Surface Of Graphite Particles Research Articles

Leaching kinetics of ash impurities from aphanitic graphite by combining dual-ultrasound and hydrochloric acid–potassium hydrogen fluoride

The hydrochloric acid-fluoride salt is useful for purifying graphite. Ultrasonic-assisted technique can significantly reduce the leaching time and improve the leaching efficiency. Compared with single-frequency, dual-frequency ultrasound has the advantages of high energy efficiency and wide cavitation area. In this study, the combination of a dual-frequency ultrasound-assisted technique and hydrochloric acid–potassium hydrogen fluoride leaching agent was proposed for the leaching of aphanitic graphite to remove impurity minerals. First, the effects of probe-type ultrasonic power, tank-type ultrasonic power, temperature, HCl concentration, ultrasonication time, and KHF2 concentration on the purification efficiency of impurities from aphanitic graphite with the assistance of dual-frequency ultrasound were investigated. It was found that the combination of dual-frequency ultrasound and hydrochloric acid–potassium hydrogen fluoride can reduce the ash content of aphanitic graphite from 13.02 % to 1.02 % with an ash removal rate of 94.17 %. Second, volumetric reaction models and unreacted shrinkage nucleation models were used to fit the kinetics of impurities from aphanitic graphite with dual-frequency ultrasound-assisted HCl-KHF2 leaching. Kinetic analysis shows that the volumetric reaction model with chemical control was better to fit the leaching process. This is consistent with the calculation results of the activation energy of the reaction (Ea = 58.13 kJ/mol). Finally, laser particle size analyzer, X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDS) were used to analyze the fugacity of impurity minerals during the process of dual-frequency ultrasound-assisted HCl-KHF2 leaching. It was revealed that combining ultrasonic cavitation fragmentation with chloric acid–potassium fluoride generated SiF4 with high solubility, thereby removing silica-bearing impurities more efficiently. The challenges in further reducing ash content from 1.02 % in the leached concentrate of aphanitic graphite could be attributed to the existence of titanium-bearing mineral impurities on the surface of graphite particles and the presence of silica-bearing minerals between graphite carbon layers.

A Flexible Sensor for Vancomycin Fabricated By Depositing Molecularly Imprinted Carbon Paste on a Wire

1. Introduction Vancomycin (VCM), an antibacterial drug, has a narrow effective blood concentration range, requiring therapeutic drug monitoring (TDM) to measure blood levels and optimize dosing regimens . Neonates, in particular, have large individual differences in the rate of drug metabolism, so strict TDM is necessary, but the dilemma is that the amount of blood drawn must be kept to a minimum. Therefore, we decided to develop a method of TDM without blood sampling by implanting a sensor that detects VCM under the skin. The sensor must be flexible enough not to damage the subcutaneous tissue. We have developed a sensor using a MIP carbon paste (MIP-CP) electrode, in which graphite particles with molecularly imprinted polymers are mixed with oil. Since higher mechanical strength is required for indwelling sensors, we fabricated MIP-carbon dough (MIP-CD) electrodes by mixing MIP with a thermosetting silicon resin prepolymer and thermosetting it. This was applied to a wire to develop a flexible wire-type sensor, and its performance was evaluated. 2. 2. experimental method 2-1. MIP graft polymerization /MIP-CD fabricationMethacrylic acid, ethylene glycol dimethacrylate, and allylamine carboxypropionic-3-ferrocene were graft copolymerized on the surface of graphite particles with fixed polymerization initiator in the presence of template VCM. Then, after washing and drying with sodium chloride solution and distilled water, the uncured MIP-CD was mixed with thermosetting silicone resin at a weight ratio of 7:3. Non-imprinted polymer (NIP)-CD, which was prepared by the same procedure without adding a template during synthesis, was also prepared for comparison.2-2. Fabrication of MIP-CD sensor Carbon ink was applied to a 20 mm tip of a 50 mm tin-plated copper wire, and uncured MIP-CD was applied on top. Then, silicon resin was applied for insulation to limit the effective area of the MIP-CD electrode, and both the insulation and MIP-CD were heat-cured in a dryer to fabricate the wire electrode shown in Fig. 1.2-3. measurement methodDifferential pulse voltammetry was performed on the MIP (or NIP)-CD sensor in phosphate buffer containing VCM or teicoplanin (TEIC), which has a similar structure, and the relationship between current and concentration was plotted. 3. Results and Discussion A comparison of the sensitivity of MIP-CD and NIP-CD electrodes to VCM is shown in Fig. 2: the current at MIP-CD increased linearly with increasing VCM concentration, while that at NIP-CD was insensitive. This result indicates that the current at the MIP-CD electrode reflects the specific binding of VCM to the imprinted binding site. As shown in Fig. 3, the MIP-CD electrode was not sensitive to TEIC and showed high selectivity. Conclusion The electrode with MIP-CD fixed on a wire is strong and flexible, yet has a specific response to VCM, and is expected to be used as an indwelling subcutaneous sensor.*This work was supported by the Bridging Research Program of the Japan Agency for Medical Research and Development (Keio University Center). Figure 1

A Disposable Sensor for Rapid Histamine Detection in Fish Using Molecularly Imprinted Carbon Paste Electrode

Introduction: Histamine (HM), a toxic compound, is produced due to an enzymatic reaction when histidine (HS)-rich red fish such as tunas and other fish and their processed products are improperly stored, e.g., leaving them at room temperature. With the increasing popularity of raw fish consumption, HM analysis is mandatory for these fish in various countries. However, the conventional immunoassay method is time-consuming, costly, and technically demanding, burdening wholesalers heavily.Molecularly Imprinted Polymers-based materials are attractive materials for sensor fabrication due to their high selectivity, stability, and ease of production. In this study, we attempted to develop a Molecularly Imprinted Polymer grafted Carbon Paste (MIP-CP) for histamine sensing. Experimental Methods First, a radical polymerization initiator was fixed on the surface of graphite particles [1]. Next, histamine dihydrochloride, itaconic acid, and ethylene glycol dimethacrylate (EDMA) were dissolved in a mixture of distilled water and dimethylformamide to prepare a polymerization solution. The polymerization solution and initiator-fixed graphite were placed in a quartz tube and irradiated with a xenon lamp for 1 hr. HM was extracted and removed using acetic acid. MIP-CP was prepared by mixing MIP-grafted graphite and silicon oil containing ferrocene in a 7:3 weight ratio. Non-imprinted polymer (NIP)-CP was also prepared using the same procedure, except that HM was not added.Differential pulse voltammetry (DPV) was performed with electrodes packed with the obtained MIP-CPs on a disposable chip [2]. The performance of the HM sensor was evaluated based on the relationship between the oxidation current of ferrocene and HM concentration. (Measurement range 0 μg/mL~100 μg/mL) Experimental results The dependence of the oxidation current density on HM concentration at the NIP and MIP electrodes was confirmed (0.0085 μA-mL/μg, R²=0.9357). The increase in current density with increasing HM concentration at the MIP-CP electrode was more than three times greater than at the NIP-CP electrode. This confirmed that MIP-CP exhibited current changes corresponding to the interaction between HM and HM-imprinted sites. Furthermore, the current increased linearly with increasing HM concentration from 0-100 µg/mL. This dynamic range includes 50 µg/mL, which is considered the lower limit of acceptable Hm concentration in fish meat.However, the current value was constant for HS concentration at 0.75 µA over the range of 40-100 µg/mL and below. Therefore, the sensor is saturated with HS at concentrations above 40 µg/mL, and histidine interference can be excluded by subtracting 0.75 µA from the current value obtained when measuring the fish meat sample. Conclusion We successfully developed a reagentless, disposable histamine sensor using MIP-CP, which provides a rapid, reliable, and cost-effective method for histamine detection in fish.

Improve the compatibility of sulfolane-graphite with the synergetic additives

The high voltage stability (> 5.5 V) makes sulfolane (SL) an excellent electrolyte solvent candidate for high specific energy lithium-ion batteries. However, the stable solid electrolyte interphase (SEI) cannot be generated on the surface of graphite particles with SL, limiting its application. To solve the interface incompatibility, we introduce fluoroethylene carbonate (FEC) and lithium nitrate (LiNO3) in SL-based electrolyte for constructing an inorganic-rich SEI on graphite. The comprehensive characterizations and simulations demonstrate that combined effect of additives facilitates the formation of additive-derived LiF-Li3N enhanced inorganic-rich SEI. The proposed electrolyte shows stable cycling performances with 324.89 mAh/g and 97.93 % after 50 cycles in Li/graphite half-cells, compared with the capacity of 24.54 mAh/g and the capacity retention of 19.4 % in SL-without additives. Importantly, the electrolyte system obtains a capacity retention of 71 % and the capacity of (127.93 mAh/g) is higher than that without additives (110.21 mAh/g) at 4.4 V after 200 cycles. This work solves the incompatibility of SL-graphite with low-cost additives, and is beneficial to realize the commercial application of sulfolane in high specific energy batteries.

Impact of graphite particle surface modification on the strengthening of cross-linked polyvinyl alcohol composites: A comprehensive investigation

To reduce the hydrophilicity of polyvinyl alcohol (PVA), various methods are employed. Acid cross-linking is one technique, but it decreases the polymer's strength. To address this, different reinforcements are utilized to enhance the polymer's strength while mitigating the side effects of acid cross-linking. The present research intends to improve the physical, mechanical, and thermal properties of PVA by cross-linking it with fumaric acid and reinforcing it with modified graphite particles. The particles were prepared through oxidative acidic treatment and added in different weight proportions (0.5, 1, 1.5, and 2 wt.%) to the PVA matrix. Water absorption (WA) tests were conducted to affirm the formation of cross-linked bonds, and Fourier transform-infrared spectroscopy was employed to confirm the oxidation of the graphite particles with acid. The composites were examined using scanning electron microscopy, which revealed a robust interfacial adhesion between the modified graphite and cross-linked PVA, resulting in better mechanical characteristics. The highest ultimate tensile strength was observed when using 1.5 wt.% of modified graphite particle reinforcement, resulting in a 31% increase in comparison to pure cross-linked PVA. Moreover, the thermal stability increased from 358°C (PVA alone) to 375°C (composite with 2 wt.% treated graphite particles). Dynamic mechanical analysis revealed an increase in glass transition temperature from 68.2°C to 72.9°C, and activation energy from 604.84 to 1028.21 kJ mol−1 (neat PVA to composite with 1.5 wt.% modified particles). The damping coefficient of the cross-linked composite was 0.257, making it suitable for acoustic damping applications like speakers.

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Roll-to-roll solvent-free manufactured electrodes for fast-charging batteries

Electrochemistry-Driven Interphase Doubly Protects Graphite Cathodes for Ultralong Life and Fast Charge of Dual-Ion Batteries.

Dual-ion batteries (DIBs) with graphite as cathode material, show superiority in terms of sustainability, affordability, and environmental impact over Li-ion batteries that rely on transition-metal based cathodes. However, graphite cathodes severely suffer from poor structural stability during anion storage at high potentials because of the co-intercalation and oxidative decomposition of electrolytes. This work presents an in situ electrochemistry-driven route to create a bifunctional interphase through implantation of diethylenetriaminepenta(methylene-phosphonic acid) (DTPMP) on the surface of graphite particles. The reaction mechanisms and functions of DTPMP are investigated both experimentally and theoretically. The DTPMP-derived interphase not only improves the antioxidative stability of electrolytes but also benefits the desolvation of PF6 - anions, which doubly protect the graphitic structure and give rise to fast-charge and ultralong cycling performance of graphite cathodes in DIBs.

A disposable edoxaban sensor chip using carbon paste electrode grafted with molecularly imprinted polymer.

Although direct oral anticoagulants (DOACs) are generally safe and TDM is not required, blood levels of the drug are important information for response decisions in emergency care. In this study, an attempt was made to develop a disposable sensor chip for the rapid detection of edoxaban in blood, a type of DOAC. Molecularly imprinted polymers with edoxaban tosilate as a template and sodium p-styrene sulfonate as a functional monomer were grafted onto the surface of graphite particles, mixed with silicon oil dissolved in ferrocene to form a paste, and filled onto a substrate made of plastic film. Sensor chips were fabricated. The current obtained from this sensor by voltammetry within 150s depended on the edoxaban concentration. Sensitivity to edoxaban was also confirmed in bovine whole blood. The potential of disposable sensors to rapidly detect edoxaban in whole blood was demonstrated in this study, although selectivity, reproducibility, and sensitivity need to be improved for practical use.

The feasibility for natural graphite to replace artificial graphite in organic electrolyte with different film-forming additives

The feasibility for natural graphite (NG) to replace artificial graphite (AG) in organic electrolytes with different additives are investigated. Although the strong film-forming additives contributes to form robust solid electrolyte interphase (SEI) film on graphite particle surface, great differences in gas evolution, lithium inventory loss and other side reactions are observed. Lithium bis(oxalato)borate (LiBOB) and Fluoroethylene carbonate (FEC) are found more effective and the combination shows to be more promising. In the optimized electrolyte, natural graphite anode exhibits excellent long-term cycling capability. After 800 cycles at high temperature, the capacity retention is comparable to that using artificial graphite. The mechanisms for the capacity-fading of the full cells with AG and NG anode are investigated by ICP, SEM and polarization studies. The results shows that NG electrode consumes more active lithium due to the rough surface and larger volume expansion. The rapid capacity-fading in the initial 100 cycles is related to the instability of the SEI film aroused from large volume expansion. The systematic analysis is inspiriting for the development of high performance lithium ion batteries with reduced cost.

Changes in the Mechanical Behavior of Electrically Aged Lithium-Ion Pouch Cells: In-Plane and Out-of-Plane Indentation Loads with Varying Testing Velocity and State of Charge

The knowledge about the influence of electrical aging on the behavior of lithium-ion cells under mechanical loads is of high importance to ensure a safe use of batteries over the lifetime in electric vehicles. In order to describe the mechanical behavior in relation to electrical aging, fresh and electrically aged NCM pouch cells were investigated under different mechanical crash loads. For the first time, the aged cells’ behavior under quasistatic lateral loading was taken into account. Aged cells showed lower maximum forces compared to the fresh cells. The reason of the changed mechanical cell behavior was explained with the different buckling behavior of fresh and aged cells by experimental images. Furthermore, quasistatic and dynamic crash tests in cell’s thickness direction were performed at varying state of charge (SOC) and compared to the results of a previously published study. Independently of the testing velocity, the electrically aged cells failed at increased deformation values. This observation was justified by an increased cell thickness due to an additional softer layer, formed on the aged graphite particle surface, which was observed by the means of scanning electron microscopy. Furthermore, the aged cells showed lower failure forces of up to −11% under quasistatic and dynamic loads at 0% SOC. It was also illustrated that electrical aging causes a deeper voltage drop after cell failure, which suggests a higher energy release after the internal short circuit. The investigations show that electrical aging has a significant influence on the mechanical properties of lithium-ion cells and must be taken into account in the safety assessment.

(Digital Presentation) A Disposable Chip Sensor for the Detection of Vancomycin: Studying the Long-Term Stability

Vancomycin is one of the most important anti-bacterial drugs for the treatment of MRSA infection. Continuous monitoring is commonly recommended as it has a low therapeutic window, which is often limited by the equipment cost, and the technical skills required for modern TDM techniques such as HP-LCs and immunoassays. As a result, a cost-effective and quick detection solution for Vancomycin TDM is critical. We have already reported a successful vancomycin sensor on a ceramic base, a paper base, and a PET (polyethylene terephthalate) base, in our previous works 1,2. However, the long-term stability of the sensor for the clinical trial is very important. Therefore, this study focused on the improvement of the stability of the sensor.The PET chip is composed of a PET base on which the silver wiring was printed using an inkjet printer. It contains two holes for electrodes with a 2.0 mm diameter for the counter electrode and a 1.0 mm diameter for the working electrode. The chip also comprises a circular reservoir of diameter 8 mm. VCM imprinted poly(methylene bisacrylamide-co-methacrylic acid-co-Allylaminocarboxypropyonic-3-ferrocene) was grafted on graphite particle surface by a procedure similar to our previous work. This grafted graphite was mixed with a) silicon oil (MIPsi ), and b) paraffin oil (MIPpff ) to make a paste to use as the sensing material. The viscosity of both the oils was the same. We performed the chronoamperometric analysis with a VCM sample solution (0-60 µgmL-1, in phosphate buffer) filled in the sample reservoir.The chronoamperometric analysis time was 15 seconds for each sample. Current obtained at the 10th second was recorded to obtain the calibration curve. The change in current at 10s demonstrated strong linearity with the VCM concentration in both MIPsi and MIPpff , indicating good linearity with the change in current at 10s. Furthermore, this result was obtained using a "single-use" chip, which implies that each concentration was measured using a separate chip. MIPsi and MIPpff were both sensitive to vancomycin. However, when the sensor was packed and kept for 3 days, the MIPsi sensor lost its sensitivity completely. Sensor with the working electrode made of MIPpff, however, retained their sensitivity. MIPpff was further packed and kept for 10 days to have a deeper insight into the effect of binder oil on the long-term stability of the sensor and the sensor was still found to be sensitive. From the results of this study, it can be concluded that a stable sensor that can sensitively detect vancomycin can be made using paraffin oil as the binder oil. References Aaryashree, A., Takeda, Y., Yoshimi, Y., Hatano, A. & Kida, M. A Disposable Vancomycin Sensor Using Molecularly Imprinted Carbon Paste on a Ceramic Chip. in ECS Meeting s vols MA2020-02 3332–3332 (2020).Aaryashree et al. A “Single-Use” Ceramic-Based Electrochemical Sensor Chip Using Molecularly Imprinted Carbon Paste Electrode. Sensors 20, 5847 (2020).

Effect of high-speed shear flocculation on the flotation kinetics of ultrafine microcrystalline graphite

A novel process combining high-speed shear flocculation and flotation (SFF) was proposed to beneficiate ultrafine microcrystalline graphite (MG). The effect of high-speed shear flocculation on the flotation kinetics of ultrafine MG was investigated extensively by comparing with conventional flotation process. The flotation kinetics of these two processes were fitted with six flotation kinetic models using 1stOpt statistical analysis software. The results show that the flotation rate of MG in the SFF process is about 3 times as fast as that in the conventional flotation process based on the first-order model with rectangular distribution of flotabilities. On one hand, the high-speed shear flocculation process resulted in increasing size of graphite aggregates. On the other hand, it generated decreasing size of kerosene droplets, which in turn benefited the increase in the size of graphite aggregates due to the improved hydrophobicity of graphite particle surface. The increased aggregates were responsible for the increase in flotation rate of MG in the SFF process. In addition, the SFF process could also improve the concentrate grade and recovery of MG in comparison with conventional flotation. The utilization of the SFF technology to separate ultrafine MG is of great potential in industrial applications.

Enhancement of the wettability of graphite-based lithium-ion battery anodes by selective laser surface modification using low energy nanosecond pulses

The electrolyte filling process of battery cells is one of the time-critical bottlenecks in cell production. Wetting is of particular importance here, since only completely wetted electrode sections are working. In order to accelerate and facilitate this process, the authors of this study developed a method to significantly increase the wettability of graphite-based anodes by a laser surface modification using low energy nanosecond laser pulses. The anode surface microstructure was evaluated by means of white-light interferometry and scanning electron microscopy. The assessment of wettability was done by drop test and capillary rise test of the liquid electrolyte. The results show that there is a predominantly selective ablation process for laser energy inputs below 2 J/m by which the graphite active material remains unaffected and the binder material is decomposed. The observed increase in surface roughness correlates with the increasing wettability. Investigations using Raman spectroscopy showed that laser treatment leads to a damage on the crystalline structure of the graphite particle surface. However, treating an entire anode including 6 wt% binder and conductive carbon black has shown that the overall amorphous content of the anodes surface can be reduced by 32% through treating the surface with a laser energy of 1.29 J/m. Up to that point, which is the resulting parameter range for the selective process, it is possible to ablate the amorphous binder and carbon black phase coevally exposing graphite particles while keeping their crystalline structure. Exceeding that range, ablation of the whole anode composite dominates and amorphization of the graphite surface occurs. The electrode’s capacity was tested on half-cells in coin cell format. For the whole laser parameter range investigated, the anodes capacity matches the mass loss caused by laser ablation. No additional capacity loss was observed due to amorphization of the exterior graphite particle’s surface.

Molecularly Imprinted Carbon-Paste for Theophylline Sensing on a Disposable Paper Chip Sensor

Introduction Molecularly imprinted polymers (MIPs) are recognition elements with specific cavities designed for a particular target molecule. Recently, MIPs have been used in various applications explicitly requiring molecular recognition. In MIPs, the crosslinking monomers and functional monomers, having an affinity with a target molecule, are copolymerized in the presence of the target or the template molecule. Upon selective removal of the template molecule, imprinted cavities are formed. MIPs provide a wide range of benefits, including mechanical reliability, cost-effectiveness, and rapid mass production, and have recently been used for various applications, especially in biosensing areas [1]–[3].Theophylline (THO) is a drug commonly used for the therapy of respiratory diseases. However, owing to its highly toxic nature, an overdose can induce paralysis, seizures, and even death.[4] Additionally, the therapeutic window of THO is relatively small (5-15 mgmL-1) [4],[5], and therefore, the therapeutic drug monitoring (TDM) of theophylline is highly significant [5]. In this study, molecularly imprinted polymers grafted carbon pastes were prepared for THO sensing. The commonly used functional monomer, methacrylic acid, crosslinking monomers, N, N’-methylenebisacrylamide (MBAA), and ethylene glycol dimethacrylate (EDMA) were used, and the MIPs thus formed were evaluated using differential pulse voltammetry on a paper chip. Methods Fig. 1 shows the scheme of the paper chip along with the sensing response of theophylline MIP. The paper chip composed of a photo-paper base with electrodes printed using conductive ink through an inkjet printer. The holes for electrodes (working electrode, a reference electrode, and counter electrode) and reservoir are cut on laminating sheets using a laser cutter. The three parts are then attached using the laminator. The reference electrode is packed with Ag/AgCl ink and dried overnight at 60 ℃. The counter electrode with the printed conductive ink is used as it is. The MIP-grafted carbon paste is packed in the working electrode with the help of a glass tube. The theophylline imprinted poly(methylene bisacrylamide-co-ethylene dimethacrylate-co-methacrylic acid) was grafted on the graphite particle surface by a procedure similar to our previous work [3], [6]. This grafted graphite was mixed with ferrocene containing silicone oil to make a paste used as the sensing material. We performed the differential pulse voltammetry with theophylline sample solution (in saline buffer with pH 7.4, 0-40 mgmL-1 and whole bovine blood) filled in the sample-reservoir. Results and Conclusions The execution time of each voltammetry was 2 min only. The plot in Fig. 1 shows the influence of the theophylline concentration on the redox current at 0.8 V at the MIP-carbon paste electrode in both buffer saline and whole bovine blood. It is quite evident from the figure that MIP is sensitive towards theophylline in both buffer and whole blood. It indicates that MIP activates the electrocatalytic behavior of the carbon-paste electrode. The dynamic range at the MIP electrode versus the concentration of theophylline is seen in the range of 0-40 mgmL-1, which covers the therapeutically effective theophylline concentration level in plasma varying from 5 to 15 mgmL-1. The DPV measurements at each concentration has been done using a new chip every time, i.e. ‘single-use’ of the chip. Additionally, no reagents have been added during the analysis, thus making the procedure of drug level measurement simple. From the results of this study, it can be concluded that the proposed method is useful for quick and straightforward real-time TDM to prevent the toxic side effects of an overdose.

Practical Approach to Enhance Compatibility in Silicon/Graphite Composites to Enable High-Capacity Li-Ion Battery Anodes

There is an urgent need to improve the energy density of Li-ion batteries to enable mass-market penetration of electric vehicles, grid-scale energy storage, and next-generation consumer electronics. Silicon–graphite composites are currently the most plausible anode material to overcome the capacity limit of graphite or poor cycling performance of silicon. One serious and unrecognized limitation to the use of the composite as an anode is the incompatibility of hydrophobic (natural) graphite with the hydrophilic Si, which adversely affects battery performance. Herein, we report a novel, practical approach to modify the graphite resulting in the formation of a hard carbon coating and graphene sheets that give rise to higher compatibility with Si nanoparticles in the composite. Electrochemical and battery testing of the composite (10 wt % Si) anode shows higher reversible capacity (10% at C/12 and 20% at C/2) than the composite with unmodified graphite reaching ∼600 mAh/g with 95% retention after 100 cycles. The enhanced battery performance is explained by the uniform distribution of Si nanoparticles at the modified graphite surface due to the presence of graphene conductive networks and a thin, oxygen-rich, amorphous carbon layer on the surface of graphite particles, as evidenced by transmission electron microscopy (TEM) images and X-ray photoelectron spectra (XPS). This work provides a new approach to prepare graphite compatible materials that can work with hydrophilic components other than silicon for various applications other than batteries.

Preconcentration and Successful Selective Detection of Traces of Diclofenac in Water using a Nanostructured Modified Carbon Paste Electrode

AbstractA highly sensitive, simple and low cost sensor for the quantification of the diclofenac has been constructed. This sensor consists of a carbon paste nano‐structured by Multi‐Walled Carbon Nanotubes (G‐MWCNT)‐CPE. Scanning electron microscopy (SEM) and voltammetry technique were used to characterize the electrode material and to determine the analytical performances of the sensor in comparison with those obtained at a G‐CPE. The electrochemical oxidation of diclofenac on both G‐CPE and (G‐MWCNT)‐CPE electrodes is mainly controlled by adsorption, presenting a maximum peak current intensity in H2SO4 0.5 mol L−1. The carbon nanotubes, as well as they provide higher conductivity of the paste, act as spacers between the flake graphite particles and avoid their stacking in order to make the surface of graphite particles more accessible to DCF adsorption. The voltammetric measurements of diclofenac on (G‐MWCNT)‐CPE provide a large quantification range from 0.02 to 1 μmol L−1, a detection limit of 0.004 μmol L−1 and quantification limit of 0.014 μmol L−1 under the optimized operating conditions (H2SO4, 0.25 M+KCl 0.25 M, scan rate of 30 mV s−1, preconcentration time 18 min. and MWNTC% (30 %)). The (G‐MWCNT)‐CPE sensor was successfully applied to natural water samples, just acidified with sulfuric acid (pH<1). These samples were doped with diclofenac in sub‐micromolar range and the developed method was validated with excellent recoveries (within a maximum of 3 % difference from 100 %) for all samples indicating no interference effects of the water matrix.

Effective Upcycling of Graphite Anode: Healing and Doping Enabled Direct Regeneration

As lithium-ion batteries (LIBs) become vital energy source for daily life and industry applications, a large volume of spent LIBs will be produced after their lifespan. Recycling of LIBs has been considered as an effective closed-loop solution to mitigate both environmental and economic issues associated with spent LIBs. While reclaiming of transition metal elements from LIB cathodes has been well established, recycling of graphite anodes has been overlooked. Here, we show an effect upcycling method involving both healing and doping to directly regenerate spent graphite anodes. Specifically, using boric acid pretreatment and short annealing, our regeneration process not only heals the composition/structure defects of degraded graphite but also creates functional boron-doping on the surface of graphite particles, providing high electrochemical activity and excellent cycling stability. The efficient direct regeneration of spent graphite by using low cost, non-volatile and non-caustic boric acid with low annealing temperature provides a more promising direction for green and sustainable recycling of spent LIB anodes.

Mechanistic Role of Thermal Gradients on Lithium Plating in Li-Ion Batteries

Unwanted lithium deposition on the surface of graphite particles tends to occur during charging of Li-ion batteries at low temperatures, high rates, and high states of charge. However, the intricacies of the coupled thermal-electrochemical interactions that govern Li plating behavior are yet to be fully uncovered. Thermal inhomogeneity naturally develops during the high rate operation of large-format cells, particularly when active cooling systems are employed; hence, a deeper investigation of the relationship between thermal gradients and Li plating is merited. This study employs a microstructure-aware modeling approach to probe the influences of both in-plane and inter-electrode thermal gradients on Li plating. Both types of thermal gradient were found to cause inhomogeneous current distribution within the electrodes. While inter-electrode gradients resulted in a variation in the Li plating onset point and severity, the Li plating induced by in-plane gradients was nearly the same as for isothermal cases at the same mean temperature. The sensitivity of charging performance to mean temperature and thermal gradient magnitude was analyzed across a range of practical conditions. Electrochemical experiments were performed under applied external thermal gradients to study the effect on plating and cell lifespan in various cell formats, and the electrode degradation was characterized post-mortem. By gaining a fundamental understanding of the Li plating phenomenon, this study aims to assist in the design of electrode structures and cell formats that will reduce the propensity for this mode of degradation.

A Disposable Vancomycin Sensor Using Molecularly Imprinted Carbon Paste on a Ceramic Chip

Introduction Vancomycin (VCM) is the first-choice drug for the therapy of MRSA infection, which is the most typical nosocomial infection. However, VCM resistant bacteria is a severe worldwide problem [1]. Therapeutic drug monitoring (TDM) of VCM in the blood is useful to prevent the creation of resistant bacteria. Nevertheless, conventional TDM using immunoassay requires economical and labor burdens to hospitals [2]. Thus, an inexpensive disposable sensor that can determine the VCM concentration in blood with simple operation as that of blood sugar-sensor is required. In this study, we developed a VCM sensor using a carbon paste electrode grafted with a molecularly imprinted polymer (MIP) and a ceramic platform. MIPs are a molecular recognition element prepared by simple radical copolymerization in the presence of the target as a template. We have discovered that redox current at a MIP-grafted carbon paste electrode is sensitive to the target [3]. Method Figure 1(a) shows the scheme of the ceramic chip composed of aluminum oxide ceramic body and platinum wiring. It contains three holes for electrodes with 2.0 mm diameter and 0.4 mm depth, connected with platinum wiring at the bottom. The chip also comprises a square sample-reservoir of side 10 mm. VCM imprinted poly(methylene bisacrylamide-co-methacrylic acid-co-Allylaminocarboxypropyonic-3-ferrocene) was grafted on graphite particle surface by a procedure similar to our previous work [3], This grafted graphite was mixed with silicone oil to make a paste to use as the sensing material. A non-treated polymer was also synthesized in a similar way as that of VCM MIP, but without the template.Two of the holes of 2.0 mm diameter were each packed with grafted graphite and Ag/AgCl paste to act as the working electrode a reference electrode, respectively. The Pt wire of the third hole was used as the counter electrode. We performed differential pulse voltammetry with a VCM sample solution (0-60 mgmL-1, both in phosphate buffer and in bovine blood) filled in the sample-reservoir. Results and Conclusions The execution time of each voltammetry was 10 min only. Figure 1(b) shows the influence of the VCM concentration on the redox current at 0.8 V at both non-treated and the MIP-carbon paste electrode. It is quite evident from the figure that only MIP responds to VCM. The dynamic range at the MIP electrode versus the concentration of VCM is seen in the range of 0-60 mgmL-1, which corresponds covers the therapeutically effective vancomycin concentration level in plasma varying from 20 to 40 mgL-1 [4], [5]. Additionally, the R2 value of 0.9963 indicates a linear behavior of the sensor with change in drug concentration. From these results, it can be concluded that the proposed method is useful for quick and straightforward TDM to prevent both of the toxic side effects by overdose and the creation of antibacterials by underdose.

A "Single-Use" Ceramic-Based Electrochemical Sensor Chip Using Molecularly Imprinted Carbon Paste Electrode.

An inexpensive disposable electrochemical drug sensor for the detection of drugs (vancomycin, meropenem, theophylline, and phenobarbital) is described. Molecularly imprinted polymer (MIP) templated with the target drugs was immobilized on the surface of graphite particles using a simple radical polymerization method and packed into the working electrode of a three-electrode ceramic-based chip sensor. Differential pulse voltammetry (DPV) was used to determine the relationship between the response current and the concentration of the targeted drug while using one sensor chip for one single operation. The time required for each DPV measurement was less than 2 min. Concentrations corresponding to the therapeutic range of these drugs in plasma were taken into account while performing DPV. In all the cases, the single-used MIP sensor showed higher sensitivity and linearity than non-imprinted polymer. The selectivity test in drugs with a structure similar to that of the target drugs was performed, and it was found that MIP-based sensors were more selective than the untreated ones. Additionally, the test in whole blood showed that the presence of interfering species had an insignificant effect on the diagnostic responses of the sensor. These results demonstrate that the disposable MIP-sensor is promising for quick and straightforward therapeutic drug monitoring to prevent the toxic side effects and the insufficient therapeutic effect due to the overdose and underdose, respectively.