Fabrication of hybrid graphene oxide/polyelectrolyte capsules by means of layer-by-layer assembly on erythrocyte cell templates

A novel and facile method was developed to produce hybrid graphene oxide (GO)–polyelectrolyte (PE) capsules using erythrocyte cells as templates. The capsules are easily produced through the layer-by-layer technique using alternating polyelectrolyte layers and GO sheets. The amount of GO and therefore its coverage in the resulting capsules can be tuned by adjusting the concentration of the GO dispersion during the assembly. The capsules retain the approximate shape and size of the erythrocyte template after the latter is totally removed by oxidation with NaOCl in water. The PE/GO capsules maintain their integrity and can be placed or located on other surfaces such as in a device. When the capsules are dried in air, they collapse to form a film that is approximately twice the thickness of the capsule membrane. AFM images in the present study suggest a film thickness of approx. 30 nm for the capsules in the collapsed state implying a thickness of approx. 15 nm for the layers in the collapsed capsule membrane. The polyelectrolytes used in the present study were polyallylamine hydrochloride (PAH) and polystyrenesulfonate sodium salt (PSS). Capsules where characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and Raman microscopy, the constituent layers by zeta potential and GO by TEM, XRD, and Raman and FTIR spectroscopies

Solid containing rotationally free nanocrystalline (Y-Fe2O3: Material for a nanosclae magnetic compass

A nanocomposite material has been characterized that contains nanometer size magnets that are free to rotate in response to an applied magnetic field. The composite consists of 5–10 nm crystals of γ-Fe2O3 dispersed in a solid methanol polymer matrix. The material was prepared by freezing a methanol-based ferrofluid of γ-Fe2O3 and subjecting it to a magnetic field applied in alternate directions to anneal the matrix. Before the field treatment, the solid displays magnetic behavior characteristic of an ordinary nanoscopic magnetic material. It is superparamagnetic above the blocking temperature (160 K) and hysteretic below, showing magnetic remanence and coercivity. After the field treatment to anneal the matrix, the same solid shows only Curie–Weiss behavior above and below the blocking temperature over the temperature range from 4.2 to 200 K and in response to applied magnetic fields as low as 1.59 kA/m. The data are consistent with a solid containing rotationally free, nanoscopic magnets encased in cavities of very small dimensions. The free rotation of the particles precludes the observation of magnetic relaxation phenomena that are characteristic of magnetic solids and ferrofluids. The present solid portends a class of magnetic materials with very little or no electrical and magnetic loss

Synthesis and Structural Characterization of a New Cyanomanganate(III) Complex, Heptapotassium µ-Oxo-bis[pentacyanomanganate(III)]cyanide

The final product resulting from the reaction of KMnO_4 and KCN in saturated aqueous solution is a gold-brown compound K_7[(CN)_5MnOMn(CN)_5]CN, as established by a single-crystal X-ray diffraction study. Full-matrix leastsquares refinement included anisotropic temperature parameters for all atoms and converged with a final R index (on F) of 0.091. The structure contains the oxo bridged [Mn_2O(CN)_(10)]^(6-) ion, which has 2/m crystallographic symmetry with the bridging oxygen atom lying at a center of symmetry. The ion exists in an eclipsed rotomeric configuration. The Mn-O distance is relatively short, 1.723 (4) Å. Crystallographically independent potassium ions are coordinated to the nitrogen ends of cyanide groups in trigonal prismatic, octahedral, and square antiprismatic geometries. Crystal data are as follows: orthorhombic; space group Ibɑm; ɑ = 12.397 (8), b = 12.772 (8), c = 14.618 (7) A (temperature 23°); Z = 4; d_(obsd) = 1.98, d_(calcd) = 1.97 g/cm^3. The synthesis, isolation, and physical characteristics of K_7[Mn_2O(CN)_(10)]CN are reported along with spectral and magnetic data. The principal features in the infrared spectrum are cyanide stretching bands centered around 2090 cm^(-1). The optical absorption spectrum in a KBr pellet consists of a primary band at 370 nm with a prominent shoulder at 410 nm and a weak shoulder at approximately 610 nm. The gold-brown crystals are strongly pleochroic, the crystals being colorless when the E vector is parallel to the long needle axis. This characteristic serves as a convenient means of identification for this substance. At room temperature K_7[Mn_2O(CN)_(10)]CN is diamagnetic

Study of 2D supramolecular self-assembled layers of phenyleneethynylene oligomers on HOPG by scanning tunneling microscopy

The type of supramolecular organization of conjugated macromolecules in solid state is an important feature to be considered for the optimization of optoelectronic properties of active layers for solar cells. We report on the scanning tunneling microscopy (STM) and small-wide angle X-ray scattering (SWAXS) study of four linear and rigid \u3c0-conjugated p-phenyleneethynylene (PPE) oligomers. The four compounds possess two dodecanoxy side chains in the central PPE moiety, and differ in conjugation length (3 and 5 phenyleneethynylene moieties). Two oligomers are benzyl (Bz3PEBz, Bz5PEBz) and two are carboxylic acid groups (Ac3PEAc, Ac5PEAc) end-capped. We found that in carboxylic acids terminated oligomers, a lineal type arrangement is obtained, likely due to the hydrogen bridge created between carboxylic acids; in contrast, for the benzylbenzoate terminated oligomers a rather step-wise arrangement is obtained, promoted by the \u3c0-\u3c0 interaction between benzyls. In general, all of the molecules form a lamellar like pattern adopting a face-on arrangement, where the conjugated backbones are flat-lying on the HOPG surface, whose distances correspond to the length of the conjugated backbone, while within the lamellas, a distance of 1.52 nm corresponds to the space between conjugated backbones; values that are consistent with those found by WAXS and DFT/6-311G(d,p) theoretical calculations, for oligomers that self-assemble with the interdigitated lateral alkyl chains