Prussian white

Prussian white Prussic acid Prusside compounds PS... 

Efficient dihydrogen formation catalyzed by polynuclear metal-cyanide complexes, coated on the electrode, takes place in acidic aqueous solution. This was shown for Prussian white (K4[f e4l 1 Fen(CN )r,]3)46 and ferric ruthenocyanide (Fe4ni[Run(CN)6]3)47 materials. 

Reduction of PB yields Prussian white (PW), also known as Everitt s salt, which appears colorless as a thin film (Equation (12)) ... 

In the literature the term soluble Prussian blue introduced by Keggin and Miles [5] to determine the KFeFe(CN)6 compound is still widely used. However, it is important to note, that the term soluble refers to the ease with which the potassium ion can be peptized rather than to the real solubility of Prussian blue. Indeed, it can be easily shown by means of cyclic voltammetry that the stability of Prussian blue films on electrode supports is nearly independent of their saturation by potassium cations. Moreover, Itaya and coworkers [9] have not found any appreciable amount of potassium ions in Prussian blue, which makes doubtful structures like KFeFe(CN)6. Thus, the above equation fully describes the Prussian blue/Prussian white redox reaction. 

The Prussian blue/Prussian white redox activity with potassium as the countercation is observed in cyclic voltammograms as a set of sharp peaks with a separation of 15-30 mV. These peaks, in particular the cathodic one, are similar to the peaks of the anodic demetallization. Such a set of sharp peaks in cyclic voltammograms correspond to the regular structure of Prussian blue with homogeneous distribution of charge and ion transfer rates throughout the film. This obvious conclusion from electrochemical investigations was confirmed by means of spectroelectrochemistry [10]. 

The sharpness of Prussian blue/Prussian white redox peaks in cyclic voltammograms can be used as an indicator of the quality of Prussian blue layers. To achieve a regular structure of Prussian blue, two main factors have to be considered the deposition potentials and the pH of initial growing solution. As mentioned, the potential of the working electrode should not be lower then 0.2 V, where ferricyanide ions are intensively reduced. The solution pH is a critical point, because ferric ions are known to be hydrolyzed easily, and the hydroxyl ions (OH-) cannot be substituted in their... 

It is important to note that not all cations promote Prussian blue/Prussian white electroactivity. Except for potassium, only ammonium (NH4+), cesium (Cs+), and rubidium (Rb+) were found able to penetrate the Prussian blue lattice. Other mono-and divalent cations are considered as blocking ones. 

In contrast to a variety of oxidizable compounds, only a few examples for the detection of strong oxidants with transition metal hexacyanoferrates were shown. Among them, hydrogen peroxide is discussed in the following section. Except for H202, the reduction of carbon dioxide [91] and persulfate [92] by Prussian blue-modified electrode was shown. The detection of the latter is important in cosmetics. It should be noted that the reduction of Prussian blue to Prussian white occurs at the lowest redox potential as can be found in transition metal hexacyanoferrates. 

Electroreflectance spectroscopy has been successfully applied to numerous other systems such as oxide films or adsorbed dyes. It is most useful when the observed features can be related to specific electronic transitions. As an example we mention the reactions of a film of Prussian Blue adsorbed on gold or platinum. Prussian Blue can be oxidized to Berlin Green, or reduced to Prussian White. The appearance of the products gives rise to characteristic features in the electroreflectance spectra [11]. 

Zhao et al. prepared magnetite (FesO nanoparticles modified with electroactive Prussian Blue [44]. These modified NPs were drop-cast onto glassy-carbon electrodes. They observed the redox processes commonly observed for PB (similar to that seen in Figure 4.8), and also demonstrated that the Prussian White material produced by PB reduction at 0.2 V served as an electrocatalyst for Fi202 reduction. They also prepared LbL films in which PB NPs and glucose oxidase were alternated between PD DA layers [99]. These were demonstrated to act as electrocatalysts for Fi202 reduction. Based on the ability to sense the product of the enzymatic reaction, these structures were shown to act as glucose sensors. 

Prussian white -use m gemstone treatment [GEMSTONES - GEMSTONE TREATMENT] pol 12) - [CHROMOGENICMATERIALS - ELECTROCHROMIC] pol 6)... 

Evaluate the two most important parameters the coverage of the PB deposited on the electrode surface (r, mol cm-2), and the difference between the anodic and the cathodic peak potentials (AEp, mV) revealing the electrochemical reversibility of the interconversion between PB and Prussian white. 

State. When both iron environments contain only iron(II), the resulting salt is not colored (Prussian White). The oxidation state localization in PB has been studied extensively. Structures, electrochemical behavior (electrodes batteries), and uses in medicine (treatment of Cs and of thallium poisoning) of Prussian Blue are mentioned in a review of cyanide complexes. In cobalt-iron Prussian Blue analogues, NaxCo3,Fe(CN)6-zH20 electronic and spin states are controlled by temperature and the ligand field strength around the Co + ions, which in turn is determined by the Co Fe ratio. ... 

FIG. 19 Using direct electron transfer at the solid/solid interface, an image of the crystal grains in a Prussian white film in 20 mM KC1 (pH 4) could be obtained with a penetrating tip. 25 gm X 25 pm, Es = —0.2 V and ET = +0.3 V, tip current 500 pA. Prussian white is continuously oxidized to Prussian blue. (From Ref. 48, with permission from Elsevier Science.)... 

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