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The selection of an appropriate transducer is a key element in biosensor development. Currently, a wide variety of substrates and working electrode materials utilizing different fabrication techniques are used in the field of biosensors. In the frame of this study, the following three specific material configurations with gold-finish layers were investigated regarding their efficacy to be used as electrochemical (EC) biosensors: (I) a silicone-based sensor substrate with a layer configuration of 50 nm SiO/50 nm SiN/100 nm Au/30-50 nm WTi/140 nm SiO/bulk Si); (II) polyethylene naphthalate (PEN) with a gold inkjet-printed layer; and (III) polyethylene terephthalate (PET) with a screen-printed gold layer. Electrodes were characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) to evaluate their performance as electrochemical transducers in an aptamer-based biosensor for the detection of cardiac troponin I using the redox molecule hexacyanoferrade/hexacyaniferrade (K3[Fe (CN)6]/K4[Fe (CN)6]. Baseline signals were obtained from clean electrodes after a specific cleaning procedure and after functionalization with the thiolate cardiac troponin I aptamers "Tro4" and "Tro6". With the goal of improving the PEN-based and PET-based performance, sintered PEN-based samples and PET-based samples with a carbon or silver layer under the gold were studied. The effect of a high number of immobilized aptamers will be tested in further work using the PEN-based sample. In this study, the charge-transfer resistance (Rct), anodic peak height (I pa ), cathodic peak height (I pc ) and peak separation (∆E) were determined. The PEN-based electrodes demonstrated better biosensor properties such as lower initial Rct values, a greater change in Rct after the immobilization of the Tro4 aptamer on its surface, higher I pc and I pa values and lower ∆E, which correlated with a higher number of immobilized aptamers compared with the other two types of samples functionalized using the same procedure.

Understanding the electric double layer (EDL) of the metal electrode–electrolyte interface is essential to electrochemistry and relevant disciplines. In this study, potential-dependent electrode Sum Frequency Generation (SFG) intensities of polycrystalline gold electrodes in HClO4 and H2SO4 electrolytes were thoroughly analyzed. The potential of zero charges (PZC) of the electrodes was −0.06 and 0.38 V in HClO4 and H2SO4, respectively, determined from differential capacity curves. Without specific adsorption, the total SFG intensity was dominated by the contribution from the Au surface and increased similar to that of the visible (VIS) wavelength scanning, which pushed the SFG process closer to the double resonant condition in HClO4. However, the EDL contributed about 30% SFG signal with specific adsorption in H2SO4. Below PZC, the total SFG intensity was dominated by the Au surface contribution and increased with potential at a similar slope in these two electrolytes. Around PZC, as the EDL structure became less ordered and the electric field changed direction, there would be no EDL SFG contribution. Above PZC, the total SFG intensity increased much more rapidly with potential in H2SO4 than in HClO4, which suggested that the EDL SFG contribution kept increasing with more specific adsorbed surface ions from H2SO4. [ABSTRACT FROM AUTHOR]

Modified electrodes based on gold particles, mixed-valence ruthenium oxides, and a binary system combining these components were developed for the voltammetric determination of ceftriaxone, cefotaxime, and cefoperazone. The electrode with the binary system of gold particles and mixed-valence ruthenium oxides, which exhibited the best performance, was used for the detection of cephalosporins in flow-injection analysis. Optimal conditions for the detection of cephalosporins in a flow-injection system were selected. The dependence of the analytical signal on the concentration of the compounds under consideration is linear on logarithmic coordinates over the range from 5 × 10–7 to 5 × 10–3 M. The proposed procedure was tested in the determination of cephalosporins in pharmaceuticals. [ABSTRACT FROM AUTHOR]

Maintaining stability of single-molecular junctions (SMJs) in the presence of current flow is a prerequisite for their potential device applications. However, theoretical understanding of nonequilibrium heat transport in current-carrying SMJs is a challenging problem due to the different kinds of nonlinear interactions involved, including electron–vibration and anharmonic vibrational coupling. Here, we overcome this challenge by accelerating Langevin-type current-induced molecular dynamics using machine-learning potential derived from density functional theory. We show that SMJs with graphene electrodes generate an order of magnitude less heating than those with gold electrodes. This is rooted in the better phonon spectral overlap of graphene with molecular vibrations, rendering harmonic phonon heat transport being dominant. In contrast, in a spectrally mismatched junction with gold electrodes, anharmonic coupling becomes important to transport heat away from the molecule to surrounding electrodes. Our work paves the way for studying current-induced heat transport and energy redistribution in realistic SMJs. [ABSTRACT FROM AUTHOR]

(1) Background: Particulate methane monooxygenase (pMMO) has a strong dependence on the natural electron transfer path and is prone to denaturation, which results in its redox activity centers being unable to transfer electrons with bare electrodes directly and making it challenging to observe an electrochemical response; (2) Methods: Using methanobactin (Mb) as the electron transporter between gold electrodes and pMMO, a bionic interface with high biocompatibility and stability was created. The Mb-AuNPs-modified functionalized gold net electrode as a working electrode, the kinetic behaviors of pMMO bioelectrocatalysis, and the effect of Mb on pMMO were analyzed. The CV tests were performed at different scanning rates to obtain electrochemical kinetics parameters. (3) Results: The values of the electron transfer coefficient (α) and electron transfer rate constant (ks) are relatively large in test environments containing only CH4 or O2. In contrast, in the test environment containing both CH4 and O2, the bioelectrocatalysis of pMMO is a two-electron transfer process with a relatively small α and ks; (4) Conclusions: It was inferred that Mb formed the complex with pMMO. More importantly, Mb not only played a role in electron transfer but also in stabilizing the enzyme structure of pMMO and maintaining a specific redox state. Furthermore, the continuous catalytic oxidation of natural substrate methane was realized. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cell technology is one of the key focus areas to facilitate the transition from carbon-based fuels to more sustainable solutions in the transportation and mobile power sectors. Transient voltage fluctuations due to load changes and even operation of fuel cells with DC/DC and DC/AC converters are detrimental to the lifetime and this paper proposes a method to deal with these fluctuations. Adding electric field modifier (EFM) electrodes made of gold to the membrane of a fuel cell was proposed elsewhere as a way to influence the short term flux of charge carriers through the membrane. While electrochemical impedance spectroscopy shows a limited capacitance of such electrodes, experiments using square wave excitation of the system in the kHz frequency range show a promising reaction of the cell to this treatment. More in-depth analysis of the used electrode material reveals the need to insulate future EFM electrodes in order to prevent oxidative dissolution. However, this work shows that the principle of using EFM electrodes to manipulate transient oscillations is physically sound. • Square Wave excitation of EFMs shows effect on cell voltage. • EIS measurement provides specific capacity of gold EFM similar to literature value. • Cyclic Voltammetry measurements of gold mesh electrodes in Nafion, behaviour equivalent to gold in acid solution. • Scanning electron microscopy confirms oxidative dissolution of gold in membrane due to potential cycling. [ABSTRACT FROM AUTHOR]

In situ dual‐modal detection of electrophysiology (EP) and blood oxygen (BO) during muscle–vascular activity is crucial for healthcare and human–machine interaction. It requires an integrated monitoring system: a transparent electrode for EP detection directly adhered to skin and a near‐infrared spectroscopy (NIRs) layer for BO detection. In particular, the multi‐channel, highly transparent, stretchable electrodes should be well developed. In this study, 16‐channel transparent ionotronic electrodes are fabricated based on a stretchable and printable ionogel, demonstrating excellent properties such as high transparency, large stretchability, wet adhesion, biocompatibility, softness, and long‐term stability. The electrode exhibits stable contact impedance for 24 h and a 2‐week periodic EP monitoring. The 16‐channel transparent ionotronic electrode outperforms stretchable gold electrodes by providing stable EP monitoring with minimal interference in NIRs for blood oxygen detection. An in situ negative correlation is found between EP intensity and blood oxygen level over time. This study paves the way for designing transparent ionotronics for synchronous optical‐related monitoring and highlights the potential use of an in situ dual‐modal monitoring system for the study of muscle–vascular coupling in neurocience and rehabilitation. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) black phosphorus (BP) is considered an ideal building block for field-effect transistors (FETs) owing to its unique structure and intriguing properties. To achieve high-performance BP-FETs, it is essential to establish a reliable and low-resistance contact between the BP and the electrodes. In this study, we employed a localized Joule heating method to improve the contact between the 2D BP and gold electrodes, resulting in enhanced BP-FET performance. Upon applying a sufficiently large source–drain voltage, the zero-bias conductance of the device increased by approximately five orders of magnitude, and the linearity of the current–voltage curves was also enhanced. This contact improvement can be attributed to the formation of gold phosphide at the interface of the BP and the gold electrodes owing to current-generated localized Joule heat. The fabricated BP-FET demonstrated a high on/off ratio of 4850 and an on-state conductance per unit channel width of 1.25 μS μm−1, significantly surpassing those of the BP-FETs without electrical annealing. These findings offer a method to achieve a low-resistance BP/metal contact for developing high-performance BP-based electronic devices. [ABSTRACT FROM AUTHOR]

In this research, novel electroencephalogram (EEG) electrodes were developed to detect high-quality EEG signals without the requirement of conductive gels, skin treatments, or head shaving. These electrodes were created using electrically conductive hook fabric with a resistance of 1 Ω/sq. The pointed hooks of the conductive fabric establish direct contact with the skin and can penetrate through hair. To ensure excellent contact between the hook fabric electrode and the scalp, a knitted-net EEG bridge cap with a bridging effect was employed. The results showed that the hook fabric electrode exhibited lower skin-to-electrode impedance compared to the dry Ag/AgCl comb electrode. Additionally, it collected high-quality signals on par with the standard wet gold cups and commercial dry Ag/AgCl comb electrodes. Moreover, the hook fabric electrode displayed a higher signal-to-noise ratio (33.6 dB) with a 4.2% advantage over the standard wet gold cup electrode. This innovative electrode design eliminates the need for conductive gel and head shaving, offering enhanced flexibility and lightweight characteristics, making it ideal for integration into textile structures and facilitating convenient long-term monitoring. [ABSTRACT FROM AUTHOR]

Developing neural electrodes with high stretchability and stable conductivity is a promising method to explore applications of them in biological medicine and electronic skin. However, considering the poor mechanical stretchability of typical conductive materials, maintaining the connection of electrode conductive paths under high stretching is still a challenge. Herein, for the first time, a double‐microcrack coupling strategy for highly stretchable neural electrodes is proposed. Compared with single‐layer stretchable microcrack electrodes, the design utilizes the complement between two gold microcrack films to contribute more conductive paths. It shows that the resistance change (R/R0) of the electrode under 100% strain is about 5.6 times, which is much lower than other electrodes and exhibits a high stretchability of ≈200%. Simultaneously, this design is an encapsulation‐free design which avoids the electrode performance degradation caused by encapsulation. Furthermore, it is found that the adhesion strength between metal electrode and substrate is critical to the stretchability and stability of electrodes, so polydimethylsiloxane0.9‐isophorone diisocyanate elastomer (PDMS0.9‐IPDI), whose adhesion to gold electrode is 4.5 times higher than that of the commercial polydimethylsiloxane (PDMS), is synthesized. Finally, the electrophysiological communication between different organisms by electrodes is successfully demonstrated. [ABSTRACT FROM AUTHOR]

An electrode composite containing a metal organic framework (Mn-MIL-100) was prepared by linkers including gold nanoparticles/polypyrrole and cysteine. The electrocatalytic application of this nanocomposite was evaluated via the oxidation of benzylic and aliphatic alcohols under open air conditions. Various active and inactive alcohol derivatives were successfully converted to the corresponding ketones with excellent yields. This advanced electrocatalyst proved to have remarkable stability over several recovery cycles from the reaction medium without significant change in its activity and selectivity and its regeneration potential. The active surface area of this electrocatalyst is very large due to its structural features, arising from the introduction of a metal organic framework (Mn-MIL-100) on a gold electrode, which provides more accessible surface sites, therefore boosting the electrocatalytic activity. The structure of the synthesized electrocatalyst has been characterized by FESEM, EDX, and AFM techniques. [ABSTRACT FROM AUTHOR]

A simple equivalent electrical circuit is used to obtain the physical parameters of electrical circuit elements from measured electrochemical impedance spectra. This model consists of four circuit elements with a clear physical meaning for each of the elements. Compared to complex models with multiple constant phase elements or Warburg impedances, our model is suitable for extracting physical values for important electrode parameters with low errors. The feasibility of the model was shown by investigating pure metal or polymer‐coated electrodes. Here, gold electrodes were coated either with Poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT : PSS), Polypyrrole:poly(styrenesulfonate) (PPy : PSS), or (PEDOT/PPy) : PSS by means of electropolymerization. The model could demonstrate the ionic‐electronic differences such as the ion accessibility of the differently coated electrodes. To prove the correctness of the model, the obtained results were compared to the literature. [ABSTRACT FROM AUTHOR]

Gold electrodes are some of the most prevalent electrochemical biosensor substrate materials because they are readily functionalized with thiolated biomolecules. Yet, conventional methods to fabricate gold electrodes are costly and require onerous equipment, precluding them from implementation in low-resource settings (LRS). Recently, a number of alternative gold electrode fabrication methods have been developed to simplify and lower the cost of manufacturing. These methods include screen and inkjet printing as well as physical fabrication with common materials such as wire or gold leaf. All electrodes generated with these methods have successfully been functionalized with thiolated molecules, demonstrating their suitability for use in biosensors. Here, we detail recent advances in the fabrication, characterization and functionalization of these next-generation gold electrodes, with an emphasis on comparisons between cost and complexity with traditional cleanroom fabrication. We highlight gold leaf electrodes for their potential in LRS. This class of electrodes is anticipated to be broadly applicable beyond LRS due to their numerous inherent advantages. [ABSTRACT FROM AUTHOR]

A rapid method for determination of hydrogen peroxide based on a non‐enzymatic amperometric sensor with an online dialysis unit was developed for analysis of sample with complicated matrices. A porous gold modified gold screen‐printed electrode was prepared by a simple method using 9 V‐battery electrodeposition. Based on data from amperometry, a linear dynamic range can be obtained in the range of 10 to 1000 μmol L−1, with a limit of detection of 0.37 μmol L−1. The proposed system was successfully applied to determine H2O2 in various milk samples with rapid analysis, high electrode stability, and excellent repeatability (1.95 % RSD with 100 replications). [ABSTRACT FROM AUTHOR]

In this review, functionalized nanogaps embedded in nanopores are discussed in view of their high biosensitivity in detecting biomolecules, their length, type, and sequence. Specific focus is given on nanoelectrodes functionalized with tiny nanometer‐sized diamond‐like particles offering vast functionalization possibilities for gold junction electrodes. This choice of the functionalization, in turn, offers nucleotide‐specific binding possibilities improving the detection signals arising from such functionalized electrodes potentially embedded in a nanopore. The review sheds light onto the use and enhancement of the tunnelling recognition in functionalized nanogaps towards sensing DNA nucleotides and mutation detection, providing important input for a practical realization. [ABSTRACT FROM AUTHOR]

Studies of electrosensory systems have led to insights into a number of general issues in biology. However, investigations of these systems have been limited by the inability to precisely control spatial patterns of electrosensory input. In this paper, an electrode array and a system to selectively stimulate spatially restricted regions of an electroreceptor array are presented. The array has 96 channels consisting of chrome/gold electrodes patterned on a flexible parylene‐C substrate and encapsulated with another parylene‐C layer. The conformability of the electrode array allows for optimal current driving and surface interface conditions. Recordings of neural activity at the first central processing stage in weakly electric mormyrid fish support the potential of this system for high spatial resolution stimulation and mapping of electrosensory systems. [ABSTRACT FROM AUTHOR]

The development of a reliable and sensitive method for the detection of myocardial infarction (MI)-specific miRNAs is of great significance in the diagnosis and management of MI. Electrochemical biosensors have emerged as a promising tool for the detection of biomolecules due to their high sensitivity, selectivity, simplicity of operation, and miniaturization. In order to further improve the sensitivity and selectivity of DNA electrochemical biosensors and meet the requirements of microRNA detection in biological samples, we fabricated a patterned superwettable gold electrode (PS-Au electrode) by mimicking the superwettable micropatterns of the desert beetle. Combining this bioinspired electrode with a DSN-assisted target recycling amplification strategy, we achieved ultrasensitive detection of myocardial infarction-specific miRNA-483 ranging from 10 aM to 100 fM with a low detection limit of 5.32 aM for miRNA-483. The electrochemical biosensor based on PS-Au electrode and DSN-assisted target recycling amplification (PSE-DTRA-EB) has good stability and specificity. Our study provides a new method for the ultrasensitive detection of MI-specific miRNAs, which may have important clinical applications in the diagnosis and prognosis of MI. [Display omitted] • Design of patterned superwettable site of PS-Au electrode can enrich analyte. • Patterned superwettable site of PS-Au electrode can reduce analyte consumption. • The PSE-DTRA-EB can detect 5.32 aM miRNA-483 with good stability and specificity. [ABSTRACT FROM AUTHOR]

Surface cleaning of the working electrode has a key role in improved electrochemical and physicochemical properties of the biosensors. Herein, chemical oxidation in piranha, chemical cleaning in potassium hydroxide-hydrogen peroxide, combined (electro-) chemical alkaline treatment, and potential cycling in sulfuric acid were applied to gold finish electrode surfaces deposited onto three different substrates; low temperature co-fired ceramics (LTCC), polyethylene naphthalate (PEN), and polyimide (PI), using three different deposition technologies; screen printing, inkjet printing, and electroplating (printed circuit board technology, PCB) accordingly. The effects of the (electro-) chemical treatments on the gold content and electrochemical responses of LTCC, PEN, and PCB applicable for aptamer-based sensors are discussed. In order to assess the gold surface and to compare the efficiency of the respective cleaning procedures; cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed. LTCC sensors electrochemically cycled in sulfuric acid resulted in the most gold content on the electrode surface, the lowest peak potential difference, and the highest charge transfer ability. While, for PEN, the highest elemental gold and the lowest peak-to-peak separation were achieved by a combined (electro-) chemical alkaline treatment. Gold content and electrochemical characteristics on the PCB surface with extremely thin gold layer could be slightly optimized with the chemical cleaning in KOH + H2O2. The proposed cleaning procedures might be generally applied to various kinds of Au electrodes fabricated with the same conditions comparable with those are introduced in this study. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are attracting widespread attention due to their exceptional photovoltaic performance and their potential for large‐scale production via low‐cost, high‐throughput roll‐to‐roll (R2R) methods. Full realization of this production approach requires replacement of the evaporated metal electrode commonly used in PSCs. Here, a novel vacuum‐free R2R‐compatible method is introduced to fabricate and deposit printed electrodes based on electrically conductive pastes, which avoids potential loss of PSC performance due to solvent migration from the pastes. Flexible R2R‐fabricated PSCs with record power conversion efficiencies (PCEs) of up to 16.7% are produced by vacuum‐free deposition of all functional layers, apart from the transparent conductive electrode. This performance compares very favorably with that of control flexible PSCs comprising an evaporated gold electrode, which displays PCEs of up to 17.4%. Furthermore, the PSCs comprising a printed electrode demonstrate outstanding operational and mechanical stability, with negligible loss of PCE after 24 h of continuous 1‐sun illumination and retention of more than 90% of their initial PCE after 3000 cyclic bends. [ABSTRACT FROM AUTHOR]

Highly active, robust, cheap, and environmentally benign electrocatalysts for the oxygen evolution reaction (OER) are critically important to develop a sustainable artificial energy cycle. Here, we report the in situ synthesis of mononuclear manganese(III) pincer complexes [Mn(OAc)(L)(cbpy)] (1) and [Mn(OAc)(L1)(cbpy)] (2) on a gold electrode surface through a self-assembly process (where OAc = acetate, cbpy = 2,2′-bipyridine-4-carboxylic acid anion, L = N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate (2-) and L1 = N,N′-(diphenyl)-2,6-pyridinedicarboxamidate (2-)) and explore their activity for the electrocatalytic OER (2H2O = 4H+ + 4e− + O2) in neutral pH medium. The modified electrode was characterized by using microscopic (FE-SEM), spectroscopic (EDX, ATR-FTIR, SERS), and electrochemical (CV and EIS) methods. The newly developed heterogenized molecular catalysts 1 and 2 can catalyze the OER exceptionally well with a low overpotential of 260 mV at J = 3.2 mA cm−2 and 275 mV at J = 2.46 mA cm−2, respectively. The Tafel slopes were found to be 68 and 77 mV decade−1 for the catalysts 1 and 2, respectively. These results support the higher OER activity of complex 1 than complex 2 under similar conditions and this may be due to more electron donating power of pincer ligand L than L1, which in turn stabilizes the high valent manganese complex intermediates. Furthermore, after long-term controlled potential electrolysis (∼ 6 h), the surface-immobilized manganese complex does not decompose into manganese oxide and preserves the molecular identity as evident from electrochemical, spectroscopic and microscopic results. [ABSTRACT FROM AUTHOR]

Owing to the high power conversion efficiency (PCE) and the solution‐processed fabrication process, perovskite solar cells (PSCs) have attracted wide attention, while most high‐performance PSCs have an n‐i‐p (conventional) configuration that requires the expensive Au electrode. Silver is widely considered as one of the most promising candidates to replace gold as the top electrode material in conventional perovskite solar cells, due to its high conductivity and relatively low price. However, due to the mismatching energy levels between the Ag electrode and the hole transporting layer, Ag electrode‐based PSCs require long‐time aging to achieve their best performance. Herein, an AgI modification layer at the Ag electrode/hole transporting layer interface is employed, which eliminates the s‐shaped bend in current density–voltage (J–V) curves of fresh PSCs with the Ag electrode and helps to achieve high‐performance devices without any posttreatment. Optimized devices show a top PCE of up to 20.45% at the beginning, which is higher than that of the fresh (5.80%) and aged (19.31%) pristine counterparts. In addition, the facile method is also available for other iodides such as NH4I, KI, and CuI. This universal approach enables Ag to be a competitive material for electrode in high‐performance and low‐cost PSCs. [ABSTRACT FROM AUTHOR]

Procalcitonin (PCT) is considered a sepsis and infection biomarker. Herein, an interdigitated electrochemical immunosensor for the determination of PCT has been developed. The interdigitated electrode was made of the laser-engraved graphene electrode decorated with gold (LEGE/Aunano). The scanning electron microscopy indicated the LEGE/Aunano has been fabricated successfully. After that, the anti-PTC antibodies were immobilized on the surface of the electrode by using 3-mercaptopropionic acid. The electrochemical performance of the fabricated immunosensor was studied using electrochemical impedance spectroscopy (EIS). The EIS method was used for the determination of PCT in the concentration range of 2.5–800 pg/mL with a limit of detection of 0.36 pg/mL. The effect of several interfering agents such as the C reactive protein (CRP), immunoglobulin G (IgG), and human serum albumin (HSA) was also studied. The fabricated immunosensor had a good selectivity to the PCT. The stability of the immunosensor was also studied for 1 month. The relative standard deviation (RSD) was obtained to be 5.2%. [ABSTRACT FROM AUTHOR]

Electrophysiology and neurochemicals such as Ca2+, K+, and Na+ on the cerebral cortex can synergistically reflect the neurophysiological states. Transparent electrodes have been reported to record electrocorticography (ECoG) and image Ca2+ on the cerebral cortex surface. However, Ca2+ imaging is unable to track extracellular changes correlated with neural activities such as anesthesia, and imaging techniques to monitor K+ and Na+ are yet unavailable. Here, a flexible multifunctional electrode (FME) based on carbon nanotube array is presented to record ECoG and extracellular ions of Ca2+, K+, and Na+. The FME exhibits both lower impedance and higher capacitance than that of conventional gold electrodes. It simultaneously shows stable ion‐sensing performance and long‐term biocompatibility. The FME realizes multi‐model recording of ECoG and extracellular ions on the cerebral cortex surface of rats, providing an effective detection method for brain science. [ABSTRACT FROM AUTHOR]

[Display omitted] • Insensitive explosive NTO was electrochemically determined by a smartphone application. • Polyethyleneimine (PEI)−modified GC- and SP-electrodes created a sensing platform for NTO. • Electrostatic and hydrogen bonding interactions between PEI and NTO enhanced sensitivity. • Cobalt-amine sites formed between PEI and cobalt(II)-acetylacetonate served as electrocatalyst. • Validated method was not affected by electroactive camouflage materials and soil ions. Rapid and sensitive voltammetric methods for 3-nitro-1,2,4-triazol-5-one (NTO) determination are scarce in the literature. In the present research, we reported a crosslinked polyelectrolyte-based modified electrode decorated with gold nanoparticles that can be easily formed on the surfaces of both screen-printed electrodes (SPEs) and glassy carbon electrodes (GCEs) for the first time, as well as a voltammetric method for the electrochemical determination of NTO. Cobalt-amine sites formed between PEI and cobalt(II)-acetylacetonate (CoAcAc, an electrocatalyst) are used as a redox mediator. Electrochemical reduction of NTO in the concentration range of 1.3–13 mg L−1 was carried out by both the developed DPV method and a smartphone application. LOD and LOQ values were found to be 0.4 mg L−1 and 1.25 mg L−1 for the developed DPV method and 0.26 mg L−1 and 0.82 mg L−1 for the smartphone implementations, respectively. By taking advantage of the restricted solubility of some other nitro-explosives in water, the solvent medium and the pH of the supporting electrolyte (the pH value at which NTO exists in anionic form, not valid for other explosives) were optimized. In the presence of other nitro explosives, such as trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 2,4-dinitro toluene (DNT), and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), the percentage recovery values range from 90.1 to 105.2 % according to the DPV results measured in admixtures with NTO. Surface morphologies of the modified electrode were characterized using scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR), whereas electrochemical studies were performed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The detection method proposed was not adversely affected by common soil ions as well as detergents, sugar, sweeteners, caffeine, and paracetamol-based painkillers as camouflage materials for explosives, the negative impacts of which were either nonexistent or eliminable. [ABSTRACT FROM AUTHOR]

Hydrogen evolution reaction (HER) on Au electrode in perchloric acid and NaOH solutions were studied using an inverted rotating disc electrode (IRDE). IRDE enables investigations of gas evolution reactions in a large potential and current window. In this configuration, the electrode is not obstructed by the product gas bubbles. Potentiodynamic polarization data were acquired at various concentrations of HClO 4 and NaOH, and at a few electrode rotational speeds. At large over-potentials, diffusion-limited currents were observed in HClO 4 solutions. In the case of HER on Au in acidic media, the Volmer-Heyrovsky-Tafel (VHT) mechanism best describes the polarization results. The fractional surface area covered by adsorbed hydrogen and the rate of reaction for individual steps were estimated using the model. At low H+ concentrations, HER proceeds mainly by the Volmer-Tafel (VT) pathway while at high H+ concentrations, Heyrovsky and Tafel pathways are equally important. In the alkaline media, HER rate was found to be independent of NaOH concentration and electrode rotational speed, and the reaction mechanism could not be identified unambiguously. The results illustrate the importance of analyzing data acquired at several reactant concentrations and at a wide potential range, to identify the reaction mechanism. [Display omitted] • Inverted rotating disc electrode to study HER in large potential/current window. • HER in HClO 4 solutions limited by mass transfer of H+ ions. • At low acid concentrations, on Au, Volmer-Tafel is the main HER route. • At high acid concentration, on Au, Heyrovsky step also contributes. • HER in alkaline media independent of NaOH concentration and rotational speed. [ABSTRACT FROM AUTHOR]

Electrode–electrolyte interfaces are the heart of electrochemical reactions. Activation of electrode surfaces by electrochemical pretreatment can endow electrodes with promoted physicochemical properties to facilitate electron-transfer kinetics during electrochemical reactions. However, comprehensive understanding of the activation mechanism, especially in aspects of surface chemical evolution is limited. Herein, we applied ToF-SIMS in combination with SEM imaging to investigate the electrochemical activation in different stages of gold electrode surfaces in hydrochloric acid solution. The results unraveled the complicated activation mechanism, which not only involved the surface reconstruction with formation of an ultra-thin layer of nanoparticles, but also the significantly altered outmost surface chemistry of the electrodes such as the efficient removal of poisonous surface contamination species. We demonstrate that with the virtues of ultra-high surface sensitivity, shallow information depth, and rich molecular characterization information, ToF-SIMS is a powerful technique for characterization of surface chemistry of electrodes/electrocatalysts. The promising applications of ToF-SIMS will advance the fundamental understanding of the surface chemistry-electrochemical/electrocatalytic activity relationship and facilitate the control and engineering of electrochemical interfaces with promoted performance. [ABSTRACT FROM AUTHOR]

Screen-printed electrodes-based sensors can be successfully used to determine all kinds of analytes with great precision and specificity. However, obtaining a high-quality sensor can be difficult due to factors such as lack of reproducibility, surface contamination or other manufacturing challenges. An important step in ensuring reproducible results is the cleaning step. The aim of the current work is to help researchers around the world who struggle with finding the most suitable method for cleaning screen-printed electrodes. We evaluated the cleaning efficiency of different chemical compounds and cleaning methods using cyclic voltammetry and electrochemical impedance spectroscopy. The percentage differences in polarization resistance (Rp) before and after cleaning were as follows: acetone—35.33% for gold and 49.94 for platinum; ethanol—44.50% for gold and 81.68% for platinum; H2O2—47.34% for gold and 92.78% for platinum; electrochemical method—3.70% for gold and 67.96% for platinum. Thus, we concluded that all the evaluated cleaning methods seem to improve the surface of both gold and platinum electrodes; however, the most important reduction in the polarization resistance (Rp) was obtained after treating them with a solution of H2O2 and multiple CV cycles with a low scanning speed (10 mV/s). [ABSTRACT FROM AUTHOR]

This paper investigated the effect of electrode materials on the performance of quartz crystal microbalance (QCM) sensors by means of theoretical calculation, experiment, and finite element analysis methods. First, we calculated the particle displacement amplitude and thus obtained the mass sensitivity function distribution of QCMs with gold, silver and aluminum electrodes, and found that the QCM with the gold electrode has the highest mass sensitivity at the center of the electrode. Then, we tested the humidity-sensing performance of QCMs with gold, silver, and aluminum electrodes using graphene oxide (GO) as the sensitive material, and found that the QCM with the gold electrode has higher humidity sensitivity. Finally, we used the finite element analysis software COMSOL Multiphysics to simulate the specific electrode material parameters that affect the sensitivity of the QCMs. The simulation results show that the density and Young's modulus of the electrode material parameters mainly affect the sensitivity. The results of this paper are instructive for optimizing QCM sensor performance and improving the capability of QCM quantitative analysis. [ABSTRACT FROM AUTHOR]

Transparent implantable devices have received significant attention in neuroscience and biomedical engineering by combining neural recording and optical modalities. Opaque, metal‐based electrode arrays for electrophysiology block optical imaging and cause photoelectric artifacts, making them difficult to integrate with optogenetics. Here, a photoelectric artifact‐free, highly conductive, and transparent poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrode array is introduced as promising neural implants. The technology which is developed in this work provides transparent neural interfaces through low‐cost, ultra‐facile method compared with other transparent materials being applied to implantable tools. The device exhibits superior optical, mechanical, and electrical characteristics to other studies, thanks to a simple ethylene glycol immersing process. The device performance is highlighted by comparing its light stimulation efficiency and photoelectric artifact extent with conventional thin gold electrodes both in vitro and in vivo. This platform can assemble transparent neural interfaces much more efficiently than any other material candidates and thus has many potential applications. [ABSTRACT FROM AUTHOR]

Pesticides are unavoidable in agriculture to protect crops from pests and insects. Organophosphates (OPs) are a class of pesticides that are more harmful because of the irreversible inhibition reaction with acetylcholinesterase enzyme, thereby posing serious health hazards in human beings. In the present work, a sensitive and selective immuno-sensing platform is developed using gold inter-digitized electrodes (Au-IDEs) as substrates, integrated with a microfluidic platform having the microfluidic well capacity of 10 µL. Au-IDE having digit width of 10 µm and gap length of 5 µm was used in this study. The surface morphological analysis by field-effect scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM) revealed the direct information regarding the modification of Au-IDEs with anti-parathion (Anti-PT) antibodies. In SEM analysis, it was seen that the Au-IDE surface was smooth in contrast to the Anti-PT modified surface, which is supported by the AFM studies showing the surface roughness of ~2.02 nm for Au-IDE surface and ~15.86 nm for Anti-PT modified surface. Further, Fourier transform infra-red (FTIR) spectroscopic analysis confirms the immobilization of Anti-PT by the bond vibrations upon the successive modification of Au-IDE with -OH groups, amine groups after modifying with APTES, and the amide bond formation after incubation in Anti-PT antibody. Electrochemical impedance spectroscopy (EIS) was carried out for the electrochemical characterization and for testing the sensing performances of the fabricated electrode. The developed immuno-sensor provided a linear range of detection from 0.5 pg/L–1 µg/L, with a limit of detection (LoD) of 0.66 ng/L and sensitivity of 4.1 MΩ/ngL−1/cm2. The sensor response was also examined with real samples (pomegranate juice) with good accuracy, exhibiting a shelf life of 25 days. The miniaturized sensing platform, along with its better sensing performance, has huge potential to be integrated into portable electronics, leading to suitable field applications of pesticide screening devices. [ABSTRACT FROM AUTHOR]

Transparent electrodes (TEs) with high chemical stability and excellent flexibility are critical for flexible optoelectronic devices, such as photodetectors, solar cells, and light-emitting diodes. Ultrathin metal electrode (thickness less than 20 nm) has been a promising TE candidate, but the fabrication can only be realized by vacuum-based technologies to date, and require tedious surface engineering of the substrates, which are neither ideal for polymeric based flexible applications nor suitable for roll-to-roll large-scale manufacture. This paper presents high-performance nanostructured transparent metal electrodes formation via displacement–diffusion-etch (DDE) process, which enables the solution-processed sub-20-nm-thick ultrathin gold electrodes (UTAuEs) on a wide variety of hard and soft substrates. UTAuEs fabricated on flexible polyethylene terephthalate (PET) substrates show a high chemical/environmental stability and superior bendability to commercial flexible indium–tin-oxide (ITO) electrodes. Moreover, flexible organic solar cells made with UTAuEs show similar power conversion efficiency but much enhanced flexibility, in comparison to that of ITO-based devices. [ABSTRACT FROM AUTHOR]

A facile and sensitive approach is introduced to precisely determine trace amounts of prostate specific antigen (PSA) by gold nanostructures deposited on fluorine-doped tin oxide (FTO) electrodes. The gold electrode fabrication is carried out by integration of two techniques of vacuum-deposition and electrochemical growth. The electrode was successfully used as a label-free immunosensor for PSA determination in human serum samples. The dependency of the biosensor performance on various fabrication parameters have been investigated and the optimized fabrication rout has been specified. This label-free immunosensor presents a noticeable performance with a large range of linearity from 0.05 to 30 ng/mL, a low detection limit of 5.7 pg/mL, and a long-term stability of 4 weeks. The obtained results for PSA determination in real samples show a good agreement with ELISA results with less than 10% deviation. [ABSTRACT FROM AUTHOR]

Protein-based electronics is one of the growing areas of bio-nanoelectronics, where novel electronic devices possessing distinctive properties are being fabricated using specific proteins. Furthermore, if the bio-molecule is analysed amidst different electrodes, intriguing properties are elucidated. This research article investigates the electron transport properties of l-aspartic acid (i.e. l-amino acid) bound to symmetrical electrodes of gold, silver, copper, platinum and palladium employing NEGF-DFT approach using self-consistent function. The theoretical work function of different electrodes is calculated using local density approximation and generalized gradient approximation approach. The calculated work function correlates well with the hole tunneling barrier and conductance of the molecular device, which further authenticate the coupling strength between molecule and electrode. Molecule under consideration also exhibits negative differential resistance region and rectification ratio with all the different electrodes, due to its asymmetrical structure. The molecular device using platinum electrodes exhibits the highest peak to valley ratio of 1.38 and rectification ratio of 3.20, at finite bias. The switching characteristics of different molecular device are justified with detailed transmission spectra and MPSH. These results indicate that l-aspartic acid and similar biomolecule can be vital to the growth of Proteotronics. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Chemical analysis of single cells plays essential roles in both fundamental research and clinical applications. In this work, the electrochemiluminescence (ECL) generated at vertically aligned gold microtube electrode ensembles (MEEs) was applied for the local chemical sensing of single cells. Thanks to the structure of MEEs and the surface‐confined nature of ECL generation, the ECL is confined in single microtubes and the local variations of hydrogen peroxide concentration can be revealed by the changes of ECL signals at single MEEs. With this methodology, we studied the hydrogen peroxide efflux from single living cells, showing the subcellular heterogeneity in hydrogen peroxide release. With sufficient spatial resolution for the parallel single cell sensing as well as advantages including easy preparation and high throughput, the MEEs provide a promising platform for subcellular electroanalysis. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Chemical analysis of single cells plays essential roles in both fundamental research and clinical applications. In this work, the electrochemiluminescence (ECL) generated at vertically aligned gold microtube electrode ensembles (MEEs) was applied for the local chemical sensing of single cells. Thanks to the structure of MEEs and the surface‐confined nature of ECL generation, the ECL is confined in single microtubes and the local variations of hydrogen peroxide concentration can be revealed by the changes of ECL signals at single MEEs. With this methodology, we studied the hydrogen peroxide efflux from single living cells, showing the subcellular heterogeneity in hydrogen peroxide release. With sufficient spatial resolution for the parallel single cell sensing as well as advantages including easy preparation and high throughput, the MEEs provide a promising platform for subcellular electroanalysis. [ABSTRACT FROM AUTHOR]

Flexible polymer neural probes are an attractive emerging approach for invasive brain recordings, given that they can minimize the risks of brain damage or glial scaring. However, densely packed electrode sites, which can facilitate neuronal data analysis, are not widely available in flexible probes. Here, we present a new flexible polyimide neural probe, based on standard and low-cost lithography processes, which has 32 closely spaced 10 μm diameter gold electrode sites at two different depths from the probe surface arranged in a matrix, with inter-site distances of only 5 μm. The double-layer design and fabrication approach implemented also provides additional stiffening just sufficient to prevent probe buckling during brain insertion. This approach avoids typical laborious augmentation strategies used to increase flexible probes' mechanical rigidity while allowing a small brain insertion footprint. Chemical composition analysis and metrology of structural, mechanical, and electrical properties demonstrated the viability of this fabrication approach. Finally, in vivo functional assessment tests in the mouse cortex were performed as well as histological assessment of the insertion footprint, validating the biological applicability of this flexible neural probe for acquiring high quality neuronal recordings with high signal to noise ratio (SNR) and reduced acute trauma. [ABSTRACT FROM AUTHOR]

The asynchronous transient responses at the edge and center of a gold disk electrode are monitored by in situ differential reflectance spectroscopy (DRS). The DRS spectrum collected in 10 mM perchloric acid shows that the edge of the electrode achieves the equilibrium sooner than the center does in chronoamperometry, which establishes the foundation for a similar electrochemical protocol to remove the metallic Cu at the edge of a Cu/Au disk electrode while keeping these at the center intact. Both phenomena are caused by the larger resistance at the center than the edge of a disk electrode. [ABSTRACT FROM AUTHOR]

We immobilized unmodified, single-stranded (ss) DNA oligonucleotides on graphene oxide (GO) using divinyl sulfone (DVS). This is a new and useful method for generating DNA biosensors that avoids the need for modified oligonucleotides with synthetic attachment chemistry. This technique yields time and cost savings. The synthesis of unmodified oligonucleotides is simpler, quicker, and less expensive than modified DNA. DVS has two reactive vinyl groups that can link labile functional groups on the GO surface to the DNA. We show that the DNA nucleobase is covalently bonded to DVS. This opens the use of ubiquitous glassy carbon electrodes (GCE) for fabricating DNA biosensors by drop-casting GO. Reverse-complimentary DNA was detected using multiple electrochemical methods. The results show that DNA can be successfully conjugated to conductive carbon for electrochemical sensors. This is simpler than other methods for functionalizing carbon electrodes. This has clear advantages over gold electrodes in terms of its electrochemical potential window. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs)-based composite decorating with single-walled carbon nanohorns (SWCNHs) was synthesized and modified on a gold electrode for non-enzymatic glucose detection. The composite was synthesized by a simple covalent bonding method. The AuNPs with an average particle size of 40 nm are dispersed homogeneously on the surface of the SWCNHs. Therefore, the synergistic effect of the AuNPs and the SWCNHs leads to an excellent glucose sensing performance. The AuNPs/SWCNHs nanocomposites acted as a fast redox probe for non-enzymatic glucose oxidation exhibiting good performance, including a high sensitivity (275.33 and 352.5 μA cm−2 mM−1), a low detection limit of 0.72 μM (S/N = 3). AuNPs/SWCNHs glucose sensor also demonstrates good stability, reproducibility, and selectivity. Moreover, the glucose contents detected by this electrode was in right agreement with real value in blood samples. In summary, this study showed that AuNPs/SWCNHs nanoparticles have the potential to be used in non-enzymatic glucose detection. [ABSTRACT FROM AUTHOR]

Stable working voltage is critical for integrated systems to keep functioning, yet it suffered from instantaneous high-power demands and the resulting voltage disturbance. An on-chip micro supercapacitor (MSC) with superb capacitance density can act as a promising high-power supply unit to satisfy power demands and stabilize the system. However, severe capacitance decay of MSC under fast charge/discharge rate greatly weakens the device power output thus making it incompetent. This work demonstrates an on-chip high-power MSC featured by the improved capacitance density, fast charge/discharge ability and scaling-down capability. The improvement is brought by the applied mesoporous gold as electrode framework, which offers fast electronic/ionic pathway and reduces porous effect under high charge/discharge rate; as well as the uniform MnO2 active layer, which is decorated by an electrochemical potential-modulated deposition method, providing large pseudocapacitance. Moreover, the asymmetric electrode structure is constructed to expand the single device operation voltage. As a result, a large steady capacitance density of 9 mF/cm2 and small capacity loss of 28% at high scan rate of 1 V/s have been achieved, leading to an unprecedented power density of 138 mW/cm2 . [ABSTRACT FROM AUTHOR]

In this study the fundamental understanding of the underlying reactions of a possible Ca−O2 battery using a DMSO‐based electrolyte was strengthened. Employing the rotating ring disc electrode, a transition from a mixed process of O2− and O22− formation to an exclusive O2− formation at gold electrodes is observed. It is shown that in this system Ca‐superoxide and Ca‐peroxide are formed as soluble species. However, there is a strongly adsorbed layer of products of the oxygen reduction reaction (ORR) s on the electrode surface, which is blocking the electrode. Surprisingly the blockade is only a partial blockade for the formation of peroxide while the formation of superoxide is maintained. During an anodic sweep, the ORR product layer is stripped from the electrode surface. With X‐ray photoelectron spectroscopy (XPS) the deposited ORR products were shown to be Ca(O2)2, CaO2, and CaO as well as side‐reaction products such as CO32− and other oxygen‐containing carbon species. It is shown that the strongly attached layer on the electrocatalyst, that was partially blocking the electrode, could be adsorbed CaO. The disproportionation reaction of O2− in presence of Ca2+ was demonstrated via mass spectrometry. Finally, the ORR mediated by 2,5‐di‐tert‐1,4‐benzoquinone (DBBQ) was investigated by differential electrochemical mass spectrometry (DEMS) and XPS. Similar products as without DBBQ are deposited on the electrode surface. The analysis of the DEMS experiments shows that DBBQ− reduces O2 to O2− and O22−, whereas in the presence of DBBQ2− O22− is formed. The mechanism of the ORR with and without DBBQ is discussed. [ABSTRACT FROM AUTHOR]

The technique chosen to immobilise DNA onto electrodes can determine the density and stability of the resultant immobilised layer. DNA‐modified electrodes were prepared using four common DNA immobilisation methods and characterised using ferrocyanide. The negatively charged DNA strands should repel ferrocyanide anions. The DNA layers created using adsorption at glassy carbon electrodes were unstable, while those created through chemisorption of thiol‐modified DNA onto gold electrodes were repeatable and stable, and returned, on average, 94 % repulsion of the probe. The presented results show how the immobilisation protocol, and DNA type, affects the stability, repeatability, and integrity of resultant DNA layers. [ABSTRACT FROM AUTHOR]

Designing tunable molecular devices with different charge carriers in single-molecule junctions is crucial to the next-generation electronic technology. Recently, it has been demonstrated that the type of charge carriers depends on and can be tuned by controlling the molecular length and the number of interfacial covalent bonds. In this study, we show that the type of charge carriers can also be tuned by controlling the material and shape of electrodes. N-heterocyclic carbenes (NHCs) have attracted attention because of their ability to form strong, substitutional inert bonds in a variety of metals. Also, NHCs are more stable than the widely used thiol group. Therefore, we use electrodes to tune the type of charge carriers in a series of NHCs with different side groups. The ab initio calculations based on non-equilibrium Green's formalism combined with density functional theory show that the dominant charge carrier switches from electrons to holes when gold electrodes are changed into platinum ones. The nature of the charge carriers can be identified by variations in the transport spectra at the Fermi level (EF), which are caused by the side groups. The projections of transport spectra onto the central molecules further validate our inferences. In addition, the transmission coefficient at EF is found to be dependent on the atomic interface structure. In particular, for the NHC without methyl or ethyl side groups, connecting a protruding atom on the electrode surface significantly enhances the transportability of both electrode materials. Overall, this study presents an effective approach to modifying transport properties, which has potential applications in designing functional molecular devices based on NHCs. [ABSTRACT FROM AUTHOR]

Aminoquinolines are widely used as antimalarial drugs and thus there is an ever increasing demand for their determination. In this paper, non‐traditional carbon film electrode developed in our laboratory (CFE) with easily replaceable carbon film was used for the determination of 5‐aminoquinoline (5‐AQ) and compared with well‐established commercially available carbon screen printed electrode (CSPE) and gold screen printed electrode (AuSPE). Electrochemical behavior of 5‐AQ was characterized by cyclic and differential pulse voltammetry. Differences in electrochemical behavior of 5‐AQ at different electrodes were evaluated. Determination of 5‐AQ was carried out by differential pulse, square wave, and direct current voltammetry. Practical applicability of the method was verified by direct determination of 5‐AQ in model samples of drinking and river water. Achieved limits of quantitation were in submicromolar concentrations. It was found out that novel CFE in terms of overall performance is in most aspects superior to routinely used commercially available CSPE and AuSPE. [ABSTRACT FROM AUTHOR]

A novel electrochemical impedance spectroscopy (EIS) sensor design, based on a standard interdigitated electrode arrangement in which the working electrode consists of gold and the combined counter and reference electrodes of polypyrrole doped with polystyrene sulfonate (PPy:PSS), is evaluated for biosensing applications. The performance is successfully proved by immobilization of a thiolated biotin as a self‐assembled monolayer (SAM), followed by streptavidin and a biotinylated horseradish peroxidase. It is shown that specific binding of biomolecules takes place only at the gold electrode. The binding activities are not influenced by the addition of small amounts of the nonionic surfactant Pluronic F‐68. The immobilization process is monitored online with EIS showing an excellent repeatability of the EIS signals in comparison with Au–Au electrode configuration even after electrode regeneration. [ABSTRACT FROM AUTHOR]

Immunoassay plays an important role in the early screening and diagnosis of diseases. The use of electrochemical methods to realize the label-free, specific and rapid detection of antigens has attracted extensive attention from researchers. In this study, we realized the function of immunosensing and detection by lithography, the interdigitated gold electrode on the polyethylene naphthalate (PEN) membrane. Then, the gold electrode was biofunctionalized and the characterization was verified by atomic force microscopy, which was finally for the detection of mice IgG. This immunosensor has a low detection limit, with a broad linear detection range of 0.01–10 ng/mL. The results show that the electrochemical impedance sensor made of metal electrodes based on PEN flexible materials is suitable for immunoassay experiments. If this method could be proved by further studies, broad application prospects can be seen in routine immunoassays. [ABSTRACT FROM AUTHOR]

Tumor-treating fields (TTFields) are alternating electrical fields of intermediate frequency and low intensity that can slow or inhibit tumor growth by disrupting mitosis division of cancerous cells through cell cycle proteins. In this work, for the first time, an in-house fabricated cyclo-olefin polymer made microfluidic bioreactors are integrated with Cr/Au interdigitated electrodes to test TTFields on yeast cells with fluorescent protein:Nop56 gene. A small gap between electrodes (50 μm) allows small voltages (<150 mV) to be applied on the cells; hence, uninsulated gold electrodes are used in the non-faradaic region without causing any electrochemical reaction at the electrode-medium interface. Electrochemical modeling as well as impedance characterization and analysis of the electrodes are done using four different cell nutrient media. The experiments with yeast cells are done with 150 mV, 150 kHz and 30 mV, 200 kHz sinusoidal signals to generate electrical field magnitudes of 6.58 V/cm and 1.33 V/cm, respectively. In the high electrical field experiment, the cells go through electroporation. In the experiment with the low electrical field magnitude for TTFields, the cells have prolonged mitosis from typical 80–90 min to 200–300 min. Our results confirm the validity of the electrochemical model and the importance of applying a correct magnitude of the electrical field. Compared to the so far reported alternatives with insulated electrodes, the here developed thermoplastic microfluidic bioreactors with uninsulated electrodes provide a new, versatile, and durable platform for in vitro cell studies toward the improvement of anti-cancer therapies including personalized treatment. [ABSTRACT FROM AUTHOR]

• Synthesized and characterized lysine oxidase nanoparticles (LOxNPs). • Fabricated an amperometric lysine biosensor based on LOxNPs/Au electrode. • Response time and LOD of biosensor was 3.5 s and 10 µM respectively. • Biosensor was applied for determination of lysine in serum samples, milk samples and pharmaceutical tablet. • Working electrode lost 14% of original activity after 200 days stored at 4 °C. The fabrication of an amperometric lysine biosensor is described in this study, wherein nanoparticles (NPs) of lysine oxidase (LOx) are covalently immobilized onto gold electrode (AuE). The LOxNPs were prepared by desolvation method and characterized by UV Vis spectroscopy, Fourier transform infra red (FTIR) spectroscopy and transmission electron microscopy (TEM). The LOxNPs/AuE modified working electrode was studied by scanning electron microscope (SEM) and cyclic voltammetric (CV) techniques. The electrode exhibited optimum current within 3.5 s at applied potential, 0.8 V, pH 6.5 and temperature, 35 °C. The sensor displayed a linear relationship between lysine concentration and current in the range 10–800 µM with a limit of detection of 10 µM. Within assay and between batch coefficients of variation were 0.0751% and 0.0637% respectively. The analytical recoveries of added lysine at 10 µM and 20 µM in sera were 98.39% and 98.23% respectively. There was a good correlation between level of lysine in sera and milk samples (R2 = 0.999 and R2 = 0.98 respectively) as determined by the standard spectrophotometric method and the present method. The biosensor measured lysine levels in milk, pharmaceutical tablet and sera of healthy individuals and cancer patients. The biosensor showed slight interference by common interferents found in serum. [ABSTRACT FROM AUTHOR]

Poly(3,4‐ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS) is widely used as a coating on microelectrode arrays in order to reduce impedance for both in vitro and in vivo electrophysiology. In many applications, electrode performance of months to years is desired; yet, there are few studies to date that examine the long‐term stability of conducting polymers and their devices. Here, the stability of PEDOT:PSS microelectrodes is examined over a period of four months in cell culture media enriched with fetal bovine serum. The electrochemical impedance remains constant for most electrodes throughout the study, and only small changes in the structure of functional electrodes are observed. The results demonstrate that PEDOT:PSS electrodes show adequate stability for a variety of in vitro electrophysiology applications in toxicology, drug development, tissue engineering, and fundamental studies of electrically active cells and tissues. [ABSTRACT FROM AUTHOR]

A simple and fast electrochemical method was described and evaluated to determine the hazardous compound, 4‐nitrophenol (4NP). In this work, concentration of 4NP was determined by differential wave voltammetry (DPV). A gold electrode (Au) was modified with 3,5‐diamino‐1,2,4‐triazole (35DT). The modified electrode (35DT‐Au) was characterized by using electrochemical impedance spectroscopy (EIS), fouirer transform infrared spektrofotometre (FTIR), cyclic voltammetry (CV) and DPV. The modified electrode showed more sensitivity towards 4NP compared to unmodified one. A wide linear concentration range from 0.24 to 130.6 μM was obtained for 4NP with a detection limit of 0.09 μM. In the reproducibility and repeatability studies, the relative standard deviation (RSD%) values of the method were obtained as 3.72 % and 2.56 %, respectively, which are acceptable values. This proposed method was successfully used for the analysis of 4NP in lake and tap water samples. Simplicity, sensitivity, selectivity and high efficiency of the proposed method can be used in routine analysis of trace amounts of 4NP in polluted waters. [ABSTRACT FROM AUTHOR]