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Sensors ◽  
2022 ◽  
Vol 22 (2) ◽  
pp. 558
Author(s):  
Erican Santiago ◽  
Shailu Shree Poudyal ◽  
Sung Y. Shin ◽  
Hyeun Joong Yoon

A graphene oxide (GO)-based cortisol biosensor was developed to accurately detect cortisol concentrations from sweat samples at point-of-care (POC) sites. A reference electrode, counter electrode, and working electrode make up the biosensor, and the working electrode was functionalized using multiple layers consisting of GO and antibodies, including Protein A, IgG, and anti-Cab. Sweat samples contact the anti-Cab antibodies to transport electrons to the electrode, resulting in an electrochemical current response. The sensor was tested at each additional functionalization layer and at cortisol concentrations between 0.1 and 150 ng/mL to determine how the current response differed. A potentiostat galvanostat device was used to measure and quantify the electrochemical response in the GO-based biosensor. In both tests, the electrochemical responses were reduced in magnitude with the addition of antibody layers and with increased cortisol concentrations. The proposed cortisol biosensor has increased accuracy with each additional functionalization layer, and the proposed device has the capability to accurately measure cortisol concentrations for diagnostic purposes.


2021 ◽  
Author(s):  
Gopal Krishna Gupta ◽  
Arpita Diwedi ◽  
Anu Sharma ◽  
Kaushik Shandilya

Abstract In the present article, highly capacitive NiMn-LDHs/GO composite of electrode material has been the synthesized for supercapacitor energy storage. Various analytical techniques (particularly X-ray diffraction (XRD), Raman spectroscopy, high resolution transmission electron microscopy (HRTEM), and scanning electron microscope (SEM)) have been employed to characterize the as-synthesized NiMn-LDHs/GO. The Microscopic images obtained using HRTEM analysis clearly reveal the formation of lattice fringe pattern (lattice spacing as ~ 0.22 nm) for GO, whereas SEM images shows highly porous nature. The super-capacitive performance of the as-synthesized electrode material have been accessed through an electrochemical work station comprising of a 3-electrode system. The working electrode made up of NiMn-LDHs/GO (Active material) on Ni foil (working electrode) with the help of PVDF (binder), has shown specific capacitance of 1964 F g−1 at current density of 1 A g−1 with Galvanostatic charging/discharging (GCD) technique. It has also shown remarkable cyclic stability with a capacitance retention of 98% after 2000 cycles. The high-power density (401 W/kg) and energy density (17.78 Wh/kg) signify the high-level electrochemical supercapacitor behaviour in charge storage applications.


Biosensors ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 459
Author(s):  
Neda Rafat ◽  
Paul Satoh ◽  
Robert Mark Worden

A novel, integrated experimental and modeling framework was applied to an inhibition-based bi-enzyme (IBE) electrochemical biosensor to detect acetylcholinesterase (AChE) inhibitors that may trigger neurological diseases. The biosensor was fabricated by co-immobilizing AChE and tyrosinase (Tyr) on the gold working electrode of a screen-printed electrode (SPE) array. The reaction chemistry included a redox-recycle amplification mechanism to improve the biosensor’s current output and sensitivity. A mechanistic mathematical model of the biosensor was used to simulate key diffusion and reaction steps, including diffusion of AChE’s reactant (phenylacetate) and inhibitor, the reaction kinetics of the two enzymes, and electrochemical reaction kinetics at the SPE’s working electrode. The model was validated by showing that it could reproduce a steady-state biosensor current as a function of the inhibitor (PMSF) concentration and unsteady-state dynamics of the biosensor current following the addition of a reactant (phenylacetate) and inhibitor phenylmethylsulfonylfluoride). The model’s utility for characterizing and optimizing biosensor performance was then demonstrated. It was used to calculate the sensitivity of the biosensor’s current output and the redox-recycle amplification factor as a function of experimental variables. It was used to calculate dimensionless Damkohler numbers and current-control coefficients that indicated the degree to which individual diffusion and reaction steps limited the biosensor’s output current. Finally, the model’s utility in designing IBE biosensors and operating conditions that achieve specific performance criteria was discussed.


2021 ◽  
Vol MA2021-02 (47) ◽  
pp. 1407-1407
Author(s):  
Vikram Singh ◽  
Rafiqul Islam ◽  
Melak Yossief ◽  
Sabine Kuss

2021 ◽  
Vol 3 (10) ◽  
Author(s):  
Wasihun Abebe Hika ◽  
Abebe Reda Woldu

AbstractElectrochemical carbon dioxide reduction reaction (CO2RR) has been investigated for decades. CO2RR to value-added products is an indispensable option to address climate change and energy storage needs. We believed that CO2RR performance can be influenced by the anode materials employed for the oxidation half-reaction. Although H2O oxidation near-neutral solution does not being received greater attention, there is also an idea that it plays an important role not only in completing CO2 reduction cycle, but also to significantly influence the cathode during reduction. Therefore, the present study aimed to investigate the impact of three different anode materials (platinum, glassy carbon, and hematite) on the activity and selectivity of the gold cathode in an electrochemical CO2 reduction reaction. Linear sweep voltammetry and electrochemical impedance spectroscopy have been used to study electrocatalytic properties. In the meantime, x-ray diffraction is used to investigate the crystal planes of the as-prepared electrodes, while the work function and morphology of Au films were measured by atomic force microscope. Similar activity and selectivity to CO formation were observed when platinum and hematite were used as counter electrodes, while the least CO formation was recorded on the glassy carbon counter electrode. Graphic abstract The protons (H+) obtained from the oxidation of H2O onto these three different anodic materials (platinum, glassy carbon, hematite) are moving faster through the bulk of the solution to the working electrode. Consequently, the reaction occurred on the working electrode can be influenced by the number of protons coming from the anode.


2021 ◽  
Author(s):  
Uday Dadwal ◽  
Rajendra Singh

Photoelectrochemical (PEC) splitting of natural water was studied using silicon nanowires decorated with silver dendrites (dendritic nanostructures) as working electrode. A metal assisted wet chemical etching method has been used for the synthesis of dendritic heteronanostructures. Measured photocurrent density 1.7 mA/cm2 under white light illumination exhibits the efficient decomposition of natural water. The decomposition of water is primarily ascribed to the enhancement in the working electrode surface and water effective interface and the decrease in the recombination of light induced (photoexcited) carriers in the existence of silver dendritic nanostructures. Enhancement in photoinduced charge carriers separation caused due to the existence of Schottky barrier between the silicon and silver dendritic nanostructures. The light induced carriers (holes) in silicon are transferred to the metal (Ag) dendritic nanostructures that work as a charge basin to effectively carry out the oxidation reaction of water during PEC measurement. The solar-to-hydrogen (STH) conversion efficiency of about 4.5% was reported, indicating the efficient PEC solar water (pH 7) splitting. A cost-effective and efficient method for the PEC solar water splitting is presented in order to enhance the STH efficiency for the production of clean and renewable fuel.


2021 ◽  
Author(s):  
Zambaga Otgonbayar ◽  
Won Chun Oh

Abstract For reduction of CO2 into hydrocarbon fuels, a quaternary AgFeNi2S4 semiconductor combined in Graphene-TiO2 nanocomposite material was synthesized via the Pechini method. The catalytic activity of the photocatalyst for photocatalytic and electrochemical CO2 evolution into hydrocarbon fuels was tested. The methanol yield under UV light was 8.679, 6.349, and 4.136 %, and the methanol yields under visible light were 6.291, 4.738, and 2.339 %, respectively. The stability and reusability of the photocatalyst remained high after a 4-cycle recycling test without a decrease in yield of the final photocatalytic CO2 reduction product. The enhanced photoreduction of CO2 through the as-prepared ternary photocatalyst can be ascribed to the catalyst's conformation and low recombination rate. In electrochemical CO2 reduction, the Faraday efficiency is the main parameter that defines the performance of the working electrode and the evolution of methanol. The Faraday efficiency of AFNSGT ternary nanocomposite was 44.25 %; this is an increase in the value of the Faraday efficiency, which proves that the design of the new nanocomposite successfully increases the activity of the working electrode and has a positive effect on the electrochemical reduction of CO2. The photocatalytic and electrochemical CO2 reduction data show that the preparation method, morphological state, and charge carrier properties of the photocatalyst are important for the catalytic activity and efficiency of the methanol evolution pathway.


KOVALEN ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 109-120
Author(s):  
Rahmiani Gani ◽  
Syarifah Rabiatul Adawiah ◽  
Arfiani Nur

Hydrogen production by water electrolysis can be optimalized by improve the working electrode. Stainless steel as working electrode was coated with graphene and polyaniline by using cyclic voltammetry method with Ag/AgCl as reference electrode and Pt as counter electrode. Coated electrodes were characterized by SEM-EDS and cyclic voltammetry method. Furthermore, the synthesized electrode was applied for water electrolysis by adding 1- 5 g/L NaHCO3. The characterization data showed that Stainless steel/Graphene-Polyaniline electrode can be synthesized by using cyclic voltammetry. The coating process was conducted at sweeping rate 10 mV/s on voltage -0.2 to 0.8 V for 10 cycles. The voltammograms showed that the highest cathodic peak current of electrolysis obtained at 0.491 mA by addition 2 g NaHCO3 on SS/G-PANi0,5 electrode, and the highest anodic peak current obtained at 0.191 mA by addition 2 g NaHCO3 on SS/G-PANi0,5 electrode. Based on the overpotential data, the smallest average potential difference of H+ adsorption obtained by SS/G-PANi1,0 electrode, and the smallest average potential difference of H+ desorption obtained by SS/G-PANi0,5 electrode. Keywords: Stainless steel, hydrogen production, electroplating, electrocatalyst, electrolysis


Author(s):  
Georgyi S. Vasiliev ◽  
Dmytro Yu. Ushchapovskyi ◽  
Victoria I. Vorobyova ◽  
Olga V. Linyucheva

Background. New 3D-printing technologies are becoming more and more advanced and widespread in the twenty-first century. One of the types of 3D-printing is electrochemical 3D-printing, in which electrochemical deposition of metals is used to form metal products. Potentially, this method of 3D-printing is the most energy efficient, the least material-intensive, and also the easiest to implement. There- fore, research aimed at creating and improving systems for electrochemical 3D-printing is promising. Objective. The aim of the paper is to study the influence of geometric parameters of the system and the composition of the elec trolyte on the current distribution on the surface of the working electrode (cathode) in the process of electrochemical 3D-printing, and therefore print accuracy. Methods. Volt-amperometric measurements and multi-physical computer modelling of the secondary distribution of current density using COMSOL MULTYPHYSICS for different geometric parameters of the working part of the 3D-printer and different composition of electrolytes. Results. Based on the simulation of the secondary distribution of current density in copper sulphate electrolyte, it was found that the content of sulfuric acid in the solution should be minimal in order to purposefully deposit metal in the area directly under the working electrode. Based on the condition of maximum energy efficiency and accuracy of electrochemical 3D-printing, the optimal ratio between the deposition surface (cathode) and the edge of the non-conductive body of working electrode was found. Conclusions. It was established that in order to narrow the zone of current scattering (increase the accuracy of electrochemical 3D-printing) it is necessary to ensure the optimal ratio between the diameter of the capillary and the edge of the non-conductive body of the counter electrode. It was shown that this ratio should not be less than 5 [mm / mm]. Further applied research will be aimed at adaptation and practical implementation of the obtained model data, optimization of the electrolyte composition and design of the 3D-printer.


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