Nano-sized lithium manganese oxide dispersed on carbon nanotubes for energy storage applications

Nano-sized lithium manganese oxide (LMO) dispersed on carbon nanotubes (CNT) has been synthesized successfully via a microwave-assisted hydrothermal reaction at 200 °C for 30 min using MnO₂-coated CNT and an aqueous LiOH solution. The initial specific capacity is 99.4 mAh/g at a 1.6 C-rate, and is maintained at 99.1 mAh/g even at a 16 C-rate. The initial specific capacity is also maintained up to the 50th cycle to give 97% capacity retention. The LMO/CNT nanocomposite shows excellent power performance and good structural reversibility as an electrode material in energy storage systems, such as lithium-ion batteries and electrochemical capacitors. This synthetic strategy opens a new avenue for the effective and facile synthesis of lithium transition metal oxide/CNT nanocomposite.     

Tuning Local Coordination Environments of Manganese Single-Atom Nanozymes with Multi-Enzyme Properties for Selective Colorimetric Biosensing

Single-atom nanozymes (SAzymes) are promising in next-generation nanozymes, nevertheless, how to rationally modulate the microenvironment of SAzymes with controllable multi-enzyme properties is still challenging. Herein, we systematically investigate the relationship between atomic configuration and multi-enzymatic performances. The constructed Mn_SA−N₃-coordinated SAzymes (Mn_SA−N₃−C) exhibits much more remarkable oxidase-, peroxidase-, and glutathione oxidase-like activities than that of Mn_SA−N₄−C. Based on experimental and theoretical results, these multi-enzyme-like behaviors are highly dependent on the coordination number of single atomic Mn sites by local charge polarization. As a consequence, a series of colorimetric biosensing platforms based on Mn_SA−N₃−C SAzymes is successfully built for specific recognition of biological molecules. These findings provide atomic-level insight into the microenvironment of nanozymes, promoting rational design of other demanding biocatalysts.     

A Highly Sensitive Amperometric Galactose Biosensor Based on Graphene-doped Sol-gel-derived Titania-Nafion Composite Films

A highly sensitive amperometric galactose biosensor was developed by encapsulating galactose oxidase within the graphene-doped sol-gel titania-Nafion composite film on platinized glassy carbon electrode. Due to the combined electrocatalytic activity of graphene and Pt NPs on the electrode towards hydrogen peroxide as well as the mesoporous nature of the titania-Nafion composite, the present galactose biosensor exhibited relatively fast response time under 2 s, high sensitivity of 40.6 mAM⁻¹cm⁻², and wide dynamic range over three orders of magnitude with a detection limit of 3.78×10⁻⁶ M (S/N=3). In addition, the biocompatible composite in the biosensor secures excellent long-term stability.     

Tetrahedral atom ordering in a zeolite framework: a key factor affecting its physicochemical properties

Three gallosilicate natrolites with closely similar chemical composition but differing in the distribution of Si and Ga over crystallographically different tetrahedral sites (T-sites) show striking differences in their cation exchange performance. The ability to exchange Na(+) by the larger alkali metal cations decreases upon increasing the size of the cation, as expected, but also with the degree of T-atom ordering. To seek an insight into this phenomenon, the crystal structures of 11 different zeolites, which show variations in degree of T-atom ordering, nature of countercation, and hydration state, have been refined using synchrotron diffraction data. While the three as-made sodium materials were characterized to have a low, medium, and high degree of ordering, respectively, their pore sizes are close to the size of the bare Na(+) cation and much smaller than that of the larger alkali cations, which are nonetheless exchanged into the materials, each one at a different level. Interestingly, large differences are also manifested when the Na(+) back-exchange is performed on the dehydrated K(+) forms, with crystallographic pore sizes too small even to allow the passage of Na(+). Although the thermodynamic data point to small differences in the enthalpy of the Na(+)/K(+) exchange in the three materials, comparison of the "static" crystallographic pore sizes and the diameter of the exchanged cations lead us to conclude that during the exchange process these zeolites undergo significant deformations that dynamically open the pores, allowing cation traffic even for Cs(+) in the case of the most disordered material. In addition to the very large topological flexibility typical of the natrolite framework, we propose as a hypothesis that there is an additional flexibility mechanism that decreases the rigidity of the natrolite chain itself and is dependent on preferential siting of Si or Ga on crystallographically different T-sites.     

Dynamic cylindrical assembly of triblock copolymers by a hierarchical process of covalent and supramolecular interactions

We have developed a hierarchical process that combines linear triblock copolymers into concentric globular subunits through strong chemical bonds and is followed by their supramolecular assembly via weak noncovalent interactions to afford one-dimensionally assembled, dynamic cylindrical nanostructures. The molecular brush architecture forces triblock copolymers to adopt intramolecular interactions within confined frameworks and then drives their intermolecular interactions in the mixtures of organic solvent and water. In contrast, the triblock copolymers, when not preconnected into the molecular brush architectures, organize only into globular assemblies.     

Modulation of Foreign Body Reaction against PDMS Implant by Grafting Topographically Different Poly(acrylic acid) Micropatterns

The surface of poly(dimethylsiloxane) (PDMS) is grafted with poly(acrylic acid) (PAA) layers via surface‐initiated photopolymerization to suppress the capsular contracture resulting from a foreign body reaction. Owing to the nature of photo‐induced polymerization, various PAA micropatterns can be fabricated using photolithography. Hole and stripe micropatterns ≈100‐µm wide and 3‐µm thick are grafted onto the PDMS surface without delamination. The incorporation of PAA micropatterns provides not only chemical cues by hydrophilic PAA microdomains but also topographical cues by hole or stripe micropatterns. In vitro studies reveal that a PAA‐grafted PDMS surface has a lower proliferation of both macrophages (Raw 264.7) and fibroblasts (NIH 3T3) regardless of the pattern presence. However, PDMS with PAA micropatterns, especially stripe micropatterns, minimizes the aggregation of fibroblasts and their subsequent differentiation into myofibroblasts. An in vivo study also shows that PDMS samples with stripe micropatterns polarized macrophages into anti‐inflammatory M2 macrophages and most effectively inhibits capsular contracture, which is demonstrated by investigation of inflammation score, transforming‐growth‐factor‐β expression, number of macrophages, and myofibroblasts as well as the collagen density and capsule thickness.     

Imide-siloxane block copolymer/silica hybrid membranes: preparation, characterization and gas separation properties

Imide-siloxane block copolymer/silica hybrid membranes with covalent bonds were prepared via sol–gel reaction. The structural informations of these hybrid membranes were obtained by using Fourier transform-infrared spectrometry (FT-IR), ²⁹Si nuclear magnetic resonance (²⁹Si NMR), XPS and thermogravimetric analysis (TGA). The gas separation properties of the hybrid membranes were also investigated in terms of organosiloxane (PDMS) or silica content at various temperatures. In the hybrids, the addition of PDMS phase increased the permeabilities of gases such as He, CO₂, O₂, and N₂, indicating that the gas transport occurred mainly through rubbery organic matrix. Meanwhile, the PDMS phase contributed the decreased gas selectivities to nitrogen but the reduction in selectivities was very small in comparison with other siloxane containing polymeric membranes. This might be due to the restriction of chain mobility by the existence of inorganic component such as silica network in the hybrids. Additionally, the increase of silica content in these hybrid membranes considerably retarded the falling-off of gas selectivity at elevated temperature. The increase of silica content in hybrid membranes resulted in well-formed silica networks and hence these inorganic components restricted the plasticization of organic matrix by the thermal segmental motion of organic components, leading to preventing the large decrease of the gas selectivity.     

Carbonic Anhydrase Immobilized on Encapsulated Magnetic Nanoparticles for CO(2) Sequestration

Bovine carbonic anhydrase (BCA) was covalently immobilized onto OAPS (octa(aminophenyl)silsesquioxane)-functionalized Fe(3) O(4) /SiO(2) nanoparticles by using glutaraldehyde as a spacer. The Fe(3) O(4) nanoparticles were coated with SiO(2) , onto which was grafted OAPS, and the product was characterized using SEM, TEM, XRD, IR, X-ray photoelectron spectroscopy (XPS), and magnetometer analysis. The enzymatic activities of the free and Fe(3) O(4) /SiO(2) /OAPS-conjugated BCA (Fe?CA) were investigated by hydrolyzing p-nitrophenylacetate (p-NPA), and hydration and sequestration of CO(2) to CaCO(3) . The CO(2) conversion efficiency and reusability of the Fe?CA were studied before and after washing the recovered Fe?CA by applying a magnetic field and quantifying the unreacted Ca(2+) ions by using ion chromatography. After 30?cycles, the Fe?CA displayed strong activity, and the CO(2) capture efficiency was 26-fold higher than that of the free enzyme. Storage stability studies suggested that Fe?CA retained nearly 82?% of its activity after 30?days. Nucleation of the precipitated CaCO(3) was monitored by using polarized light microscopy, which revealed the formation of two phases, calcite and valerite, at pH?10 upon addition of serine. The magnetic nanobiocatalyst was shown to be an excellent reusable catalyst for the sequestration of CO(2.).     

Highly Stable,Water‐Dispersible Metal‐Nanoparticle‐Decorated Polymer Nanocapsules and Their Catalytic Applications

A facile synthesis of highly stable, water‐dispersible metal‐nanoparticle‐decorated polymer nanocapsules (M@CB‐PNs: M=Pd, Au, and Pt) was achieved by a simple two‐step process employing a polymer nanocapsule (CB‐PN) made of cucurbit[6]uril (CB[6]) and metal salts. The CB‐PN serves as a versatile platform where various metal nanoparticles with a controlled size can be introduced on the surface and stabilized to prepare new water‐dispersible nanostructures useful for many applications. The Pd nanoparticles on CB‐PN exhibit high stability and dispersibility in water as well as excellent catalytic activity and recyclability in carbon–carbon and carbon–nitrogen bond‐forming reactions in aqueous medium suggesting potential applications as a green catalyst.     

meso‐Ester and Carboxylic Acid Substituted BODIPYs with Far‐Red and Near‐Infrared Emission for Bioimaging Applications

A series of meso‐ester‐substituted BODIPY derivatives 1–6 are synthesized and characterized. In particular, dyes functionalized with oligo(ethylene glycol) ether styryl or naphthalene vinylene groups at the α positions of the BODIPY core ( 3 – 6 ) become partially soluble in water, and their absorptions and emissions are located in the far‐red or near‐infrared region. Three synthetic approaches are attempted to access the meso‐carboxylic acid (COOH)‐substituted BODIPYs 7 and 8 from the meso‐ester‐substituted BODIPYs. Two feasible synthetic routes are developed successfully, including one short route with only three steps. The meso‐COOH‐substituted BODIPY 7 is completely soluble in pure water, and its fluorescence maximum reaches around 650 nm with a fluorescence quantum yield of up to 15 %. Time‐dependent density functional theory calculations are conducted to understand the structure–optical properties relationship, and it is revealed that the Stokes shift is dependent mainly on the geometric change from the ground state to the first excited singlet state. Furthermore, cell staining tests demonstrate that the meso‐ester‐substituted BODIPYs ( 1 and 3 – 6 ) and one of the meso‐COOH‐substituted BODIPYs ( 8 ) are very membrane‐permeable. These features make these meso‐ester‐ and meso‐COOH‐substituted BODIPY dyes attractive for bioimaging and biolabeling applications in living cells.