Reduction 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.

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.

Synthetic Cathinones' Comprehensive Screening and Classification by Voltammetric and Chemometric Analyses: A Powerful Method for On-Site Forensic Applications.

The use of synthetic cathinones (SCs) has increased in recent years, posing significant public health problems due to their adverse effects and potential for fatal poisonings. The structural diversity and rapid emergence of new SC analogues create challenges for law enforcement and drug screening techniques. This work presents for the first time the electrochemical detection of SCs using differential pulse voltammetry (DPV) on a boron-doped diamond electrode (BDDE). We analyzed 15 SCs, including well-known compounds such as mephedrone, methylone, and ephylone, revealing distinct electrochemical profiles with two characteristic reduction peaks (R1 and R2). The method was optimized in Britton-Robinson buffer (0.1 mol L-1, pH 8.0) and demonstrated a high selectivity and sensitivity. Multivariate statistical methods, including principal component analysis and hierarchical cluster analysis, classified SCs into six distinct groups. The DPV optimization and analytical parameter determination, including the limit of detection (LOD), were performed for the least electroactive SC, 4'-methyl-α-pyrrolidinohexanophenone, yielding an LOD of 3.8 μmol L-1, suitable for screening street samples. Interference studies with common illicit drugs and adulterants confirmed the selectivity of the DPV-BDDE method. Preliminary identification of SCs in 46 real seized samples was successfully performed using this method with results validated by liquid chromatography-mass spectrometry (LC-MS). The method also identified three SCs not included in the original set: bupropion, benzylone, and dipentylone. The DPV-BDDE method offers a rapid, robust, and portable approach for the selective screening of SCs in forensic applications, demonstrating significant advantages over traditional colorimetric tests.

An innovative homogeneous electrochemistry coupled with colorimetry dual-model sensing strategy for perfluorooctane sulfonate based on Cu@CuO aerogel nanozyme.

Bypreparing Cu@CuO aerogel as a nanozyme which exhibits prominent peroxidase-like (POD) activity, an innovative homogeneous electrochemistry (HEC) coupled with the colorimetry dual-model sensing strategy is proposed to detect perfluorooctane sulfonate(PFOS) for the first time. Cu@CuO aerogel accelerates the oxidation process of colorless o-phenylenediamine to form yellow 2,3-diaminophenazinc (DAP), and meanwhile, DAP as an electroactive substance creates a reduction peak current upon the electrochemical measurements. Interestingly, in the presence of PFOS, the POD activity of Cu@CuO aerogel isinhibited since the specific coordination between PFOS and Cu(II) can cover the active sites, resulting in the color of the sensing system becoming light and the peak current of DAP decreasing. This innovative dual-mode detection method showed excellent electrochemical detection of PFOS in the concentration range 10.0 ~ 1125.0nM with a limit of detection (LOD) as low as 3.3nM and a LOD of 20.8nM in the colorimetric detection in the range 62.3 ~ 875nM. Furthermore, the sensor was successfully used for the analysis of real samples with an RSD value ≤ 6.5%. The successful application of this two-mode sensing method for the determination of PFOS holds promise for the detection of other contaminants in the future.

Tailoring glassy carbon electrode surface with FeBiO3 for electrochemical detection of dinitrophenol isomers

ABSTRACT This study presents a simultaneous, rapid, and highly sensitive electrochemical detection of 2,4- and 2,5-dinitrophenol isomers using an iron bismuth oxide (FeBiO3)-modified glassy carbon electrode (GCE). The FeBiO3-modified GCE exhibited superior electrochemical performance over bare GCE, Bi2O3-modified GCE, and Fe2O3-modified GCE, as demonstrated by electrochemical impedance spectroscopy (EIS) with the potassium ferricyanide (Fe(CN6)3-/4-) standard. The synthesised electrocatalyst FeBiO3 exhibited strong absorption both in the visible and UV regions of the spectrum, attributed to band gap transitions and charge transfer transitions linked to its Bi2O3 and Fe2O3 components. The morphology and the structure of the FeBiO3 were characterised using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), while Fourier transform infrared spectroscopy (FTIR) was employed to analyse the functional groups attached to the surface of FeBiO3. Cyclic voltammetry (CV) clearly demonstrated an increased current and improved peak resolution for the reduction of 2,4- and 2,5-dinitrophenols at the FeBiO3/GCE, compared to the bare GCE. The mechanism shows that the reduction of 2,4- and 2,5-dinitrophenols occurs through interactions with the surface oxygen functional groups of FeBiO3, resulting in the stepwise reduction of their NO2 groups to hydroxyamino compounds and then to nitrosophenols. Using square wave voltammetry (SWV), the reduction peak currents were significantly improved, enhancing detection sensitivity beyond that reported in previous works. A linear range from 1 µM to 1 mm for the dinitrophenol isomers was established, with detection limits of 0.07 µM for 2,4-dinitrophenol and 0.09 µM for 2,5-dinitrophenol. The FeBiO3/GCE electrode showed interferences with mono-nitrophenols and mono-/di-chlorophenols in solution but maintained excellent long-term stability and reproducibility, allowing it to effectively detect dinitrophenol isomers in drinking water, tap water, and wastewater samples.

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.

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.

Functional effects of subsidies and stressors on benthic microbial communities along freshwater to marine gradients.

Leaf litter in coastal wetlands lays the foundation for carbon storage, and the creation of coastal wetland soils. As climate change alters the biogeochemical conditions and macrophyte composition of coastal wetlands, a better understanding of the interactions between microbial communities, changing chemistry, and leaf litter is required to understand the dynamics of coastal litter breakdown in changing wetlands. Coastal wetlands are dynamic systems with shifting biogeochemical conditions, with both tidal and seasonal redox fluctuations, and marine subsidies to inland habitats. Here, we investigated gene expression associated with various microbial redox pathways to understand how changing conditions are affecting the benthic microbial communities responsible for litter breakdown in coastal wetlands. We performed a reciprocal transplant of leaf litter from four distinct plant species along freshwater-to-marine gradients in the Florida Coastal Everglades, tracking changes in environmental and litter biogeochemistry, as well as benthic microbial gene expression associated with varying redox conditions, carbon degradation, and phosphorus acquisition. Early litter breakdown varied primarily by species, with highest breakdown in coastal species, regardless of the site they were at during breakdown, while microbial gene expression showed a strong seasonal relationship between sulfate cycling and salinity, and was not correlated with breakdown rates. The effect of salinity is likely a combination of direct effects, and indirect effects from associated marine subsidies. We found a positive correlation between sulfate uptake and salinity during January with higher freshwater inputs to coastal areas. However, we found a peak of dissimilatory sulfate reduction at intermediate salinity during April when freshwater inputs to coastal sites are lower. The combination of these two results suggests that sulfate acquisition is limiting to microbes when freshwater inputs are high, but that when marine influence increases and sulfate becomes more available, dissimilatory sulfate reduction becomes a key microbial process. As marine influence in coastal wetlands increases with climate change, our study suggests that sulfate dynamics will become increasingly important to microbial communities colonizing decomposing leaf litter.

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.

Evaluation of electrodeposition synthesis of gold nanodendrite on screen-printed carbon electrode for nonenzymatic ascorbic acid sensor

Gold nanodendrite (AuND) is a type of gold nanoparticles with dendritic or branching structures that offers advantages such as large surface area and high conductivity to improve electrocatalytic performance of electrochemical sensors. AuND structures can be synthesized using electrodeposition method utilizing cysteine as growth directing agent. This method can simultaneously synthesize and integrate the gold nanostructures on the surface of the electrode. We conducted a comprehensive study on the synthesis of AuND on screen-printed carbon electrode (SPCE)-based working electrode, focusing on the optimization of electrodeposition parameters, such as applied potential, precursor solution concentration, and deposition time. The measured surface oxide reduction peak current and electrochemical surface area from cyclic voltammogram were used as the optimization indicators. We confirmed the growth of dendritic gold nanostructures across the carbon electrode surface based on FESEM, EDS, and XRD characterizations. We applied the SPCE/AuND electrode as a nonenzymatic sensor on ascorbic acid (AA) and obtained detection limit of 16.8 μM, quantification limit of 51.0 μM, sensitivity of 0.0629 μA μM−1, and linear range of 180–2700 μM (R2 value = 0.9909). Selectivity test of this electrode against several interferences, such as uric acid, dopamine, glucose, and urea, also shows good response in AA detection.

Novel and simple electrochemical sensing platform based on polypyrrole nanotubes/ZIF-67 nanocomposite/screen printed graphite electrode for sensitive determination of metronidazole

Here, a simple, fast, and sensitive voltammetric sensor based on screen printed graphite electrode (SPGE) modified with polypyrrole nanotubes/zeolitic imidazolate framework-67 (PPy NTs/ZIF-67) nanocomposite is introduced for the metronidazole (MNZ) determination. The PPy NTs/ZIF-67 nanocomposite was synthesized and characterized by using X-ray diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques. The developed sensor based on PPy NTs-ZIF-67 nanocomposite modified SPGE shows an obvious reduction peak at −650 mV for MNZ, mainly due to the synergistic effects of the ZIF-67 and PPy NTs. Differential pulse voltammetry (DPV) was found to be the most suitable method for MNZ detection, showing a linear dynamic range of 0.01 to 500.0 µM and a low limit of detection (LOD) of 0.004 µM. In investigating the practicability, the PPy NTs/ZIF-67/SPGE sensor demonstrated efficient practicability with satisfactory recoveries (97.1 % to 103.5 %) and low relative standard deviation (RSD) values of 1.8–3.6 % for MNZ determination in MNZ tablets and urine samples.

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.

Green synthesis of NiO and NiO@graphene oxide nanomaterials using Elettaria cardamomum leaves: Structural and electrochemical studies

An eco-friendly synthetic route was developed for the formation of nickel oxide (NiOaq and NiOet) nanoparticles (NPs) by treating Ni(NO3)2.6H2O with aqueous/ethanolic extracts of Elettaria cardamomum leaves; the same reaction was performed in the presence of graphene oxide (GO) to produce NiOaq@GO and NiOet@GO nanocomposites (NCs), respectively. The NMs were characterized by XRD, FT-IR, SEM, EDX, UV–visible spectroscopy, and TGA-DSC analysis. They were also subjected to electrochemical investigations and photocatalytic degradation of crystal violet (CV) dye. XRD analysis revealed the average crystallite sizes of 8.84–14.07 nm with a face-centered cubic form of NiO NPs and a hexagonal structure of their nanocomposites with GO. FT-IR spectroscopy confirmed the presence of Ni-O vibrations at 443-436 cm−1. SEM images confirmed the spherical morphology of NiO NPs while NiOaq@GO NCs contained randomly aggregated, thin, and wrinkled graphene sheets. NiOaq and NiOet have shown particle sizes of 27.7–30.63 nm which were decreased to 19.33–26.39 nm in their respective NiOaq@GO and NiOet@GO NCs. EDX spectra verified the homogeneous distribution of elements (Ni, O, C) on the surface of the particles. The synthesized NCs have shown smaller band gaps (NiOaq@GO = 3.74 eV; NiOet@GO = 3.34 eV) as compared to their respective NPs (NiOaq = 5.0 eV; NiOet = 3.89 eV). TGA/DSC data was used to find the thermal stabilities, glass transition temperatures, and enthalpies. Cyclic voltammetry measurements exhibited distinct oxidation and reduction peaks. NCs exhibited better potential as electrode materials for supercapacitor applications as compared to their respective NPs. NiOet@GO exhibited the best electrochemical performance and photocatalytic degradation efficiency of CV dye. After 120 min exposure to sunlight, the degradation coefficient of CV was observed to be 82.93, 86.34, 89.99, 90.27 and 81.65 % in the presence of NiOaq, NiOet, NiOaq@GO, NiOet@GO and GO, respectively.

Synthesis and investigation of charge storage characteristics in Ni-MOF/PANI composite as an active electrode material for supercapacitor

This study aimed to develop a more stable and efficient energy storage device, synthesis of nickel-based pristine metal organic framework (MOF) and combined it with the emeraldine base phase of polyaniline (PANI) which is confirmed with XRD, SEM and TEM. Both Ni-MOF and PANI exhibit faradaic (battery-like) behaviour. However, when these two materials are combined, the stability of the resulting material is enhanced. The initial materials, MOF and PANI, exhibit specific capacities of 42 C/g and 72 C/g, respectively. However, when these two materials are combined, their composite exhibits an enhanced specific capacity of 122 C/g. The cyclic voltammetry (CV) analysis shows oxidation and reduction peaks, indicating faradaic behaviour. This behaviour is further confirmed by electrochemical impedance spectroscopy (EIS). Upon comparing it with prior results, the specific capacity appears to be slightly lower. However, it is anticipated to exhibit stronger stability, which is contradictory. The composite material (Ni-MOF/PANI) exhibits remarkable capacitive retention of 99.25 % even after undergoing 5000 cycles, as anticipated. In order to validate the aforementioned findings and determine the extent of the current contribution from capacitive and diffusive control, Dunn's model was employed. The data demonstrates the prevalence of diffusive-controlled (faradaic) current over capacitive current. The highest proportion of current resulting from diffusion is 96 %, achieved at a scan rate of 5 mV/s. The highest proportion of current resulting from capacitance is 24 %, achieved at a scan rate of 300 mV/s. At lower scan rates, the material exhibits a greater faradaic behaviour, whereas at higher scan rates, there is a progressive increase in non-faradaic processes. The insufficient time for diffusive process at higher scan rates is the cause. The Dunn's model with quadratic correction is also performed and comparative results were shown. Overall, the material exhibits more stability and dominance in the faradaic process, which paves the path for improved performance.

Dual Electrochemical Methods for Determination of Anesthetic Procaine

Procaine belongs to a type of medicine in which excessive dosage form creates cardiac problems and many allergenic reactions. Thus, continuous monitoring of this drug and its metabolite is crucial for sustainable health management during treatment. In this study, electrochemical techniques such as square wave voltammetry (SWV) and differential pulse polarography (DPP) are utilized for assaying procaine amounts in standard and pharmaceutical formulations. In SWV, the reduction of diazotized procaine gives a reduction peak at −0.05 V which is directly proportional with procaine hydrochloride concentration, whereas in DPP, the interaction of the drug with lead cation at −0.4 V is followed by the decrease in peak current of the lead cation reduction peak, which is directly proportional with the concentration of the drug. Both methods indicate high accuracy, sensitivity and precision. Linear concentration ranges of both methods are 0.0999–5.996 × 10-7 M for SWV and 0.1999–5.996 × 10-7 M for DPP. The limit of detection (LOD) and limit of quantification (LOQ) are calculated for both SWV and DPP techniques, and found that LOD equals 1.984 × 10-9 M and LOQ equals 6.611 × 10-9 M for SWV, while for (DPP) LOD and LOQ were found to be 3.519 × 10-9 M and 1.173 × 10-8 M, respectively.

Ultrasensitive electrochemical detection of 4-nitrophenol through flower-like mixed transition metal oxide anchored on reduced graphene oxide composites

4-Nitrophenol or para-nitrophenol is an organic water pollutant that has a direct impact on environmental pollution and human health. Therefore, developing sensitive electrochemical sensors is vital for monitoring environmental water samples to detect hazardous 4-nitrophenol. Herein, template-free zinc vanadate (ZV) micro-flowers were synthesized and anchored on reduced Graphene oxide (RGO) to modify the electrode surface for sensing and quantification of 4-nitrophenol. The fabrication of the as-prepared electrode modifier was confirmed by physicochemical and morphological characterizations. The synthesized ZV/RGO/GCE displayed well-defined reductive peak current at the potential of −0.7 V due to the hydrogenation of 4-nitrophenol. The increase in active sites and the larger surface area acquired by ZV and RGO were responsible for efficient sensing toward 4-nitrophenol. Under the optimized experimental parameters, CV and DPV techniques were carried out to investigate the electrochemical performance of ZV/RGO/GCE for the detection of 4-nitrophenol. The resultant cathodic current response was related linearly (0.01 µM to 1955 µM) to the concentration with the LOD of 0.009 µM. The developed sensor exhibited a good recovery range in the real-sample analysis in multiple water systems. The proposed ZV/RGO/GCE functions well as an effective electrode material for the determination of the perilous pollutant 4-nitrophenol in water samples by an electrochemical approach.

H/D Isotope Effects in the Electrochemistry of Electrochromic Iron Hexacyanoruthenate

AbstractThe electrochemical deposition of iron hexacyanoruthenate (Fe−HCR) on gold electrodes was studied in electrolytes prepared with light and heavy water. Cyclic voltammetry of the material during preparation and after transfer to a precursor‐free solution exhibits two reductions peaks in H2O‐based electrolytes but only one reduction peak in D2O‐based electrolytes. The voltammetric behavior changes reversibly upon transfer of the material between D2O‐based and H2O‐based 1 mol L−1 KCl solutions. No clear structural differences between samples prepared in D2O and H2O were detected by means of X‐ray photoelectron spectroscopy (XPS) and polarization modulation infrared reflection absorption spectroscopy (PM IRRAS). We noted a relatively slow exchange of coordinated water and a fast exchange of zeolitic water. Using voltammetric experiments we could rule out simple effects of solution conductivity for K+, participation of H+/D+ in the charge compensation and surface effects on the observed dependence of the peak splitting on the isotopic composition of the solvent. The most likely reason for the observed behavior is the different structure of the H‐bonded water network of coordinated H2O and zeolitic H2O/D2O which is supported by the PM IRRAS data.

Exploring Spectral and Electrochemical Behavior of Hydroxy‐N‐Benzylideneanilines by Integrated Theoretical and Experimental Approaches

ABSTRACTThe present work explored the effect of –OH group substitution (o/p) on the spectral and electrochemical behavior of N‐benzylideneaniline. The geometry optimization of unsubstituted and (o/p)‐OH‐substituted analogs revealed the coplanarity of the molecules. The vibrational spectra of the compounds were computed using density functional theory (DFT) and compared with the experimental data. The observed bands were assigned based on total energy distribution (TED). Predicted electronic absorption spectra from time‐dependent density functional theory (TD‐DFT) calculation were compared with the UV–visible spectra of the molecules. The analysis of the lowest spin‐allowed (singlet‐singlet) excited states divulged possible electronic transition. The o‐substituted benzylideneaniline possessed the lowest highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap among the substituted and unsubstituted analogs. The intramolecular contacts were interpreted using natural bond orbital and localized molecular orbital analysis. The –CH=N– linkage was investigated as a bridge for the electron delocalization from the donor to acceptor moieties. The manifestation of a reduction peak in the cyclic voltammetric studies confirmed the electrochemical behavior in the –OH‐substituted molecule, which was diffusion‐controlled. The discrepancy in the electrochemical property concerning the position of the –OH substituent of the candidate molecules was put forward.

NiCoFeS/rGO nanozyme-mediated multifunctional homogeneous sensing system for ultrasensitive electrochemical assay of pesticides residues in fruits and vegetables

In this work, a homogeneous sensing platform was constructed for ultrasensitive electrochemical organophosphate pesticides (OPs) detection based on nano-enzyme NiCoFeS/rGO with high peroxidase-like activity. In the presence of H2O2, NiCoFeS/rGO catalyst oxidized o-phenylenediamine (OPD) to produce yellow OPDox with strong absorbance and reduction peak current. This activity could be inhibited by thiocholine (TCh) produced by acetylcholinesterase (AChE). However, presence of organophosphates (OPs) could inhibit AChE and reduce TCh production, enabling protect the peroxidase-like activity of NiCoFeS/rGO. So, according to the increased signal of OPDox, the content of OPs could be measured by colorimetric or electrochemical mode. Using electrochemical analysis mode and optimizing experimental conditions, the detection limit was low (9.74fg mL−1) and the linear range was wide (12.5fg mL−1-1.25 ng mL−1). The selectivity, stability reproducibility and practicability of the method were investigated. At the same time, the analysis results of colorimetric and electrochemical method for AChE and colorimetric method for OPs were preliminarily determined, respectively.

Synthesis, Structural, Electrochemical, and DFT Studies of Highly Substituted Nonplanar Ni(II) Porphyrins and Their Intensity-Dependent Third-Order Nonlinear Optical Properties.

We designed and successfully synthesized highly substituted electron-deficient nonplanar Ni(II) porphyrins and their derivatives (1-7) in moderate to good yields. These derivatives were comprehensively characterized by various spectroscopic techniques and single-crystal X-ray diffraction (SCXRD) analysis. SCXRD analysis confirmed the structures of compounds 2, 4, and 7, adopting saddle-shape geometry. These nonplanar porphyrins demonstrated significant bathochromic shifts in their absorption spectra compared to parent NiTPP, attributed to the influence of bulky β-substituents and/or peripheral fusion. π-Extended porphyrins 6 and 7 displayed panchromatic absorption spectra extending into the NIR region. Porphyrins 6 and 7 demonstrated a profound anodic shift (∼400 mV) in their first reduction peak potentials compared to precursor NiTPP(NO2)Br6. The experimental absorption spectral pattern matches the simulated absorption spectra obtained from TD-DFT studies. The femtosecond laser intensity-dependent third-order nonlinear optical studies revealed that NiDFP(VCN)2Br6 (6) and NiDFP(VCN)2(PE)6 (7) displayed giant optical nonlinearities compared to the other porphyrins. Among all, NiDFP(VCN)2Br6 (6) possessed the highest two-photon absorption coefficient (β) and cross-section (σTPA) values in the range of 22-33 × 10-10 m/W and 3.77-6.95 × 106 GM, respectively. These findings suggest that the investigated nonplanar π-extended porphyrins are promising candidates for future optoelectronic applications.