A novel electrochemical glucose sensor was developed, based on a multiwall carbon nanotubes (MWCNTs)-copper-1,3,5-benzenetricarboxylic acid (CuBTC)-epoxy composite electrode, named MWCNT-CuBTC. The electrode nanocomposite was prepared by a two-roll mill procedure and characterized morphostructurally by scanning electron microscopy (SEM). The CuBTC formed defined crystals with a wide size distribution, which were well dispersed and embedded in the MWCNTs. Its electrical conductivity was determined by four-point probe contact (DC) conductivity measurements. The electroactive surface area, determined using cyclic voltammetry (CV), was found to be 6.9 times higher than the geometrical one. The results of the electrochemical measurements using CV, linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), chronoamperometry (CA) and multiple pulse amperometry (MPA) showed that the MWCNT-CuBTC composite electrode displayed high electrocatalytic activity toward the oxidation of glucose and, as a consequence, very high sensitivity. The best sensitivity of 14,949 µAmM⁻¹cm⁻¹ was reached using MPA at the potential value of 0.6 V/SCE, which was much higher in comparison with other copper-based electrodes reported in the literature. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of an effective glucose sensor.

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Three types of composite electrode materials, i.e. carbon nanotubes-epoxy (CNT), zeolite-carbon nanotubes-epoxy (ZCNT) and TiO₂-modified zeolite-carbon nanotubes-epoxy (TiZCNT), were synthesized, morphologically and electrically characterized, and tested in the photoelectrodegradation of pentachlorophenol (PCP) from water. The electrode composite materials were synthesized by the two-roll mill method, and a higher porosity of zeolite-modified electrode, caused by the zeolite incorporation, was noticed by means of scanning electron microscopy. Electroactive surface area, determined by classical methods using cyclic voltammetry (CV), and electric conductivity, determined by the four-point method, were negatively affected by the presence of zeolite. The photoelectrochemical behaviour of the electrodes, under ultraviolet (UV) irradiation, towards the pentachlorophenol oxidation was studied, and the photoelectrocatalytic activity of each electrode was determined. The PCP oxidation occurred in two steps at +0.65 V and +0.94 V vs. saturated calomel electrode SCE under UV irradiation. The oxidation peak recorded at +0.65 V vs. SCE appeared only under UV irradiation and it is considered that the photoelectrooxidation peak corresponded to PCP photoelectrooxidation. Also, the enhancement of PCP electrooxidation at +0.94 V vs. SCE was noticed under UV irradiation, which confirmed the photelectrocatalytic activity. The performance of the PCP degradation process, expressed as degradation efficiency and electrochemical efficiency, recommended the operation of photoelectrocatalysis at a bias voltage application of +0.8 V/SCE, while the mineralization degree recommended a bias voltage value of +1.5 V/SCE.

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The electrochemical methods-based protocol for simultaneous detection of tetracycline (TC) from antibiotics class and fluoxetine (FXT) from anti-depressive pharmaceuticals class, which belongs to emerging pollutants from water, was developed in this study using carbon nanofiber-epoxy composite electrode (CNF). The electrochemical behaviour of each pharmaceutical on CNF was considered the basis for simultaneous detection of both pharmaceuticals from water. TC electrooxidation on CNF occurred in two steps and, consequently, two detection potentials are considered. FXT electrooxidation occurred in one step that is overlaid to the first step of TC detection, this step being considered as cumulative for both pharmaceuticals. Each electrochemical method of cyclic voltammetry (CV) and differential-pulsed voltammetry (DPV) allowed detecting cumulative presence of TC and FXT at the detection potential ranged between 0.65 and 0.815 V vs. SCE and the selective detection of TC at the detection potential ranged between 0.956 and 1.14 V vs. SCE. The electroanalytical parameters related to the lowest limit of detection and sensitivity recommended this electrode to exhibit the potential for practical applications in the electrochemical detection of certain pharmaceuticals as emerging pollutants from water.

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Ammonium and nitrite are listed by Water Framework Directive as core parameters that should be monitored for the groundwater as drinking water source. This work describes the sensitive protocols for the simultaneous detection of ammonium and nitrite in water at a new silver-electrodecorated carbon nanotubes-epoxy composite electrode (Ag-CNT) using advanced voltammetric technique. A carbon nanotubes-epoxy composite electrode obtained by two-roll mill procedure was decorated electrochemically with silver nanoparticles. This new electrode displays excellent electrocatalytic activity towards the direct oxidation of ammonium and nitrite at well separated less potential values (+0.15 V/SCE for ammonium and +0.7 V/SCE for nitrite). Very good detection sensitivities (0.613 mA mM⁻¹ for ammonium and 0.980 mA mM⁻¹ for nitrite) and the lowest limits of detection (1 μM for ammonium and 0.7 μM for nitrite) were achieved by differential-pulsed voltammetry (DPV) under optimum operating conditions of 0.05 V step potential, 0.2 V modulation amplitude and the scan rate of 0.05 V s⁻¹. This detection protocol was successfully applied to the simultaneous determination of ammonium and nitrite in groundwater samples, and the results were found to be consistent with the values obtained by the standardized spectrophotometry methods.

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Monitoring of pesticide residues in food, beverages, and the environment requires fast, versatile, and sensitive analyzing methods. Direct electrochemical detection of pesticides could represent an efficient solution. Adequate electrode material, electrochemical technique, and optimal operation parameters define the detection method for practical application. In this study, cyclic voltammetric and differential pulse voltammetric techniques were used in order to individually and simultaneously detect two pesticides, i.e., carbaryl (CR) and paraquat (PQ), from an acetate buffer solution and also from natural apple juice. A graphene-modified boron-doped diamond electrode, denoted BDDGR, was obtained and successfully applied in the simultaneous detection of CR and PQ pesticides, using the differential pulse voltammetric technique with remarkable electroanalytical parameters in terms of sensitivity: 33.27 μA μM−1 cm−2 for CR and 31.83 μA μM−1 cm−2 for PQ. These outstanding results obtained in the acetate buffer supporting electrolyte allowed us to simultaneously detect the targeted pesticides in natural apple juice.@en