Fabrication and characterization of grafted polymer electrode self modification with activated carbon
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A new grafted polymer electrode self modified with activated carbon (GPESMAC) was fabricated and electrochemical characterization by cyclic voltammetric analysis. The polystyrene was used as polymer grafted with acrylonitrile as a monomer and activated carbon as improvement material using gamma irradiation to produce a new copolymer. The redox process of K3Fe(CN)6 during cyclic voltammetry was studied with the new working electrode (GPESMAC) by cyclic voltammetric analysis. The physical properties of these electrodes have high hardness, insolubility, and stability at different high temperatures. Also, the sensitivity under conditions of cyclic voltammetry is significantly dependent on different scan rate and concentrations. The GPESMAC was characterized by surface analytical methods including SEM and AFM. Interestingly, the redox reaction of Fe(III) solution using GPESMAC remained constant even after 15 cycles. It is therefore evident that the GPESMAC possesses some degree of stability. The potential use of the grafted polymer as a useful electrode material is therefore clearly evident. It is through the study of applications in quantitative and qualitative analysis proved that the conductivity of grafted polymer with activated carbon is highly efficient and stability compared with the commercial solid electrodes and modified by mechanical means or by evaporating the solvent, such as glassy carbon electrode. On the other hand an enhancement of redox current peaks and high detection limits effective species such as Fe(II)/Fe(III) was studied.
KeywordsGrafted polymer electrode self modified Activated carbon Redox couple Fe(III)/Fe(II) Electrocatalysis Cyclic voltammetry
The process of modifying polymers with good conductive materials stirs the attention of the scientists in recent times. One of these methods is irradiation of grafting polymers and modified with conductive materials to be used for multiple purposes, especially in the field of conductors and semiconductors, as well as in electrochemistry [1, 2, 3, 4].
A composite polymer membrane working electrode has been studied at cyclic voltammetric for famotidin and terthiophene determination of drug in pharmaceutical formulation. This composite film of polymer electrode showed good catalytic behavior, which includes a good current response [5, 6].
The modified electrode functionalized with polyacrylic acid (PAA) tethered to indium tin oxide (ITO) and covered with gold nanoparticle (ITO/PAA/Au) demonstrated switchable interfacial properties discriminating different pH. The switchable electrochemical and plasmonic process was characterized by cyclic voltammetry (CV), electrochemistry impedance spectroscopy (EIS), and localized surface plasmon resonance (LSPR) .
Grafted molecularly imprinted (MIP) polymer thin films onto Au electrodes was studied as good sensor in the presence of N,N′-methylenebis(acrylamide) to detection of hydroquinone .
Another study for using a molecularly imprinted polymer (MIP) as a recognition element in the development of a heparin sensor for real-time monitoring. An indium tin oxide (ITO) electrode grafted with a heparin-specific MIP was used as a working electrode to perform cyclic voltammetry of ferrocyanide. The anodic current was found to be dependent on heparin concentration. Therefore, the MIP-grafted electrode is suitable for real-time monitoring of heparin in blood. The advantage of these method is that a very small volume of blood is needed, which is very important, especially when regular measurements are required .
The electrical connectivity of grafted polymer with pair of electrons located on the nitrogen atom within the structure of grafted polymer, and in addition to that the presence of high conductivity in a series of a activated carbon is one of the reasons used in the manufacture of electrodes operating polymeric high connectivity characteristic, which is mainly used in the analysis electrochemistry, especially in a cyclic voltammetry .
One of the syntheses of grafting polymers is electropolymerization of statistically exposed dithiobenzoate moieties served as a chain transfer agent for the polymerization of styrene on a matrix of an electrodeposited conjugated polymer. The polystyrene modified substrate was then used as the macro chain transfer agent for the synthesis of the second block of poly-tert-butyl acrylate on the surface. The polymerization from the surface was characterized by surface analytical methods including AFM, XPS, and contact angle measurements [10, 11, 12, 13, 14].
In this work, grafted polymer was modified with activated carbon to fabrication grafted polymer electrode self modified with activated carbon by gamma ray. The new grafted polymer electrode was electrochemically characterized in K3Fe(CN)6 with KCl aqueous electrolyte by CV technique.
Synthesis of grafted polymer modified with activated carbon (GP/AC)
Polystyrene-acrylonitrile was grafted with activated carbon (AC) as an improvement material, using gamma-irradiation. The new grafted polymer modified with activated carbon indicated that the best grafting percentage ratio could be revealed when the concentration of the catalyst ferrous ammonium sulphate (FAS) is about 2 % and the monomer concentration is 90 %, at gamma ray dose 1.25 M rad .
Instrument and electroanalytical methods
Electrochemical workstations of NuVant Systems Inc., USA (EZ stat series with potentiostat/glvanostat driven by electroanalytical measuring software) were connected to a PC computer in order to perform cyclic voltammetry (CV), chronoamperometry (CC), and chronoamperometry (CA). An Ag/AgCl (3 M NaCl) and platinum wire (1 mm diameter) were used as the reference and counter electrodes, respectively.
Grafted polymer electrode self modified with AC was used as a working electrode in this study. The voltammetric experiments were carried out with 0.1 M KCl as supporting electrolyte and using K3Fe(CN)6 solution for calibration. The solution was degassed with nitrogen gas for 10–15 min prior to recording the voltammogram.
All reagents were analytical reagents or electrochemical grade purity. All solutions were prepared using double distilled water. Unless otherwise specified, the supporting electrolyte was used 0.1 M KCl in aqueous media at room temperature.
Fabrication of grafted polymer electrode self modified with activated carbon (GPESMAC)
GPESMAC has been fabricated from grafted polymer modified with activated carbon. The diameter of electrode was 3 cm. A (1 mm) hole was made in the grafted polymer to allow 1 cm length of platinum wire out from the other side of electrode. A copper wire was then joined with the platinum wire. After that, all parts of fabricated electrode were covered with glassy tube and then fixed with epoxy resin.
Results and discussion
Electrochemical properties of grafted polymer electrode self modified with activated carbon (GPESMAC)
Potential window of GPESMAC
Effect of GPESMAC on the redox reaction of K3[Fe(CN)6] during CV
Effect of varying scan rate
Effect of varying temperature
From the relationship between log(Ia) and 1/T of the oxidation K3Fe(CN)6 as Fe(II)/Fe(III) the activation energy was found 6.32 kJ/mol in GPESMAC comparison with other studies .
Effect of varying K3Fe(CN)6 concentration
The potential cycling of the redox of GPESMAC in 1 mM K4Fe(CN)6 and 1 M KCl aqueous solution as a supporting electrolyte was carried out during cyclic voltammetry. Continuous potential cycling did not seem to affect the redox current of GPESMAC as the faradic activity appears reproducible even after 15 cycles, reflecting the stability and reproducibility at the surface of GPESMAC.
Scanning electron microscopy (SEM) of GPE/AC
Atomic force microscopy (AFM)
A grafted polymer electrode self modified with activated carbon GPESMAC has been fabricated in laboratory for using in cyclic voltammetric technique as a working electrode. The new electrode was used as alternative of working electrodes modified with deposit materials such as activated carbon using classical modification methods (attachment or solvent evaporation methods). The CV analysis results of these electrodes have an extended potential working region as compared to the routine modification method of GCE with activated carbon and have high stability and reproducibility. Redox peaks of Fe(II)/Fe(III) showed high current as compared with other modified electrodes.
Electro-catalytic activity of GPESMAC is therefore evident in this study, it was studied by redox process of K3Fe(CN)6 during cyclic voltammetry. The redox peaks potential shifts slightly to less negative value by about 100 mV for oxidative peak and 50 mV for reductive peak with current enhancement of about 3-fivefolds. The sensitivity under conditions of cyclic voltammetry is significantly dependent on the concentration, scan rate and temperature. Excellent reproducibility and stability of the current is observed, provided a fabricated electrode is used for each experiment without any polishing.
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