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Fundamentals of Screen-Printing Electrochemical Architectures
Abstract
This chapter introduces the background theory on the screen-printing process.
... The scope of this case is limited to variation minimization in the screen-printing stage of the manufacturing process. Screen-printing is one of the most versatile, durable, economical and high-quality graphic resolution processes having a variety of commercial and retail applications (Foster et al. 2016). An important factor that makes screen-printing so popular is the fact that it allows one to use a wide variety of printing materials like plastic labels, powder coated metal plates, resistor or circuit boards, cylindrical containers and so on as a surface for printing (Phillips et al. 2014). ...
... Due to this pressure, the screen comes in contact with the power coated plate which leads to the printing of the desired content. In the last step, the screen is carefully lifted off the powder coated plate to avoid any spill overs of ink (shown in Fig. 4) (Foster et al. 2016). The output of this stage is a screen-printed powder coated plate that goes to the fitting stage (Fig. 5). ...
Six Sigma is a widely practiced, systematic, and structured methodology embedded with statistical methods and managerial philosophies for quality improvement by large firms along with small firms in the industrialized economies. Application of Six Sigma in Micro Small Medium Enterprises (MSMEs) in developing economies is limited due to several barriers these firms face. In academic literature, there is unavailability of sufficient evidence of successful implementation of the practice in these firms to encourage and provide a roadmap for its implementation. Thus, there is a need for studies that presents frameworks with illustrative case studies demonstrating the implementation of Six Sigma in MSMEs. In the present times, MSME firms in developing economies are facing competition from world leaders, and thus it has become essential for them to focus on the quality of their manufacturing products and at the same time being productive and efficient. Moreover, in the literature, it is observed that the potential of operations research (OR) methods is not sufficiently explored in Six Sigma studies. OR-based methods and tools should be integrated into Six Sigma implementation frameworks as these methods expand the application portfolio and tackle some of the barriers that limit the application of Six Sigma in small-scale firms. In this paper, a Six Sigma implementation framework for an MSME organization is developed incorporating Multi Criteria Decision Making (MCDM) tool Decision-Making Trial and Evaluation Laboratory, apart from other conventional tools like cause and effect analysis, benefit effort analysis, Pareto analysis, control charts, etc. The proposed framework is illustrated in detail with the help of a real-life case study of an MSME in India. The results obtained after the implementation of this framework signify that the incorporation of MCDM in Six Sigma lead to a significant improvement in the sigma level of the firm despite of unavailability of sufficient resources.
... Various methods can be used to evaluate these properties of SPE [13,14,15]. In this study, the CV The anodic and cathodic peaks on the CV curve also undergo more shifting when the scan rate is varied [16], resulting in less sensitive analytical signals on these electrodes. ...
Three types of conductive inks, including Ceres, Acheson carbon inks, and Ag/AgCl ink, were utilized to fabricate screen-printed electrodes (SPEs) on a 0.4 mm thick polyethylene terephthalate substrate using a screen-printing technique. To enhance the electrical conductivity, the printed electrodes were cured at 80°C for 90 minutes. The basic electrochemical properties of the self-made SPEs using these conductive inks were determined, evaluated, and compared with commercial SPEs from Metrohm. Although the electroactive surface areas of the self-made SPEs were not significantly different from those of the commercial SPEs, the heterogeneous electron transfer rates on the surfaces of self-made SPEs using Ceres and Acheson inks were inferior to those of the commercial SPEs. However, after pre-condition by applying a potential of +1.2 V for 180 s in a 2 M Na2CO3 solution, the electrochemical properties of the self-made SPEs, including the active surface areas and heterogeneous electron transfer rates, were significantly improved and became better than those of the commercial SPEs.
... Additionally, for particle synthesis requiring higher kinetic energy, ball diameters in the range of a few tens of millimetres are employed [12]. Conversely, for producing fine powders (characterized by a homogeneous particle size distribution and a diameter below 5 µm suitable for screen printing) [25], balls smaller than 10 mm are utilized [26]. The typical ratio of balls to powder is 10:1, though a higher ratio of 20:1 can be employed to enhance milling efficiency (by increasing high-energy collisions), or a lower ratio can be used to decrease it [27]. ...
This paper addresses the polymer conductive paste formulation based on modified silver oxide (Ag 2 O) particles. This paste is distinguished by the self-reduction of Ag 2 O particles to conductive Ag through a thermal process. It is suitable for the fabrication of conductive flexible structures. In addition to detailing the paste’s recipe, the paper provides a comparison and assesses the effect of modifying Ag 2 O particles through 5 hours of milling, comparing them with large-grain particles in their original state, focusing on screen printing technology. The investigation delves into the impact of milling on particle size and distribution using as well as to verify the purity of the homogeneously created powder. Samples are manufactured using an Ag 2 O -based paste, screen-printed on a flexible PET Mylar® A substrate, 50 µm thick. The printed patterns are cured at 120°C to 160°C for 10 minutes while monitoring the effect of vacuum and number of printed layers on sheet resistance. Sheet resistance measurements are conducted using a 4-point probe test method. The results suggest that wet planetary ball milling is a suitable technique for modifying Ag 2 O particles, rendering them suitable to produce polymer conductive paste. In addition, milling produces only silver oxide fine powder particles, according to XRD patterns.
... Inks or pastes are commonly made of carbon (e.g., carbon black, graphite, etc.) or metallic forms such as gold, silver, and platinum. 10 Various carbon-based materials, including graphene and its derivatives, 11−14 are often used as WE and CE because they possess exceptional features in electrochemistry including high conductivity and low background current. Moreover, the inks allow plenty of simple surface modifications such as metal depositions and composites self-assembling, which promote the sensitivity and selectivity of detection while providing simplicity of fabrication and importantly contributing to lower prices. ...
Paper-based electrochemical devices (PEDs) have emerged as versatile platforms that bridge analytical chemistry and materials science, demonstrating advantages of portability, cost-effectiveness, and environmental sustainability. This study investigates the integration of a graphene pseudoreference electrode (GPRE) into a PED, and it exhibits potential advantages over the traditional Ag/AgCl pseudoreference electrode (PRE). In addition, the electrochemical properties and stability of GPRE are compared with those of the traditional Ag/AgCl PRE. The results demonstrate that GPRE exhibits a stable and reproducible potential during electrochemical measurement throughout 180 days, demonstrating its suitability as an alternative to an expensive metal PRE. Furthermore, a GPRE-incorporated paper-based device is designed and evaluated for use in the electrochemical detection of cadmium (Cd) and lead (Pb) using an in situ bismuth-modified electrode. The GPRE-incorporated PED exhibited good analytical performance, with a low limit of detection of 0.69 and 5.77 ng mL–1 and electrochemical sensitivities of 70.16 and 38.34 μA·mL·μg–¹·cm–2 for Cd(II) and Pb(II), respectively. More than 99.9% accuracy of the sensor was obtained for both ions with respect to conventional inductively coupled plasma-mass spectrometry. The results highlight the effectiveness and suitability of the GPRE-incorporated PED as a sensor for various applications, such as environmental monitoring, food quality control, and medical diagnostics.
... The present review discovered a limitation of the developed electrochemical aptasensors for Salmonella detection, namely, that they are mostly constructed using conventional electrodes (13 studies) rather than SPEs (two studies). This finding demonstrates the need for more studies using SPEs to detect Salmonella as it offers flexibility in electrode design, material compatibility and modifications, low production cost, the possibility of large-scale production, and connection to portable instrumentation [90][91][92]. Due to their miniaturized size, SPEs can significantly improve detection systems in diagnostic applications since the sample volume and reagent can be reduced to microliters, and low-power analysis is needed. The miniaturized size, versatility, and portability make the SPEs highly possible for on-site testing and monitoring of real samples [93,94]. ...
The development of rapid, accurate, and efficient detection methods for Salmonella can significantly control the outbreak of salmonellosis that threatens global public health. Despite the high sensitivity and specificity of the microbiological, nucleic-acid, and immunological-based methods, they are impractical for detecting samples outside of the laboratory due to the requirement for skilled individuals and sophisticated bench-top equipment. Ideally, an electrochemical biosensor could overcome the limitations of these detection methods since it offers simplicity for the detection process, on-site quantitative analysis, rapid detection time, high sensitivity, and portability. The present scoping review aims to assess the current trends in electrochemical aptasensors to detect and quantify Salmonella. This review was conducted according to the latest Preferred Reporting Items for Systematic review and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A literature search was performed using aptamer and Salmonella keywords in three databases: PubMed, Scopus, and Springer. Studies on electrochemical aptasensors for detecting Salmonella published between January 2014 and January 2022 were retrieved. Of the 787 studies recorded in the search, 29 studies were screened for eligibility, and 15 studies that met the inclusion criteria were retrieved for this review. Information on the Salmonella serovars, targets, samples, sensor specification, platform technologies for fabrication, electrochemical detection methods, limit of detection (LoD), and detection time was discussed to evaluate the effectiveness and limitations of the developed electrochemical aptasensor platform for the detection of Salmonella. The reported electrochemical aptasensors were mainly developed to detect Salmonella enterica Typhimurium in chicken meat samples. Most of the developed electrochemical aptasensors were fabricated using conventional electrodes (13 studies) rather than screen-printed electrodes (SPEs) (two studies). The developed aptasensors showed LoD ranges from 550 CFU/mL to as low as 1 CFU/mL within 5 min to 240 min of detection time. The promising detection performance of the electrochemical aptasensor highlights its potential as an excellent alternative to the existing detection methods. Nonetheless, more research is required to determine the sensitivity and specificity of the electrochemical sensing platform for Salmonella detection, particularly in human clinical samples, to enable their future use in clinical practice.
... The mesh is usually built on a metal or wooden frame able to hold the pressure from the mesh and printing tension. For further information on how to choose the right mesh for screen-printing for electrochemical applications, please read Foster et al. 29 3) What squeegee to use? The squeegee pushes the ink through the mesh at high pressure, and sometimes speed, creating a controlled flow of ink upon the substrate. ...
Biomarkers play an important and irrefutable role in the screening, diagnosis, monitoring and treatment of a wide variety of human diseases. As these biomarkers inevitably feature more and more prominently in the patient care pathway, there is a growing need for technologies that can provide rapid, accurate and sensitive test results at low cost. In this review we showcase, discuss, evaluate, and explain some recent advances in screen-printed electrodes (SPEs) and the modification strategies used for the electrochemical biosensing of some of the important, established biomarkers related to 1) cardiac injury, 2) cancer diagnostics and 3) acute inflammatory conditions, three areas of medicine currently associated with significant healthcare costs. Electroanalytical biosensors are proven to be an attractive alternative to benchtop conventional testing techniques, saving space, whilst allowing enhanced portability, a reduction in testing costs and test turnaround times. Electrochemical-based point-of-care (POC) testing technologies are still in the early stages of commercial, and hence clinical, uptake. Due to the design flexibility, low-cost and reliability of SPEs we expect to see a significant acceleration in the development of SPE-based electrochemical approaches to POC in these areas of medicine. Rapid, simultaneous detection of multiple important analytes in a single test at the point of patient's care will undoubtedly be the driver for uptake into clinical settings; their potential for impact is discussed herein.
... Two-dimensional (2D) coatings and printing methods have been long used as manufacturing solutions for carbon-based solventmodifier mixes deposition since the 1990s. Large-scale production techniques such as drop-casting, pad-printing, spin-coating, dipcoating, screen-printing, spray-coating and roll-to-roll (R2R) are all methods to coat, deposit or bond materials onto a surface and offering a reproducible and scalable solution with reduced fabrication costs towards decentralized analysis (Bard, 1983;García-Miranda Ferrari et al., 2021b;Banks et al., 2016;Willmann et al., 2014;Bae et al., 2010;Hösel et al., 2013). R2R allows the industrial manufacture of low-cost sensor devices by using wet deposition methods coupled with gravure, flexography, wire-bar, rotary screenprinting, slot-die and/or knife-over-edge technologies to deposit dispersions of functional materials (Assaifan et al., 2016;Bariya et al., 2018;Reddy et al., 2011;Cagnani et al., 2020;Abbel et al., 2018). ...
Carbon materials, from their traditional forms such as graphite or carbon black, to the more novel forms such as carbon nanotubes (CNTs), graphene, graphene oxide (GO), and their variants have been used extensively transducer elements for sensing platforms. In this chapter, we explore the variety of carbon shapes and nanomaterials, their synthesis methods and their applications as the basis of electrochemical sensors. These include different carbon allotropes utilized within the literature but also recent advances in manufacturing solutions such as 2D printing and additive manufacturing (3D printing) of graphitic structures for their applications to sensors.
... Catalyst supports are therefore key to the current output of the electrolyser and its longevity. [160][161][162][163][164]. However, carbon based supports are not suitable for application within the anodic side of electrolysers given that they suffer fast corrosion under high oxidative potentials. ...
The potential for generating green hydrogen by electrolysis (water splitting) has resulted in a substantial amount of literature focusing on lowering the current production cost of hydrogen. A significant contributor to this high cost is the requirement for precious metals (namely Pt and Ir/Ru (oxides)) to catalyse the two main reactions involved in electrolysis: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein we overview the current literature of non-precious metal HER and OER catalysts capable of efficient water splitting within a polymer electrolyte membrane (PEM) electrolyser, recording the activity and stability of each catalyst and allowing for direct comparison to be made. Additionally, we highlight the inapplicability of catalyst stability testing in many academic studies for commercial electrolyser applications and propose a universal stability-testing regime for HER and OER catalysts that more accurately mimics the conditions within an operating electrolyser.
... Moreover, the In 2 O 3 /SnO 2 films were developed using hydrothermal synthesis of materials and deposition of films via screen printing technology [123]. The screen printing technology is excellent to print materials on desired surface with desired design [124,125]. Nonetheless, the material to be deposited should meet the criteria of printing on the desired substrate. In addition, the screen printing follows complex steps with a good facility to back up. ...
The presence of H2S is an incisive indicator to assess the quality of indoor and/or outdoor air. A number of metal oxide sensors have been developed to measure the concentration levels of H2S in the environmental systems. Among such sensors, In2O3-based sensors are one of the most promising options with the enhanced potential to generate highly sensitive and specific signals in diverse physical/chemical forms (such as pristine, metal-doped/loaded, and composite). Their enhanced sensing performance has been ascribed to to many excellent properties (e.g., chemisorption capabilities of oxygen, direct interactions with H2S, synergetic effect with other materials, generation of sensing signals (at ambient conditions), and capabilities to interact with hydrolyzed form of H2S). It is also noted that chemoresistive sensing of In2O3-materials is a highly preferable option in terms of the strong interactivity with H2S. Herein, we have reviewed the potential of In2O3-based materials (e.g., in pure, metal-doped/loaded, and composite form) for the sensing of H2S gas with the special emphasis on operation temperature conditions (e.g., at and above room temperature). Discussion is also extended to the H2S sensing mechanisms and synthesis procedures with the future prospects on this technology. Moreover, a careful evaluation has been made to select the best available option for the In2O3-based sensing method based on the evaluation on their performance on parallel basis.
... This procedure can be applied several times in order to obtain more layers of the material onto the substrate, either conductive ink or dielectric material. Further details of the procedure were reviewed elsewhere [7]. ...
Recent progress in the field of electroanalysis with metal nanoparticle (NP)-based screen-printed electrodes (SPEs) is discussed, focusing on the methods employed to perform the electrode surface functionalization, and the final application achieved with different types of metallic NPs. The ink mixing approach, electrochemical deposition, and drop casting are the usual methodologies used for SPEs’ modification purposes to obtain nanoparticulated sensing phases with suitable tailor-made functionalities. Among these, applications on inorganic and organic molecule sensing with several NPs of transition metals, bimetallic alloys, and metal oxides should be highlighted.
... A larger mesh size and a smaller wire diameter result in a minimised dot size, as shown in Table 2. The mesh openings are defined by the maximum paste particle size and should be 3 times larger (Foster et al., 2016). The positions of the Al dots under the worst case are at the cross-centre of Ju, et al. ...
Excellent surface passivation with a localised back surface field (LBSF) formation is the key parameter for increasing the efficiency of PERC cells. In this regard, the additional use of rear multi-stack passivation layers (Al 2 O 3 /SiN X) and local laser opening of the LBSF increase the production cost. In addition, these stacked layers and the laser process require additional tools, which creates a compatibility barrier for studies conducted in small-scale industrial laboratories. Rear multi-stack passivation layers (Al 2 O 3 /SiN X) and a front SiN X anti-reflection coating (ARC) layer were changed using a one-step thermal oxidation process. The emitter doping and thermal SiO 2 oxidation layer were optimised for the front ARC and rear passivation layer. The formation mechanism of the LBSF was investigated by varying the firing conditions and the Al dot size. Scanning electron microscopy images confirmed the thickness of the LBSF. The fabricated cell exhibited an efficiency of 20.05% with a fill factor (FF) of 78%, a current density (J SC) of 39.3 mA/cm 2 , and an open-circuit voltage (V OC) of 655 mV under a spectral condition of AM 1.5G. A significant improvement in the recombination current density (J 0) (314 fA/cm 2) was achieved as compared with the fire-through full BSF solar-cell process (933 fA/cm 2).
... Paper Blue serves as the substrate to develop sustainable glucose strips, combining printed technologies: wax-and screen-printing. The former is a green approach to define the testing area [25], the latter is used to print the sensing strips on the wax-patterned support [26], as shown in Fig. 3. ...
Nowadays, environmentally friendly synthesis pathways for preserving the environment and minimizing waste are strongly required. Herein, we propose filter paper as a convenient scaffold for chemical reactions. To demonstrate this novel approach, Prussian Blue Nanoparticles (PBNPs) were synthesized on filter paper by utilizing few μL of its precursors without external inputs, i.e. pH, voltage, reducing agents, and without producing waste as well. The functional paper, named “Paper Blue”, is successfully applied in the sensing field, exploiting the reduction of hydrogen peroxide at low applied potential. The eco-designed “Paper Blue” was combined with wax- and screen-printing to manufacture a reagentless electrochemical point-of-care device for diabetes self-monitoring, by using glucose oxidase as the biological recognition element. Blood glucose was linearly detected for a wide concentration range up to 25 mM (450 mg/dL), demonstrating its suitability for management of diabetes and glucose-related diseases. The Paper Blue-based biosensor demonstrated a correlation coefficient of 0.987 with commercial glucose strips (Bayer Contour XT). The achieved results demonstrated the effectiveness of this approach, which is also extendible to other (bio)systems to be applied in catalysis, remediation, and diagnostics.
Detecting urea is crucial for diagnosing related health conditions and ensuring timely medical intervention. The addition of machine learning (ML) technologies has completely changed the field of biochemical sensing, providing enhanced accuracy and reliability. In the present work, an ML-assisted screen-printed, flexible, electrochemical, non-enzymatic biosensor was proposed to quantify urea concentrations. For the detection of urea, the biosensor was modified with a multi-walled carbon nanotube-zinc oxide (MWCNT-ZnO) nanocomposite functionalized with copper oxide (CuO) micro-flowers (MFs). Further, the CuO-MFs were synthesized using a standard sol-gel approach, and the obtained particles were subjected to various characterization techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and Fourier transform infrared (FTIR) spectroscopy. The sensor’s performance for urea detection was evaluated by assessing the dependence of peak currents on analyte concentration using cyclic voltammetry (CV) at different scan rates of 50, 75, and 100 mV/s. The designed non-enzymatic biosensor showed an acceptable linear range of operation of 0.5–8 mM, and the limit of detection (LoD) observed was 78.479 nM, which is well aligned with the urea concentration found in human blood and exhibits a good sensitivity of 117.98 mA mM−1 cm−2. Additionally, different regression-based ML models were applied to determine CV parameters to predict urea concentrations experimentally. ML significantly improves the accuracy and reliability of screen-printed biosensors, enabling accurate predictions of urea levels. Finally, the combination of ML and biosensor design emphasizes not only the high sensitivity and accuracy of the sensor but also its potential for complex non-enzymatic urea detection applications. Future advancements in accurate biochemical sensing technologies are made possible by this strong and dependable methodology.
Electrochemical methods and devices have ignited prodigious interest for sensing and monitoring. The greatest challenge for science is far from meeting the expectations of consumers. Electrodes made of two-dimensional (2D) materials such as graphene, metal–organic frameworks, MXene, and transition metal dichalcogenides as well as alternative electrochemical sensing methods offer potential to improve selectivity, sensitivity, detection limit, and response time. Moreover, these advancements have accelerated the development of wearable and point-of-care electrochemical sensors, opening new possibilities and pathways for their applications. This Review presents a critical discussion of the recent developments and trends in electrochemical sensing.
Analytical chemistry applied to medical and diagnostic analysis has recently focused on the development of cost-effective biosensors able to monitor the health status or to assess the level of specific biomarkers that can be indicative of several diseases. The improvement of technologies relating to the possibility of the non-invasive sampling of biological fluids, as well as sensors for the detection of analytical signals and the computational capabilities of the systems routinely employed in everyday life (e.g., smartphones, computers, etc.), makes the complete integration of self-standing analytical devices more accessible. This review aims to discuss the biosensors that have been proposed in the last five years focusing on two principal detecting approaches, optical and electrochemical, which have been employed for quantifying different kinds of target analytes reaching detection limits below the clinical sample levels required. These detection principles applied to point-of-care (POC) devices have been extensively reported in literature, and even the limited examples found on the market are based on these strategies. This work will show the latest innovations considering the integration of optical and electrochemical detection with the most commonly reported analytical platforms for POC applications such as paper-based or wearable and implantable devices.
In this chapter, the use of miniaturized 2D-printed electrochemical devices for the detection of biomarkers is explored. This section reports the 3 different types and forms of construction of 2D electrochemical devices, as well as their architecture, materials used and production methods. In addition, different models are explored, such as electrodes obtained by screening, made from wearable seals and sensors, including modification with anchoring of different species, such as thin films, metallic nanoparticles, DNA strands, antibodies, enzymes, among others. others. Furthermore, the application of the devices and their advantages will be discussed in detail, as well as the future perspectives for the use of these devices.
Most cytokines are present at reduced amounts in body fluids due to their biological features of production, release, and action mechanisms. The required time between sampling and their measurement is critical for diagnosis and treatment. Electrochemical nanobiosensors offer the possibility to be tailor‐made and cost affordable, producing direct and rapid readouts with low sample volume, explaining their feasibility in timely measurements and potential in designing unique and multiplexed Point‐Of‐Care (POC) testing platforms. This review summarizes and discusses the measurement limitations of the standard methods and the recent progress on electrochemical nanobiosensors as a plausible alternative to measuring them.
Nowadays, various types of flexible and stretchable strain sensors have been used in the potential applications in smart wearable devices such as human motion detection, soft robotics, and health monitoring, etc. The stretchable strain sensor can be produced by several fabrication methods. However, the production of a strain sensor with desirable characteristics, cost-effectiveness, and suitable mass consumption, is still challenging. The aim of this present study is to compare composite strain sensors fabricated by three methods which are drop-casting, screen-printing, and spin-coating. In this study, silver nanoparticles (AgNPs) and polydimethylsiloxane (PDMS) were used to fabricate [email protected] composite based strain sensor. The electrical conductivity, hysteresis behaviour, and sensitivity of fabricated [email protected] composite based strain sensors were analyzed by different characterization methods and the results were supported by morphological analysis. Based on the obtained results, the drop-casting and screen-printing methods produced [email protected] composite strain sensors with good performance. Both methods produced [email protected] composite strain sensors with similar electrical conductivity. The best hysteresis behaviour and the highest sensitivity performance (GF = 10.08) were achieved in the drop-casting method due to the less cracking observed under 70% strain testing. In short, [email protected] composite based strain sensor fabricated by the drop-casting method exhibited good performance and it has a potential to be used as a strain sensor.
Due to the complexity of the screen‐printing operation and the rheological behaviors of the screen‐printable paste, such a paste is usually formulated by trial‐and‐error. In this report, a systematic procedure, based on heuristics and mechanistic models, for the design of a screen‐printable paste is developed. The procedure is demonstrated by a case study of the formulation of a conductive paste of copper particles.
In this article, textile based metamaterial, having broadband microwave absorption was developed using screen printing technique. The metamaterial has over 90% absorption from 7.39 GHz to 18 GHz. The metamaterial consists of a top layer of the printed structure of commercial conductive inks on various kinds of clothes, which is separated from a conductive ground plane with flexible dielectric foam of 3mm thickness. The metamaterial was simulated using ANSYS HFSS software for various thicknesses of the printed ink. It was observed that the absorption band varies with variation in thickness, and the optimized thickness is found to be about 50µm. With the increase in thickness the absorption shifts from broadband to narrow band. To achieve the optimum thickness in fabrication, statistically designed experiments were conducted to study the variation of printed thickness and width with different kinds of clothes and substrates (FR4, plain weave cotton cloth, twill weave cotton cloth), mesh number of the screen (50 to 110) and the number of passes (1 to 3). Substrate material and number of passes are found to be the most significant factors that affect the printed width resolution and thickness. Rigid copper foil and printed cloth could both be used as the ground plane. A complete, flexible absorber was fabricated using printed cloth as the groundplane. The microwave response (absorption) of all the fabricated absorbers were measured and compare and founds to be in agreement (more than 90%) with the simulation. Further, the fabricated absorber on cloth substrate is also made hydrophobic by treating with PDMS.
The constant and persistent synthesis and abuse of new psychoactive substances have sparked the requirement for rapid, on-site, sensitive analytical protocols for their sensing and quantification. Mephedrone (4-MMC) is currently one of the most popular legal highs among recreational drug abusers and imposes a serious public health problem. In this paper, the electrochemical sensing of two metabolites of 4-MMC, namely, nor-mephedrone (4-methylcathinone, 4-MC) and dihydromephedrone (4-methylephedrine, 4-MMC-R), utilizing screen-printed graphite electrodes is performed. The accessible linear ranges by cyclic voltammetry were found to correspond to 40-300 μg mL⁻¹ for 4-MC in both phosphate buffer solution (PBS, pH 7.0) and spiked diluted human urine, whereas in the case of 4-MMC-R, the linearity ranges are 15-300 μg mL⁻¹ (PBS, pH 3.0) and 25-300 μg mL⁻¹ (spiked diluted human urine). To maximize the assay sensitivity, differential pulse voltammetry (DPV) was performed toward the sensing of 4-MC, which exhibited a linear response over the range 10-250 and 10-300 μg mL⁻¹ in PBS pH 7.0 and spiked diluted human urine, respectively. However, 4-MMC-R demonstrated slightly higher sensitivity over the range 5-300 μg mL⁻¹ in both PBS pH 3.0 and spiked diluted human urine. Using DPV, the limits of detection (3σ) were calculated and found to correspond to ca. 3.97 and 3.64 μg mL⁻¹ for 4-MC and 4-MMC-R (PBS, pH 7.0 and 3.0), respectively, and ca. 6.34 and 3.87 μg mL⁻¹ for 4-MC and 4-MMC-R (spiked diluted human urine), respectively. The potential interference of adulterants' metabolites commonly found in NPS street samples was also explored (at both pH 7.0 and 3.0). The electrochemical approach reported herein provides a novel laboratory tool for the identification and quantification of synthetic cathinone metabolites and has potential for the basis of a portable analytical sensor for their fast, cheap, reliable, and accessible determination in the field.
The application of a novel fully 3-D printed carbon nanofiber–graphite–polystyrene electrode has been investigated for the trace determination of Zn²⁺ by differential pulse anodic stripping voltammetry. The possibility of utilising a carbon pseudo-reference electrode was found to be successful. The effect of accumulation potential and time were investigated and optimised. Using an accumulation potential of −2.9 V (vs. C) and an accumulation time of 75 s a single sharp anodic stripping peak was recorded exhibiting a linear response from 12.7 μg/L to 450 μg/L. The theoretical detection limit (3σ) was calculated as 8.6 μg/L. Using the optimised conditions a mean recovery of 97.8%, (%CV = 2.0%, n = 5) for a tap water sample fortified at 0.990 μg/mL was obtained indicating the method holds promise for the determination of Zn²⁺ in such samples.
We demonstrate a facile, low cost and reproducible methodology for the production of electrocatalytic 2D-MoSe2 incorporated/bulk modified screen-printed electrodes (MoSe2-SPEs). The MoSe2-SPEs outperform traditional carbon based electrodes, in terms of their electrochemical activity, towards the Hydrogen Evolution Reaction (HER). The electrocatalytic behaviour towards the HER of the 2D-MoSe2 within the fabricated electrodes is found to be mass dependent, with an optimal mass ratio of 10% 2D-MoSe2 to 90% carbon ink. MoSe2-SPEs with this optimised ratio exhibit a HER onset, Tafel value and a turn over frequency of ca. −460 mV (vs. SCE), 47 mV dec−1 and 1.48 respectively. These values far exceed the HER performance of graphite (unmodified) SPEs, that exhibit a greater electronegative HER onset and Tafel value of ca. −880 mV and 120 mV dec−1 respectively. It is clear that impregnation of 2D-MoSe2 into the MoSe2-SPEs bulk ink/structure significantly increases the performance of SPEs with respect to their electrocatalytic activity towards the HER. When compared to SPEs that have been modified via a drop-casting technique, the fabricated MoSe2-SPEs exhibit excellent cycling stability. After 1000 repeat scans, a 10% modified MoSe2-SPE displayed no change in its HER onset potential of −450 mV (vs. SCE) and an increase of 31.6% in achievable current density. Conversely, a SPE modified via drop-casting with 400 mg cm−2 of 2D-MoSe2 maintained its HER onset potential of −480 mV (vs. SCE), however exhibited a 27.4% decrease in its achievable current density after 1000 scans. In addition to the clear performance benefits, the production of MoSe2-SPEs mitigates the need to post hoc modify an electrode via the drop-casting technique. We anticipate that this facile production method will serve as a powerful tool for future studies seeking to utilise 2D materials in order to mass-produce SPEs/surfaces with unique electrochemical properties whilst providing substantial stability improvements over the traditionally utilised technique of drop-casting.
In this paper the effect of solvent induced chemical surface enhancements upon graphitic screen-printed electrodes (SPEs) are explored. Previous literature has indicated that treating the working electrode of a SPE with the solvent N,N-dimethylformamide (DMF) offers improvements in the electroanalytical response, resulting in a 57-fold increment in the electrode surface area compared to their unmodified counterparts. The protocol involves two steps: i) the SPE is placed into DMF for a selected time, and ii) is cured in an oven at a selected time and temperature. Beneficial electroanalytical outputs are reported to be due to the increased surface area attributed to the binder within the bulk surface of the SPEs dissolving out during the immersion step (step i). We revisit this exciting concept and explore these solvent induced chemical surface enhancements using edge- and basal- plane like SPEs and a new bespoke SPE, utilising the solvent DMF and explore, in detail, the parameters utilised in steps (i) and (ii). The electrochemical performance following steps (i) and (ii) is evaluated using the outer-sphere redox probe hexaammineruthenium (III) chloride / 0.1 M KCl where it is found that the largest improvement is obtained using DMF with an immersion time of 10 minutes and a curing time of 30 minutes at 100 °C. Solvent induced chemical surface enhancement upon the electrochemical performance of SPEs is also benchmarked in terms of their electroanalytical sensing of NADH (dihydronicotinamide adenine dinucleotide reduced form) and capsaicin both of which are compared to their unmodified SPE counterparts. In both cases, it is apparent that a marginal improvement in the electroanalytical sensitivity (gradient of calibration plots) of 1.08-fold and 1.38-fold is found respectively. Returning to the original exciting concept, interestingly it was found that when poor experimental technique was employed, only then significant increases within the working electrode area are evident. In this case, the insulating layer that defines the working electrode surface, which was not protected from the solvent (step (i)) creates cracks within the insulating layer exposing the underlying carbon connections and thus increasing the electrode area by an unknown quantity. We infer that the origin of the response reported within the literature, where an extreme increase in the electrochemical surface area (57-fold) was reported, is unlikely to be solely due to the binder dissolving but rather poor experimental control over step (i).
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