Chronoamperometric Methods Research Articles

Enhanced Glucose Sensing Performance through Controlled Pulsed Laser Deposition of Au Clusters on Anodized Glassy Carbon Electrodes

Diabetes, a global health problem, necessitates precise blood glucose measurement for effective management. Despite their prevalence, enzymatic glucose sensors suffer from sensitivity to temperature and pH and limited lifetime of the enzyme, thus requiring replacement every two weeks (Teymourian et al., 2020). In contrast, non-enzymatic sensors offer enhanced durability, superior sensitivity, and ease of miniaturization, making them promising for the so-called "fourth generation" glucose sensors (Aun et al., 2021). Noble metals like Pt (Kim et al., 2012), Au (Shen et al., 2022), Pd (Elkholy et al., 2019), and Ir (Dong et al., 2018) have emerged as prospective candidates for glucose sensing due to their ability to oxidize glucose at a physiological pH of 7.4. Among these, Au has gained attention due to its remarkable electroactivity for glucose electro-oxidation (Vassilyev et al., 1985), despite its weak chemisorptive properties arising from filled d-orbitals (Hammer & Nørskov, 1995). Various methods have been employed to fabricate nanostructured gold electrodes, encompassing direct electrostatic assembly, covalent linking, polymer entrapment or co-mixing, sol-gel processes, electrochemical etching, and electrodeposition (Dahan et al., 2023). Nevertheless, many of these fabrication approaches entail the use of hazardous chemicals or involve cumbersome procedures, de facto limiting their practical application. As a result, scalable solutions to catalyst fabrication and deposition are needed to seamlessly integrate with the cleanroom process flows to build non-enzymatic glucose sensors.In this study, 7x7mm glassy carbon electrodes (GCs) served as working electrodes in a three-electrode system, with a reversible hydrogen electrode employed as a reference and a Pt mesh as a counter electrode. The GCs underwent meticulous polishing using alumina slurry of varying sizes (1μm, 0.3 μm, and 0.01 μm). Subsequently, they were anodized in 1M KOH at 1.8V for 2 hours in ambient air conditions. The electroactive area of the GCs was determined by measuring the capacitance with EIS before and after anodization, and by later dividing by the specific capacitance (13 μF/cm2). A remarkable tenfold increase in surface area was observed after anodization. With a custom-built cluster deposition apparatus (Figure 1a), four monolayers of gold clusters were deposited on three bare GCs (BareGC) and three anodized ones (AnGC). Field Emission Scanning Electron Microscopy (FE-SEM) images captured the morphology of BareGC and AnGC, both with and without clusters (Figure 1b). Atomic force microscopy was also utilized to complement the morphology study of the electrodes' surface. Grazing Incidence X-ray Diffraction (XRD) at 0.5 degrees revealed a peak corresponding to the Au(111) plane in Au+BareGC (Figure 1c). Rutherford backscattering was employed to quantify the gold loading on the samples. To facilitate the generation of active Au-OH species on the nanoclusters, the electrodes underwent cycling between 0.43V and 1.53V in 0.1M PBS, devoid of chlorides. Subsequently, the sensing performance towards glucose was evaluated via chronoamperometric methods, maintaining the potential at 0.884V under stirring conditions (250 rpm). Gradual increases in glucose concentration were applied in steps of 0.25 mM and later in 1 mM increments up to 7 mM (Figure 1d).Both Au+BareGC and Au+AnGC electrodes exhibited an extremely linear response (R²=0.99) within the 0.25 mM to 7 mM linear range. After calibration, the electrodes underwent cycling in 0.5 M H2SO4 between 0.015V and 1.715V (vs RHE). The gold oxide reduction peak was integrated (Figure 1e), allowing estimation of the electroactive surface area (ESA) using the formula ESA=(Integrated charge)/(scan rate*0.386 mC/cm-2). A comparative analysis with similar nanostructured Au samples (Table 1) revealed that Au+AnGC displayed a four times higher sensitivity and substantially lower detection limits.The impact of chlorides was explored by repeating the chronoamperometric calibration in a PBS+0.1M KCl buffer. Chloride adsorption led to complete catalyst deactivation and eventually to gold loss from both samples. Notably, Au+BareGC displayed higher sensitivity to Cl etching, experiencing a 50% reduction in gold ESA compared to a 30% drop in Au+AnGC.This work has proved that the deposited nanoclusters possess an extremely high density of active sites towards glucose electro-oxidation. In addition, the deposition on highly porous electrodes decreases the poisoning effect of chlorides. These findings show significant promise as a scalable fabrication strategy to glucose sensor development.References in Table 1:[1] https://www.sciencedirect.com/science/article/pii/S001346861400766X#bib0060[2] https://pubs.acs.org/doi/10.1021/jp810235v[3] https://www.sciencedirect.com/science/article/pii/S0925400515007133?via%3Dihub[4] https://www.sciencedirect.com/science/article/pii/S0039914012008971[5] https://pubs.acs.org/doi/10.1021/ac035143t Figure 1

Minimize Surface Change for Corrosion Study Using a Chronopotentiometric Approach Method in SECCM

In the realm of single-channel scanning electrochemical cell microscopy (SECCM), two primary methods are utilized for approaching the micropipette onto the substrate surface, specifically the chronoamperometric and chronopotentiometric methods. The chronoamperometric method is typically employed in corrosion studies utilizing SECCM, although it has been observed that negative approach potentials can influence subsequent microscale electrochemical measurements as a result of cathodic degradation of the metal oxide film. In this study, we investigated the practicality and stability of utilizing the chronopotentiometric approach method in SECCM-based corrosion research, and we found that the metal surface change during the approach process can be reduced by applying a 0 A approach signal, allowing for the acquisition of primitive electrochemical information of the surface.

The Interplay of Anodic Passivation and Oxygen Evolution of Medium Entropy Alloys in Artificial Seawater

Medium entropy alloys (MEA) have gained increased interest in both academic and industrial sectors due to their favorable mechanical and anti-corrosion properties, rendering them ideal candidates for engineering and potentially catalytic applications. Although previous studies have shown high current densities at high anodic potentials for MEAs, a lack of understanding on the underlying transpassive dissolution and local corrosion behavior remains.This project aimed to investigate and compare the passivation behavior of MEAs CrCoNi and FeCrNi (equimolar) under high anodic potentials, focusing on the mechanisms of transpassive dissolution and the oxygen evolution reaction in artificial seawater. The study utilized various techniques such as scanning electrochemical microscopy (SECM) to instantaneously detect evolving metal species and oxygen, and inductively coupled plasma mass spectrocmetry (ICP-MS) to quantify the dissolved metal species. For these investigations, the alloys were subjected to precisely controlled corrosion loads employing potentiodynamic, potentiostatic, and chronoamperometric methods during the SECM experiments and subsequent ICP-MS analysis.Macroscopic corrosion and passive film properties were studied via potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and X-Ray Photoelectron Spectroscopy (XPS). Finally, in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM) were used to analyze the corrosion morphology and surface potentials before, during, and after passivity breakdown. Overall, this study aimed to provide a comprehensive understanding of the interplay between passivation, anodic dissolution and oxygen evolution of the MEAs in artificial seawater.

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.

Ruthenium nanoparticles embedded poly(4-aminodiphenylamine) nanocomposites based determination of guaifenesin in real samples

An efficient sensing surface is fabricated through incorporating ruthenium on electropolymerized poly-(4-aminodiphenylamine)(Padpa) film by potentiodynamic cycling of 4-aminodiphenylamine (4-adpa) in an acidic medium. The mechanism of electropolymerization comprises the conversion of protonated monomer to di-imine species and generates positively charged radical-intermediate via dimerization step. The surface morphology of deposited film on electrode surface is studied using SEM and XPS techniques. The electrocatalytic appraisal of constructed (Ru/Padpa/GCE) sensing interface is examined towards the electro-oxidation of guaifenesin (GUA) by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronoamperometric (CA) methods. The Ru/Padpa/GCE sensing interface displayed a linear response of GUA from 1.5 to 45 µg/mL with the limit of detection (LOD) of 48.8 ng/mL (S/N = 3). The obtained higher activity of Ru/Padpa/GCE is mainly attributed to its larger active surface area, faster electron transfer kinetics, and higher catalytic sites from the interface. The Ru/Padpa/GCE sensing interface is further applied for the determination of GUA in pharmaceutical (cough syrup, and human urine) samples with a recovery of 97.1–101.0 %. The diffusion coefficient of GUA (1.51 × 10-6 cm2/s) is also obtained via theoretical electrochemical method, which ensures that Ru/Padpa/GCE sensing interface can be considered as a potential candidate for clinical diagnostic analysis.

Electrochemical Studies on Interaction of Ofloxacin with ITO-PANI Supported Bilayer Lipid Membrane

Bilayer phospholipid membrane was formed on the ITO-Pani surface in NaCl bath solution at different pH. Characterization and interaction of bilayer lipid membrane (BLM) with Ofloxacin molecules in 0.1 M NaCl solution was studied at different pH employing electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometric methods. The changes in the properties of BLM due to addition of Ofloxacin depends on the pH of bath solution. At low pH the membrane surface is positively charged and the interaction of drug molecules with the BLM surface takes place through chloride bridge. At alkaline pH the membrane surface is negatively charged and the drug molecules get attached through hydrogen bonding. The results of electrochemical impedance spectroscopy, cyclic voltammetry and chronoamperometry support each other.

Electrochemical deposition of gelatin particles on electrode ITO thin films

In this paper, an electrochemical study of Gelatin was carried out on the glass semiconductor ITO electrode in different media: acidic medium (sulfuric acid) and basic medium (sodium hydroxide solution), using chronoamperometric and cyclic voltammetry methods in order to obtain an electrochemical response of a substance Gelatine. In order to study the structural and optical properties of the film, we used several techniques, including the DRX technology and the Scanning Electron Microscopy (SEM).

Investigation of Hexylamine Adsorption on Gold in Perchloric Acid

The adsorption of hexylamine at the solution–gold interface in 1 M HClO4 in the presence of 0.1 M Fe2+ and 0.1 Fe3+ was studied by potentiodynamic, chronoamperometric and EIS methods. The main kinetic characteristics of the oxidation-reduction reaction iron ions (exchange current density, transfer coefficient, diffusion coefficients of iron ions) were determined. It was shown that the physical adsorption of hexylamine on gold can be described by the Dhar–Flory–Huggins isotherm. The values of the adsorption constant and the Gibbs free adsorption energy were obtained. A comparison of the free adsorption energy at these interfaces with the interaction energies of hexylamine and water molecules, and hexylamine molecules with each other was carried out. It was shown that hexylamine adsorption at all of these interfaces is due mainly to the hydrophobic effect of the interaction of hexylamine and water molecules.

A Tribological Investigation of the Titanium Oxide and Calcium Phosphate Coating Electrochemical Deposited on Titanium

Titanium (Ti) and its alloys are widely used in biomedical applications due to their excellent mechanical properties and biocompatibility. However, they are a concern due to the possibility of cytotoxic effects coming from the degradation products. This degradation occurs by the combined action of corrosion and mechanical wear of these materials, which are released in the biological environment by the biomaterial implanted. The present article aims to investigate a new route to improve electrochemical and tribological performance with surface modification. Regarding the deposition of a protective layer on the surface, it consists of titanium oxide (TiO2) and calcium phosphate (CaP). Both coatings were performed by chronoamperometric methods with titanium oxidation at 1 V and calcium phosphate reduction at −1.5 V. The corrosion and tribocorrosion tests demonstrated the effective combination of TiO2 and CaP layer to protect the Ti substrate. Furthermore, this coating combination reduced corrosion degradation and mechanical wear in PBS, simulating a physiological environment. Additionally, it was observed that this combination of coating decreased the dissipated energy, and consequently, the wear decreased during sliding tests. All these findings indicate the protective behavior of the TiO2 and CaP layer during the tribocorrosion tests.

Facile synthesis of Co/Ni bimetallic phosphate as electrode material for urea fuel cells: Effect of synthetic strategy on the physicochemical and electrocatalytic behavior

Novel bimetallic Co/Ni phosphates were introduced in this work by two different synthetic strategies; reflux (CoNiP-R) and sol–gel (CoNiP-S) methods and evaluated as cheap electrodes for electrooxidation of urea (UEO) in alkaline medium (KOH medium). The as-prepared CoNiP-R and CoNiP-S materials were studied in terms of different physicochemical tools including Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), transmission Electron Microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and Brunauer, Emmett and Teller (BET) surface area to understand what the effect of the synthetic method on the morphology, crystallinity, and surface area is. These investigations indicate the successful synthesis of smaller particles with higher surface area by sol–gel methodology if compared with the reflux method. The performance of CoNiP-R and CoNiP-S as electrode materials for UEO was evaluated through cyclic voltammetry (CV) at diverse urea contents and various sweep rates in addition to electrochemical impedance spectroscopy (EIS) and chronoamperometric (CA) methods. The synthesized CoNiP-S showed an enhanced UEO if compared with CoNiP-R at various urea doses up to 1.0 mol/l. Besides, the improvement of the obtained charge transfer resistance and current density indicates the increase of electrons generated from UEO.

Immuno-battery: A single use self-powered immunosensor for REASSURED diagnostics

In this work, we present a novel self-powered approach totally independent from any external energy source. We have developed a self-powered paper-based immunosensor that generates energy in the presence of the biomarker in the sample. In particular, the device – which has been labeled as Immuno-Battery – makes use of magnesium as anode and the widely employed HRP-labeled antibody as cathodic catalyst to detect C-reactive protein (CRP) presence in artificial samples. Feasibility of self-powered sensing is proved by submitting the immuno-battery to a resistive load. In this regime, the sensor provides operation voltages above 1.55 V and maximum power densities from 40 to 571 μW cm−2 that allow for future implementation of an electronic readout circuit. We have demonstrated that sensitivity of the system is not compromised by the self-powered mode operation, as the LOD value delivered by our battery (20 ± 2 ng mL−1) is compliant with LOD values reported for protein detection in paper-based electrochemical immunoassays with chronoamperometric methods. Moreover, as a case study, a LOD of 269 ± 39 ng mL−1 is obtained for CRP detection, in accordance with available commercial high-sensitivity CRP detection kits. This proof-of-concept opens the path towards the development of digital diagnostic devices in a sustainable and affordable manner.

Graphene Oxide Decorated Tin Sulphide Quantum Dots for Electrochemical Detection of Dopamine and Tyrosine

The current study highlights the design and construction of a sensitive and selective sensor for detection of dopamine and tyrosine using a GO-SnS2 quantum dots by a drop casting method on glassy carbon electrode. Highly porous nano-crystalline GO-SnS2 quantum dots were synthesized by using ultrasonication followed by hydrothermal method in a facile manner. XRD, SEM, XPS, TEM, and pore size distribution techniques were used to characterize the quantum dots that were produced. The newly fabricated electrode was evaluated for EIS (Electrochemical impedance spectroscopy), CV (cyclic voltammetry) and chronoamperometric methods. The observed limit of detection of dopamine was observed to be 26 nM. High selectivity and sensitivity were observed for electrochemical detection of dopamine and tyrosine.

(Digital Presentation) Investigation of the Hexylamine Adsorption on Platinum By Potentiostatic and Potentiodynamic Methods

Adsorption is one of the electrochemical process stages often. The adsorption of polar organic molecules (surfactants) on metal electrodes is of significant interest. In particular, the surfactant adsorption affects the exchange current value and determines the metal corrosion rate. Therefore, the explanation of the adsorption mechanism is the most important problem in the investigation of the electrochemical kinetics.The kinetics of the Fe2+ and Fe3+ oxidation-reduction reaction on a platinum electrode in 1 M HClO4 was investigated by potentiodynamic and chronoamperometric methods in the presence of hexylamine as a surfactant. The main kinetic characteristics of the reaction (exchange current density, transfer coefficient, diffusion coefficients of iron ions) have been determined.The dependence of the exchange current density on the hexylamine concentration is analyzed. The surface coverage with a surfactant was estimated at various hexylamine concentrations. It was shown that the hexylamine adsorption on platinum is described by the Dhar-Flory-Huggins adsorption isotherm. The values of the adsorption constant and the adsorption free energy are obtained. These values are close to the corresponding values for the hexylamine adsorption on mild steel in hydrochloric acid. Consequently, the objective laws for the hexylamine adsorption depend low on the acid type and the electrode nature. This indicates the physical adsorption of the surfactant.It is possible that adsorption occurs due to the hydrophobic interaction of the surfactant molecules with polar water molecules. Then, the displacement of surfactant molecules to the interface takes place regardless of the nature of the acid and the metal contacting with the solution. The latter assumption requires further investigations of the surfactant adsorption on various metals.

MXene-based composite electrodes for efficient electrochemical sensing of glucose by non-enzymatic method

A recently discovered 2D transition titanium metal carbides also called as MXenes (Ti3C2Tx)-based nanocomposite was prepared with Cu2O through wet precipitation technique, and these materials were further developed as the electrode for sensing glucose by chronoamperometry technique. The prepared MXene-Cu2O (Ti3C2Tx-Cu2O) nanocomposite was characterized by XRD, FTIR, UV–Vis spectroscopy, FE-SEM, EDAX, and Raman spectroscopy. Morphological studies of the composites revealed that the micro-octahedral shape of Cu2O is distributed on the surface of MXene with size larger than bare Cu2O. Further, the prepared composite material was fabricated as a sensing probe, and the electrochemical activities were examined by cyclic voltammetric analysis (CV) and chronoamperometric (CA) methods. From the CV and CA investigation, the current response was higher for the composite than the bare material (Cu2O & MXene) in the presence of glucose. The amperometric investigation of MXene-Cu2O composite for the detection of glucose shows a broad linear range (0.01–30 mM) with a sensitivity of 11.061/μAmM cm−2 and a detection limit of 2.83 μM. Further, the fabricated sensor exhibits good selectivity with interfering species like NaCl, fructose, sucrose, urea, ascorbic acid, lactose, short response time, stability, good reproducibility, and compatibility with human serum sample. From the investigation, the prepared MXene-Cu2O composite is a good candidate for the direct detection of glucose molecules and is also well suitable for clinical diagnosis.

Selective electro-oxidation of dopamine on Co or Fe supported onto N-doped ketjenblack

Herein, we report the synthesis of Co and Fe supported onto N-doped ketjenblack (Co/KB-N and Fe/KB-N) electrocatalysts via a template-free synthesis method, using EDTA nitrogen precursor and oxidized carbon, and their examination for dopamine electrooxidation reaction. The as-fabricated electrocatalysts initially were physicochemically characterized using the transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS) and carbon, hydrogen, nitrogen, sulfur (CHNS), techniques. Afterwards, they were electrochemically evaluated using cyclic voltammetry, chronoamperometric and potentiometric methods. Both electrocatalysts were examined in alkaline environment (pH=13). Co/KB-N was also tested at a pH value close to human's serum (pH=7.25), exhibiting much higher performance in terms of activity, sensitivity, stability and selectivity. The lower pH values favored the dopamine electrooxidation reaction, specifically increasing the Co/KB-N current response from ca. 7 to 50 μA and its sensitivity at high concentration range from 571.3 to 1185.7 μA mM−1 cm−2. This performance improvement could be attributed to the fact that the neutral environment favors the formation of the Co3+/Co4+ redox pair, which is not presented in the alkaline medium, and, in combination with the presence of N, is responsible for the high rate of electron transfer as well as the Co/KB-N high selectivity.

Fabrication of Electrochemical Sensor for Epinine Determination Amplified with MgO/CNTs Nanocomposite and Ionic Liquid

Background:Catecholamines are a large group of pharmacological and biological compounds that are widely used in biological systems. These compounds are prepared both naturally and synthetically with many key roles in the human body and its activities. Therefore, many researchers focused on the identification and determination of catecholamines in biological samples.Methods:MgO/SWCNTs were synthesized through the chemical precipitation method. In addition, cyclic voltammetry, differential pulse voltammetry, and chronoamperometric methods were used for the electro-oxidation reaction study of epinine at the surface of the modified electrode.Results:Carbon paste electrode (CPE) modified with MgO/SWCNTs nanocomposite and 1-butyl- 3-methylimidazolium methanesulfonate (BMMS) was used as an electrochemical sensor for the determination of epinine. The results showed a linear dynamic range of 5.0 nM-250 μM with a detection limit of 0.1 nM for epinine determination using MgO/SWCNTs/BMMS/CPE as a sensor.Conclusion:In the present study, a highly sensitive electrochemical sensor was designed and fabricated as an analytical tool for the determination of epinine. MgO/SWCNTs/BMMS/CPE was successfully used for the determination of epinine in water and dextrose saline with an acceptable recovery range of 98.7%-102.72%.

Nonenzymatic Electrochemical Sensor Based on CuO-MgO Composite for Dopamine Detection

Dopamine plays an essential role in the proper functioning of the brain and the body. A change in the level of dopamine can lead to disorders related to the nervous system. Thus, detection of dopamine levels may aid in the diagnosis and treatment of various diseases. Enzymatic electrochemical sensors have been extensively studied for the detection of dopamine because they exhibit excellent selectivity and reliability. However, enzymatic electrochemical sensors suffer from several unavoidable drawbacks such as complex enzyme purification process, weak enzyme immobilization on the electrode, enzyme denaturation and low stability. On the other hand, non-enzymatic sensors are promising alternatives that offer high sensitivity, high electrocatalytic activity, long term stability and eliminate the problems associated with enzymes. Herein, we present a non-enzymatic nanocomposite (NC) of metal oxides (CuO-MgO) for efficient electrochemical detection of dopamine. Scalable sol-gel method is adopted for the controlled growth of CuO-MgO NC. The structural, elemental and morphological analysis is performed by XRD, Raman spectroscopy, and TEM characterization, respectively. The electrochemical analysis was carried out to study the electrocatalytic behavior of CuO-MgO in the detection of dopamine, by cyclic voltammetry and chronoamperometric methods. The electrocatalytic behavior was investigated at different scan rates and for different dopamine concentrations in artificial sweat solution. The CuO-MgO NC catalyst exhibited a sensitivity of <inline-formula> <tex-math notation="LaTeX">$69~\mu $ </tex-math></inline-formula>Acm^&#x2212;2mM^&#x2212;1 and the detection limit is computed to be <inline-formula> <tex-math notation="LaTeX">$6.4~\mu \text{M}$ </tex-math></inline-formula> in the linear range of 10-<inline-formula> <tex-math notation="LaTeX">$100~\mu \text{M}$ </tex-math></inline-formula>. Moreover, the NC apprehended a high degree of selectivity towards other bio-compounds present in the sweat, and no possible interfering cross-reaction from these species was observed. The as-synthesized CuO-MgO NC offered high sensitivity, selectivity, fast response and stability, which benchmarked its potential for dopamine sensing.

CATCH (Cortisol Apta WATCH): ‘Bio-mimic alarm’ to track Anxiety, Stress, Immunity in human sweat

This work demonstrates an electrochemical label-free cortisol aptasensor (Cortisol Apta-Watch (CATCH) for detection of cortisol from passively perspired eccrine sweat. The platform is designed to track cortisol levels in sweat to understand the implications of stress in different physiological processes of the body. The sensor platform is characterized with zeta potential, FTIR, and electrochemical measurements to understand the aptamer binding chemistry and cortisol binding sensitivity. Following this, the platform's sensitivity to cortisol analyte concentration in human sweat is evaluated using impedimetric and chronoamperometric methods. The results highlight the platform's sensitivity to cortisol with a detection limit of ~1 ng/mL in human sweat and a dynamic range of 1–256 ng/mL. The performance metrics highlight the ability of the sensor to sensitively detect cortisol in human sweat with high significance (p<0.05). These studies are demonstrated across triplicate measurements and have low RSD values (˷<2%). The performance was also evaluated on five healthy subjects, indicating the ability to detect sweat cortisol in real time and on-body. Additionally, the developed sensing platform demonstrated excellent correlation with state-of-art reference method with a Pearson's correlation of r = 0.97 in nine human subject samples. The sensor also demonstrated that the circadian behavior of cortisol can be tracked with elevated levels in the morning and low levels in the evening in a cohort of healthy subjects. The developed aptamer-based cortisol sensing technology can aid in real-time, continuous monitoring facilitating personalized health monitoring.

Nanomolar detection of mercury(II) using electropolymerized phthalocyanine film

The synthesis and characterization of novel cobalt(II) tetraamide benzimidazole phthalocyanine (CoTABImPc) has been reported for the first time and applied for the determination of mercury(II) at nanomolar concentration using electrochemical techniques. CoTABImPc was prepared by coupling 4-(1H-benzimidazol-2-yl)aniline with cobalt(II) tetracarboxylic acid phthalocyanine. CoTABImPc was characterized by elemental analysis, TGA, FT-IR, UV–visible, Mass, and NMR spectroscopic techniques. The CoTABImPc was electropolymerized on clean glassy carbon electrode (GCE) by continuous cycling of the potential (GCE/poly(CoTABImPc)). The polymeric film was employed for the detection of highly toxic Hg(II) by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometric (CA) methods. The designed GCE/poly(CoTABImPc) electrode exhibited good electrochemical response and high electrocatalytic activity for detecting Hg(II). The Pc polymeric film electrode displayed a sensitivity of 1.2178 µA nM−1 cm−2 for the detection of Hg(II) in the linear range 10–300 nM, and low detection limit of 4 nM using CV technique. Further, DPV exhibited a sensitivity of 1.4024 µA nM−1 cm−2 in the 10–500 nM range with LOD of 3.8 nM. The CA method delivered an excellent sensitivity of 3.7389 µA nM−1 cm−2 in the linear range 10–400 nM with LOD of 3 nM. The proposed method augments the selective electrochemical determination of Hg(II) in environment pollution analysis.

Bronze Electroplating: Stability, Nucleation and Growth Study of a New Green Formulation

Bronze electroplating is a widely used process in the electronics and costume jewelry industrial sectors as an anti-corrosion coating and barrier layer against intermetallic diffusion. The study of this alloy is also essential for the realization of copper-zinc-tin sulfide (CZTS) compounds, a quaternary semiconductor with a growing interest for the realization of thin film photovoltaic devices. The galvanic baths currently on the market are alkaline with a high amount of sodium or potassium cyanide to complex the metal ions. Cyanide salts are extremely dangerous for their toxicity, blocking cellular respiration. For this reason, cyanides are considered a danger both for the environment as well as for the workers with whom it comes in contact. In this study, a new eco-friendly, acidic and cyanide-free formulation was developed for the deposition of the Cu-Sn alloy.To achieve this goal, methanesulfonic acid (MSA) was chosen as electrolyte, which is biodegradable as part of the natural sulfur cycle. Various recipes have been evaluated to obtain a solution that was stable over time and that did not lead to the precipitation or oxidation of its components. Copper sulphate, copper methanesulfonate and tin methanesulfonate solutions were used as precursors of the metals [1]. As stabilizing additives nitrilotriacetic acid (NTA) and 2-picolinic acid (2PA), complex agents for copper, and hydroquinone (HYD), antioxidant agent for tin, were evaluated. The composition of the films, obtained both by potentiostatic and galvanostatic deposition, were analyzed by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) and, to investigate the structural phases of the deposits, XRD measurements were carried out. Finally, nucleation and growth as a function of the concentration of thiourea (TU) and potassium and sodium tartrate (PST), regulating additives for the deposition of copper and tin, respectively, were studied by chronoamperometric methods, in order to achieve progressive growth and therefore a lucid deposit. The present study funded by the PRIN Project (“Progetti di Ricerca di Rilevante Interesse Nazionale”), “Novel Multilayered and Micro-Machined Electrode Nano-Architectures for Electrocatalytic Applications (Fuel Cells and Electrolyzers)”, grant number 2017YH9MRK.