Analytical & Bioanalytical Electrochemistry
Volume:14 Issue: 5, May 2022

In this paper, we developed a simple and disposable electrochemical paper-based immunosensor (e-PI) based on manual screen printing method via patterned sticker label film on paper. The proposed electrochemical sensors provide the opportunity for economical single-use analysis of biological samples. The e-PI was constructed with hydrophobic glossy paper layers on a wax paper substrate to define three-electrode system. A carbon ink was used for construction of e-PI which composed of the graphite powder and cellulose acetate. The stability of the e-PI was evaluated using electrochemical methods. Carbohydrate antigen 15-3 (CA15-3) antibodies to the target CA15-3 antigen were immobilized on gold-modified graphite electrodes on the e-PI. Electrochemical properties of e-PI were investigated by cyclic voltammetry, differential pulse voltammetry and electrochemical impedance spectroscopy. The fabricated e-PI offers a vast linear range from 0.5 to 200 U mL−1 with a low limit of detection 0.15 U mL−1. Furthermore, the fabricated e-PI has acceptable stability, accuracy and high sensitivity.

A novel photoelectrocatalyst composed from multiwalled carbon nanotubes (MWCNTs), titanium dioxide (TiO2) and gold-platinum bimetallic nanoparticles (Au–PtNPs) was prepared on the surface of a fluorine-tin oxide (FTO) electrode and it was used for electrooxidation of ethanol molecules. Multiwalled carbon nanotubes were utilized as the catalyst support to improve the electrical transmission. The TiO2 nanoparticles were transferred onto the surface of MWCNTs/FTO modified electrode and then, the surface of the electrode was coated with gold-platinum nanoparticles. The surface morphology and chemical composition of the prepared Au-Pt/TiO2/MWCNTs photoelectrocatalyst were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. The fabrication process of the photoelectrocatalyst was investigated by cyclic voltammetry and chronoamperometry techniques. The exchange current densities (J0) were calculated for Pt/FTO, Pt/MWCNTs/FTO, Pt/TiO2/MWCNTs/FTO and Au-Pt/TiO2/MWCNT/FTO electrodes and they were found to be:  4.10 × 10-5, 6.06 × 10-5, 1.45 × 10-4 and 1.89 × 10-4 mA cm-2, respectively. Also, the values of J0 for Pt/TiO2/MWCNTs/FTO and Au-Pt/TiO2/MWCNTs/FTO in the presence of light were obtained 2.0 × 10-4 and 5.1 × 10-4 mA cm-2, respectively. The obtained results reveal that the Au-Pt/TiO2/MWCNTs/FTO electrode has the higher J0 value in the presence of UV-Vis light and the light irradiation can accelerate the ethanol oxidation process. The experimental results showed that the proposed photoelectrocatalyst has an excellent catalytic activity for oxidation of ethanol molecules under the UV-Vis light irradiation which is due to the synergistic effect between the TiO2 photocatalyst and gold-platinum electrocatalyst.

A simultaneous electrochemical determination of serotonin (Ser), melatonin (Mel) and, tryptophan (Trp) was conducted for the first time in the presented research. A metal-metal-metal oxide nanocomposite (CuNi-CeO2-rGO) was synthesized and for modification of glassy carbon electrode (GCE), it was decorated at reduced graphene oxide (rGO). The differential pulse voltammetry (DPV) technique was applied to measurement of Ser, Mel and Trp at the surface of CuNi-CeO2-rGO/GCE. The electrical impedance spectroscopy (EIS) analysis of prepared bare and modified electrodes showed that the CuNi-CeO2-rGO/GCE has the lowest charge transfer resistant in comparison to GCE. The Transmission electron microscopy (TEM) and, X-ray Diffraction (XRD) techniques applied to check the characterization of synthesized nanomaterials. In contrast to the GCE, three separated and well-defined peaks appeared at the CuNi-CeO2-rGO/GCE at 369, 570 and 706 mV for Ser, Mel and Trp in the electrochemical potential window of 0.1-1.0 V. The chemical and electrochemical conditions of analysis were optimized and the detection limit of 5.8 nM (0.0058 µM) for Ser, 6.1 nM (0.0061 µM) for Mel and 6.3 nM (0.0063 µM) for Trp, were calculated based on 3Signal/Noise. The applicability of the CuNi-CeO2-rGO/GCE was investigated by determining target analytes in human urine and blood plasma and comparing the obtained data with HPLC data. The obtained data were in good agreement with each other which demonstrates that the presented method was one of the best analytical methods for the monitoring of Ser, Mel and Trp in the laboratory.

In this paper, a novel integrated system for power generation and freshwater production is proposed. The system consists of Proton exchange membrane fuel cell (PEMFC), photovoltaic (PV) thermal cells and Proton exchange membrane electrolyzer (PEME) in addition to a membrane distillation (MD) system for freshwater production. The proposed system is assessed from thermodynamics viewpoints through first and second law analyses and the modeling and simulation of the subsystems are conducted in EES software to provide a comprehensive assessment concerning thermodynamic criteria. Simulation of each subsystem is validated by considering the reported data in the previous works. The proposed system is subsequently optimized via a multi-objective optimization method based on genetic algorithm. The results showed that PV cell temperature and PV area are the main influential parameters that can affect the power output and exergy efficiency. The optimization results show that at a well-balanced operating point, power and exergy efficiency would be 30 kW and 11.7%, respectively.

Today, remarkable growth in the generation and abuse of drugs lead to the need for fast, simple, selective, and sensitive methods for their detection. Tramadol is one of the most abused drugs that can make addiction. A highly conductive and highly sensitive voltammetric method is developed for the determination of tramadol based on a 1-methyl-3-butyl imidazolium bromide/praseodymium hydroxide-graphene quantum dots nanocomposite modified carbon paste electrode (1-M-3-BBr/Pr(OH)3-GQD/CPE). According to the obtained voltammograms, the 1-M-3-BBr/Pr(OH)3-GQD/CPE exhibits high catalytic activity on the oxidation signal of tramadol. Tramadol shows an irreversible anodic oxidation peak in the potentials of ~1170 mV and ~1230 mV at the surface of a modified and unmodified CPE, respectively. Square wave voltammogram signals confirmed that the oxidation current of tramadol was increased linearly with its concentration in the range of 9.0×10-9-3.0×10-4 mol L-1 with a detection limit of 3.0×10−9 mol L-1. Finally, the 1-M-3-BBr/Pr(OH)3-GQD/CPE was effectively used for the determination of tramadol in some real samples with an acceptable selectivity.

Incorporation of N and S containing porous graphite (NSPG) in the composition of carbon paste electrodes (CPEs) can improve their sensing behavior. Result of former studies have indicated the selective interaction of N, N-bis(a-methylsalicylidene) diethylenetriamine (BMT) and Pr3+ ions, as opposed to other lanthanide ions. In this light, BMT was incorporated into a mixed matrix of NSPG and graphite powder to obtain a modified Pr3+ potentiometric sensor. The results indicated that the nano-composite sensor offers enhanced sensitivity, selectivity; response time; response stability and lifetime in comparison to CPEs modified using multiwall carbon nanotube (MWCNT). The optimal response (i.e. a Nernstian response of 19.7±0.3 mV per decade from 1.0×10-7 to 1.0×10-2 mol L-1) was observed for a sensor containing 10% NSPG, 15% BMT, 30% IL and 45 % graphite powder.