Multicore-shell MnO2@Ppy@N-doped porous carbon nanofiber ternary composites as electrode materials for high-performance supercapacitors

In this study, a multicore-shell ternary composite electrode material (MnO₂@Ppy@NPCNFs) with excellent electrochemical performances was prepared by using surface modification, in which core-shell Ppy@N-doped porous carbon nanofibers (Ppy@NPCNFs) with large specific surface area and high conductivity were used as the substrate (a multicore layer), and MnO₂ was loaded on the substrate by hydrothermal synthesis to form a shell layer, further improving the SC of electrode material. The parameters of hydrothermal growth of MnO₂ on Ppy@NPCNFs were explored by means of the control variable method and response surface methodology, and the optimal parameters were predicted and verified. Electrochemical test results showed that the SC of MnO₂@Ppy@NPCNFs prepared under the optimal reaction parameters was as high as 595.77 F g^-1, and its capacitance retention was 96.2 % after 1000 cycles. Moreover, a symmetric supercapacitor prepared with the optimal multicore-shell electrode showed an energy density of 9.36 Wh kg^-1 at a power density of 1000 W kg^-1 and a retention rate of 92.46 % after 1000 cycles, indicating the promising application of multicore-shell ternary composite electrode material in high-performance supercapacitors.

A glassy carbon electrode modified with reduced graphene oxide and gold nanoparticles for electrochemical aptasensing of lipopolysaccharides from Escherichia coli bacteria

An electrochemical aptasensor is described for the voltammetric determination of lipopolysaccharide (LPS) from Escherichia coli 055:B5. Aptamer chains were immobilized on the surface of a glassy carbon electrode (GCE) via reduced graphene oxide and gold nanoparticles (RGO/AuNPs). Fast Fourier transform infrared, X-ray diffraction and transmission electron microscopy were used to characterize the nanomaterials. Cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy were used to characterize the modified GCE. The results show that the modified electrode has a good selectivity for LPS over other biomolecules. The hexacyanoferrate redox system, typically operated at around 0.3 V (vs. Ag/AgCl) is used as an electrochemical probe. The detection limit is 30 fg·mL^-1. To decrease the electrochemical potential for detection of LPS, Mg/carbon quantum dots were used as redox active media. They decrease the detection potentialto 0 V and the detection of limit (LOD) to 1 fg·mL^-1. The electrode was successfully used to analyze serum of patients and healthy persons. Graphical abstractSchematic representation of the modification of reduced graphene oxide gold nanoparticles with aptamer chains to immobilize on the glassy carbon electrode surface for electrochemical detection of lipopolysaccharides.

An electrochemical biosensor for prostate cancer biomarker detection using graphene oxide-gold nanostructures

In this paper, a most sensitive electrochemical biosensor for detection of prostate-specific antigen (PSA) was designed. To reach the goal, a sandwich type electrode composed of reduced graphene oxide/ gold nanoparticles (GO/AuNPs), Anti-Total PSA monoclonal antibody, and anti-Free PSA antibody was assembled. The functionalized materials were thoroughly characterized by atomic force microscope spectroscopy, transmission electron microscopy, and X-ray diffraction techniques. The electrochemical properties of each of the modification step were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The results presented that the proposed biosensor possesses high sensitivity toward total and free PSA. Furthermore, the fabricated biosensor revealed an excellent selectivity for PSA in comparison to the other tumor markers such as BHCG, Alb, CEA, CA125, and CA19-9. The limit of detection for the proposed electrochemical biosensor was estimated to be around 0.2 and 0.07 ng/mL for total and free PSA antigen, respectively.

MOF-derived microstructural interconnected network porous Mn2O3/C as negative electrode material for asymmetric supercapacitor device

A metal–organic framework is employed for the preparation of an interconnected network porous structure of Mn₂O₃/carbon for supercapacitor applications.

Enhancement of corrosion resistance of polypyrrole using metal oxide nanoparticles: Potentiodynamic and electrochemical impedance spectroscopy study

We introduce a simple and facile strategy for dispersing of nanoparticles within a p-type conducting polymer matrix by in situ electropolymerization using oxalic acid as the supporting electrolyte. Coatings prepared from polypyrrole-nano-metal oxide particles synthesized by in situ polymerization were found to exhibit excellent corrosion resistance much superior to polypyrrole (Ppy) in aggressive environments. The anti-corrosion behavior of polypyrrole films in different states and the presence of TiO₂, Mn₂O₃ and ZnO nanoparticles synthesized by electropolymerization on Al electrodes have been investigated in corrosive solutions using potentiodynamic polarization and electrochemical impedance spectroscopy. The electrochemical response of the coated electrodes in polymer and nanocomposite state was compared with bare electrodes. The use of TiO₂ nanoparticles has proved to be a great improvement in the performances of polypyrrole films for corrosion protection of Al samples. The polypyrrole synthesized in the presence of TiO₂ nanoparticles coated electrodes offered a noticeable enhancement of protection against corrosion processes. The exceptional improvement of performance of these coatings has been associated with the increase in barrier to diffusion, prevention of charge transport by the nanosize TiO₂, redox properties of polypyrrole as well as very large surface area available for the liberation of dopant due to nano-size additive.

Facile electrosynthesis of nano flower like metal-organic framework and its nanocomposite with conjugated polymer as a novel and hybrid electrode material for highly capacitive pseudocapacitors

The [Cu(btec)_0.5DMF] (H₄btec=1,2,4,5-benzenetetracarboxylate acid) was electrosynthesized on the graphite working electrode by applying catholic potential. The [Cu(btec)_0.5DMF] grows on a graphite surface which results from the coordination of 1,2,4,5-benzenetetracarboxylate anions with Cu²⁺ cations. The electrosynthesized [Cu(btec)_0.5DMF] was characterized by X-ray diffraction, scanning electron microscopy. Furthermore, POAP/Cu(btec)_0.5DMF nanocomposite film electrosynthesized on the surface of the carbon paste electrode by cyclic voltammetry. Different electrochemical methods including galvanostatic charge-discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area and stability in an aqueous electrolyte.

Facile electrosynthesis, characterisation and electrochemical performance of poly ortho aminophenol/Al5Y3O12 nanocomposite as a new high efficient supercapacitor

In this paper, firstly Al₅Y₃O₁₂ has been synthesized without any impurities using pulse electrochemical deposition and then fabricated POAP/YAG films to serve as the active electrode for the electrochemical supercapacitor.

Physicoelectrochemical properties of facilely electrosynthesized reduced graphene oxide/p-type conductive polymer nanocomposite film

As electro-active electrodes, composites of reduced graphene oxide and poly ortho aminophenol (POAP) with good uniformity are prepared by electropolymerization. In comparison with Ni-POAP, the Ni-rGO/POAP-modified electrode shows a higher response for methanol oxidation.

One-step electrochemical preparation and characterization of nanostructured hydrohausmannite as electrode material for supercapacitors

A novel, simple one-pot electrochemical procedure is proposed for the preparation of hydrohausmannite.

Electrochemical study of supercapacitor performance of polypyrrole ternary nanocomposite electrode by fast Fourier transform continuous cyclic voltammetry

The supercapacitive behavior of polypyrrole/reduced graphene oxide/Au nanoparticles as a ternary composite electrode was studied by CV, galvanostatic charge/discharge, EIS and fast Fourier transform continuous cyclic voltammetry techniques.