Irreversible electrostatic deposition of Prussian blue from colloidal solutions

Prussian blue (PB) can be deposited from colloidal solutions (5.4?×?10^?3?mol_PB?L^?1, 0.01?mol?L^?1 KNO₃) on glassy carbon, either by potential cycling or potentiostatically, provided that the deposition potential is more positive than ?0.2?V vs. Hg/Hg₂Cl₂. Depending on the deposition potential, the PB particles form either a single layer of Everitt??s salt, of PB, or multilayers of Berlin green. Also depending on the electrode potential, the deposition was accompanied by currents which were either only of capacitive nature, or represent the sum of capacitive and faradaic currents. The currents were always limited by the diffusion of the colloidal particles to the electrode surface, i.e., they obeyed the Cottrell equation. The PB layers were characterized by in situ atomic force microscopy.     

Irreversible electrostatic deposition of CdTe quantum dots on glassy carbon electrodes from colloidal solutions

Journal of Solid State Electrochemistry - Cadmium telluride quantum dots (CdTe-QDs) can be deposited from colloidal solutions on glassy carbon (GC) electrodes potentiostatically. The immobilization...     

普鲁士蓝膜的电沉积及其电化学阻抗谱

利用循环伏安法在两种不同组成的电解液中进行铂电极上普鲁士蓝膜的电化学沉积，在氯化钾溶液中测量了修饰膜的循环伏安行为，比较了两种膜的电化学阻抗谱。修饰普鲁士蓝膜铂电极的电化学阻抗谱测量结果表明，沉积条件及其沉积膜厚度均对电子传递过程产生影响。     

Potentiodynamic deposition of Prussian blue from a solution containing single component of ferricyanide and its mechanism investigation

Potentiodynamic techniques were used for the direct electrodeposition of Prussian blue nano-clusters from an acidic solution of ferricyanide. Electrochemical, EQCM, IR, AFM, and UV/vis measurements were carried out to characterize deposited nano-sized Prussian blue and to explore the formation mechanism. Results showed that ferricyanide could partially dissociate to free ferric and cyanide ions. The driving force of this dissociation is the formation of PB and the evolution of HCN. The optimal potential window for the potentiodynamic formation of PB from an acidic solution (pH 1.6) is between –0.5 V and 0.4 V. In addition, the influence of surface adsorption of CN^- ions on the formation of PB was discussed.Dedicated to Professor W. Vielstich on the occasion of his 80th birthday.     

Electrochemical deposition and mechanism investigation of Prussian blue on graphic carbon paste electrode from an acidic ferricyanide solution

Prussian blue (PB) films were electrochemically deposited on graphite carbon paste electrodes (GCPEs) from an acidic solution of ferricyanide using the potentiodynamic and potentiostatic techniques. Interestingly, we, for the first time, observed that on the surface of GCPE, the electrochemistry of PB films strongly depended on the deposition potential. A maximum formation rate of PB was obtained at a more positive deposition potential (0.4 V vs saturated calomel electrode) on GCPE than that on Au or Pt electrode. The ratio of peak current at ca 0.75 V to the one at 0.19 V varied with the deposition potential. In addition, the electrocatalytic activity of the modified GCPEs towards the reduction of hydrogen peroxide considerably changed with the formation potentials of the PB films. These phenomena can be due to the different formation mechanism of PB at different deposition potentials. Dedicated to Prof. Dr. Teresa Iwasita on the occasion of her 65th birthday in recognition of her numerous contributions to interfacial electrochemistry.     

Layer-by-layer self-assembly of Prussian blue colloids

The adsorption of Prussian blue (PB) colloids within layers of polyelectrolytes has been achieved by a reiterative immersion-rinse approach. Multilayer assemblies consisting of alternate layers of these components have been prepared by the layer-by-layer (LbL) self-assembly technique. Both processes have been carefully monitored by cyclic voltammetry and infrared and UV-visible spectroscopy. Linear increase in the IR and UV-visible light absorbance with the number of deposited layers indicates that well-organized lamellar systems have been elaborated. Size and distribution of Prussian blue nanoparticles in these systems have been investigated by AFM. The effect of the molar concentration of the PB dipping solution on the adsorption process and the distribution of the PB colloids has also been described. Finally, magnetic properties of these assemblies have been studied by low-temperature ESR measurements. Indeed, this new approach of hybrid LbL films opens the way to a new class of nanostructured lamellar compounds.     

Novel magnetic functionalities of Prussian blue analogs

Cyano-bridged bimetal assemblies demonstrate novel magnetic functionalities, particularly Prussian blue analogs, which have unique properties. In this perspective, we describe a charge-transfer phase transition, reversible photomagnetism, second harmonic generation and magnetization-induced second harmonic generation, ferroelectric ferromagnetism, humidity-sensitive magnetism, high ionic conductivity, and a coupling effect (which we named spin-ionics) between ionic conduction and magnetic ordering with Prussian blue analogs.     

Photocontrolled magnetization of CdS-modified Prussian blue nanoparticles

The first photocontrollable magnetic nanoparticles containing CdS and Prussian blue (PB) have been created using reverse micelles as nanoreactors. Photoinduced electron transfer from CdS to PB in the reverse micelle changed the magnetic properties of the composite nanoparticles from ferromagnetic to paramagnetic. The magnetization in the ferromagnetic region below 4 K was substantially decreased after UV light illumination and could be restored almost to its original level by thermal treatment at room temperature. This novel strategy of designing composite nanoparticles containing photoconductive semiconductors and magnetic materials to create photoswitchable magnetic materials may open many possibilities in the development of magneto-optical devices.     

A simple chemical method for visualization of sebaceous fingerprints on unfired cartridge cases by Prussian blue deposition

Russian Journal of Applied Chemistry - This paper presents a new method for chemical development of latent fingerprints on unfired cartridge cases and some metal surfaces. It is based on chemical...     

Chronocoulometric study of the electrochemistry of Prussian blue

During the electrochemical oxidation of Prussian blue (PB) to Prussian yellow (PY), an electrocatalytic oxygen production proceeds at the electrode when aqueous electrolyte solutions are used. The formed oxygen is scavenged by the PY, probably by absorption, and it is consumed during the electrochemical reduction of PY to PB by a heterogeneous chemical reaction of PB with oxygen to PY and hydrogen peroxide. Because of this catalytic regeneration of PY, it is impossible to determine the amount of low-spin iron by chronocoulometry using a potential program in which PB is first oxidized to PY and then the charge is measured to reduce PY to PB. The latter charge is biased by the electrocatalytic PY regeneration.     

Directed assembly of multilayers--the case of Prussian blue

We introduce the concept of 'directed assembly' of multilayers on surfaces: the overall process involves the exposure of a surface to a series of solutions containing, alternately, adsorbable cations and adsorbable anions, and these are gradually built up into well-defined multilayer structures.     

Nanocomposite of a chromium Prussian blue with TiO2. Redox reactions and the synthesis of Prussian blue molecule-based magnets

The reaction of [NEt₄]₃[Cr(CN)₆] with titanium(III) p-toluenesulfonate at a pH of 2 affords a gray solid whose metal content and spectroscopic and magnetic properties are fully consistent with it being a Prussian blue material of stoichiometry “Ti^III[Cr^III(CN)₆] · H₂O”. The carbon, nitrogen, and hydrogen content, however, are not consistent with this stoichiometry, and further investigation showed that the gray material has a powder X-ray diffraction profile, infrared spectrum, and magnetic properties very similar to those of the “all-chromium” Prussian blue Cr^II[Cr^III(CN)₆]_0.67 · 6H₂O. All data, including the C, H, and N weight percentages, are consistent with the conclusion that the material isolated is a nanocomposite of Cr^II[Cr^III(CN)₆]_0.67 · xH₂O and TiO₂ in the ratio of 1–1.6. These results suggest that Ti^III reduces some of the [Cr^III(CN)₆]³⁻ ions to generate Ti^IV and Cr^II; the former hydrolyzes to amorphous TiO₂ · 2H₂O, the latter loses its bound CN ligands and reacts with unreacted [Cr^III(CN)₆]³⁻ ions to generate the crystalline all-chromium PB species. The electrochemical potentials suggest that the [Cr^III(CN)₆]³⁻ ion should not be reduced by Ti^III; evidently, this unfavorable reaction is driven by the insolubility of the reaction products. The results constitute a cautionary tale in two respects: first, that the characterization of Prussian blue materials must be conducted with care and, second, that the insolubility of Prussian blue analogues can sometimes drive reactions that in solution are thermodynamically unfavorable.     

Thermal decomposition of Prussian blue under inert atmosphere

The thermal decomposition of Prussian blue (iron(III) hexacyanoferrate) under inert atmosphere of argon was monitored by thermal analysis from room temperature up to 1000?°C. X-ray powder diffraction and ⁵⁷Fe M?ssbauer spectroscopy were the techniques used for phase identification before and after sample heating. The decomposition reaction is based on a successive release of cyanide groups from the Prussian blue structure. Three principal stages were observed including dehydration, change of crystal structure of Prussian blue, and its decomposition. At 400?°C, a monoclinic Prussian blue analogue was identified, while at higher temperatures the formation of various polymorphs of iron carbides was observed, including an orthorhombic Fe₂C. Increase in the temperature above 700?°C induced decomposition of primarily formed Fe₇C₃ and Fe₂C iron carbides into cementite, metallic iron, and graphite. The overall decomposition reaction can be expressed as follows: Fe₄[Fe(CN)₆]₃·4H₂O????4Fe?+?Fe₃C?+?7C?+?5(CN)₂?+?4N₂?+?4H₂O.     

Multilayer membranes via layer-by-layer deposition of organic polymer protected Prussian blue nanoparticles and glucose oxidase for glucose biosensing

Polyelectrolyte multilayers (PEMs) are now widely used for bioanalytical applications. In this work, a bilayer of poly(diallydimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS) is consecutively adsorbed on 3-mercapto-1-propanesulfonic acid modified Au electrode surfaces, forming stable, ultrathin multilayer films. Subsequently, Prussian blue nanoparticles protected by PDDA (denoted as P-PB) and negatively charged glucose oxidase (GOx) are consecutively adsorbed onto the PSS-terminated bilayer. The growth of each of the P-PB/GOx bilayers is followed quantitatively using UV-visible absorption spectroscopy and the electrochemical method. The P-PB nanoparticles can catalyze the electroreduction of hydrogen peroxide formed from enzymatic reaction at lower potential and inhibit the responses of interferents, such as ascorbic acid (AA) and uric acid (UA). Performance of the multilayer films can be tailored by controlling the number of bilayers. Under optimal conditions, a linear range of 0.10 to 11.0 mM and a detection limit of 10 microM were achieved. The glucose biosensor has good stability and reproducibility.     

Light-regulated electrostatic interactions in colloidal suspensions

The net charge of a colloidal particle was controlled using light and a new photocleavable self-assembled monolayer (SAM). The SAM contained a terminal ammonium group and a centrally located carboxylic acid group that was masked with an ortho-nitrobenzyl functionality. Once exposed to UV light, the 2-nitrobenzyl group was cleaved, therefore transforming the colloidal particle from a net positive (silica-SAM-NH3+) to a net negative (silica-SAM-COO-) charge. By varying the UV exposure time, their zeta potential could be tailored between +26 and -60 mV at neutral pH. To demonstrate a photoinduced gel-to-fluid phase transition, a binary colloidal suspension composed of silica-SAM-NH3+ and negatively charged, rhodamine-labeled silica particles was mixed to form a gel. Exposure to UV light rendered all of the particles negative and therefore converted the system into a colloidal fluid that settles to form a dense sediment.     

Photochemical synthesis of Prussian blue film from an acidic ferricyanide solution and application

We describe a novel photochemical method to synthesize compacted Prussian blue (PB) film from an acidic ferricyanide solution. The key step is the photochemical reduction of ferricyanide ion to ferrocyanide ion that subsequently coordinates with the free ferric ion dissociated from the ferricyanide in acidic medium to form Prussian blue on the illuminated electrode surface. The prepared PB film electrode shows high electrocatalytic activity towards the reduction of hydrogen peroxide and the amperometric responses show a linear dependence on the concentration of hydrogen peroxide in a range of 1.0 × 10⁻⁶ to 1.2 × 10⁻³ M with a detection limit down to 4 × 10⁻⁷ M. The present photochemical method provides a simple and promising route for the local fabrication of patterned molecular magnets, ion-selective sensors, and electro- or photochromic devices.     

Electric-field-induced conductance switching in FeCo Prussian blue analogues

FeCo Prussian blue analogues, which are known as typical molecule-based magnets, exhibited abrupt conductance switching by applying a high electric field as well as by varying the temperature. The current density versus electric field (J-E) curves of FeCo Prussian blue with Rb cations in interstitial sites shows so-called negative resistance effects at electric fields higher than the threshold voltage. This means that the FeCo Prussian blue analogues are multiproperty materials in the sense that their conducting, magnetic, and optical properties can be reversibly controlled by certain external stimuli.     

Visualization of latent fingerprints using Prussian blue thin films

Herein,a facile and effective approach was proposed for visualizing latent fingerprints(LFPs) on two kinds of conductive surfaces by spatially selective electrochemical deposition of Prussian blue(PB) thin films.This strategy exploited the fingerprint residue as an insulating mask and the PB thin films were only generated on the bare surface including the valleys between the papillary ridges,which produced a negative image of LFPs with high resolution up to the third level information.The surface morphology of PB films was characterized by the field emission scanning electron microscopy(FE-SEM).This enhancement technique showed promising performance in selected materials of practical interest.     

Separation of radionuclides in colloidal form from aqueous solutions

A review is presented on the separation of colloidal radionuclides from aqueous solutions involving the sorption and flotation methods.