Enzymeless voltammetric hydrogen peroxide sensor based on the use of PEDOT doped with Prussian Blue nanoparticles

An electrochemical sensor for H₂O₂ was developed based on electrochemically deposited Prussian blue (PB) nanoparticles doped poly(3,4-ethylenedioxythiophene) (PEDOT). The PEDOT/PB composite was composed of PEDOT wrapped PB nanoparticles, where the conducting polymer PEDOT not only protected the PB particles to warrant high stability, but also connected them to enhance the electron transfer. Owing to the excellent conductivity of PEDOT and unique electrocatalytic activity of PB, the PEDOT/PB modified electrode exhibited good catalytic activity toward the electrochemical reduction of H₂O₂, and was used for the detection of H₂O₂ in concentrations ranging from 0.5 to 839 μM, with a detection limit of 0.16 μM. Moreover, the sensor also demonstrated excellent reproducibility, selectivity and long-term stability, showing great promise for the fabrication of electrochemical sensors and H₂O₂ related biosensors.

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Graphical abstract An electrochemical non-enzymatic sensor for hydrogen peroxide with excellent stability was developed. It is based on conducting polymer PEDOT doped with Prussian blue nanoparticles.

     

Voltammetric determination of paracetamol using a glassy carbon electrode modified with Prussian Blue and a molecularly imprinted polymer,and ratiometric read-out of two signals

The authors report on a ratiometric electrochemical sensor for paracetamol (PR) which was fabricated by successively electropolymerizing a layer of Prussian blue (PB) and a layer of molecularly imprinted polypyrrole (MIP) on the surface of a glassy carbon electrode (GCE). The binding of PR molecules to the MIP has two effects: The first is an increase of the oxidation current for PR at 0.42 V (vs. SCE), and the second is a decrease in the current for PB (at 0.18 V) due to partial blocking of the channels which results in reduced electron transmissivity. Both currents, and in particular their ratio, can serve as analytical information. Under optimized conditions, the sensor displays enhanced sensitivity for PR in the 1.0 nM to 0.1 mM concentration range and a 0.53 nM lower limit of detection. The sensor was applied to the determination of PR in tablets and urines where it gave recoveries in the range between 94.6 and 104.9 %. This dual-signal (ratiometric) detection scheme (using electropolymerized Prussian Blue and analyte-specific MIP) in our perception has a wide scope in that it may be applied to numerous other electroactive species for which specific MIP can be made available.

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Graphical Abstract Prussian blue (PB) and molecularly imprinted polymer (MIP) were combined to fabricate an electrochemical sensor for paracetamol (PR) detection. The ratio of both currents, increase of PR current and decrease of PB current, was employed for PR selective detection with enhanced sensitivity.

     

Electrochromic properties of Prussian blue–polypyrrole composite films in dependence on parameters of synthetic procedure

Composite materials of Prussian blue–polypyrrole (PB/PPy) on the surface of indium tin oxide (ITO)-coated glasses were obtained via one-step chemical (redox) and one-stage electrochemical procedures in mixed solution of iron (III), hexacyanoferrate (III), and pyrrole with various concentration ratios of components in nitrate supporting electrolyte. Electrochemical stability of composite films depends on the amount of Py in synthetic solution, whereas color contrast coefficient values depend on the type of synthetic procedure. PB/PPy film electrochromic response (tested by spectroelectrochemical potentiodynamic measurements) was compared with response of both pure PB and pure PPy films. It was shown that degradation of composite films occurs due to PB component instability in Prussian white form. The highest value of color contrast coefficient and great electrochemical stability were revealed for composite films obtained via redox-synthesis procedure from solution with 0.1 mM [Fe³⁺ + Fe(CN)₆ ^3?] and 1.0 mM Ру (PB/PPy-Ch-1:1:10 system).     

Label-free electrochemical immunosensor for the carcinoembryonic antigen using a glassy carbon electrode modified with electrodeposited Prussian Blue, a graphene and carbon nanotube assembly and an antibody immobilized on gold nanoparticles

We described a sensitive, label-free electrochemical immunosensor for the detection of carcinoembryonic antigen. It is based on the use of a glassy carbon electrode (GCE) modified with a multi-layer films made from Prussian Blue (PB), graphene and carbon nanotubes by electrodeposition and assembling techniques. Gold nanoparticles were electrostatically absorbed on the surface of the film and used for the immobilization of antibody, while PB acts as signaling molecule. The stepwise assembly process was investigated by differential pulse voltammetry and scanning electron microscopy. It is found that the formation of antibody-antigen complexes partially inhibits the electron transfer of PB and decreased its peak current. Under the optimal conditions, the decrease of intensity of the peak current of PB is linearly related to the concentration of carcinoembryonic antigen in two ranges (0.2–1.0, and 1.0–40.0 ng·mL^?1), with a detection limit of 60 pg·mL^?1 (S/N?=?3). The immunosensor was applied to analyze five clinical samples, and the results obtained were in agreement with clinical data. In addition, the immunosensor exhibited good precision, acceptable stability and reproducibility.

Single microparticle applied in magnetic-switchable electrochemistry

In this work we demonstrated the micromanipulation of a single magnetic microparticle (Fe₃O₄) modified with Prussian blue (PB) for use in magnetic-switchable electrochemistry. A single Fe₃O₄-PB microparticle with 120 μm was isolated in an electrochemical microcell (20 μL), in which a fine control of PB electrochemical process on carbon electrode (Ø = 4.0 mm) was obtained. For cyclic voltammetry, redox processes attributed to PB/PW (Prussian blue/Prussian white) one electron redox couple were observed, however the capacitive currents were very high. On the other hand, by using differential pulse voltammetry, a maximum faradaic current for anodic peak of 200 nA cm^− 2 at 0.06 V was observed. Several and high stable chronoamperograms were obtained by “switch on” and “switch off” magnetic commutative states for a single microparticle, showing that the system developed here can be very promising for application in electrochemistry.     

Simultaneous sensing of L-tyrosine and epinephrine using a glassy carbon electrode modified with nafion and CeO2 nanoparticles

An electrochemical sensor was developed and tested for detection of L-tyrosine in the presence of epinephrine by surface modification of a glassy carbon electrode (GCE) with Nafion and cerium dioxide nanoparticles. Fabrication parameters of a surfactant-assisted precipitation method were optimized to produce 2–3 nm CeO₂ nanoparticles with very high surface-to-volume ratio. The resulting nanocrystals were characterized structurally and morphologically by X-ray diffractometery (XRD), scanning and high resolution transmission electron microscopy (SEM and HR-TEM). The nanopowder is sonochemically dispersed in a Nafion solution which is then used to modify the surface of a GCE electrode. The electrochemical activity of L-tyrosine and epinephrine was investigated using both a Nafion-CeO₂ coated and a bare GCE. The modified electrode exhibits a significant electrochemical oxidation effect of L-tyrosine in a 0.2 M Britton-Robinson (B-R) buffer solution of pH 2. The electro-oxidation peak current increases linearly with the L-tyrosine concentration in the molar concentration range of 2 to 160 μM. By employing differential pulse voltammetry (DPV) for simultaneous measurements, we detected two reproducible peaks for L-tyrosine and epinephrine in the same solution with a peak separation of about 443 mV. The detection limit of the sensor (signal to noise ratio of 3) for L-tyrosine is ~90 nM and the sensitivity is 0.20 μA μM^?1, while for epinephrine these values are ~60 nM and 0.19 μA μM^?1. The sensor exhibited excellent selectivity, sensitivity, reproducibility and stability as well as a very good recovery time in real human blood serum samples.

Simultaneous electrochemical determination of L-tyrosine and epinephrine in blood plasma with Nafion-CeO₂/GCE modified electrode showing a 443 mV peak-to-peak potential difference between species oxidation peak currents.     

Electrochemical and electrocatalytic stability of Prussian blue/Berlin green redox transformation in Prussian blue-polypyrrole composite films

Redox transformation of Prussian blue to Berlin green (PB/BG) in Prussian blue-polypyrrole (PB-PPy) composites synthesized via original one-step method has been studied. It was shown that the nature of anion and composition of background electrolyte play an important role for both the stability and the shape of electrochemical response of composite film during redox transfer of Prussian blue to Berlin green. Nitric acid, phosphoric acid, malic acid and citric acid 0.05 N (eq/L) solutions and the same acids partially neutralized with 0.01 N KOH were used as electrolyte to study the role of potassium ions presence in solution. The most stable electrochemical response of PB/BG redox transfer was obtained for the nitrate anions containing solutions in the presence of potassium ions. Nevertheless, the stability of the electrochemical transformation PB/BG in composite films in other media is enough to detect the sulphite ions content in wine samples via electrocatalytic reaction at the potentials of PB/BG redox transformation.

     

Determination of Rutin in Drinks Using an Electrode Modified with Carbon Nanotubes-Prussian Blue

A new sensor was developed using a screen-printed carbon electrode modified with single-walled carbon nanotubes (SWCNTs) and Prussian blue (PB) coated with chitosan. The modified electrode allowed the oxidation and reduction of rutin at 0.25 and 0.096 V, respectively, with a ΔE of 0.154 V. Furthermore, the peak currents increase nearly 100% compared with the electrode without modification. The process was more reversible compared with the electrode modified with only SWCNTs or PB. Cyclic voltammetry was used to characterize the modified electrode surface. The quantification of rutin was more sensitive with adsorptive stripping voltammetry than with anodic stripping voltammetry. Adsorption potential, adsorption time and pH were optimized based on the oxidation of rutin: E_ads =–0.10 V, t_ads = 60 s, pH 3.0. The detection limit (3σ/b) was 0.01 μM and the relative standard derivation was 3%. The new sensor was used in the quantification of rutin in black tea, coffee and synthetic drink of tea with satisfactory results.     

Non-enzymatic sensing of hydrogen peroxide using a glassy carbon electrode modified with the layered MoS<Subscript>2</Subscript>-reduced graphene oxide and Prussian Blue

The authors describe an electrochemical sensor for hydrogen peroxide (H₂O₂). It was constructed by consecutive, selective modification of a glassy carbon electrode (GCE) with Prussian Blue (PB), layered molybdenum disulfide (MoS₂), and reduced graphene oxide (rGO). The properties of the modified GCE were characterized via high-resolution transmission electron microscopy, UV-vis spectroscopy and X-ray diffraction. The electrochemical properties of the electrode were studied using cyclic voltammetry and electrochemical impedance spectroscopy. The sensor exhibits excellent electrocatalytic activity for the reduction of hydrogen peroxide in comparison to GCEs modified with MoS₂-rGO or PB only. Response is linear in the 0.3 μM to 1.15 mM H₂O₂ concentration range at a working analytical voltage of 0.1 V, with a 0.14 μM detection limit. The electrochemical sensitivity is 2883.5 μA·μM^?1·cm^?2, and response is fast (<10 s). The sensor is selective, stable and reproducible. This is attributed to the efficient electron transport properties of the MoS₂-rGO composite and the high loading with PB.

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Graphic abstract Prussian Blue nanoparticles were deposited on MoS₂-rGO modified glassy carbon electrode by electrochemical method. This sensor was used for the detection of H₂O₂ in tap water and river water.

     

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.

     

Electroanalytical Study of Prussian Blue Modified Glassy Carbon Paste Electrodes

Two types of glassy carbon (GC) powder (i.e., Sigradur K and Sigradur G) have been mixed with mineral oil to obtain glassy carbon paste electrodes (GCPE's). The electrochemical behavior of such electrodes at different percentages of glassy carbon has been evaluated with respect to the electrochemistry of ferricyanide as revealed with cyclic voltammetry and the best paste composition was chosen. GC was then modified with Prussian Blue (PB), mixed at different percentages with unmodified GC and with a fixed amount of mineral oil in order to obtain PB modified glassy carbon paste electrodes (PB‐GCPE's). PB‐GCPE's with different percentages of GC modified with PB (PB‐GC) were compared and the dependence on the amount of PB on their performances was evaluated by studying the parameters of cyclic voltammetry (i.e., current peak, ΔE_p, anodic and cathodic current ratio, charge density) and the amperometric response to H₂O₂. Data interpretation based on the GC surface area is presented. GCPE's with a selected amount of PB‐GC were then tested as H₂O₂ probes and all the analytical parameters together with the dependence on pH were evaluated. Some preliminary experiments with these electrodes assembled as glucose, lysine and lactate biosensors are also reported.     

Enhanced stability of a Prussian blue/sol-gel composite for electrochemical determination of hydrogen peroxide

We have prepared a sol–gel that incorporates Prussian Blue (PB) as a redox mediator. It is shown that the PB in the pores of the sol–gel retains its electrochemical activity and is protected from degradation at acidic and neutral pH values. TEM and EDX studies revealed the PB nanoparticles to possess a cubic crystal structure and to be well entrapped and uniformly dispersed in the pores of the matrix. The electrocatalytic activity of the materials toward hydrogen peroxide (H₂O₂) was studied by cyclic voltammetry and amperometry. The modified electrode displays good sensitivity for the electrocatalytic reduction of H₂O₂ both in acidic (pH 1.4) and neutral media. The sensor has a dynamic range from 3 to 210 μM of H₂O₂, and the detection limit is 0.6 μM (at an SNR of 3).

Binary and Ternary Copper(II) Complexes with NIPAAm/IA Copolymers and Aminoacids: Interpretation of UV‐Visible Spectra and Cyclic Voltammograms

The complex formations of homopolymers and copolymers of poly(N‐isopropyl acrylamide) (PNIPAAm), polyacrylamide (PAAm) and poly(itaconic acid) (PIA) with Cu(II) ions in aqueous solutions were studied by using UV‐visible spectra in the region of 200–1100 nm and cyclic voltammograms between ?0.800 V and 0.600 V. According to the optical and electrochemical spectra of the polymer‐ and copolymer‐Cu(II) complexes and their ternary complexes with alanine, i.e., absorptions and the shifts in the wavelength of the maximum absorptions, currents and potentials of the peaks in the pH range of 3–12, the intensities of anodic and cathodic peak currents of polymers containing IA groups decrease with increasing pH and they show maximum absorptions at lower wavelengths than do the homopolymers used in this work. The peak point of the visible band shifts from 800 to 650 nm, with increasing pH, while the intensity of the third anodic peak observed after pH=4 increases in the case of both Ala‐Cu(II) and its ternary solution with P(NIPAAm‐co‐IA, 9.8 mol%). Both the pH‐dependent shifts of maximum absorptions and the appearence of the third anodic peaks as the pH raised were interpreted as a presence of tetracoordinated Cu(II) complexes in the solution and on the electrode surface, involving combined carboxyl, amide and amine interaction.     

Utilization of Pyronine B as Voltammetric Probe for the Determination of DNA

Abstract

The electrochemical behaviors of the interaction of pyronine B (PB) with DNA were investigated on the mercury drop working electrode. In pH 2.0 Britton‐Robinson (B‐R) buffer solution, PB can be easily reduced on the mercury electrode and had a well‐defined voltammetric reductive wave at ?0.86 V (vs. saturated calomelelectrode, SDE). On the addition of DNA into the PB solution, the reductive peak current of PB decreased with the positive movement of the peak potential and without the appearance of new peaks. The result showed that a new supramolecular complex was formed via intercalation of PB with DNA, which can't be reduced on the Hg electrode. The conditions of interaction and the electrochemical detection were carefully investigated. Under the optimal conditions the decrease of peak current was proportional to the concentration of DNA in the range of 1.0～30.0 mg/L with the linear regression equation as ΔIp″(nA)=51.84C (mg/L)–94.97 (n=13, γ=0.993) and the detection limit was 0.90 mg/L. The interaction mechanism was discussed with the aggregation of DNA‐PB supramolecular complex and the stoichiometry of the supramolecular complex was calculated with the binding number as 3 and the binding constant as 1.61×10¹⁵.     

Application of multivariate optimization method in nanomolar simultaneous determination of morphine and codeine in the presence of uric acid using a glassy carbon electrode modified with a hydroxyapatite-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticle/multiwalled carbon nanotubes composite

The electrochemical oxidation of morphine (MO) and codeine (COD) has been investigated by the application of a novel glassy carbon electrode modified with a hydroxyapatite-Fe₃O₄ nanoparticles/multiwalled carbon nanotubes composite (HA-FeNPs-MWCNTs/GCE). The modified electrode worked as an efficient sensor for simultaneous determination of MO and COD in the presence of uric acid. Response surface methodology was utilized to optimize the voltammetric response of the modified electrode for the determination of MO and COD. The amount of HA-FeNPs in the modifier matrix (%HA-FeNPs), the solution pH and the accumulation time were chosen as the three important operating factors through the experimental design methodology. The central composite design as a response surface approach was applied for obtaining the optimum conditions leading to maximum oxidation peak currents for MO and COD. The differential pulse voltammetry results showed that the obtained anodic peak currents were linearly proportional to concentration in the range of 0.08–32 µM with a detection limit (S/N = 3.0) of 14 nM for MO and in the range of 0.1–28 µM and with a detection limit of 22 nM for COD. The proposed method was successfully applied to determine these compounds in human urine and blood serum samples.     

Hydrogen diffusivity in the massive LaNi5 electrode using voltammetry technique

The Randles–Sev?ik relationship has been applied to evaluate atomic hydrogen diffusivity in massive LaNi₅ intermetallic compound. The electrode was cathodically hydrogenated in 6 M KOH solution (22 °C), and then voltammetry measurements were carried out at various, very slow potential scan rates (υ?=?0.01–0.1 mV?·?s^?1). At potentials more noble than the equilibrium potential of the H₂O/H₂ system, the anodic peaks were registered as a consequence of oxidation of hydrogen absorbed in cathodic range. The peak potentials linearly increase with the logarithm of the scan rate with a slope of 0.059 V. The slope testifies to a symmetric charge transfer process with symmetry factor α?=?½. The peak currents linearly increase with the square root of the potential scan rate, and the straight line runs through the origin of the coordinate system. The slope of the I _a ^(peak) ?=?f(υ ^1/2) straight line is a measure of the atomic hydrogen diffusion coefficient. Assuming the hydrogen concentration in the LaNi₅ material after cathodic exposure to be C _0,H?=?0.071 mol?·?cm^?3 (63 % of theoretical value), the hydrogen diffusion coefficient equals D _H?=?2.0?·?10^?9 cm²s^?1. Extrapolation of rectilinear segments of potentiodynamic polarization curves with Tafel slopes of 0.12 V and linear polarization dependencies from voltammetry tests allowed the exchange current densities of the H₂O/H₂ system on the tested material to be determined. The exchange current densities on initially hydrogenated LaNi₅ alloy are close to 1 mA?·?cm^?2, irrespective of the electrode potential scan rate.     

Enhancement of the Electrochemical Performance of Prussian Blue Modified Electrode via Ionic Liquid Treatment

This article first reports the preparation of a Prussian blue (PB) modified electrode with improved electrochemical properties at the functionalized glass carbon electrode (GC) by imidazolium based ionic liquid. The molecular ionic liquid film on the GC electrode has been found to influence the electrodeposition of PB by a way of enhancement of voltammetric currents, suggesting efficient electrodepositon. Such efficient electrodeposition was caused by the static electric effect which existed between the positively charged imidazolium group on the electrode surface and the negative ferric‐ferricyanide in solution. Compared with the PB/GC electrode, the PB/[Bmim][Cl]/GC electrode showed much better electrochemical stability after successive potential cycling for 250 cycles. A comparative study on amperometric responses of both electrodes to reduce H₂O₂ was also investigated. PB/[Bmim][Cl]/GC electrode showed a better electrocatalytic performance to H₂O₂ with wider linear detection range and higher sensitivity than that at the electrode without [Bmim][Cl]. Furthermore, the kinetics for both electrodes was discussed. The PB/[Bmim][Cl]/GC electrode possessed a greater diffusion coefficient.     

Fabrication of Fe3O4 Nanoparticles Modified Electrode and Its Application for Voltammetric Sensing of Dopamine

Magnetic nanoparticles of Fe₃O₄ approximately 5nm in size were synthesized and characterized by XRD and TEM. A novel gold electrode modified with Fe₃O₄ nanoparticles was then constructed and was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The modified electrode exhibited strong promoting effect and high stability toward the electrochemical oxidation of dopamine (DA), which gave reversible redox peaks with a formal potential of 0.192 V (vs. Ag/AgCl) electrode in pH 7.0 phosphate buffer solution (PB). The anodic peak currents (measured by constant potential amperometry) increased linearly with the concentration of dopamine in the range of 1.5×10^?7 to 4.0×10^?4 M. The detection limit (S/N=3) obtained was 3.0×10^?8 M. The relative standard deviation (RSD) of 8 successive scans was 3.41% for 1.5×10^?6 M DA. The interference of ascorbic acid (AA) could be eliminated efficiently. The proposed method showed excellent sensitivity and recovery.     

Determination of Rutin by a Graphene-Modified Glassy Carbon Electrode

A reduced graphene oxide-modified glassy carbon electrode for sensitive detection of rutin is reported. The modified electrode was obtained by one-step electrochemical reduction of graphene oxide on the bare glassy carbon electrode. In the presence of graphene, an enhanced electrochemical response for rutin appeared with a pair of well-defined anodic and cathodic peaks in pH 3.0 phosphate buffer. Under the optimized conditions, the anodic peak currents exhibited a linear relationship with rutin concentration from 0.1 to 2.0 µM with a detection limit of 23.2 nM. The modified electrode was employed to the analysis of tablets (with satisfactory recovery of 19.96 mg/per tablet) and Flos Sophorae. The graphene-modified electrode exhibited high sensitivity, good stability, and selectivity for the determination of rutin.     

Gold Nanowires – Assisted Prussian Blue Enhancing Peroxidase – Like Activity for the Non-enzymatic Electrochemically Sensing H2O2 Released From Living Cells

Prussian blue nanoparticles (PBNPs) have peroxidase-like activity for H₂O₂. However, PB alone have poor electrochemical performances. Herein, a strategy was proposed by direct in-situ growth PBNPs onto gold nanowires (AuNWs) surface to obtain the peroxidase-like activity with about 4.05 times higher than that of PBNPs alone. PBNPs@AuNWs was employed to construct a non - enzymatic electrochemical H₂O₂ sensor with the detection limit of 5.3×10⁻⁹ mol/L (S/N=3). The sensor was successfully used to detect H₂O₂ in human serum samples or secreted from living HeLa cells. It may be a competitive candidate for H₂O₂ assaying in biological samples or cellular investigation.