Electrochromism and electrochemical magnetism in Ni–Fe Prussian blue

We studied the electrochemical and magnetic properties of NiFe Prussian blue. The NiFe Prussian blue was synthesized on Ni electrodes in the form of thin films by an electrochemical technique. Measurements of its magnetic properties show that NiFe Prussian blue with the Fe^{III-low spin (LS)}–CN–Ni^II structure exhibits ferromagnetic properties, with T _c (critical temperature)=25 K. On the other hand, the reduced form, which has the Fe^II-LS–CN–Ni^II structure, is paramagnetic. This means that the magnetic properties can be controlled between ferromagnetic and paramagnetic by an electrochemical method. Furthermore, it is well known that NiFe Prussian blue exhibits electrochromic properties. Hence, this compound is a multifunctional, molecule-based compound in which optical and magnetic properties can be controlled by an electrochemical redox reaction. Contribution to the special issue on “Magnetic field effects in Electrochemistry.”     

Cyclic voltammetric studies of Prussian blue and viologens within a paper matrix for electrochromic printing applications

The apparent redox response of Prussian blue (PB, iron(III) hexacyanoferrate(II)) within a paper matrix is similar to that found in conventional liquid electrolyte voltammetry using a PB-modified electrode; however part of the response is from PB which adsorbs onto the glassy carbon (GC) working electrode. Application of a Nafion® coating to the PB-impregnated paper matrix prevents transfer of PB to the GC surface. In contrast to the PB system, the redox response of the 1,1′-dimethyl-4,4′-bipyridilium (MV, methyl viologen) system, where both redox states examined are soluble, is confined wholly to the paper matrix. For the case of 1,1′-diheptyl-4,4′-bipyridilium (HV, heptyl viologen), the electrogenerated insoluble radical cation salt adsorbs onto the GC electrode, the KCl-impregnated paper acting simply as the electrolyte medium. PB can be electrogenerated within a paper matrix, with the possible application in monochrome electrochromic printing systems.     

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.     

Electrochemical quartz crystal microbalance study on the two-electrode-system cyclic voltammetric behavior of Prussian blue films

A two-channel electrochemical quartz crystal microbalance (EQCM) was used to investigate the cyclic voltammetric behavior of two Prussian blue (PB) film-modified Au electrodes in a two-electrode con-figuration in aqueous solution. The redox peaks observed in the two-electrode cyclic voltammogram (CV) are assigned to the intrinsic redox transitions among the Everitt's salt, PB, and Prussian yellow for the film itself, the redox process of the Au substrate and the redox process of small-quantity ferri-/ferrocyanide impurities entrapped in the PB film, as also supported by ultraviolet-visible (UV-Vis) spectroelectrochemical data. The profile of the two-electrode solid-state CV for the PB powder sand-wiched between two gold-coated indium-tin oxide (ITO) electrodes is similar to that for two PB-modified Au electrodes in aqueous solution, implying similar origins for the corresponding redox peaks. The two-channel EQCM method is expected to become a highly effective technique for the studies of the two-electrode electrochemical behaviors of many other species/materials.     

Functionalization of graphene with electrodeposited Prussian blue towards amperometric sensing application

Prussian blue (PB) was grown compactly on graphene matrix by electrochemical deposition. The as-prepared PB-graphene modified glassy carbon electrode (PB-graphene/GCE) showed excellent electrocatalytic activity towards both the reduction of hydrogen peroxide and the oxidation of hydrazine, which could be attributed to the remarkable synergistic effect of graphene and PB. The PB-graphene/GCE showed sensitive response to H₂O₂ with a wide linear range of 10-1440 μM at 0.0 V, and to hydrazine with a wide linear range of 10-3000 μM at 0.35 V. The detection limit was 3 μM and 7 μM, respectively, and both of them had rapid response within 5 s to reach 95% steady state response. The wide linear range, good selectivity and long-time stability of the PB-graphene/GCE make it possible for the practical amperometric detection of hydrogen peroxide and hydrazine.     

Simultaneous identification of historical pigments Prussian blue and indigo in paintings by electrospray mass spectrometry

A new analytical protocol for identification of Prussian blue (PB) and indigo was proposed. Pigments useful for dating of artworks were detected by flow injection analysis/electrospray ionization mass spectrometry after alkalization of their suspensions in water, decomposition of PB to iron (III) hydroxide and hexacyanoferrate (II) and reduction of indigo to soluble leucoindigo using sodium dithionite. Limits of detection (PB 47 pg, indigo 59 pg) complied with requirements for analysis of microsamples of historical paintings. Potential of the developed method was proven in analysis of blue samples of two oil paintings from the 20^th century. Further, PB was confirmed in a microsample from a painting of ‘Crucifixion’, St. Sebestian church on St. Hill in Mikulov, Czech Republic. Copyright © 2013 John Wiley & Sons, Ltd.     

Amperometric biosensors based on the immobilization of oxidases in a Prussian blue film by electrochemical codeposition

Prussian blue has been formed by cyclic voltammetry onto the basal pyrolytic graphite surface to prepare a chemically modified electrode which provides excellent electrocatalysis for both oxidation and reduction of hydrogen peroxide. It is found for the first time that glucose oxidase or -amino oxidase can be incorporated into a Prussian blue film during its electrochemical growth process. Two amperometric biosensors were fabricated by electrochemical codeposition, and the resulting sensors were protected by coverage with a thin film of Nafion. The influence of various experimental conditions was examined for optimum analytical performance. The glucose sensor responds rapidly to substrates with a detection limit of 2 × 10⁻⁶ M and a linear concentration range of 0.01–3 mM. There was no interference from 2 mM ascorbic acid or uric acid. Another ( -amino acid) sensor gave a detection limit of 3 × 10⁻⁵ M -alanine, injected with a linear concentration range of 7.0 × 10⁻⁵-1.4 × 10⁻² M. Glucose and -amino acid sensors remain relatively stable for 20 and 15 days, respectively. There is no obvious interference from anion electroactive species due to a low operating potential and excellent permselectivity of Nafion.     

Morphology and thermoresponsive behavior of hybrid micelles of polystyrene-b-poly((N-isopropyl acrylamide)-co-(4-vinylbenzyl chloride)) with Prussian blue

The hybrid micelles of polystyrene-b-poly((N-isopropyl acrylamide)-co-(4-vinylbenzyl chloride)) block copolymer(PS-b-P(NIPAM-co-VBC)) with Prussian blue(PB) in the corona were prepared by reaction of pentacyano(4-(dimethylamino)-pyridine)ferrate(Fe-DMAP)-attached PS-b-P(NIPAM-co-VBC) with Fe Cl3. The formation of the PB framework inside the micelles was verified by UV-Vis, FTIR and TGA. The morphology of the hybrid micelles was studied by TEM and compared with that of the neat and Fe-DMAP-attached PS-b-P(NIPAM-co-VBC). It is found that attachment of Fe-DMAP may change the short rod-like micelles of the neat PS-b-P(NIPAM-co-VBC) into spherical ones and lead to a smaller micelle size. The morphology of the hybrid micelles may be altered or remain unchanged after formation of the PB framework, depending on the chain structure of PS-b-P(NIPAM-co-VBC) and starting concentration. The thermoresponsive behavior of different micelles was studied using DLS. It is observed that attachment of Fe-DMAP can improve the hydrophilicity of the P(NIPAM-co-VBC) block, leading to weaker hysteresis of the micelle size during the heating and cooling cycle. However, the crosslinked PB framework in the micellar corona may result in a more evident hysteresis phenomenon and blur the two-stepwise change of the micellar size with temperature.     

Novel self assembled magnetic Prussian blue graphene based aerogel for highly selective removal of radioactive cesium in water

A novel self-assembled Magnetic Prussian Blue/Reduced Graphene Oxide (3D-MPBRGO) aerogel was prepared by an easy and cost effective process for elimination of radioactive Cesium from contaminated aqueous solution selectively. The 3D-MPBRGO displayed excellent adsorption capability of 3.64 mmol per g or (484.12 mg/g) for Cs (initial 50 mM cesium concentration, pH 7 and 30 °C) and quick separation from solution by applying magnetic field as compared to previously published results for graphene based adsorbents. This excellent removal efficiency of nanocomposite can be ascribed to enlarged adsorbent surface area (402.68 m²/g) and uniform distribution of nanoparticles on RGO which removes aggregation of sheets as well. The thermodynamic analysis displayed exothermic and spontaneous nature of Cs ion adsorption. The experimental data of adsorption isotherm followed the Langmuir isotherm model than that of Tempkin and Freundlich while adsorption kinetics followed pseudo second order.     

Oxidation pathways and kinetics of morphine in acidic and neutral media on the aluminum electrode covered by metallic palladium and modified by Prussian blue

This paper describes the use of an aluminum electrode covered by metallic palladium and modified by Prussian blue prepared by a simple and rapid electroless method for the electro-oxidation of morphine. Two different pathways for electro-oxidation of morphine at various pH ranges were suggested. Also, some thermodynamic and kinetic parameters such as the number of electrons involved in the rate determining step, n _α , transfer coefficient α, and the total electrons (n) involved in morphine oxidation at the time scale of the cyclic voltammetric technique, the catalytic rate constant of the electrochemical process k, and diffusion coefficient of morphine D were determined. The mean values obtained are 0.5, 0.5, 1, 26.8 M^-1 s^-1 and 3.1 × 10⁻⁵ cm² s⁻¹, respectively.     

Self‐Assembling of Hybrid Prussian Blue Units in Cinder Matrix: Characterization and Electrocatalysis

Industrial waste cinder (CFe*) has been utilized as a stable anchoring matrix for self‐assembling of Fe(CN)₆^3? as hybrid Prussian blue units (PB, *Fe³⁺Fe^II(CN)₆) on a screen‐printed carbon electrode (SPE) for efficient catalytic applications. The waste cinder was found to be a composite of calcium and iron silicates similar to glass matrix by X‐ray photoelectron spectroscopic (XPS) study. The hybrid PB formations were confirmed by both FT‐IR and electrochemical methods. Most importantly, the free iron (Fe*) ion bound to the non‐bridging oxygen terminals of the silicates was found to play a key role in the PB formation. The self‐assembled PB hybrid on the cinder‐modified screen‐printed electrodes (designated as PBCFe*‐SPE) improved linear detection range and sensitivity for H₂O₂ mediated oxidation than those obtained at a classical PB‐SPE in 0.1 M, pH 2 KCl/HCl base electrolyte at 0.0 V (vs. Ag/AgCl) by amperometric batch analysis.     

Introduction of high valent Mo6+ in Prussian blue analog derived Co-layered double hydroxide nanosheets for improved water splitting

Herein, we report a facile method for synthesizing MoCo-layered double hydroxide (LDH) nanosheets employing Prussian blue analog (PBA) as the precursor. The introduction of Mo in Co-LDH modulates the electronic structure, increases the number of active sites and electrochemical surface area to improve the hydrogen evolution, oxygen evolution, and overall water splitting activity. As a result, PBA-derived Mo_0.25Co_0.75-LDH nanosheets demonstrated 10 mA cm^?2 current density at only 220 mV and 115 mV overpotentials for OER and HER, respectively. The overall water splitting was attained at 1.52 V cell voltage for 10 mA cm^?2 current density.     

Microelectrochemical electronic effects in two-layer structures of distinct Prussian blue type metal hexacyanoferrates

The formation of a rigid bilayer structure from two metal hexacyanoferrates: Prussian blue (PB) and nickel hexacyanoferrate (NiHCNFe), as inner and outer films, respectively, has been demonstrated. To avoid intermingling of the granular cyanometallate microstructures, namely of the outer film (NiHCNFe) into the inner film (PB), the morphology of outer film material was changed by forming a polymeric hybrid (composite) of NiHCNFe with poly(N-methylpyrrole). The outer NiHCNFe film is physically separated from the electrode surface, and it undergoes redox reactions at potentials characteristic of the inner PB film. This arrangement leads to the reversible charge state trapping and bistable switching during voltammetric potential cycling. Under solid-state voltammetric conditions in the absence of contact with the liquid electrolyte phase, when the bilayer structure of PB and the oxidized NiHCNFe was formed between two sandwich-forming carbon electrodes, unidirectional rectifying current flow has been observed.Dedicated to Zbigniew Galus on the occasion of his 70th birthday     

A non‐gassing electroosmotic pump with sandwich of poly(2‐ethyl aniline)‐Prussian blue nanocomposite and PVDF membrane

Low voltage, non‐gassing electroosmotic pump (EOP) was assembled with poly(2‐ethyl aniline) (EPANI)‐Prussian blue nanocomposite electrode and commercially available hydrophilic PVDF membranes. The nanocomposite material combines excellent oxidation/reduction capacity of EPANI with exceptional stability by shuttling of proton between Prussian blue nanoparticles and EPANI redox matrix. The flow rate was highly dependent on the electrode composition but it was linear with applied voltage. The flow rate at 5 V for different nanocomposite, EPANI, EPANI‐A, EPANI‐B, and EPANI‐C were 127.29, 187.41, 148.51, and 95.47 µL/min cm², respectively, which increases substantially with increase in the Prussian blue content. The obtained best electro osmotic flux was 43 µL/min/V/cm² for EPANI‐A. It was higher than most of the EOP assembled using polyquinone and polyanthraquinone redox polymers. The assembled EOP remained exceptionally stable until the electrode charge capacity was fully utilized. The best EOP produces a maximum stall pressure of 1.2 kPa at 2 V. These characteristics make it suitable for a variety of microfluidic/device applications.     

Formation of carbonylrhenium cryptates with alkali metal cations: Coordination chemistry studies of [Ph2P(E)NP(E)Ph2], E = O,S, Se towards ReBr(CO)5

Reaction of ReBr(CO)₅ with Li[Ph₂P(O)NP(O)Ph₂] afforded the cryptate Li[Re₂(CO)₆{μ-Ph₂P(O)NP(O)Ph₂-κ²O,O’}₃]; whereas K[Ph₂P(O)NP(O)Ph₂] reacted with ReBr(CO)₅ to give K[Re₂(CO)₆{μ-Ph₂P(O)NP(O)Ph₂-κ²O,O′}{Ph₂P(O)NP(O)Ph₂-κ²O,O′}₂]. Other chalcogen ligands’ salts M[Ph₂P(E)NP(E)Ph₂], E = Se and S, M = K and Li gave dirhenium carbonyls with bromido and Ph₂P(E)NP(E)Ph₂, E = Se or S bridges upon reaction with ReBr(CO)₅.     

Measurement of apparent diffusion coefficients within ultrathin nafion Langmuir-Schaefer films: comparison of a novel scanning electrochemical microscopy approach with cyclic voltammetry

The use of scanning electrochemical microscopy (SECM) to evaluate the apparent diffusion coefficient, Dapp, of redox-active species in ultrathin Nafion films is described. In this technique, an ultramicroelectrode (UME) tip, positioned close to a film on a macroscopic electrode, is used to oxidize (or reduce) a species in bulk solution, causing the tip-generated oxidant (reductant) to diffuse to the film/solution interface. The oxidation (reduction) of film-confined species regenerates the reductant (oxidant) in solution, leading to feedback to the UME. A numerical model is developed that allows Dapp to be determined. For these studies, ultrathin films of Nafion were prepared using the Langmuir-Schaefer (LS) technique and loaded with an electroactive species, either the ferrocene derivative ferrocenyltrimethylammonium cation, FA+, or tris(2,2'-bipyridyl)ruthenium(II), Ru(bpy)32+. The morphology and the thickness of the Nafion LS films (1.5 +/- 0.2 nm per layer deposited) were evaluated using atomic force microscopy (AFM). For comparison with the SECM measurements, cyclic voltammetry (CV) was employed to evaluate the concentration of electroactive species within the Nafion LS films and to determine Dapp. The latter was found to be essentially invariant with film thickness, but the value for Ru(bpy)32+ was 1 order of magnitude larger than for FA+. CV and SECM measurements yield different values of Dapp, and the underlying reasons are discussed. In general, the Dapp values for these films are considerably smaller than for recast Nafion films, which can be attributed to the compactness of Nafion LS films. Nonetheless, the ultrathin nature of the films leads to fast response times, and we thus expect that these modified electrodes could find applications in sensing, electroanalysis, and electrocatalysis.