ИСТИНА

Prussian Blue, PB (ferric(III) hexacyanoferrate(II)) is a promising electrocatalytic material for hydrogen peroxide (H2O2) detection[1], hence PB-modified electrodes are of great interest especially in miniaturized biosensors. In contrast to the relatively high potential (0.6 V vs. Ag/AgCl) for H2O2 oxidation at platinum electrodes, modification with PB provides moderate electrochemical conditions (0 V vs. Ag/AgCl), an higher rate constant and dramatically improved selectivity[2]. The disadvantage of the limited stability of PB particular in higher H2O2 concentration can be attenuated by e.g. codeposition of PB and nickel-hexacyanoferrate (NiHCF)[2]. Ultramicroelectrodes (UME) were successfully modified with PB or PB/NiHCF films and applied for imaging H2O2 distribution in combination with scanning electrochemical microscopy (SECM), respectively[3,4]. Here we present PB/NiHCF-modified atomic force-scanning electrochemical microscopy (AFM-SECM) probes with mixed layers of PB/NiHCF, which were electrochemically deposited. Besides a thorough characterization, the stability was investigated in the range of 50 and 430 μM H2O2. In addition, the modified probes were used for imaging the evolution of H2O2 at a platinum UME (diam. 25 μm), biased at -0.4 V vs. Ag/AgCl, while simultaneously the topography was recorded. First results towards imaging of H2O2 at a bio-relevant sample will be presented. With this approach, H2O2 can be detected at moderate potential, while simultaneously the evolution of H2O2 can be directly correlated to topographical characteristics of a sample. [1] W. Chen, S. Cai, Q.- Q. Ren, W. Wen, Y.- D. Zhao, Recent advances in electrochemical sensing for hydrogen peroxide: a review, Analyst 137 (2012) 49. [2] N. A. Sitnikova, A. V. Borisova, M. A. Komkova, A. A. Karyakin, Superstable advanced hydrogen peroxide transducer based on transition metal hexacyanoferrates, Anal. Chem. 83 (2011) 2359. [3] O. G. Voronin, A. Hartmann, C. Steinbach, A. A. Karyakin, A. R. Khokhlov, C. Kranz, Prussian blue-modified ultramicroelectrodes for mapping hydrogen peroxide in scanning electrochemical microscopy (SECM), Electrochem. Commun. 23 (2012) 102. [4[ M. A. Komkova, A. Holzinger, A. Hartmann, A. R. Khokhlov, C. Kranz, A. A. Karyakin, O. G. Voronin, Ultramicrosensors based on transition metal hexacyanoferrates for scanning electrochemical microscopy, Beilstein J. Nanotechnol. 4 (2013) 649. ise142409