Reduction Peak Research Articles

Ruthenium decorated V@WO3 nanocomposites heterostructures for selective detection of sulfonamide in honey samples

In the current study, V@WO3 nanocomposite heterostructures were synthesized by a facile hydrothermal method having 1D highly stable and uniform morphology. The designed nanostructures were decorated with ruthenium nanoparticles through a microwave-assisted fabrication method. The physiochemical attributes of Ru/V@WO3 were confirmed by applying various analytical as well as spectroscopic techniques; including, XRD, SEM, FTIR, Raman spectroscopy, and UV–vis spectroscopy. The Ru/V@WO3 modified glassy carbon electrode was utilized for the detection of sulfonamide. The fabricated electrode exhibited fantastic electrochemical properties for the highly selective and sensitive detection of sulfonamide with a desirable and well-defined reduction peak (39 µA) at − 0.6 V. The designed sensor was used for the detection of sulfonamide in honey samples with 0.006 nM LoD and the regression value was 0.997 indicating a good linear relationship between composite and analyte. To study the selectivity of the designed sensor, interfering substances; trimethoprim (TMP), metronidazole (MTD), cephalosporin (CEP), and dihydroartemisinin (DHA) were used and no response was recorded against these drugs. Furthermore, the modified GCE showed excellent stability and life span.

Solvent Impact on Langmuir and Langmuir–Schaefer Films of Soluble Main‐Chain Poly(fullerene)s Based on C60

Understanding the morphology and electronic properties of poly(fullerene)s is crucial for the development of new organic devices. This work addresses the fabrication and characterization of Langmuir–Schaefer (LS) films of poly(fullerene)s based on C60 with short (HSS8) and long (HSS16) sidechains, solubilized in chloroform or xylene. In addition, density functional theory (DFT) calculations are used to optimize the molecular geometries, determine energies, and investigate the influence of solvent applied. Depending on the organic solvent, floating material isotherms indicate the formation of disordered aggregates in the aqueous subphase. The influence of solvent in LS films is also evidenced by way of atomic force microscopy (AFM), UV‐vis, and cyclic voltammetry (CV) measurements. From DFT calculations, the arms of the poly(fullerene)s start to extend from an initial position of surrounding the fullerene sphere. In AFM measurements, depending on the organic solvent, the roughness significantly reduces, while the homogeneity is much higher. In UV‐vis and CV measurements, the propensity to form aggregates depends mainly on the polarization of the solvent and is directly related to the maximum absorption, oxidation, and reduction peaks. From the optical bandgap energy values, the poly(fullerene)s studied here present high potential for application in organic electronic devices.

Electrodeposited folic acid platinum electrode for rapid detection of human hepatocellular carcinoma cells

AbstractFolic acid (FA) was successfully adhered onto the surface of platinum through an electrochemical process without hindering its functional capability to bind with human hepatocellular carcinoma (HepG2) cells. The CV response of FA‐deposited platinum electrode showed distinct oxidation and reduction peaks, which decreased gradually by varying the concentrations of FA. The electrochemically deposited FA/Pt electrode was used to detect HepG2 cells in the electrolyte, and a linear response in DPV peak current was observed with a sensitivity of ∼ 3 nA/cells mL−1 in the range of 5×103 to 25×103 cells mL−1.

Protecting heritage: Insights into effective flood management using green infrastructure in a highly urbanized environment

Developing flood resilience in heritage cities is an exigent challenge of rapidly urbanizing cities of the Global South. While Green Infrastructure (GI) intervention is generally considered an important flood adaptation measure, the limited space availability combined with complex urban hydrodynamics makes the objective assessment of its efficacy challenging. Our study addresses this by integrating a 1D-2D hydrodynamic model with high-resolution remote sensing datasets, including satellite imageries derived from Sentinel-1 and Sentinel-2 and flood levels obtained from field surveys to generate contextualized urban flood maps that consider the constraints of heavily urbanized land areas in the city of Ahmedabad, a rapidly urbanizing historic city in western parts of India. Historically, this city has not been flood-prone, but the high intensity of urbanization is rendering the city extremely vulnerable to flooding risks. We investigate the efficacy of four individual Green Infrastructure(GI) facilities in managing urban stormwater based on contextual space and resource availability. The efficiency is quantified based on runoff reduction coefficient, flood extent, and peak flood depth metrics. The results show that permeable pavements are the most efficient, reducing flood volume and flooded area by 23% and 1.5%, respectively. However, these benefits were marginal, challenging the current understanding. Our findings underscore the necessity for location-specific GI solutions in urban flood risk management.

A reduced graphene oxide-based electrochemical sensing and eco-friendly 4-nitrophenol degradation

The pollutant para-nitrophenol or 4-Nitrophenol (4-NP) is being deemed lethal because it slows down photosynthetic processes, is carcinogenic, and has other major negative impacts on aquatic as well as terrestrial life. In this study, a distinctive electrochemical sensor for measurement of the 4-Nitrophenol was incorporated by electrodepositing nanocomposite of reduced graphene oxide (RGO) and manganese dioxide (MnO2) on conductive fabric (CF). The morphological features of the prepared electrode (RGO/MnO2/CF) were studied by scanning electron microscopy (SEM), whereas the phase purity and formation of composite were authenticated via X-ray diffraction method. Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDS) and elemental mapping were also employed to analyze the morphology and elemental composition of the composite. Analysis and comparison were done on the electrochemical characteristics of 4-Nitrophenol on RGO/MnO2/CF. The electrochemical studies involved the pH study, cyclic voltammetry analysis at the rate of 0.05 Vs−1, scan rate study, and incubation time study which were done to examine the behavior and kinetics of the synthesized electrodes. The fabricated RGO/MnO2/CF electrode was found to have clearly defined redox peak currents towards 4-Nitrophenol. The limit of detection (LOD) and limit of quantification (LOQ) of 55.9 μM and 169.3 μM was calculated for optimal circumstances where the reduction peak current fluctuates linearly with a concentration of 4-Nitrophenol. Additionally, the as-fabricated sensor maintained >99.9 % of its original signal even after 5 weeks of storage, proving its good stability, significant specificity, and reproducibility. As a result, the suggested technique offers an outstanding framework for the simple and reliable sensing of 4-Nitrophenol. In addition, RGO and the optimal amount of NaBH4 were added to study the degradation of 4-NP. The degradation was analyzed by taking the absorbance of the sample after an interval of 5 min. The findings demonstrate that 4-NP is effectively degraded by the RGO.

Improvement of CO Oxidation and CH4 Combustion by Pd and Pt Partial Substitution on LaMn0.5Cu0.5O3 Perovskite.

LaMn0.5Cu0.5O3 (LMC) as the parent perovskite and Pd- and Pt-doped LaMn0.5Cu0.5O3 catalysts (LMCPd and LMCPt) instead of Cu were synthesized in a new solid-state synthesis technique at a low temperature. Perovskite lattice formation of the LMC catalyst was successfully performed at 600 °C. All perovskites were investigated by X-ray diffraction, HRTEM, O2-TPD, H2-TPR, BET, and XPS analyses. The prepared perovskites were used as heterogeneous catalysts for CO oxidation and methane combustion reactions. The catalytic performance of the LMC catalyst was noticeably enhanced via Pd and Pt substitution instead of Cu. The enhancement in the mobility of lattice oxygen and specific surface area has triggered this catalytic performance improvement, which play an important role in CO oxidation and methane combustion. The Mn 2p and Mn 3s XPS spectra showed that by doping Pd and Pt in the LMC perovskite, Mn was affected in different states and the Mn 3s peaks were only observed in the LMCPt catalyst. XPS spectra of the LMCPd1 sample showed a high oxidation state of Pd3+ or Pd4+, from which it can be concluded that Pd was successfully incorporated into the LMC perovskite lattice. The H2-TPR profiles of the LMCPd and LMCPt perovskites revealed that the reduction peaks of Cu and Mn were shifted to lower temperatures by increasing Pd and Pt partial substitution due to the synergetic effect of the cation and the H2-spillover effect of palladium and platinum.

Electrochemical sensor based on onion-like carbon (OLC) materials modified electrode for sensitive determination of 4-nitrophenol

Due to its advantageous features, the electrochemical technique has garnered considerable attention in detecting 4-nitrophenol (4-NP). And the modified materials of such working electrode significantly influence the sensitivity of the electrochemical sensor. In this investigation, a sensitive and selective electrochemical sensor for detecting 4-NP in real water samples was developed by using a spherical onion-like carbon (OLC) as a new material for electrode modification. By comparing with generally used carbon nanotube (CNT), OLC exhibits higher electroactive surface area and conductibility. The electroactive surface area of OLC modified glassy carbon electrode (OLC/GCE) and CNT modified GCE (CNT/GCE) was determined to be 0.1508 cm2 and 0.1231 cm2 respectively. Notably, the OLC/GCE (Ipc:−139 μA) exhibited a significantly higher reduction peak current for 4-NP reduction in contrast to CNT/GCE (Ipc:−94 μA) determined by the cyclic voltammetry test. Remarkably, under ideal conditions, the OLC/GCE displayed a linear detection range for 4-NP spanning from 0.05 to 120 μM, with an exceptionally low identifying limit of 3.74 nM. In addition, OLC/GCE exhibits excellent selectivity, reproducibility, and repeatability for determining 4-NP. And the current response remains about 92% of its primal value 15 days later, demonstrating an outstanding stability of OLC/GCE. Furthermore, OLC/GCE was successfully employed in determining 4-NP in authentic water samples, yielding satisfactory recovery rates ranging from 96.14% to 102.1%. This investigation exemplifies the outstanding sensing capabilities and promising potential of OLC in the field of electrochemically detecting 4-NP in environmental settings, which provides a new method for the simple, sensitive and quantitative detection of 4-NP.

Structural, Electrical, and Electrochemical Properties of a Na2O-V2O5 Ceramic Nanocomposite as an Active Cathode Material for a Na-Ion Battery

In this paper, a relationship between the structure and the electrical properties of a nanocrystalline composite ceramics xNa2O·(100 − x)V2O5 with ‘x’ of 5, 15, 25, 35, and 45 mol%, abbreviated as xNV, was investigated by X-ray diffractometry (XRD), X-ray absorption spectroscopy (XAS), Cyclic Voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and cathode active performance in Na-ion battery (SIB). For the expected sodium vanadium bronzes (NaxV2O5) precipitation, the preparation of xNV was performed by keeping the system in the molten state at 1200 °C for one hour, followed by a temperature decrease in the electric furnace to room temperature at a cooling rate of 10 °C min−1. XRD patterns of the 15NV ceramic exhibited the formation of Na0.33V2O5 and NaV3O8 crystalline phases. Moreover, the V K-edge XANES showed that the absorption edge energy of ceramics 15NV recorded at 5479 eV is smaller than that of V2O5 at 5481 eV, evidently indicating a partial reduction from V5+ to V4+ due to the precipitation of Na0.33V2O5. In the cyclic voltammetry, reduction peaks of 15NV were observed at 1.12, 1.78 V, and 2.69 V, while the oxidation peak showed up only at 2.36 V. The values of the reduction peaks were related to the NaV3O8 crystalline phase. Moreover, the diffusion coefficient of Na+ (DNa+) gradually decreased from 8.28 × 10−11 cm2 s−1 to 1.23 × 10−12 cm2 s−1 with increasing Na2O content (x) from 5 to 45 mol%. In the evaluation of the active cathode performance of xNV in SIB, ceramics 15NV showed the highest discharge capacity 203 mAh g−1 at a current rate of 50 mA g−1. In the wider voltage range from 0.8 to 3.6 V, the capacity retention was maintained at 50% after 30 cycles, while it was significantly improved to 90% in the narrower voltage range from 1.8 to 4.0 V, although the initial capacity decreased to 56 mAh g−1. It is concluded that the precipitation of the Na0.33V2O5 phase improved the structural and electrical properties of 15NV, which provides a high capacity for the Na-ion battery when incorporated as a cathode active material.

Simulation and fabrication of titanium dioxide thin films for supercapacitor electrode applications

Nanostructured thin-film electrode materials are proposed for supercapacitors due to their outstanding performance over bulk materials. In this work, we fabricated a TiO2 nanotube film over a titanium foil using a top-down approach for supercapacitor electrodes. We noticed that the fabricated nanotubes are uniform and well aligned, confirmed by FESEM; the TiO2 nanotube parameters were further simulated using COMSOL Multiphysics. Simulations show an areal capacitance of 1.19393 pF/cm2 with oxidation and reduction peak currents of 6.18921×10[Formula: see text] A and −6.0320×10[Formula: see text] A, respectively, at 10 mV/s scan rate. The as-prepared nanotubes show a poor areal capacitance of 1.0193 F/cm2, which is improved to 12.8764 F/cm2 at a scan rate of 10 mV/s, that is approximately 12.63 times with oxidation and reduction peak currents of 0.129 mA/cm2 and −0.105 mA/cm2, respectively, by performing an electrochemical etching. Further, the surface roughness of both as-prepared and etched samples is studied to comment on their surface area changes. The effect of the etched sample is studied, compared and validated with simulation, which reveals that the etched TiO2 nanotubes thin-film sample shows considerable similarity with the simulation results.

Crystal phase-mediated oxidative dehydrogenation of lactic acid to pyruvic acid on MoO3

Sustainable production of pyruvic acid was investigated in the presence of MoO3 catalyst through oxidative dehydrogenation of lactic acid with air as oxidizing agent. α-MoO3 can be easily transformed to h-MoO3 under the assistance of monovalent cation, in which Na+ offered the strongest ability. It is found that the reactivity of oxidative dehydrogenation of lactic acid depends on crystal phase of MoO3, and h-MoO3 displays far better activity than α-MoO3. Structure characterizations reveal that h-MoO3 mainly exposes (110) plane while α-MoO3 mainly exposes (010) plane. Adsorption energy of lactic acid molecule on (110) plane with -11.04 eV is far lower than (010) plane with +4.73 eV, suggesting that lactic acid molecule is easily adsorbed on (110) plane, rather than (010) plane. Kinetic study shows that the activation energy is 14.23 kJ/mol on h-MoO3, lower than that on α-MoO3 with 23.15 kJ/mol. XPS results reveal that the binding energy of Mo 3d in h-MoO3 is higher than α-MoO3, suggesting a stronger oxidative ability. Furthermore, h-MoO3 has a larger valence band value of 3.42 eV than α-MoO3 with 3.35 eV, also demonstrating a stronger oxidative ability. H2-TPR results show that the reduction peak at low temperature of around 500 °C is stronger over h-MoO3 than α-MoO3, suggesting that surface-crystal oxygen of h-MoO3 is easilier departed during the oxidative dehydrogenation of lactic acid. At 230 °C, h-MoO3 achieved 82.3% of pyruvic acid selectivity at LA conversion of 82.0%, far higher than α-MoO3 with 38.2% of pyruvic acid selectivity at LA conversion of 42.4%. This work provided a novel strategy for boosting the oxidative dehydrogenation of lactic acid to pyruvic acid by crystal phase-mediated reactivity, and achieving sustainable production of pyruvic acid.

Gold–graphitic carbon nitride composite electrode for pimobendan detection

AbstractIntroductionHeart failure can lead to death and hospitalization, especially among older adults, and pimobendan is used with human patients. We investigated the electrochemical behavior of Au/g‐C3N4 electrochemical sensors to detect the concentration of pimobendan.ExperimentalCharacterization of the materials was conducted using XRD, TEM, SEM, EDS and FTIR. Cyclic voltammetry (CV) was used to measure the concentration and redox properties of pimobendan.Result and DiscussionsAt a voltage of 0.05 V, a reduction peak appeared, indicating an association between pimobendan concentration (ranging from 0 to 55 μM) and reductive current. At low concentrations of pimobendan concentration from 0.0 to 1.3 μM, the linearity R2 = 0.9149 with a detection limit of 0.29 μM. Dopamine, epinephrine, and uric acid did not interfere with the detection of pimobendan.ConclusionsA composite sensing electrode consisting of 3% Au/g‐C3N4 was fabricated for the detection of pimobendan. A potential pimobendan sensing mechanism on 3% Au/g‐C3N4 was proposed on the basis of these findings.

Preparation and characterization of molybdenum trioxide/poly(3,4-ethylenedioxythiophene): Polystyrene sulphonate nanocomposites for electrochromic application.

Electrochromic processes are mostly characterized by colour change arising from the energy of a chemical reaction involving electron transfer. Transition metal oxides of tungsten, molybdenum, iridium, and nickel show the most intense Electrochromic colour changes and photochemical stability of about 100 cycles compared to organic electrochromes which are susceptible to photochemical degradation. The prospect of conjugated polymers (comprising of metal oxides and polymers) has opened a new dimension on improving the Electrochromic performance of the transition metal oxides. In this work, solution growth methods were employed in preparing a MoO3/PEDOT: PSS composite layer by adding PEDOT: PSS into MoO3 aqueous dispersion resulting in an electrostatic interaction between MoO3 and PEDOT: PSS for electrochromic application. This composite has shown a long-term stability up to more than 550 cycles which shows higher potential specific capacitance than WO3/PEDOT: PSS. This approach has significantly improved the stability issue of MoO3 and enhances the potential of MoO3-based materials for electrochromic applications. The semi crystalline nature of MoO3-300 °C was further proved by FE-SEM observation of the MoO3 nanoparticles. The particle size shown in the images corresponds with FE-SEM result and polycrystalline structure was observed under high magnification. The polycrystalline nature of the MoO3 particles favors their electrochemical stability, while their small size facilitates their effective interactions with PEDOT: PSS. The electrochemical properties of MoO3, PEDOT: PSS and composite were further studied by cyclic voltammetry (CV) from -1 V to +1 V. MoO3 has a broad oxidation peak at -0.43 V and no obvious reduction peak in this range. PEDOT: PSS has an oxidation peak at -0.02 V and a reduction peak at -0.55 V. In the composite, the peak at -0.43 V becomes a shoulder and a new pair of redox peaks appear at -0.18 V/-0.09 V.

Determination of 2,4-dinitrophenylhydrazine using carbon paste modified with nanoparticles by cyclic voltammetry, high-performance liquid chromatography and spectrophotometry methods

The research deals with the manufacture of an electrode using modified carbon paste to determine 2,4-dinitrophenylhydrazine (2,4-DNPHZ), The modified carbon paste electrode (NiO-NCQD/g-C3N4/MCPE). The results show the presence of oxidation and reduction peaks, and it is subject to a quasi-reversible system; the best value ​​of pH is (1) using sulfuric acid with a concentration of (0.1M), and scan rate is 100 mv sec-1, it was linearity range of (1-1000) µM for oxidation, and (100-1000) µM for reduction, with correlation coefficient (R2=0.9717) and (R2=0.9914) for each of them, respectively. The proposed electrochemical method was compared with two methods they are spectrophotometry at a wavelength 360) nm( and high-performance liquid chromatography (HPLC) at wavelengths (340 and 250) nm. It turned out that the electrochemical method (NiO-NCQD/g-C3N4/MCPE) was superior to the spectrophotometry method in terms of the detection limit. It turns out that there is no significant difference between (HPLC) and (NiO-NCQD/g-C3N4/MCPE) in terms of accuracy. The proposed electrochemical method is a new analytical method characterized by accuracy, repeatability, and reliability.

Use of biogenic silver nanoparticles on the cathode to improve bioelectricity production in microbial fuel cells.

To date, research on microbial fuel cells (MFCs) has. focused on the production of cost-effective, high-performance electrodes and catalysts. The present study focuses on the synthesis of silver nanoparticles (AgNPs) by Pseudomonas sp. and evaluates their role as an oxygen reduction reaction (ORR) catalyst in an MFC. Biogenic AgNPs were synthesized from Pseudomonas aeruginosa via facile hydrothermal synthesis. The physiochemical characterization of the biogenic AgNPs was conducted via scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-visible spectrum analysis. SEM micrographs showed a spherical cluster of AgNPs of 20-100nm in size. The oxygen reduction reaction (ORR) ability of the biogenic AgNPs was studied using cyclic voltammetry (CV). The oxygen reduction peaks were observed at 0.43V, 0.42V, 0.410V, and 0.39V. Different concentrations of biogenic AgNPs (0.25-1.0mg/cm2) were used as ORR catalysts at the cathode in the MFC. A steady increase in the power production was observed with increasing concentrations of biogenic AgNPs. Biogenic AgNPs loaded with 1.0mg/cm2 exhibited the highest power density (PDmax) of 4.70W/m3, which was approximately 26.30% higher than the PDmax of the sample loaded with 0.25mg/cm2. The highest COD removal and Coulombic efficiency (CE) were also observed in biogenic AgNPs loaded with 1.0mg/cm2 (83.8% and 11.7%, respectively). However, the opposite trend was observed in the internal resistance of the MFC. The lowest internal resistance was observed in a 1.0mg/cm2 loading (87Ω), which is attributed to the high oxygen reduction kinetics at the surface of the cathode by the biogenic AgNPs. The results of this study conclude that biogenic AgNPs are a cost-effective, high-performance ORR catalyst in MFCs.

Synthesis and Characterization of Cross-linkable Viologen Derivatives

In this study, crosslinkable allyl functional viologen derivative (ALV-Br) was synthesized with 4-4'biridyl in the presence of allyl bromide in acetonitrile and the precipitated product was separated by filtration. Chemical characterization of the obtained structure was carried out as a result of FT-IR and 1H-NMR spectra. In the cyclic voltammetry (CV) measurements performed for electrochemical characterization, a two-step reversible reduction peak attributed to viologen salts was clearly observed in the 0-0.8 V range. According to the UV-Vis absorption spectra, it is seen that they only absorb in the UV region below 400 nm in both solution and thin film. Thin films of ALV-Br salt were then spray coated in the presence of a tetrathiol-based crosslinker (pentaerythritol tetrakis(3-mercapto-propionate).In the final step, the surface morphology of the crosslinked thin film was examined by Atomic force microscopy (AFM) and compared with the results of the non-crosslinked one. Finally, the patterned film of ALV-Br could be obtained by this technique.

Development of a high-performance label-free electrochemical immunosensor for early cancer diagnosis using anti-CEA/Ag-MOF/GO/GCE nanocomposite

In order to detect carcinoembryonic antigen (CEA) as a tumor marker in lung cancer for early cancer diagnosis, this study aimed to develop a label-free electrochemical immunosensor based on the immobilization of an Anti-CEA antibody on a metal-organic framework (MOF)-graphene oxide nanocomposite modified glassy carbon electrode (Anti-CEA/Ag-MOF/GO/GCE). Ag-MOF/GO nanocomposite was prepared on the GCE surface using the ultrasonic irradiation method, and Anti-CEA antibody was subsequently immobilized on the surface. Analysis of the crystal structure and morphology of the modified electrode using FE-SEM and XRD revealed that the correct combination of GO nanosheets and Ag-MOF nanoparticles produced a high surface area to trap the antibodies. Electrochemical tests utilizing the CV and DPV methods revealed that the immunosensor's sensitivity, stability, and selectivity were improved by Anti-CEA/Ag-MOF/GO/GCE. Results showed that, with a detection limit of 0.005 ng/mL, the change in the reduction peak current was inversely correlated with the logarithm concentration of CEA in the range of 10-3 to 5000 ng/mL. The suggested CEA immunosensor's applicability in a human serum sample was investigated, and findings of analytical studies via standard addition technique for both ELISA and DPV assays revealed that significant agreement existed between the outcomes of the two assays. Additionally, the recoveries ranged from 99.00% to 99.25%, and all relative standard deviations (RSDs) for the sample detections were below 5.01%, indicating satisfactory accuracy in results measured with the proposed CEA immunosensor, indicating that the prepared CEA immunosensor in this study can be used in clinical applications and human fluids.

Polymerase incorporation of fluorescein or rhodamine modified 2′-deoxyuridine-5′-triphosphates into double-stranded DNA for direct electrochemical detection

The 2′-deoxyuridine-5′-triphosphates modified with fluorescein (dUTP-Fl) or rhodamine (dUTP-Rh) were tested as bearers of electroactive labels and as proper substrates for polymerases used in polymerase chain reaction (PCR) and isothermal recombinase polymerase amplification (RPA) with the aim of electrochemical detection of double-stranded DNA (dsDNA) amplification products. For this purpose, electrochemical behavior of free fluorescein and rhodamine as well as the modified nucleotides, dUTP-Fl and dUTP-Rh, was studied by cyclic (CV) and square wave (SWV) voltammetry on carbon screen printed electrodes. Both free fluorescein and dUTP-Fl underwent a two-step oxidation at the peak potentials (Ep) of 0.6–0.7 V and 0.8–0.9 V (phosphate buffer, pH 7.4). The reduction peaks of fluorescein and dUTP-Fl were registered between –0.9 V and −1 V, but they did not depend on concentration. The free rhodamine and dUTP-Rh have demonstrated the well-defined oxidation peaks at 0.8–0.9 V. In addition, the distinct reduction peaks at Ep between –0.8 V and −0.9 V were registered for both rhodamine and dUTP-Rh. The dUTP-Fl and dUTP-Rh were further tested as substrates to incorporate an electroactive label into 210 or 206 base pair long dsDNA amplicons generated either by PCR or RPA. Among two dUTP derivatives tested, dUTP-Fl revealed significantly better compatibility with PCR and RPA, producing the full-size amplicons at 50–90% substitution of dTTP in the reaction mixture. In the PCR, the best compromise between amplicon output and labeling was achieved at the dUTP-Fl : dTTP and dUTP-Rh : dTTP molar ratios of 70% : 30% and 20% : 80% in the PCR mixture, respectively, allowing the direct electrochemical detection of amplicons at micromolar concentrations. Alongside with fluorescence DNA assays, the fluorescein and rhodamine modified dUTP appear as promising electroactive labels to develop direct electrochemical DNA assays for detecting PCR and RPA products.

A comparative study on silicon-based negatrode materials in metallic cavity electrode and button half cell — Uncovering unseen microscopic and dynamic features

The electrochemical characterization of lithium storage materials using the button cell is commonplace, but it is also tedious and time-consuming. Also, the results are often affected by the use of the binders and separator membranes, and by the electrode forming and cell assembly methods. To study the changes in materials before and after dis-/charging, one has to break up the button cell and disturb the packing structure of electrode. In this work, the metallic cavity electrode made of copper (Cu-MCE) was used to study silicon-based negative electrode (negatrode) materials during electrochemical de-/lithiation. The initial apparent reaction area (i.e. the contacting area between the Cu substrate and the active materials, 0.785 mm2) of the Cu-MCE was much smaller than that of the half-button cell (153.86 mm2), reducing significantly the overall current and hence polarization in the Cu-MCE. Powders of commercial silicon and phosphorus-doped silicon (P-doped Si) were tested in the Cu-MCE and a conventional button cell. Cyclic voltammograms (CVs) recorded using the Cu-MCE showed full activation in the first cycle, unlike the button cell whose CVs expanded continuously beyond 5 cycles. Current peaks on the CVs of the Cu-MCE agreed with the expected redox reactions but were more pronounced. The subtle differences between P-doped Si and pure Si could also be revealed by the Cu-MCE with the current peaks becoming more obvious, apparently due to modification in material structures and improved ion transport dynamics. The peak currents on the CVs of the Cu-MCE were plotted against the square root of scan rate (v1/2), showing non-linearity for the two oxidation peaks at 0.35 and 0.54 V, indicating both diffusion and surface of the delithiation processes. Linear plots were obtained for the two reduction peaks at 0.165 and 0.245 V with comparable slopes (−0.024 and 0.029 mA mV−1/2 s1/2), confirming diffusion control with insignificant polarization. However, similar analyses of the button cell revealed diffusion control in both oxidation and reduction, indicating slower dynamics with large polarization to delithiation. More importantly, the Cu-MCE can be inspected directly after dis-/charging without any disturbance, and provides unseen variation in the packing structure, particle morphology, and elemental information of the active materials. It is hoped that the higher accuracy, better details, and greater efficiency offered by the Cu-MCE for studying the intrinsic electrode reaction characteristics of Si-based electrode materials can be extended to other powdery materials for charge storage.

One-step electrodeposition of silver nanoparticles on multi-walled carbon nanotubes to fabricate an Ag-NPs@MWNTC&CPE sensor for the detection of the toxic antibiotic ronidazole in doped chicken liver and muscle

In this work, a simple and innovative fabrication strategy was developed by electrodeposition procedures to combine a film of deposited silver nanoparticles (Ag- NPs) on multi-walled carbon nanotubes to fabricate an Ag- NPs@MWNTC&CPE sensor to detect the active principle of Ronidazole. The physicochemical nature of Ag- NPs@MWNTC&CPE nanocomposite, their texture and morphology were characterized by XRD and SEM. The electrochemical results were performed using cyclic voltammetry, ESI and differential pulse voltammetry techniques. Under optimal experimental conditions, a highly electrocatalytic activity is observed, the reduction reaction of Ronidazole is controlled by a diffusion process with the participation of four electrons and four protons, and a strong potential shift of the reduction peak was measured at -0.58 V/ Ag- NPs@MWNTC&CPE vs Ag/AgCl. The developed sensor shows good selectivity in the presence of metal ions, biomolecules and similar nitro-containing drugs. The results showed that the cathodic current peak was linearly proportional to the concentration of Ronidazole in the range of 1.0×10−4 to 1 ×10−7 M with a detection limit of LOD=2.01×10−8M. To analyze the practicality of the technique for the determination of Ronidazole in real samples of spiked chicken liver and muscle with satisfactory recoveries.

Phosphate-driven H2O2 decomposition on DNA-bound bio-inspired activated carbon-based sensing platform for biological and food samples.

Hydrogen peroxide (H2O2) is one of the most important reactive oxygen species (ROS). Increased endogenous H2O2 levels indicate oxidative stress and could be a potential marker of many diseases, including Alzheimer's, cardiovascular diseases, and diabetes. However, consuming H2O2-incorporated food has adverse effects on humans and is a serious health concern. We used salmon testes DNA with bio-inspired activated carbon (AC) as an electrocatalyst for developing a novel H2O2 sensor. The phosphate backbone of DNA contains negatively charged oxygen groups that specifically attract protons from H2O2 reduction. We observed a linearity range of 0.01-250.0μM in the H2O2 reduction peak current with a detection limit of 2.5 and 45.7nM for chronoamperometric and differential pulse voltammetric studies. High biocompatibility of the sensor was achieved by the DNA, facilitating endogenous H2O2 detection. Moreover, this non-enzymatic sensor could also help in the rapid screening of H2O2-contaminated foods.