Mami Yamada

Simple synthesis of three primary colour nanoparticle inks of Prussian blue and its analogues

Historic Prussian blue (PB) pigment is easily obtained as an insoluble precipitate in quantitative yield from an aqueous mixture of Fe3+ and [FeII(CN)6]4? (Fe2+ and [FeIII(CN)6]3?). It has been found that the PB pigment is inherently an agglomerate of 10?20?nm nanoparticles, based on powder x-ray diffraction (XRD) line broadenings and transmission electron microscopy (TEM) images. The PB pigment has been revived as both organic-solvent-soluble and water-soluble nanoparticle inks. Through crystal surface modification with aliphatic amines, the nanoparticles are stably dispersed from the insoluble agglomerate into usual organic solvents to afford a transparent blue solution. Identical modification with [Fe(CN)6]4? yields water-soluble PB nanoparticles. A similar ink preparation is applicable to Ni-PBA and Co-PBA (nickel and cobalt hexacyanoferrates). The PB (blue), Ni-PBA (yellow), and Co-PBA (red) nanoparticles function as three primary colour inks.

Electrochromic Thin Film of Prussian Blue Nanoparticles Fabricated using Wet Process

Electrochromic thin films of Prussian blue nanoparticles were developed using wet processing. The resultant alkyl-ligand covered nanoparticles disperse well in organic solvents. Consequently, various conventional coating and printing methods can be used in high-quality micro-fabrication to prepare electronic devices. We examined electrochromic properties of the thin film fabricated using spin-coating method. Electrochromism of the thin film on an indium tin oxide (ITO) electrode was observed. The color changes from blue to colorlessness reversibly at potentials between +0.6 to -0.4 V. Furthermore, various patterns were printed on ITO substrates using photolithography, indicating potential application of this approach to information displays and smart windows.

Estimation of Surface Structure and Carbon Monoxide Oxidation Site of Shape-Controlled Pt Nanoparticles

Surface structures of shape-controlled Pt nanoparticles have been estimated using cyclic voltammetry (CV) and infrared reflection absorption spectroscopy (IRAS). Cubic and cuboctahedral Pt nanoparticles are prepared using a capping polymer. These nanoparticles give CVs similar to those of single crystal electrodes of Pt in sulfuric acid solution. The CV of cubic nanoparticles is similar to that of the Pt(510) [=5(100)-(110)] electrode, while the CV of cuboctahedral nanoparticles is reproduced well with the convolution of Pt(766) [=13(111)-(100)] and Pt(17 1 1) [=9(100)-(111)] electrodes. These results suggest that the planes of the cubic and cuboctahedral nanoparticles are composed of step-terrace and atomically flat terraces, respectively. Adsorbed carbon monoxide (CO) on the shape-controlled nanoparticles gives the IR bands that are assigned to on-top and bridged CO. The band of on-top CO is deconvoluted to two bands: the higher and the lower frequency bands are assigned to the CO on the plane and the edges of the nanoparticles, respectively. On-top CO adsorbed on the edges is oxidized at more negative potential than that on the planes. Edge sites of the nanoparticles promote CO oxidation.

Fabrication of a tubular FeCo bimetallic nanostructure using a cellulose–cobalt hexacyanoferrate composite as a precursor

A tubular fibre structure with a ca. 9-11 microm outer diameter comprised of FeCo nanoparticle assemblies with an amorphous carbon core was fabricated via reductive thermal decomposition of a cellulose-cobalt hexacyanoferrate (Fe-CN-Co) composite material.