A screen-printed carbon electrode modified with a chitosan-based film for in situ heavy metal ions measurement

SEM images and FTIR data of the working electrode surface showed that Mn+ ions were adsorbed on chitosan (Chit) and crosslinked chitosan-carbon nanotube (Chit-CNT) films. XPS revealed that chelation of Mn+ ions with the –NH2/–OH groups from chitosan, –COOH group from carbon nanotubes, and aqua ligands represents a possible structure of the active Mn+ species in the Chit-based film. The electrochemical behaviors of the Chit-based film modified screen-printed carbon electrode (SPCE) were characterized for individual and simultaneous detection of Cu2+, Pb2+, Hg2+, Zn2+, Cd2+, and As3+ ions. For individual detection, the concentration range was 0.50–3.00 ppm with a detection limit of 0.4 ppm for Cu2+; 1.0–4.0 ppm with a detection limit of 0.5 ppm for Pb2+; 1.0–5.0 ppm with a detection limit of 0.8 ppm for Hg2+. For simultaneous detection, the lab chip sensor was successfully used to determine the concentrations of Pb2+, Cu2+, Hg2+, and As3+ ions simultaneously

OPTIMIZATION OF SCREEN PRINTED REFERENCE ELECTRODE BASED ON CHARGE BALANCE AND POLY (BUTYL ACRYLATE) PHOTOCURABLE MEBRANE

This research focus on transforming the traditional design of reference electrode into all-solid-state reference electrode front-end using Ag/AgCl screen- printed electrodes. By replacing the internal reference solution of a traditional reference electrode by a solid photocurable membrane, an all-solid-state reference electrode can be achieved. The solid-state screen-printed reference electrode was designed using a photocurable acrylic film containing immobilized sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB) and trimethylocthylammonium chloride (TOMA-Cl). An optimum ratio of NaTFPB:TOMA-Cl = 1:1 produced a stable reference electrode. In the anions interference studies, all anions i.e. NO3-, Cl-, Br- and SO42- does not give effect to the SPRE except perchlorate anions. The all-solid-state reference electrodes was applied to the detection of potassium ions and ammonium ions. Validation of the all-screen-printed reference electrode was performed with reference electrode standard gel type. The validation results showed that all-solid-state screen-printed reference electrode demonstrated performance that was comparable to standard reference electrode

OPTIMIZATION OF SCREEN PRINTED REFERENCE ELECTRODE BASED ON CHARGE BALANCE AND POLY (BUTYL ACRYLATE) PHOTOCURABLE MEBRANE

This research focus on transforming the traditional design of reference electrode into all-solid-state reference electrode front-end using Ag/AgCl screen- printed electrodes. By replacing the internal reference solution of a traditional reference electrode by a solid photocurable membrane, an all-solid-state reference electrode can be achieved. The solid-state screen-printed reference electrode was designed using a photocurable acrylic film containing immobilized sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB) and trimethylocthylammonium chloride (TOMA-Cl). An optimum ratio of NaTFPB:TOMA-Cl = 1:1 produced a stable reference electrode. In the anions interference studies, all anions i.e. NO3-, Cl-, Br- and SO42- does not give effect to the SPRE except perchlorate anions. The all-solid-state reference electrodes was applied to the detection of potassium ions  and ammonium ions. Validation of the all-screen-printed reference electrode was performed with reference electrode standard gel type. The validation results showed that all-solid-state screen-printed reference electrode demonstrated performance that was comparable to standard reference electrode.

Comparative electrochemical study on the effects of heterogeneous carbon nanostructured-materials on the properties of screen-printed carbon electrodes towards Riboflavin determination

In this work, the influence of graphene nanoribbons (GNs), graphene nanoplatelets (GNPls), multi-walled carbon nanotubes (MWCNTs) and graphene oxide (GO) as a modifier on the properties of screen-printed carbon electrodes towards electrochemical determination of riboflavin (VB2) is investigated. Additionally, ionic liquid (IL, 1-Butyl-2,3-dimethylimidazolium tetra fluoroborate), iron(II) phthalocyanine (FePc) and Nafion were added into the modifier suspensions and further tested for their electro-catalytic effect. Their performance as modifier is compared to unmodified screen-printed carbon electrodes (SPCE). Unmodified screen-printed electrodes are printed in laboratory onto the ceramic substrate using carbon ink. Modified electrodes are prepared by drop-casting modifier suspension onto the active surface area of SPCE. The three-electrode system is used, consisted of a glass vessel equipped with the screen-printed carbon electrode as a working electrode (unmodified or modified), the reference electrode an Ag/AgCl electrode (3M KCl) and the auxiliary electrode a platinum wire. The studies are done using cyclic voltammetry (CV) in Britton-Robinson buffer solution (BRBS, pH 2.0) as a supporting electrolyte at scan rate of 50 mV/s. The preliminary results show that in comparison to modified screen-printed carbon electrodes, unmodified electrodes give increased current signals where the redox reaction of riboflavin occurs. Unmodified screen-printed electrodes usually give high responses due to the more hydrophilic surface and are very easy to handle, with excellent sensitivity and as low cost electro-analytical tools. Nevertheless, the results seem promising that the the modifier free sensor can be applied for the quick quantification of riboflavin

Selenocystine modified screen-printed electrode as an alternative sensor for the voltammetric determination of metal ions

A novel selenium based screen-printed electrode was developed based on the immobilization of selenocystine on aryl diazonium salt monolayers anchored to a carbon-nanofiber screen-printed electrode support (SeCyst- SPCNFE). SeCyst-SPCNFE was analytically compared to a screen-printed carbon nanofiber electrode modified with L-Cystine (Cyst-SPCNFE) for the determination of Pb(II) and Cd(II) by stripping voltammetric techniques. Their analytical performance suggests that SeCyst-SPCNFE could be a much better alternative for metal ion determination at trace levels than Cyst-SPCNFE. The proposed electrode was successfully applied for the simultaneous voltammetric determination of trace Pb(II) and Cd(II) in a wastewater reference material with a very high reproducibility (3.2%) and good trueness (2.6%)

Effect of sensitization on the electrochemical properties of nanostructured NiO

Screen-printed NiO electrodes were sensitized with 11 different dyes and the respective electrochemical properties were analyzed in a three-electrode cell with the techniques of cyclic voltammetry and electrochemical impedance spectroscopy. The dye sensitizers of NiO were organic molecules of different types (e.g., squaraines, coumarins, and derivatives of triphenyl-amines and erythrosine B), which were previously employed as sensitizers of the same oxide in dye-sensitized solar cells of p-type (p-DSCs). Depending on the nature of the sensitizer, diverse types of interactions occurred between the immobilized sensitizer and the screen-printed NiO electrode at rest and under polarization. The impedance data recorded at open circuit potential were interpreted in terms of two different equivalent circuits, depending on the eventual presence of the dye sensitizer on the mesoporous electrode. The fitting parameter of the charge transfer resistance through the electrode/electrolyte interface varied in accordance to the differences of the passivation action exerted by the various dyes against the electrochemical oxidation of NiO. Moreover, it has been observed that the resistive term RCT associated with the process of dark electron transfer between the dye and NiO substrate is strictly correlated to the overall efficiency of the photoconversion () of the corresponding p-DSC, which employs the same dye-sensitized electrode as photocathode

New Directions in Screen Printing and Related Fabrication Processes

This thesis reports the development of screen printed electrodes and associated fabrication processes in order to develop and understand new electrochemical based sensors. There are three main sections to this thesis. In the first part, an overview of sensors, in particular electrochemical sensors, that are commercially available and their current problems and limitations with conventional electrodes and electrode materials is discussed. Second, an introduction into screen printing and their advantages are given. The full process by which these next generation electrodes are manufactured is thoroughly described followed by examples of screen printed-electrodes and their powerful application as well as their low detection limits which compare well to existing literature on the market. The first example of a copper (II) oxide screen-printed electrode is reported, which is characterised with microscopy and its efficiency for the electrochemical sensing of glucose, maltose, sucrose and fructose is explored. It is shown that the non-enzymatic electrochemical sensing of glucose with cyclic voltammetry and amperometry is possible with low micro-molar up to milli-molar glucose readily detectable, which compares competitively with nano-catalyst modified electrodes. An additional benefit of this approach is that metal oxides with known oxidation states can be incorporated into the screen-printed electrodes allowing one to identify exactly the origin of the observed electro-catalytic response which is difficult when utilising metal oxide modified electrodes formed via electro-deposition techniques which result in a mixture of metal oxides/oxidation states. These next generation screen printed electrochemical sensing platforms provide a simplification offering a novel fabrication route for the mass production of electro-catalytic sensors for Analytical and Forensic applications. Other examples such as, bespoke screen printed electrodes which can be used as a template to produce randomly dispersed electro-catalytic micro-domains for analytical sensing purposes, are also shown to further demonstrate the applications and utility of screen printed electrodes. The final section focuses on electrode design. It is demonstrated that the electron transfer properties of disposable screen-printed electrodes can be readily tailored via the introduction of a polymeric formulation into the ink used in their fabrication. This approach allows the role of the binder on the underpinning electrochemical properties to be explored and quantified for the first time, allowing the electrochemical reactivity of the screen-printed electrodes to be tailored from that of edge plane-like to basal plane-like reactivity of highly ordered pyrolytic graphite. Building on this fundamental study of the origin of electron transfer at these novel electrodes, the first example of “Cosmetic Electrochemistry” is demonstrated where a commercially available cosmetic product, a deodorant, can be used to confer microelectrode behaviour on a macroelectrode. Proof-of-concept is shown that a graphite screen-printed electrode can be sprayed with an off-the-shelf cosmetic product and within seconds is ready to use. The polymer contained within the cosmetic product partially blocks the graphite screen-printed electrode surface leaving the underlying graphite electrode exposed in the form of graphite micron-sized sites which are randomly distributed across the electrode surface. The creation of microdomain sites enhance mass transport of the target analyte and it is shown that the electroanalytical performance of the cosmetically modified electrode, via the cathodic stripping of lead, could achieve a similar performance to current state-of-the-art methodologies. Further examples are also reported with the introduction of plaster-trodes where a commercially available plaster is electrolytically modified with electrocatalytic material and is used to detect various alcohol

New approaches to antimony film screen-printed electrodes using carbon-based nanomaterials substrates

Three different commercial carbon nanomaterial-modified screen-printed electrodes based on graphene, carbon nanotubes and carbon nanofibers were pioneeringly tested as electrode platforms for the plating with Sb film. They were microscopically and analytically compared to each other and to the most conventional unmodified carbon screen-printed electrode (SPCE). The obtained detection and quantification limits suggest that the in-situ antimony film electrode prepared from carbon nanofibers modified screen-printed electrode (SbSPCE-CNF) produces a better analytical performance as compared to the classical SPCE modified with antimony for Pb(II) and Cd(II) determination, approving its appropriateness for measuring low μg L(-1) levels of the considered metals. In-situ SbSPCE-CNF was successfully used for the simultaneous determination of Pb(II) and Cd(II) ions, by means of differential pulse anodic stripping voltammetry, in a certified reference estuarine water sample with a very high reproducibility and good trueness

Nanoparticles modified screen printed electrode for electrochemical determination of COD

The Chemical Oxygen Demand (COD) is a parameter widely used to determine organic pollutants in water and is defined as the number of oxygen equivalents necessary to oxidize the organic compounds. The standard method for COD measurement (the dichromate titration) suffers from several inherent drawbacks such as the long time of the process and the consumption of toxic chemicals. Hence, interest is growing towards those methods employing electrochemical oxidation of organic compounds, as they allow to dispense with toxic reagents and above all to perform a continuous determination. In this work a new electrochemical method for COD measurement has been developed based on direct oxidation of organic molecules on suitably modified electrodic surfaces. In particular, we have developed various sensors based on modified working electrode surfaces obtained by electrodepositing copper and/or nickel oxide nanoparticles onto several commercial screen printed electrodes. Glucose was used as the standard compound for COD measurements: C6H12O6 + 6O2 → 6CO2 + 6H2O The metallic nanoparticles catalyze the oxidation of the glucose, as well as of different organic pollutants, and make the detection possible at relatively low potential, also in presence of chloride as interferent. The analytical parameters were optimized and the results obtained highlight how the electrodeposition of different metallic nanoparticles onto several screen printed electrode surfaces can influence the selectivity and sensitivity towards the COD detection in real matrices, via electrochemical method. The results were compared with those obtained by the standard method and showed a good agreement. These findings provide an interesting strategy to obtain a simple, cheap, portable and eventually continuous sensor for COD measurement

A Screen Printed Electrode for the Characterization of Cardiac Tissues

A screen-printed electrode (SPE), intended to be used as part of a cardiac mapping system, was fabricated and evaluated to determine if SPEs are a suitable alternative to current electrodes. The SPEs were designed in AutoCAD and screen-printed using silver conductor ink and an insulating paste. Measurements were taken during electrode development to determine how well the design translated to the final printed product. The efficacy of the insulating material used, and the affects of print speed on print quality were also evaluated. Finally, the performance of the SPEs was studied through a stimulating and recording model, as well as electrochemical analysis. The electrochemical analysis inluded modifying the silver electrode to produce a silver, silver chloride electrode. The results showed promise and provided insight on where efforts should be focused to advance the development of SPEs. Overall it was concluded that SPEs would be well-suited for mapping cardiac electrical activity