Edge Plane Research Articles

Ionophore-Based SERS Sensing for Electrolyte Cations.

We present here a surface-enhanced Raman spectroscopy (SERS)-based platform for selectively detecting electrolyte cations. This platform facilitates the reorientation of the chromoionophore I (CHI) molecule positioned on the surface of silver nanoparticles, regulated by the targeted electrolyte cation within the ionophore-based ion-selective sensing framework. When exposed to the target ions, leading to deprotonation, the aromatic plane of the CHI molecule shifts from an endwise to an edgewise configuration on the SERS substrate surface. This reorientation improves the coupling of the induced dipole within the molecule and the induced electromagnetic field normal to the surface, leading to a heightened and more discernible SERS signal. Additionally, NMR data revealed a protonation-dependent conformational change in the CHI molecules. Upon protonation, the side chain of the CHI molecule extends away from its aromatic ring, whereas upon deprotonation, the carbon chain folds back and closely approaches the edge of the aromatic plane, further confirming this conclusion. Using Ca2+ and Na+ as examples, this method shows a detection limit of 0.1 μM for Ca2+ and 1 μM for Na+ with high selectivity. The successful application of the versatile and rapidly advancing SERS technique for electrolyte cation detection shows a promising pathway for enhancing current ion detection capabilities. As a preliminary demonstration, the total Ca2+ concentration in undiluted human serum was successfully determined, with common matrix interference effectively circumvented.

Supercapacitor electrodes based on Ru/RuO2 decorated on N,S-doped few-layer graphene

Innovatively designed flexible and high-performance shape memory polymer supercapacitors are promising next-generation energy storage devices for portable and wearable electronics. Therefore, thermally induced smart shape memory polymer polyurethane was synthesized using polycaprolactone/poly(ethylene glycol)/hexamethylene diisocyanate (PCL/PEG/HDI) in which the incorporation of PEG successfully assisted in lowering the transition temperature. The resulting polymer exhibits a remarkable transition temperature of 50 °C and a shape recovery ratio of 100 % at a strain of 300 %. The smart polymer was coated with a silver paste to ease the electron flow followed by coating with the electrode. Hybrid electrode materials are prepared in two stages. Initially, a few layers of holey-graphene were synthesized, where BET surface area reveals the presence of pores that are tuned by isothermal treatments in O2-atmosphere. Subsequently, active hybrid electrode materials nanostructured Ru/RuO2 decorated N, S-doped few layers of holey graphene were synthesized using hydrothermal methods. Here, nitrogen and sulfur doping in the basal or edge plane served as catalysts and metal coordination sites, facilitating the uniform distribution of ruthenium nanoparticles on the graphene. It is further confirmed by the density function theory (DFT) calculation using the adsorption energy. The optimized hybrid electrode material demonstrates a specific capacitance of 1297 mFcm−2 at a current density of 2 mAcm−2. A flexible-shape memory polymer supercapacitor exhibits a notable device-specific capacitance of 189 mFcm−2 at a current density of 1 mAcm−2, a high energy density of 45 µWhcm−2 at a power density of 0.25 mWcm−2, with 81 % of specific capacitance retention after eight shape programming and recovery cycle. Excellent shape recoverability and robust electrochemical performance make the as-fabricated symmetric supercapacitors a promising candidate for integration in flexible electronic applications.

The anisotropy of molybdenite planes: Analysis based on the adsorption behaviors of reagent and H2O

Multiple planes with different properties are exposed after the comminution of molybdenite because of the anisotropy of molybdenite. Study on the properties of different planes is of great significance to enhance the comprehensive utilization of molybdenite, especially in flotation. In order to explore the properties of different planes, the two main planes of molybdenite (basal plane and edge plane) are respectively taken as the research object in this paper, and the properties of planes are expressed using DFT through the adsorption behaviors of a new reagent named DTC-CTS and water molecules. The results show that edge plane has higher activity than basal plane. This is because there are exposed molybdenum atoms on the edge plane, and the sulfur atoms in DTC-CTS and oxygen atoms in water molecules are easy to react with the exposed molybdenum atoms. While the activity of basal plane is low because of the hinderance effect of sulfur atoms in the skin layer. The different adsorption behaviors of water molecules on molybdenite planes verified the hydrophobicity of different planes. In addition, the results also show that the water can affect the DTC-CTS adsorption on edge plane. Water can enhance interaction between single-bond sulfur atom and molybdenum atom, and weaken the interaction between double-bond sulfur atom and molybdenum atom on edge plane.

Transition-metal atoms embedded MoTe2 single-atom catalyst for efficient electrocatalytic hydrogen evolution reaction

As an attractive catalyst for the electrochemical hydrogen evolution reaction(HER), MoTe2 has attracted great interest. However, scarce catalytic sites and unsatisfactory catalytic activity of pristine MoTe2 basal plane impeded its practical application. The incorporation of single metal atom into 2D-substrate have been demonstrated as an effective strategy to tune HER activity of materials. Herein, we systematically investigated a series of transition-metal atoms(Fe, Co, Ni, Cu, Ru, Rh, Pd and Ag) embedded MoTe2 plane and edge single-atom catalysts(SAC, TM-MoTe2) for HER performance by employing density functional theory calculations. All TM-MoTe2 catalysts exhibit good thermodynamically and electrochemical stability. Compared with pristine MoTe2, HER catalytic activity of TM-MoTe2 are significantly enhanced due to effective modulation of charge transfer on embedded metal, which attribute to synergy interaction between embedded TM and surrounding Mo atoms. Specially, 2 candidate catalysts with Ru-MoTe2 plane and Fe-MoTe2 edge are found to show higher HER catalytic performance with low overpotential of only 10 mV and 60 mV, respectively. Furthermore, we found a key descriptor Δdd′ to well predict HER-activity trend of MoTe2-based material, which is closely correlated with H adsorption energy(ΔEH). This work provides in-depth theoretical insights for understanding active sites and designing high-efficiency MoTe2-based HER catalysts.

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Microfluidic Shape Analysis of Non-spherical Graphite for Li-Ion Batteries via Viscoelastic Particle Focusing.

The size and shape of graphite, which is a popular active anode material for lithium-ion batteries (LIBs), significantly affect the electrochemical performance of LIBs and the rheological properties of the electrode slurries used in battery manufacturing. However, the accurate characterization of its size and shape remains challenging. In this study, the edge plane of graphite in a cross-slot microchannel via viscoelastic particle focusing is characterized. It is reported that the graphite particles are aligned in a direction that shows the edge plane by a planar extensional flow field at the stagnation point of the cross-slot region. Accurate quantification of the edge size and shape for both spheroidized natural and ball-milled graphite is achieved when aligned in this manner. Ball-milled graphite has a smaller circularity and higher aspect ratio than natural graphite, indicating a more plate-like shape. The effects of these differences in graphite shape and size on the rheological properties of the electrode slurry, the structure of the coated electrodes, and electrochemical performance are investigated. This method can contribute to the quality control of graphite for the mass production of LIBs and enhance the electrochemical performance of LIBs.

Engineering a vanadium-incorporated MoS2-based mixed metal dichalcogenide system for improved supercapacitor performance

In this study, we developed a mixed metal dichalcogenide system of molybdenum‑vanadium disulfide with the chemical formula Mo1-xVxS2, where x = 0.3, 0.5, and 0.7, corresponding to Mo:V ratios of 70:30, 50:50, and 30:70 using a facile one-pot hydrothermal method. This mixed metal structure is expected to influence both the basal plane and the edge plane towards engineering the active sites in the resulting system forming xMon+-yV4+-zS2− network, which is a crucial for its improved electrochemical performance. Structural studies confirmed the emergence of structural distortion in the system due to the difference in the ionic sizes of Mo and V ions, leading to strain in the lattices. Furthermore, electron microscopic analysis revealed the formation of aggregated nano-petals for bare MoS2, while these petals self-assembled to form flower-like microspheres upon the introduction of V in the mixed metal (Mo1-xVxS2) systems. Consequently, the Mo0.5V0.5S2 delivered a specific capacitance of 492.2 F g−1 at 1 A g−1 with substantial capacitance retention of 94 % up to 3000 cycles, which is twofold higher compared to bare MoS2. Moreover, the fabricated symmetric device achieved an energy density of 19.5 Wh kg−1 and a maximum power density of 9000 W kg−1 with capacitance retention of 92.8 and 86.3 % after 5000 and 10,000 charge/discharge cycles, respectively.

Hybrid graphene nanoflakes for electrochemical sensing with multianalyte detection capability

This work illustrates the production of highly electrochemically active graphene by liquid phase exfoliation technique for ultrasensitive electrochemical sensors. An airless high-pressure spray technique was designed to exfoliate bulk natural graphite into nm-scaled flakes (referred as HP50). Transmission electron microscopy, Raman and X-ray photoelectron spectroscopy studies reveal that the HP50 sample has a mixed structure composed of amorphous carbon and a few-layer graphene fraction with high amount of edge plane defects. The HP50 flakes are drop cast on glassy carbon electrodes to test the simultaneous and selective electrochemical detection of hydrogen peroxide, ascorbic acid, and dopamine. In cyclic voltammetry measurements, hydrogen peroxide reduces at −0.2 V vs Ag/AgCl (1 M), while ascorbic acid and dopamine oxidize at 0.1 V vs Ag/AgCl (1 M) and 0.3 V vs Ag/AgCl (1 M), respectively. Linear sweep voltammetry demonstrates high sensitivity (164, 739, and 3357 μA mM−1 cm−2) and low limit of detection (15, 1.7, and 2.1 μM) for the three analytes, respectively. Interference studies confirm a high sensitivity and selectivity towards the different chemical species. The HP50-based multianalyte sensors are also tested against different environmental and commercial samples, illustrating their viability in practical applications.

Cobalt-catalyzed carbonization from polyacrylonitrile for preparing nitrogen-containing ordered mesoporous carbon CMK-1 electrode with high electric double-layer capacitance

Ordered mesoporous carbon CMK-1 was prepared via carbonization at a relatively low temperature (the first step) followed by partial graphitization (the second step of carbonization at higher temperature) inside the ordered mesopores of cobalt-loaded mesoporous silica MCM-48 using polyacrylonitrile (PAN) as a carbon/nitrogen source. This first step of the carbonization is called “infusibilization”, and the resultant material is denoted as PANinf. In an advanced temperature-programmed desorption analysis of the PANinf/MCM-48 composite, the temperature of the observed HCN signal indicated that carbonization was reduced from 550 to 450 °C by a Co catalyst. The amount of typical N2 formation associated with the selective removal of pyridinic N species, resulting in the graphitic surface formation, also increased at a relatively high temperature (approximately 1000 °C) with the aid of the Co catalyst. The CMK-1 prepared through cobalt-catalyzed carbonization exhibited a higher electric double-layer capacitance with an Et4N+BF4–/propylene carbonate electrolyte, and higher electrical conductivity than CMK-1 prepared without a catalyst. This also implied the progress of graphitization within the carbonaceous wall. These results suggest that the edge planes of the graphitic domains in CMK-1 are predominantly exposed on the surfaces of the carbonaceous walls, resulting in an increase in the number of adsorptive sites for the electrolyte during capacitance measurements.

Elucidating the impact of non-spherical morphology on kinetic behavior of graphite using single-particle microelectrode

The precise assessment of the kinetic properties of graphite is crucial for the design of the material and the development of electrochemical models for lithium-ion batteries. However, conventional evaluation methods using composite electrodes fall short in excluding the influence of its porous structure and evaluating the influence of particle shape on kinetic behavior. In this work, we elucidate the impact of non-spherical morphology on kinetic behavior of single artificial graphite particle, employing the single-particle microelectrode technique. Three single artificial graphite particles with different sizes are pre-cycled and exhibit outstanding rate capability, maintaining a maximum capacity retention of 78.1 % at 200 C. Further, exchange current density and diffusion coefficients are determined through Tafel plots and the potentiostatic intermittent titration technique (PITT), respectively. It is found that the particle with a higher exposure of edge planes present elevated exchange current density and diffusion coefficients. Considering that the graphite particles typically feature an ellipsoidal rather than spherical shape, we propose an approach based on an ellipsoidal diffusion model for extracting diffusion coefficients. This model takes into account the non-spherical morphology of graphite, addressing the limitations inherent in the geometric assumptions of previous methods. The average relative error between the diffusion coefficients derived from the ellipsoidal diffusion model and the previous method using spherical assumptions is 215 %, indicating that accurately depicting the shape of ellipsoidal graphite particles in the model is crucial for obtaining correct estimates of kinetic parameters. This study offers direct experimental evidence of superior kinetic behavior of edge planes over basal planes. To leverage this characteristic, it is recommended to employ an out-of-plane aligned architecture for composite electrodes using novel techniques, e.g., 3D printing or magnetic alignment techniques.

Laser-Induced Graphene for Electrochemical Analysis of Food and Agricultural Contaminants

Carbon-nanomaterial sensors offer promising routes toward low-cost, high-throughput electrochemical sensors. Carbon nanomaterials, such as graphene and carbon nanotube (CNT), have been studied with various fabrication methods to produce sensors, including high-quality thin film graphene and CNT by chemical vapor deposition. However, the complexity and cost associated with their fabrication have hindered their implementation into single-use test strip sensors. Even high-yield mechanical and/or chemical exfoliation of graphene from graphite followed by solution phase printing of electrodes can be costly due to the complexity of ink formulation and the need for post-print annealing requirements. However, laser-induced graphene (LIG) avoids the need to exfoliate graphene from graphite or to create a solution-phase graphene ink by converting sp3 carbon found in carbon-rich substrates into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. The resulting LIG also exhibits a high surface area and is porous with a high density of edge plane sites, which are beneficial for biofunctionalization and heterogeneous charge transport during electrochemical sensing. Furthermore, we have demonstrated that the surface area and wettability of the LIG can be tuned to greatly improve the sensitivity of electrochemical enzymatic biosensors (detection limits down to the picomolar range) and reduce the water layer buildup between the ion-selective membrane and the electrode, which improves the accuracy of the sensor readings. The fabricated LIG electrodes have been used in a wide variety of electrochemical sensing applications, including in food safety (foodborne pathogens and other contaminants), environmental monitoring (agrochemicals), and health monitoring sensors (salivary potassium and lactate, and urinary potassium and ammonium). Different electroanalytical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. We demonstrate how the ISE (ion-selective electrodes) can be functionalized with PVC-based ion-selective membranes for potassium, nitrate, nitrite, ammonium, sodium, and pH in various biological solutions, including soil and water for nutrient/fertilizer monitoring in farm fields. Additionally, we demonstrate how the hydrophilic LIG graphene can be used to create other highly sensitive electrochemical biosensors including enzymatic pesticide biosensors and Salmonella spp. immunosensors. All these electroanalytical sensors were validated in real-world samples and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Results demonstrate the utility of LIG-based sensors for rapid and sensitive electrochemical measurement of contaminants as a readily modified platform for scalable production of electroanalytical devices applied toward point-of-service environmental and food monitoring.

Relocation of the 2018–2022 seismic sequences at the Central Gulf of Corinth: New evidence for north-dipping, low angle faulting

The Gulf of Corinth, Central Greece, is a highly active half-graben, characterized by seismicity which is more intense in its western part, while destructive earthquakes have also occurred towards its eastern end. We herein present an analysis of the seismicity in the Central Gulf of Corinth, for the period from June 2018 to December 2022. We applied the EQTransformer machine-learning model to enhance the initially available data, adding missing P- and S-wave arrival-times or improving existing ones. The events were initially located using a new local velocity model and then relocated using the double-difference method, including waveform cross-correlation data from local stations. The hypocenters, generally distributed at depths between 5 and 15 km, along with the focal mechanisms of significant earthquakes (1965 through 2022) and the geometry of mapped faults on the surface were co-examined to better understand their possible connection. It is shown that major outcropping north-dipping structures, such as the East Helike fault and its eastward offshore extension, match only with the southern bounds of seismicity. The Mw = 5.9, 1970 Antikira and Mw = 5.7, 1992 Galaxidi earthquakes cannot be associated with known mapped faults on the surface and likely occurred on low-angle, north-dipping planes. The variability in slip behavior of the low-angle detachment in the Gulf of Corinth, ranging from seismic slip to aseismic creep, probably accounts for the most part of the N-S extensional deformation. The spatial pattern of the 2018–2022 microseismicity delineates the edges of the rupture planes of major events that occurred during the instrumental era, including the Mw = 6.3, 1995 Aigion earthquake. The lack of aftershocks for significant earthquakes, including the Mw = 5.0, 8 October 2022 event, south of Desfina, is interpreted in terms of different pore pressure conditions, variations in fault-rock strength, and the preferred accumulation of high stress inside the upper crust.

A DFT study of superior adsorbate–surface bonding at Pt-WSe2 vertically aligned heterostructures upon NO2, SO2, CO2, and H2 interactions

This study investigates the potential of platinum (Pt) decorated single-layer WSe2 (Pt-WSe2) monolayers as high-performance gas sensors for NO2, CO2, SO2, and H2 using first-principles calculations. We quantify the impact of Pt placement (basal plane vs. vertical edge) on WSe2’s electronic properties, focusing on changes in bandgap (ΔEg). Pt decoration significantly alters the bandgap, with vertical edge sites (TV-WSe2) exhibiting a drastic reduction (0.062 eV) compared to pristine WSe2 and basal plane decorated structures (TBH: 0.720 eV, TBM: 1.237 eV). This substantial ΔEg reduction in TV-WSe2 suggests a potential enhancement in sensor response. Furthermore, TV-WSe2 displays the strongest binding capacity for all target gases due to a Pt-induced “spillover effect” that elongates adsorbed molecules. Specifically, TV-WSe2 exhibits adsorption energies of − 0.5243 eV (NO2), − 0.5777 eV (CO2), − 0.8391 eV (SO2), and − 0.1261 eV (H2), indicating its enhanced sensitivity. Notably, H2 adsorption on TV-WSe2 shows the highest conductivity modulation, suggesting exceptional H2 sensing capabilities. These findings demonstrate that Pt decoration, particularly along WSe2 vertical edges, significantly enhances gas sensing performance. This paves the way for Pt-WSe2 monolayers as highly selective and sensitive gas sensors for various applications, including environmental monitoring, leak detection, and breath analysis.

Uncovering the hetero-hydrophobic attraction between the basal planes of molybdenite and talc under flotation conditions

The very close natural floatability of molybdenite and talc has been traditionally believed as the main reason for their separation problem. However, the interactions between the basal and edge planes of the two platy minerals remain unclear. Here the hydrophobic attraction between the basal planes was proposed as the dominating factor for that problem. Flotation tests in both single and mixed mineral systems were conducted using carboxymethyl cellulose (CMC) as talc depressant and sodium isobutyl xanthate (SIBX) as molybdenite collector. Zeta potential distribution, contact angle, in situ optical microscope observation, EDLVO calculation and surface energy analysis were applied to reveal the surfacial actions between the basal and edge planes of molybdenite and talc. Molybdenite and talc showed obvious floatability difference in single mineral system, however, their separation efficiency met with big decline in mixed mineral system. Zeta potential results demonstrated that, in the presence of CMC and SIBX, negatively charged particles of molybdenite and talc aggregated rather than electrostatically repulsed and dispersed. The contact angle and particle adhesion results showed a certain degree of selective attraction between the basal planes of molybdenite and talc. The EDLVO calculation suggested the attractive interactions were ranked as: Mb(basal)-Tlc(edge) > Mb(basal)-Tlc(basal) ≈ Mb(edge)-Tlc(edge) > Mb(edge)-Tlc(basal). The surface energy calculation pointed out that the fundamental reason for the separation problem was exactly the hetero-hydrophobic attraction between their basal planes.

Graded contractions of the [formula omitted]-grading on [formula omitted]

Graded contractions of the Z23-grading on the complex exceptional Lie algebra g2 are classified up to equivalence and up to strong equivalence. The non-toral fine Z23-grading is highly symmetric, with all the homogeneous components Cartan subalgebras. This makes possible a combinatorial treatment based on certain nice subsets of the set of 21 edges of the Fano plane. There are 24 such nice sets up to collineation. Each of these is the support of an admissible graded contraction, one of which is present in every equivalence class of graded contractions. Each nice set gives rise to a single Lie algebra, except for three of the cases in which families depending on one or two parameters are found. In particular, a large family of 14-dimensional Lie algebras arise, most of which are solvable. The properties of each of these Lie algebras are studied.

Comparing thermoplastic electrode materials: Toward enhanced sensing of O2 and H2O2 in flow devices

AbstractCarbon composite electrodes often suffer from poor electrocatalytic activity and require complex, expensive, or time‐consuming modifications to effectively detect certain analytes such as O2 and H2O2. Thermoplastic electrodes (TPEs) are a new class of composite electrodes, fabricated by mixing commercial graphite with a thermopolymer, that exhibit superior electrochemical properties to typical carbon composite electrodes. This work investigates the properties of TPEs using two thermopolymer binders – polycaprolactone (PCL) and polystyrene (PS) – with sanded and heat‐pressed surface treatments. XPS and SEM analysis suggested that sanded TPEs have a higher density of graphitic edge planes and improved electrochemistry as a result. Electrochemical detection of O2 and H2O2 was demonstrated on sanded PS TPEs. Additionally, this work introduces the first use of a 3D‐printed TPE template as part of a 3D‐printed sensor module that is reversibly sealed with magnets as a proof‐of‐concept flow‐based sensor for detecting H2O2.

High-efficient acetylene synthesis by selective electrochemical formation of CO2-derived CaC2

Acetylene can be used as feedstock for various chemical products, but its raw material has been a fossil fuel, which poses an environmental challenge. One way to address the challenge is to form CaC2 from CO2, which reacts with water to form acetylene. This study demonstrated the selective formation of CaC2 from CO2 by an electrochemical process in NaCl-KCl-CaCl2-CaO melt at 823 K to produce C2H2 with high current efficiency. The CaC2 was formed through two reactions: the carbon electrodeposition from CO2-derived CO32− (Step 1) and the electrochemical reduction of Ca(II) ion on the carbon (Step 2). These two reactions could be controlled by conducting potentiostatic electrolysis under CO2 and Ar atmospheres, resulting in acetylene synthesis with a maximum current efficiency of 92 %. Each electrochemical reaction agreed with the thermodynamic electrode potential. The electrolysis on carbon electrodes revealed that the higher the crystallinity of carbon, the more selectively CaC2 was formed. The CaC2 formation was induced by the reduction of Ca(II) ions on the basal plane of the graphite layer rather than the edge plane. The unique interfacial phenomenon between high-temperature melt and a carbon electrode surface will contribute to realizing a highly efficient CO2 conversion process to acetylene.

Defective graphene-nanomaterials derived from banana-biomass for simultaneous electrochemical detection of xanthine, hypoxanthine, and uric acid: Insights from scanning electrochemical microscopy on edge and basal planes

While graphene and other graphene-based materials are promising for electrochemical sensors, developing a simple synthesis method and understanding how their structure affects their performance remains challenging. This study introduces a straightforward method to produce highly defective graphene-based nanomaterials (BP-GNMs) from banana pulp (BP) biomass. These BP-GNMs are suitable for efficiently detecting purine bases (xanthine (X), hypoxanthine (Hx), and uric acid (UA)) simultaneously using electrochemical techniques. The synthesis process involves heating at 180 °C in air. Compared to BP-derived graphene quantum dots (BP-GQDs) made using a hydrothermal method, BP-GNMs exhibit significantly better electrochemical activity. This is shown by well-defined, separated peaks with high currents in electrochemical measurements of the purine bases. In this study, we compared the physicochemical properties of BP-GNMs and BP-GQDs using various techniques like FESEM, TEM, XPS, UV–Vis, Raman, and FTIR spectroscopy. Our analysis revealed the formation of layered nanomaterials based on graphene, with sizes ranging from 400 mm to 10 μm. These nanomaterials exhibited a balanced ratio of sp2-bonded carbon (sp2C) to sp3-bonded carbon (sp3C). This balanced ratio is attributed to the presence of both defective basal planes (containing sp2C) and edge planes (containing sp3C) on the BP-GNMs. The heterogeneity on the surface in terms of edge and basal planes of the materials was viewed using scanning electrochemical microscopy (SECM) technique with ferrocene-carboxylic acid as a redox probe. As a practical application of this low-cost biomass material, an efficient and separation-free simultaneous electrochemical sensing of X, Hx and UA in various fishes and human urine samples were demonstrated with a recovery of 100±2%.

Surface-Roughened Graphene Oxide Microfibers Enhance Electrochemical Reversibility.

Here, we provide an optimized method for fabricating surface-roughened graphene oxide disk microelectrodes (GFMEs) with enhanced defect density to generate a more suitable electrode surface for dopamine detection with fast-scan cyclic voltammetry (FSCV). FSCV detection, which is often influenced by adsorption-based surface interactions, is commonly impacted by the chemical and geometric structure of the electrode's surface, and graphene oxide is a tunable carbon-based nanomaterial capable of enhancing these two key characteristics. Synthesized GFMEs possess exquisite electronic and mechanical properties. We have optimized an applied inert argon (Ar) plasma treatment to increase defect density, with minimal changes in chemical functionality, for enhanced surface crevices to momentarily trap dopamine during detection. Optimal Ar plasma treatment (100 sccm, 60 s, 100 W) generates crevice depths of 33.4 ± 2.3 nm with high edge plane character enhancing dopamine interfacial interactions. Increases in GFME surface roughness improve electron transfer rates and limit diffusional rates out of the crevices to create nearly reversible dopamine electrochemical redox interactions. The utility of surface-roughened disk GFMEs provides comparable detection sensitivities to traditional cylindrical carbon fiber microelectrodes while improving temporal resolution ten-fold with amplified oxidation current due to dopamine cyclization. Overall, surface-roughened GFMEs enable improved adsorption interactions, momentary trapping, and current amplification, expanding the utility of GO microelectrodes for FSCV detection.

Label-free voltammetric screening of human blood serum

The current study presents a comprehensive voltammetric investigation into the direct analysis of untreated human blood serum in a phosphate buffer at an unmodified, graphite electrode by means of voltammetry. By employing advanced square-wave voltammetry at an edge plane pyrolytic graphite electrode (EPPGE), the basic principles were established for developing a sensitive, fast, simple, and label-free method for the simultaneous screening of uric acid, bilirubin, and albumin analytes that are present in human blood serum and are quite essential for rapid medical diagnostics. The electrochemical protocol utilizes the specific structural patterns of the EPPGE, the inherent redox and adsorption properties of the analysed analytes, and the sensitivity and rapidity of the employed advanced voltammetric technique. The methodology has been successfully applied for quantification of the considered analytes in a series of samples of human blood serum and was compared with the standard methods used in a clinical biochemical laboratory. This novel method represents a significant advancement towards the development of point-of-care devices aimed at swiftly and simultaneously quantifying uric acid, bilirubin, and albumin levels in human serum.