The goal of this study was to develop an electroanalytical method for the simultaneous determination of steroid hormones for the first time. The key factor in the electrochemical methods is the ...choice of suitable electrode materials. For this purpose, graphene quantum dots (GQDs) doped poly(sulfosalicylic acid) (PSSA) was immobilized on a glassy carbon electrode (GCE). Apart from exhibition strong and stable electrocatalytic response towards estradiol (E2) and progesterone (P4), the proposed sensor was able to distinguish two hormone's oxidation peaks clearly. Under the optimal conditions, for selective determination of E2, good linear relationships were obtained in the range of 0.001–6.0μmolL–1, with detection limit of 0.23nmolL–1, and for P4 in the range of 0.001–6.0μmolL–1, with the detection limit of 0.31nmolL–1. The prepared sensor possessed accurate and rapid response toward E2 and P4 with an improved stability, selectivity and repeatability. More importantly, the facile and environment-friendly electrochemical construction strategy provided here, may be open a cost-effective way for setting up nanocomposites or nanohybrid-based sensing platform, which extend the application of electrochemical sensor for the green, facile and sensitive analysis of electroactive compounds in biological systems and pharmaceutical formulations.
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•Fabrication of a reproducible, stable and sensitive platform for E2 and P4 oxidation was reported.•Superior properties of GQDs and PSSA were used for preparation of high performance CP/QDs hybrid materials.•The GQDs-PSSA/GO/GCE showed higher selectivity for E2 and P4 than the bare GCE.•This sensor could be a good alternative to conventional methods for the determination of steroid hormones.
Engineering of nanostructured electrodes for enhancing their electrochemical performance is a critical issue to further development in energy storage systems. In the present study, we have developed ...a facile template-free method to engineer 3D hierarchical ravine-like electrode based on MnCo2S4 nanosheet arrays as an efficient material for high-performance electrochemical capacitors. The physico-chemical characteristics of ravine-like structure of MnCo2S4 nanosheets are investigated by different techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS). The as-prepared MnCo2S4 electrode exhibits an ultrahigh specific capacity of 834 C g−1 (231 mAh g−1) at the current density of 1 A g−1, excellent rate capability and good cycle performance. Thiospinel nature of the MnCo2S4 electrode and its ravine-like nanosheet structure with effective spatial confinement for the electrolyte ions and charge transportation are responsible for this remarkable performance. Furthermore, the assembled MnCo2S4//AC asymmetric device shows the maximum energy density of 57 W h kg−1 and the highest power density of 20.8 kW kg−1.
A template-free method has been developed to engineer 3D ravine-like interconnected MnCo2S4 nanosheet arrays as a positive electrode material for asymmetric electrochemical capacitors. Display omitted
•Engineering 3D hierarchical ravine-like interconnected MnCo2S4 nanosheet arrays.•Developing a facile template free method to grow ravine-like nanostructures.•Achieving an ultrahigh specific capacity of 834 C g−1 for the MnCo2S4 electrode.•Delivering remarkable energy density and cycling stability from the MnCo2S4//AC asymmetric device.
Abstract
Exploring environment-friendly active material-electrolyte combinations has become increasingly necessary with the rising use of supercapacitors. In this study, the potential of ternary Mn
2
...SnS
3
on Ni foam as an electrode material was considered. The study investigated the impact of precursors on the morphology of the prepared electrodes utilizing techniques such as X-ray diffraction, energy dispersive X-ray analysis, field-emission scanning electron microscopy, and transmission electron microscopy. Nanocubes Mn
2
SnS
3
(NC-MTS) and nanoworms Mn
2
SnS
3
(NW-MTS) were synthesized via a facile solvothermal route. The results suggest that NC-MTS exhibits better capacitive performance compared with NW-MTS, which means that morphology has a significant effect on the electrochemical reaction. NC-MTS presents excellent supercapacitor performances with a high specific capacity of about 2115 F g
−1
at current density 2 A g
−1
, excellent rate capability of 78% at 17 A g
−1
and excellent cycling stability 92% capacitance retention after 3000 GCD cycles. Whereas, NW-MTS illustrated a specific capacity of about 853 F g
−1
at current density 2 A g
−1
, rate capability of 50% at 17 A g
−1
and cycling stability of 81% capacitance retention after 3000 GCD cycles. Additionally, an asymmetric supercapacitor NC-MTS/NF//AC based on the NC-MTS/NF as a positive electrode and activated carbon (AC) as a negative electrode was successfully constructed with the excellent electrochemical performance, which demonstrated a high energy density of 60.56 Wh kg
−1
and a high power density of 699.89 W kg
−1
.
In this study, we aim to design a simple and effective electrochemical DNA biosensor based on a carbon paste electrode modified with ds-DNA/poly(L-cysteine)/Fe3O4 nanoparticles-graphene oxide ...(ds-DNA/p(L-Cys)/Fe3O4 NPs-GO/CPE) for sensitive detection of adenine (A) and guanine (G). The electrocatalytic oxidation of A and G on the electrode was explored by differential pulse voltammetry (DPV) and cyclic voltammetry (CV). This sensor shows separated and well-defined peaks for A and G, by which one can determine these biological bases individually or simultaneously. The ds-DNA/p(L-Cys)/Fe3O4 NPs-GO/CPE exhibited an increase in peak currents and the electron transfer kinetics and decrease in the overpotential for the oxidation reaction of A and G. Under the optimal conditions a linear relationship is figured out between the peak current and the analytes' concentrations on a range of 0.01–30.0μM and 0.01–25.0μM for simultaneous determination of A and G, with detection limits of 3.48 and 1.59nM, respectively. As well as, individually determination is resulted two linear concentration ranges of 0.01–30.0μM for A and 0.01–25.0μM for G with detection limits of 3.90 and 1.58nM for A and G, respectively. The proposed biosensor exhibited some advantages in terms of simplicity, rapidity, high sensitivity, good reproducibility and long-term stability. Furthermore, the measurements of thermally denatured single-stranded DNA were carried out and the value of (G + C)/(A + T) of DNA was calculated as about 0.77 for various DNA samples. This study also ascertained that the proposed biosensor can be profitable to evaluate DNA bases damage.
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•A DNA biosensor based on ds-DNA/p(L-Cys)/Fe3O4 NPs-GO was designed.•The proposed DNA biosensor had a strongly electrocatalytic capability for A and G detection.•The contribution of ds-DNA, p(L-Cys) and GO at improving electrochemical detection was assessed.•The proposed biosensor exhibited high sensitivity and long-term stability.•The proposed biosensor could be profitable to evaluate DNA bases damage.
A magnetic bar carbon paste electrode (MBCPE) modified with cobalt ferrite magnetic electrospun nanofibers (NFs) and graphene oxide (GO) is described for the electrochemical determination of rutin. ...The NFs were prepared by electrospinning using a solution that contains poly(vinyl pyrrolidone) (PVP) and Co(II) and Fe(III) nitrates as metal sources. Carbon paste was prepared by hand mixing GO, CoFe
2
O
4
NFs and graphite. This paste was then packed into the end of a glass tube and a very small magnetic bar was inserted into the tube to be coated with the carbon paste to provide a magnetic field. The MBCPE was used to attract the magnetic nanofibers to the electrode surface. Cyclic voltammetry and differential pulse voltammetry techniques were used to study the electrochemical behavior of rutin on the modified MBCPE at pH 2.5. The electrocatalytic current, best measured at a potential of around 0.5 V (vs. Ag/AgCl), varies with the rutin concentration in two linear ranges, viz. from 0.001–0.1 nM and from 1.0–100 nM, with a 0.94 pM detection limit. The electrode was successfully applied to the determination of rutin in lemon, red apple, lime and orange juices.
Graphical abstract
Schematic representation of a modified magnetic bar carbon paste electrode for detection of rutin. To achieve the modified electrode, electrospun CoFe
2
O
4
nanofibers, graphene oxide and a very small magnetic bar are packed into the end of a glass tube.
The present work proposes a novel hierarchical nanostructure composed of the Cu-Ni nanostructured metallic foams (CN NMFs) and S-doped MnNi LDH-MWCNTs on Cu foil (CF), as an excellent self-standing ...hybrid cathode for flexible asymmetric supercapacitors. The combination of structural and compositional advantages endows the CF/CN NMFs/S-LDH-MWCNTs electrode with greatly improved electrochemical capacitive performance, including high specific capacitance (4760 F g
–1
at a current density of 1 A g
–1
) and excellent rate capability (81.9% capacitance retention at 10 A g
–1
) and superior cycling stability. Remarkably, the corresponding solid-state flexible asymmetric supercapacitor with CF/CN NMFs/S-LDH-MWCNTs and Fe
3
O
4
@ZnO-AC film as cathode and anode, respectively, delivers a high energy density up to 124.37 Wh kg
–1
as well as superb cycling stability (98.8% capacitance retention after 5000 cycles), and can be able to light up a LED indicator, demonstrating the potential for practical applications. These attractive results suggest that such an all-solid-state asymmetric supercapacitor shows great potential in developing energy storage systems with high levels of energy and power delivery.
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•Green synthesis of a nanocomposite consisting of poly(3,4-ethylenedioxythiophene) and ZrO2 nanoparticles was developed.•The nanocomposite possesses good conductivity and a ...three-dimensional microporous network structure.•The PEDOT/ZrO2-NPs/GCE exhibits excellent electrocatalytic activity towards oxidation of progesterone.•The proposed sensor was successfully applied for the determination of progesterone in biological fluids and pharmaceuticals.
The present study describes a green synthesisof a nanocomposite consisting of poly(3,4-ethylenedioxythiophene) and zirconium oxide nanoparticles. The nanocomposite possesses good conductivity and a three-dimensional microporous network structure owing to the presence of the nanoparticles. Data from the scanning electron microscopy, field-emission scanning electron microscopy, energy dispersive spectrum and Fourier transform infrared spectroscopy demonstrated that the proposed nanocomposite was successfully synthesized. A glassy carbon electrode modified with the nanocomposite exhibits excellent electrocatalytic activity towards oxidation of progesterone. Some parameters affecting the sensor response were optimized and then the calibration curve was plotted. The detection limit of 0.32 nM and two linear calibration ranges of 1–100 and 100–6 × 103 nM were obtained for progesterone determination at the proposed sensor. It was successfully applied for the determination of progesterone in biological fluids and pharmaceutical products without complex sample pretreatment.
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► Simultaneous determination of Tyr and PC has not yet been published in literature. ► The salient feature of this electrode is large effective surface area. ► The modified electrode ...has good stability and reproducibility. ► The low cost proposed electrode is resistant against surface fouling.
A novel, simple and selective electrochemical method was investigated for the single or simultaneous determination of tyrosine (Tyr) and paracetamol (PC) in aqueous media (phosphate buffer solution, pH 7.5) on MWCNTs-graphene nanosheet nanocomposite modified glassy carbon electrode (MWCNTs-GNS/GCE) using differential pulse voltammetry (DPV). The MWCNTs-GNS/GCE displayed high effective surface area, high porosity, more reactive sites and excellent electrochemical catalytic activity toward the oxidation of Tyr and PC. The peak current of differential pulse voltammograms of Tyr and PC increased linearly with their concentration in the ranges of 0.90–95.4μM Tyr and 0.80–110.0μM PC. The detection limits for Tyr and PC were 0.19μM and 0.10μM, respectively. The proposed sensor was successfully applied for the determination of Tyr and PC in human blood serum and pharmaceutical samples.
In this work, a nanoarray electrode consisting of ZnCu
2
O
4
nanoparticles (ZnCu
2
O
4
NPs) and Ni–Co layered double hydroxide (Ni–Co LDH) nanoparticles supported on Ni foam (NF) is successfully ...achieved by an in situ growth route. The pre-formed ZnCu
2
O
4
nanoparticles on Ni foam operate as a substrate and then guide the Ni–Co LDH nanoparticles on their surface by facile hydrothermal method. Electrochemical performances of the Ni–Co LDH/ZnCu
2
O
4
nanoparticles are evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge techniques (GCD), electrochemical impedance spectroscopy (EIS), and cycle life measurements in 2 mol L
–1
KOH electrolyte. The Ni–Co LDH/ZnCu
2
O
4
electrode achieves a maximum capacity of 3511.77 F g
–1
at 1 A g
–1
with raising cycling stability of 99.84% capacitance retention after 5000 cycles at 8 A g
–1
, together with ~ 100% Coulombic efficiency. In addition, an asymmetric supercapacitor is fabricated using Ni–Co LDH/ZnCu
2
O
4
NPs on Ni foam (Ni–Co LDH/ZnCu
2
O
4
NPs/NF) as the positive electrode, and activated carbon on Ni foam (AC/NF) as the negative electrode, which shows an operation voltage of 1.15 V, and high specific energy of 103.16 Wh kg
–1
at a specific power of 824.97 W kg
–1
with good cycling stability of 97.88% capacitance retention after 5000 cycles at 2 A g
–1
. Moreover, the asymmetric device displays improved low self-discharge behavior by charging it at an optimal current density and time, and the self-discharge is severely suppressed due to the presence of a 3D network of Ni–Co LDH/ZnCu
2
O
4
NPs grown on nickel foam. The unique core-shell configuration of Ni–Co LDH/ZnCu
2
O
4
can make full use of the synergistic effects of two components, provide sufficient electroactive sites, as well as facilitate the charge transport process because of their considerable electrochemical properties, making it a potential choice for electrochemical energy storage.
In this study, ZnO/ZIF-67 was synthesized on nickel foam and subsequently evaluated for its chemical behavior using a three-electrode system in a 2 mol L
–1
KOH electrolyte. Cyclic voltammetry and ...galvanostatic charge and discharge analysis measurements were employed. At a current density of 1 A g
–1
, ZnO/ZIF-67 exhibited the highest specific capacitance of 2908 F g
–1
. The suggested electrode demonstrated excellent cycle stability, maintaining its performance over 5000 charge–discharge cycles. Furthermore, the retention capacity of ZnO/ZIF-67 was determined to be 95.3%, accompanied by an approximate 100% coulombic efficiency. Subsequently, an asymmetric supercapacitor was constructed to investigate the system's capacitive behavior. The maximum specific capacitance of the two-electrode device was obtained as 264.4 F g
–1
at a current density of 1 A g
–1
, with approximately 78.8% of the capacitance retained even after 5000 charge–discharge cycles. These results highlight the potential utilization of ZnO/ZIF-67 nanostructures in advancing the development of next-generation supercapacitors.
