Research

14 pages, 8310 KiB

Open AccessArticle

All-Solid-State Potentiometric Platforms Modified with a Multi-Walled Carbon Nanotubes for Fluoxetine Determination

by Hisham S. M. Abd-Rabboh, Heba M. Hashem, Layla M. S. Al Shagri, Abdel El-Galil E. Amr, Abdulrahman A. Almehizia, Ahmed M. Naglah and Ayman H. Kamel

Membranes 2022, 12(5), 446; https://doi.org/10.3390/membranes12050446 - 21 Apr 2022

Cited by 5 | Viewed by 1684

Abstract

Novel cost-effective screen-printed potentiometric platforms for simple, fast, and accurate assessment of Fluoxetine (FLX) were designed and characterized. The potentiometric platforms integrate both the FLX sensor and the reference Ag/AgCl electrode. The sensors were based on the use of 4′-nitrobenzo-15-crown-5 (ionophore I), dibenzo-18-crown-6 [...] Read more.

Novel cost-effective screen-printed potentiometric platforms for simple, fast, and accurate assessment of Fluoxetine (FLX) were designed and characterized. The potentiometric platforms integrate both the FLX sensor and the reference Ag/AgCl electrode. The sensors were based on the use of 4′-nitrobenzo-15-crown-5 (ionophore I), dibenzo-18-crown-6 (ionophore II), and 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) (ionophore III) as neutral carriers within a plasticized PVC matrix. Multiwalled carbon nanotubes (MWCNTs) were used as a lipophilic ion-to-electron transducing material and sodium tetrakis [3,5-bis(trifluoromethyl)phenyl] borate (NaTFPB) was used as an anionic excluder. The presented platforms revealed near-Nernstian potentiometric response with slopes of 56.2 ± 0.8, 56.3 ± 1.7 and 64.4 ± 0.2 mV/decade and detection limits of 5.2 × 10⁻⁶, 4.7 × 10⁻⁶ and 2.0 × 10⁻⁷ M in 10 mM Tris buffer solution, pH 7 for sensors based on ionophore I, II, and III, respectively. All measurements were carried out in 10 mM tris buffer solution at pH 7.0. The interfacial capacitance before and after insertion of the MWCNTs layer was evaluated for the presented sensors using the reverse-current chronopotentiometry. The sensors were introduced for successful determination of FLX drug in different pharmaceutical dosage forms. The results were compared with those obtained by the standard HPLC method. Recovery values were calculated after spiking fixed concentrations of FLX in different serum samples. The presented platforms can be potentially manufacturable at large scales and provide a portable, rapid, disposable, and cost-effective analytical tool for measuring FLX. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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12 pages, 1837 KiB

Open AccessArticle

Hydrous Cerium Dioxide-Based Materials as Solid-Contact Layers in Potassium-Selective Electrodes

by Nikola Lenar, Robert Piech and Beata Paczosa-Bator

Membranes 2022, 12(4), 349; https://doi.org/10.3390/membranes12040349 - 22 Mar 2022

Cited by 5 | Viewed by 1745

Abstract

This paper introduces hydrous cerium dioxide applied for the first time as a solid-contact layer in ion-selective electrodes. Cerium dioxide belongs to the group of metal oxides that exhibit both redox activity and a large surface area and therefore was considered to be [...] Read more.

This paper introduces hydrous cerium dioxide applied for the first time as a solid-contact layer in ion-selective electrodes. Cerium dioxide belongs to the group of metal oxides that exhibit both redox activity and a large surface area and therefore was considered to be an appropriate material for the solid-contact layer in potentiometric sensors. The material was examined both standalone and as a component of composite materials (with the addition of carbon nanomaterial or conducting polymer). Three cerium dioxide-based materials were tested as solid-contact layers in potentiometric sensors in the context of their microstructure, wettability, and electrical properties. The addition of hydrous cerium dioxide was shown to enhance the properties of carbon nanotubes and poly(3-octylthiophene-2,5-diyl) by increasing the value of electrical capacitance (798 μF and 112 μF for hCeO₂-NTs and hCeO₂-POT material, respectively) and the value of contact angle (100° and 120° for hCeO₂-NTs and hCeO₂-POT material, respectively). The proposed sensor preparation method is easy, without the need to use an advanced apparatus or specific conditions, and fast; sensors can be prepared within an hour. Designed hCeO₂-based electrodes exhibit competitive linear range and potential stability within the wide range of pH values (2.0–11.5). Designed electrodes are dedicated to potassium determination in environmental and clinical samples. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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12 pages, 3281 KiB

Open AccessArticle

Solid-Contact Potentiometric Anion Sensing Based on Classic Silver/Silver Insoluble Salts Electrodes without Ion-Selective Membrane

by Chunxian Liao, Lijie Zhong, Yitian Tang, Zhonghui Sun, Kanglong Lin, Longbin Xu, Yan Lyu, Dequan He, Ying He, Yingming Ma, Yu Bao, Shiyu Gan and Li Niu

Membranes 2021, 11(12), 959; https://doi.org/10.3390/membranes11120959 - 05 Dec 2021

Cited by 8 | Viewed by 2895

Abstract

Current solid potentiometric ion sensors mostly rely on polymeric-membrane-based, solid-contact, ion-selective electrodes (SC-ISEs). However, anion sensing has been a challenge with respect to cations due to the rareness of anion ionophores. Classic metal/metal insoluble salt electrodes (such as Ag/AgCl) without an ion-selective membrane [...] Read more.

Current solid potentiometric ion sensors mostly rely on polymeric-membrane-based, solid-contact, ion-selective electrodes (SC-ISEs). However, anion sensing has been a challenge with respect to cations due to the rareness of anion ionophores. Classic metal/metal insoluble salt electrodes (such as Ag/AgCl) without an ion-selective membrane (ISM) offer an alternative. In this work, we first compared the two types of SC-ISEs of Cl⁻ with/without the ISM. It is found that the ISM-free Ag/AgCl electrode discloses a comparable selectivity regarding organic chloride ionophores. Additionally, the electrode exhibits better comprehensive performances (stability, reproducibility, and anti-interference ability) than the ISM-based SC-ISE. In addition to Cl⁻, other Ag/AgX electrodes also work toward single and multi-valent anions sensing. Finally, a flexible Cl⁻ sensor was fabricated for on-body monitoring the concentration of sweat Cl⁻ to illustrate a proof-of-concept application in wearable anion sensors. This work re-emphasizes the ISM-free SC-ISEs for solid anion sensing. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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12 pages, 5609 KiB

Open AccessArticle

Graphene Flakes Decorated with Dispersed Gold Nanoparticles as Nanomaterial Layer for ISEs

by Barbara Niemiec, Nikola Lenar, Robert Piech, Krzysztof Skupień and Beata Paczosa-Bator

Membranes 2021, 11(7), 548; https://doi.org/10.3390/membranes11070548 - 20 Jul 2021

Viewed by 1813

Abstract

This paper proposes a new type of solid-contact layer based on graphene/gold nanoparticles for ion-selective electrodes. A novel approach to preparing the material for intermediate layer by modifying the graphene flakes by gold nanoparticles is presented. With this approach, we observed a large [...] Read more.

This paper proposes a new type of solid-contact layer based on graphene/gold nanoparticles for ion-selective electrodes. A novel approach to preparing the material for intermediate layer by modifying the graphene flakes by gold nanoparticles is presented. With this approach, we observed a large surface area of material and in consequence high electrical capacitance of electrodes. We have obtained satisfactory results demonstrating that the modification of graphene with gold allows for enhancing electrical and wetting properties of carbon nanomaterial. Electrical capacitance of designed nanocomposite-contacted electrode equals to approximately 280 µF, which in consequence ensures great long-term potential stability defined by the potential drift of 36 μV/h. The modification of graphene with nanoparticles completely changed its wetting properties, as the designed material turned out to be hydrophobic with a water contact angle of 115°. Graphene/gold nanoparticles–contacted electrodes are insensitive to the changing light conditions, exhibiting near-Nernstian response in the potassium concentration range between 10^−5.9 M and 10⁻¹ M of K⁺ ions and may be applied in the pH range between 2 and 10.5. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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14 pages, 6845 KiB

Open AccessArticle

Catalytic Adsorptive Stripping Voltammetric Determination of Germanium Employing the Oxidizing Properties of V(IV)-HEDTA Complex and Bismuth-Modified Carbon-Based Electrodes

by Agnieszka Królicka, Jerzy Zarębski and Andrzej Bobrowski

Membranes 2021, 11(7), 524; https://doi.org/10.3390/membranes11070524 - 13 Jul 2021

Cited by 4 | Viewed by 2110

Abstract

An efficient procedure that may be used to determine germanium traces and combines the advantages of catalytic adsorptive stripping voltammetry (CAdSV) with the convenience of screen-printed electrodes was developed. To induce the CAdSV response of the germanium(IV)-catechol complex, the vanadium(IV)-HEDTA compound was employed [...] Read more.

An efficient procedure that may be used to determine germanium traces and combines the advantages of catalytic adsorptive stripping voltammetry (CAdSV) with the convenience of screen-printed electrodes was developed. To induce the CAdSV response of the germanium(IV)-catechol complex, the vanadium(IV)-HEDTA compound was employed in combination with various bismuth-modified homogeneous (glassy carbon, gold coated with a bismuth layer via physical vapor deposition) and heterogeneous (screen-printed carbon, mesoporous carbon, graphene and reduced graphene oxide, polymer-encapsuled carbon fiber) electrodes. This solution had never before been implemented for this purpose. To achieve the most favorable performance of the working electrode, the parameters of bismuth deposition were optimized using a central composite design methodology. SEM imaging and contact angle measurements confirmed the long-term stability and high chemical resistance of the electrodes against the oxidizing action of V(IV)-HEDTA. Under optimized conditions, the method made it possible to detect nanomolar concentrations of germanium with favorable detection limits, high sensitivity, and a wide linear range of 5–90 nM of Ge(IV). Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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17 pages, 4372 KiB

Open AccessArticle

MnO₂@Reduced Graphene Oxide Nanocomposite-Based Electrochemical Sensor for the Simultaneous Determination of Trace Cd(II), Zn(II) and Cu(II) in Water Samples

by Siyamthanda Hope Mnyipika, Tshimangadzo Saddam Munonde and Philiswa Nosizo Nomngongo

Membranes 2021, 11(7), 517; https://doi.org/10.3390/membranes11070517 - 09 Jul 2021

Cited by 19 | Viewed by 3167

Abstract

The rapid detection of trace metals is one of the most important aspect in achieving environmental monitoring and protection. Electrochemical sensors remain a key solution for rapid detection of heavy metals in environmental water matrices. This paper reports the fabrication of an electrochemical [...] Read more.

The rapid detection of trace metals is one of the most important aspect in achieving environmental monitoring and protection. Electrochemical sensors remain a key solution for rapid detection of heavy metals in environmental water matrices. This paper reports the fabrication of an electrochemical sensor obtained by the simultaneous electrodeposition of MnO₂ nanoparticles and RGO nanosheets on the surface of a glassy carbon electrode. The successful electrodeposition was confirmed by the enhanced current response on the cyclic voltammograms. The XRD, HR-SEM/EDX, TEM, FTIR, and BET characterization confirmed the successful synthesis of MnO₂ nanoparticles, RGO nanosheets, and MnO₂@RGO nanocomposite. The electrochemical studies results revealed that MnO₂@RGO@GCE nanocomposite considerably improved the current response on the detection of Zn(II), Cd(II) and Cu(II) ions in surface water. These remarkable improvements were due to the interaction between MnO₂ nanomaterials and RGO nanosheets. Moreover, the modified sensor electrode portrayed high sensitivity, reproducibility, and stability on the simultaneous determination of Zn(II), Cd(II), and Cu(II) ions. The detection limits of (S/N = 3) ranged from 0.002–0.015 μg L⁻¹ for the simultaneous detection of Zn(II), Cd(II), and Cu(II) ions. The results show that MnO₂@RGO nanocomposite can be successfully used for the early detection of heavy metals with higher sensitivity in water sample analysis. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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14 pages, 21539 KiB

Open AccessFeature PaperArticle

Development of a Glucose Sensor Based on Glucose Dehydrogenase Using Polydopamine-Functionalized Nanotubes

by Won-Yong Jeon, Hyug-Han Kim and Young-Bong Choi

Membranes 2021, 11(6), 384; https://doi.org/10.3390/membranes11060384 - 24 May 2021

Cited by 21 | Viewed by 3637

Abstract

The electrochemical-based detection of glucose is widely used for diagnostic purposes and is mediated by enzyme-mediated signal transduction mechanisms. For such applications, recent attention has focused on utilizing the oxygen-insensitive glucose dehydrogenase (GDH) enzyme in place of the glucose oxidase (GOx) enzyme, which [...] Read more.

The electrochemical-based detection of glucose is widely used for diagnostic purposes and is mediated by enzyme-mediated signal transduction mechanisms. For such applications, recent attention has focused on utilizing the oxygen-insensitive glucose dehydrogenase (GDH) enzyme in place of the glucose oxidase (GOx) enzyme, which is sensitive to oxygen levels. Currently used Ru-based redox mediators mainly work with GOx, while Ru(dmo–bpy)₂Cl₂ has been proposed as a promising mediator that works with GDH. However, there remains an outstanding need to improve Ru(dmo–bpy)₂Cl₂ attachment to electrode surfaces. Herein, we report the use of polydopamine-functionalized multi-walled carbon nanotubes (PDA-MWCNTs) to effectively attach Ru(dmo–bpy)₂Cl₂ and GDH onto screen-printed carbon electrodes (SPCEs) without requiring a cross–linker. PDA-MWCNTs were characterized by Fourier transform infrared (FT–IR) spectroscopy, Raman spectroscopy, and thermal gravimetric analysis (TGA), while the fabrication and optimization of Ru(dmo–bpy)₂Cl₂/PDA-MWCNT/SPCEs were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements. The experimental results demonstrate a wide linear range of glucose-concentration-dependent responses and the multi-potential step (MPS) technique facilitated the selective detection of glucose in the presence of physiologically relevant interfering species, as well as in biological fluids (e.g., serum). The ease of device fabrication and high detection performance demonstrate a viable pathway to develop glucose sensors based on the GDH enzyme and Ru(dmo–bpy)₂Cl₂ redox mediator and the sensing strategy is potentially extendable to other bioanalytes as well. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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13 pages, 8257 KiB

Open AccessArticle

The Origin of the Non-Constancy of the Bulk Resistance of Ion-Selective Electrode Membranes within the Nernstian Response Range

by Valentina Keresten, Elena Solovyeva and Konstantin Mikhelson

Membranes 2021, 11(5), 344; https://doi.org/10.3390/membranes11050344 - 07 May 2021

Cited by 6 | Viewed by 2324

Abstract

The dependence of the bulk resistance of membranes of ionophore-based ion-selective electrodes (ISEs) on the composition of mixed electrolyte solutions, within the range of the Nernstian potentiometric response, is studied by chronopotentiometric and impedance measurements. In parallel to the resistance, water uptake by [...] Read more.

The dependence of the bulk resistance of membranes of ionophore-based ion-selective electrodes (ISEs) on the composition of mixed electrolyte solutions, within the range of the Nernstian potentiometric response, is studied by chronopotentiometric and impedance measurements. In parallel to the resistance, water uptake by the membranes is also studied gravimetrically. The similarity of the respective curves is registered and explained in terms of heterogeneity of the membranes due to the presence of dispersed aqueous phase (water droplets). It is concluded that the electrochemical equilibrium is established between aqueous solution and the continuous organic phase, while the resistance refers to the membrane as whole, and water droplets hamper the charge transfer across the membranes. In this way, it is explained why the membrane bulk resistance is not constant within the range of the Nernstian potentiometric response of ISEs. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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13 pages, 23048 KiB

Open AccessArticle

Potassium-Selective Solid-Contact Electrode with High-Capacitance Hydrous Iridium Dioxide in the Transduction Layer

by Nikola Lenar, Robert Piech, Jan Wyrwa and Beata Paczosa-Bator

Membranes 2021, 11(4), 259; https://doi.org/10.3390/membranes11040259 - 04 Apr 2021

Cited by 6 | Viewed by 2060

Abstract

This work presents new material for solid-contact layers—hydrous iridium dioxide IrO₂·2H₂O, characterized by high electrical capacitance value, evaluated using chronopotentiometry (1.22 mF) and electrochemical impedance spectroscopy (1.57 mF). The remarkable electrical parameters of layers resulted in great analytical parameters [...] Read more.

This work presents new material for solid-contact layers—hydrous iridium dioxide IrO₂·2H₂O, characterized by high electrical capacitance value, evaluated using chronopotentiometry (1.22 mF) and electrochemical impedance spectroscopy (1.57 mF). The remarkable electrical parameters of layers resulted in great analytical parameters of IrO₂·2H₂O-contacted potassium-selective electrodes. Various parameters of ion-selective electrodes were examined in the scope of this work using a potentiometry method including: linear range, repeatability, stability of potentiometric response and sensitivity to varying measurement conditions. The analytical parameters obtained for solid-contact electrodes were compared with the ones obtained for coated disc electrodes to evaluate the influence of the iridium dioxide layer. The linear range of the IrO₂·2H₂O-contacted K⁺-selective electrodes covered concentrations of K⁺ ions from 10⁻⁶ to 10⁻¹ M and the potential stability was estimated at 0.097 mV/h. The IrO₂·2H₂O-contacted electrodes turned out to be insensitive to varying light exposure and changes in the pH values of measured solutions (in the pH range of 2 to 10.5). A water layer test proved that, contrary to the coated disc electrode, the substantial water film is not formed between the ion-selective membrane and iridium dioxide layer. Full article

(This article belongs to the Special Issue Electrochemical Sensors Based on Nanomaterial Layers)

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