Electrode Matrix Research Articles

Ultrasensitive electrochemical biosensor for des-gamma-carboxy prothrombin analysis based on core-shell Pd@PtCu-alloy loaded on WS2 nanosheet

Abstract Herein, a sandwich-type electrochemical biosensor was developed for determination of des-gamma-carboxy prothrombin (DCP). Core-shell Pd@PtCu loaded on WS2 nanosheet (Pd@PtCu-WS2) nanocomposite was lightly synthesized, which possessed large surface area and remarkable peroxidase-like activity, and thus acted as nanocarrier and signal nanoprobe. Secondary DCP antibodies (Ab2) were then tethered on the surface of the nanocomposite, forming the superior label to product and amplify electrochemical signal. Additionally, gold nanoparticles-functionalized multi-wall carbon nanotubes (AuNPs@MWCNTs) was employed as the electrode matrix, which could accelerate electron transfer and improve the immobilization of primary DCP antibodies (Ab1). After the typical sandwich-type recognition, an obvious current response was generated through the reduction of hydrogen peroxide (H2O2). With this strategy, the biosensor revealed ultra-sensitivity ranging from 100 fg mL−1 to 100 ng mL−1 with a low limit of detection of 71.6 fg mL−1. What’s more, it was demonstrated to successfully analyze DCP in clinical serum sample. Therefore, the biosensor provided an alternative tool for clinical biomarker analyses.

Human Body Parts Proximity Measurement Using Distributed Tactile Robotic Skin.

Safety in human–machine cooperation is the current challenge in robotics. Safe human–robot interaction requires the development of sensors that detect human presence in the robot’s workspace. Detection of this presence should occur before the physical collision of the robot with the human. Human to robot proximity detection should be very fast, allowing machine elements deceleration to velocities safe for human–machine collision. The paper presents a new, low-cost design of distributed robotic skin, which allows real-time measurements of the human body parts proximity. The main advantages of the proposed solution are low cost of its implementation based on comb electrodes matrix and real-time operation due to fast and simple electronic design. The main contribution is the new idea of measuring the distance to human body parts by measuring the operating frequency of a rectangular signal generator, which depends on the capacity of the open capacitor. This capacitor is formed between the comb electrodes matrix and a reference plate located next to the matrix. The capacitance of the open capacitor changes if a human body part is in vicinity. The application of the developed device can be very wide. For example, in the field of cooperative robots, it can lead to the improvement of human–machine interfaces and increased safety of human–machine cooperation. The proposed construction can help to meet the increasing requirements for cooperative robots.

Rapid Collection and Aptamer-Based Sensitive Electrochemical Detection of Soybean Rust Fungi Airborne Urediniospores

Plants are the central source of food for humans around the world. Unfortunately, plants can be negatively affected by diverse kinds of diseases that are responsible for major economic losses worldwide. Thus, monitoring plant health and early detection of pathogens are essential to reduce disease spread and facilitate effective management practices. Various detection approaches are currently practiced. These methods mainly include visual inspection and laboratory tests. Nonetheless, these methods are labor-intensive, time-consuming, expensive, and inefficient in the early stages of infection. Thus, it is extremely important to detect diseases at the early stages of the epidemic. Here, we would like to present a fast, sensitive, and reliable electrochemical sensing platform for the detection of airborne soybean rust spores. The suspected airborne soybean rust spores are first collected and trapped inside a carbon 3D electrode matrix by high-capacity air-sampling means. Then, a specific biotinylated aptamer, suitable to target specific sites of soybean rust spores is applied. This aptamer agent binds to the surface of the collected spores on the electrode. Finally, spore-bound aptamer units are incubated with a streptavidin–alkaline phosphatase agent leading to the enzymatic formation of p-nitrophenol, which is characterized by its unique electrochemical properties. Our method allows for the rapid (ca. 2 min), selective, and sensitive collection and detection of soybean rust spores (down to the limit of 100–200 collected spores per cm2 of electrode area). This method could be further optimized for its sensitivity and applied to the future multiplex early detection of various airborne plant diseases.

Manganese dioxide (MnO2)/Fullerene-C60-Modified Electrodes for the Voltammetric Determination of Rifaximin

Rifaximin (RFX) is a broad-spectrum oral antibiotic with bactericidal actions against Gram-negative and Gram-positive bacteria. In the present work, a sensitive voltammetric assay for the RFX in pharmaceutical formulations is designed using nanostructured working electrodes. Surface functionalization with manganese dioxide (MnO2)/fullerene-C60 nanocomposite exhibited the highest electrochemical responses with a sharp oxidation peak at about 336 mV that was obtained using the differential pulse voltammetry (DPV). The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were applied, while the electrode matrix composition including types of nanomaterials, electroanalytical parameters, and pH effect were optimized. To that end, using the DPV, high sensitivity was obtained from the linear calibration curve ranged from 0.8 to 31.5 µg·mL−1 with the correlation coefficient of 0.99, limit of detection of 0.76 µg·mL−1 and limit of quantification of 2.31 µg·mL−1. Accordingly, the designed approach is offering a potential applicability towards the RFX determination in pharmaceutical preparations and its quality control.

Determining nadifloxacin in pharmaceutical formulations using novel differential pulse voltammetric approach

The present study suggested a novel analysis protocol for sensitive differential pulse voltammetric determination of nadifloxacin (NF). The performance of the working carbon paste electrodes (CPE) were improved via incorporation of different carbonaceous nanomaterials such graphene nano sheets (rG), fullerene-C60, multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs). Through assay optimization, comprehensive and deep parallel studies were conducted concerning the electrode matrix composition, mode of electrode modification, electroanalytical parameters and pH effects. Anodic oxidation peak were recorded at 1.02 V at pH 4 with an irreversible diffusion-controlled process. To that end, using the differential pulse voltammetry, high sensitivity was achieved in the NF concentration ranged from 3.3 to 53.3 μmol and limit of detection reached 0.250 μmol with improved stability and reproducibility. Moreover, the electrode reaction mechanism was studied electrometrically and sustained with the molecular orbital calculations. The interferences issues were also taken into consideration. Accordingly, the designed approach offers potential applicability towards nadifloxacin determination in pharmaceutical preparations with acceptable recoveries compared with the reported methods.

How to Improve the Performance of Electrochemical Sensors via Minimization of Electrode Passivation

It follows from critical evaluation of possibilities and limitations of modern voltammetric/amperometric methods that one of the biggest obstacles in their practical applications in real sample analysis is connected with electrode passivation/fouling by electrode reaction products and/or matrix components. This review summarizes possibilities how to minimise these problems in the field of detection of small organic molecules and critically compares their potential and acceptability in practical laboratories. Attention is focused on simple and fast electrode surface renewal, the use of disposable electrodes just for one and/or few measurements, surface modification minimising electrode fouling, measuring in flowing systems, application of rotating disc electrode, the use of novel separation methods preventing access of passivating particles to electrode surface and the novel electrode materials more resistant toward passivation. An attempt is made to predict further development in this field and to stress the need for more systematic and less random research resulting in new measuring protocols less amenable to complications connected with electrode passivation.

Analysis of phase waves in the ECoG data

Subdural ECoG data recorded from the matrix of electrodes during syllable pronunciation are analyzed by the method of circular-linear regression. Phase waves in 1D electrode arrays and in the whole 2D set of electrodes are detected, and their spatial organization and temporal evolution are studied. Phase portraits of wave vectors indicate the presence of sources, sinks, and saddle points. The analysis of temporal evolution of phase portraits shows that they changed more at the beginning of syllable pronunciation. Furthermore, wave sources were more stable in their localization during the pronunciation. Overall, in spite of large variability of phase portraits, they represent some characterization of the dynamics of electric potential in the cerebral cortex.

Research into storage processes in batteries to create highly efficient reversible hydrogen storage

This paper has experimentally proved that hydrogen accumulates in large quantities in metal ceramic electrodes of alkaline accumulators during their operation. It has been found that hydrogen is not present in the metal ceramic electrodes of alkaline accumulators not yet in operation. It is shown that in alkaline accumulators with a service life of more than five years, the largest amount of hydrogen is present in their electrodes. Hydrogen is found to accumulate in oxide-nickel electrodes of alkaline accumulators, which have hydrogen absorption capacity of 13.4 wt%. Sintered nickel matrix of oxide-nickel electrode of alkaline accumulator was considered. The values of hydrogen absorption in this matrix are 20.2 wt%, the stored energy density is 44.018 kJ/g. The results obtained in the operation are three times higher than the previously obtained data, which are based on the use of traditional methods for reversible metal hydrides, such as magnesium hydride and complex hydrides. In addition, the results obtained exceed the values announced in the criteria for hydrogen storage systems developed by the US Department of Energy.

Conducting Polymer Composites As Multifunctional Electrode Matrices for Lithium-Ion Batteries

The rising number of lithium-ion battery cells fabricated to power electric vehicles has raised concerns about the environmental impacts of battery electrode fabrication process. Typically, N-Methyl-2-pyrrolidone (NMP) solvent is used to blend active materials and electrode matrices, which are normally polyvinylidene fluoride/carbon-black (PVDF/C) mixtures. The use of NMP solvent, however, requires extensive energy for electrode drying and toxic solvent recovery. In addition, the PVDF/C electrode matrix offers weak interactions with active materials, which results in poor morphological integrity and rapid capacity fading, especially for high-volume-change electrode materials. Using water-processable binders such as carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) has been proven to enable a greener electrode-casting process as well as improve electrode performance. However, the electrical conductivity of these electrodes relies mainly on carbon additives, which are subjected to agglomeration and volumetric-capacity reduction. In this study, new electrode matrices are developed from in situ polymerized polypyrrole:carboxymethyl-cellulose (PPy:CMC) composites with water-processable and electrical-conductive features. By forming a composite structure in which CMC acts as an anionic dopant for PPy conducting polymer, the PPy:CMC composites show good electrical conductivity, allowing them to be used as mono-component electrode matrices. As a result, carbon-additive-free LiCoO2/PPy:CMC electrodes can cycle at different C-rate. More importantly, the PPy:CMC composites enable aqueous slurry electrode casting, addressing the environmental pollution associated with NMP solvent utilization. The study introduces another potential application of conducting polymer composites in Li-ion batteries.Keywords: aqueous electrode casting, conducting polymers, polypyrrole.

(Invited) Microporous Activated Carbon and S Composite Cathode for Rechargeable Li-S Battery

Sulfur (S) has an outstanding theoretical capacity (1,672 mAh g-1) and is abundant material. There are several problems limiting a realistic S positive electrode. A major issue is unstable properties of lithium polysulfide (Li2Sn) intermediates formed during charge and discharge processes; they dissolve easily into various electrolytes [1-3]. When dissolution of Li2Sn occurs, this leads to a rapid capacity decay by a redox shuttle reaction and to irreversible degradation of the overall Li-S system. To solve these problems S-composites for stabilization of S derivatives has been proposed. In previous work, S-composites with mesoporous activated carbon and conductive polymers with S and S-graphene have been extensively studied, and these systems show relatively high cycle stability. However, these electrodes still have a problem of insufficient charge-discharge efficiency. This is due to the redox shuttle of dissolving Li2Sn intermediates, and there is few practical methods that completely prevent the dissolution of Li2Snintermediates with these electrodes. Therefore, in recent years, other studies have been conducted to completely prevent the dissolution of Li2Sn by using new host materials for S and novel cell design. They are composites of S with microporous activated carbon or organic substances and all-solid Li-S batteries [1-5]. These technologies can completely suppress the dissolution of a Li2S intermediate, so that it is known that not only their capacity retention but also their charge-discharge efficiency is stabilized[6]. However, these electrodes have a problem in energy density because their micropore volume is still low, which is derived from low S loading.We synthesized S-composites based on microporous alkali-activated carbon with high porous volume and tested positive electrode performance of the S-composites. As a result, we achieved both improvement of cycling characteristics by preventing Li2Sn dissolution and an increase in S loading amount[7]. To increase S loading into microporous carbon as well as limit dissolution of Li2S4-8 we designed micropore-rich activated carbon with high surface area and pore volume, which was obtained by activation of azulmic carbon (AZC) precursor as a nitrogen (N)-doped carbon[8]. The AZC was a carbonized product from azulmic acid (AZA) that was obtained by polymerization of hydrocyanic acid (H−C≡N) under a high temperature. We would suggest that our activated AZC is promising material as positive S electrode matrix for the next-generation rechargeable Li batteries.Moreover, we increased S loading into micropores by preparing activated carbon with alkali activation from a N-doped carbon AZC-800 (carbonized at 800ºC) to enhance energy density of Li-S batteries. It was found that micropores are selectively formed by removing nitrogen from AZC-800 with alkali activation; hence AZC-800/1KOH and AZC-800/2KOH (the numerical before KOH is a KOH/AZC weight ratio) have high surface area. As a result, S can be loaded up to 55 and 62 wt.% in the respective activated carbon electrodes: AZC-800/1KOH@S55 and AZC-800/2KOH@S62. AZC-800/1KOH@S55 can cycle well in not only a glyme-based electrolyte, LiTFSI/G4/HFE but also 1M LiPF6 EC/DMC. AZC-800/2KOH@S62 can function in LiTFSI/G4/HFE but is incompatible with the EC/DMC-based electrolyte. We consider that these different characteristics are ascribed to a fine pore structure. The present microporous activated AZC with high S loading is promising positive electrode material for rechargeable Li-S batteries. Lately we have developed another activator instead of KOH. We have applied AZC-based materials also to a massive cathode based on Al-mesh-type current collector to increase a cell energy density.This work was partly supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING)” from Japan Science and Technology Agency (JST); Grant#: JPMJAL1301.References S. Zheng, P. Han, Z. Han, H. Zhang, Z. Tang, and J. Yang, Scientific Reports, 4, 4842 (2014). Z. Li, L. Yuan, Z. Yi, Y. Sun, Y. Liu, Y. J. iang, Y. Shen, Y. Xin, Z. Zhang, and Y. Huang, Adv. Energy Mater., 4, 1301473 (2014). B. Zhang, X. Qin, G. R. Li, and X. P. Gao, Energy Environ. Sci., 3, 1531 (2010). L. Wang, X. He, J. Li, M. Chen, J. Gao, and C. Jiang, Elctrochim. Acta, 72, 114 (2012). T. Kobayashi, Y. Imade, D. Shishihara, K. Homma, M. Nagao, R. Watanabe, T. Yokoi, A. Yamada, R. Kanno,, and T. Tatsumi, J. Power Sources, 182, 621 (2008). T. Takahashi. M. Yamagata, and M. Ishikawa, Prog. Nat. Sci., 25, 612 (2015). S. Okabe, S. Uchida, Y. Matsui, M. Yamagata, and M. Ishikawa, Electrochemistry, 85, 671 (2017). S. Usuki, S. Uchida, Y. Matsui, M. Yamagata, H. Hinago, and M. Ishikawa, Electrochemistry, 85, 650 (2017).

An electrochemical sensor for simultaneous determination of some pharmaceutical compounds using ionic liquid and Pd nanoparticles supported on porous silicon doped carbon-ceramic electrode as a renewable surface composite electrode

A novel approach was presented to synthesize Pd nanoparticles supported on the surface of porous silicon (PSi) powder by a simple in-situ redox reaction between Pd+2 and PSi in hydrofluoric acid solution. Ionic liquid and Pd/PSi nanocomposite doped carbon-ceramic electrode was prepared by mixing them with electrode matrix before gelation. Pd/PSi nanocomposite in carbon-ceramic ionic liquid electrode (CCILE) was utilized as a novel electrocatalyst and exhibited a synergetic impact on the oxidation of codeine (COD) and acetaminophen (ACT). The chemical, electrochemical, and morphological, features of the provided nanostructure were characterized by means of X-ray diffraction spectroscopy, energy dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FT-IR), as well as cyclic voltammetry (CV). The peak currents of oxidation were raised, and the oxidation peak potentials of ACT and COD were declined on the proposed sensor surface by the high electrochemical activity, high surface area, fast electron transfer rate, as well as proper antifouling features of this nanostructure. ACT and COD were determined simultaneously via differential pulse voltammetry (DPV). Using the proposed electrochemical sensor, ACT and COD could be measured in the range of 0.3–15 µmol L−1 with detection limits of 24 nM and 32 nM, respectively. As a final point, the provided electrochemical sensor was utilized to determine ACT and COD in the real samples, including pharmaceutical compounds and blood serum with satisfactory results.

Separation and recovery of ammonium from industrial wastewater containing methanol using copper hexacyanoferrate (CuHCF) electrodes

Ammonium is typically removed from wastewater by converting it to nitrogen gas using microorganisms, precluding its recovery. Copper hexacyanoferrate (CuHCF) is known to reversibly intercalate alkali cations in aqueous electrolytes due to the Prussian Blue crystal structure. We used this property to create a carbon-based intercalation electrode within an electrochemical cell. Depending on the electrode potential, it can recover NH4+ from wastewater via insertion/regeneration while leaving organics. In the first phase, different binders were evaluated towards creating a stable electrode matrix, with sodium carboxymethyl cellulose giving the best performance. Subsequently, based on voltammetry, we determined an intercalation potential for NH4+ removal of + 0.3 V vs. Ag/AgCl, while the regeneration potential of the electrode was + 1.1 V (vs. Ag/AgCl). Using the CuHCF electrodes 95% of the NH4+ in a synthetic wastewater containing 56 mM NH4+ and 68 mM methanol was removed with an energy input of 0.34 ± 0.01 Wh g−1 NH4+. A similar removal of 93% was obtained using an actual industrial wastewater (56 mM NH4+, 68 mM methanol, 0.02 mM NO2−, 0.05 mM NO3−, 0.04 mM SO42− and 0.34 mM ethanol), with an energy input of 0.40 ± 0.01 Wh g−1 NH4+. In both cases, there was negligible removal of organics. The stability of CuHCF electrodes was evaluated either by open circuit potential monitoring (61 h) or by cyclic voltammetry (50 h, 116 cycles). The stability during cycling of the electrode was determined in both synthetic and real streams for 25 h (125 cycles). The charge density (C cm−1) of the CuHCF electrodes declined by 17 % and 19% after 125 cycles in the synthetic stream and the actual wastewater, respectively. This study highlights the possibility of low-cost CuHCF coated electrodes for achieving separation of NH4+ from streams containing methanol. The stability of electrodes has been improved but needs to be further enhanced for large-scale applications and long-term operation.

Preparation of graphene oxide/poly(o-phenylenediamine) hybrid composite via facile in situ assembly and post-polymerization technology for the anode material of lithium ion battery

Electrode material is a key factor for high-energy storage battery. In this paper, graphene oxide/poly(o-phenylenediamine) (GO/PoPD) hybrid composite is prepared by combining the self-assembly process to form graphene oxide/o-phenylenediamine hydrogel and subsequently the in situ oxidation polymerization, which exhibits the open porous morphology with high BET surface area of 347 m2/g. As the anode of lithium ion battery, GO/PoPD possesses the double lithium storage mechanisms from graphene oxide and poly(o-phenylenediamine). Meanwhile, it exhibits an initial discharge-specific capacity of 1632.4 mAh/g and the improved cycling stability. Even after 43 cycles, it still keeps a capacity of 839.5 mAh/g, which is obviously higher than that of GO and PoPD. Furthermore, GO/PoPD hybrid composite presents the enhanced rate performances with the discharge-specific capacities of 1411.7, 718.2, 621.2, and 576.3 mAh/g at current rates of 50, 100, 200, and 500 mA/g, respectively. The improved electrochemical performances are attributed to the formed stable porous morphology, which facilitates the electrolyte ion to penetrate into the electrode matrix during the redox reaction and then results in the improved cell performances.

Conducting polymer composites as water-dispersible electrode matrices for Li-Ion batteries: Synthesis and characterization

As battery materials increase in energy density, the likelihood of larger morphological changes during cycling increases. Current PVDF/carbon electrode matrices are ill-prepared for such materials and new battery electrode matrices are required. Typical strategies replace PVDF by aqueous binders, utilize other carbonaceous conductive additives or add small amounts of conducting polymers. In this study, we propose a class of water-processable, self-conductive electrode matrices that relies on the combination of polyelectrolyte binders with conducting polymers. By in situ polymerizing conducting polymer monomers in an aqueous solution of carboxylate-containing polymers, new electrode matrices are synthesized, in which components are intimately mixed at the nano-scale. Herein, the molecular composite polypyrrole:carboxymethyl cellulose (PPy:CMC), as a representative electrode matrix, allows the water-based electrode fabrication of carbon-additive-free electrodes. No additional binders and conductive additives are required to fabricate electrodes due to the adhesive and conductive features of PPy:CMC composites. This study paves the way for developing a promising type of electrode matrices for Li-ion batteries based on conducting polymer molecular composites that are adhesive and conductive, ensuring high-energy-density battery materials maintain active over more cycles. • Water-dispersible, self-conductive binder from low-cost, high-volume raw materials. • Simple synthesis and purification yields nano-composite of polypyrrole and carboxymethyl cellulose. • Binder is compatible with industry-typical slurry casting (tape casting). • Carbon additive-free lithium intercalation cathode operates at 1C.

Influence functions for a hysteretic deformable mirror with a high-density 2D array of actuators.

We present modeling and analysis of a hysteretic deformable mirror where the facesheet interacts with a continuous layer of piezoelectric material that can be actuated distributively by a matrix of electrodes through multiplexing. Moreover, a method to calculate the actuator influence functions is described considering the particular arrangement of electrodes. The results are presented in a semi-analytical model to describe the facesheet's deformation caused by a high-density array of actuators, and validated in a simulation. The proposed modeling of an interconnection layout of electrodes is used to determine the optimal pressures the actuators must exert to achieve a desired surface deformation.

Highly Elastic Block Copolymer Binders for Silicon Anodes in Lithium-Ion Batteries.

Silicon (Si) is a promising anode material to replace the broadly adopted graphite due to its high capacity and abundant source. However, Si anodes suffer from severe problems of huge volume change (∼300%), and the commonly used binders like poly(vinylidene fluoride) (PVDF) cannot accommodate such changes. Here, we report a tough block copolymer PVDF-b-Teflon (PTFE) binder that can coalesce pulverized Si and thus enhance the stability of Si anodes. The suspension copolymerization of vinylidene fluoride and tetrafluoroethylene produces elastic PVDF-b-PTFE with large breaking elongations of >250% and high viscosity as well as high ionic conductivity and thermal stability. We show that 5 wt % of the binder forms elastic cobweb structures in the electrode matrix that can effectively coalesce Si particles and conductive agents together, enabling long cycling stability (>250 cycles) and high rate performance (1 C) for electrodes at a commercial-level Si loading of 1 mg·cm-2. The findings point out to a promising strategy for developing highly elastic and tenacious binders for electrodes with large volume changes during the electrochemical reactions.

3D porous carbon nanofibers with CeO2-decorated as cathode matrix for high performance lithium-sulfur batteries

The reasonable design of the cathode host material is of great significance for achieving high-efficiency sulfur electrochemistry and increasing the energy density of lithium-sulfur (Li-S) batteries. Herein, a uniformly CeO2 doped three-dimensional porous nitrogen-rich carbon nanofiber (CeO2@CNF) is prepared as an advanced sulfur electrode matrix. Carbon nanofibers with good electrical conductivity and abundant pores can effectively store sulfur and inhibit the shuttle of polysulfides by double physicochemical sulfur coordination. In addition, electrocatalytically active CeO2 nanocrystals significantly promote stable redox activity. The prepared sulfur electrode achieves a high area capacity of 8.4 mAh cm−2, a high rate capacity of up to 2 C and an excellent cycle capacity of over 400 cycles.

On the DC Offset Current Generated during Biphasic Stimulation: Experimental Study

This paper deals with the DC offset currents generated by a platinum electrode matrix during biphasic stimulation. A fully automated test bench evaluates the nanoampere range DC offset currents in a realistic and comprehensive scenario by using platinum electrodes in a saline solution as a load for the stimulator. Measurements are performed on different stimulation patterns for single or dual hexagonal stimulation sites operating simultaneously and alternately. The effectiveness of the return electrode presence in reducing the DC offset current is considered. Experimental results show how for a defined nominal injected charge, the generated DC offset currents differ depending on the stimulation patterns, frequency, current amplitude, and pulse width of a biphasic signal.

MnO/few-layered-graphene composite as a high performance electrode material in aqueous supercapacitors

MnO nanonetwork decorated few layered graphene (FLG) composite was prepared using a completely solid state process and when tested as an electrode material in an aqueous supercapacitor it delivered an excellent specific capacitance (SC) of 778.5 F/g at a current density of 0.5 A/g and retained 93% of the SC even after 1000 charge-discharge cycles. Cyclic Voltammetry (CV) studies showed that the SC of the composite is the resultant of the combined electric double layer capacitance of FLG and pseudo-capacitance of MnO. The negligible change in the nature of CV curves recorded at different scan rates showed that the composite is electrochemically stable. Also, the high discharge capacitance is explained in terms of composite’s porosity, which shortens the cation path into the electrode matrix.

A new nickel-based co-crystal complex electrocatalyst amplified by NiO dope Pt nanostructure hybrid; a highly sensitive approach for determination of cysteamine in the presence of serotonin

A highly sensitive electrocatalytic sensor was designed and fabricated by the incorporation of NiO dope Pt nanostructure hybrid (NiO–Pt–H) as conductive mediator, bis (1,10 phenanthroline) (1,10-phenanthroline-5,6-dione) nickel(II) hexafluorophosphate (B,1,10,P,1,10, PDNiPF6), and electrocatalyst into carbon paste electrode (CPE) matrix for the determination of cysteamine. The NiO–Pt–H was synthesized by one-pot synthesis strategy and characterized by XRD, elemental mapping analysis (MAP), and FESEM methods. The characterization data, which confirmed good purity and spherical shape with a diameter of ⁓ 30.64 nm for the synthesized NiO–Pt–H. NiO–Pt–H/B,1,10, P,1,10, PDNiPF6/CPE, showed an excellent catalytic activity and was used as a powerful tool for the determination of cysteamine in the presence of serotonin. The NiO–Pt–H/B,1,10, P,1,10, PDNiPF6/CPE was able to solve the overlap problem of the two drug signals and was used for the determination of cysteamine and serotonin in concentration ranges of 0.003–200 µM and 0.5–260 µM with detection limits of 0.5 nM and 0.1 µM, using square wave voltammetric method, respectively. The NiO–Pt–H/B,1,10,P,1,10,PDNiPF6/CPE showed a high-performance ability for the determination of cysteamine and serotonin in the drug and pharmaceutical serum samples with the recovery data of 98.1–103.06%.