Fast Heterogeneous Electron Transfer Research Articles

Sustainable Laser Induced Supercapacitors from Cork Natural Substrates

A novel type of eco-friendly and cost-effective supercapacitor has been developed by fabricating interdigitated and squared supercapacitors made of porous graphitic carbon electrodes and Polyvinyl alcohol (PVA) electrolyte. The electrodes were fabricated using a simple, fast, and low-cost laser engraving process, using visible irradiation wavelengths (450 nm) and performed under ambient conditions, resulting in highly three-dimensional, electrically conductive, and porous graphitic carbon structures.By adjusting the laser power and wavelength, it was possible to produce electrode materials with highly porous and high surface area morphology, which are promising for electrochemical applications. Spectral investigation using Raman and FTIR spectroscopies confirmed the formation of graphitic carbon structures and the full conversion of the cork precursor under visible laser irradiation.The obtained electrodes exhibited excellent supercapacitive behavior when exposed to a PVA electrolyte, achieving a specific areal capacitance of up to 11.24 mF/cm2 with PVA at 30% laser power. The supercapacitive properties showed excellent stability over time, with no significant loss after 10000 charge/discharge cycles.To evaluate the performance of the new supercapacitors, linear electrodes were used as working electrodes in a three-electrode configuration electrochemical cell. The electrodes showed diffusion-limited electrochemical behavior with fast heterogeneous electron transfer rates (HET), which was superior to that of traditional glassy carbon electrodes.The innovative and efficient electrode fabrication method presented in this study, which utilizes low-cost instrumentation, environmentally friendly fabrication methods, and Earth-abundant precursor materials, shows great promise for producing large-scale "green" electrochemical sensing platforms and devices in the future.

Pencil Graphite Electrocatalytic Sensors Modified by Pyrene Coated Reduced Graphene Oxide Decorated with Molybdenum Disulfide Nanoroses for Hydrazine and 4-Nitrophenol Detection in Real Water Samples.

Novel nanostructured platforms based on Pencil Graphite Electrodes (PGEs), modified with pyrene carboxylic acid (PCA) functionalized Reduced Graphene Oxide (rGO), and then decorated by chronoamperometry electrodeposition of MoS2 nanoroses (NRs) (MoS2NRs/PCA-rGO/PGEs) were manufactured for the electrocatalytic detection of hydrazine (N2H4) and 4-nitrophenol, pollutants highly hazardous for environment and human health. The surface morphology and chemistry of the MoS2NRs/PCA-rGO/PGEs were characterized by scanning electron microscopy (SEM), Raman, and X-ray photoelectron spectroscopy (XPS), assessing the coating of the PCA-rGO/PGEs by dense multilayers of NRs. N2H4 and 4-nitrophenol have been monitored by Differential Pulse Voltammetry (DPV), and the MoS2NRs/PCA-rGO/PGEs electroanalytical properties have been compared to the PGEs, as neat and modified by PCA-rGO. The MoS2NRs/PCA-rGO/PGEs demonstrated a higher electrochemical and electrocatalytic activity, due to their high surface area and conductivity, and very fast heterogeneous electron transfer kinetics at the interphase with the electrolyte. LODs lower than the U.S. EPA recommended concentration values in drinking water, namely 9.3 nM and 13.3 nM, were estimated for N2H4 and 4-nitrophenol, respectively and the MoS2NRs/PCA-rGO/PGEs showed good repeatability, reproducibility, storage stability, and selectivity. The effectiveness of the nanoplatforms for monitoring N2H4 and 4-nitrophenol in tap, river, and wastewater was addressed.

Influence of boron doped level on the electrochemical behavior and seawater salinity detection of boron doped diamond film electrodes

Boron doped diamond (BDD) film electrodes have a good application prospect in the field of seawater salinity detection. However, the influence mechanism of boron doping level (given by B/C ratio) on seawater salinity detection limited its application. In this paper, microstructure-phase-electrochemical relationships in BDD film electrodes were systematically investigated, aiming to reveal the effect of boron content on seawater salinity measurement, and lay a foundation for practical application of BDD film electrodes. With the increase of the boron doping, the content of non-diamond phase increased, while the crystallinity and the grain size of diamond decreased. Meanwhile, when the B/C ratio of BDD electrode reached 10000 ppm, they had the largest electroactive surface areas (EASA) and the smallest diffusion resistance, and their electrochemical performance was optimal in this study. In addition, BDD film electrode exhibited fast heterogeneous electron transfer in both internal Fe(CN)6−3/−4 and external Ru(NH3)6+2/+3 redox systems. Under the optimal parameter setting, the maximum signal response of BDD electrode at 40 ‰ was 69 mA/cm2 and the measurement error was less than 0.81 ‰. Appropriate proportion of sp2-C and B-sp3-C phases can significantly improve the detection performance of BDD electrode.

Synthesis of graphene interlayer diamond films for enhanced electrochemical performance

Boron doped polycrystalline diamond (BDD) films have shown great potential in electrochemical applications. However, the high background current and poor signal-to-noise ratio, caused by the crystal defects produced during the growth process, limit its application. This paper reports the controllable synthesis of a diamond/graphene/diamond (DGD) sandwich structure. The graphene interlayer is designed to act as a high-speed tunnel for the electronic transmission, and the outer diamond layers can completely maintain its inherent excellent features. This sandwich structure can effectively avoid the negative impact of surface non-diamond carbon relative to material properties, and obtain a wider electrochemical window (3.65 V) and a lower background current (about 0.4 μA cm−2). At the same time, this DGD electrode exhibits fast heterogeneous electron transfer in both the inner (Fe(CN)6−3/−4) and outer (Ru(NH3)6+2/+3) redox systems. By changing the preparation process of the middle G layer, the growth process of the G layer and its influence on the energy band and electrochemical performance of the electrode are analyzed in detail. In general, the DGD sandwich structure methodology paves a novel route for designing high-performance conductive diamond electrodes and holding great promise in electrochemical applications.

Support-Free PEDOT:PSS Fibers as Multifunctional Microelectrodes for In Vivo Neural Recording and Modulation.

In vivo microelectrodes are essential for neuroscience studies. However, development of microelectrodes with both flexibility and multifunctionality for recording chemical and electrical signals in the same extracellular microspace and modulating neural activity remains challenging. Here, we find that pure PEDOT:PSS fibers (i.e., support-free) exhibit high conductivity, fast heterogeneous electron transfer, and suitable charge storage and injection capabilities, and can thus directly act as microelectrodes not only for chemical and electrophysiological recording in the same extracellular microspace, but also for electromodulation of neural microcircuit activity. Moreover, the microelectrodes mechanically match with neural tissues, exhibiting less foreign body responses. Given the multifunctionality, flexibility, and biocompatibility, the support-free PEDOT:PSS-based microelectrodes offer a new avenue to microelectrode technology for neuroscience research, diagnostics and therapeutics.

Support‐Free PEDOT:PSS Fibers as Multifunctional Microelectrodes for In Vivo Neural Recording and Modulation

AbstractIn vivo microelectrodes are essential for neuroscience studies. However, development of microelectrodes with both flexibility and multifunctionality for recording chemical and electrical signals in the same extracellular microspace and modulating neural activity remains challenging. Here, we find that pure PEDOT:PSS fibers (i.e., support‐free) exhibit high conductivity, fast heterogeneous electron transfer, and suitable charge storage and injection capabilities, and can thus directly act as microelectrodes not only for chemical and electrophysiological recording in the same extracellular microspace, but also for electromodulation of neural microcircuit activity. Moreover, the microelectrodes mechanically match with neural tissues, exhibiting less foreign body responses. Given the multifunctionality, flexibility, and biocompatibility, the support‐free PEDOT:PSS‐based microelectrodes offer a new avenue to microelectrode technology for neuroscience research, diagnostics and therapeutics.

Enzyme-immobilized 3D silver nanoparticle/graphene aerogel composites towards biosensors

The detection of allergen sulfite is essential for food quality control and public health supervision. Here, a high-performance sulfite biosensor was developed from a sulfite oxidase enzyme (SOx) immobilized on silver nanoparticles (AgNPs) decorated on 3D reduced graphene oxide (3D-rGO). 3D-rGO with high specific pore volume and high electroactive surface area is ideal as a supporting material. AgNPs further provide high electrical conductivity or fast charge transfer and serve as an enzyme anchoring site via a stable thiol bonding. The composite material was initially functionalized with the folic acid and cysteine namely rGO@Ag-Cys-FA before immobilized with the SOx. The resultant rGO@Ag-Cys-FA-SOx exhibits high sensitivity and selectivity towards sulfite detection, high bio-electrocatalytic activity, and fast heterogeneous electron transfer rate constant. The biosensor is also tested in a continuous flow injection system to demonstrate the practical use. Besides, the as-produced sensor in this work can be used in the real sample, which is the canned fruit product indicating its potential practical application.

Laser Scribing Fabrication of Graphitic Carbon Biosensors for Label-Free Detection of Interleukin-6.

Interleukin-6 (IL-6) is an important immuno-modulating cytokine playing a pivotal role in inflammatory processes in disease induction and progression. As IL-6 serves as an important indicator of disease state, it is of paramount importance to develop low cost, fast and sensitive improved methods of detection. Here we present an electrochemical immunosensor platform based on the use of highly porous graphitic carbon electrodes fabricated by direct laser writing of commercial polyimide tapes and chemically modified with capture IL-6 antibodies. The unique porous and 3D morphology, as well as the high density of edge planes of the graphitic carbon electrodes, resulted in a fast heterogeneous electron transfer (HET) rate, k0 = 0.13 cm/s. The resulting immunosensor showed a linear response to log of concentration in the working range of 10 to 500 pg/mL, and low limit of detection (LOD) of 5.1 pg/mL IL-6 in phosphate buffer saline. The total test time was approximately 90 min, faster than the time required for ELISA testing. Moreover, the assay did not require additional sample pre-concentration or labelling steps. The immunosensor shelf-life was long, with stable results obtained after 6 weeks of storage at 4 °C, and the selectivity was high, as no response was obtained in the presence of another inflammatory cytokine, Interlukin-4. These results show that laser-fabricated graphitic carbon electrodes can be used as selective and sensitive electrochemical immunosensors and offer a viable option for rapid and low-cost biomarker detection for point-of-care analysis.

Surface Roughness and Electrochemical Performance Properties of Biosynthesized α-MnO2/NiO-Based Polyaniline Ternary Composites as Efficient Catalysts in Microbial Fuel Cells

In this study, biosynthesized α-MnO2/NiO NPs and chemically oxidative polyaniline (PANI) were synthesized to form ternary composite anode material for MFC. The synthesized materials were characterized with different materials (UV-Vis, FTIR, XRD, TGA-DTA-DSC, SEM-EDX-Gwyddion, CV, and EIS) to deeply examine their optical, structural, morphological, thermal, roughness, and electrocatalytic properties. The degree of surface roughness for α-MnO2/NiO/PANI was23.65±5.652 nm. This value was higher than the pure α-MnO2, pure PANI, and even α-MnO2/PANI nanocomposite due to surface modification. The total charge storing performance for bare PGE, α-MnO2/PGE, PANI/PGE, α-MnO2/PANI/PGE, and α-MnO2/NiO/PANI/PGE were 5.291, 17.267, 20.659, 23.258, and 24.456 mC. From this, the charge storing performance formed by α-MnO2/NiO/PANI-modified PGE was highest, indicating that this electrode is best in cycle stability and increases its life cycle during energy conversion time in MFC. This is also supported by its effective surface area, having a value of 0.00984 cm2. From this, it is evidenced that the ternary composite catalyst-modified anode facilitates the fast electrocatalytic activity as observed from its high peak current and lower peak-to-peak potential separation (ΔEp=0.216 V) than other electrodes. Such surface modification helps to store more electrical charge by increasing electrical conductivity during its charge/discharge processing time. In addition, the lower charge transfer resistance property with a value of 788.9 Ω and the fast heterogeneous electron transfer rate of ~2.92 s-1 enable to facilitate glucose oxidation, and this enhances to produce high power output and increase wastewater treatment efficiency. As a result, the bioelectrical activity of α-MnO2/NiO/PANI composite-modified PGE was very effective in producing a maximum power density of 506.96 mW m-2 with COD of 81.92%. The above observations justified that α-MnO2/NiO/PANI/PGE serves as an effective anode material in double-chambered MFC application.

Smart bandage with integrated multifunctional sensors based on MXene-functionalized porous graphene scaffold for chronic wound care management

Three-dimensional (3D) porous laser-guided graphene (LGG) electrodes on elastomeric substrates are of great significance for developing flexible functional electronics. However, the high sheet resistance and poor mechanical properties of LGG sheets obstruct their full exploitation as electrode materials. Herein, we applied 2D MXene nanosheets to functionalize 3D LGG sheets via a C–O–Ti covalent crosslink to obtain an LGG-MXene hybrid scaffold exhibited high conductivity and improved electrochemistry with fast heterogeneous electron transfer (HET) rate due to the synergistic effect between LGG and MXene. Then we transferred the obtained hybrid scaffold onto PDMS to engineer a smart, flexible, and stretchable multifunctional sensors-integrated wound bandage capable of assessing uric acid (UA), pH, and temperature at the wound site. The integrated UA sensor exhibited a rapid response toward UA in an extended wide range of 50–1200 μM with a high sensitivity of 422.5 μA mM−1 cm−2 and an ultralow detection limit of 50 μM. Additionally, the pH sensor demonstrated a linear Nernstian response (R2 = 0.998) with a high sensitivity of −57.03 mV pH−1 in the wound relevant pH range of 4–9. The temperature sensor exhibited a fast and stable linear resistive response to the temperature variations in the physiological range of 25–50 °C with an excellent sensitivity and correlation coefficient of 0.09% ⁰C−1 and 0.999, respectively. We anticipate that this stretchable and flexible smart bandage could revolutionize wound care management and have profound impacts on the therapeutic outcomes.

Nitrogen-doped carbon coated TiC nanofiber arrays deposited on Ti-6Al-4V for selective and sensitive electrochemical detection of dopamine

Core-shell titanium carbide/carbon (TiC@C) and titanium carbide/nitrogen-doped carbon (TiC@CNx) quasi-aligned nanofiber arrays (NFAs) are fabricated on biomedical Ti-6Al-4V by a simple thermal chemical process in the presence of benzene and pyridine at 800 °C, respectively. The morphology, structure, and composition of the TiC@C and TiC@CNx NFAs are characterized by X-ray diffraction, electron microscopy, energy-dispersive X-ray spectrometry, and Raman scattering spectroscopy. The TiC@C and TiC@CNx nanofibers consisting of highly conducting single-crystalline TiC cores and carbon shells or N-doped carbon shells have a large amount of defects and N doping endows the TiC@CNx NFAs with excellent electrochemical properties. The TiC@CNx NFAs electrode exhibits fast heterogeneous electron transfer (HET) kinetics in the Fe(CN)63−/4− redox couple showing an ideal peak-to-peak potential separation (59 mV) at a high scan rate of 7000 mV s−1. As a result, the TiC@CNx NFAs electrode has high activity in the simultaneous detection of dopamine (DA), ascorbic acid (AA), uric acid (UA), and serotonin (5-hydroxytryptamine, 5-HT) as well as high sensitivity and selectivity in the determination of DA in the presence of UA, AA, and 5-HT. The linear range for the determination of DA is 0.5–180 μM and detection limit is 8 nM (S/N = 3).

Physical contact between cytochrome c1 and cytochrome c increases the driving force for electron transfer

In oxidative phosphorylation, the transfer of electrons from reduced cofactors to molecular oxygen via the electron transport chain (ETC) sustains the electrochemical transmembrane potential needed for ATP synthesis. A key component of the ETC is complex III (CIII, cytochrome bc1), which transfers electrons from reduced ubiquinone to soluble cytochrome c (Cc) coupled to proton translocation into the mitochondrial intermembrane space. One electron from every two donated by hydroquinone at site P is transferred to Cc via the Rieske-cytochrome c1 (Cc1) pathway. According to recent structural analyses of CIII and its transitory complex with Cc, the interaction between the Rieske subunit and Cc1 switches intermittently during CIII activity. However, the electrochemical properties of Cc1 and their function as a wire between Rieske and Cc are rather unexplored. Here, temperature variable cyclic voltammetry provides novel data on the thermodynamics and kinetics of interfacial electron transfer of immobilized Cc1. Findings reveal that Cc1 displays two channels for electron exchange, with a remarkably fast heterogeneous electron transfer rate. Furthermore, the electrochemical properties are strongly modulated by the binding mode of the protein. Additionally, we show that electron transfer from Cc1 to Cc is thermodynamically favored in the immobilized Cc1-Cc complex. Nuclear Magnetic Resonance, HADDOCK, and Surface Plasmon Resonance experiments provide further structural and functional data of the Cc1-Cc complex. Our data supports the Rieske-Cc1-Cc pathway acting as a unilateral switch thyristor in which redox potential modulation through protein-protein contacts are complemented with the relay-like Rieske behavior.

Siloxene, Germanane, and Methylgermanane: Functionalized 2D Materials of Group 14 for Electrochemical Applications

Abstract2D monoelemental group 14 materials beyond graphene, such as silicene and germanene, have recently gained a lot of attention. Covalent functionalization of group 14 layered materials can lead to significant tuning of their properties. While optical and electronic properties of germanene, silicene, and their derivatives have been studied in detail previously, there is no information on their electrochemistry and toxicity. Herein, electrochemical applications of 2D siloxene, germanane, and methylgermanane, specifically for detection of an important biomarker, dopamine, as well as catalyzation of oxygen reduction and hydrogen evolution reactions, which are important in energy applications, are explored. Among the three materials, germanane portrays most superior properties for the electrochemical applications mentioned. All three materials possess fast heterogeneous electron transfer rates, relative to bare glassy carbon electrodes. In addition, toxicity studies of these materials are conducted to gain insights on their possible harmful effects toward human health. The results of this study show siloxene nontoxic while germanane and methylgermanane impose dose‐dependent toxicity. Interestingly, methylation successfully reduce the toxicity of methylgermanane at lower concentrations. These studies provide fundamental insights into electrochemical and toxic properties of functionalized group 14 layered materials for future electrochemical applications.

Electrochemical determination of free chlorine on pseudo-graphite electrode

Pseudo-graphite from the University of Idaho Thermolyzed Asphalt Reaction also known as GUITAR is a new form of carbon. It shares morphological features with graphites, including basal and edge planes. Unlike graphites and other sp2-hybridized carbons, GUITAR has fast heterogeneous electron transfer across its basal planes and resistance to corrosion similar to boron-doped diamond electrodes. In this contribution GUITAR electrodes were examined as sensors for aqueous free chlorine (HOCl and OCl−) at pH 7.0 with cyclic voltammetric (CV) and chronoamperometric (CA) methods. Using CV at 50 mV s−1 GUITAR has a limit of detection of 1.0 μmol L−1, linear range of 0–5,000 μmol L−1, sensitivity of 215.8 μA L mmol−1 cm−2 and a signal stability of 4 days in constant exposure to 1 mmol L−1 free chlorine in pH 7.0, 0.1 mol L−1 phosphate buffer system. After 7 days of exposure GUITAR electrodes lost 37% of the former sensitivity, which was recovered by an in-situ regeneration procedure. The common aqueous ions, Ca2+, Na+, NO3-, SO42−, Cl−, CO32− and dissolved oxygen did not affect the response of the GUITAR-based sensor. The combination of limit of detection, linear range, sensitivity, sensor lifetime and its relative lack of interferences indicate that GUITAR is one of the best performers in free chlorine sensors.

The sp2-sp3 carbon hybridization content of nanocrystalline graphite from pyrolyzed vegetable oil, comparison of electrochemistry and physical properties with other carbon forms and allotropes

Nanocrystalline (nc) graphite produced from pyrolyzed vegetable oil has properties that deviate from typical graphites, but is similar to the previously reported Graphite from the University of Idaho Thermolyzed Asphalt Reaction (GUITAR). These properties include (i) fast heterogeneous electron transfer (HET) at its basal plane and (ii) corrosion resistance beyond graphitic materials. To discover the structural basis for these properties, characterization of this nc-graphite was investigated with Raman and X-ray photoelectron spectroscopies, nano-indentation, density, X-ray diffraction (XRD), thermogravimetric and elemental analyses. The results indicate that this nc-graphite is in Stage-2 of Ferrari's amorphization trajectory between amorphous carbon (a-C) and graphite with a sp2/sp3 carbon ratio of 85/15. The nano-crystallites size of 1.5 nm from XRD is consistent with fast HET rates as this increases the density of electronic states at the Fermi-level. However, d-spacing from XRD is 0.350 nm vs. 0.335 for graphite. This wider distance does not explain its corrosion resistance. Literature trends suggest that increasing sp2 content in a-C's increase both HET and corrosion rates. While nc-graphite's HET rate follows this trend, it exhibits higher than predicted corrosion resistance. In general, this form of nc-graphite matches the best examples of boron-doped diamond in HET and corrosion rates.

Sensitive detection and determination of benzodiazepines using silver nanoparticles-N-GQDs ink modified electrode: A new platform for modern pharmaceutical analysis

In this work, a unique conductive nano-ink based on silver nanoparticle‑nitrogen doped graphene quantum dots (Ag/N-GQD) was synthesized and utilized for development of a novel, unique and sensitive biosensor for determination of alprazolam, chlordiazepoxide bis, diazepam, oxazepam and clonazepam. Electrochemical deposition, as a well-controlled synthesis procedure, has been utilized for subsequently layer-by-layer preparation of Ag/N-GQD nano-ink on a chitosan (CS) electropolymerized on the surface of gold electrode using cyclic voltammetry techniques in the regime of −1 to +1 V. The modified electrode appeared as an efficient electroactive interface for detection of selected benzodiazepines by using cyclic voltammetry, differential pulse voltammetry, and square wave voltammetry. The prepared sensor showed a noticeably good electro-activity for electrooxidation of alprazolam, chlordiazepoxide bis, diazepam, oxazepam and clonazepam than bare CS and Ag/N-GQD modified electrodes. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between unique features of CS such as high permeability, excellent film-forming capability, good adhesion, cheapness, nontoxicity, and a susceptibility to chemical modifications, Ag/N-GQD nano-ink as high electrical conductivity. Finally, application of the new sensor for determination of selected benzodiazepine group drugs in unprocessed human plasma samples was studied. In general, the simultaneous attachment of Ag/N-GQD nano-ink to structure of CS provides new opportunities toward biomedical analysis and the personal healthcare.

Sensitive monitoring of taurine biomarker in unprocessed human plasma samples using a novel nanocomposite based on poly(aspartic acid) functionalized by graphene quantum dots.

The rapid and accurate determination of the level of taurine biomarker in various tissues and body fluids can be of great interest in the early diagnosis of several important pathologies and diseases. For the first time, this study reports on the electropolymerization of a low toxic and biocompatible nanocomposite "poly(aspartic acid)-graphene quantum dots (GQDs)" as a novel strategy for surface modification of glassy carbon electrode and preparation a new interface for measurement of taurine. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs nanostructures on poly(aspartic acid) using cyclic voltammetry techniques in the regime of -1.5 to 2V. The field emission scanning electron microscopy indicated immobilization of uniformly GQDs onto poly(aspartic acid) film. The modified electrode appeared as an effective electroactivity for detection of taurine biomarker using cyclic voltammetry, chronoamperometry, and differential pulse voltammetry. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of poly(aspartic acid) as semiconducting polymer, GQDs as high density of edge plane sites, and subtle electronic characteristics to chemical modification. Under the optimized analysis conditions, the prepared sensor for detection of taurine showed a low limit of quantification 0.001mM. Finally, the resulting prepared sensor allow the quantification of these biomarkers directly in biological samples without need of derivatization schemes or sample pretreatment.

Electrochemical monitoring of malondialdehyde biomarker in biological samples via electropolymerized amino acid/chitosan nanocomposite.

This study reports on the electropolymerization of a low toxic and biocompatible nanopolymer with entitle poly arginine-graphene quantum dots-chitosan (PARG-GQDs-CS) as a novel strategy for surface modification of glassy carbon surface and preparation of a new interface for measurement of malondialdehyde (MDA) in exhaled breath condensate. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of GQDs-CS nanostructures on a PARG prepolymerized on the surface of glassy carbon electrode using cyclic voltammetry techniques in the regime of -1.5 to 2V. The modified electrode appeared as an effective electroactivity for detection of MDA by using cyclic voltammetry, linear sweep voltammetry, and differential pulse voltammetry. The prepared modified electrode demonstrated a noticeably good activity for electrooxidation of MDA than PARG. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of PARG and semiconducting polymer, GQDs as high density of edge plane sites and subtle electronic characteristics and unique properties of CS such as excellent film-forming ability, high permeability, good adhesion, nontoxicity, cheapness, and a susceptibility to chemical modification. The prepared sensor showed 1 oxidation processes for MDA at potentials about 1V with a low limit of quantification 5.94nM. Finally, application of new sensor for determination of MDA in exhaled breath condensate was suited. In general, the simultaneous attachment of GQDs and CS to structure of poly amino acids provides new opportunities within the personal healthcare.

1T-Phase Transition Metal Dichalcogenides (MoS2, MoSe2, WS2, and WSe2) with Fast Heterogeneous Electron Transfer: Application on Second-Generation Enzyme-Based Biosensor.

Two-dimensional transition metal dichalcogenides (TMDs) have been in the spotlight for their intriguing properties, including a tunable band gap and fast heterogeneous electron-transfer (HET) rate. Understandably, they are especially attractive in the field of electrochemical biosensors. In this article, HET capabilities of various TMDs (MoS2, MoSe2, WS2, and WSe2) within group VI chemically exfoliated via t-BuLi intercalation are studied and these capabilities are used in the second generation electrochemical glucose biosensor. Strikingly, tungsten dichalcogenides (WS2 and WSe2) exhibit superior HET properties compared to that of their molybdenum counterparts (MoS2 and MoSe2). When incorporated into second generation glucose biosensors, WS2 and WSe2 generated a higher electrochemical responses than that of MoS2 and MoSe2, following the same trend as expected. The commendable performance by WX2 is attributed to the dominance of 1T phase, revealed by characterization data. The developed and optimized 1T WX2-based biosensor achieved analytical requirements of selectivity, wide linear ranges, as well as low limits of detection and quantification. The outstanding electrochemical performances of WS2 and WSe2 are to be recognized, adding on to the fact that they are not decorated with any metal nanoparticles. This is imperative to showcase the real potential of two-dimensional TMDs in electrochemical biosensors.

Electrochemical quantification of some water soluble vitamins in commercial multi-vitamin using poly-amino acid caped by graphene quantum dots nanocomposite as dual signal amplification elements

Rapid analyses of some water soluble vitamins (Vitamin B2, B9, and C) in commercial multi vitamins could be routinely performed in analytical laboratories. This study reports on the electropolymerization of a low toxic and biocompatible polymer “poly aspartic acid-graphene quantum dots” as a novel strategy for surface modification of glassy carbon electrode and preparation a new interface for measurement of selected vitamins in commercial multi vitamins. Electrochemical deposition, as a well-controlled synthesis procedure, has been used for subsequently layer-by-layer preparation of graphene quantum dots nanostructures on a poly aspartic acid using cyclic voltammetry techniques in the regime of −1.5 to 2 V. The field emission scanning electron microscopy indicated immobilization of graphene quantum dots onto poly aspartic acid film. The modified electrode possessed as an effective electroactivity for detection of water soluble vitamins by using cyclic voltammetry, chronoamperometry and differential pulse voltammetry. Enhancement of peak currents is ascribed to the fast heterogeneous electron transfer kinetics that arise from the synergistic coupling between the excellent properties of poly aspartic acid as semiconducting polymer, graphene quantum dots as high density of edge plane sites and chemical modification. Under the optimized analysis conditions, the prepared sensor for detection of VB2, VB9, and VC showed a low limit of quantification 0.22, 0.1, 0.1 μM, respectively.