This article reviews fundamental aspects of deposition, structure and electrochemistry of Prussian Blue and its analogues. Special attention is given to the metal hexacyanoferrates with potential analytical applications. Prussian Blue and its analogues as advanced sensing materials for nonelectroactive ions are discussed. In contrast to common ‘smart materials’, the sensitivity and selectivity of metal hexacyanoferrates to such ions is provided by thermodynamic background. Prussian Blue itself is recognized as the most advantageous low-potential transducer for hydrogen peroxide over all known systems. Both high sensitivity (ca. 1 A M−1 cm−2) and selectivity in relation to oxygen reduction are more than three orders of magnitude higher, than for platinum electrodes. Biosensors based on different transducing principles containing enzymes oxidases are compared, and the devices operated due to hydrogen peroxide detection with the Prussian Blue based transducer are shown to be the most advantageous ones. The future prospects of chemical and biological sensors based on metal hexacyanoferrates are outlined.

Prussian Blue and Its Analogues: Electrochemistry and Analytical Applications

Electrochemistry of Methylene Blue Bound to a DNA-Modified Electrode

This review focuses on the electrosynthesis, in situ characterization, and technological applications of Prussian blue analogues with the generic formula AhMk[Fe(CN)6]l·mH2O, where h, k, l, and m are stoichiometric numbers, A = alkali metal cation, and M is a transition metal. Six such metal hexacyanoferrate (MHCF) compounds derived from Cu, Pd, In, V, Co, and Ni are featured in this article against the backdrop of the Prussian blue parent compound itself and other related compounds. The use of cyclic voltammetry and complementary techniques including scanning probe microscopies, quartz crystal microgravimetry, and ac impedance spectroscopy, for studying the growth of MHCF films on targeted substrates, is discussed. Spectroelectrochemical in situ characterization of these films in the UV−visible and IR regions is then reviewed. Finally, the use of Prussian blue and its analogues in devices for displays and “smart” windows, photoimaging, environmental remediation, chemical/biological sensing, energy conver...

Metal Hexacyanoferrates: Electrosynthesis, in Situ Characterization, and Applications

The electrocatalytic properties of multi-walled carbon nanotube modified electrodes toward the oxidation of NADH are critically evaluated. Carbon nanotube modified electrodes are examined and compared with boron-doped diamond and glassy carbon electrodes, and most importantly, edge plane and basal pyrolytic graphite electrodes. It is found that CNT modified electrodes are no more reactive than edge plane pyrolytic graphite electrodes with the comparison with edge plane and basal plane pyrolytic graphite electrodes allowing the electroactive sites for the electrochemical oxidation of NADH to be unambiguously determined as due to edge plane sites. Using these highly reactive edge plane sites, edge plane pyrolytic graphite electrodes are examined with cyclic voltammetry and amperometry for the electroanalytical determination of NADH. It is demonstrated that a detection limit of 5 µM is possible with cyclic voltammetry or 0.3 µM using amperometry suggesting that edge plane pyrolytic graphite electrodes can conveniently replace carbon nanotube modified glassy carbon electrodes for biosensing applications with the relative advantages of reactivity, cost and simplicity of preparation. We advocate the routine use of edge plane and basal plane pyrolytic graphite electrodes in studies utilising carbon nanotubes particularly if ‘electrocatalytic’ properties are claimed for the latter.

Exploring the electrocatalytic sites of carbon nanotubes for NADH detection: an edge plane pyrolytic graphite electrode study

Understanding the electro-catalytic oxidation mechanism of urea on nickel electrodes in alkaline medium

The electrochemical behavior of methylene blue (MB) at a carbon fiber microcylinder electrode, was studied by cyclic voltammetry. The charge transfer coefficient α of the electrode reaction with two-electron transfer is 0.5, and the number of H+ participating in the electrode process is 3 at pH 2.2–5.4, 2 at pH 5.4–6.0 and 1 at pH 6.0–10.7, respectively. The standard electron transfer rate constant ko′, and standard formal potential Eo′ of MB at various pH were determined by using the carbon fiber microcylinder electrode. The electrode reaction mechanism of methylene blue at various pH is proposed. The adsorbability of MB at the electrode is discussed and explored by cyclic voltammetry and chronocoulometric technique.

The electrochemical behavior of methylene blue at a microcylinder carbon fiber electrode

Cobalt hexacyanoferrate modified microband gold electrode and its electrocatalytic activity for oxidation of NADH

Catalytic oxidation of reduced nicotinamide adenine dinucleotide at a microband gold electrode modified with nickel hexacyanoferrate

The effects of temperature and electrolyte on the redox potential of cytochrome c at a chemically modified microband gold electrode

A new amperometric electrode for the assay of lactate dehydrogenase (LDH) is prepared by modifying a nanometer—sized microband gold electrode with nickel hexacyanoferrate. The amperometric determination bases on electrochemically detecting NADH produced by the enzymatic reaction of lactate with NAD+ under the catalysis of LDH. The modified electrode can sensitively detect LDH at +0.55V vs. SCE with a linear response in the range of 10U / mL to 350U / mL under optimum conditions.

Chen-Xin Cai

Papers

The electrochemical behavior of methylene blue at a microcylinder carbon fiber electrode

Cobalt hexacyanoferrate modified microband gold electrode and its electrocatalytic activity for oxidation of NADH

Catalytic oxidation of reduced nicotinamide adenine dinucleotide at a microband gold electrode modified with nickel hexacyanoferrate

The effects of temperature and electrolyte on the redox potential of cytochrome c at a chemically modified microband gold electrode

Determination of Lactate Dehydrogenase by the Electrochemical Oxidation of Nadh at a Modified Microband Gold Electrode