Free-standing conductive hydrogel electrode for potentiometric glucose sensing

Flexible conductive polymer hydrogels are attracting attention as an electrode material. Electrochemical biosensors with conductive polymer hydrogels have been developed because they have some advantages such as biocompatibility, high conductivity, 3D nanostructure, solvated surface, and enlarged interface. Conductive polymer hydrogels bearing receptor molecules such as enzymes in its 3D nanostructure enable the detection of target analytes with high sensitivity. However, because such hydrogels are fragile, they cannot stand on their own and a supporting substrate is required to fabricate them. This means that the loss of mechanical toughness is detrimental for their application to flexible biosensors. In this study, we have proposed a free-standing conductive hydrogel electrode with no coating on a substrate, which is composed of polyaniline with phenyl boronic acid including polyvinyl alcohol, for potentiometric glucose sensing. In addition, its electrical responsivity to glucose has been confirmed by investigating its mechanical properties at various glucose concentrations, considering the hydrogel compositions.

A free-standing conductive hydrogel electrode with no coating on a substrate is proposed for potentiometric glucose sensing.

Exploring the Functional Properties of Sodium Phytate Doped Polyaniline Nanofibers Modified FTO Electrodes for High-Performance Binder Free Symmetric Supercapacitors

The performance of high-rate supercapacitors requires fine morphological and electrical properties of the electrode. Polyaniline (PANI), as one of the most promising materials for energy storage, shows different behaviour on different substrates. The present study reports on the surface modification of fluorine doped tin oxide (FTO) with the sodium phytate doped PANI without any binder and its utilization as a novel current collector in symmetric supercapacitor devices. The electrochemical behaviour of the sodium phytate doped PANI thin film with and without a binder on fluorine doped tin oxide (FTO) as current collector was investigated by cyclic voltammetry (CV). The electrode without a binder showed higher electrocatalytic efficiency. A symmetrical cell configuration was therefore constructed with the binder-free electrodes. The device showed excellent electrochemical performance with high specific capacities of 550 Fg⁻¹ at 1 Ag⁻¹ and 355 Fg⁻¹ at 40 Ag⁻¹ calculated from galvanostatic discharge curves. The low charge transfer and solution resistances (R_CT and R_S) of 7.86 Ωcm² and 3.58 × 10⁻¹ Ωcm², respectively, and superior rate capability of 66.9% over a wide current density range of 1 Ag⁻¹ to 40 Ag⁻¹ and excellent cycling stability with 90% of the original capacity over 1000 charge/discharge cycles at 40 Ag⁻¹, indicated it to be an efficient energy storage device. Moreover, the gravimetric energy and power density of the supercapacitor was remarkably high, providing 73.8 Whkg⁻¹ at 500 Wkg⁻¹, respectively. The gravimetric energy density remained stable as the power density increased. It even reached up to 49.4 Whkg⁻¹ at a power density of up to 20 Wkg⁻¹.

An Amazingly Simple, Fast and Green Synthesis Route to Polyaniline Nanofibers for Efficient Energy Storage

The major drawbacks of the conventional methods for preparing polyaniline (PANI) are the large consumptions of toxic chemicals and long process durations. This paper presents a remarkably simple and green route for the chemical oxidative synthesis of PANI nanofibers, utilizing sodium phytate as a novel and environmentally friendly plant derived dopant. The process shows a remarkable reduction in the synthesis time and usage of toxic chemicals with good dispersibility and exceedingly high conductivity up to 10 S cm⁻¹ of the resulting PANI at the same time. A detailed characterization of the PANI samples has been made showing excellent relationships between their structure and properties. Particularly, the electrochemical properties of the synthesized PANI as electrode material for supercapacitors were analyzed. The PANI sample, synthesized at pre-optimized conditions, exhibited impressive supercapacitor performance having a high specific capacitance (C_sp) (832.5 Fg⁻¹ and 528 Fg⁻¹ at 1 Ag⁻¹ and 40 Ag⁻¹, respectively) as calculated from galvanostatic charge/discharge (GCD) curves. A good rate capability with a capacitance retention of 67.6% of its initial value was observed. The quite low solution resistance (R_s) value of 281.0 × 10⁻³ Ohm and charge transfer resistance value (R_ct) of 7.44 Ohm represents the excellence of the material. Further, a retention of 95.3% in coulombic efficiency after 1000 charge discharge cycles, without showing any significant degradation of the material, was also exhibited.

Supercapacitive Properties of 3D-Arrayed Polyaniline Hollow Nanospheres Encaging RuO2 Nanoparticles

A major limitation of polyaniline (PANi) electrodes for supercapacitors is the slow rate of ion transport during redox reactions and the resultant easy saturation of areal capacitance with film thickness. In this study, three-dimensionally (3D)-arrayed PANi nanospheres with highly roughened surface nanomorphology were fabricated to overcome this limitation. A hierarchical nanostructure was obtained by polymerizing aniline monomers on a template of 3D-arrayed polystyrene (PS) nanospheres and appropriate oxidative acid doping. The structure provided dramatically increased surface area and porosity that led to the efficient diffusion of ions. Thus, the specific capacitance (C_sp) reached 1570 F g^-1, thereby approaching a theoretical capacitance of PANi. In addition, the retention at a high scan rate of 100 mV s^-1 was 77.6% of the C_sp at a scan rate of 10 mV s^-1. Furthermore, 3D-arrayed hollow PANi (H-PANi) nanospheres could be obtained by dissolving the inner PS part of the PS/PANi core/shell nanospheres with tetrahydrofuran. The ruthenium oxide (RuO₂) nanoparticles (NPs) were also encaged in the H-PANi nanospheres by embedding RuO₂ NPs on the PS nanospheres prior to polymerization of PANi. The combination of the two active electrode materials indicated synergetic effects. The areal capacitance of the RuO₂-encaged PANi electrode was significantly larger than that of the RuO₂-free PANi electrode and could be controlled by varying the amount of encaged RuO₂ nanoparticles. The encagement could also solve the problem of detachment of RuO₂ electrodes from the current collector. The effects of the nanostructuring and RuO₂ encagement were also quantitatively analyzed by deconvoluting the total capacitance into the surface capacitive and insertion elements.

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.

Synthesis and highly efficient supercapacitor behavior of a novel poly pyrrole/ceramic oxide nanocomposite film

This work introduces new nanocomposite materials (Ppy/YAG) for electrochemical redox capacitors with advantages including long life cycle and stability in an aqueous electrolyte to that of commonly used ruthenium based pervoskites.

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.

Physioelectrochemical investigation of the supercapacitive performance of a ternary nanocomposite by common electrochemical methods and fast Fourier transform voltammetry

Fast Fourier transform continuous cyclic voltammetry as a new technique for the explanation of a composite electrode for supercapacitors.

Continuous fast Fourier transform admittance voltammetry as a new approach for studying the change in morphology of polyaniline for supercapacitors application

In this study, continuous fast Fourier transform admittance voltammetry (CFFTAV) was used to study and characterize the surface morphology of polyaniline (PANI) on glassy carbon (GC) electrodes.