Pencil Lead Electrode Modified with Hemoglobin Film as a Novel Biosensor for Nitrite Determination

In Situ Preparation of Metallic Copper Nanosheets/Carbon Paper Sensitive Electrodes for Low-Potential Electrochemical Detection of Nitrite

In the realm of electrochemical nitrite detection, the potent oxidizing nature of nitrite typically necessitates operation at high detection potentials. However, this study introduces a novel approach to address this challenge by developing a highly sensitive electrochemical sensor with a low reduction detection potential. Specifically, a copper metal nanosheet/carbon paper sensitive electrode (Cu/CP) was fabricated using a one-step electrodeposition method, leveraging the catalytic reduction properties of copper's high occupancy d-orbital. The Cu/CP sensor exhibited remarkable performance in nitrite detection, featuring a low detection potential of -0.05 V vs. Hg/HgO, a wide linear range of 10~1000 μM, an impressive detection limit of 0.079 μM (S/N = 3), and a high sensitivity of 2140 μA mM-1cm-2. These findings underscore the efficacy of electrochemical nitrite detection through catalytic reduction as a means to reduce the operational voltage of the sensor. By showcasing the successful implementation of this strategy, this work sets a valuable precedent for the advancement of electrochemical low-potential nitrite detection methodologies.

Green synthesis of copper oxide nanoparticles using Ficus elastica extract for the electrochemical simultaneous detection of Cd2+, Pb2+, and Hg2

In this paper, for the first time, we report the use of a new carbon paste electrode based on a low-cost pencil graphite powder modified with polyaniline (PANI) and green synthesized copper oxide nanoparticles using Ficus elastica extract as a sensor for Cd²⁺, Pb²⁺, and Hg²⁺. The elaborated electrode was characterized by FT-IR spectroscopy, field-emission gun scanning electron microscopy (FEG-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and simultaneous thermal analysis (TGA/DSC). The electrochemical behavior of the sensor was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy techniques. According to CV, as well as square wave voltammetry (SWV) results, it was found that the CuONPs/PANI-CPE sensor was able to determine very low concentrations of Cd²⁺, Pb²⁺, and Hg²⁺ in HCl (0.01 M) either in single metal or in multi-metal solutions with a high sensitivity. Furthermore, Cd²⁺, Pb²⁺, and Hg²⁺ simultaneous detection on CuONPs/PANI-CPE achieved very low limits of detection (0.11, 0.16, and 0.07 μg L^-1, respectively). Besides, the designed sensor displayed a good selectivity, reproducibility, and stability. Moreover, CuONPs/PANI-CPE enabled us to determine with high accuracy Cd²⁺, Pb²⁺, and Hg²⁺ traces in environmental matrices.

Electrochemically activated pencil lead electrode as a sensitive voltammetric sensor to determine gallic acid

An electrochemical sensor for the determination of some polyphenolic compounds such as Gallic acid (GA) and Galloyl esters was developed using the activated pencil lead electrode (APLE). At first, a study has been made of the optimum conditions for electrochemical activation of the pencil lead electrode. Potentiodynamic and potentiostatic strategies were investigated for activation of the pencil lead electrode and the results show that the potentiodynamic pretreatment gives better performance toward measurement of the polyphenolic compounds. Electrochemical properties of GA were investigated using chronoamperometry and cyclic voltammetry; and some thermodynamic and kinetic variables such as α, n _α, and D were calculated. Sensitive differential pulse voltammetry (DPV) technique was applied for the determination of Gallic acid and Galloyl esters in different samples. Enhanced oxidation peak currents of Gallic acid were observed at APLE when compared with non-activated PLE. The calibration graph has two linear ranges of 0.49-24.3 µM and 0.07-0.83 mM, and the obtained limit of detection for S/N = 3 was 0.25 µM. Adsorptive stripping differential pulse voltammetry (AdSDPV) was also conducted to determine Gallic acid and Galloyl esters in sub-micromolar concentration range. Using the AdSDPV method, the limit of detection was improved and calculated to be 5.2 nM. The proposed method was successfully applied for quantification of the total concentration of Gallic acid and Galloyl esters in a variety of real samples such as black and green tea, and mango juice samples, and desirable recovery values indicated the good accuracy of the developed sensor.