/carbon (SiO₂/C) composites has been frequently used to synthesize silicon/carbon (Si/C) composites and silicon carbide (SiC) materials, which are of great interest in the research areas of lithium-ion batteries (LIBs) and nonmetal oxide ceramics, respectively. Up to now, however, it has not been comprehensively understood how totally different crystal phases of Si or SiC can result from the compositionally identical parent materials (SiO₂/C) via magnesiothermic reduction. In this article, we propose a formation mechanism of Si and SiC by magnesiothermic reduction of SiO₂/C; SiC is formed at the interface between SiO₂ and carbon when silicon intermediates, mainly <i>in situ</i>-formed Mg₂Si, encounter carbon through diffusion. Otherwise, Si is formed, which is supported by an <i>ex situ</i> reaction between Mg₂Si and carbon nanosphere that results in SiC. In addition, the resultant crystalline phase ratio between Si and SiC can be controlled by manipulating the synthesis parameters such as the contact areas between silica and carbon of parent materials, reaction temperatures, heating rates, and amount of the reactant mixtures used. The reasons for the dependence on these synthesis parameters could be attributed to the modulated chance of an encounter between silicon intermediates and carbon, which determines the destination of silicon intermediates, namely, either thermodynamically preferred SiC or kinetic product of Si as a final product. Such a finding was applied to design and synthesize the hollow mesoporous shell (ca. 3–4 nm pore) SiC, which is particularly of interest as a catalyst support under harsh environments

Elucidating Relationships between Structural Properties of Nanoporous Carbonaceous Shells and Electrochemical Performances of Si@Carbon Anodes for Lithium-Ion Batteries

The encapsulation of silicon in hollow carbonaceous shells (Si@C) is known to be a successful solution for silicon anodes in Li-ion batteries, resulting in many efforts to manipulate the structural properties of carbonaceous materials to improve their electrochemical performance. In this regard, we demonstrate in this work how both the shell thickness and pore size of nanoporous carbonaceous materials containing silicon anodes influence the electrochemical performance. Structurally well-defined Si@C materials with varying carbon-shell thicknesses and pore sizes were synthesized by a nanocasting method that manipulated the carbon shell and by a subsequent magnesiothermic reduction that converted the amorphous silica cores into silicon nanocrystals. When these materials were employed as anodes, it was verified that two opposite effects occur with respect to the thickness of carbon shell: The weight ratio of silicon and the electrical conductivity are simultaneously affected, so that the best electrochemical performance is not obtained from either the thickest or the thinnest carbon shell. Such countervailing effects were carefully confirmed through a series of electrochemical performance tests and the use of electrochemical impedance spectroscopy. In addition, the effect of pore size was elucidated by comparing Si@C samples with different pore sizes, revealing that larger pores can further improve the electrochemical performance as a result of enhanced Li-ion diffusion

Bio-Inspired, Melanin-Like Nanoparticles as a Highly Efficient Contrast Agent for <i>T</i>₁‑Weighted Magnetic Resonance Imaging

The development of nontoxic and biocompatible imaging agents will create new opportunities for potential applications in clinical MRI diagnosis. Synthetic melanin-like nanoparticles (MelNPs), analogous to natural sepia melanin (a major component of the cuttlefish ink), can be used as contrast agent for MRI. MelNPs complexed with paramagnetic Fe³⁺ ions show much higher relaxivity values than existing MRI <i>T</i>₁ contrast agents based on gadolinium (Gd) or manganese (Mn); MelNP values at 3T were <i>r</i>₁ = 17 and <i>r</i>₂ = 18 mM^–1 s^–1 (<i>r</i>₂/<i>r</i>₁ value of 1.1). With significant enhancement to MRI contrast, this biomimetic approach using MelNPs functionalized with paramagnetic Fe³⁺ ions and surface-modified with biocompatible poly­(ethylene glycol) units, could provide new insight into how melanin-based bioresponsive and therapeutic imaging probes integrate with their various biological functions

Phase contrast microscope images of the PVS.

<p>A: The fluorescent image of the FNPs that were injected at a PN located about the CV4 and flowed in a PVS buried in the adipose tissue of the AWFB. It flowed up to the CV 14 and reemerged to the abdominal cavity toward the liver surface. The flow line was barely visible under the stereo fluorescence microscope. B & C: Phase contrast microscope images of the bright mode (B) and fluorescent mode (C) of the boxed region in (A). The PV (dashed arrow) running parallel to and above the blood vessel (two arrows) is hardly visible in (B) but clearly observable with fluorescence of FNPs in the panel (C). This primo vessel is the first observation of the so called extra vascular PVS. It runs closely along the blood vessel. The AWFB is clearly seen in (B) and its boundary is depicted with two curves in (C). The boundary of the abdominal wall fat band is indicated with two yellow curves. 40x. D & E: The PN is not noticeable without the fluorescence in (D), but manifestly appears with fluorescent view in the panel (E). The size of the PN was 250 μm. The fluorescent nanoparticles were highly concentrated in the PN. 40x</p

Mast cells in the PN.

<p><b>A:</b> The fluorescence of FNPs indicates the location of a PN (arrow). <b>B</b>: The toluidine blue staining cannot distinguish the parietal peritoneum and the PN. It showed the presence of mast cells (broken arrows) in the PN. The PN was torn off from the peritoneum during the sectioning process. <b>C</b>: An intact PN stained with toluidine blue was obtained. The overview of an AWFB-section shows a PN which are well kept just inside the parietal peritoneum. A lymph node (LN), blood vessels (BV), adipose tissues and parietal peritoneum (PP) are also seen showing their relative locations. It is a rare and fortunate case that a lymph node and a PN located nearby was found as presented in this figure. <b>D</b>: A magnified view shows that the cells in the lymph node and the PN look different. In fact, there were no mast cells in the lymph node and but many in the PN. <b>E</b>: A further magnified image depicts clearly the distribution of mast cells (*). The toluidine blue staining can be used for identifying the PN by revealing the abundance of mast cells even though it could not distinguish the collagens of the PN and surrounding connective tissues.</p

The anatomical position of the novel flowing duct in the abdominal wall fat band.

<p>A: Schematic illustration showing the location of linea alba and the conception vessel CV in the abdominal skin side. The broken line is the surgery cutting line of the abdominal wall. The line is in the right hand side from the linea alba in order to avoid cutting the PVS in the AWFB. The FNPs that were injected to a PN entered the AWFB and appeared at the terminal point to be continued to the PVS on the liver surface. B: The blood vessels in the AWFB inside the parietal peritoneum of the abdominal wall. The locations CV 8 to 14 are mere markings for positional references and not real CV-acupoints. Note that the CV8 corresponds to the umbilicus and the parietal peritoneum continues down to the ligament wrapping the bladder. C: A PV (arrow) emerged from the AWFB (double arrows) was raised tautly with a forceps.</p