Sailong Xu

One-step hydrothermal crystallization of a layered double hydroxide/alumina bilayer film on aluminum and its corrosion resistance properties.

A zinc-aluminum layered double hydroxide (ZnAl-LDH)/alumina bilayer film has been fabricated on an aluminum substrate by a one-step hydrothermal crystallization method. The LDH film was uniform and compact. XRD patterns and SEM images showed that the LDH film was highly oriented with the c-axis of the crystallites parallel to the substrate surface. The alumina layer existing between the LDH film and the substrate was formed prior to the LDH during the crystallization process. Polarization measurements showed that the bilayer film exhibited a low corrosion current density value of 10(-8) A/cm(2), which means that the LDH/alumina bilayer film can effectively protect aluminum from corrosion. Electrochemical impedance spectroscopy (EIS) showed that the impedance of the bilayer was 16 MOmega, meaning that the film served as a passive layer with a high charge transfer resistance. The adhesion between the film and the substrate was very strong which enhances its potential for practical application.

Morphologies, Preparations and Applications of Layered Double Hydroxide Micro-/Nanostructures

Layered double hydroxides (LDHs), also well-known as hydrotalcite-like layered clays, have been widely investigated in the fields of catalysts and catalyst support, anion exchanger, electrical and optical functional materials, flame retardants and nanoadditives. This feature article focuses on the progress in micro-/nanostructured LDHs in terms of morphology, and also on the preparations, applications, and perspectives of the LDHs with different morphologies.

Facile synthesis of NiAl-layered double hydroxide/graphene hybrid with enhanced electrochemical properties for detection of dopamine

Layered double hydroxides (LDHs), also known as hydrotalcite-like anionic clays, have been investigated widely as promising electrochemical active materials. Due to the inherently weak conductivity, the electrochemical properties of LDHs were improved typically by utilization of either functional molecules intercalated between LDH interlayer galleries, or proteins confined between exfoliated LDH nanosheets. Here, we report a facile protocol to prepare NiAl-LDH/graphene (NiAl-LDH/G) nanocomposites using a conventional coprecipitation process under low-temperature conditions and subsequent reduction of the supporting graphene oxide. Electrochemical tests showed that the NiAl-LDH/G modified electrode exhibited highly enhanced electrochemical performance of dopamine electrooxidation in comparison with the pristine NiAl-LDH modified electrode. Results of high-resolution transmission electron microscopy and Raman spectra provide convincing information on the nanostructure and composition underlying the enhancement. Our results of the NiAl-LDH/G modified electrodes with the enhanced electrochemical performance may allow designing a variety of promising hybrid sensors via a simple and feasible approach.

Conformational Changes in Mannan-Binding Lectin Bound to Ligand Surfaces

The binding of soluble proteins to target surfaces is vital in triggering the immune response. However, structural insight into such processes is still lacking. Mannan-binding lectin (MBL) is a classic example of a pattern recognition molecule with important roles in innate immunity against microbial infections. By small angle x-ray scattering analysis we show that the large MBL complex in solution is folded into a ramified structure with a striking rotational symmetry and a structure permissive of elongation by unbending. Nevertheless, the structure in solution is found to be very stable. However, when the MBL molecule interacts with surface-immobilized ligands, the stable MBL structure is broken into a stretched state with separation of the ligand-binding domains as shown by high resolution atomic force microscopy. These studies provide a snapshot of the single molecule mechanics of MBL and the first direct evidence that the transition from the soluble state to surface-bound protein involves large conformational changes in the quaternary structure, thus highlighting the role of surface topography in immune recognition.

AFM-based force spectroscopy measurements of mature amyloid fibrils of the peptide glucagon

We report on the mechanical characterization of individual mature amyloid fibrils by atomic force microscopy (AFM) and AFM-based single-molecule force spectroscopy (SMFS). These self-assembling materials, formed from the 29-residue amphiphatic peptide hormone glucagon, were found to display a reversible elastic behaviour. Based on AFM morphology and SMFS studies, we suggest that the observed elasticity is due to a force-induced conformational transition which is reversible due to the β-helical conformation of protofibrils, allowing a high degree of extension. The elastic properties of such mature fibrils contribute to their high stability, suggesting that the internal hydrophobic interactions of amyloid fibrils are likely to be of fundamental importance in the assembly of amyloid fibrils and therefore for the understanding of the progression of their associated pathogenic disorders. In addition, such biological amyloid fibril structures with highly stable mechanical properties can potentially be used to produce nanofibres (nanowires) that may be suitable for nanotechnological applications.

Enhanced photocatalytic performances of hierarchical ZnO/ZnAl2O4 microsphere derived from layered double hydroxide precursor spray-dried microsphere.

Layered double hydroxides (LDHs), also called hydrotalcites, have been widely investigated for degradation of dye molecules, in the forms of direct photocatalysts, supports or precursors to ZnO-containing photocatalysts. LDH precursor-derived ZnO/ZnAl2O4 photocatalytic nanostructures have hitherto been created, involving ZnO/ZnAl2O4 powder and templated hierarchical frameworks with laboratory-scale preparations. We herein report a scalable preparation of ZnO/ZnAl2O4 microsphere derived from ZnAl-LDH precursor spray-dried microsphere. Survey of textural properties shows that ZnO/ZnAl2O4 microspheres maintain the hierarchically spherical feature and the relatively large surface area. Photocatalytic evaluation under UV irradiation shows that the ZnO/ZnAl2O4 microspheres exhibit highly enhanced photodegradation performance to methylene blue (MB) in comparison with the commercial ZnO powder. A preferential photodegradation to methyl orange (MO) of the MO/MB mixture was also observed, which was illustrated experimentally in terms of the favorable interaction and distribution between basic MO molecules and the acidic-site ZnO/ZnAl2O4 photocatalyst. Our results may initiate large-scale production of microspheres with promising photocatalytic performances.

Eco-efficient synthesis route of carbon-encapsulated transition metal phosphide with improved cycle stability for lithium-ion batteries

An eco-efficient synthesis route is developed to prepare carbon-encapsulated Ni3P nanoparticles embedded in carbon nanosheets as a cycling-stable anode material for lithium ion batteries. The green method is achieved by calcining the precursor of intercalated sodium dodecyl phosphate/Ni(OH)2, and is readily extended to prepare the transition metal sulphide by altering the intercalated surfactant.

Preparation of microspherical α-zirconium phosphate catalysts for conversion of fatty acid methyl esters to monoethanolamides

The performance of solid catalysts and catalyst supports is generally believed to be dependent on their morphology, surface area, and architecture. In order to fully exploit their attractive properties in actual practical applications, layered zirconium phosphate materials should be fabricated into macroscopic form. Here, we report the fabrication of microscopic spheres of alpha-zirconium phosphate (alpha-ZrP) by a spray-drying process. The layered alpha-ZrP nanoparticles were originally obtained using a synthesis route involving separate nucleation and aging steps (SNAS). The resulting products are composed of nanosize alpha-ZrP particles aggregated into solid microspheres with a diameter of 5-45 microm and a sphericity of 0.80. After calcination at 573 K, surface area of 43.8 m(2)/g could be obtained for alpha-ZrP microspheres, which is larger than that of the alpha-ZrP powder after similar thermal treatment (36.2 m(2)/g). Furthermore, the number of acidic sites of the alpha-ZrP microspheres is greater than for the alpha-ZrP powder due to its unique textual properties and higher surface area. The acylation reaction of fatty acid methyl esters (methyl stearate) with ethanolamine to form monoethanolamides was chosen as a probe reaction to evaluate the catalytic activity of the resulting microspherical alpha-ZrP materials, which showed high activity compared to the sample in the form of powders, with about 92.9% methyl stearate conversion at 393 K for 12 h. The enhanced performance in the reaction is determined by the large surface area and the increased number of acidic sites in the multiple-scales porosity of alpha-ZrP microspheres.

In Situ Crystallized Zirconium Phenylphosphonate Films with Crystals Vertically to the Substrate and Their Hydrophobic, Dielectric, and Anticorrosion Properties

The in situ crystallization technique has been utilized to fabricate zirconium phenylphosphonate (ZrPP) films with their hexagonal crystallite perpendicular to the copper substrate. The micro/nano roughness surface structure, as well as the intrinsic hydrophobic characteristic of the surface functional groups, affords ZrPP films excellent hydrophobicity with water contact angle (CA) ranging from 134 degrees to 151 degrees , without any low-surface-energy modification. Particularly, in the corrosive solutions such as acidic or basic solutions over a wide pH from 2 to 12, no obvious fluctuation in CA was observed for all the ZrPP film. The k values of the hydrophobic ZrPP films are in the low-k range (k < 3.0), meeting the development of ultra-large-scale integration (ULSI) circuits. The hydrophobicity feature is proposed to bear ZrPP film a more stable low-k value in an ambient atmosphere. Besides, the polarization current of ZrPP films is reduced by 2 orders of magnitude, compared to that of the untreated copper substrate. Even deposited in a vacuum oven for 30 days at room temperature, ZrPP films also show excellent corrosion resistance, indicating a stable anticorrosion property.

Synergistic lithium storage of a multi-component Co2SnO4/Co3O4/Al2O3/C composite from a single-source precursor

Endowing multi-component anode nanomaterials for lithium-ion batteries (LIBs) with integrated features for synergistically enhancing electrochemical performance is challenging via a simple preparation method. We herein describe an easy approach for preparing a multi-component Co2SnO4/Co3O4/Al2O3/C composite as the anode nanomaterial for LIBs, derived from a laurate anion-intercalated CoAlSn-layered double hydroxide (CoAlSn-LDH) single-source precursor. The resultant Co2SnO4/Co3O4/Al2O3/C electrode delivers a highly enhanced reversible capacity of 1170 mA h g−1 at 100 mA g−1 after 100 cycles, compared with the bi-active composites designed without Al2O3 or carbon (Co2SnO4/Co3O4/C, Co2SnO4/Co3O4/Al2O3, and Co2SnO4/Co3O4) which are easily derived through the same protocol by choosing LDH precursors without Al cation or surfactant intercalation. The distinctly different cycling stability and rate capability of Co2SnO4/Co3O4/Al2O3/C among the different composite electrodes suggest that the high enhancement could result from the following synergistic features: the combined conversion and alloying reactions of bi-active Co2SnO4/Co3O4 during cycling, the buffering role of non-active Al2O3 and carbon, and the improved conductivity of the self-generated carbon matrix. The LDH precursor-based approach may be extended to the design and preparation of various multi-component transition metal oxide composite nanomaterials for synergistic lithium storage.