Electrochemical Detection of Nucleic Acids Using Three-Dimensional Graphene Screen-Printed Electrodes.

Electrochemical approaches, along with miniaturization of electrodes, are increasingly being employed to detect and quantify nucleic acid biomarkers. Miniaturization of the electrodes is achieved through the use of screen-printed electrodes (SPEs), which consist of one to a few dozen sets of electrodes, or by utilizing printed circuit boards. Electrode materials used in SPEs include glassy carbon (Chiang H-C, Wang Y, Zhang Q, Levon K, Biosensors (Basel) 9:2-11, 2019), platinum, carbon, and graphene (Cheng FF, He TT, Miao HT, Shi JJ, Jiang LP, Zhu JJ, ACS Appl Mater Interfaces 7:2979-2985, 2015). There are numerous modifications to the electrode surfaces as well (Cheng FF, He TT, Miao HT, Shi JJ, Jiang LP, Zhu JJ, ACS Appl Mater Interfaces 7:2979-2985, 2015). These approaches offer distinct advantages, primarily due to their demonstrated superior limit of detection without amplification. Using the SPEs and potentiostats, we can detect cells, proteins, DNA, and RNA concentrations in the nanomolar (nM) to attomolar (aM) range. The focus of this chapter is to describe the basic approach adopted for the use of SPEs for nucleic acid measurement.

The smallest electrochemical bubbles.

Many of the relevant electrochemical processes in the context of catalysis or energy conversion and storage, entail the production of gases. This often implicates the nucleation of bubbles at the interface, with the concomitant blockage of the electroactive area leading to overpotentials and Ohmic drop. Nanoelectrodes have been envisioned as assets to revert this effect, by inhibiting bubble formation. Experiments show, however, that nanobubbles nucleate and attach to nanoscale electrodes, imposing a limit to the current, which turns out to be independent of size and applied potential in a wide range from 3 nm to tenths of microns. Here we investigate the potential-current response for disk electrodes of diameters down to a single-atom, employing molecular simulations including electrochemical generation of gas. Our analysis reveals that nanoelectrodes of 1 nm can offer twice as much current as that delivered by electrodes with areas four orders of magnitude larger at the same bias. This boost in the extracted current is a consequence of the destabilization of the gas phase. The grand potential of surface nanobubbles shows they can not reach a thermodynamically stable state on supports below 2 nm. As a result, the electroactive area becomes accessible to the solution and the current turns out to be sensitive to the electrode radius. In this way, our simulations establish that there is an optimal size for the nanoelectrodes, in between the single-atom and ∼3 nm, that optimizes the gas production.

Preparation and Performance Investigation of Carbon-Coated Li1.2Mn0.2Ti0.6O2/C Cathode Materials.

Mn-based cation disordered rock-salt (DRX) cathode materials exhibit promising application prospects due to their cost-effectiveness and high specific capacity. However, the synthesis methods commonly employed for these materials rely on the solid-state reaction method and mechanochemistry method, primarily attributed to the influence of low-valence states of Mn. Currently, sol-gel approaches for preparing Mn-based DRX cathode materials are limited to systems involving Mn3+. Furthermore, there is a paucity of research regarding the modification of Mn-based DRX. To address this concern, the submicrometer-sized carbon-coated Li1.2Mn0.2Ti0.6O2/C materials were synthesized via a one-step sintering process using the sol-gel method with sucrose as the carbon source, resulting in smaller particle sizes compared to those prepared by the solid-state reaction at the same temperature. When employed as a cathode material for lithium batteries, samples prepared with 10 wt % sucrose exhibited exceptional cycling stability by delivering an initial discharge specific capacity of 119.6 mA h g-1 (at a current density of 20 mA g-1). After 20 charge-discharge cycles, a reversible specific capacity of 91.0 mA h g-1 was achieved, with a capacity retention rate of 76.1%. This approach provides distinctive insights and strategies for the preparation and modification of manganese-titanium-based disordered rock-salt cathode materials.

Research progress of high-entropy oxides for electrocatalytic oxygen evolution reaction.

High-entropy oxides (HEOs), similar to high-entropy materials (HEMs), have "four-core effects", i.e., high-entropy effect, delayed diffusion effect, lattice distortion effect and cocktail effect, which have attracted more and more attention in the scientific field of renewable energy technology due to their unique structural characteristics, variable chemical composition and corresponding functional properties. HEOs have become potential candidates for electrocatalytic oxygen evolution reaction (OER), which is a key half reaction for electrolytic CO2, nitrogen reduction, and water electrolysis. However, the precise synthesis of HEOs with a wide range of components and structures is challenging, not to mention their active and stable operation for OER. In this paper, we review the recent advancements in the electrocatalytic oxygen evolution facilitated by HEOs in water electrolysis. We analyze these developments from the perspectives of activity and stability in acid and alkaline conditions, respectively. Furthermore, we summarize the design from the aspect of element composition, structure, morphology, and catalyst-support interactions, along with related reaction mechanism of HEOs. Additionally, we discuss the current challenges faced by HEOs in the field of OER and suggest potential directions for the future development of HEOs beyond water electrolysis application.

Single Atom Catalyst for Nitrate-to-Ammonia Electrochemistry.

Various life forms suffer from the negative effects of nitrate when it accumulates in water bodies, which is a major concern in the present day. The removal of nitrate from water bodies is a critical challenge, and the most effective method to achieve that is to change it into ammonia. Ammonia is a clean energy source and a vital input for the fertilizer industry. The Haber-Bosch process, which dominates the industrial production of ammonia, requires a lot of energy. A more sustainable way to produce ammonia is to use nitrate-contaminated water and reduce it to ammonia through electrocatalysis. This review is constituted of amalgamated articles featuring unique conditions that affect the productivity and activity of the transition metal single atom catalyst (TNMSAC) for the electrocatalytic nitrate reduction to ammonia (NRA) reaction. It explores factors such as nitrate ion adsorption, the characteristics of the central electroactive transition metal, the type of coordinating atoms, the impact of potential on stability, and the interplay among single atoms on the selectivity and yield of ammonia gas. In addition, this review also covers advanced concepts such as dual-atom catalysts, dual single atom catalysts, and single atom alloys. The review will provide valuable guidance for enhanced comprehension and strategic designing of TNMSAC for the electrocatalytic conversion of NRA, which will contribute to achieving a green ammonia economy.

Shattering the Water Window: Comprehensive Mapping of Faradaic Reactions on Bioelectronics Electrodes.

It is generally accepted that for safe use of neural interface electrodes, irreversible faradaic reactions should be avoided in favor of capacitive charge injection. However, in some cases, faradaic reactions can be desirable for controlling specific (electro)physiological outcomes or for biosensing purposes. This study aims to systematically map the basic faradaic reactions occurring at bioelectronic electrode interfaces. We analyze archetypical platinum-iridium (PtIr), the most commonly used electrode material in biomedical implants. By providing a detailed guide to these reactions and the factors that influence them, we offer a valuable resource for researchers seeking to suppress or exploit faradaic reactions in various electrode materials. We employed a combination of electrochemical techniques and direct quantification methods, including amperometric, potentiometric, and spectrophotometric assays, to measure O2, H2, pH, H2O2, Cl2/OCl-, and soluble platinum and iridium ions. We compared phosphate-buffered saline (PBS) with an unbuffered electrolyte and complex cell culture media containing proteins. Our results reveal that the "water window"─the potential range without significant water electrolysis─varies depending on the electrolyte used. In the culture medium that is rich with redox-active species, a window of potentials where no faradaic process occurs essentially does not exist. Under cathodic polarizations, significant pH increases (alkalization) were observed, while anodic water splitting competes with other processes in media, preventing prevalent acidification. We quantified the oxygen reduction reaction and accumulation of H2O2 as a byproduct. PtIr efficiently deoxygenates the electrolyte under low cathodic polarizations, generating local hypoxia. Under anodic polarizations, chloride oxidation competes with oxygen evolution, producing relatively high and cytotoxic concentrations of hypochlorite (OCl-) under certain conditions. These oxidative processes occur alongside PtIr dissolution through the formation of soluble salts. Our findings indicate that the conventional understanding of the water window is an oversimplification. Important faradaic reactions, such as oxygen reduction and chloride oxidation, occur within or near the edges of the water window. Furthermore, the definition of the water window significantly depends on the electrolyte composition, with PBS yielding different results compared with culture media.

Electrochemical oxidation of UV filters: A first-principles molecular dynamics study.

A theoretical model is proposed to study the oxidation mechanisms of the organic UV filters BP3 and BP4 during electrochemical water treatment utilizing Car-Parrinello molecular dynamics. Factors such as the amount of solvent to be included and how to design the system with the least possible intervention are discussed. The stages of the proposed model consist of the optimization of the geometries by density functional theory methods, the equilibration of the structure immersed in a water box, the inclusion of the reactive species, and the analysis of the reaction energies of each reaction pathway. The ab-initio molecular dynamics simulations lead to several products, and some trends can be identified, in accordance with the well-known reactivity rules of organic chemistry. The products proposed in this work are intermediates in longer oxidative pathways.

Conductive Polypropylene Additive Manufacturing Feedstock: Application to Aqueous Electroanalysis and Unlocking Nonaqueous Electrochemistry and Electrosynthesis.

Additive manufacturing electrochemistry is an ever-expanding field; however, it is limited to aqueous environments due to the conductive filaments currently available. Herein, the production of a conductive poly(propylene) filament, which unlocks the door to organic electrochemistry and electrosynthesis, is reported. A filament with 40 wt % carbon black possessed enhanced thermal stability, excellent low-temperature flexibility, and high conductivity. The filament produced highly reproducible additive manufactured electrodes that were electrochemically characterized, showing a k0 of 2.00 ± 0.04 × 10-3 cm s-1. This material was then applied to three separate electrochemical applications. First, the electroanalytical sensing of colchicine within environmental waters, where a limit of detection of 10 nM was achieved before being applied to tap, bottled, and river water. Second, the electrodes were stable in organic solvents for 100 cyclic voltammograms and 15 days. Finally, these were applied toward an electrosynthetic reaction of chlorpromazine, where the electrodes were stable for 24-h experiments, outperforming a glassy carbon electrode, and were able to be reused while maintaining a good electrochemical performance. This material can revolutionize the field of additive manufacturing electrochemistry and expand research into a variety of new fields.

Software Integrated Personalized Biosensing Device for Serum Creatinine Detection Based on Boron doped MXene Nanohybrid.

In recent years, an increase in the number of chronic kidney disease (CKD) cases has led to a global health burden majorly affecting underdeveloped and developing nations. A key biomarker for assessing the kidneys' normal functioning is creatinine, which is filtered out from the blood by the kidney. Thus, timely and specific detection of creatinine becomes necessary for diagnosis and subsequent treatment of CKD. Hence, in this study, we have tried to develop a field-deployable, software-integrated immunosensor for the detection of creatinine in a serum sample. The immunosensor was developed by incorporating gold nanoparticles, boron doped MXene, polyaniline, and anticreatinine antibody using an appropriate bioconjugation reaction. The developed sensor was able to detect creatinine in a linear dynamic range of 10 nM to 0.1 M with a limit of detection of 1.72 (±0.07) nM. The sensor was integrated with an indigenously developed software named "CretCheck" which simplifies the process of data analysis. The software integrated personalized biosensing device was used to find the creatinine concentrations directly from the obtained analytical signals. The developed immunosensor with the integrated software can also be implemented directly in primary health care facilities for creatinine detection in the future.

Synthesis and Electrochemical Study of Gold(I) Carbene Complexes.

In this work, we have prepared and characterized some gold compounds wearing a N-heterocyclic carbene (NHC) ligand as well as alkynyl derivatives with different substituents. The study of their electrochemical behavior reveals that these complexes show an irreversible wave at potentials ranging between -2.79 and -2.91 V, referenced to the ferrocenium/ferrocene pair. DFT calculations indicate that the reduction occurs mainly on the aryl-C≡C fragment. The cyclic voltammetry experiments under CO2 atmosphere show an increase in the faradaic current of the reduction wave compared to the experiments under argon atmosphere, indicating a possible catalytic activity towards the carbon dioxide reduction reaction (CO2RR).

A self-powered and self-monitoring ultra-low frequency wave energy harvester for smart ocean ranches.

The ocean ranch environment contains ultra-low-frequency wave energy that can be utilized for powering low-power equipment. Therefore, this article proposes a smart ocean ranch self-powered and self-monitoring system (SOR-SSS) which consists of several key components: a mass pendulum ball (MPB), a commutation wheel system (CWS), an electromagnetic energy harvesting unit (EEHU), and four piezoelectric energy harvesting units (PEHU). Through six-degree-of-freedom vibration test bench experiments, the SOR-SSS achieved a maximum output power of 17.56 mW under a working condition of 0.4 Hz, which was sufficient to power 152 LED lights. Additionally, by training the experimental base data using the LSTM algorithm, two different tasks were trained with a maximum accuracy of 99.72% and 99.80%, respectively. These results indicate that the SOR-SSS holds significant potential for collecting and predicting ultra-low-frequency blue energy. It can provide an effective energy supply and monitoring solution for smart ocean ranch.

1,4-Benzodioxane substituted aza-BODIPY: towards photostable yet efficient triplet photosensitizer.

We report herein the synthesis of aza-BODIPY substituted with 1,4-benzodioxane-6-yl substituents at 3,5 positions of the chromophore system. Both pyrrole rings of the aza-BODIPY in question were substituted with bromine atoms in order to induce highly desirable photophysical properties, such as highly populated excited triplet state (T1) and long excited triplet-state lifetime (τT) of 21 µs. The photosensitized oxygenation of a model compounds, viz. DPBF, points to a high singlet oxygen and/or other ROS formation quantum yield of 0.42. The photosensitizer studied exhibited an absorption band within the so-called "therapeutic window", with λabs 678 nm. As estimated by CV/DPV measurements the 1,4-benzodioxane-6-yl substituted aza-BODIPYs studied exhibited a multi-electron oxidations at a relatively low potentials (Eox), pointing to the very good electron-donating properties of these molecules. High photostability and thermal stability was observed for all compounds studied. The good singlet oxygen quantum yield measured combined with an exceptional photostability makes this aza-BODIPY a promising candidate for applications such as photocatalysis and photodynamic therapy (PDT).

Bipolar electrochemical growth of conductive microwires for cancer spheroid integration: a step forward in conductive biological circuitry.

The field of bioelectronics is developing exponentially. There is now a drive to interface electronics with biology for the development of new technologies to improve our understanding of electrical forces in biology. This builds on our recently published work in which we show wireless electrochemistry could be used to grow bioelectronic functional circuitry in 2D cell layers. To date our ability to merge electronics with in situ with biology is 3D limited. In this study, we aimed to further develop the wireless electrochemical approach for the self-assembly of microwires in situ with custom-designed and fabricated 3D cancer spheroids. Unlike traditional electrochemical methods that rely on direct electrical connections to induce currents, our technique utilises bipolar electrodes that operate independently of physical wired connections. These electrodes enable redox reactions through the application of an external electric field. Specifically, feeder electrodes connected to a power supply generate an electric field, while the bipolar electrodes, not physically connected to the feeder electrodes, facilitate the reduction of silver ions from the solution. This process occurs upon applying a voltage across the feeder electrodes, resulting in the formation of self-assembled microwires between the cancer spheroids.Thereby, creating interlinked bioelectronic circuitry with cancer spheroids. We demonstrate that a direct current was needed to stimulate the growth of conductive microwires in the presence of cell spheroids. Microwire growth was successful when using 50 V (0.5 kV/cm) of DC applied to a single spheroid of approximately 800 µm in diameter but could not be achieved with alternating currents. This represents the first proof of the concept of using wireless electrochemistry to grow conductive structures with 3D mammalian cell spheroids.

Investigating perimidine precursors for the synthesis of new multiredox polymers.

We present a new simple approach for electrochemical synthesis of semi-condensed ambipolar perinone polymers with phthaloperine (p1) or phenanthroline (p2) skeleton from available and cheap perimidine precursors. Polymerization of perimidine derivatives varies in efficiency depending on the monomer, but overall is highly efficient, especially when electropolymerization is used. Electrooxidation is well controllable and provides a certain characteristic share of new bonds in the structure of perimidine polymers: semi-ladder bis-perimidine unit, ladder bis-perimidine unit, and protonated bis-perimidine unit. Polymer p2 obtained with higher efficiency was put through broader analysis (UV-Vis, IR, ESR and quantum-chemical calculations). As indicated, donor-acceptor structure and specific intermolecular interactions of p2 assure its electrical conductivity and complex redox activity. Although protonated bonds break π-conjugation in the structure of the macromolecule, there is also a diradical state that favors intermolecular interactions and intermolecular π-conjugation channels within bis-perimidine segments. It has been proven that there is a diradical state which appears as an intermediate state between the oxidized and reduced states of the protonated polymer unit. This work positions perimidine polymers as a versatile ambipolar multiredox p- and n-type conductor, indicating a potential for expanding perinone-based perylene-diperimidine polymers for innovative electronics and (bio)sensors.

Elucidating charge transfer process and enhancing electrochemical performance of laser-induced graphene via surface engineering with sustainable hydrogel membranes: An electrochemist's perspective.

Laser-induced graphene (LIG) has emerged as a promising solvent-free strategy for producing highly porous, 3D graphene structures, particularly for electrochemical applications. However, the unique character of LIG and hydrogel membrane (HM) coated LIG requires accounting for the specific conditions of its charge transfer process. This study investigates electron transfer kinetics and the electroactive surface area of LIG electrodes, finding efficient kinetics for the [Fe(CN)6]3-/4- redox process, with a high rate constant of 4.89 x 10-3 cm/s. The impact of polysaccharide HM coatings (cationic chitosan, neutral agarose and anionic sodium alginate) on LIG's charge transfer behavior is elucidated, considering factors like ohmic drop across porous LIG and Coulombic interactions/permeability affecting diffusion coefficient (D), estimated from amperometry.It was found that D of redox species is lower for HM-coated LIGs, and is the lowest for chitosan HM. Chitosan coating results in increased capacitive share in the total current while does not apparently reduce Faradaic current. Experimental findings are supported by ab-initio calculations showing an electrostatic potential map's negative charge distribution upon chitosan chain protonation, having an effect in over a two-fold redox current increase upon switching the pH from 7.48 to 1.73. This feature is absent for other studied HMs. It was also revealed that the chitosan's band gap was reduced to 3.07 eV upon acetylation, due to the introduction of a new LUMO state. This study summarizes the operating conditions enhanced by HM presence, impacting redox process kinetics and presenting unique challenges for prospective LIG/HM systems' electrochemical applications.

Biomolecular condensates regulate cellular electrochemical equilibria.

Control of the electrochemical environment in living cells is typically attributed to ion channels. Here, we show that the formation of biomolecular condensates can modulate the electrochemical environment in bacterial cells, which affects cellular processes globally. Condensate formation generates an electric potential gradient, which directly affects the electrochemical properties of a cell, including cytoplasmic pH and membrane potential. Condensate formation also amplifies cell-cell variability of their electrochemical properties due to passive environmental effect. The modulation of the electrochemical equilibria further controls cell-environment interactions, thus directly influencing bacterial survival under antibiotic stress. The condensate-mediated shift in intracellular electrochemical equilibria drives a change of the global gene expression profile. Our work reveals the biochemical functions of condensates, which extend beyond the functions of biomolecules driving and participating in condensate formation, and uncovers a role of condensates in regulating global cellular physiology.

Aqueous Electrochemical Direct Air Capture Using Alizarin Red S.

irect Air Capture (DAC) is an emerging form of atmospheric carbon dioxide removal. Conventional DAC sorbents utilize swings in temperature and/or pressure, which are energy intensive and hinders large-scale deployment. In this work, we demonstrate a green, aqueous electrochemical DAC system that employs Alizarin Red S (ARS) as an electroactive capturing agent. The system has an estimated minimum theoretical energy requirement of 24.6 kJe/mole of CO2, demonstrated reversible electrochemical behavior over 100 cycles and 205 hours, and maintained an average coulombic efficiency of 100% with an average capacity retention of 99.8%. With a techno-economic analysis, we highlight the impact of current density and electrode surface area on levelized costs, and we describe a path to lower the cost of DAC below US$500 per tonne of CO2.

Antinociceptive, anti-inflammatory, and antioxidant effects of a flavonoid-rich phytocomplex from the leaves of Celtis iguanaea (jacq.) Sargent (Cannabaceae).

We demonstrated the antinociceptive and anti-inflammatory effects of the ethyl acetate leaf extract of Celtis iguanaea (Jacq.) Sargent (EAECi) in mice. The in vitro antioxidant activity of EAECi and its phytoconstituents was also investigated. The antinociceptive effect of EAECi is attributed to its anti-inflammatory activity, as evidenced by its anti-hyperalgesic and antiedematogenic effects. EAECi reduced polymorphonuclear cell migration, myeloperoxidase activity, pro-inflammatory cytokines (TNF-α and IL-1ß), and PGE2 levels. The levels of anti-inflammatory cytokines (IL-4 and IL-10) were increased compared to the vehicle-treated groups. The overall antioxidant capacity of EAECi is noteworthy, with the Electrochemical Index determined by Differential Pulse Voltammetry being 42.7 µA/V. Concurrently, Square Wave Voltammetry revealed the reversibility of the redox process (Ep1a/Ep1c) at 0.254 V. The presence of twenty-six phytochemicals, primarily flavone aglycones, was suggested by paper-spray mass spectrometry. These findings represent a step towards validating C. iguanaea leaf extract for treating acute inflammatory conditions.

Platinum nanoparticles-based electrochemical H2O2 sensor for rapid antibiotic susceptibility testing.

With the increase of antimicrobial resistance, rapid antibiotic susceptibility testing (AST) to guide precise antibiotic administration has become increasingly important. However, current gold standard AST approaches tend to take up to 24-48 h. In this work, based on the nature of catalase-positive bacteria decomposing H2O2, we developed a rapid, portable, straightforward, and cost-effective phenotypic AST approach by detecting residual H2O2 using a Pt nanoparticles-based electrochemical sensor. The pulse current of the sensor exhibited a linear increase with rising H2O2 concentration, demonstrating a high sensitivity of ∼382.2 µA cm-2 mM-1. This approach showed superb diagnostic performance, with an area under the curve of 1 for 24 clinical samples of Escherichia coli and Staphylococcus aureus, with a total detection time of 60 and 45 min, respectively. Furthermore, the performance of the sensor showed no degradation even after 100 detections, promising a substantial reduction in AST costs. Overall, the proposed approach exhibited immense potential for diagnosing bacterial antibiotic resistance.

Identification of transformation products from fluorinated lithium-ion battery additives TPFPB and TPFPP: forever chemicals of tomorrow?

Fluorinated organic compounds (FOCs) represent a class of synthetic chemicals distinguished by their resilient carbon-fluorine bonds, which demonstrate an ability to withstand environmental degradation over an extended period. The integration of FOCs into cutting-edge applications, including lithium-ion batteries (LiBs), presents considerable potential for environmental harm that has not yet been sufficiently addressed. This study focuses on the environmental fate of two fluorinated aromatics, tris(pentafluorophenyl)borane (TPFPB) and tris(pentafluorophenyl)phosphine (TPFPP), given their important role in improving the performance of LiBs. To achieve this, laboratory simulation methods including total oxidizable precursor assay, electrochemistry (EC), Fenton reaction, UV-C irradiation, and hydrolysis were employed. Liquid chromatography and gas chromatography coupled with high-resolution mass spectrometry were used for identification of transformation products (TPs) and prediction of their molecular formulae. Despite the structural similarity between TPFPB and TPFPP, distinct differences in electrochemical behavior and degradation pathways were observed. TPFPB readily underwent hydroxylation and hydrolysis, resulting in a wide range of 49 TPs. A total of 28 TPs were newly identified, including oligomers and highly toxic dioxins. In contrast, TPFPP degraded exclusively under harsh conditions, requiring the development of innovative conditioning protocols for EC. In total, the simulation experiments yielded nine structurally different compounds, including seven previously undescribed, partially defluorinated TPs. This study highlights the potential risks associated with the use of FOCs in LiBs and provides insight into the complex environmental behavior of FOCs.