A N-[(Benzyloxy)carbonyl]-l-alanyl-l-prolyl-l-leucine-N-cyclohexylcyclohexanamine (Cbz-APL) tripeptide-coated glassy carbon electrode (GCE)-based sensor was used for sensitive and selective recognition of cadmium ions in environmental water. Detailed cyclic voltammetric and electrochemical impedance spectroscopic studies were performed to investigate the charge transfer and sensing activity of the developed electrochemical sensor. Square wave anodic stripping voltammetry (SWASV) was employed to further investigate the sensitivity, selectivity, validity, and applicability of the developed sensor. A sharp electrochemical signal of oxidized Cd at −0.84 V versus Ag/AgCl provides evidence for the higher sensing ability of Cbz-APL/GCE than bare GCE at −0.79 V. Moreover, on Cbz-APL/GCE, extraordinary low detection limits of 4.34 fM and linearity range of 15 nM to 0.1 pM with coefficients of correlation higher than 0.99 for Cd2+ were achieved. Besides, the influence of inorganic and organic interferents on the targeted analyte signals was examined, and high selectivity of Cbz-APL/GCE for Cd2+ ions was observed. Lastly, the validity and applicability of the developed electrochemical sensor for the detection of Cd2+ ions were checked in real water samples, and 100% recovery was obtained.
The development of an efficient, selective, and highly sensitive electrochemical sensor for the simultaneous analysis of multiple drugs is a tough challenge. Herein, we report an applied electrochemical sensing platform comprising both acid-and base-functionalized carbon nanotubes (CNTs) with zinc oxide nanoparticles between the layers (COOH-CNTs/ ZnO/NH 2 -CNTs) for the detection of paracetamol, diclofenac, and orphenadrine (PAR, DIC, and ORP) drugs with ultrahigh sensitivity and selectivity as evidenced by intense and well-resolved voltammetric signals. Prior to electrochemical analysis, the nanocomposite/ glassy carbon electrode (GCE) surface was characterized by multiple spectroscopic techniques. The performance of f CNTs/ZnO/f CNTs/GCE was probed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave anodic stripping voltammetry (SWASV). The functionalized porous architecture with a large effective surface area provided a conduit for efficient mass transport and active sites for anchoring adsorbate molecules, thus leading to substantially lower oxidation overpotentials and amplified current signals. The f CNTs/ZnO/f CNTs/GCE exhibited a 6-fold increase in active surface area than bare GCE. Under optimized SWASV conditions, the designed sensor demonstrated simultaneous detection of PAR, DIC, and ORP with an unprecedented femtomolar limit of detection (46.8, 78, and 60 fM, respectively) within a time span of just 1 min. Besides the specificity, stability, and reliability studies of the designed sensing platform in multiple biological and pharmaceutical samples, % recoveries of 96−102% highlight the novelty and figures of merit of the designed electrochemical sensor. Moreover, computational studies were carried out that support the experimental outcome of a favorable charge transfer process between functional groups of the drugs and the sensor surface.
In this work, a simple and sensitive electrochemical method was developed to determine ethyl violet (EV) dye in aqueous systems by using square wave anodic stripping voltammetry (SWASV) employing a glassy carbon electrode modified with acidic-functionalized carbon nanotubes (COOH- f CNTs). In square wave anodic stripping voltammetry, EV exhibited a well-defined oxidation peak at 0.86 V at the modified GCE. Impedance spectroscopy and cyclic voltammetry were used to examine the charge transduction and sensing capabilities of the modified electrode. The influence of pH, deposition potential, and accumulation time on the electro-oxidation of EV was optimized. Under the optimum experimental conditions, the limit of detection with a value of 0.36 nM demonstrates high sensitivity of COOH- f CNTs/GCE for EV. After detection, it was envisioned to devise a method for the efficient removal of EV from an aqueous system. In this regard a photocatalytic degradation method of EV using Ho/TiO 2 nanoparticles was developed. The Ho/TiO 2 nanoparticles synthesized by the sol–gel method were characterized by UV–vis, XRD, FTIR, SEM, and EDX. The photocatalytic degradation studies revealed that basic medium is more suitable for a higher degradation rate of EV than acidic and neutral media. The photodegradation kinetic parameters were evaluated using UV–vis spectroscopic and electrochemical methods. The results revealed that the degradation process of EV follows first-order kinetics.
Herein, we present a greener approach to achieve an ultrasensitive, selective, and viable sensor engineered by amino acids as a recognition layer for simultaneous electrochemical sensing of toxic heavy metals (HMs). Electrochemical techniques like electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and square-wave anodic stripping voltammetry (SWASV) were applied to demonstrate sensing capabilities of the designed analytical tool. The comparative results of different amino acids demonstrate alanine’s superior performance with a well-resolved and enhanced current signal for target metal ions due to strong complexation of its functional moieties. The working conditions for alanine-modified GCE were optimized by investigating the effect of alanine concentration, different supporting electrolytes, pH values, accumulation potentials, and time. The limits of detection for Zn2+, Cd2+, Cu2+, and Hg2+ were found to be 8.92, 5.77, 3.01, and 5.89 pM, respectively. The alanine-modified electrode revealed absolute discrimination ability, stability, and ultrasensitivity toward metal ions even in the presence of multifold interfering species. Likewise, greener modifier-designed electrodes possessed remarkable electrocatalytic activity, cost affordability, reproducibility, and applicability for picomolar level detection of HM ions in real water sample matrixes. Theoretical calculations for the HM–amino acid interaction also support a significantly improved mediator role of the alanine modifier that is consistent with the experimental findings.
Development of an ultra-sensitive electrochemical platform for the simultaneous detection of two high blood pressure drugs.
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