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Relevant academic research and scientific papers

Photo-induced charge transfer in Prussian blue analogues as detected by photoacoustic spectroscopy

The photo-induced charge transfer in four series of Prussian blue (PB) analogues was studied from photoacoustic spectra. In cobalticyanides the observed signals were assigned to a metal-to-ligand charge transfer, which appears as a shoulder below 450 nm, and to d-d transitions for Co(II), Ni(II) and Cu(II) complex salts. No evidence of metal-to-metal charge transfer was observed for this series, which is probably due to the high stability of low spin cobalt(III) in the hexacyanide complex. Photoacoustic spectra for ferricyanides are broad bands, which result particularly intense up to 750 nm. Such features were attributed to the overlapping of contributions from metal-to-ligand (a minor contribution from d-d transitions in the outer metal. The spectra for the ferrocyanides series are dominated by the metal-to-ligand charge transfer band below 550 nm, approximately 100 nm above this transition in cobalticyanides. Within the studied solids, the most intense and broad metal-to-metal charge transfer bands were found for a series of low spin Co(III) high spin Co(II) hexacyanoferrates(II,III) and with similar features also for ferric ferrocyanide (Prussian blue), assigned to Fe(II) → Co(III) and Fe(II) → Fe(III) photo-induced transition, respectively. The first of these transitions requires of more energetic photons to be observed, its maximum falls at 580 nm while for Prussian blue it is found at 670 nm. Prussian blue analogues are usually obtained as nanometric size particles and many of them have a microporous structure. The role of surface atoms on the observed charge transfer bands in the studied series of compounds is also discussed.

Prussian blue nanowires fabricated by electrodeposition in porous anodic aluminum oxide

Highly ordered prussian blue (PB) nanowire arrays were fabricated successfully for the first time by self-assembling in a nan-oporous anodic aluminum oxide template. The nanowires with different lengths and diameters could be obtained by controlling, respectively, the deposition time and the size of the nanohole in the template. The structure and morphology of the nanowires were characterized by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. The results showed each of the nanowires was a continuous and preferentially of single crystal with face-centered-cubic structure. The Curie temperature Tc of PB nanowires was lower with respect to that of PB bulk. The growth mechanism of the nanowire is also discussed.

Synthesis of ultrathin films of Prussian blue by successive ion adsorption technique

Ultrathin films of Prussian blue (PB) were successfully prepared on substrates by the successive ion adsorption technique that consisted of alternate immersions of a substrate into solutions of Fe2+ and Fe(CN)63-. The PB films showed stable electrochemical redox and electrochromic properties.

STUDIES OF DIFFERENT HYDRATED FORMS OF PRUSSIAN BLUE

Results of thermal gravimetric analysis, electrical conductivity and (1)H n.m.r. studies of Prussian Blue, Fe43+2+(CN6>3*nH2O, a classical mixed-valence compound exhibiting semiconducting behaviour in the temperature range 30-150 deg C, are presented.Three different stages of hydration together with the anhydrous form have been identified by thermal gravimetric analysis.The proton magnetic resonance investigation suggested that there are bound water molecules and electrical conductivity studies confirm the existence of these four forms by the four different values of the activation energy.Variations of the activation energy on hydration have been interpreted qualitatively in terms of the energy band and energy levels of Fe2+ and Fe3+.

14. Valence Delocalization in Prussian Blue Fe(III)43*xD2O, by Polarized Neutron Diffraction

Polarized neutron diffraction has been used to investigate the spin delocalization from the high-spin Fe(III) sites to the low-spin Fe(II) in deuteriated Prussian Blue, Fe43*xD2O.Measuremants of the 111, 200, and 400 reflections were made on a powdered sample at 3 K and 4.8 T using a neutron wavelength of 1.074 A.The expectation value of S at the Fe(II) site is -0.008+/-0.028 corresponding to an upper limit of about 5percent of an electron for the spin delocalization.