Oxidation Peak Research Articles

Electrochemical Characteristics of Ambarella Peel Waste as Liquid Electrolyte for Zn-Cu Biobattery

This study focuses on the electrochemical characterization of Zn-Cu bio-battery cells utilizing electrolytes derived from ambarella peel waste. The primary objectives are to determine the half-cell and full-cell characteristics of these bio-batteries at various concentration ratios and to identify the optimal concentration ratio for maximum performance. Cyclic voltammetry analysis of the half-cells revealed an oxidation peak at 0.5 V vs Ag/AgCl, corresponding to the conversion of uronic acid to aldaric acid. Additionally, two reduction peaks were observed: hydrogen ion reduction to H2 at 0 V vs Ag/AgCl and water reduction at –0.42 V vs Ag/AgCl. The rate-determining step analysis indicated that the redox reactions in the ambarella peel electrolyte solution were surface reactions. The highest rate constant (ks) of 0.722 ± 0.05 s–1 was observed at a 1:2 concentration ratio. This ratio also resulted in the highest battery capacity of 0.0816 mAh and the maximum power density of 16.13 mW/m2. The study concluded that the 1:2 concentration ratio of ambarella peel waste electrolyte solution is optimal, outperforming the 1:1 and 1:3 ratios in terms of battery capacity and power density.

Tripartite Detection and Sensing of Toxic Heavy Metals Using a Copper-Based Porphyrin Metal-Organic Framework.

The detection of heavy metals in water sources is a critical concern for environmental preservation and public health. However, current electrochemical heavy metal sensors suffer from high sensing limits, cross-sensitivity, and poor selectivity. In this work, we present the possibility of an electrochemical sensor based on a copper (Cu) metal-organic framework for the detection of lead, cadmium, and mercury by replacing Cu metal nodes. The working electrode consists of a ∼5 μm thin layer of copper- tetracarboxyphenylporphyrin (Cu-TCPP) sheets that are adsorbed on a glassy carbon electrode (GCE). Upon interaction with Pb2+, Cd2+, and Hg2+, these ions are adsorbed on and incorporated into the metal nodes of the MOF. The adsorbed metallic species can be oxidized to the ionic form (Pb → Pb2+) electrochemically, which results in an oxidation response and enables the quantitative detection of these metals. The oxidation peak currents follow a (mostly) bimodal linear regression with a sensing range of up to 30 μM dependent on the deposition time and an ultralow limit of detection (LoD) of up to 5 nM. The system displays robust and selective sensing in saturated solutions of counterions and interfering metal ions (low error margins of <10%). This work represents the first report of a Cu-TCPP-modified GCE anode as an effective electrode for the sensitive detection of multiple heavy metals and an in-depth study into the Cu replacement kinetics of the Cu-MOF.

Electrochemical study of an enhanced platform by electrochemical synthesis of three-dimensional polyaniline nanofibers/reduced graphene oxide thin films for diverse applications

This work reports the electrochemical fabrication of thin films comprising polyaniline nanofibers (PANI) in conjunction with graphene oxide (GO) and reduced graphene oxide (rGO) on ITO substrate, along with examining the electrochemical properties, with a focus on the influence of the substrate and electrolyte in the electrodeposition methods. The study explores the electrochemical characteristics of these thin films and establishes a flexible framework for their application in diverse sectors such as sensors, supercapacitors, and electronic devices. It analyzes the impact of the substrate and electrolyte in electrodeposition techniques. The effects were studied using techniques such as cyclic voltammetry and chronoamperometry. The fabrication process of PANI/GO and PANI/rGO thin films involved the integration of rGO within PANI via electropolymerization, conducted under sulfuric acid. GO was synthesized by modifying the well-known Hummers’ method and characterized by X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). SEM showed the diameters of the formed PANI were between 40 and 150 nm, which helped to intertwine the rGO nanosheets with PANI nanofibers to form thin films. The electrochemical behavior of the PANI/rGO thin films was examined using cyclic voltammetry (CV) and chronoamperometry in different electrolytes, including sulfuric acid (H₂SO₄) and potassium nitrate (KNO₃). The CV profiles exhibited distinct oxidation and reduction peaks, with variations in the voltammogram morphology attributed to the nature of the electrolyte and the substrate employed during the electrodeposition process. These results highlight the critical role of both the substrate and electrolyte in governing the electrochemical performance of PANI/rGO thin films. The findings from this study demonstrate a versatile approach for the fabrication of PANI/graphene-based thin films with tunable electrochemical properties, and such a strategy has great application to fabricating other thin film composites for supercapacitors or other control source frameworks requiring enhanced charge storage and electrochemical responsiveness.

Molybdenum-doping to enhance the deprotonation ability of nickel-based hydroxide electrocatalysts for ethanol oxidation

With technological advancements, the practical application of ethanol oxidation reaction (EOR) is becoming increasingly promising, yet the need for higher ethanol concentrations highlights the growing importance of the deprotonation ability (Ni2+ to Ni3+) of the catalyst. The deprotonation ability is the key step for nickel-based catalysts in EOR, as it is essential for Ni2+ to continuously undergo deprotonation to transform into Ni3+ in order to maintain the continuous EOR. Herein, we developed Mo-doped Ni(OH)2 nanosheets by a hydrothermal method. The Mo-doped Ni(OH)2 nanosheets show excellent EOR performance due to the high valence doping of Mo, the onset potential of the oxidation peak (Ni2+ to Ni3+) appears at a position with a small overpotential,. The in-situ Raman spectroscopy technique further characterized the increase in NiOOH in the process of EOR. The Mo-doped Ni(OH)2 nanocomposite catalyst facilitates the oxidation of Ni2+ into Ni3+. Based on the above theoretical guidance, Mo-doped Fe/Ni(OH)2 nanosheets was designed and synthesized. The outstanding EOR performance of the Mo-Fe/Ni(OH)2-3 showed a potential of 1.352 V at 10 mA cm−2. The catalyst was used to design three-electrode reversible zinc-ethanol-air battery (T-RZEAB), which effectively overcomes the opposing kinetic and thermodynamic requirements for EOR and oxygen reduction reaction (ORR) catalysts in the oxygen electrode. The charging voltage of T-RZEAB with Mo-Fe/Ni(OH)2-3 is 240 mV lower than that of a traditional zinc-air battery at 25 mA cm−2.

Fabrication of a molecularly imprinted poly(methyl methacrylate) decorated graphite electrode for detection of aloe emodin in Aloe vera

In this work, the authors represent a comprehensive approach for the development and validation of a novel graphite-supported molecularly imprinted poly(methyl methacrylate) electrode for the selective and sensitive detection of aloe emodin (AE) in aloe-based cosmetic products. The electrocatalytic activity of the electrode was evaluated using cyclic voltammetry and differential pulse voltammetry techniques in phosphate buffer saline. Surface morphology, structural characteristics, and imprinting endorsement were investigated using field emission scanning electron microscopy, Fourier-transform infrared spectroscopy, and UV-Vis spectroscopy. Under the optimal conditions, the electrode showed an oxidative differential pulse voltammetry peak at -0.2931±0.011 V (vs. Ag/AgCl, saturated KCl). The current was increased linearly with increasing concentrations of AE from 0.0005 to 350 µM, with a low detection limit of 0.0003 µM. The voltammetric analysis has been validated by reverse-phase high-performance liquid chromatography (RP-HPLC) methods. A partial least square regression model was developed to correlate the results obtained from the proposed system with the reference values obtained by RP-HPLC. The model showed a high prediction accuracy of 95.95 % for the detection of AE in cosmetic samples. The developed electrode provides a low-cost, rapid, easy, and convenient method for the detection of AE in cosmetic products, offering potential benefits for quality control and safety assessment in the cosmetic industry.

Synthesis, structure, and solution chemistry of mixed-ligand oxidovanadium(IV) complexes incorporating ONO donor hydrazone ligands

Four mixed-ligand oxidovanadium(IV) complexes, [VIVO(L1-4)(phen)], 1-4, incorporating tridentate dibasic ONO donor hydrazone ligands (H2L1-4, general abbreviation H2L) derived from the condensation of 2-picolinyl hydrazide with 2-hydroxy acetophenone and its 5-substituted derivatives as primary ligands and 1,10-phenanthroline (phen) as auxiliary ligand have been synthesized in excellent yields. The complexes were characterized by elemental analyses, magnetic susceptibility measurements, and various spectral (e.g. IR, UV–Vis and EPR) studies. The molecular structure of one of the four complexes has been determined by single-crystal X-ray diffractometry. In 1, the hydrazone ligand is meridionally disposed of, coordinating through one enolic-O, one phenolic-O, and one imine-N. The other basal position is occupied by one pyridine-N of the phen moiety. The axial positions are occupied by one oxido-O atom and the other pyridine-N atom of the phen moiety. The complexes are paramagnetic with one unpaired electron (μeff ≈ 1.73 BM), suggesting no interaction with the neighboring molecules and are EPR active. The complexes display two d-d transitions, one near 725 and the other near 840 nm due to d xy → d xz , d yz and d xy → d x 2 − y 2 transitions, respectively. The other d-d transition associated with d xy → d z 2 transition was not observed as it falls in the UV region, which is masked by highly intense intra-ligand transitions. The complexes display one-electron oxidation peaks in the +0.75 to +0.89 V vs. Ag/AgCl region in the CH3CN solution that show a linear relationship with the Hammett parameter (σ) of the substituents in the aryloxy ring.

Facile synthesis of green graphite-based (Ni/Cu/N) MOF composite for a methanol oxidation reaction

Recently, direct methanol fuel cells (DMFCs) have been regarded as the greatest energy-producing owing to their low operating temperature, high production rate of methanol, and low greenhouse gas emission. However, the energy conversion efficiency of the DMFCs is still unsatisfactory due to the slow kinetics of the fuel oxidation reaction. So, an economic electrocatalyst with high efficiency and good stability is still needed. Herein, low-cost nanocomposites of (Ni/Cu/N) MOF and palm pollen-derived G-graphite were prepared with different ratios namely, (1:1), (1:2), and (2:1) through a solvothermal reaction. The nanocomposites were characterized via X-ray diffraction (XRD), Scanning electron Microscopy (SEM), Fourier transform infrared (FTIR), Thermal gravimetric analysis (TGA), and, (Brunauer–Emmett–Teller) technique (BET). Electrodes have been tested as electro-catalysts for methanol-oxidation reaction (MOR) in a basic medium. As revealed from the cyclic voltammetry measurements, all electrodes exhibit a good response to MOR, being the nanocomposite with the ratio between (Ni/Cu/N) MOF and G-graphite (2:1) is the best with an oxidation peak current density of 55 mA/cm2 at a scan rate of 50 mV/s, with an onset potential of 0.35 V, and stability reaches 96 %. The electrochemical impedance spectroscopy (EIS) test showed that the ratio (2:1) has the lowest charge transfer resistance, RCT, of 5.21 Ω which confirms its higher electrochemical activity. This superior performance of the (Ni/Cu/N) MOF and G-graphite (2:1) over other reported MOF-based electrocatalysts is attributed to the synergistic effect of the (Ni/Cu/N) MOF electrocatalyst, wherein Ni and Cu provide redox electrocatalytic active sites for MOR while the G-graphite contributes towards the chemical stability and electrical conductivity of the electrode, respectively. The good activity and stability of the prepared electrodes suggest the potential use of these electrodes as electrocatalysts for MOR in direct methanol fuel cells (DMFCs).This study opens the venue for valorizing the natural wastes derived graphitic material as stable supporting material in Mof based composites electrodes for MOR.

Minimally Invasive Real-Time Monitoring for Rapid and Sensitive Diagnosis of Spinal Cord Injury.

Spinal cord injury (SCI) is a serious neurological injury that is currently extremely difficult to cure clinically. SCI involves numerous pathophysiological processes, and microRNAs (miRNAs) play an important role in these processes. Meanwhile, miRNAs have received a lot of attention for their role in other diseases as well. Therefore, the detection of disease-related miRNAs is important for the study of disease development, treatment, and prognosis. With the rapid development of molecular biology, the traditional detection methods of miRNA can no longer meet the needs of experiments. Electrochemical detection methods are widely used because of their excellent detection performance. Here, we designed an electrochemical sensor prepared using borosilicate glass microneedle electrodes for real-time monitoring of miR-21-5p expression in vivo after SCI. The sensor showed a good linear relationship between the oxidation peak current value and the concentration of miR-21-5p in the concentration range 0-2 fM (Y = 12.025X + 90.396, R2 = 0.98). The limit of detection (LOD) of the sensor was 0.3667 fM. The experimental results showed that the borosilicate glass microneedle electrochemical sensor achieved fast, accurate, highly sensitive, highly specific, highly stable, and reproducible monitoring of miR-21-5p. More importantly, the electrochemical sensor has a better clinical translation prospect, which is important for the research of clinical diseases.

Detection of piperine content in black pepper using a molecular imprinted poly(N,N-dimethylacrylamide) embedded graphite electrode: A machine learning based prediction approach

The paper presents a molecular imprinted graphite electrode for selective and sensitive detection of piperine (1-Propylpiperidine) in Piper nigrum (black pepper). Poly(N,N-dimethylacrylamide) (PDMAM) was utilized as a functional monomer directing polymerization of uniform molecularly imprinted polymer (MIP) layers on the surface of the graphite layer using ethylene glycol dimethacrylate (EGDMA) as cross-linker with piperine (PIP) as template molecules. The formation of imprinting, non-imprinting, and elution of analytes within the polymer matrix were studied by field emission scanning electron microscope (FESEM), Fourier transform infrared (FTIR), UV–visible (UV–Vis) and X-ray photoelectron spectroscopy (XPS). The electrochemical response of piperine was evaluated through differential pulse voltammetry (DPV) using a PDMAM-MIP@G electrode that showed an oxidation peak at 1.25 ± 0.15 V. Under optimized experimental conditions, DPV peak currents were linear over two concentration ranges (0.001–1 µM and 1–200 µM). A limit of detection (LOD) was found to be 0.0006 µM. Developed electrode yielded high selectivity, sensitivity (12.92 µA/µM (lower linear range) and 0.33 µA/µM (upper linear range)), promising reproducibility, long-term stability (3.85 % decrease in response over 28 days), and interference immunity. The developed PDMAM-MIP@G electrode was applied to real samples using four branded pepper powder procured from local market and the sensor data was recorded. A convolutional neural network (CNN) driven prediction model has been proposed to predict the piperine concentration. Among the four CNN models tested, the best model, averaged over 50 runs, achieved a mean absolute error (MAE) of 0.268, a mean prediction error of 2.35 %, and a R-squared value of 0.93 on the testing set when compared with reference values obtained from reverse-phase high-performance liquid chromatography (RP-HPLC).

New Brønsted–Lowry acid Co(II) complexes: Synthesis, characterization, and investigation of electrochemical application for sensing of salbutamol

In recent years, the employment of transition metal complexes for working electrode surface modification for sensor fabrication has become an area of research direction. Based on this, in this study, three Co(II) complexes: Co(phen)Cl2 (CoC12H8N2Cl2) (C1), and Brønsted–Lowry acids Co(phen)(HTA)Cl (CoC16H13N2O6Cl)(C2), and Co(phen)(HTA)2 (CoC20H18N2O12)(C3) were synthesized and characterized using various techniques such as UV–Vis, FT-IR, ICP OES, TGA, DTA, pXRD as well as electrolytic conductivity, and acid-base property analysis. C and C3 were found polycrystalline whose size falls within the nano range of 50 and 51 nm, respectively. The synthesis was intended to get materials for voltammetrically modifying glassy carbon electrodes for the determination of salbutamol. Salbutamolis a short-acting β2adrenergic receptor agonist that is applied for opening the medium and large airways in the lungs and eventually treats asthma among other problems. The electrochemical application of the synthesized materials was studied by fabricating through electropolymerization of C1, C2, and C3 on glassy carbon electrodes. The poly(C1)/GCE, poly(C2)/GCE, and poly(C3)/GCE) revealed effective surface area is 0.174 cm2, 0.183 cm2, and 0.281 cm2, respectively, and electrochemical catalysis of the materials increased with the number of the tartrate. The Rct values are 5686, 242, 216, and 185 Ω cm2, while the Cdl values are 9.93 × 10−8, 5.35 × 10−6, 1.25 × 10−5, and 2.72 × 10−5, for bare GCE, poly(C1)/GCE, poly(C2)/GCE and poly(C3)/GCE, respectively. Similarly, the rate of charge transfer (k°) increased significantly on the modified electrode compared to the bare GCE. Salbutamol demonstrated a single well-shaped irreversible oxidative peak at the modified electrodes in the ascending order of poly(C1)/GCE, poly(C2)/GCE, and poly(C3)/GCE when compared to a bare GCE.

Maleic anhydride esterified potato starch as the binder in silicon nanoparticles anode for lithium-ion batteries

Potato starch is a natural carbohydrate binder. Starch has hydroxyl groups that can promote interaction with silicon particles using multifaceted hydrogen bonds. Maleic anhydride esterified potato starch can produce a binder that maintains the cycle stability of lithium-ion batteries. Fourier-transform infrared spectroscopy spectra show wavelengths of 1776 cm−1 and 1855 cm−1. Thermal gravimetric analysis curves decreased in weight percent by 80 % at 286 °C. Carbon-13 nuclear magnetic resonance spectra show high peaks at 3.37 ppm, 3.65 ppm, 4.56 ppm, 5.09 ppm, and 6.22 ppm. Scanning electron microscope images show that the morphological change in esterified starch was due to the increased length of starch and the maleic anhydride grafted onto the starch granules. The cyclic voltammetry curve shows that the reduction peak is around 0.16 V, and the oxidation peak is around 0.38 V and 0.56 V. Nyquist plots show a small half circle, indicating that the electrode's solid-electrolyte interphase layer is low. The cycling performance shows a capacity of 1950 mAh/g.

Electro‐Oxidation of Ibuprofen and Metoprolol Using a Manganese Oxide Platform

AbstractPharmaceutical compounds, such as ibuprofen and metoprolol, are of increasing concern due to their persistence in the environment and potential adverse effects on human health. In this work, we developed an electrochemical sensor system for the determination of ibuprofen and metoprolol based on a modified manganese oxide nanoparticle (MnO2NPs) on a screen‐printed carbon electrode (SPCE). The characterisation of MnO2NPs modifier was investigated via Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy techniques, Uv/vis spectroscopy, and small‐angle X‐ray scattering spectroscopy. The electrochemical behaviour of the MnO2NPs was studied using differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques. The optimum experimental conditions were investigated by examining the effects of scan rates, pH on the CV responses, and electrolytes on the DPV response. The MnO2NPs modified electrode demonstrated enhanced catalytic activity in the electro‐oxidation of both ibuprofen and metoprolol. The oxidation peaks of ibuprofen and metoprolol were observed at +1.14 V and +1.46 V, respectively, for the MnO2NPs/SPCE sensor. The sensor's limit of detection was 3.81 pM and 4.6 pM respectively and its linear response was from 0.97–5.82 pM. Furthermore, interference and stability studies were conducted to evaluate the performance of the MnO2NPs/SPCE sensor under optimum conditions, which resulted in a good performance. The proposed sensor was successfully used for the determination of ibuprofen and metoprolol in the application of real water samples.

Oxidation Potential of 2,6-Dimethyl-1,4-dihydropyridine Derivatives Estimated by Structure Descriptors

Linear relationships, expressing the electrochemical properties of molecules as functions of structure, give insight into the associated electrochemical process and are a tool for prediction. Many biological activities rely on water-based dissociation, making electrochemical properties a bridge between structure and activity. Motivated by a previous study, a replica is made here on a different dataset in order to validate/invalidate the previously reported results. There are several methods for obtaining structure-based descriptors. Some of the methods have been devised to account for molecular topology, some to account for molecular geometry, and others to account for both. Two methods are involved here to derive structure-based descriptors and further obtain structure–property relationships (FMPI and ChPE). In order to express structure descriptors, both FMPI and ChPE express first the topology of the molecule, using the heavy atoms identity matrix and the heavy atoms adjacency matrix, both square symmetric matrices in the belief that symmetry is one major factor of molecular stability. A set of 2,6-dimethyl-1,4-dihydropyridine derivatives with oxidation peak potentials and coulometrically determined number of electrons experimental data is subjected to the search for structure–activity relationships. Even if the 2,6-dimethyl-1,4-dihydropyridine is a symmetric compound (of Cs point group), their derivatives are generally not symmetric (9 out of 24 are asymmetric). The dataset is subjected to descriptive and inferential statistics in order to filter out the most relevant structure–activity relationship. The geometry is built using three levels of theory (one from molecular mechanics and two others from density functionals, of which one accounts for the interaction with water as solvent). One challenge of picking one out of two reported measured values is dealt with by calculating the likelihood associated with the two choices. Relevant structure–activity models are extracted and discussed. The use of in vivo (in water, SM8 model) models in geometry optimization (from MMFF94 and B3LYP and to M06 + Water SM8) results in a precision gain, but this is, in most of the cases, not statistically significant, and this can be considered a negative result.

Green Synthesis of Electroactive Magnesium Ferrite Nanoparticles for the Selective Determination of Mefenamic Acid in Blood, Pharmaceutical Products, and Wastewater

Mefenamic acid (MNA) treats sports injuries, rheumatoid arthritis, and osteoarthritis. However, improper use/disposal of MNA results in the accumulation of toxic metabolites that may serious disease. The purpose of this study is to fabricate a nano ferrite-based electrochemical sensor for robust, and sensitive determination of MNA. Magnesium ferrite nanoparticles (MgFe4O7-NPs) were synthesized using a green approach using a Mentha leaf extract. The analytical characterization of MgFe4O7-NPs displayed a hexagonal structure and a particle size of less than 21 nm with rough and porous morphology. The synthesized MgFe4O7-NPs were used to fabricate an electrochemical sensor by modifying a glassy carbon electrode (MgFe4O7-NPs/GCE). The cyclic voltammetry (CV) characterization of the electrode confirms excellent redox and diffusion control for electroactive species. Thus, the MgFe4O7-NPs/GCE was used to determine MNA by differential pulse voltammetry (DPV). The results showed a linear relationship between oxidation peak current and concentration of MNA from 10 × 10−9 to 2.30 × 10−4 M (R 2 = 0.9918) with a detection limit of 1.12 × 10−9 M. The analytical performance of the fabricated sensor has been evaluated for MNA in blood samples, pharmaceutical tablets, and water samples with satisfactory results.

Study Effect of rGO Addition on Photocatalytic Activity of TiO2 in Reducing Carbon Dioxide Using Electrochemical Method

Abstract Increasing the carbon dioxide (CO2) concentration every year can cause various environmental problems. One of the technologies to reduce CO2 is carbon capture. The semiconductor of TiO2 is widely used as a photocatalyst to reduce CO2. However, TiO2 has limitations in absorbing light in the visible region because it has a large band gap value. Besides, TiO2 has a fast recombination of electron-hole pairs so it can reduce photocatalytic activity. An addition of rGO is expected to cover the shortcomings of TiO2 because rGO has good conductivity and a small band gap. We synthesized rGO-TiO2 photocatalyst and measured its activity in capturing and converting CO2 using an electrochemical method. By using voltage difference as an electron driver in reacting with CO2 we observe the reaction between electrons and CO2. The measurements were carried out under irradiated and unirradiated conditions. The CV measurements show that the rGO-TiO2 electrode with 60% rGO content has reduction and oxidation peaks. Based on the electrochemical half-reaction table, the reduction peaks in unirradiated conditions indicate the conversion of CO2 to CH4 and (COOH)2, while under irradiated the reduction peak indicates the formation of HCOO− and CH2CH2. The results show that by using the rGO-TiO2 composite as an electrode not only reduces CO2 but also converts the CO2 into hydrocarbon.

Synthesis, Characterization and Electrochemical Performance of Bi2S3/Rice Husk-Based Activated Carbon Composites As Lithium Ion Battery Anodes

This study investigates the impact of hydrothermal duration on bismuth sulfide/activated carbon composites (Bi2S3/AC) by varying the duration to 8, 24, and 48 hours. The primary aim is to delineate the composite characteristics and electrochemical performance of Bi2S3/AC composites, aiming to produce anodes for lithium-ion batteries with high capacity, excellent cyclic stability, and minimal volume expansion. Activated carbon derived from rice husks was synthesized via a carbonization process and chemical activation using H3PO4 as an activator. Subsequently, the synthesis of Bi2S3/AC composites used bismuth nitrate pentahydrate and thiourea precursors through the hydrothermal method that involved three variations of hydrothermal duration: 8, 24, and 48 hours, denoted as BC8, BC24, and BC48, respectively. The FTIR test indicates the presence of Bi-S, C=C, and C-O groups in the three composite products, signifying the existence of bismuth sulfide and activated carbon. The XRD result reveals orthorhombic crystal forms in the composites, while the SEM-EDX mapping illustrates particle morphologies resembling flower-like shapes. These compositions comprise Bi 74.16%, S 11.37%, and C 10.43%. The GSA test suggests a mesoporous pore size in these composites. In final result, BC24 exhibits the highest electrical and ionic conductivity, measuring 2.12 × 10−3 S.cm−1 and 2.057 × 10−4 S.cm−1, respectively. The CV data of the BC24 composite indicates two reduction and oxidation peaks in the first cycle. Charge-discharge test on the BC24 composite exhibits a specific charge capacity of 445.51 mAh/g and a discharge capacity of 364.24 mAh/g.

Determination of silver ions in distilled water by stripping voltammetry at a Nafion-coated gold electrode in combination with quartz crystal microbalance and electrochemical impedance spectroscopy

Here, we propose a stripping voltammetric method for Ag+ ion determination in distilled water utilizing screen-printed Au electrodes coated with Nafion (Nafion/Au screen-printed electrodes). The concentration of Ag+ in pure water was determined by linear sweep voltammetry (LSV) after silver deposition on the Nafion/Au electrode. The anodic stripping peak current increased linearly with the concentration of Ag+ ion in the range from 1 ppm to 22 ppm. The LSV oxidative peak current was increased by extending the silver deposition time from 300 s to 500 s. Repetitive LSV measurements revealed satisfactory reproducibility of the Nafion/Au screen-printed electrodes. The detection mechanism was elucidated by recording mass changes of the Nafion/Au electrode with a quartz crystal microbalance (QCM), and by determining changes in the low-frequency capacitance of the Nafion/Au electrode by electrochemical impedance spectroscopy (EIS). The observed changes in mass and capacitance confirmed Ag+ accumulation and release processes at the Nafion/Au electrodes, in good agreement with stripping voltammetry. The combination of stripping voltammetry, QCM and EIS allowed a detailed characterization of the ion transfer, deposition and stripping processes at the Nafion/Au electrodes in presence of Ag+ ions. The Nafion/Au screen-printed electrode enabled voltammetric determination of low Ag+ concentrations in distilled water, without any sample pretreatment nor addition of supporting electrolyte.

Electroactive RuPt NPs programmed dual-channel electrochemical sensor for methyl mercaptan monitoring

The accurate and sensitive detection of methyl mercaptan (CH3SH) was of great significance for food corruption monitoring. Electroactive labels engineered electrochemical sensors possessed tailorable electrochemical responses, and showed potential prospects for CH3SH monitoring. In comparison to a single electrochemical signal, electroactive nanocomposites with multiple electrochemical responses not only provided multi-channel sensing signals for accurate detection, but also increased the peak intensity for sensitive detection. Herein, RuPt NPs were designed and explored to possess two independent and non-interfering electrochemical oxidation peaks at 0.75 V and -0.73 V. The formation of metal-SH covalent bonds between electroactive sites of RuPt NPs and CH3SH induced the changes of two electrochemical oxidation peaks. By utilizing the sum intensity of two electrochemical peaks as detection signal, a dual-channel electrochemical sensor was established for CH3SH detection in the range of 1 μM-1 mM, and had a low limit of detection (LOD) of 300 nM. This work gave a new insight into promoting more electroactive nanocomposites with multiple signals for accurate and sensitive electrochemical detection applications.

Modification of Screen Printed Carbon Electrode-Gold Nanoparticles (SPCE-AuNPs) for Detection of Mercury in Cosmetics

The cosmetics industry in Indonesia has experienced a significant increase of 12.6% from 2022 to June 2023, with 1025 industries having a positive impact on the Indonesian economy. Apart from that, it has triggered a number of naughty manufacturers to use dangerous chemicals in their cosmetic products such as mercury (Hg). Therefore, it is important to develop a fast and sensitive method for detecting mercury in cosmetics using SPCE-AuNPs. This research was carried out by synthesizing gold nanoparticles (AuNPs) using the reducing agent sodium citrate (Na3H5C6O7) with varying concentrations and characterization of several chemical instruments. Furthermore, SPCE was modified by AuNPs, its performance and application were tested to detect mercury in cosmetic cream using cyclic voltammetry (CV). SPCE-AuNPs provides an electrochemical response with higher oxidation and reduction peaks than bare SPCE with an oxidation peak at a potential of 0.1 V to 0.3 V and a reduction peak at -0.05 V to 0.05 V at a scan rate of 0.01 V/s to 0.03 V/s. This shows a good electrochemical response so it can be used for application to detection of mercury in cosmetic samples. The SPCE modified using AuNPs can potentially be used as a sensor for mercury detection in cosmetics.

Design of high-performance electrochemical sensor based on SnS2 nanoplates and ionic liquid-modified carbon paste electrode for determination of hydrazine in water samples

Designing effective and accurate analytical techniques to determine hydrazine is essential for preserving the environment. Herein, an electrochemical sensor based on a carbon paste electrode (CPE) modified with SnS2 nanoplates (SnS2NPs) and ionic liquid (IL) was presented for determination of hydrazine in water samples. The SnS2NPs were synthesized using the hydrothermal method and characterized through field emission scanning electron microscope, Fourier transform infrared spectrometer and energy dispersive spectroscopy. The use of cyclic voltammetry in electrochemical investigations has shown that incorporating IL and SnS2NPs in an electrochemical sensor significantly improves its efficiency. These results in a considerable increase in the oxidation peak current and a decrease in the oxidation peak potential of hydrazine compared to an unmodified CPE. The method of differential pulse voltammetry was utilized to accurately measure the quantity of hydrazine. The SnS2NPs/ILCPE showed improved sensing capabilities, resulting in a noticeable sensitivity of 0.0747 µA/µM and a low limit of detection of 0.05 µM for a broad linear range of hydrazine concentration from 0.08 µM to 450.0 µM. In addition, the SnS2NPs/ILCPE sensor was successfully utilized to measure the amount of hydrazine present in water samples, with a recovery range of 96.0 to 104.4 %. The relative standard deviation was found to be lower than 3.6 % (n = 5), indicating that the developed sensor is suitable for accurately determining hydrazine in water samples with high sensitivity.