Cobalt Hexacyanoferrate Film Research Articles

Amperometric assay of hydrazine utilizing electro-deposited cobalt hexacyanoferrate nanocrystals on graphene oxide sheets

In-situ electrochemical deposition of cobalt hexacyanoferrate (CoHCF) on graphene oxide (GO) and its application for the electrocatalytic hydrazine determination in real samples are described in this research study. Co2+ is immobilized on GO and the resulting material, GO-Co2+ is coated on the surface of glassy carbon (GC) electrode. The fabricated electrode (GC/GO-Co2+) is subjected to a continuous potential cycling in the range of 0.0–1.0 V which results in the formation of a thin CoHCF film on the surface of GO coated on the GC electrode (abbreviated as GC/GO-CoHCF). The synthesized GO-CoHCF composite material is characterized by Fourier transform infrared and scanning electron microscopy. GC/GO-CoHCF electrode electrocatalytically oxidizes hydrazine at low overpotential (0.63 V) and this phenomenon is subsequently utilized for the sensitive determination of hydrazine in aqueous solutions. It exhibits a wide linear calibration range (0.1–400 µM), high sensitivity (0.93 µA µM−1 cm−2) and low limit of detection (17.5 nM) for the determination of hydrazine. Further, this electrode is employed for hydrazine determination in real samples.

Cobalt ferrite nanoparticles as a source of intrinsic metals for simultaneous electrosynthesis of Prussian blue and cobalt hexacyanoferrate

A novel method is proposed for the simultaneous electrochemical formation of Prussian blue (PB) and cobalt hexacyanoferrate (CoHCF) on the surface of edge-plane pyrolytic graphite electrodes (EPPGE) modified by CoFe2O4/Chit/PTCA nanoparticle (NP) (where CoFe2O4 = cobalt ferrite, Chit = chitosan, and PTCA = Perylene-3,4,9,10-tetracarboxylic acid). The PB and CoHCF films are formed from the NP intrinsic metals (Fe3+ and Co2+) in the presence of ferrocyanide ([FeII(CN)6]4−) dissolved in a Britton-Robinson (BR) buffer at pH 1.60. The extent of the film formation is determined by the amount of the PTCA immobilised on the CoFe2O4/Chit NP surface and is influenced by the components of the BR buffer medium. Larger amounts of immobilised PTCA enhance electrosynthesis and generate modified electrodes in situ with excellent electrochemical properties. Optimized electrodes increased electroactive area approximately 420% compared to bare EPPGE. We believe that the combination of NP intrinsic metals, PTCA immobilisation, use of [FeII(CN)6]4− and BR buffer components provides a new electrochemical structure for simultaneous production of PB and CoHCF films. The quality of the electrodes generated in situ by the present method is evidenced by their increased sensitivity and enhanced active surface area relative to bare EPPGE, which indicates its potential for future application in electrochemical sensors.

In situ observation of macroscopic phase separation in cobalt hexacyanoferrate film

Lithium-ion secondary batteries (LIBs) store electric energy via Li+ deintercalation from cathode materials. The Li+ deintercalation frequently drives a first-order phase transition of the cathode material as a result of the Li-ordering or Li-concentration effect and causes a phase separation (PS) into the Li-rich and Li-poor phases. Here, we performed an in situ microscopic investigation of the PS dynamics in thin films of cobalt hexacyanoferrate, LixCo[Fe(CN)6]0.9, against Li+ deintercalation. The thick film (d = 1.5 μm) shows a characteristic macroscopic PS of several tens of μm into the green (Li1.6Co[Fe(CN)6]0.9) and black (Li.6Co[Fe(CN)6]0.9) phases in the x range of 1.0 < x < 1.6. Reflecting the substrate strain, the thin film (d = 0.5 μm) shows no trace of the PS in the entire x region. Our observation suggests that the macroscopic PS plays a significant role in the charge/discharge dynamics of the cathode.

An Electrochemical Sensor for Hydrazine Based on In Situ Grown Cobalt Hexacyanoferrate Nanostructured Film

There is a growing demand for simple, cost-effective, and accurate analytical tools to determine the concentrations of biological and environmental compounds. In this study, a stable electroactive thin film of cobalt hexacyanoferrate (Cohcf) was prepared as an in situ chemical precipitant using electrostatic adsorption of Co2+ on a silicate sol-gel matrix (SSG)-modified indium tin oxide electrode pre-adsorbed with [Fe(CN)6]3− ions. The modified electrode was characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical techniques. Electrocatalytic oxidation of hydrazine on the modified electrode was studied. An electrochemical sensor for hydrazine was constructed on the SSG-Cohcf-modified electrode. The oxidation peak currents showed a linear relationship with the hydrazine concentration. This study provides insight into the in situ growth and stability behavior of Cohcf nanostructures and has implications for the design and development of advanced electrode materials for fuel cells and sensor applications. Keywords: Cobalt hexacyanoferrate, Electrocatalysis, Electrochemical sensor, Hydrazine, Sol-gel matrix

Copper-cobalt hexacyanoferrate modified glassy carbon electrode for an indirect electrochemical determination of mercury

An electrochemical sensor based on a glassy carbon electrode modified with a hybrid film of copper cobalt hexacyanoferrate was prepared for the indirect electrochemical determination of Hg2+. It exploits the formation of a redox inactive complex with thiols. l-cysteine and 1,4-butanedithiol were used, with the former giving more sensitive results. Interference studies were carried out which led to Cu2+ being the major interferent. Exploiting the fact that the response of l-cysteine to Hg2+ is much more rapid compared to Cu2+, the interference from Cu2+ was avoided or minimized by quick measurement of the amperometric current after the addition of the analyte. The modified electrode showed promising results in detecting Hg2+ in spiked mineral water samples.

Use of screen-printed electrodes for quantification of cocaine and Δ​9-THC: adaptions to portable systems for forensic purposes

The worldwide attention for illicit drug consumption is known, mainly cocaine and marijuana, which were the most commonly apprehended drugs. In this study, we adapted conventional systems for voltammetric analysis for identifying these drugs using screen-printed electrode (SPE) devices in a portable potentiostat. For cocaine determination, a commercial platinum screen-printed electrode (Pt-SPE) with a cobalt hexacyanoferrate film (CoHCFe) presented the best results in comparison to other available models, and for Δ9-tetrahydrocannabinol (Δ9-THC), no chemical modification was required on the carbon screen-printed electrodes (C-SPEs). The results allowed the use of the adapted systems with good analytical parameters: cocaine and Δ​9-THC determination presented a sensibility equal to 2.02 × 10−2 and 2.65 × 10−7 A L mol−1 , respectively. Finally, the developed procedures showed an application for electrochemical analysis in forensic context, besides the results obtained to comply with reliable results which forensic analysis must have.

Electrocatalytic determination of thiols using hybrid copper cobalt hexacyanoferrate modified glassy carbon electrode

An electrochemical sensor based on a glassy carbon electrode (GCE) modified by a thin film of hybrid copper cobalt hexacyanoferrate (Cu–CoHCF) was prepared and tested for the determination of three thiols: l-cysteine (CySH), l-glutathione (GSH) and 1,4-butanedithiol (BdSH). Cyclic voltammetry (CV) measurements were carried out with the as prepared and thermally treated chemically modified electrode (CME) in phosphate buffer solution from pH 2 to 7. From the CV measurements, it was concluded that at pH higher than 5, the Cu–CoHCF layer was unstable and underwent significant fouling when biased at a potential at which the three thiols were electrocatalically oxidized. Following the preliminary CVs chronoamperometric measurements were carried out to determine the optimum conditions to develop an analytical method for the determination of thiols. Cysteine showed the lowest limit of detection (7.5×10−7M), but very low values were displayed also by GSH (2.5×10−6M) and BdSH (2.0×10−6M). The range of linearity extended up to 6.0×10−5M for CySH, 9.0×10−5M for GSH and 1.2×10−4M for BdSH without significant fouling of the CME. The analytical method was applied to the determination of GSH in a nutraceutical purchased from the local market.

Application of electrodeposited cobalt hexacyanoferrate film to extract energy from water salinity gradients

Cobalt hexacyanoferrate film as a cheap and efficient electrode material for extracting energy from water salinity gradients.

Influence of co-electrodeposited Gold particles on the electrocatalytic properties of CoHCF thin films

The electrochemical modification of solid electrodes with metal hexacyanoferrate thin films for enhancing the interfacial properties has created interest for over the past three decades. The preparation of Prussian blue (PB) Au nano composites for the enhancement in the electrocatalytic properties of PB on glassy carbon electrode has been reported by us. The incorporation of Au nano particles in Cobalt hexacyanoferrate (CoHCF) films on Glassy carbon by co-electrodeposition is expected to benefit its interfacial electron transfer properties. The present work describes the effect on the interfacial properties by incorporated Au particles in CoHCF (CoHCF(Au)) modified electrodes. The CoHCF(Au) modified electrodes were characterized by UV-Vis spectrophotometry, Cyclic Voltammetry, AC Impedance, FE-SEM etc., Influence on the electrocatalytic properties of CoHCF(Au) films have been explored by performing two important reactions i) Hydrazine elecrtro-oxidation ii) Oxygen evolution reaction. Our results reveal that CoHCF(Au) modified GC electrode perform better in terms of charge transport in the redox film and also for the electrooxidation of hydrazine in comparision with simple CoHCF modified electrodes. By using the current-transient technique (chrono method i vs t curve) the hydrazine diffusion coefficient (D0) were calculated. Diffusion coefficient of hydrazine was approximately three times higher on CoHCF(Au) electrode, 9.5×10−5 cm2 s−1 compared with simple CoHCF modified electrode, 3.3× 10−5 cm2 s−1. Similarly, we also discuss results which reveal that CoHCF(Au) electrodes enhances electrocatalytic activity in splitting water to oxygen in 0.1M NaOH solution compared to simple CoHCF and Au deposited on GC electrodes.

Photoinduced Phase Transition into a Hidden Phase in Cobalt Hexacyanoferrate as Investigated by Time-Resolved X-ray Absorption Fine Structure

Photoinduced dynamics in thin film of cobalt hexacyanoferrate, Na0.79Co[Fe(CN)6]0.902.9H2O, was investigated by time-resolved X-ray absorption fine structure (XAFS) spectroscopy around the Co K edge at 300 K. The compound remains in the low-spin (LS) phase with the electronic configuration of LS Co3+–LS Fe2+ up to 500 K. Nevertheless, the differential XAFS spectrum indicates the formation of high-spin (HS) Co2+ (\({\sim}0.007\)/Co site). The decay time (τdecay) of HS Co2+ is 32 ns, while the formation time is within the time resolution (\({\leq}100\) ps). Such a long decay time suggests photoinduced phase transition (PIPT) into a hidden metastable phase.

Photocurrent determination ascorbic acid using an n-silicon electrode modified by platinum and cobalt hexacyanoferrate films

By depositing a film of cobalt hexacyanoferrate (CoHCF) on silicon electrode coated by a platinum layer, a novel photoelectrochemical sensor for the detection of ascorbic acid (AA) has been developed. The stable film of CoHCF was electrochemically deposited onto a phosphorus heavy doped silicon (n+-Si) with 9 μm epitaxial layer (n–n+-Si) wafers coated with about 40 nm platinum layer (Pt/n–n+-Si). Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectra, X-ray diffraction (XRD) and cyclic voltammetry (CV) were used to characterize the CoHCF film on the Pt/n–n+-Si electrode. The CoHCF modified Pt/n–n+-Si electrode has been used for determination of AA with a two-electrode cell in absence of reference electrode by photocurrent measurement at a zero bias. The composite modified electrode demonstrated good photocurrent responses by adding different concentrations of AA with a good stability. The linear range for the detection of AA was 1.0 × 10−6 to 1.0 × 10−3 M, with a detection limit (S/N = 3) of 1.0 × 10−6 M. This provides a facile way of detecting AA and succeeds in averting from inconvenient reference electrode.

Electrochemical properties of nanostructured cobalt hexacyanoferrate containing K+ and Cs+ synthesized in water-in-oil AOT reverse microemulsions

Herein a series of cobalt–iron Prussian blue analogs (PBAs) containing K+ and Cs+ were synthesized in water-in-oil AOT reverse microemulsions. The size, morphology and composition of the as-prepared cobalt hexacyanoferrate (CoHCF) can be fine-tuned by conveniently varying the water-to-surfactant molar ratio (w) of the microemulsion, as confirmed by various techniques such as infrared spectroscopy (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). These nanostructured PBA were thereafter employed to chemically modify electrodes to thoroughly investigate their electrochemical properties. Oxidized and reduced cobalt hexacyanoferrates were fabricated and characterized in the presence of alkali metal (Li+, Na+, K+, Rb+, Cs+) and NH4+ counteractions by cyclic voltammetry (CV). In addition, it was demonstrated that formal potentials of hexacyanoferrate (III, II) redox reactions were sensitive to the choice of electrolyte cations, and they correlated well with the sizes of hydrated Na+, K+, Rb+, Cs+ and NH4+ except for Li+. Furthermore, the samples are found to vary significantly in permeability, probably due to the difference of composition, structure and morphology of products, and the changes during charging/discharging. Finally, it is noteworthy to highlight that the nanostructures of cobalt hexacyanoferrate synthesized at w=5–40 had much more electrochemistry stability than that synthesized in aqueous solution in all electrolytes. The potential application of the modified electrode of CoHCF films in electrochromic display was also noticed.

Electrochromism and redox switching of cobalt hexacyanoferrate–polyaniline hybrid films in a hydrophobic ionic liquid

Electrochromic hybrid thin films of cobalt hexacyanoferrate–polyaniline (CoHCF–PAni) have been synthesized by forming a film of K 2Co 2+[Fe 2+(CN) 6] followed by electropolymerization of PAni from an aqueous micellar solution. The hybrid film structure comprises cube like shapes with a face centered cubic lattice of CoHCF and fibers of PAni. Electrochemistry of hybrid films followed for the first time in an ionic liquid—1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, revealed significant differences in their electrochromic and redox parameters in comparison with those observed for neat CoHCF and PAni films. Charge transfer, capacitive and diffusive phenomena were found to be controlled by the film microstructure, applied potential and the ingress–egress ability of the pyrrolidinium cation. The high coloring efficiency of 262 cm 2 C −1 at 687 nm under +0.4 V shown by the hybrid film and its ability to sustain 1000 cycles without much loss in optical contrast renders it suitable for use in electrochromic smart windows.

Voltammetric determination of cocaine in confiscated samples using a cobalt hexacyanoferrate film-modified electrode

In this work, a fast, non destructive voltammetric method for cocaine detection in acetonitrile medium using a platinum disk electrode chemically modified with cobalt-hexacyanoferrate (CoHCFe) film is described. The deposition of CoHCFe film at platinum disk (working electrode) was carried out in aqueous solution containing NaClO 4 at 0.1 mol L −1 as supporting electrolite. Stability studies of the film and subsequent voltammetric analysis of cocaine were made in acetonitrile medium with NaClO 4 at 0.1 mol L −1 as supporting electrolite. A reversible interaction between cocaine and CoHCFe at the film produces a proportional decrease of original peak current, due to the formation of a complex between cocaine and cobalt íons, with subsequent partial passivation of the film surface, being the intensity of current decrease used as analytical signal for cocaine. A linear dependence of cocaine detection was carried out in the range from 2.4 × 10 −4 to 1.5 × 10 −3 mol L −1, with a linear correlation coefficient of 0.994 and a detection limit of 1.4 × 10 −4 mol L −1. The analysis of confiscated samples by the proposed method indicated cocaine levels from 37% to 95% (m/m) and these results were validated by comparison to HPLC technique, being obtained good correlation between both methods.

Electrocatalytic oxidation of l-cysteine with a stable copper–cobalt hexacyanoferrate electrochemically modified carbon paste electrode

Abstract A stable composition of hybrid copper–cobalt hexacyanoferrate (Cu–CoHCF) film was electrodeposited on a carbon paste electrode (CPE). There are a few reports for using this hybrid as a mediator, but all of them require almost 12 h conditioning time before usage. Contrary to previous reports this electrode does not require any conditioning and can be used immediately after film formation. The electrocatalytic activity of this film was investigated and showed a good electrocatalytic effect for oxidation of l -cysteine (Cys) in phosphate buffer solution (PBS) in pH range of 1–7. A linear range of 6 μM to 1 mM of Cys and an experimental detection limit of 5 μM of Cys were obtained using cyclic voltammetry method. The diffusion coefficient of Cys and catalytic rate constant for electrocatalytic reaction were also calculated. The major problem reported in electro oxidation of Cys is poisoning of electrode surface with reaction product, but in this study oxidation of Cys had no significant fouling effect on the modified electrode surface for the concentrations below 0.5 mM of Cys.

Electrooxidation and Determination of Dopamine Using a Nafion®-Cobalt Hexacyanoferrate Film Modified Electrode.

The electrocatalysis of dopamine has been studied using a cobalt hexacyanoferrate film (CoHCFe)-modified glassy carbon electrode. Using a rotating disk CoHCFe-modified electrode, the reaction rate constant for dopamine was found to be 3.5 × 105 cm³ mol-1 s-1 at a concentration of 5.0 × 10-5 mol L-1. When a Nafion® film is applied to the CoHCFe-modified electrode surface a high selectivity for the determination of dopamine over ascorbic acid was obtained. The analytical curve for dopamine presented linear dependence over the concentration range from 1.2 × 10-5 to 5.0 × 10-4 mol L-1 with a slope of 23.5 mA mol-1 L and a linear correlation coefficient of 0.999. The detection limit of this method was 8.9 × 10-6 mol L-1 and the relative standard deviation for five measurements of 2.5 × 10-4 mol L-1 dopamine was 0.58%.

Preparation, Characterization, and Electrocatalytic Properties of Cobalt Oxide and Cobalt Hexacyanoferrate Hybrid Films

AbstractPolynuclear mixed‐valent films of cobalt oxide and cobalt hexacyanoferrate (CoOCoHCF) have been deposited on electrode surfaces from a solution of Co2+ and Fe(CN)63− ions by repetitive potential cycling method. Simultaneous cyclic voltammetry and electrochemical quartz crystal microbalance measurements demonstrate the steady growth of modified film. The effect of type of monovalent cations as well as acidity of the supporting electrolyte on film growth and redox behavior of resulting film was investigated. In pure supporting electrolyte, electrochemical responses of modified electrode resemble with that of a surface immobilized redox couple. The hybrid film electrodes showed electrocatalytic activity toward oxidation of NADH, hydrazine and hydroxylamine. The feasibility of using our modified electrodes for analytical application was also explored.

Characterization and Electrocatalytic Property of Cobalt Hexacyanoferrate Film on Carbon Nanotubes Modified Gold Electrode

Cobalt hexacyanoferrate (CoHCF) film was formed on multiwalled carbon nanotubes (MWNTs) modified gold electrode by electrodeposition from 0.5 M KCl solution containing CoCl2 and K3Fe(CN)6. The electrochemical behavior and the electrocatalytic property of the modified electrode were investigated. Compared with CoHCF/gold electrode, the CoHCF/MWNTs/gold electrode exhibits greatly improved stability and enhanced electrocatalytic activity toward the oxidation of thiosulfate. A linear range from 5.0×10−5 to 6.5×10−3 M (r=0.9990) for thiosulfate detection at the CoHCF/MWNTs/gold electrode was obtained, with a detection limit of 2.0×10−5 M (S/N=3).

Amperometric determination of paracetomol by a surface modified cobalt hexacyanoferrate graphite wax composite electrode

A stable electro active thin film of cobalt hexacyanoferrate (CoHCF) was deposited on the surface of an amine adsorbed graphite wax composite electrode using a simple method. Cyclic voltammetric experiments showed two pairs of well defined peaks for this CoHCF modified electrode which exhibited excellent electrocatalytic property for the oxidation of paracetomol at a reduced overpotential of 100 mV and over a concentration range of 3.33 × 10 −6 to 1.0 × 10 −3 M with a slope of 0.208 μA/μM with good sensitivity. The influence of the supporting electrolyte on peak current and peak potential were also obtained in addition with effects of common interference (e.g., ascorbic acid) on the response of the modified electrode. Various parameters that influence the electrochemical behavior of the modified electrode were optimized by varying scan rates and pH. Electrochemical impedance spectroscopy studies suggested that the electrode reaction of the CoHCF film is mainly controlled by transport of counter ion. The immobilized CoHCF maintained its redox activity showing a surface controlled electrode reaction with the electron transfer rate constant ( K s) of 0.94 s −1 and charge transfer coefficient of 0.42. Hydrodynamic and chronoamperometric studies were done to explore the utility of the modified electrode in dynamic systems. The results of the differential pulse voltammetry (DPV) using the modified electrode was applied for the determination of paracetomol in commercially available tablets. The results obtained reveal that the electrode under study could be used as an effective sensor for online monitoring of paracetomol.

Surface modification of amine-functionalised graphite for preparation of cobalt hexacyanoferrate (CoHCF)-modified electrode: an amperometric sensor for determination of butylated hydroxyanisole (BHA)

A cobalt hexacyanoferrate (CoHCF)-modified graphite paraffin wax composite electrode was prepared by a new approach. An amine-functionalised graphite powder was used for the fabrication of the electrode. A functionalised graphite paraffin wax composite electrode was prepared and the surface of the electrode was modified with a thin film of CoHCF. Various parameters that influence the electrochemical behaviour of the modified electrode were studied by varying the background electrolytes, scan rates and pH. The modified electrode showed good electrocatalytic activity towards the oxidation of butylated hydroxyanisole (BHA) under optimal conditions and showed a linear response over the range from 7.9 x 10(-7) to 1.9 x 10(-4) M of BHA with a correlation coefficient of 0.9988. The limit of detection was 1.9 x 10(-7) M. Electrocatalytic oxidation of BHA was effective at the modified electrode at a significantly reduced potential and at a broader pH range. The utility of the modified electrode as an amperometric sensor for the determination of BHA in flow systems was evaluated by carrying out hydrodynamic and chronoamperometric experiments. The modified electrode showed very good stability and a longer shelf life. The modified electrode was applied for the determination of BHA in spiked samples of chewing gum and edible sunflower oil. The advantage of this method is the ease of electrode fabrication, good stability, longer shelf life, low cost and its diverse application for BHA determination.