Electrochemical Formation of Prussian Blue in Natural Iron-Intercalated Clay and Cinder Matrixes

Abstract

Natural iron-intercalated clays and waste cinder (from steel industry) were converted into an ef®cient catalyst by electrochemical formation of Prussian blue (PB) directly inside the matrix. The basic electrochemical features for the PB-modi®ed electrodes were investigated by means of cyclic voltammetry technique, in terms of E fwhm , surface charge (q), surface excess (G), site-site interaction model, and ®lm resistivity (R f ), etc. The iron intercalated PB electrodes show superior electrochemical activity and stability over the classical GCE/PB electrodes and were analyzed by the interaction parameter`r'. The more ef®cient electrocatalytic function of the iron intercalated PB electrodes than the GCE/PB was demonstrated with guanine oxidation reaction.Keywords: Clay, Cinder, Prussian blue, GuanineWe report here the ®rst electrochemical evidence for the formation of Prussian blue (PB) directly inside the natural ironriched materials of nontronite and cinder. Earlier studies on clay modi®ed electrodes (CMEs) in the presence of Fe(CN) 6 3À focussed only on the interfacial surface characterization of the modi®ed clays [1±8]. Neither the clay ®lm formed by rapid drying nor the spin-coated CMEs showed the PB formation on the intercalated iron ions [1±8]. Since only a very small amount of clay can be deposited on the electrode surface, the concentration of iron available for PB formation is even lower. Furthermore, the CME prepared by simple evaporation technique has highly porous aerogel structures and the ®lms eventuallỳ`s loughed off'' as platelet to platelet distance increased to a minimum of energy interaction due to osmotic swelling in aqueous solutions [9]. Indeed, the nature of making the electrode, the amount of the material, and its operating concentration, etc., make a crucial modi®cation in the interfacial-structures that may in¯uence the PB formation.In this study, we solve the above problems by preparing the clay=carbon paste electrode (clay=CPE) and cinder=carbon paste electrode (cinder=CPE), which contain a relatively higher amount of clay or cinder. Two natural iron-riched modi®ers of nontronite, [(Si 7.25 , and industrial waste cinder were speci®cally used in this study. The iron content of cinder was experimentally determined as 7272.8 ppm=g by atomic absorption spectroscopy. To verify the iron-carbon intercalated nature of the cinder powders, same measurements were also done for 1 M HNO 3 treated (ca. 2 h at 60 C) cinder powders. The result of 6921.1 ppm=g is only about a 5 % decrease in iron content con®rming the expectation. Another one of the most studied smectite clays, [montmorillonite, (Si 7.84 Note that, even though the amount of iron centers in nontronite is about 7.2 times greater than that in montmorillonite, nontronite has isomorphous substitution in the tetrahedral sheet and montmorillonite is a dioctahedral mineral with substitution mainly in the octahedral sheet [10,11]. Figure 1 shows the continuous cyclic voltammetric (CV) response of the SWa-1=CPE, SWy-1=CPE, and cinde...

A Glucose Biosensor Employing a Stable Artificial Peroxidase Based on Ruthenium Purple Anchored Cinder

“…The processing of the cinder and the preparation of the cinder-modified carbon paste electrode (designated as CPE/CFe*) generally followed our earlier reports. 20,21 Figure 1 shows the systematic scheme for the tailoring procedure of the cinder-modified electrodes. For the preparation of the cinder/ruthenium purple hybrid-modified carbon paste electrode (designated as CPE/CFe*-RP), 2 mM of Ru(CN) 6 4in 0.1 M, pH 2 ammonium buffer solution was continuously cycled for 60 scans at a scan rate of 50 mV/s.…”

Flow Injection Analysis of an Ultratrace Amount of Arsenite Using a Prussian Blue-Modified Screen-Printed Electrode

“…The mediator function of the modified PB layer to the As 3+ oxidation was verified by an obvious oxidation signal at ∼1.0 V versus Ag/AgCl at the PBSPE. According to the established voltammetric characteristics of PB, the two redox peaks at ∼0.2 (A1/C1) and ∼1.0 V (A2/C2) corresponding to the K + -coupled reactions of PB T Everitts salt (ES) and PB T Prussian yellow (PY), respectively, as per the following equations 30,31,[33][34][35][36][37] The increase in anodic response together with a decrease in cathodic peak current at the PB/PY redox process in the presence of As 3+ provides strong evidence for the mediated reaction. Further experiments with increasing scan rate (v) from 5 to 200 mV/s showed a constant slope of ∼0.5 from the log(i pa ) versus log(v) plot for the A2/C2 process regardless of the existence of As 3+ .…”

Estudo espectro eletroquímico de sistemas estruturados argila-corante

“…Eletrodos modificados com compósitos argilominerais vêm sendo desenvolvidos de longa data [4,7,9,[10][11][12][13][14]19,22,[24][25][26][27][28], empregando distintos substratos (Pt, carbono vítreo, eletrodo de pasta de carbono, etc.) e objetivando diferentes aplicações tais como: 1-reconhecimento óptico; 2-desenvolvimento de sistemas eletrocatalíticos; 3-desenvolvimento de eletrodos empregados para determinações eletroanalíticas.…”