Shape Of Nanoplates Research Articles

Shape-controlled synthesis of Pt nanoframes

Plate-like Pt nanoframes were synthesized using Au nanoplates as a template, followed by formation of a Ag layer coating on the Au template, and selective chemical etching of Au and Ag leaving the Pt structure intact. Circular, triangular, and hexagonal Au nanoplates successfully served as templates for fabrication of various Pt nanoframe shapes, which resembled the original Au nanoplate shape. A thin Ag layer was found to play a critical role as an electron-transfer mediator in the galvanic replacement reaction between the thin Ag layer on Au nanoplates and Pt precursors. During the replacement reaction, the Pt layer grew faster at the {112} edges than at the {111} terraces of Au nanoplates. The thicker periphery of the nanoplates survived the chemical etching step, while the thinner center was etched, leading to formation of Pt nanoframes in high yield and good homogeneity.

Effect of surface-topology on magnetic properties in (La0.6Eu0.4)0.67Ca0.33MnO3 of anisotropic shape of nanoplates

(La0.6Eu0.4)0.67Ca0.33MnO3 has been prepared in the shape of nanoplates of single crystallites (an orthorhombic structure) through polymer templates. HRTEM images reveal 18, 25, and 30nm thicknesses of plates after heating a precursor powder at 873, 1073, and 1273K in air for 2h. These values present average crystallite size determined from broadening of the X-ray diffraction peaks. A spin-glass-like surface (GS) overlayer (3–5nm thickness) in such plates facilitates a ferromagnetic→ferrimagnetic reordering with markedly suppressed Curie point TC, i.e., as small as 90K in a 873K heated sample, from the parent value 268K. The TC point increases to 103K (or 120K) when heating at higher temperature 1073 (or 1273K), during which the core grows at the expense of the overlayer. The GS tailors as high coercivity Hc as 617Oe in the zero field cooled (ZFC) sample that is decreased to 500Oe in the field cooled (FC) sample in the surface spin-freezing along the field direction. The Hc-value (ZFC) that steps down successively to 252Oe on the overlayer is thinned down by heating at 1273K. Samples heated at 873, 1073, or 1273K have regularly increased saturation magnetization 35.3, 63.9, or 69.6emu/g in ZFC, while 43.7, 70.2, or 75.5emu/g in FC measured at 10K. The ferrimagnetic reordering are described based on the scenario of an antiferromagnetic exchange coupling between the Eu3+ and Mn3+ (or Mn4+) sublattices.

Isothermal crystallization of polyethylene oxide/silver nanoplate composites

AbstractThis research was accomplished to investigate the kinetics of isothermal crystallization of polyethylene oxide (PEO)/silver nanoplate composites. It was obtained that the spherulites increased in size and numbers with time for the composites with various particle loadings. Additionally, the spherulite growth rate of composites decreased with an increase in the crystallization temperature and increased with the addition of nanoplates. The spherulite growth rate was further analyzed by the theory developed by Lauritzen and Hoffman. The product of the lateral surface free energy (σ) and the end surface free energy (σe) decreased with an increase in the content of nanoplates. We proposed the possible crystallization mechanisms of these PEO/nanoplate composites according to the change of σ and σe with the presence of nanoplates. A controlled experiment showed a minor change in PEO crystallization with the presence of a surfactant C16TAB. This implied that the unique size and shape of nanoplates plays a key role on hindering the primary nucleation of PEO and increasing the spherulite growth rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis, Stabilization, and Functionalization of Silver Nanoplates for Biosensor Applications

Silver nanoplates (NPTs) were prepared by a seed-mediated growth method with different diameters (d = 25, 32, 53, and 100 nm) and with thicknesses of approximately 10 nm in all cases. As the concentration of silver seeds increased, the diameter of the nanoplates increased, resulting in an overall shift in the localized surface plasmon resonance (LSPR) band maximum from 570 to 900 nm, thus providing a novel method to tune the plasmon resonance. The LSPR was calculated from theory for both triangular and circular nanoplate geometries. In agreement with transmission electron micrographs, the model results confirmed the shape of nanoplates as being truncated prisms, intermediate between that of a prism and a disk. Because of the toxicity of the surfactant hexadecyltrimethylammonium bromide (CTAB), the stabilizing CTAB bilayer surrounding the NPT was replaced by a nontoxic alkanethiol with surfactant properties. This enabled the extraction of metal nanoparticles into deionized water or buffer for bioconjugation without aggregation. Silver nanoplates were also coated with polyelectrolyte layers using the standard layer-by-layer (LbL) method. The LSPR was found to be very sensitive to the addition of polyelectrolyte layers, with a plasmon band shift from 728 to 740 nm after adding only one monolayer (thickness ∼1.5 nm). Bioconjugation of these nanoplates was achieved with the addition of a mercaptolinker containing a carboxyl group. The carboxyl groups were activated with 1-ethyl-3-(3-dimethylaminopropyl) hydrochloride (EDC)/N-hydroxysuccinimide (NHS) and conjugated to green fluorescent protein (GFP) in order to validate the potential of the NPTs for enhancement of bioassays. The fluorescence of the conjugated NPTs was 5.6-fold brighter than that of NPTs added to GFP without activation.

Synthesis of SnNb2O6 Nanoplates and Their Photocatalytic Properties

Abstract The visible light-driven photocatalyst SnNb2O6 was synthesized by reacting Sr2Nb2O7 with molten SnCl2 at 573 K. SEM observations revealed that the SnNb2O6 sample had a surface area of 56 m2 g−1, with particles having a nanoplate shape, a thickness of ca. 10 nm and widths of several hundred nm. A Pt-loaded SnNb2O6 nanoplate sample showed photocatalytic activity for H2 evolution from an aqueous methanol solution under visible light irradiation.