Cyclic Voltammetry Studies Research Articles

A coronene diimide based radical anion for detection of picomolar H2O2: a biochemical assay for detection of picomolar glucose in aqueous medium.

Coronene diimide functionalized with 4-(2-nitrovinyl)phenyl (CDI 2) serves as a precursor for generating a stable radical anion (CDI 2˙-) using H2S as a reductant in 40% H2O-THF solution in the NIR region with stability up to >50 min. The optical, cyclic voltammetry (CV), current-voltage (I-V) and electron paramagnetic resonance (EPR) studies revealed the formation of the radical anion (CDI 2˙-). The addition of a strong oxidant NOBF4 quenches the radical anion (CDI 2˙-). The aggregation studies revealed that CDI 2 exists in the aggregated state in 40% H2O-THF solution, which points to the possibility of stabilization of the radical anion in the aggregates. The radical anion (CDI 2˙-) was explored for the detection of 58.27 pM H2O2 in aqueous medium with the naked eye colour change from green to light yellow. The biochemical assay involving the radical anion (CDI 2˙-) and glucose oxidase (GOx) enzyme can be used for the detection of 16 pM (UV-vis method) and 82.4 pM (fluorescence method) glucose. The naked eye colour change from green to light yellow (daylight) and a colorless non-fluorescent solution to a green fluorescent solution (365 nm) allow the detection of 1 nM glucose.

Construction of a binder-free PANI-CQD-Cu electrode via an electrochemical method for flexible supercapacitor applications.

In recent years, flexible hybrid supercapacitors (FSCs) have played a significant role in energy storage applications owing to their superior flexibility and electrochemical properties. In this study, carbon quantum dots (CQDs) were prepared from ascorbic acid via a hydrothermal method and physical and chemical characterizations were performed. Then, the carbon quantum dots (CQDs) were doped with polyaniline (PANI) and copper (Cu) to form a PANI-CQD-Cu composite coated on carbon cloth (CC) using an electropolymerization method. In the polymerization process, CQDs bind with the PANI chain and form a PANI-CQD-Cu composite. The prepared electrode's functional group and surface morphology were characterized through XRD, Raman, BET, XPS and SEM with EDAX studies. The electrochemical properties of the PANI-CQD-Cu electrode were investigated using cyclic voltammetry, impedance spectroscopy and galvanostatic charge-discharge study. The capacitance value of PANI-CQD-Cu was 1070 mF cm-2 at 5 mA cm-2 (1070 F g-1 at 1 A g-1), which was higher than that of PANI (775 mF cm-2). Moreover, a flexible asymmetric supercapacitor (FASC) based on an activated carbon/PVA-H2SO4/PANI-CQD-Cu device was fabricated, which exhibited outstanding energy and power densities of 23.10 μW h cm-2 and 0.978 mW cm-2, respectively. The capacitance value remained at 92% after 3000 cycles. The outcome results indicated that the PANI-CQD-Cu-coated CC electrode material can be a promising electrode material for practical energy storage applications.

Development of an Electroanalytical Method for Ronidazole Determination in Environmental and Food Matrices Using Boron-Doped Diamond Electrode

A novel electroanalytical approach is presented for the determination of ronidazole in environmental and food matrices by applying a cathodically pretreated boron-doped diamond electrode and the square-wave adsorptive cathodic stripping voltammetry technique. From the studies of cyclic voltammetry to investigate the electroactivity of the ronidazole molecule, the occurrence of an irreversible cathodic process was verified, which was more efficiently detected using the cathodically pretreated boron-doped diamond electrode compared to the anodically pretreated electrode. Still on the electrochemical response of ronidazole, the effects of pH and scan rate were studied and, its apparent diffusion coefficient was determined by chronoamperometry (8.20 × 10−6 cm2 s−1). Under optimal experimental conditions, the analytical curve obtained for ronidazole was linear in two concentration ranges (12.70 to 63.40 µmol L−1 and 76.04 to 126.2 µmol L−1), with a limit of detection of 2.55 µmol L−1. For intra- and inter-day repeatabilities, relative standard deviations of only 2.7 and 3.5% were verified, which demonstrated the stable analytical response of the electrode. Recovery percentages ranging from 96 to 100% were achieved in the analysis of natural water and whole milk samples. Therefore, the proposed electroanalytical method shows satisfactory analytical performance towards ronidazole determination in varied matrice samples.

Siloxide tripodal ligands as a scaffold for stabilizing lanthanides in the +4 oxidation state.

Synthetic strategies to isolate molecular complexes of lanthanides, other than cerium, in the +4 oxidation state remain elusive, with only four complexes of Tb(iv) isolated so far. Herein, we present a new approach for the stabilization of Tb(iv) using a siloxide tripodal trianionic ligand, which allows the control of unwanted ligand rearrangements, while tuning the Ln(iii)/Ln(iv) redox-couple. The Ln(iii) complexes, [LnIII((OSiPh2Ar)3-arene)(THF)3] (1-LnPh) and [K(toluene){LnIII((OSiPh2Ar)3-arene)(OSiPh3)}] (2-LnPh) (Ln = Ce, Tb, Pr), of the (HOSiPh2Ar)3-arene ligand were prepared. The redox properties of these complexes were compared to those of the Ln(iii) analogue complexes, [LnIII((OSi(OtBu)2Ar)3-arene)(THF)] (1-LnOtBu) and [K(THF)6][LnIII((OSi(OtBu)2Ar)3-arene)(OSiPh3)] (2-LnOtBu) (Ln = Ce, Tb), of the less electron-donating siloxide trianionic ligand, (HOSi(OtBu)2Ar)3-arene. The cyclic voltammetry studies showed a cathodic shift in the oxidation potential for the cerium and terbium complexes of the more electron-donating phenyl substituted scaffold (1-LnPh) compared to those of the tert-butoxy (1-LnOtBu) ligand. Furthermore, the addition of the -OSiPh3 ligand further shifts the potential cathodically, making the Ln(iv) ion even more accessible. Notably, the Ce(iv) complexes, [CeIV((OSi(OtBu)2Ar)3-arene)(OSiPh3)] (3-CeOtBu) and [CeIV((OSiPh2Ar)3-arene)(OSiPh3)(THF)2] (3-CePh), were prepared by chemical oxidation of the Ce(iii) analogues. Chemical oxidation of the Tb(iii) and Pr(iii) complexes (2-LnPh) was also possible, in which the Tb(iv) complex, [TbIV((OSiPh2Ar)3-arene)(OSiPh3)(MeCN)2] (3-TbPh), was isolated and crystallographically characterized, yielding the first example of a Tb(iv) supported by a polydentate ligand. The versatility and robustness of these siloxide arene-anchored platforms will allow further development in the isolation of more oxidizing Ln(iv) ions, widening the breadth of high-valent Ln chemistry.

Strategic electrochemical oxidation of vinblastin sulfate (an anticancer drug) via PVP-functionalized strontium oxide nanoparticles.

Cancer is a primary cause of death worldwide, and considerably impacts mortality rates in low- and middle-income countries. The rise in chemotherapeutic patients and toxicity of cytotoxic agents highlight the need for reliable analytical methods to detect these compounds. The current study presents a simple and straightforward method for producing polyvinylpyrrolidone functionalized strontium oxide nanoparticles (PVP-SrO NPs). The synthesized PVP-SrO NPs were applied as a sensitive sensor to detect vinblastin sulfate (VNB) (an anticancer drug). The synthesized PVP-SrO NPs were characterized using different characterization techniques. Fourier transform infrared spectroscopy (FTIR) confirms the functionality of synthesized PVP-SrO NPs. The sharp intense peaks of X-ray diffraction spectroscopy (XRD) confirm the crystalline nature of NPs, scanning electron microscopy (SEM) confirm the nanobeads like morphology, and energy dispersive spectroscopy (EDS) reveals the presence of Sr and O at 68.3% and 23% respectively. The electrochemical impedance spectroscopy and cyclic voltammetry studies revealed that the PVP-SrO/GCE is more conductive than bare GCE with an R ct value of 960.4 Ω compared to 2440 Ω. The sensor exhibited a wide linear dynamic range for VNB (0.05 to 60 μM) with low LOD 0.005 μM, and LOD 0.017 μM. The proposed sensor was successfully used for monitoring VNB in human blood serum samples with a satisfactory percent recovery from 96% to 103%. The fabricated sensor exhibits better performance than the reported sensors in terms of processing, simplicity, cost-effectiveness, energy consumption, and enhanced efficacy in a very short time.

Charge-compensated nido-carborane derivatives in the synthesis of iron(II) bis(dicarbollide) complexes.

A series of stable iron(II) bis(dicarbollide) derivatives [8,8'-(RNHC(Et)HN)2-3,3'-Fe(1,2-C2B9H10)2] (R = Pr, R = Ph, (CH2)2OH, (CH2)3OH, (CH2)2NMe2) was prepared starting from FeCl2 or [FeCl2(dppe)] and the corresponding nido-carboranyl amidines [10-RNHC(Et)HN-7,8-C2B9H11]. In a similar way, the reactions of the oxonium derivatives of nido-carborane with FeCl2 in tetrahydrofuran in the presence of t-BuOK lead to the corresponding stable oxonium derivatives iron(II) bis(dicarbollide) [8,8'-(RR'O)2-3,3'-Fe(1,2-C2B9H10)2] (RR' = (CH2)4, (CH2)2O(CH2)2, (CH2)5; R = R' = Et), which can be alternatively prepared by the reaction of the parent iron(II) bis(dicarbollide) with tetrahydrofuran or 1,4-dioxane in the presence of Me2SO4. The cyclic voltammetry studies of the synthesized iron(II) bis(dicarbollide) derivatives revealed that the introduction of amidinium and oxonium substituents leads to a significant increase in the Fe2+/Fe3+ redox potential relative to the parent iron(II) bis(dicarbollide). The redox potentials of the oxonium derivatives are close to the redox potential of ferrocene and somewhat lower than redox potentials of sulfonium and phosphonium derivatives of iron(II) bis(dicarbollide).

Understanding the Reaction Mechanism and Kinetics of Mediated Li-O2 Batteries Using Flow Set-Ups and Cyclic Voltammetry

Li-O2 batteries are very promising candidates for electromobility because of their very high theoretical energy density. Moreover, they are composed of abundant materials, as opposed to Li-ion batteries, which would make them a greener and cheaper alternative. The principal reaction in Li-O2 batteries is the formation of lithium peroxide during discharge via the oxygen reduction reaction (ORR), that is then oxidised during the charge by the oxygen evolution reaction (OER). One of the major challenges of Li-O2 batteries is related to the insulating nature of their discharge product, that significantly limits the capacity and hinders performance. A strategy to overcome this is by using redox mediators (RMs), which shuttle electrons from the electrode surface to the solution and thus facilitate a solution-based mechanism for the formation of large crystals. Understanding the reaction kinetics of these RMs can therefore aid in increasing the battery performance.Quinones, specifically 2,5-Di-tert-butyl-1,4-benzoquinone (DBBQ),is a commonly used discharge RM in this type of batteries. However, their reaction kinetics and how these vary with different electrolyte conditions are not yet well understood. DBBQ undergoes two single electron reductions, whose potentials and kinetics vary with salt concentrations and solvent having a direct effect on its ability to mediate the ORR.In this work, we have developed a Li-O2 flow cell to study the reaction mechanism and kinetics of DBBQ, and performed cyclic voltammetry (CV) studies to better understand how these vary with changing solvent and salt conditions. In the Li-O2 flow set-up the battery is positioned outside the nuclear magnetic resonance (NMR) magnet and plastic tubing then runs through the NMR and electron paramagnetic resonance (EPR) spectrometers. In this way, the reduction of the DBBQ can be monitored while the battery is cycling. In the proton NMR, the neutral DBBQ signals disappear on discharge as the singly reduced DBBQ semiquinone monoanion is a radical. The fast electron exchange between the neutral and radical species broaden out the NMR signals on discharge as the EPR signal grows. On charge, the neutral DBBQ signal reappears and the EPR signal disappears. The Li-O2 flow set-up is very sensitive to air and moisture exposure as the tubing is not perfectly impermeable to them. Therefore, having the CVs as a complementary method to study the reaction mechanisms and kinetics is very useful.We have developed a theoretical framework of Li-coupled electron transfer reactions that can predict the electrochemical kinetics in the presence of high and low donor number solvents and used to quantify thermodynamic and kinetic parameters. We define E0 app and k0 app as the apparent thermodynamic and kinetic parameters that describe the overall system and can be derived from the Nernst equation and Butler Volmer kinetics. These overall descriptors depend on the pathway the reaction takes (Figure 1). The different pathways in different solvents/salts are due to changes in the Li+ solvation strength as well as the competing ionic association of the counter anion.Experimentally, we have shown that in three different solvents, DME, tetraglyme and DMSO the behaviour of DBBQ can be explained by this theoretical framework. In DME, the DBBQ behaviour is most reminiscent of pathway 1 where the kinetics slow down with increasing Li+ concentration. In DMSO the kinetics present a maximum at Li+ concentrations around 1M. Simulations and fitting of the CV experiments in DMSO for the first reduction are in good agreement with pathways 2 and 3, while in tetraglyme it is harder to explain the trends as they do not fit into just one of the pathways.In conclusion we have studied the mechanism and kinetics of DBBQ as a RM for Li-O2 batteries with an in-situ flow set up and CVs and build a theoretical framework to understand how these vary in different electrolyte conditions. This method can be extended to study both the second reduction of DBBQ and other discharge and charge RMs for Li-O2 batteries. Figure 1

Novel plasmonic Z‐scheme-based photocatalysts and electrochemical aptasensor for the degradation and determination of epirubicin

A novel type of aptasensor and Z-scheme-based photocatalyst was fabricated and used for photodegradation as well as estimation of epirubicin (EP) using the nanocomposite of carbon nano-onion (CNO), flower-like MoS2, and dendritic Ag. We have developed a new type of sensor design having the ability to detect and differentiate between various molecules with greater sensitivity and accuracy than the existing sensors. The biosensor based on aptamer immobilization on a screen-printed carbon electrode was modified with CNO/MoS2/Ag dendrites nanocomposite synthesized by hydrothermal and co-precipitation methods. Materials were fully characterized by FE-SEM, TEM, XRD, DRS, and XPS. Cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) studies were performed in 1 mM K3[Fe(CN)6]/K4[Fe(CN)6] for a quantitative assessment of EP in terms of charge transfer resistance (Rct) changes. The difference in Rct increased linearly with increasing EP concentration from 0.1− 500 nM with a detection limit of 0.03 nM. For achieving better response, aptamer concentration, incubation time, and modifier content were optimized, and the measurement of EP in real samples was also performed. The photocatalytic degradation of EP was investigated using CNO/MoS2/Ag dendrites with a band gap of 1.7 eV to show that superoxide anion and hydroxide radicals significantly affected the degradation of EP during 50 min, and 99.50 % of EP was degraded.

Electrosynthetic Carboxylation of Biomass-Derived Compounds in Ionic Liquids

Chemical production from renewable biomass and CO2 is a sustainable alternative to the current fossil based chemical industry as it will enable significant reduction of greenhouse gas emissions. CO2 is a desirable chemical building block as it is abundant and steadily becoming more available as carbon capture technologies are maturing. However, activation and valorization of CO2 remains a challenge due to its thermodynamic stability and kinetic inertness. CO2 activation has been demonstrated with thermal, (photo)catalytic and electrochemical methods, and especially the electrochemical approach allows for mild reaction conditions and high efficiency. In this context, the synthesis of carboxylic acids by electrosynthetic carboxylation represents an interesting strategy for valorization of biomass-derived alcohols and CO2.In electrosynthesis, a supporting electrolyte salt is needed in the reaction medium to ensure high conductivity. A major drawback of using such a supporting electrolyte salt is increased waste generation. However, by replacing supporting electrolyte salts with recyclable ionic liquids the waste generation can in theory be avoided. In addition, ionic liquids can provide a highly conducting reaction medium with a sufficiently large electrochemical window allowing CO2 activation to take place. Furthermore, room temperature ionic liquids are especially suitable for electrosynthetic carboxylation reactions due to their high CO2 absorption capacity.In this work, we present preliminary results, including cyclic voltammetry and reaction optimization studies, for electrosynthetic C-O activation and carboxylation of biomass-derived compounds with room temperature ionic liquids as electrolytes.

Electrochemical Oxidation of Cobalt at a Platinum Electrode in a Chloride Medium

Cobalt is a highly important metal that is widely used in lithium-ion batteries, cemented carbide, magnetic materials, chemical, and medical industries. The current global cobalt reserves (in total around 6.9 million tons) are unevenly distributed mainly between the Democratic Republic of Congo (48%) and Australia (21%) [1]. One of the main sources of cobalt is nickel production where Co is as a byproduct. Nevertheless, research related to cobalt extraction from both primary or secondary resources must be accelerated to address the current imbalance between supply and demand, that has resulted in cobalt being classified as highly critical by the EU [2]. Currently, primary and secondary raw materials are refined using pyro-hydrometallurgical or hydrometallurgical processing routes, followed by e.g. cobalt crystallization, or electrowinning. Battery grade cobalt salts can be further subjected for calcination to form battery grade oxides. In the current study, we investigate a novel approach of electrifying metallurgy - attempting for direct electrochemical cobalt recovery as cobalt oxide from a hydrometallurgical chloride based process solution.Potentiostatic electrolysis was performed in synthetic cobalt chloride solution, mimicking the industrial concentrations. SEM and EDX were used for microstructural characterization and determination of sample compositions, respectively. Cyclic voltammetry (CV) was also carried out to understand the anodic behavior of cobalt on the Pt electrode. CV studies suggested the formation of different cobalt-containing phases and the obtained precipitates in potentiostatic experiments were identified as Co3O4 and CoOOH. However, the precipitate composition was strongly dependent on the conditions of electrolysis, such as potential, temperature, and pH. At the highest studied potential (1150 mV vs. Ag/AgCl) the precipitate obtained had a saturated black color indicating desired formation of Co3O4, while at lower potentials the brown colour indicated dominance of other phases. The microstructure of the electrodes due to different potentials was investigated by SEM, indicating also morphology changes as a function of recovery potential. EDX analysis suggested that the precipitates recovered included not only cobalt and oxygen but also traces of chloride ions.Overall, this study highlights the possibility of cobalt recovery in oxide form in a chloride medium as an alternative method for the recovery of cobalt from industrial process solutions. The proposed approach can be suggested as an alternative to the traditional process of crystallization or electrowinning. In addition, cobalt obtained in a form of oxide is an important class of materials characterized by good electrochemical, catalytic, and optical properties and can be used as a final product in a variety of applications if quality requirements can be achieved. Acknowledgment The ENICON project (https://enicon-horizon.eu/) has received funding from the European Union’s Framework Program for Research and Innovation Horizon Europe under Grant Agreement No. 101058124 References Rahimpour Golroudbary, S.; Farfan, J.; Lohrmann, A.; Kraslawski, A. Environmental Benefits of Circular Economy Approach to Use of Cobalt. Global Environmental Change (2022) 76, doi:10.1016/j.gloenvcha.2022.102568.Blengini, G.A.; EL Latunussa, C.; Eynard, U.; Torres de Matos, C.; Wittmer, D.; Georgitzikis, K.; Pavel, C.; Carrara, S.; Mancini, L.; Unguru, M.; et al. Study on the EU’s List of Critical Raw Materials (2020) Final Report., doi:10.2873/904613.

Tunable capacitive charge storage of NiCoLDH@rGO for high-energy capacitor: Performance of flexible solid-state capacitor

The compositionally tunned pristine nickel cobalt layered double hydroxides (NiCoLDHs) and NiCoLDH@reduced graphene-oxide (NiCoLDH@rGO) composites generated via the simple single-pot solvothermal method. The synthesized NiCoLDH and the NiCoLDH@rGO composites were characterized through powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transformed infra-red (FT-IR) spectroscopy, scanning electron microscope (SEM) equipped with energy dispersive X-ray analysis (EDAX), high-resolution transmission electron microscope (HR-TEM), and X-ray photoelectron spectroscopy (XPS) techniques. The XRD, Raman and FT-IR data confirmed the formation of the NiCoLDH with presence of carbonate and nitrate ions in the basal space. Enhanced basal length was observed for the NiCoLDH@rGO composites. The three-electrode system was constructed to analyse the cyclic voltammetry and Galvanostatic charge-discharge studies in 1 M KOH confirmed that the pristine LDHs and the composites are electrochemically active, and the capacity could be tuned by varying (Ni2+/Co3+) mole ratio or the rGO content. The charge storage kinetics in NiCoLDH@rGO was performed through Dunn's approaches and the Power Law, affirmed as the (Ni2+/Co3+) ratio or the rGO content is increased in the composite the capacitive contribution is increased for the charge storage. The NC@RG10 (NiCoLDH with 10 wt% rGO) composite electrode could deliver an enhanced specific capacity of 963C g−1 at a current rate of 1.5 A g−1. Consequently, pristine LDH or composites as positive electrode and rGO as negative electrode was fabricated using the CR-2032 coin-type hybrid capacitor. The laboratory prototype pristine hybrid capacitor (NiCoLDH|1 M KOH|rGO) delivered an enhanced specific energy of 56 Wh kg−1 at specific power of 810 W kg−1, whereas the composite hybrid device (NC@RG10|1 M KOH|rGO) having NC@RG10 electrode delivered an enhanced specific energy of 166 Wh kg−1 at specific power of 638 W kg−1. The NC@RG10 composite-based hybrid device exhibited excellent stability with coulombic efficiency as high as 99 % even at the 10,000th charge−discharge cycle. Reduced aggregation and enhanced conductivity leading to significant capacitive contribution in the NC@RG10 composite is due to the existence of rGO and responsible for the excellent charge storage performance. The fabricated hybrid capacitor powered a red LED on a single charge for 40 min. Fascinatingly, a flexible solid-state hybrid capacitor was also fabricated that delivered an impressive specific energy of 28 Wh kg−1 at a specific power of 553 W kg−1 at a 180° bent angle.

Cyclic voltammetry studies of malonamide hydrazone derivative and its electrochemical effect on CdCl2

The purpose of this study is to detect the electrochemical reduction of a novel N-(benzo[d]thiazol-2-yl)-3-oxo-3-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)propenamide ligand (o-H2BMP) at varying pH by using a gold electrode in the presence of tetra butyl ammonium bromide as a supporting electrolyte at room temperature. The outcomes results showed that the effective reduction mechanism of the o-H2BMP ligand consumes 8 electrons and 8 hydrogen ions at pH 5, which belong to the reduction of azomethine and two carbonyl groups at (0.0518 V – 0.678 V), respectively. Also, the electrochemical behavior of Cd(II) ions in a cell containing 0.1 M KCl in 50 % (DMSO-water) mixed solvent by using glassy carbon electrode was proceeded with two electrons transfer as Cd+2/Cd0 in reversible mechanism. This work presents a novel structural analysis of the complexes that can be formed in solution and which exhibit stochiometric ratios of (M:L, 1:1, 2:3, 1:2). Moreover, the degree of reversibility of Cd(II) ions redox behavior was evaluated in the absence/presence of the o-H2BMP ligand which indicated that the redox behavior of Cd(II) ions more reversible in the case of free Cd(II) according to the ∆Ep, α, and kh values. While, in the presence of the o-H2BMP ligand, the degree of reversibility was decreased and the number of electrons transferred in the rate-determining step increased which confirming the complexation reaction of Cd(II) with the ligand.

Nitrogen doped biomass derived carbon and BiVO4 composite for simultaneous detection of furazolidone and chloramphenicol

An efficient electrochemical sensor based on nitrogen functionalized biochar (N-BC) and BiVO4 hybrid nanocomposites was prepared, and used for simultaneous detection of furazolidone (FZD) and chloramphenicol (CAP) with highly sensitive and selective in food sample. The N-BC was obtained by acid activation method which using biomass waste (rice halls) as the raw and processed material and urea as the nitrogen source, which was further mixed with BiVO4 to synthesized N-BC/BiVO4 composite. The surface morphology and structured properties were characterized by Scanning electron microscopic (SEM), Nitrogen (N2) adsorption/desorption isotherms, X-ray powder diffraction (XRD) patterns, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and electrochemical impedance studies of N-BC/BiVO4 film on GCE showed that electron transfer rate in [Fe (CN)6]3−/4− solution was rapider than bare GCE, N-BC/GCE and BiVO4/GCE. The sensor was successfully used for the detection of FZD and CAP with wide linear ranges of 0.1–1600 μM for FZD and 0.1–3200 μM for CAP, low limit of detection of 0.053 μM for FZD and 0.087 μM for CAP (S/N = 3), respectively. In addition, the proposed sensor has shown good anti-interference ability, reproducibility and stability, and obtained satisfactory results for respective or simultaneous detection of FZD and CAP in milk sample.

Bis(pyrazolyl)methane supported cobalt (II) complexes as sensitizers in dye-sensitized solar cells

A series of eight cobalt(II)-based dyes was synthesised using pyrazole and bis(pyrazolyl) methane derivatives. The new dyes were equipped with suitable anchoring functionalities, such as, carboxylic acid or thiocyanate groups, either on the ligand backbone or as a co-ligand to the metal center. All the synthesized compounds were characterized by various spectro-analytical techniques. The HOMO and LUMO energy gap of the dye molecules were determined theoretically by using B3LYP method. The opto-electronic and electrochemical properties of the dyes were analyzed by UV–visible spectroscopy and cyclic voltammetry studies respectively. The photo sensitizing capacity of all the synthesized cobalt-complexes was determined with a help of solar cell constructed using dye-TiO2 coated FTO anode, platinum coated FTO cathode and an iodine based redox mediator. Among the tested compounds, complexes C8 and C9 which contain carboxylic anchoring groups exhibited the best performance.

Metal‐Free Electrochemical [3+2] Cycloaddition between α‐Amino Carbonyls and Tosylmethyl Isocyanide en route to Substituted Imidazoles

AbstractThe established strategy unveils a metal and mediator‐free electrochemical [3+2] cycloaddition approach among α‐amino carbonyls and tosylmethyl isocyanide (TosMIC) fabricating substituted imidazole scaffolds. Implementation of electro‐redox conditions on this cycloaddition approach eliminates the essential requirement of transition metal catalysts and chemical oxidants. A wide variety of different functionalities are well tolerated under this reaction condition, contributing to the substrate scope and applicability. Several control experiments and cyclic voltammetry studies suggest an electro‐oxidation triggered successive C−C and C−N bond formations followed by rapid aromatization for constructing the five‐membered core structure.

One-Pot template free synthesis of bimetallic alloy Pt-M/C (M = Fe, Co & Cu) with improved activity for electrocatalytic oxidation of methanol

We prepared a simple, one-step synthesis of Pt-M (M = Co, Cu & Fe)/C supported on Vulcan-XC-72 carbon using the polyol reduction method. The morphology, structure and elemental composition of the prepared catalysts were confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Electrochemical characterization including electrochemical impedance, cyclic voltammetry and chronoamperometry were studied to compare the electrochemical activity of the as-prepared catalyst with standard 20 wt % Pt/C. From transmission electron microscopy studies, the estimated average particle size for PtFe/C, PtCo/C and PtCu/C were 16, 12 and 10 nm respectively. In cyclic voltammetry studies, the PtFe/C catalyst exhibited the maximum current density for electrooxidation of methanol (14.88 mA cm−2), compared to PtCu/C (9.96 mA cm−2), PtCo/C (4.66 mA cm−2) and Pt/C (2.34 mA cm−2). Also, the negative sweep onset potential and greater If/Ib ratio verified the enhanced activity of the PtFe/C catalyst. The stability of the catalyst was studied using chronoamperometric methods, which reveals the slow decay of the prepared catalyst and higher current density for initial and final time intervals. Impedance studies confirm that the PtFe/C catalyst exhibits the smallest semicircle, suggesting a significantly higher electrooxidation rate in comparison to the other catalysts. The electrocatalytic activity of the prepared catalyst follows the order: PtFe/C > PtCu/C > PtCo/C > Pt/C.

Interfacial molecular structure of phosphazene-based polymer electrolyte at the air-aqueous interface using sum frequency generation vibrational spectroscopy

The change induced in the physicochemical properties of polymer while hosting ions provides a platform for studying its potential applications in electrochemical devices, water treatment plants, and materials engineering science. The ability to host ions is limited in very few polymers, which lack a detailed molecular-level understanding for showcasing the polymer-ion linkage behavior at the interfacial region. In the present manuscript, we have employed sum frequency generation (SFG) vibrational spectroscopy to investigate the interfacial structure of a new class phosphazene-based methoxyethoxyethoxyphosphazene (MEEP) polymer in the presence of lithium chloride salt at the air-aqueous interface. The interfacial aspects of the molecular system collected through SFG spectral signatures reveal enhanced water ordering and relative hydrogen bonding strength at the air-aqueous interface. The careful observation of the study finds a synchronous contribution of van der Waals and electrostatic forces in facilitating changes in the interfacial water structure that are susceptible to MEEP concentration in the presence of ions. The observation indicates that dilute MEEP concentrations support the role of electrostatic interaction, leading to an ordered water structure in proximity to diffused ions at the interfacial region. Conversely, higher MEEP concentrations promote the dominance of van der Waals interactions at the air-aqueous interface. Our study highlights the establishment of polymer electrolyte (PE) characteristics mediated by intermolecular interactions, as observed through the spectral signatures witnessed at the air-aqueous interface. The investigation illustrates the polymer-ion linkage adsorption effects at the interfacial region, which explains the macroscopic changes observed from the cyclic voltammetry studies. The fundamental findings from our studies can be helpful in the design and fine-tuning of better PE systems that can offer improved hydrophobic membranes and interface stability for use in electrochemical-based power sources.

Development of Novel Cobalt Tungstate Anchored on MCM-41 for Sensitive Detection of Dopamine in Human Urine Samples

In this study, MCM-41/CoWO4 nanocomposite has been used for electrochemical detection of dopamine neurotransmitters. The cobalt tungstate nanoparticles (CoWO4) were synthesized through facile hydrothermal method and MCM-41/CoWO4 nanocomposite was prepared by ultrasonication method. The as-synthesized MCM-41/CoWO4 nanocomposite was characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman techniques. The electrochemical performance of the nanocomposite was examined using electrochemical impedance spectroscopy, cyclic voltammetry, and differential pulse voltammetry studies. The GCE/MCM-41/CoWO4 electrode exhibited a linear range, better sensitivity, and limit of detection (LOD) of 10–170 μM, 0.3361 μA μM−1 cm−2 and 7.2 nm, respectively. Moreover, the GCE/MCM-41/CoWO4 electrode demonstrated good repeatability, reproducibility, and stability. In addition to that, the real sample analysis was conducted using human urine with excellent recovery and RSD percentage.

Electrochemical Detection of Metol through the Cobalt Nickel Oxide Nanosheets Incorporated with MCM-41 Nanospheres Composites Modified Glassy Carbon Electrode

In this study, contaminations of metol (or Elon) in environmental water and industrial wastewater are the major causes of toxicity, which is very harmful to human health and other living things. Hence the determination of metol in high demand is more important. Further, the Mobil Composition of Matter (MCM-41) mesoporous silica nanoparticles incorporated with cobalt nickel oxide (CoNiO2) complex to form MCM-41/CoNiO2 composite modifying the glassy carbon electrode (GCE) used for metol detection. The MCM-41/CoNiO2 composite coated on the GCE surface exhibited fast electron transfer kinetics, improved conductivity, a large surface area, active stability, and improved catalytic efficiency. The structural morphology of the MCM-41/CoNiO2 composite was investigated using several spectroscopic and microscopic techniques. Here, the MCM-41/CoNiO2 composite was verified using different characterization studies such as Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, Energy Dispersive X-ray Analysis, X-ray Diffraction Analysis, and X-ray Photoelectron Spectroscopy. Additionally, the electrochemical investigations have included Electrochemical Impedance Spectroscopy, Cyclic Voltammetry, and Differential Pulse Voltammetry studies. The GCE/MCM-41/CoNiO2 electrode shows a low detection limit of 10 nM and the LOQ value is 0.1 μM with a broad linear response range of 0.1–750 μM, and greater sensitivity of 0.411 μA μM−1 cm−2 under optimal voltammetry.

Enhancing surface area, morphology, and electrocatalytic activity favouring triiodide reduction via surface sulfurization of metal oxide

Herein, a direct anionic exchange method was employed using Thioacetamide (TAA) and Phosphorous Pentasulfide (P2S5) by facile hydrothermal method. The preliminary results confirm that the sulfurization leads to amorphization and formation of MoS2. BET analysis demonstrates the substantial improvement in the surface area from 72.046 m²/g for pristine MoO3 to 104.402 m²/g, and 140.802 m²/g, for TAA and P2S5 treated MoO3 respectively, was achieved upon sulfurization. Cyclic Voltammetry (CV) studies show an excellent triiodide reduction ability in LiI/I redox system which is due to the improvement in electrocatalytically active sites and stability across the CE/electrolyte interface. The lower charge transfer resistance (Rct) values obtained from Electrochemical impedance spectroscopy (EIS) confirm the effective charge carrier transport that improved the conductivity across electrode/electrolyte interface. The power conversion efficiency (PCE) measured under our lab conditions found an improvement for pristine MoO3 i.e. 0.78% to a maximum PCE of 5.48% and 4.12% for the P2S5 and TAA sulfurized MoO3 respectively. In general, this work highlights the use of phosphorous pentasulfide which can also be utilized for direct anionic exchange with the advantage of phosphorous content in resultant products which could greatly improve various physio-chemical properties of the material.