Pd Doped Ag@C Core-Shell Nanocomposite for Electrochemical Sensitive Determination of Bisphenol A

In this work, core–shell structured nanocomposites consisting of Pd doped Ag@C were synthesized by impregnation–reduction method. Then, sensing electrodes were fabricated by modifying Pd/Ag@C core-shell nanoparticles on screen-printed electrodes (SPE) for electrochemical determination of bisphenol A (BPA). The composition and morphology of nanocomposites were characterized by scanning electron microscopy, transmission electron microscopy, X ray diffraction and energy-dispersive X-ray spectroscopy. The electrochemical response characteristics of nanocomposites to BPA was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results indicated that, compared with Ag@C and Pd/C, Pd/Ag@C nanocomposite shows greater catalytic activity to the oxidation of BPA due to the synergistic effect of Pd and Ag. Among the four synthesized Pd/Ag@C-x (x=1-4) nanomaterials, the Pd/Ag@C-3 exhibits the best sensing performance toward the sensitive detection of BPA. The linear range for BPA determination was from 8.0×10-8 M to 1.5×10-5M with a detection limit of 1.0×10-8 M. A less than 9% oxidation peak current change was observed on the determination of BPA using Pd/Ag@C-3/SPE when added different interfering species into the BPA solution. The oxidation peak current attenuation of BPA on Pd/Ag@C-3/SPE within five weeks was found to be less than 3.6%.

Square-Wave Voltammetric Sensing of Lawsone (2- Hydroxy-1,4-Naphthoquinone) Based on the Enhancement Effect of Cationic Surfactant on Anodically Pretreated Boron-Doped Diamond Electrode

In this reported work, an anodically pretreated boron-doped diamond (BDD) electrode was used for the inexpensive, simple and quick detection of a natural dye, lawsone. Lawsone had a well-defined, irreversible and diffusion-controlled oxidation peak at approximately +0.19 V in phosphate buffer solution (PBS, 0.1 M, pH 2.5) using cyclic voltammetry (CV). The oxidation peak heights of lawsone were significantly increased in PBS using the cationic surfactant cetyltrimethylammonium bromide (CTAB). Under optimized experimental conditions, the calibration curve was linear over a concentration range of 0.1–5.0 μM with detection limit of 0.029 μM in 0.1 M PBS (pH 2.5) containing 0.1 mM CTAB by using square-wave voltammetry (SWV). To evaluate the practical applicability of the BDD electrode, it was used for the quantification of lawsone in commercial henna, a natural dye made from the leaves of the henna plant.

Poly (Orange CD) sensor for paracetamol in presence of folic acid and dopamine

In the present work, Orange CD was chosen as an intriguing modifier for the electropolymerization on the surface of CPE by the CV technique. A novel, sensitive, and cost-effective poly (Orange CD) MCPE (PoOCD/MCPE) sensor was utilized for the selective detection of paracetamol (PA) in 0.2 M phosphate buffer solution (PBS) of pH 7.4. The oxidation peak current of PA was vastly enhanced at the sensor. The scan rate study is suggested that electro-oxidation of PA was adsorption-controlled. The pH study testifies the redox pathways transport with the same quantity of electrons and protons. The detection limit of PA is found to be 2.64 µM. DPV results show that substantial peak separation between PA, folic acid (FA), and dopamine (DA) could be facilitating their individual and simultaneous determination on the sensor. The decorated sensor demonstrates high sensitivity, stability, reproducibility, repeatability and has been successfully exploited for the detection of PA in a tablet with promising results.

Simultaneous Detection of Dopamine and Serotonin with carbon-based electrodes

Graphite-based materials, like pyrolyzed carbon electrodes, are widely used as implantable electrochemical sensors, for the detection of neurotransmitters, neuromodulators, and gaseous species, thanks to their strong mechanical properties, superior electron-transfer kinetics, and in-vivo stability. Electrochemical properties of graphite can be improved by coating them with carbon nanotubes (CNTs) which improves sensitivity, selectivity, and resistance to biofouling. Although several types of electrodes have been developed to detect biologically relevant targets like monoamines, multiplexed sensing of dopamine and serotonin is not yet widely available. Herein we introduce pyrolyzed carbon electrodes coated with CNTs for fast scan cyclic voltammetry for simultaneous detection of dopamine and serotonin with a sensitivity of 52/microM and 5nA/microM, respectively. Serotonin shows a broad oxidation peak at 0.68V. When dopamine and serotonin are probed simultaneously at 10 Hz, dopamine oxidizes at 0.1V 0.1 and serotonin oxidizes at 0.78V and dopamine reduces at -0.35V and serotonin at 0.1V. Thus the sensors shows discrimination between dopamine and serotonin and are suitable for simultaneous detection of these monoamines. Keywords: Carbon nanotubes, Electrochemistry, Dopamine, Serotonin, Anti-fouling Surfaces

One-Step Electrodeposition Synthesized Aunps/Mxene/ERGO for Selectivity Nitrite Sensing

In this paper, a new nanocomposite AuNPs/MXene/ERGO was prepared for sensitive electrochemical detection of nitrite. The nanocomposite was prepared by a facile one-step electrodeposition, HAuCl4, GO and MXene mixed in PBS solution with the applied potential of –1.4 V for 600 s. The modified material was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and cyclic voltammetry (CV). The electrochemical behavior of nitrite at the modified electrode was performed by CV and chronoamperometry. The AuNPs/MXene/ERGO/GCE showed a well-defined oxidation peak for nitrite at +0.83 V (Vs. Ag/AgCl) in 0.1 M phosphate buffer solution (pH 7). The amperometric responses indicated the sensor had linear ranges of 0.5 to 80 μM and 80 to 780 μM with the LOD (0.15 μM and 0.015 μM) and sensitivity (340.14 and 977.89 μA mM–1 cm–2), respectively. Moreover, the fabricated sensor also showed good selectivity, repeatability, and long-term stability with satisfactory recoveries for a real sample. We also propose the work that needs to be done in the future for material improvements in the conclusion.

Electro-oxidation of formoterol fumarate on the surface of novel poly(thiazole yellow-G) layered multi-walled carbon nanotube paste electrode

The current study explicates the electro-oxidation behavior of formoterol fumarate (FLFT) in the presence of uric acid (UA) on the surface of poly thiazole yellow-G (TY-G) layered multi-walled carbon nanotube paste electrode (MWCNTPE). The modified (Poly(TY-G)LMWCNTPE) and unmodified (MWCNTPE) electrode materials were characterized through electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and cyclic voltammetry (CV) approaches. The characterization data confirms the good conducting and electrocatalytic nature with more electrochemical active sites on the Poly(TY-G)LMWCNTPE than MWCNTPE towards the FLFT analysis in the presence of UA. Poly(TY-G)LMWCNTPE easily separates the two drugs (FLFT and UA) even though they both have nearer oxidation peak potential. The electro-catalytic activity of the developed electrode is fast and clear for FLFT electro-oxidation in 0.2 M phosphate buffer (PB) of pH 6.5. The Poly(TY-G)LMWCNTPE offered a well-resolved peak with the highest electro-oxidation peak current at the peak potential of 0.538 V than MWCNTPE. The potential scan rate and oxidation peak growth time studies show the electrode reaction towards FLFT electro-oxidation is continued through a diffusion-controlled step. The variation of concentration of FLFT in the range from 0.2 to 1.5 µM (absence of UA) and 3.0 to 8.0 μM (presence of UA) provides a good linear relationship with increased peak current and a lower limit of detection (LOD) values of 0.0128 µM and 0.0129 µM, respectively. The prepared electrode gives a fine recovery for the detection of FLFT in the medicinal sample with acceptable repeatability, stability, and reproducibility.

Laser Photocatalysis of the Chlorophyll Dye Using the Cyclic Voltammetry Method

Cyclic voltammetry is a widely used technique in electrochemistry due to its simplicity and large amount of data and information that can be obtained. This study utilises this technique to study chlorophyll a and total chlorophyll (Tchl) alongside a laser light to induce photosynthesis. No oxidative peak was observed, regardless of the solution pH in either a dark or light environment when using a solution with an electrolyte of tetrabutylammonium perchlorate (TBAP) in both dichloromethane (DCM) and acetonitrile (MeCN), whereas in a solution of aqueous HCl a small anodic peak was observed. The concentration of the droplet of Tchl pigment on the surface of macro glassy carbon electrode (GCE) was increased, which resulted in a similar trend and the oxidation peak was observed to be slightly larger when in the presence of light. It was observed that the filtered solution of Tchl pigment produced a weaker signal than the unfiltered solution and there were slightly reduced oxidative peak currents when the concentration of VK1 was increased. were no observed changes in the peak charges or currents over a wide potential range (0.0, 0.2, 0.4, 0.6 and 0.8 V) in the presence or absence of light by using coulometry and amperometry methods, therefore, more information on the 3-D formation is required for the photoreduction processes.

Reduced Graphene Oxide Fibre Electrodes for Drug Sensing

Reduced graphene oxide (rGO) fibre electrodes and their ability to sense paracetamol (as model drug) were studied. rGO was electrodeposited onto carbon fibre by two different approaches: potentiostatic deposition and cyclic voltammetry (CV) in the presence of graphene oxide solution. Carbon fibre electrodes coated with rGO (after five CV cycles) could sense paracetamol with an oxidation peak at 0.62 V (vs. Ag/AgCl). The limit of detection of this fibre sensor was found to be 36.3 µM with a linear range of 50–500 µM of paracetamol (R2 = 0.9901).

Voltammetric quantification of an anesthetic drug propofol (2,6-diisopropylphenol) on boron-doped diamond electrode in the pharmaceutical formulations

In this paper, the detailed electrochemistry of propofol (PRO) which is one of the intravenous agents commonly used for sedative-hypnotic purposes was examined. In cyclic voltammetry, the agent showed one irreversible and diffusion?controlled oxidation peak, resulting in the formation of a couple with a reduction and re-oxidation wave at less positive potentials. The effect of electrode pretreatment procedures on the electrochemical response of PRO was investigated by using square wave voltammetry (SWV) and the optimum procedure was used to improve the signal response in subsequent studies. Quantification of PRO was done based on the first oxidation peak using SWV. After optimization of all variables, the linear working range of PRO was found to be between 2.5 ?g mL-1 (1.4?10-5 mol L-1) and 160.0 ?g mL-1 (1.1?10-3 mol L-1, n=15) with a detection limit 0.71 ?g mL-1 (3.9?10-6 mol L-1). No noteworthy interference effect was detected. Also, the developed method was used for quantification of PRO in pharmaceutical sample.

Study of the CuII Affinity by Three Chelating Agents of Biological Interest: TPEN, TRIEN and Et2DTC

Copper is an important micronutrient, and it is present in some protein structures, as well as participate in several important biological processes. Due to its importance, some ligands are used and studied like carriers of copper in the biological systems. This work has investigated the affinity of CuII by three ligands of biological interest: N,N,N,N’-tetrakis (2-pyridilmethyl) ethylenediamine (TPEN), triethylenetetramine (TRIEN), and diethyldithiocarbamate (Et2DTC), used for this purpose. The studies were performed by evaluating the CuII d-d band when complexed with these three ligands. The CuII d-d band in aqueous solution appears around 800 nm; when in the presence of TRIEN, this band displaces to 576 nm. TRIEN ligand is substituted by TPEN ligand (d-d band at 689 nm), and finally, in the presence of the Et2DTC ligand, the d-d band displaces to 665 nm. Theoretical calculations were used to obtain the binding energy and the values obtained were −481.85 kcal mol−1 for the CuII-TPEN, −417.80 kcal mol−1 for CuII-TRIEN and −726.72 kcal mol−1 for CuII-Et2DTC. Electrochemical studies showed an oxidation peak at 0.008 V to CuII-TRIEN complex, −0.135 V to CuII-TPEN and 0.150 V to CuII-Et2DTC. These results showed that CuII has a higher affinity by the Et2DTC ligand compared to the other ligands studied.