Electropolymerization Conditions Research Articles

Synthesis and characterization of polypyrrole – TiO2 coatings on AISI 304 stainless steel

The electrical properties of conducting polymers make them interesting materials to be used in a large number of technological applications. In recent years, an important effect on the anticorrosive properties of the conductive polymer was observed when inorganic particles such as nano-sized TiO2 are incorporated in the conductive matrix. In the present study, polypyrrole films were synthesized in the presence of TiO2 nanoparticles. A study of the electropolymerization conditions, thickness of the formed films and the effect of incorporation of TiO2 nanoparticles on the structure of the polymer matrix by Raman spectroscopy was performed. These results show that it is possible to obtain the adherent coatings, with thicknesses between 3-4 µm. However, the presence of TiO2 nanoparticles in the polymeric matrix influences the corrosion resistance of the polypirrole coatings, destabilizing the natural passive capacity on the surface of AISI 304 stainless steel.

Electrochemical sensor based on electropolymerized dopamine molecularly imprinted film for tetrabromobisphenol A

This work reported the simple and direct detection of 3,3′,5,5′‑tetrabromobisphenol A (TBBPA) by a polydopamine imprinted electrochemical sensor. The imprinted film was directly prepared by electropolymerization of dopamine on a glassy carbon electrode in the presence of template molecule, and then characterized using electrochemical probe of potassium ferricyanide, scanning electron microscopy and atomic force microscopy. It was found that the obtained sensing film greatly enhanced the oxidation signals of TBBPA due to strong accumulation ability. The influences of electropolymerization conditions (e.g. template concentration, scan cycles and scan rates), accumulation time and pH value were studied. The developed sensing platform exhibited good reproducibility, excellent sensitivity and selectivity, offering a low detection limit (0.27 nM) and a linear range from 1 to 50 nM. It was applied for TBBPA detection in plastic e-waste samples, and the results were consistent with those obtained by high-performance liquid chromatography.

Enhancement Supercapacitive Behavior of Electrodeposited Doped Polypyrrole for Supercapacitor Applications

Polypyrrole (PPy) have been extensively studied because of their low cost, easy production, good conductivity and controlled doping/de-doping properties as well as extensive applications in various areas such as energy storage, sensors, and electronic devices 1, 2. A detailed study of the effects of different electropolymerization conditions on the supercapacitive properties of polypyrrole (ppy) films doped using different dopants deposited on stainless steel was reported. The resulting thin films have been characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The electrochemical properties of PPy thin films were investigated by cyclic voltammetry, electorochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge. The results showed that the different electrodeposition operating conditions of synthesis and the type of dopant and the electrolyte used significantly affect the supercapacitive properties of PPy thin films. Thus, these results provide a useful orientation for the use of optimized electrodeposition modes for the growth of PPy thin films to be applied as electrode material in supercapacitors and achieved a specific capacitance of 266 F/g for amperometric deposited PPy thin film doped with 0.03 M dodecylbenzene sulfonic acid (DBSA) and using 0.1 M H2SO4 as an electrolyte. References Cai, Z.; Xiong, H.; Zhu, Z.; Huang, H.; Li, L.; Huang, Y.; Yu, X., Electrochemical synthesis of graphene/polypyrrole nanotube composites for multifunctional applications. 2017, Synthetic Metals 227, 100-105.Dubal, D. P.; Lee, S. H.; Kim, J. G.; Kim, W. B.; Lokhande, C. D., Porous polypyrrole clusters prepared by electropolymerization for a high performance supercapacitor. 2012, Journal of Materials Chemistry 22, 3044-3052. Figure 1: Cyclic voltammetry of PPy doped by DBSA and a schematic diagram of supercapacitor components Figure 1

Tailorable drug capacity of dexamethasone-loaded conducting polymer matrix

The unique properties of conducting polymers, which are in the same time biocompatible and electrically responsive materials, make them perfect candidates for controlled drug release systems. In this study, the electrically-triggered controlled release system based on dexamethasone-loaded poly (3, 4-ethylenedioxypyrrole) (PEDOP) matrix is described. It is shown that the electropolymerization conditions can facilitate or suppress the formation of PEDOP/Dex matrix, as well as they can have the effect on its electrochemical performance. The release experiments performed in three different modes show that the drug capacity of PEDOP matrix increases with the increase in Dex concentration in the step of matrix synthesis, and higher Dex concentrations make it easier to control the amount of Dex released in an electrically-triggered mode. These results confirm the importance of the careful optimization of immobilization conditions to maximize drug capacity of matrix and maintain its electrochemical properties.

Enhanced thermoelectric properties of electropolymerized poly (3,4-ethylenedioxythiophene) thin films by optimizing electrolyte temperature and thermal annealing temperature

Effects of electrolyte temperature and annealing temperature on ClO4-doped poly (3,4-ethylenedioxythiophene) (PEDOT) thin films were investigated. Prior to the electropolymerization of the thin films, we performed cyclic voltammetry (CV) analysis while changing the electrolyte temperature between 0 °C and 60 °C. The current density increased with increasing electrolyte temperature, and the onset oxidation potential was mostly constant at approximately 1.3 V. From the CV analysis, we determined the electropolymerization condition of electrolyte temperature 50 °C and applied potential 1.52 V. Following the electropolymerization of the PEDOT thin films, thermal annealing was implemented in the range 80 °C to 140 °C with a mixture of argon (95%) and hydrogen (5%) gases at atmospheric pressure. ESR analysis showed that the intensity of the ESR spectra decreased with increased annealing temperature because of the decrease of charge-trapping related defects. In the annealed samples, the electrical conductivity of PEDOT thin films increased and the Seebeck coefficient decreased with increased annealing temperature; this was supported by the ESR analysis results. As a result, PEDOT thin films annealed at 80 °C and 100 °C exhibited a maximum power factor of 0.8 μW/(m·K2). Therefore, we conclude that the moderate annealing treatment enabled the thermoelectric performance to improve.

Influence of the Electropolymerization Parameters on the Doping Level of Polybithiophene Films Grown in Acetonitrile and Water

Electropolymerized polythiophene (PTh) is a conductive polymer with low crystallinity, excellent thermal stability, and good conductivity. Its applications strongly depend on the electrochemical conditions employed during film growth, the nature of the doping counterion, the substituents attached to the thiophene ring, and the reaction medium employed. Electropolymerization of bithiophene (BTh) to produce polybithiophene (PBTh) can be successful both in aqueous and organic media. The objective of the present study was to compare the influence of the electropolymerization conditions on the doping level (δ) of PBTh films. A high doping level was reached using ACN as solvent (% δ = 25.58% ± 0.77), while in water the electropolymerization was strongly inhibited. The study of in-situ conductance during electropolymerization in ACN showed a conductance increase with the number of cycles, while conductance did not increase in water. This electropolymerization inhibition is attributed to a nucleophilic attack by the H2O molecule on the cationic species formed during the oxidation of PBTh.

Preparation of High Charge Storage Capacity PEDOT/Functionalized Mwcnts Hybrid Nanocomposite for Neural Electrode Applications

There is an ever growing demand for the development of high charge storage capacity, biocompatible microelectrodes, which are essential for neural recording and stimulation applications. The challenge here is to increase the charge storage capacity. Higher charge density would enable to pump in higher charge at the electrode/biological element interface even in with a smaller area electrode. However, there is a tradeoff between electrode dimension and interface impedance. A decrease in the electrode dimension results in low capacitance and high impedance which is a major drawback for stimulation because higher signal amplitudes are required for efficiently stimulating the cells. In order to overcome this bottleneck, it is imperative to develop materials having higher active area for the same geometric area. This not only reduces the interface impedance but also increases the specific capacitance. In developing these materials, biocompatibility and long term stability considerations must be taken into consideration. Biocompatible conducting polymers are good candidates for these applications and are being utilized as electrode materials in neuro prosthesis research for the past two decades. Yet the quest of high charge density electrode is still unmet. Among them, PEDOT (Poly Ethylene Dioxy Thiophene) is considered to be one of the promising conducting polymers due to its excellent electronic and ionic conductivity which cater low impedance and high specific capacitance, ease of fabrication by electro chemical polymerization along with excellent biocompatibility and bio stability. But PEDOT suffers from low cycling stability due to its low mechanical strength leading to decrease in pseudo capacitance and conductivity. Choosing the right dopant in PEDOT could potentially overcome these issues. In this work, we have synthesized different hybrid nanocomposites of PEDOT by doping different types carbon based 2D nanomaterials. The syntheses of these nanocomposites were carried out using electro polymerization. The electrode deposition was carried out using Chrono Amperometry, a widely used Potentiostatic technique. The idea behind using these 2D nanomaterials is well explored owing to the inherent advantages of these materials such as extraordinary mechanical strength, electrical conductivity and high chemical stability. Furthermore, the high surface to volume ratio results in higher surface charge, thereby resulting in a higher storage capacity. The focus of this endeavor is to study the charge storage capacity of the synthesized hybrid nanocomposites. The dopants that were used to synthesize the nano composites were Graphene nano platelets, Graphene Oxide, Multiwalled Carbon Nanotubes (MWCNTs) and functionalized MWCNTs. Similar conditions were adapted for electro polymerization. All the experiments were carried out at a scan rate of 100 mV/s using CH Instruments electro chemical setup shown in Fig.1. These include finite pulse potential amplitude of 1V and 120s pulse duration. Amongst all the materials, functionalized MWCNTs demonstrated the highest charge storage capacity as can be inferred by the cyclic voltammograms shown in Fig. 2(a). Functionalized CNTs not only disperse well in the precursor solution but also get embedded in a greater quantity in PEDOT matrix owing to their inherent negative charge. After identifying the right choice of dopant, the next step is to optimize the electro polymerization conditions so as to enhance the charge storage capacity to the best possible value. Cyclic voltammograms (CV) of PEDOT/Functionalized MWCNTs (PEDOT/FCNTs) as shown in Fig. 2(b) reveals that the area of the CV curve is highest for a loading percentage (wt/vol) of 1 mg/ml compared to other loading percentages. We observed that beyond 1 mg/ml, the excess concentration of MWCNTs is impeding the electro polymerization and is not resulting in a good film. The loading was fixed to 1 mg/ml for subsequent experiments. The next parameter that was optimized is the potential of electro polymerization with the duration of electro polymerization being 800s. As can be observed from Fig. 2(c), the suitable potential is 1 V. Voltages beyond this show a reduced charge storage and may be attributed to over oxidation during polymerization. Similarly, Fig. 2(d) reveals that area of the CV curve has attained maximum at pulse duration of 800s by keeping the amplitude as constant at 1V. Fig. 3 depicts the magnitude plot of electrode interface impedance for the PEDOT/CNT-COOH nanocomposite deposited at 1V with pulse duration of 800s in the frequency range of 0.1Hz to 1MHz. Hence, the best possible charge storage capacity and lowest interface impedance is obtained for a ratio of 1mg/ml (wt/vol) with electro polymerization amplitude of 1V and pulse duration 800s. Further morphological studies would be carried out in due of course of time to gain a deeper understanding in the synthesis of hybrid nanocomposite of PEDOT/FCNTs. Figure 1

Localized Detection of d‐Serine by using an Enzymatic Amperometric Biosensor and Scanning Electrochemical Microscopy

Abstractd‐Serine acts as an endogenous co‐agonist for N‐methyl‐d‐aspartate receptors at synapses, making it essential for proper brain development and function. This amino acid has also been linked to several neurodegenerative diseases such as Alzheimer's disease and dementia. Nevertheless, the primary site and mechanism of d‐serine release remains unclear. We recently demonstrated the use of an enzymatic amperometric biosensor for the in vivo quantification of endogenous d‐serine release in Xenopus laevis tadpoles. Herein, we investigate the effect of the permselective poly(meta‐phenylenediamine) electropolymerization conditions on the biosensor's response time and selectivity. Scanning electrochemical microscopy (SECM) is then used with the optimized biosensor to measure localized release of d‐serine from a model system. This SECM methodology, which provides high spatial and temporal resolution, could be useful to investigate the primary site and mechanism of d‐serine release in other biological samples.

Highly sensitive and selective voltammetric determination of dopamine using a gold electrode modified with a molecularly imprinted polymeric film immobilized on flaked hollow nickel nanospheres

The authors describe the preparation of a molecularly imprinted polymer (MIP) film on the surface of electrodeposited hollow nickel nanospheres (hNiNS), and the use of this nanocomposite in an electrochemical sensor for dopamine (DA). The use of the 3-dimensional hNiNS as a support material enlarges the sensing area and conductivity, while the MIP film warrants improved selectivity for DA. Quantification based on the “MIP/gate effect” was performed by employing hexacyanoferrate as the electrochemical probe. Scanning electron microscopy, cyclic voltammetry and electrochemical impedance spectroscopy were applied to characterize the sensor materials. The electropolymerization condition such as pH value, functional monomer and ratio of template to monomer were optimized. By using dopamine (DA) as a model analyte, the sensor, if operated at 0.1 V vs. SCE, has fairly low detection limit of 1.7 × 10−14 M (at an S/N ratio of 3), two wide assay ranges of 5 × 10−14 to 1 × 10−12 M and 1 × 10−12 to 5 × 10−11 M, and superb selectivity.

Synthesis and characterization of nanocomposites based on PANI and carbon nanostructures prepared by electropolymerization

Nanocomposites based on polyaniline (PANI) and carbon nanostructures (CNSs) (graphene (G) and multiwall carbon nanotubes (MWCNTs)) were prepared by in situ electrochemical polymerization. CNSs were inserted into the PANI matrix by dispersing them into the electrolyte before the electropolymerization. Electrochemical characterization by means of cyclic voltammetry and steady state polarization were performed in order to determine conditions for electro-polymerization. Electro-polymerization of the PANI based nanocomposites was carried out at 0.75 V vs. saturated calomel electrode (SCE) for 40 and 60 min. The morphology and structural characteristics of the obtained nanocomposites were studied by scanning electron microscopy (SEM) and Raman spectroscopy, while thermal stability was determined using thermal gravimetric analysis (TGA). According to the morphological and structural study, fibrous and porous structure of PANI based nanocomposites was detected well embedding both G and MWCNTs. Also, strong interaction between quinoidal structure of PANI with carbon nanostructures via π–π stacking was detected by Raman spectroscopy. TGA showed the increased thermal stability of composites reinforced with CNSs, especially those reinforced with graphene.

Effects of Electropolymerization Parameters of PPy(DBS) Surfaces on the Droplet Flattening Behaviors During Redox.

We present a systematic study on the effects of electropolymerization parameters of polypyrrole-dodecylbenzenesulfonate (PPy(DBS)) surfaces on the flattening behaviors of organic droplets during reduction and oxidation (redox). PPy(DBS) surfaces were fabricated under varying electropolymerization conditions, including voltage, surface charge density, and dopant electrolyte (DBS-) concentration. The flattening behaviors on different PPy(DBS) surfaces were characterized by analyzing droplet behaviors and energy-dispersive X-ray spectroscopy (EDS) data. The surface charge density and voltage during electropolymerization determined the thickness and doping ratio of synthesized PPy(DBS) surfaces, affecting how DBS- molecules are released from PPy(DBS) upon reduction. The release amount and rate of DBS- molecules were strongly related to the droplet flattening time.

Electrochemical Study of Conducting Poly(thionine) Electropolymerization in Two Methods and Its Significance for the Detection of Dopamine

In this research, we investigated the electrochemical behaviors of conducting poly(thionine) (PTH) on glassy carbon electrode (GCE) for the interference-free detection of dopamine (DA). The PTH films on GCE were prepared in two methods: direct potential sweeping (single step, PTH-S), or a constant potential oxidation of GCE followed by potential sweeping (double step, PTH-D). Our electrochemical investigation revealed that the simple variation of the electropolymerization conditions dramatically changed the PTH formation mechanism without altering the chemical structure of the polymers as well as the catalytic activity for the oxidation of DA in the presence of ascorbic acid (AA) and uric acid (UA). The PTH-D exhibited higher sensitivity for the detection of DA compared to the PTH-S, which can be attributed to the higher accumulated surface charge/polymer amount on the PTH-D films compared to the PTH-S. The PTH-S could easily suppress the signals of AA and UA in the presence of DA, while, the PTH-D could easily separate the oxidation signals of AA, DA, and UA with higher sensitivity. These interesting features will help the researchers to control the sensitivity for DA oxidation and other analytes by using PTH and other conducting polymers.

Tuning the Surface Properties of Polypyrrole Films for Modulating Bacterial Adhesion

Tuning the physical–chemical properties of polypyrrole (PPy) opens up potentially exciting new applications, especially in the area of bacterial adhesion. Polypyrrole is electrochemically synthesized under various conditions and the physical properties of the films and their effects on bacterial adhesion are characterized. Five types of dopants—chloride (Cl), perchlorate (ClO4), p‐toluene‐sulfonate (ToS), dodecylbenzene sulfonate (DBS), and poly sodium styrene sulfonate (PSS)—are used to fabricate PPy films at two different constant potentials (0.500 and 0.850 V) with and without Fe3+. Their thickness, roughness, and wettability are measured. The adhesion tendency of Escherichia coli, as a model bacterium, to the four polymers is studied. E. coli shows greater adhesion tendency to the hydrophobic, rough surface of PPy‐DBS, and less adhesion tendency to the smooth and hydrophilic surface of PPy‐PSS. The results facilitate the choice of appropriate electropolymerization conditions to modulate bacterial adhesion. image

Polypyrrole Microcontainers: Electrochemical Synthesis and Characterization

We present electrochemically controlled synthesis of polypyrrole microcontainers on electrogenerated hydrogen gas bubbles acting as a template. We performed structural characterization of the obtained microcontainers to gain insight into the growth kinetics of the polypyrrole shell. Experimental results showed that surfactant-mediated polymerization of pyrrole at the hydrogen microbubble surface under controlled electrochemical biasing led to the synthesis of various micro/nanostructures. Dependent upon the electrochemical conditions, such as the number of redox cycles and scan rate, the containers with spherical globules and bowl-like structures, which become lantern-like with increasing the number of cycles, are formed, as revealed by scanning electron microscopy. Their diameter can range between 40 and 200 μm, and wall thickness can be varied from 2 to 70 μm, depending upon the electropolymerization conditions.

A novel electropolymerized fluorescent film probe for TNT based on electro-active conjugated copolymer

A novel electro-active conjugated copolymer (PFPCz) has been designed, synthesized and used as the precursor of electropolymerization (EP) directly. By optimizing the EP condition, the PFPCz EP films have been prepared and displayed high fluorescent sensitivity to TNT, whose fluorescent intensity could be quenched 68.6% exposed to TNT (50μM) in aqueous medium. These results suggest PFPCz EP film a promising candidate for TNT detection. Furthermore, this work provides not only a new precursor to EP but also a promising fluorescence film sensor candidate.

Influence of electropolymerization conditions on the morphological and electrical properties of PEDOT film

ABSTRACT In this work the effects of electropolymerization conditions on the morphological properties and conductivity of poly(3,4-ethylenedioxythiophene) (PEDOT) film have been studied. PEDOT films were electrochemically synthesized in a one step process from acetonitrile solution containing 3,4-ethylenedioxythiophene (EDOT) and lithium perchlorate. Based on atomic force microscopy, scanning electron microscopy, cyclic voltammetry and impedance spectroscopy measurements, the morphological properties such as the of structure, double layer capacitance and thus the polymer surface area have been determined. It was shown that depending on the deposition conditions applied, different structures and film surface area could be obtained. Impedance measurements performed during deposition showed different resistance behavior and conductivity. The relationship between structure and conductivity of PEDOT film obtained under different deposition conditions has been discussed.

Influence of electrochemical copolymerization conditions of 3‐methylthiophene and biphenyl on the morphology and nanomechanical properties of the films

ABSTRACTThe aim of this work is to synthesize novel 3‐methylthiophene (3MTh)/biphenyl (Biph) copolymer films by electropolymerization and study their mechanical properties through nanoindentation. The morphology, the chemical structure as well as the electrical conductivity of the copolymer films depended strongly on the electropolymerization conditions. It was found that the polymer deposition follow an instantaneous, two‐dimensional nucleation and growth mechanism leading to homogenous films. The copolymer films had higher Young modulus and nanohardness than poly(3‐methylthiophene) (3PMTh), indicating that the incorporation of Biph units within the P3MTh chain leads to a more densely packed structure and a more brittle polymer. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42575.

Electropolymerized Eugenol‐MWNT‐Based Electrode for Voltammetric Evaluation of Wine Antioxidant Capacity

AbstractEugenol electropolymerization conditions on multiwalled carbon nanotube based glassy carbon electrode (MWNT/GCE) have been found. The polyeugenol/MWNT/GCE shows reversible redox steps of o‐quinone fragment in acidic media. Natural phenolic antioxidants are oxidized on polyeugenol/MWNT/GCE at 0.52 V excluding resveratrol (0.62 V). Differential pulse voltammetry on polyeugenol/MWNT/GCE was applied for the evaluation of wine antioxidant capacity (AOC). The AOC was expressed in catechin equivalents per 1 L of wine. The linear dynamic range is 1.00–250 µM with LOD and LOQ of 0.21 and 0.71 µM of catechin, respectively. Positive correlations for AOC with antioxidant activity (r=0.9840) and total phenolics content (r=0.9944) were observed.

Noncovalently functionalized monolayer graphene for sensitivity enhancement of surface plasmon resonance immunosensors.

A highly efficient surface plasmon resonance (SPR) immunosensor is described using a functionalized single graphene layer on a thin gold film. The aim of this approach was two-fold: first, to amplify the SPR signal by growing graphene through chemical vapor deposition and, second, to control the immobilization of biotinylated cholera toxin antigen on copper coordinated nitrilotriacetic acid (NTA) using graphene as an ultrathin layer. The NTA groups were attached to graphene via pyrene derivatives implying π-π interactions. With this setup, an immunosensor for the specific antibody anticholera toxin with a detection limit of 4 pg mL(-1) was obtained. In parallel, NTA polypyrrole films of different thicknesses were electrogenerated on the gold sensing platform where the optimal electropolymerization conditions were determined. For this optimized polypyrrole-NTA setup, the simple presence of a graphene layer between the gold and polymer film led to a significant increase of the SPR signal.

Electrochemical preparation and characterization of polypyrrole/stainless steel electrodes decorated with gold nanoparticles.

The electrosynthesis and characterization of polypyrrole(PPy)/stainless steel electrodes decorated with gold nanoparticles and the performance of the composite electrode for sensing applications is described. PPy films were grown in potassium perchlorate and sodium salicylate solutions under comparable electropolymerization conditions. Polymer films prepared in the presence of perchlorate ions exhibited worm-like structures, whereas columnar structures were obtained in salicylate-containing solutions. Voltammetric response of PPy films prepared in salicylate solutions was more reversible. PPy films were decorated with gold nanoparticles obtained by a double step potentiostatic electrodeposition routine that allowed fine control of deposit characteristics. Analysis of deposits was performed by means of SEM and confocal Raman spectroscopy. The electrocatalytic activity of the Au/PPy electrodes was assessed for the electro-oxidation of hydrazine and hydroxylamine. Results showed a successful optimization of the route of synthesis that rendered nanocomposite electrode materials with promising applications in electrochemical sensing.