Redox Reactions of Bio Molecule for Nano-bio Battery
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0915-R03-14
Redox Reactions of Bio Molecule for Nano-bio Battery Kwang Min Shin, Sang Jun Park, Seong Gil Yoon, Chang Kee Lee, Su Ryon Shin, Min Kyoon Shin, Bon Kang Gu, Min Sup Kim, and Seon Jeong Kim Hanyang University, Seoul, Korea, Republic of
ABSTRACT Metal oxide nanoparticles within the protein ferritin can act as an energy storage source in nano-bio batteries containing ferrous ferritin and a reconstituted ferritin cage containing different inorganic elements, such as Co, Mn, Ni, and Pt. These components were introduced as two ferritin half-cells with different redox potentials existing between the ferrous ferritin and the reconstituted ferritin. The reduction of ferritin was analyzed in a solution containing 3-[Nmorpholino] propanesulfonic acid buffer and oxidized methyl viologen using cyclic voltammetry. The reduction and oxidation peaks of the methyl viologen occurred at potentials of –700 and –600 mV, respectively, and the reduction and the oxidation peaks of the released Fe occurred at potentials of –300 and –100 mV, respectively. The reduction of ferritin was influenced by the pH of the ferritin solution. INTRODUCTION Nanotechnology is a challenging area of technology. Even though the development of nanoscale devices has accelerated recently, the development of micro- and nanoscale energy storage technology has not been seriously considered. Moreover, the power systems used for many micro- and nanoscale devices are larger than the devices themselves, and a nanoscale power system is highly sought after for nanoscale devices to be successful. The nano-bio battery concept is based on using the bioinorganic protein ferritin, which has an inner metallic core, which is reconstituted with both an iron and a cobalt core.1–3 Ferritin is an iron storage protein that is found in animals, humans, and even bacteria, and it can sequester up to 4,500 Fe(III) atoms in its core. It consists of 24 monomer units, and its outer diameter is 12 nm and its inner diameter is around 7.5 nm.4 Ferritin forms a stable and robust structure that is able to withstand biological extremes.5 In the biomineralized reconstitution process of the ferritin core, ferritin can be loaded with different core materials—for example, cobalt6 or manganese7—each having a different redox capability. Nano-bio batteries have little weight, have a high energy density, and because of their small size, can function as a chip-scale power source. The capacity of a nano-bio battery is determined by two factors: the difference in redox potential between the two electrodes, and the number of ferritin molecules in a unit electrode area. The redox reaction between each ferritin molecule with different core materials involves the transfer of an electron from a donor to an accepter molecule. In this process, ferritin is loaded with reduced Fe(II) ions in the core acting as the electron donor or the anode in a battery cell, and cobalt cored ferritin acts as the electron acceptor or the cathode. Furthermore, reconstituted ferritin containing various core materials
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