Analytical & Bioanalytical Electrochemistry
Volume:15 Issue: 9, Sep 2023

In this study, electrochemical green synthesis, characterization, and application of Carbon dot-doped TiO2 nanocomposites (TiO2@CDs) as carbon paste electrode modifiers have been carried out. The preparation of nanocomposites begins with the synthesis of carbon dots (CDs) by varying the value of the oxidation potential. The obtained CDs were incorporated on the surface of TiO2 through continuous stirring at room temperature followed by heating at a constant temperature of 140oC for 4 hours. To determine the effect of potential variations of CDs on the characteristics of nanocomposites, we used SEM, XRD, and FTIR. Based on SEM characterization, potential variations of CDs didn’t affect or change the surface morphology of TiO2. TiO2 has a characteristic surface morphology which is composed of spherical particles of uniform size. However, XRD and FTIR characterization showed that the potential variation of CDs caused a 2θ angle shift and TiO2 wavenumber in the fingerprint region. Potential variations of CDs caused the average particle size of TiO2 to increase from 37.32 nm to 42.89 nm, 45.12 nm, and 49.01 nm for oxidation potentials of 10 V, 15, and 20 V, respectively. The results of the electrochemical characteristics showed superior performance of CPE in the Fe(CN)63-/Fe(CN)64- solution system after being modified with TiO2@CDs. Superior performance is demonstrated by significantly increased peak currents, both oxidizing and reducing. This phenomenon is strongly influenced by the size of the synthesized CDs particles through potential variations. Based on these results, a potential of 15 V is stated as the best potential in the application of CDs as a modifier.

In this research, the electrochemical performance of carbon paste electrode modified with 4-(3,5-dimethyl-1,4,7,8-tetrahydrodipyrazolo[3,4-b: 4', 3'-e] pyridin-4-yl)benzene-1, 3-diol (DBC) and zirconium dioxide nanoparticles (ZrO2) are investigated for the electrocatalytic oxidation of β-nicotinamide adenine dinucleotide (NADH). The kinetic parameters, transfer coefficient (α), and apparent charge transfer rate constant (ks) were obtained 0.31 and 4.83 s-1, respectively by the cyclic voltammetry (CV) technique. The anodic peak potential of the DBC modifier depends on pH and has a linear range with a slope of 0.047 V/pH. Also, the performance of the modified electrode in the electrocatalytic oxidation of NADH is investigated. It was observed that in the presence of the modifier, the overvoltage related to the oxidation of NADH decreases significantly and its oxidation potential decreases by about 300 mV. Also, the diffusion coefficient (D) between the species and the electrode surface was calculated (D=1.93×10-6 cm2 s-1) using the chronoamperometric method. Using the differential pulse voltammetry method (DPV), the detection limit of 5.8 nM was acquired. Two linear concentration ranges of 0.01-1.0 µM and 1.0-350.0 µM for NADH were obtained. The modified electrode was used to quantitatively analyze NADH in the blood serum sample. Also, this electrode can be acceptably utilized for the simultaneous measurement of NADH and ascorbic acid species.

The effects of 1.0 M hydrochloric acid (HCl) and 0.5 M sulphuric acid (H2SO4) were evaluated for a new pyran derivative known as (E)-4-hydroxy-3-(3-hydroxy-4-methoxyphenyl)acryloyl)-6-methyl-2H-pyran-2-one (HMAP) on corrosion of MS. To evaluate the efficacy of HMAP, various techniques including weight loss measurements, potentiodynamic polarization measurement (PP), electrochemical impedance spectroscopy (EIS), and theoretical approaches [density functional theory (DFT) and Molecular Dynamic simulations (MDS)] were utilized. The maximum inhibitory efficiency was determined to be 89.3% in 1M HCl and 94.6% in 0.5M H2SO4 at 298 K in the existence of 1 mM HMAP. Langmuir isotherm fitted well adsorption process. Plotting Nyquist and Bode graphs in EIS allowed to determine CPE parameters by fitting resulting data. According to the polarization parameters, HMAP is a mixed-type inhibitor in both media, with a cathodic preponderance in the sulfuric medium. The results of the EIS investigation indicate that these compounds stop corrosion through an adsorption mechanism. Findings from experiments and theory were shown to be closely connected.

A Ce3+ all-solid-state ion selective electrode (ASS-ISE) was developed and applied in the analysis of this ion in samples with complex matrices. The electrode includes conductive multi-walled carbon nanotubes (MWCNTs) -epoxy resin substrate on a copper wire, which was later coated with a Ce3+-selective PVC membrane film, optimally composed of 25% wt. of PVC, 65% wt. of nitrobenzene (NB), 2% wt. of sodium tetraphenyl borate (NaTPB)), and 8% wt. of N’-[(2-hydroxyphenyl)methylidene]-2-furohydrazide (L) as a Ce3+-selective ion carrier. The optimal ASS-ISE showed a Nernstian behavior with a calibration curve slope of 19.3±0.4 mV/decade in the concentration window of 1.0×10-7 M to 1.0×10-4 M, and its limit of detection (LOD) reached 5.0×10-8 M. The electrode had outstanding selectivity for the target ion in the presence of varied commonly occurring interfering ions and could be satisfactorily used in the determination of cerium ion concentration in wastewater samples.

One of the important molecules in homeostasis, especially for hormone metabolism, cellular membrane production, and vitamin D synthesis is cholesterol. However, studies showed that increased levels of this molecule would be associated with increased incidence of cardiovascular diseases including heart failure and myocardial infarction (MI). Thus, the measurement of the blood level of cholesterol is an important step for early detection and prevention of several diseases. Electrochemical sensors with high accuracy could be useful for the detection of cholesterol in body fluids. Due to the outstanding chemical and physical properties that nanoparticles possess, they are perfectly suited for the development of new and improved sensing devices. In particular, electrochemical sensors and biosensors are two types of sensing devices that could benefit from the use of nanoparticles. Many different kinds of nanoparticles, such as metal nanoparticles, oxide nanoparticles, semiconductor nanoparticles, and even composite nanoparticles, have found widespread application in electrochemical sensors and biosensors, respectively. This review has covered a variety of electrochemical biosensors for cholesterol detection, including conductometric, amperometric, and potentiometric-based biosensors, as well as their detection techniques and limitations.

Wearable Potentiometric Ion Sensors (WPISs) have emerged as a highly promising analytical tool that amalgamates advancements in chemistry, materials science, and electronics to provide essential physiological insights during various human activities. The remarkable capability of seamlessly integrating these analytical devices into everyday wearables, such as sweatbands, patches, and garments, without causing any discomfort to the wearer, has transformed WPISs into indispensable tools for both monitoring health parameters and enhancing athletic performance. Recent research has demonstrated a significant role for WPISs in tracking critical biomarkers, including sodium, potassium, calcium, magnesium, ammonium, and chloride, which are present in relatively high concentrations in sweat. The utilization of these innovative devices empowers us to continuously monitor patients' well-being and optimize athletes' performance. In this comprehensive review, we delve into a plethora of studies concerning wearable sensors designed for sodium detection and explore the latest materials utilized in the development of sodium-sensing wearables.