Dmitry Pankratov

A hybrid electric power device for simultaneous generation and storage of electric energy

We herein report on an entirely new kind of electric power device. In the hybrid device, chemical energy is directly converted into electric energy, which is capacitively stored within a singular contrivance. The device is built based on dual-function electrodes, viz. discrete electrodes manifesting simultaneous electrocatalytic and charge-storage features.

Interfacial Behavior and Activity of Laccase and Bilirubin Oxidase on Bare Gold Surfaces

Two blue multicopper oxidases (MCOs) (viz. Trametes hirsuta laccase (ThLc) and Myrothecium verrucaria bilirubin oxidase (MvBOx)) were immobilized on bare polycrystalline gold (Au) surfaces by direct adsorption from both dilute and concentrated enzyme solutions. The adsorption was studied in situ by means of null ellipsometry. Moreover, both enzyme-modified and bare Au electrodes were investigated in detail by atomic force microscopy (AFM) as well as electrochemically. When adsorbed from dilute solutions (0.125 and 0.25 mg mL⁻¹ in the cases of ThLc and MvBOx, respectively), the amounts of enzyme per unit area were determined to be ca. 1.7 and 4.8 pmol cm⁻², whereas the protein film thicknesses were determined to be 29 and 30 Å for ThLc and MvBOx, respectively. A well-pronounced bioelectrocatalytic reduction of molecular oxygen (O₂) was observed on MvBOx/Au biocathodes, whereas this was not the case for ThLc-modified Au electrodes (i.e., adsorbed ThLc was catalytically inactive). The initially observed apparent k(cat)(app) values for adsorbed MvBOx and the enzyme in solution were found to be very close to each other (viz. 54 and 58 s⁻¹, respectively (pH 7.4, 25 °C)). However, after 3 h of operation of MvBOx/Au biocathodes, kcatapp dropped to 23 s⁻¹. On the basis of the experimental results, conformational changes of the enzymes (in all likelihood, their flattening on the Au surface) were suggested to explain the deactivation of MCOs on the bare Au electrodes.

A Nernstian Biosupercapacitor.

Abstract We propose the very first “Nernstian biosupercapacitor”, a biodevice based on only one redox polymer: poly(vinyl imidazole‐co‐allylamine)[Os(bpy)2Cl], and two biocatalysts. At the bioanode PQQ‐dependent glucose dehydrogenase reduces the Os3+ moieties at the polymer to Os2+ shifting the Nernst potential of the Os3+/Os2+ redox couple to negative values. Concomitantly, at the biocathode the reduction of O2 by means of bilirubin oxidase embedded in the same redox polymer leads to the oxidation of Os2+ to Os3+ shifting the Nernst potential to higher values. Despite the use of just one redox polymer an open circuit voltage of more than 0.45 V was obtained during charging and the charge is stored in the redox polymer at both the bioanode and the biocathode. By connecting both electrodes via a predefined resistor a high power density is obtained for a short time exceeding the steady state power of a corresponding biofuel cell by a factor of 8.

The influence of nanoparticles on enzymatic bioelectrocatalysis

In nearly all papers concerning enzyme–nanoparticle based bioelectronic devices, it is stated that the presence of nanoparticles on electrode surfaces per se enhances bioelectrocatalysis, although the reasons for that enhancement are often unclear. Here, we report detailed experimental evidence that neither an overpotential of bioelectrocatalysis, nor direct electron transfer and bioelectrocatalytic reaction rates for an adsorbed enzyme depend on the size of nanoparticles within the range of 20–80 nm, i.e. for nanoparticles that are considerably larger than the enzyme molecules.

Powering electronic contact lenses : current achievements, challenges, and perspectives

The recent media hoopla regarding ‘smart’, ‘bionic’, or more appropriately, electronically augmented contact lenses is analyzed in terms of real achievements coupled to the critically important issue of power management. Not depending on the availability, currently or in the near future, of to-the-purpose discrete or integrated electronic devices, power management, including delivery/supply and temporal sustainability, will be an outstanding issue if present-day technology should remain the only option. Radically different approaches have been taken to deliver electric power to electronically augmented contact lenses, that is, ranging from quite simplistic wire-based delivery assemblies, grossly inappropriate for end users, to various elaborate wireless designs drawing on over-the-air power delivery, as well as solar and electrochemical cells. Nonetheless, given the complex restrictions offered by a contact lens, conventional, even state-of-the-art, power management technology is at an impasse, and to ensure a bright future for smart lenses, radical technological measures need to be taken. Bridging the conceptual gap between fuel cells and supercapacitors, an ingenious novel approach to on-lens power management is presented: a charge-storing fuel cell, or alternatively, a self-charging capacitor, that is, a hybrid electric power device.

Ex vivo electric power generation in human blood using an enzymatic fuel cell in a vein replica

Here we report an enzymatic fuel cell in a vein replica that generates sustained electricity, enough to power an e-ink display, in an authentic human blood stream. We also detail a simple and safe approach for fuel cell evaluation under homeostatic conditions. Our results demonstrate proof-of-principle operation of a biocompatible and safe biodevice that could be implanted in superficial human veins, which we anticipate to be a starting point for more sophisticated investigations of personal sources of electricity.

Scalable, high performance, enzymatic cathodes based on nanoimprint lithography.

Summary Here we detail high performance, enzymatic electrodes for oxygen bio-electroreduction, which can be easily and reproducibly fabricated with industry-scale throughput. Planar and nanostructured electrodes were built on biocompatible, flexible polymer sheets, while nanoimprint lithography was used for electrode nanostructuring. To the best of our knowledge, this is one of the first reports concerning the usage of nanoimprint lithography for amperometric bioelectronic devices. The enzyme (Myrothecium verrucaria bilirubin oxidase) was immobilised on planar (control) and artificially nanostructured, gold electrodes by direct physical adsorption. The detailed electrochemical investigation of bioelectrodes was performed and the following parameters were obtained: open circuit voltage of approximately 0.75 V, and maximum bio-electrocatalytic current densities of 18 µA/cm2 and 58 µA/cm2 in air-saturated buffers versus 48 µA/cm2 and 186 µA/cm2 in oxygen-saturated buffers for planar and nanostructured electrodes, respectively. The half-deactivation times of planar and nanostructured biocathodes were measured to be 2 h and 14 h, respectively. The comparison of standard heterogeneous and bio-electrocatalytic rate constants showed that the improved bio-electrocatalytic performance of the nanostructured biocathodes compared to planar biodevices is due to the increased surface area of the nanostructured electrodes, whereas their improved operational stability is attributed to stabilisation of the enzyme inside nanocavities.

Potentially implantable biocathode with the function of charge accumulation based on nanocomposite of polyaniline/carbon nanotubes

A potentially implantable biocathode with the function of charge accumulation based on a nanobiocomposite including multiwall carbon nanotubes, polyaniline, and bilirubin oxidase is developed. The regularities of the functioning of the obtained electrode are studied in air–saturated phosphate buffer solution, pH 7.4 (PB), and also in phosphate buffer solution containing redox–active blood components (BMB). The open circuit potential of the biocathode is 0.33 and 0.08 V vs. the saturated calomel electrode in PB and BMB, respectively; it is completely restored after at least three self-charge/discharge cycles with connection to resistors with different resistance. Bioelectrocatalytic current density of oxygen reduction is 0.50 and 0.42 mA cm–2 with the residual activity of 78 and 60% of the initial value after 12 h of continuous operation in PB at 25°C and in BMB at 37°C, respectively.

Nanoengineering of Graphene-Supported Functional Composites for Performance-Enhanced Enzymatic Biofuel Cells

Abstract Biofuel cells are a kind of bioenergy devices, which hold wide interests in the areas of bioelectronics, biomedicine, and applied bioelectrochemistry, among others. The development and applications of biofuel cells have encountered some critical challenges mainly arising from their low power capacity and limited cycling stability. To develop new-generation biofuel cells that could offer enhanced performances, for example, through creating biocompatible microenvironments for trapping biomolecules and enhancement of electron-transfer kinetics, intensive efforts have recently devoted to new design, structural engineering, and smart architecture of nanostructured electrode materials. This chapter offers an up-to-date overview of relevant advances in the research and development of enzymatic biofuel cells using graphene-supported functional composites as electrode materials, with the emphasis on the nanoscale engineering of electrode materials for enhancing the overall performance. The chapter focuses on several types of composite material systems, including metallic nanoparticle-decorated graphene materials, polymer-graphene and metal hydroxide-graphene composites. We start with a brief introduction to enzymatic biofuel cells and graphene as a unique two-dimensional material, followed by elucidating the working principles of an enzymatic biofuel cell. We then give some examples about six types of electrode materials that have been tested for enzyme-based biofuel cells and summarize the main immobilization methods of enzymes onto or into graphene-supported materials. We finally discuss remained challenges and ongoing research efforts.