Contents lists available at ScienceDirect Sensors and Actuators B: Chemical journal homepage: www.elsevier.com/locate/snb Prussian Blue based flow-through (bio)sensors in power generation mode: New horizons for electrochemical analyzers Maria A. Komkova ⁎ , Egor A. Andreev, Olga A. Ibragimova, Arkady A. Karyakin Chemistry Faculty of M.V. Lomonosov, Moscow State University, 119991, Moscow, Russia ARTICLE INFO Keywords: Electrochemical biosensors Flow-through analysis Power generation Prussian Blue ABSTRACT We report on advanced Prussian Blue (PB) based flow-through (bio)sensors operated in power generation mode. The performance of such (bio)sensors in wall-jet cell is significantly improved with respect to three-electrode regime in terms of up to 1.5 times higher sensitivity probably due to the enhanced mass transport compared to it in batch cell upon stirring. Most importantly, potentiostat-free operation upon short-circuiting PB modified electrode with Ag|AgCl reference through an ammeter drastically decreases noises, which results in up to 3 times increased signal-to-noise ratio compared to conventional three-electrode flow-through systems. These findings, as well as the simplicity of the proposed approach, are encouraging for the high throughput robust sensing and open new horizons for elaboration of electrochemical analyzers. 1. Introduction Expected to provide both miniaturization and simplification of the readout in comparison with conventional electroanalytical devices powered by the potentiostat, the so-called ‘self-powered’ electro- chemical (bio)sensors are becoming increasingly popular [1,2]. Nevertheless, despite of their attractive title, which was coined for a biofuel cell generating power proportional to the concentration of analyte consumed as the fuel [3], such sensors are hardly applicable. First, they are able to generate power sufficient for low-power elec- tronics only at high analyte concentrations [4–6] and, thus, still require external power supply. Second, in order to gain ultimate power output, the electrodes with large potential difference are commonly used [7,8]. Considering amperometric sensors, we note that short-circuiting the electrodes with large potential difference shifts working electrode po- tential from the optimal one, which deteriorates analytical performance of the corresponding sensor. Therefore, the only feasible approach for potentiostat-free operation is power generation upon short-circuiting the electrodes with the smallest potential difference. Short-circuiting equilibrates electrode potentials. The reference electrode is character- ized by high exchange current density and stable potential by defini- tion. Obviously, upon short-circuiting the working electrode potential would be maintained close to the Ag|AgCl open circuit potential. Ac- cordingly, the amperometric sensors operated around 0.00 V versus Ag|AgCl reference are the most promising candidates for such a setup, since the shortcut would adjust optimal working electrode potential without potentiostat [9]. Among the low-potential electrochemical transducers, Prussian Blue (or ferric hexacyanoferrate) is the most efficient one due to its unique catalytic properties. Compared to the widely used platinum electrodes, in neutral media Prussian Blue based electrocatalyst provides 1000 times higher electrochemical rate constant [10], which results in ex- ceptionally high sensitivity of the corresponding (bio)sensors, and three orders of magnitude higher selectivity in hydrogen peroxide reduction relative to oxygen reduction [11]. These out-and-outer properties of ferric hexacyanoferrate even denoted as an ‘artificial peroxidase’ (in- cluding exceptional electrocatalytic activity among transition metal hexacyanoferrates [12]) determine advantageous analytical perfor- mance of Prussian Blue based (bio)sensors [13–16]. Earlier we reported on advanced Prussian Blue based (bio)sensors operated through power generation upon short-circuiting the working electrode and the Ag|AgCl reference through an ammeter [9]. Never- theless, the applicability of such approach for the flow-injection ana- lysis was still questionable. Seemingly low rate of signal generation at micromolar analyte concentrations could either decrease the sensitivity or extend the response time of the corresponding flow-through (bio) sensors, which would probably be a significant drawback. Accordingly, the primary objective of the present study was a cri- tical evaluation of Prussian Blue based (bio)sensors in flow injection regime operated in power generation mode upon short-circuiting the working and the silver chloride reference electrode. The research de- tailed herein clearly shows that enhanced mass transport in wall-jet cell https://doi.org/10.1016/j.snb.2019.04.134 Received 14 December 2018; Received in revised form 21 April 2019; Accepted 26 April 2019 ⁎ Corresponding author at: Leninskie gory 1, build. 3, 119991, Moscow, Russia. E-mail address: mkomkova@gmail.com (M.A. Komkova). Sensors & Actuators: B. Chemical 292 (2019) 284–288 Available online 28 April 2019 0925-4005/ © 2019 Elsevier B.V. All rights reserved. T