Zeinab Pourghobadi

In this work, the glassy carbon electrode was modified by multi-walled carbon nanotubes, β-cyclodextrin, reduced graphene oxide, and gold nanoparticle nanocomposites GC/MWCNTs/β-CD-rGO@Au). The GC/MWCNTs/β-CD-rGO@Au electrode was utilized for simultaneous monitoring of catechol (CC) and hydroquinone (HQ). The modified electrode has a clear pair of voltammetric peaks for CC and HQ, which makes it an appropriate tool for the simultaneous determination of the two isomers. Under optimized conditions, the oxidation peak currents of CC and HQ at GC/MWCNTs/β-CD-rGO@Au were increased linearly in the 1–173 μM and 2–80 μM concentration range with the limit of detection (LOD) (based on S/N = 3) of 0.17 μM and 0.26 μM. The GC/MWCNTs/β-CD-rGO@Au exhibits adequate stability, repeatability, and recovery in analyzing two dihydroxybenzenes isomers.

In the world of medicine, the discovery of acyclovir, an antiviral medication often used to treat herpes infections, is very important. Accurate and sensitive detection are essential for patient safety since acyclovir is recognized for its possible adverse effects and toxicity at high dosages. A Cu metal-organic framework (MOF) doping with Fe₃O₄/SiO₂ was prepared by direct Co-precipitation method. This binary Fe₃O₄-SiO₂/Cu-MOF was analysis by scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD), and this MOF was used to modify the glassy carbon electrode (GCE) surface. Modified GCE was used for the electrochemical monitoring of Acyclovir in the plasma samples. Acyclovir’s electro-oxidation behavior was assessed using cyclic and differential pulse voltammetric techniques. A redox mechanism was postulated based on the effect of the potential scanning rate and solution pH on the voltammetric response of Acyclovir oxidation. A 0.03 μM limit of detection was acquired for Acyclovir analysis with a linear response in the range of 1–60 μM. Finally, acyclovir quantification in the blood serum samples was successfully performed.

We developed an electrochemical sensor by combination of Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) then decorated with Au-nanoparticles (AuNPs) by an electrodeposition process for detection of dopamine (DP) in the presence of acetaminophen (AC). The electrochemical properties of MWCNT/GO- AuNPs/GCE were characterized by scanning electron microscopy (SEM) and cyclic voltammetry (CV).The results displayed that Au nanoparticles were well jointed onto MWCNT/GO nanocomposite. The electrochemical responses displayed the prepared sensor showed enhanced electrocatalytic activity for the detection of DP inthe presence of acetaminophen (AC). Under optimum conditions, the proposed sensorpresented a linear response based on the DP concentration in the range of 1.0 to 165 μ M with a detection limit of 0.07 μ M using the differential pulse voltammogram (DPV) method.Moreover, this proposed sensor displayed a linear range concentration of AC ranging from 3 to 200.0 μ M and detection limit of 0.061 μ M. Also, the prepared sensor indicated excellent sensitivity and selectivity for the DP determination in the presence of AC in real samples.

In this research work, a straightforward strategy for the development of carbon-based electrodes is presented using nanoclay as a modifier, and a room temperature ionic liquid was employed as a binder for the simultaneous determination of dopamine (DP) and uric acid (UA) in the presence of ascorbic acid (AA) in real samples in the form of serum and urine. The synergistic effect between nanoclay and the ionic liquid results in an increase in the activity of the prepared carbon ionic liquid/nanoclay (NC-CILE) nanocomposites, promoting the electron transfer and electrocatalytic activity. Considerable stability, electrocatalytic properties, and large surface area make it possible to exploit low detection limit sensors for long term applications in real samples and wide linear dynamic ranges. The electrochemical behavior of the prepared NC‑CILE electrode was diagnostically studied by cyclic voltammetry and differential pulse voltammetry analyses. The response currents were linear in the DP and UA concentration ranges of 1.0–100.0 and 0.1–10.0 μM, respectively. In addition, at 50.0 µM of AA, the detection limits for DP and UA were estimated to be around 0.45 and 0.025 μM (S/N = 3), respectively.

Paraquat is one of the most toxic materials widely applied in agriculture in most countries. In the present study, a simple, innovative and inexpensive nano biosensor which is based on a thioglycolic acid (TGA) - CdTe@CdS core-shell nanocrystals (NCs) to detect paraquat, is suggested. The NCs based biosensor shows a linear working range of 10–100 nM, and limited detection of 3.5 nM. The proposed sensor that has been well used for the detection and determination of paraquat in natural water samples is collected from corn field and a canal located near to the corn field yielding recoveries as high as 98%. According to our findings, the developed biosensor shows reproducibility and high sensitivity to determine paraquat in natural water samples in which the amount of paraquat has low levels. The suggested method is efficiently applied to paraquat determination in the samples of natural water that are collected from a tap water and a canal located near to the cornfield.

In the present research, 4, 4'-biphenol was used as a homogeneous mediator for determining cysteine (CySH) on a Glassy Carbon Electrode (GCE). To describe the electrochemical properties of 4,4'-biphenol and to examine its electrocatalytic impacts on cysteine oxidation, both Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) were employed. Our findings revealed that 4,4'-biphenol could significantly accelerate the reactions related to electron transfer to CySH. Moreover, the diffusion coefficient of CySH and its reaction with the catalytic constant of 4,4'-diphenoquinone was estimated via chronoamperometry technique.The results showed that cysteine concentration range of 10-1000 μM led to linear increases in the oxidation peaks, thus to providing a detection of 0.99 μM with R² = 0.993. A Relative Standard Deviation (RSD) of 2.5% was achieved after performing 7 cysteine replicates (100 μM), and CySH was successfully determined in real serum samples through the proposed approach.

In the present research, a glassy carbon electrode (GCE) was activated aided by an electrochemical process in a 0.5 molar sodium hydroxide solution and then modified by nickel oxide (NiO) nanoparticles and multiwall carbon nanotubes (MWCNT) to obtain NiO/MWCNT/OGCE electrode. This electrode was morphologically and structurally characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Cyclic voltammetric and chronoamperometry methods were employed to investigate the catalytic properties of the modified electrodes for Alfu electro-oxidation in buffer solution. The modified electrode exhibited promising electrocatalytic properties toward the oxidation of Alfuzosin (Alfu).The electrocatalytic role of NiO in Alfu electro-oxidation process was clearly demonstrated in comparison to the OGCE/MWCNT electrode. The reason behind this electrocatalytic activity relays on a synergistic effect involving both NiO and MWCNT. Differential pulse voltammetry (DPV) was employed as a sensitive procedure for the quantitative determination of Alfu. It was found that the oxidation current is in direct relationship with the concentration of Alfu in the 0.01–2.0μM and 2.0–90μM concentration ranges, with 0.0006 μM detection limits. Moreover, no significant response was observed in the presence of the common interference, demonstrating the good selectivity of Alfu. The method was successfully used for the determination of Alfu content in real samples.