Bipolar Supercapacitive Performance of N-Containing Carbon Materials Derived from Covalent Triazine-Based Framework.

The search for new electrode materials for bipolar-supercapacitor performance is the intention of numerous research in the area of functional framework materials. Among various electrode materials, covalent triazine-based frameworks (CTFs) are in the spotlight drawing much attention as potential electrode material for energy storage. Herein, we present the synthesis of nitrogen-functionalized CTFs marked as CTF-Py-600 and CTF-Py-700 with high nitrogen content (18% and 14%, respectively) for supercapacitor application by applying 2,6-dicyanopyridine monomer via the polymerization reaction under ionothermal condition. The BET surface area of these materials are in the range of 940-1999 m2g-1. CTF-Py-700 demonstrates outstanding electrochemical performance in both potential windows. At the negative potential window, it exhibits a higher specific capacitance of 435 F g-1 (at 1 A g-1) compared to the positive potential window, where it shows a specific capacitance of 306 F g-1 (at 1 A g-1) owing to the synergistic existence of its large surface area (1999 m2g-1) and high nitrogen content (14%) with inherent microporosity. Remarkable cycling stability without noticeable degradation of specific capacitance after 15000 cycles was recorded for CTF-Py-700. This suggests that the nitrogen-functionalized CTFs are going to be a highly demanded electrode material for electrochemical energy storage applications.

Effect of the alkyl chain length of α,ω-dichloroalkane on the Gibbs energy of transfer for functional groups.

Ion-transfer reactions of alkyl and perfluoroalkyl carboxylate ions (CH3(CH2)n-2COO- with n = 8-12 and CF3(CF2)n-2COO- with n = 3-9) were investigated at the polarized Cl-(CH2)m-Cl with m = 2, 4, 6, and 8 (O) | water (W) interface to evaluate the effects of n and m on the solvation energy of the ions, as well as on their methylene and terminal groups. These ions exhibited reversible or quasi-reversible voltammetric waves due to their transfer across the O | W interfaces, enabling the determination of formal potentials and formal Gibbs transfer energies from O to W, Δ G tr,o → w 0 ' The Δ G tr,o → w 0 ' values for CH3(CH2)n-2COO- and CF3(CF2)n-2COO- increased linearly with n, allowing the estimation of Δ G tr,o → w 0 ' for methylene and difluoromethylene groups, Δ G tr,o → w 0 ' (CH2) and Δ G tr,o → w 0 ' (CF2), and for their terminal groups, Δ G tr,o → w 0 ' (COO- + CH3) and Δ G tr,o → w 0 ' (COO- + CF3). Whereas the Δ G tr,o → w 0 ' (CH2) and Δ G tr,o → w 0 ' (CF2) hardly changed with the variation in m, the Δ G tr,o → w 0 ' (COO- + CH3) and Δ G tr,o → w 0 ' (COO- + CF3) decreased noticeably. These results suggest that the solvation energy for ions in Cl-(CH2)m-Cl increases with m, regardless of hydrophilic or lipophilic nature of the ions. Based on these findings, the advantage of using Cl-(CH2)m-Cl with a large m as a non-aqueous solvent for ion-transfer voltammetry was discussed.

CRISPR-Based Electrochemical Biosensors For Animal Health: Recent Advances.

Animal diseases are a major concern to animal welfare, human health and the global economy. Early detection, prevention and control of these animal diseases are crucial to ensure sustainability of livestock sector, to reduce farm losses and protecting public health. Points of care (POC) devices are small, portable instruments that provide rapid results thus reduce the risk of disease transmission and enable early intervention. CRISPR based diagnostics offer more accurate and efficient solution for monitoring animal health due to their quick response, can detect very low level of pathogenic organism or disease markers and specificity. These diagnostics are particularly useful in the in area with limited resources or access to common diagnostic methods, especially in developing countries. The ability of electrochemical sensors to detect accurately very low analyte concentration makes them suitable for POC diagnostics and field application. CRISPR base electrochemical biosensors show great potential in revolutionizing disease detection and diagnosis including animal health. However, challenges, such as achieving selectivity and sensitivity, need to be addressed to enhance the competitiveness of these biosensors. Currently, most CRISPR based bioassay research focuses on nucleic acid target detection, but researchers exploring to monitor small organic/ inorganic non-nucleic acid molecules like toxins and proteins. Emerging diagnostics would be centered on CRISPR-Cas system will offer great potential as an accurate, specific and effective means to identify microorganism, virus, toxins, small molecules, peptides and nucleic acid related to various animal health disorders particularly when integrated into electrochemical biosensing platform.

Rapid detection of tertiary butylated hydroquinone in food samples using Mn-MOF@f-CNF composite-modified screen-printed electrode.

Hydroquinone-based organic molecules are often used as unavoidable preservatives in the food industry. Among these additives, tertiary butylated hydroquinone (TBHQ) is widely employed as a preservative in various processed foods. However, the potential health risks associated with the excessive presence of TBHQ in food products have raised significant concerns. To address this pressing issuea novel binder-free composite composed of a manganese metal-organic framework and functionalized carbon nanofibers (Mn-MOF/f-CNF) has been developed as an electrode modifier for the ultrasensitive detection of TBHQ in food samples. The Mn-MOF/f-CNF composite was achieved using the ultrasonication method, revealing a lamellar sheet-like structure of the Mn-MOF and the curly thread-like fibrous structure of f-CNF. The developed Mn-MOF/f-CNF/SPE sensor system resulted in well-defined redox signals for TBHQ detection in a neutral pH solution. Compared to the unmodified SPE system, the modified system showed approximately a 300 mV reduction in overpotential and a twofold increase in peak current signal for TBHQ detection. The Mn-MOF/f-CNF/SPE sensor system showed a linear concentration window of 0.01 to 800 µM with a sensitivity of 6.28 µA µM-1 cm-2 and the obtained detection limit was 1.36 nM. Additionally, the proposed sensor displayed excellent reproducibility and repeatable results with an RSD of less than 5%. The real-time applicability of the Mn-MOF/f-CNF/SPE sensor system was demonstrated using real samples such as potato chips and instant noodles, showing excellent results with a recovery range of 95.1-98.5%.

Designing an Electrochemical Biosensor Based on Voltammetry for Measurement of Human Chorionic Gonadotropin.

Background: Human chorionic gonadotropin (hCG) is a polypeptide hormone synthesized during pregnancy and is also upregulated in some pathologic conditions such as certain tumors. Its measurement is essential for diagnosing pregnancy and malignancies. Despite numerous attempts to introduce an accurate method capable of detecting hCG levels, several limitations are found in previous techniques. This study aimed to address the limitations of current hCG assay methods by designing an electrochemical biosensor based on voltammetry for the rapid, selective, inexpensive, and sensitive measurement of hCG levels. Methods: A carbon paste electrode was prepared and functionalized by para-aminobenzoic acid. The primary anti-ß-hCG monoclonal antibody was immobilized on the electrode surface by activating the carboxyl groups with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide solutions. The study also involved optimizing parameters such as the time for primary antibody fixation, the time for hCG attachment, and the pH of the hydrogen peroxide solution to maximize the biosensor response. Different concentrations of hCG hormone were prepared and loaded on the electrode surface, the secondary antibody labeled with HRP enzyme was applied, thionine in phosphate-buffered saline solution was placed on the electrode surface, and the differential pulse electrical signal was recorded. Results: The linear range ranged from 5 to 100 mIU/ml, and the limit of detection was calculated as 0.11 mIU. The relative standard deviation was 3% and 2% for five repeated measurements of commercial standard samples with concentrations of 2 and 20 mIU/mL, respectively. The percent recovery was obtained from 98.3% to 101.5%. Conclusion: The sensor represents a promising advancement in hCG level measurement, offering a potential solution to overcome the existing limitations in current diagnostic strategies. Simple and inexpensive design, detecting hCG in its important clinical range during early pregnancy, and successful measurement of hCG in real serum samples are the advantages of this sensor.

Electroanalytical Strategies for Local pH Sensing at Solid-Liquid Interfaces and Biointerfaces.

Obtaining analytical information about chemical species at interfaces is fundamentally important to improving our understanding of chemical reactions and biological processes. pH at solid-liquid interfaces is found to deviate from the bulk solution value, for example, in electrocatalytic reactions at surfaces or during the corrosion of metals. Also, in the vicinity of living cells, metabolic reactions or cellular responses cause changes in pH at the extracellular interface. In this review, we collect recent progress in the development of sensors with the capability to detect pH at or close to solid-liquid and bio interfaces, with spatial and time resolution. After the two main principles of pH detection are presented, the different classes of molecules and materials that are used as active components in these sensors are described. The review then focuses on the reported electroanalytical techniques for local pH sensing. As application examples, we discuss model studies that exploit local pH sensing in the area of electrocatalysis, corrosion, and cellular interfaces. We conclude with a discussion of key challenges for wider use of this analytical approach, which shows promise to improve the mechanistic understanding of reactions and processes at realistic interfaces.

Study on the electrochemical and spectroscopic characteristics of holmium ion and its interaction with DNA.

Metal ion-DNA interactions play a crucial role in modulating the structure and function of genetic material in the natural environment. In this study, we report on the favorable electrochemical activity of holmium(III) (Ho3+) on a glassy carbon electrode (GCE) and its interaction with double-stranded DNA. The interaction between DNA and Ho3+ was investigated for the first time using cyclic voltammetry and differential pulse voltammetry. The electrochemical behavior of Ho3+ ions on a GCE exhibited a reversible electron transfer process, indicative of its redox activity. A linear correlation between the peak current and the square root of the scan rate was observed, suggesting a diffusion-controlled kinetic regime for the electrochemical process. Additionally, fluorescence and absorption spectroscopy were employed to confirm the binding of Ho3+ to DNA. Our findings demonstrate that, at pH 7.2, specific DNA bases and phosphate groups can interact with Ho3+ ions. Moreover, electrochemical measurements suggest that Ho3+ ions bind to DNA via a groove binding mode, with a calculated binding ratio of 1:1 between Ho3+ and DNA. Notably, under optimal conditions, an increase in the amount of DNA leads to a significant reduction in the current intensity of Ho3+ ions.

Eugenol's electrochemical behavior, complexation interaction with copper chloride, antioxidant activity, and potential drug molecular docking application for Covid-19.

Electrochemical studies were conducted to analyze the behavior of eugenol, CuCl2, and their complex using cyclic voltammetry. The oxidation mechanisms of eugenol and the redox behavior of copper ions were elucidated, showing differences in reversibility and charge transfer coefficients. Various kinetic and solvation parameters were determined. The redox behavior of CuCl2 was found to be more reversible compared to the copper-eugenol complex. The copper-eugenol complex exhibited enhanced antioxidant activity compared to eugenol and standard ascorbic acid. The eugenol was oxidized to form eugenol quinone methide through two postulated irreversible mechanisms. Molecular docking studies suggested higher potential bioactivity of the copper-eugenol complex towards the target protein of COVID-19 than the eugenol ligand.

Disposable electrochemical sensors based on reduced graphene oxide/polyaniline/poly(alizarin red S)-modified integrated carbon electrodes for the detection of ciprofloxacin in milk.

An electrochemical sensor based on an electroactive nanocomposite was designed for the first time consisting of electrochemically reduced graphene oxide (ERGO), polyaniline (PANI), and poly(alizarin red S) (PARS) for ciprofloxacin (CIPF) detection. The ERGO/PANI/PARS-modified screen-printed carbon electrode (SPCE) was constructed through a three-step electrochemical protocol and characterized using FTIR, UV-visible spectroscopy, FESEM, CV, LSV, and EIS. The new electrochemical CIPF sensor demonstrated a low detection limit of 0.0021 µM, a broad linear range of 0.01 to 69.8 µM, a high sensitivity of 5.09 µA/µM/cm2, and reasonable selectivity and reproducibility. Moreover, the ERGO/PANI/PARS/SPCE was successfully utilized to determine CIPF in milk with good recoveries and relative standard deviation (< 5%), which were close to those with HPLC analysis.

Rapid nanomolar detection of cocaine in biofluids by electrochemical aptamer-based sensor with low-temperature effect for drugged driving screening.

Cocaine is one of the most abused illicit drugs, and its abuse damages the central nervous system and can even lead directly to death. Therefore, the development of simple, rapid and highly sensitive detection methods is crucial for the prevention and control of drug abuse, traffic accidents and crime. In this work, an electrochemical aptamer-based (EAB) sensor based on the low-temperature enhancement effect was developed for the direct determination of cocaine in bio-samples. The signal gain of the sensor at 10 °C was greatly improved compared to room temperature, owing to the improved affinity between the aptamer and the target. Additionally, the electroactive area of the gold electrode used to fabricate the EAB sensor was increased 20 times by a simple electrochemical roughening method. The porous electrode possesses more efficient electron transfer and better antifouling properties after roughening. These improvements enabled the sensor to achieve rapid detection of cocaine in complex bio-samples. The low detection limits (LOD) of cocaine in undiluted urine, 50% serum and 50% saliva were 70 nM, 30 nM and 10 nM, respectively, which are below the concentration threshold in drugged driving screening. The aptasensor was simple to construct and reusable, which offers potential for drugged driving screening in the real world.

Development of a dual-template molecularly imprinted electrochemical sensor for the simultaneous detection of depression markers 5-HT and Glu.

A dual-template molecularly imprinted electrochemical sensor was developed for the simultaneous detection of serotonin (5-HT) and glutamate (Glu). First, amino-functionalized reduced graphene oxide (NRGO) was used as the modification material of a GCE to increase its electrical conductivity and specific surface area, using Glu and 5-HT as dual-template molecules and o-phenylenediamine (OPD) with self-polymerization ability as functional monomers. Through self-assembly and electropolymerization, dual-template molecularly imprinted polymers were formed on the electrode. After removing the templates, the specific recognition binding sites were exposed. The amount of NRGO, polymerization parameters, and elution parameters were further optimized to construct a dual-template molecularly imprinted electrochemical sensor, which can specifically recognize double-target molecules Glu and 5-HT. The differential pulse voltammetry (DPV) technique was used to achieve simultaneous detection of Glu and 5-HT based on their distinct electrochemical activities under specific conditions. The sensor showed a good linear relationship for Glu and 5-HT in the range 1 ~ 100 µM, and the detection limits were 0.067 µM and 0.047 µM (S/N = 3), respectively. The sensor has good reproducibility, repeatability, and selectivity. It was successfully utilized to simultaneously detect Glu and 5-HT in mouse serum, offering a more dependable foundation for objectively diagnosing and early warning of depression. Additionally, the double signal sensing strategy also provides a new approach for the simultaneous detection of both electroactive and non-electroactive substances.

Influence of Potentiostat Hardware on Electrochemical Measurements.

We describe two operating modes for the same potentiostat, where the redox processes of hydroquinone in a hydrochloric acid medium are contrasted for cyclic voltammetry (CV) as functions of a digital/staircase scan and an analogue/linear scan. Although superficially there is not much to separate the two modes of operation as an end user, differences can be seen in the voltammograms while switching between the digital and analogue modes. The effects of quantization clearly have some impact on the measurements, with the outputs between the two modes being a function of the equivalent-circuit model of the electrochemical system under investigation. Increasing scan rates when using both modes produces higher peak redox currents, with the differences between the analogue and digital modes of operation being consistent as a function of the scan rate. Differences between the CV loops between the analogue and digital modes show key differences at certain points along the scans, which can be attributed to the nature of the electrolyte affecting the charging and discharging processes and consequently changing the peak currents of the redox processes. The faradaic processes were shown to be independent of the scan rates. Simulations of the equivalent-circuit behaviour show differences in the responses to different input signals, i.e., the step and ramp responses of the system. Both the voltage and current steps and ramp responses showed the time-domain behaviour of distinct elements of the equivalent electrochemical circuit model as an approximation of the applied digital and analogue CV input signals. Ultimately, it was concluded that similar parameters between the two modes of operation available with the potentiostat would lead to different output voltammograms and, despite advances in technology, digital systems can never fully emulate a true analogue system for electrochemical applications. These observations showcase the value of having hardware capable of true analogue characteristics over digital systems.

Modified Gold Screen-Printed Electrodes for the Determination of Heavy Metals.

Screen-printed electrodes (SPEs) are reliable, portable, affordable, and versatile electrochemical platforms for the real-time analytical monitoring of emerging analytes in the environmental, clinical, and agricultural fields. The aim of this study was to evaluate the electrochemical behavior of gold screen-printed electrodes (SPGEs) modified with molecules containing amino (Tr-N) or α-aminophosphonate (Tr-P) groups for the selective and sensitive detection of the toxic metal ions Pb2+ and Hg2+ in aqueous samples. After optimizing the analytical parameters (conditioning potential and time, deposition potential and time, pH and concentration of the supporting electrolyte), anodic square wave stripping voltammetry (SWASV) was used to evaluate and compare the electrochemical performance of bare or modified electrodes for the detection of Hg2+ and Pb2+, either alone or in their mixtures in the concentration range between 1 nM and 10 nM. A significative improvement in the detection ability of Pb2+ ions was recorded for the amino-functionalized gold sensor SPGE-N, while the presence of a phosphonate moiety in SPGE-P led to greater sensitivity towards Hg2+ ions. The developed sensors allow the detection of Pb2+ and Hg2+ with a limit of detection (LOD) of 0.41 nM and 35 pM, respectively, below the legal limits for these heavy metal ions in drinking water or food, while the sensitivity was 5.84 µA nM-1cm-2 and 10 µA nM-1cm-2, respectively, for Pb2+ and Hg2+. The reported results are promising for the development of advanced devices for the in situ and cost-effective monitoring of heavy metals, even in trace amounts, in water resources.

Fast and simple voltammetric sensing of avanafil in the pharmaceutical formulation by using unmodified boron-doped diamond electrode.

Background and purpose: Erectile dysfunction is a common issue among adult males involving difficulty in maintaining an erection, and it is often treated with fast-acting, low-side-effect drugs like avanafil (AVN), among other phosphodiesterase-5 inhibitors. Hence, developing fast, simple, and sensitive methods to detect AVN is crucial. Experimental approach: This study conducts an electroanalytical inquiry and provides a new voltammetric method for accurately analyzing AVN utilizing a boron-doped diamond (BDD) electrode without any modifications. Key results: In the Britton-Robinson buffer (BR, 0.04 mol L-1, pH 4.0), cyclic voltammetry showed a clearly defined and irreversible anodic peak at around +1.44 V relative to Ag/AgCl. The pH of the solution was shown to have an impact on the voltammetric signals of the oxidation peaks. A good linear response for AVN quantification was achieved using square-wave voltammetry. This was done in a 0.04 mol L-1 BR (pH 4.0) solution at a potential of +1.33 V (vs. Ag/AgCl). The method exhibited a wide dynamic range of 0.5 to 30.0 µg mL-1 (1.0 to 62 µmol L-1) and a low limit of detection of 0.14 µg mL-1 (0.29 µmol L-1). The method proposed demonstrated suitability for determining AVN content in pharmaceutical formulations. The accuracy of the approach was demonstrated by comparing the results obtained using the developed method with those achieved using the UV-Vis spectrometry method. Conclusion: Our method simplifies the analytical process by eliminating the need for electrode modification, reducing both time and resource requirements while enhancing overall feasibility.

An electrochemical biosensor for sensitive detection of live Salmonella in food via MXene amplified methylene blue signals and electrostatic immobilization of bacteriophages.

A novel bacteriophage-targeted electrochemical biosensor designed for accurate and quantitative detection of live Salmonella in food samples is presented. The biosensor is simply constructed by electrostatic immobilizing bacteriophages on MXene-nanostructured electrodes. MXene, renowned for its high surface area, biocompatibility, and conductivity, serves as an ideal platform for bacteriophage immobilization. This allows for a high-density immobilization of bacteriophage particles, achieving approximately 71 pcs µm-2. Remarkably, the bacteriophages immobilized MXene nanostructured electrodes still maintain their viability and functionality, ensuring their effectiveness in pathogen detection. Therefore, the proposed biosensor exhibited enhanced sensitivity with a low limit of detection (LOD) of 5 CFU mL-1. Notably, the biosensor shows excellent specificity in the presence of other bacteria that commonly contaminate food and can distinguish live Salmonella from a mixed population. Furthermore, it is applicable in detecting live Salmonella in food samples, which highlights its potential in food safety monitoring. This biosensor offers simplicity, convenience, and suitability for resource-limited environments, making it a promising tool for on-site monitoring of foodborne pathogenic bacteria.

Tuning the shell thickness of N-doped interconnected hollow carbon sphere for the electrochemical sensing of antibiotic drug chloramphenicol.

N-doped hollow carbon spheres (NHCSs) with different shell thicknesses are constructed using various amounts of SiO2 precursor. An interconnected framework with diminished wall thickness ensures an efficient and continuous electron transport which helps to enhance the performance of NHCS. Improvement of the electrocatalytic performance was shown in the determination of antibiotic drug chloramphenicol (CAP) due to the unique hollow thin shell morphology, ample defect sites, accessible surface area, higher surface-to-volume ratio and an synergistic effect. Boosted electrocatalytic activity of 1.5 N-doped HCS (1.5 NHCS) was applied to detect CAP with a linear range and detection limit of 1-1150 µM and 0.098 µM (n = 3), respectively, with superior storage stability and considerable sensitivity. These results suggest that the proposed work can be successfully applied to the determination of CAP in milk and water samples.

Efficient nitrite determination by electrochemical approach in liquid phase with ultrasonically prepared gold-nanoparticle-conjugated conducting polymer nanocomposites.

An electrochemical nitrite sensor probe is introduced herein using a modified flat glassy carbon electrode (GCE) and SrTiO3 material doped with spherical-shaped gold nanoparticles (Au-NPs) and polypyrrole carbon (PPyC) at a pH of 7.0 in a phosphate buffer solution. The nanocomposites (NCs) containing Au-NPs, PPyC, and SrTiO3 were synthesized by ultrasonication, and their properties were thoroughly characterized through structural, elemental, optical, and morphological analyses with various conventional spectroscopic methods, such as field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller method. The peak currents due to nitrite oxidation were characterized in detail and analyzed using conventional cyclic voltammetry (CV) as well as differential pulse voltammetry (DPV) under ambient conditions. The sensor response increased significantly from 0.15 to 1.5 mM of nitrite ions, and the sensor was fabricated by coating a conducting agent (PEDOT:PSS) on the GCE to obtain the Au-NPs/PPyC/SrTiO3 NCs/PEDOT:PSS/GCE probe. The sensor's sensitivity was determined as 0.5 µA/µM∙cm2 from the ratio of the slope of the linear detection range by considering the active surface area (0.0316 cm2) of the flat GCE. In addition, the limit of detection was determined as 20.00 ± 1.00 µM, which was found to be satisfactory. The sensor's stability, pH optimization, and reliability were also evaluated in these analyses. Overall, the sensor results were found to be satisfactory. Real environmental samples were then analyzed to evaluate the sensor's reliability through DPV, and the results showed that the proposed novel electrochemical sensor holds great promise for mitigating water contamination in the real samples with the lab-made Au-NPs/PPyC/SrTiO3 NC. Thus, this study provides valuable insights for improving sensors for broad environmental monitoring applications using the electrochemical approach.

Trimethylamine N-oxide detection by electrochemical sensor based on screen printed electrode modified with molecularly imprinted polypyrrole-molybdenum(III) sulfide nanosheets.

Trimethylamine N-oxide (TMAO) is a gut metabolite produced by dietary L-carnitine and choline metabolism. Its altered level in the serum has been implicated in human health and diseases such as colorectal cancer, chronic kidney diseases, cardiovascular diseases, etc. Early detection of TMAO in body fluids has been presumed to be significant in understanding the pathogenesis and treatment of many diseases. Hence, developing reliable and rapid technologies for its detection may augment our understanding of pathogenesis and diagnosis of diseases. Hence, in the present work, polypyrrole (Ppy)@molybdenum(III)sulfide (Mo2S3) nanosheets (NS) composite molecularly imprinted polymer (MIP) (Ppy@Mo2S3-MIP) based electrochemical sensor has been fabricated for the detection of TMAO. Polypyrrole (Ppy) and Mo2S3 NS have been synthesized by chemical oxidative polymerization and hydrothermal techniques, respectively. The synthesized nanocomposite has been validated using different techniques such as X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The fabricated Ppy@Mo2S3-MIP sensor showed a linear detection range from 30 µM to 210 µM, a sensitivity of 1.21 µA µM-1 cm-2 and a limit of detection as 1.4 µM for the detection of TMAO and found more robust and improved when compared with Ppy-MIP using identical parameters. The fabricated sensor is also highly selective towards TMAO. It can be further used to detect TMAO in human samples such as urine quickly.

Electrocatalytic Hydrogen Generation by Ni-PN3P Pincer Complexes: Role of Phosphorus Substituents in Tuning the Reactivity.

Electrocatalytic hydrogen evolution reaction (eHER) is crucial in addressing the growing global energy demand. Although nickel-pincer-based molecular complexes, varying in donor atoms, were studied previously for eHER, the impact of variations in the substituents attached to the donor atoms was not investigated. Herein, three air-stable R1PN3PR2-based NiII-pincer complexes [R1=R2=Ph2 (7); R1=R2=tBu2 (9); R1= tBu2, R2=Ph2 (10)], varying solely in P-substituents, were studied in acetonitrile. While the redox potentials for NiII/I and NiI/0 couples underwent anodic shifts by ~100 mV upon progressively substituting tert-butyl by phenyl groups on each P-atom, the corresponding eHER reactivity with organic acids (acetic acid,  p-toluenesulfonic acid and trifluoromethanesulfonic acid) of different strengths followed different trends; likely influenced by the pKa of intermediate metal-hydride (M-H) species [pKa(M-H9) > pKa(M-H10) > pKa(M-H7)]. Depending on the acid strength, different oxidation states of the metal were activated to promote eHER. The catalytic rates for 9, 10, and 7 were calculated to be 85 s-1, 77 s-1 and 95 s-1 with Faradaic efficiencies of 88.5 ± 2%, 66.1 ± 1.4%, and 91.7 ± 1.5% respectively, in acetic acid. Electrochemical data supported by theoretical results reinforce a significant electronic influence of the anchoring P-substituents on the activity of these complexes.

Synthesis and characterization of polysaccharide-cryogel and its application to the electrochemical detection of DNA.

The main goal of our study is to demonstrate the applicability of the PPy-cryogel-modified electrodes for electrochemical detection of DNA. First, a polysaccharide-based cryogel was synthesized. This cryogel was then used as a template for chemical polypyrrole synthesis. This prepared polysaccharide-based conductive cryogel was used for electrochemical biosensing on DNA. Carrageenan (CG) and sodium alginate (SA) polysaccharides, which stand out as biocompatible materials, were used in cryogel synthesis. Electron transfer was accelerated by polypyrrole (PPy) synthesized in cryogel networks. A 2B pencil graphite electrode with a diameter of 2.00 mm was used as a working electrode. The prepared polysaccharide solution was dropped onto a working electrode as a support material to improve the immobilization capacity of biomolecules and frozen to complete the cryogelation step. PPy synthesis was performed on the electrodes whose cryogelation process was completed. In addition, the structures of cryogels synthesized on the electrode surface were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Surface characterization of the modified electrodes was performed by energy-dispersive X-ray spectroscopy (EDX) analysis. Electrochemical determination of fish sperm DNA (fsDNA) was performed using a PPy-cryogel-modified electrode. The use of a porous 3D cryogel intermediate material enhanced the signal by providing a large surface area for the synthesis of PPy and increasing the biomolecule immobilization capacity. The detection limit was 0.98 µg mL-1 in the fsDNA concentration range 2.5-20 µg mL-1. The sensitivity of the DNA biosensor was estimated to 14.8 µA mM-1 cm-2. The stability of the biosensor under certain storage conditions was examined and observed to remain 66.95% up to 45 days.