Optimal Experimental Conditions Research Articles

Measures of solid-state material and powder bed absorptivity in the visible and near IR spectrum with new small homemade integrative spheres

Abstract The absorptivity is a major parameter in laser-matter interaction. It can be measured by different methods (thermal or optical). The already known integrating sphere method is generally used with spheres whose choice of dimensions and architecture is not discussed in the literature. The influence of the parameters of the sphere (size of the sphere, position of the photodiode on the sphere, distance of the photodiode from the sphere, opening of the passage of the laser, distance from sample to the sphere, presence of a baffle in front of the photodiode, sample angle, coating materials) was tested with a mirror of known reflectivity. This study has demonstrated that it is possible to use small integrating spheres for absorptivity measurements. These spheres are home-made by additive manufacturing from a polymer, with the inner walls coated with BaSO4. The optimum experimental conditions for these small spheres are defined, particularly the angle sample. The absorptivity of various materials in the solid state and powder bed was measured for four wavelengths. These measurements were carried out for three sizes of spheres and confirmed the literature results (for example, the absorptivity is measured at 80% for copper at blue wavelength). This small sphere will be adapted to in-situ measurement, particularly in the Laser Powder Bed Fusion process whatever wavelength, particularly new green or blue laser sources, and material.

DETERMINATION OF ANTIVIRAL-DRUG FAVIPIRAVIR FROM BIOLOGICAL SAMPLES BY USING MOLECULAR IMPRINTED POLYMER-BASED ELECTROCHEMICAL SENSOR

Objective: The molecularly imprinted polymer (MIP) technique was applied in this study for selective, fast, and sensitive electrochemical determination of antiviral drug favipiravir (FAVI). Material and Method: By electropolymerizing the functional monomer o-phenylenediamine (o-PD) on a glassy carbon electrode (GCE) in the presence of a template molecule FAVI, the new MIP-based sensor (MIP@o-PD/GCE) was constructed using cyclic voltammetry (CV). For the removal and rebinding procedures, as well as the optimization of conditions and performance measurement of MIP@o-PD/GCE, differential pulse voltammetry (DPV) was used. The ferrocyanide/ferricyanide redox marker was used to monitor each step of the experimental procedure using DPV. Result and Discussion: MIP@o-PD/GCE has a linear response to FAVI in the range from 10 pM to 90 pM under optimal experimental conditions for human serum samples. The detection limit of MIP@o-PD/GCE was obtained to be 1.80 pM, whereas the quantification limit was found to be 6.23 pM. The designed sensor was successfully applied to a synthetic human serum sample to verify its applicability and validity. Electrochemical sensor selectivity was evaluated by comparing the binding of paracetamol and tenofovir, which are similar to favipiravir, and also oseltamivir and famciclovir, which are other drugs used in the treatment of COVID-19.

Covalent organic framework-based ratiometric electrochemical sensing platform for ultrasensitive determination of amyloid-β 42 oligomer

Accurate and sensitive detection of amyloid-β 42 oligomer (Aβ42O) is of great significance for early diagnosis of Alzheimer's disease (AD). Herein, a signal on-off ratiometric electrochemical immunosensor was developed for highly selective and quantitative determination of Aβ42O by using novel covalent organic frameworks (COFs) composites as the sensing platform. This immunosensor produced two independent electrochemical signals from the [Fe(CN)6]3−/4− and methylene blue (MB) probes at different potentials based on the electrocatalytic activity of gold nanoparticle−functionalized porphyrinyl COFs nanocomposites toward [Fe(CN)6]3−/4− and the signal probe of MB encapsulated in the aptamer-modified alkynyl COFs. Because the two signals of [Fe(CN)6]3−/4− and MB changed in opposite directions, a signal on−off mode was generated which can correct the results by introducing a reference signal and effectively eliminate background interference. Under optimal experimental conditions, the current ratio (IMB/I[Fe(CN)6]3−/4−) was well linearly related to the logarithmic value of Aβ42O concentrations in the range of 10 pM to 1 μM, and the detection limit was 5.1 pM (S/N = 3). Additionally, the immunosensor exhibited satisfactory performance in case of real cerebrospinal fluid samples. The designed ratiometric electrochemical immunosensor provides a valuable route for early diagnosis of AD and our results also pave the way for designing of sensing platforms using COF-based nanomaterials and extending their functions and applications to bioanalysis.

Enzymatically Mediated In Situ Generation of Z-Scheme Bi2S3/Bi2MoO6 Heterojunction-Based Organic Photoelectrochemical Transistor for METTL3/METTL14 Detection.

The OPECT biosensing platform, which connects optoelectronics and biological systems, offers significant amplification and more possibilities for research in biological applications. In this work, a homogeneous organic photoelectrochemical transistor (OPECT) biosensor based on a Bi2S3/Bi2MoO6 heterojunction was constructed to detect METTL3/METTL14 protein activity. The METTL3/METTL14 complex enzyme was used to catalyze adenine (A) on an RNA strand to m6A, protecting m6A-RNA from being cleaved by an E. coli toxin (MazF). Alkaline phosphatase (ALP) catalyzed the conversion of Na3SPO3 to H2S through an enzymatic reaction. Due to the adoption of the strategy of no fixation on the electrode, the generated H2S was easy to diffuse to the surface of the ITO electrode. The Bi2S3/Bi2MoO6 heterojunction was formed in situ through a chemical replacement reaction with Bi2MoO6, improving photoelectric conversion efficiency and realizing signal amplification. Based on this "signal on" mode, METTL3/METTL14 exhibited a wide linear range (0.00001-25 ng/μL) between protein concentration and photocurrent intensity with a limit of detection (LOD) of 7.8 fg/μL under optimal experimental conditions. The applicability of the developed method was evaluated by investigating the effect of four plasticizers on the activity of the METTL3/METTL14 protein, and the molecular modeling technique was employed to investigate the interaction between plasticizers and the protein.

Dispersive micro-solid phase extraction based on two MOFs as highly effective adsorbents for analysis of nilotinib in plasma and wastewater.

Nilotinib (NIL) is a prescription medication employed in the treatment of specific types of leukemia, namely chronic myelogenous leukemia (CML). The determination of NIL levels in patients undergoing treatment for CML is of paramount importance for effective management of treatment and toxicity. Also, monitoring and controlling its level in wastewater sources could help scientists to identify potential hotspots of contamination and take appropriate measures to mitigate their impact on the environment and public health. This study presents a D-µ-SPE technique utilizing two MOFs as adsorbents for the efficient detection of nilotinib in plasma and wastewater samples for the first time. Two highly effective MOFs, MIL-101(Fe) and MIL-53(Al), were synthesized and applied as dispersive micro-solid phase extraction (D-µ-SPE) adsorbents for the extraction of nilotinib coupled with HPLC-UV in a short time of analysis. Experimental parameters affecting extraction efficacy such as adsorbent amount, ionic strength, pH value, adsorption-desorption time and type of elution solvent, were optimized. Under optimal experimental conditions, the linear dynamic was achieved in the range of 0.25-5.00 µg/mL in human plasma and 0.01-0.20 µg/mL in wastewater. The extraction recovery was in the range of 89.18-91.53% and 94.39-99.60% for nilotinib and MIL-101(Fe) and also 91.22-97.35% and 98.14-100.78% for nilotinib and MIL-53(Al) from human plasma and wastewater respectively. HPLC-UV determination of nilotinib after the D-µ-SPE method showed acceptable accuracy and precision in both plasma and wastewater. In comparison between the two adsorbents, the extraction procedure was easier and faster with MIL-53(Al) as the adsorbent.

OPTIMIZATION OF NEWLY FABRICATED LACCASE BIOSENSOR BASED ON SINGLE-WALLED CARBON NANOTUBE FOR TYRAMINE DETECTION

Tyramine (TYR), also identified as 4-(2-aminoethyl) phenol, is an organic compound. Its elevated presence indicates prolonged food storage, leading to spoilage and potentially impacting human well-being. To address this concern, a biosensor was designed on a single-walled carbon nanotube carboxyl-functionalized screen-printed carbon electrode (COOH-SWCNT-SPCE). Laccase (LAC)-based electrochemical biosensors were effectively created using a simple and innovative technique involving enzyme LAC being drop cast. Electrochemical Impedance Spectroscopy (EIS), Cyclic Voltammetry (CV), and Differential Pulse Voltammetry (DPV) were utilized to assess the properties and electrochemical behavior of the modified SPCEs. Under optimal experimental conditions, the LAC/COOH-SWCNT-SPCE biosensor exhibited favorable performance at scan rates of 50 mV s-1 (within the range of 10 to 500 mV s-1), pH 8.0 (ranging from 7.0 to 10.0), 4 µL enzyme LAC (varying from 2 to 10 µL), and 1.0 mg mL-1 SWCNTs (ranging from 0.2 to 3.0 mg mL-1). Deposition potential and time were set at 0.5 V. The modified SPCEs demonstrated effective usage for TYR measurement, achieving a Correlation Coefficient (R2) of 0.981 and a Limit of Detection (LOD) of 0.070 mM.

Advancing Precision in Vascularized Composite Allografts through Multiplex Sensing of Predictive Biomarkers

Vascularized Composite Allotransplantation (VCA) is a promising option for extensive tissue reconstruction. Successful graft outcomes in VCA surgeries require close monitoring of immunological reactions and the progression of ischemic conditions. Excessive immunosuppression may lead to chronic infections and dangerous side effects, while inadequate immunosuppression can result in acute or chronic rejection episodes, jeopardizing graft function. Monitoring the immunological status of an allograft becomes critical when exploring innovative tolerance induction protocols or transitioning patients from conventional therapies. Currently, confirming clinical rejection involves invasive biopsies, which are suboptimal for routine monitoring due to associated risks. Thus, developing non-invasive technologies capable of detecting changes in the immunological status of the graft before apparent clinical signs of inflammation and tissue damage become imperative. To address these limitations, this study proposes a low-cost, portable, flexible, miniaturized, and site-of-care (SOC) platform for multiplex sensing of predictive biomarkers (e.g., interleukin 6 (IL6), lactate) and pH to detect instances of VCA rejection before apparent clinical signs of immunogenic reactions such as inflammation and tissue damage.The sensor fabrication was performed on in-house fabricated porous laser-engraved graphene (PLEG)-electrode, utilizing the laser-induced carbonization (LIC) technique on a thin (12.5 µm) polyimide (PI) surface at optimized laser parameters (laser power-22%, speed-5.2%, and gas flow-50%). The PI sheet was laminated on a polyethylene terephthalate (PET) sheet with silicone adhesive in the middle, helping to dissipate the heat generated during the carbonization process. Compared to conventional screen-printed platforms, the PLEG electrode provides higher surface area, receptor loading, electrical conductivity, ease of surface modification, and improved sensitivity with an average resistance of 40 ± 3 Ω/cm. Subsequently, the connection pad and reference electrodes (RE) were coated with silver/silver chloride (Ag/AgCl) conductive paste for improved connection. The RE was stabilized by coating it with polyvinyl butyrate (PVB) and sodium chloride polymeric cocktail. Three working electrodes (WE) were designated as WE-1 (for IL6), WE-2 (for lactate), and WE-3 (for pH). The sensor construction was initiated with surface activation WEs in 0.50 M H2SO4 containing 0.10 M KCl as a supporting electrolyte by sweeping potential between 1.0 and -1.2 V vs. Ag/AgCl reference electrode. For IL-6 sensing, the WEs were incubated with freshly prepared 1-pyrenebutyric acid N-hydroxysuccinimide (PBASE) as a non-covalent crosslinker (10.0 mM) in dimethylformamide (DMF) for 3 hrs., followed by buffer wash (3 times) to remove any unbound crosslinker. Later, a monoclonal antibody to IL6 was immobilized using peptide bond formation between PBASE and the recognition element, passivated by incubating in Bovine serum albumin (BSA) to block non-specific binding. Upon binding, the antigen-antibody complex's formation results in a decrease in voltammetric signal of the redox signal, generating an IL6-dependent change in current. For lactate detection, an amperometric method utilizes a two-electrode electrochemical setup. The WE comprise a composite Glutaraldehyde/BSA/Lactate-Oxidase/Prussian Blue/PLEG-electrode (GA/BSA/LOx/PB/ PLEG). An Ag/AgCl-coated electrode serves as the RE, and counter electrodes (CE). For the pH sensor (PANI/PLEG), polyaniline (PANI) was electrodeposited at 0.80 V for 600 sec on an activated PLEG electrode washed with distilled water and coated with Nafion (0.25% v/v). For pH measurements, the open-circuit potential (OCP) was measured between the PANI/PLEG electrode and the RE.Post characterization, the sensor’s electrochemical measurements to detect IL6, lactate, and pH were performed in buffer, artificial interstitial fluid, porcine blood, and serum samples with portable potentiostat. Under optimal experimental conditions, the devised platform showed a sensitivity of 2.59 µA/(log10IL6), 0.021 µA/mM, and ~49.39 ± 2 mV in spiked serum for IL6, lactate, and pH, respectively. Subsequently, serum samples of porcine VCA recipients were collected on postoperative days (POD) 0, 2, and 6 and tested using the IL-6, lactate, and pH sensors, respectively. The sensors can successfully track the change in the levels of IL6 (increasing) and lactate (increasing) and the change in pH post-surgery and align with clinical observations of inflammation and ischemia post-allograft on POD6. The sensor results were also validated using commercial IL6 ELISA and lactate kits using the same samples and showed a correlation (r) of r = 0.9885 (n=3, for IL6) and r = 0.9896 (n=3, for lactate). Our results demonstrate that the developed miniaturized platform offers a portable, low-cost, robust, and multiplex sensing platform capable of quantifying predictive biomarkers post-VCA surgeries. This platform presents a promising, miniaturized, and cost-effective solution for the real-time monitoring of biomarkers in VCA models. KEYWORDS: Vascularized Composite Allotransplantation (VCA), Ischemia, Interleukin-6, Lactate, Electrochemical sensor, Porous laser engraved graphene, Multiplex sensing

Tools for Parameterization of a Single Particle Model with Electrolyte Dynamics (SPMe) with Bayesian Experimental Design to Capture Degradation-Induced Capacity Fade in Lithium-Ion Batteries

The intelligent design of durable, next-generation lithium-ion batteries can be facilitated through the use of computationally efficient models that capture battery physics. In this work, we demonstrate a single particle model with electrolyte dynamics (SPMe), which accounts for battery capacity fade caused by mechanisms such as solid electrolyte interface (SEI) growth, lithium plating, and stress-induced particle cracking. The model is trained using both experimental data and data generated using a higher-fidelity Doyle-Fuller-Newman model so the ground truth parameters are known. To quantify and reduce the uncertainty in the unknown model parameters, we are developing a Bayesian experimental design approach that, with the aid of multiple models with varying fidelity, can rapidly identify optimal experimental input conditions leading to the greatest expected information gain.

Development of Aptamer-Functionalized Gold Nanoparticles as Probes in Point-of-Care Diagnostic Device for Rapid Detection of Multidrug-Resistant Bacteria in Bombyx mori L. .

The sericulture industry suffers severe crop losses due to various silkworm diseases, necessitating the development of further technologies for rapid pathogen detection. Here, we report an all-in-one portable biosensor that combines conjugated gold nanoparticles (Au NPs) with an aptamer-based lateral flow assay (LFA) platform for the real-time analysis of Mammaliicoccus sp. and Pseudomonas sp. Our platform enables sample-to-answer naked eye detection within 5 min without any cross-reactivity with other representatives of the silkworm pathogenic bacterial group. This assay was based on the sandwich-type format using a bacteria-specific primary aptamer (Apt1) conjugated with 23 nm ± 1.27 nm Au NPs as a signal probe and another bacteria-specific secondary aptamer (Apt2)-coated nitrocellulose membrane as a capture probe. The hybridization between the signal probe and the capture probe in the presence of bacteria develops a red band in the test line, whose intensity is directly proportional to the bacterial concentration. Under the optimal experimental conditions, the visual limit of detection of the strip for Mammaliicoccus sp. and Pseudomonas sp. was 1.5 × 104 CFU/mL and 1.5 × 103 CFU/mL, respectively. Additionally, the performance of the LFA device was validated by using a colorimetric assay, and the results from the colorimetric assay are consistent with those obtained from the LFA. Our findings indicate that the developed point-of-care diagnostic device has significant potential for providing a cost-effective, scalable alternative for the rapid detection of silkworm pathogens.

A Nafion/BiVO4-COOH-MWCNTs/GCE for the sensitive determination of Cd2+ and Pb2+ by DPASV

BiVO4 was hydrothermally prepared and then ultrasonically mixed with carboxylated multiwalled carbon nanotubes (COOH-MWCNTs) to yield a BiVO4-COOH-MWCNTs composite. The composite were cast-coated on a glassy carbon electrode (GCE) to yield a BiVO4-COOH-MWCNTs/GCE, and then a Nafion solution was cast-coated on the BiVO4-COOH-MWCNTs/GCE to yield a Nafion/BiVO4-COOH-MWCNTs/GCE. The related materials and electrodes were characterized by field emission scanning electron microscopy, X-ray diffractometer and electrochemical methods. Under the optimal experimental conditions, Cd2+ and Pb2+ were analyzed by differential pulse anodic stripping voltammetry on the Nafion/BiVO4-COOH-MWCNTs/GCE, giving a linear detection range (LDR) from 10.0 nM to 2.00 μM and a limit of detection (LOD, S/N = 3) of 0.5 nM for Cd2+, as well as a LDR from 10.0 nM to 1.00 μM and a LOD of 0.9 nM for Pb2+. The Nafion/BiVO4-COOH-MWCNTs/GCE exhibited good selectivity, stability and reproducibility and returned satisfactory results of determining Cd2+ and Pb2+ in seafood samples.

Probiotic bacterial adsorption coupled with CRISPR/Cas12a system for mercury (II) ions detection

The complex sample matrix poses significant challenges in accurately detecting heavy metals. In view of its superior performance for the biological adsorption of heavy metals, probiotic bacteria can be explored for functional unit to eliminate matrix interference. Herein, Lactobacillus rhamnosus (LGG) demonstrates a remarkable tolerance and can adsorb up to 300 μM of Hg2+, following the Freundlich isotherm model with the correlation coefficient (R2) value of 0.9881. Subsequently, by integrating the CRISPR/Cas12a system, a sensitive and specific fluorescent biosensor, “Cas12a-MB,” has been developed for Hg2+ detection. Specifically, Hg2+ adsorbed onto LGG can specifically bind to the nucleic acid probe, thereby inhibiting the binding of the probe to LGG and the subsequent activation of the CRISPR/Cas12a system. Under optimal experimental conditions, with the detection time of 90 min and the detection limit of 0.44 nM, the “Cas12a-MB” biosensor offers a novel, eco-friendly approach for Hg2+ detection, showcasing the innovative application of probiotics in biosensor.

Harmonization of experimental procedures to assess mitochondrial respiration in human permeabilized skeletal muscle fibers

AimHigh-resolution respirometry in human permeabilized muscle fibers is extensively used for analysis of mitochondrial adaptions to nutrition and exercise interventions, and is linked to athletic performance. However, the lack of standardization of experimental conditions limits quantitative inter- and intra-laboratory comparisons. MethodsIn our study, an international team of investigators measured mitochondrial respiration of permeabilized muscle fibers obtained from three biopsies (vastus lateralis) from the same healthy volunteer to avoid inter-individual variability. High-resolution respirometry assays were performed together at the same laboratory to assess whether the heterogenity in published results are due to the effects of respiration media (MiR05 versus Z) with or without the myosin inhibitor blebbistatin at low- and high-oxygen regimes. ResultsOur findings reveal significant differences between respiration media for OXPHOS and ETcapacities supported by NADH&succinate-linked substrates at different oxygen concentrations. Respiratory capacities were approximately 1.5-fold higher in MiR05 at high-oxygen regimes compared to medium Z near air saturation. The presence or absence of blebbistatin in human permeabilized muscle fiber preparations was without effect on oxygen flux. ConclusionOur study constitutes a basis to harmonize and establish optimum experimental conditions for respirometric studies of permeabilized human skeletal muscle fibers to improve reproducibility.

Bio-Based Materials for Electrochemical Detection of Bisphenol A

Bisphenol A is a widely used endocrine disruptor known for its toxicity and prevalence in the environment. It contaminates drinking water, especially when plastic bottles are exposed to Sunlight. Rapid, on-site detection of BPA in drinking water is crucial for protecting human health and the environment. Herein, we developed an electrochemical sensor for detecting and monitoring bisphenol A in water bodies utilizing biobased materials. The device uses a biopolymeric membrane with agarose and gelified green tea tannins (GT/Agar). A sensitive part was made using this natural composite due to its high ability to attach bisphenol A to tannin monomers. Green tea tannins were purified and characterized through HPLC, FTIR, SEM, and AFM. The electrochemical activity of the GT-Agar/Au sensor is also evaluated by electrochemical impedance spectroscopy, cyclic voltammetry, square wave voltammetry and scan rate. Based on its redox signal under the optimal experimental conditions, this sensor has a detection range of 10−16 M to 10−4 M, a limit of detection of 1.52 to 10−17 M and very high selectivity. The proposed sensor successfully determined BPA levels from ultra-trace concentrations in bottled water samples, achieving satisfactory recovery rates. Compared to the results obtained using HPLC, it demonstrates high reliability.

High-temperature assisted barium molybdate incorporation into heteroatom-doped porous carbon sheets for selective detection of sulfonamide derivatives

Electrochemical sensors are inherently dependent upon novel electrocatalyst materials with excellent properties. A rapid analytical technique was developed to determine 5-aminosalicylic acid (5-ASA) without the need for time-consuming separation steps. In this study, the perovskite-type barium molybdate (BaMoO3) nanocubes and phosphorous-doped graphitic carbon nitride (P-gC3N5) were prepared by coprecipitation followed the chemical vapour deposition method. Various spectroscopic techniques were performed to analyse the morphology and structure of the proposed electrocatalyst (BaMoO3/P-gC3N5). BaMoO3/P-gC3N5 modified glassy carbon electrodes (GCE) exhibit superior electrocatalytic activity towards 5-ASA detection over unmodified electrodes. Difference Pulse Voltammetry (DPV) was used under optimal experimental conditions for determining 5-ASA accurately. Combining BaMoO3 and P-gC3N5 forms an electrocatalytic hybrid composite with a large specific surface area, rapid electron transfer, and high electrical conductivity. BaMoO3/P-gC3N5 modified electrodes possess a broad detection range (0.01–723 µM), low limit of detection (4.0 nM), excellent selectivity, sensitivity (1.046 µAµM-1cm−2), and good reproducibility toward the detection of 5-ASA. Human serum, urine, and river water samples were successfully tested for 5-ASA content with the electrochemical sensor fabricated.

Simulation and Selection of the Optimal Experimental Conditions to Determine the Low-Energy Parameters of the np Interaction in the nd Breakup Reaction at a Neutron Energy of 5 MeV

Simulation and Selection of the Optimal Experimental Conditions to Determine the Low-Energy Parameters of the np Interaction in the nd Breakup Reaction at a Neutron Energy of 5 MeV

Nanostructured TiO2-X/CuXO-based electrochemical sensor for ultra-sensitive glyphosate detection in real water samples

Glyphosate, a widely employed non-selective pesticide for enhancing crop productivity through weed control, poses significant health and environmental concerns due to its potential link to chronic diseases, cancers, and disruptions in natural symbiotic relationships. Quantifying glyphosate values becomes imperative for effective monitoring and mitigation of associated risks. In response, a novel electrochemical sensor was developed utilizing nanostructured TiO2 films modified with Ti3+ ions and copper oxides for precise detection and quantification of glyphosate in real water samples. The nanotubular structure, synthesized via potentiostatic anodization, underwent further modification through cathodic reduction of Ti4+ to Ti3+ ions and copper electrodeposition. Under optimal experimental conditions, the sensor exhibited a notable ability to detect glyphosate traces by inhibiting peak current in Differential Pulse Voltammetry (DPV). It achieved low limits of detection (LOD = 0.34 pmol/L) and quantification (LOQ = 0.70 pmol/L) within a linear working range of 0.55 to 1000.00 pmol/L. The sensor demonstrated robust stability and excellent precision (repeatability and intermediate precision) without significant variations in analytical response and yielded recovery rates ranging from 91.06 to 99.38 %. These promising results underscore the sensor’s potential application for detecting glyphosate in real aquatic matrices, contributing to effective environmental monitoring and health protection.

Nitrogen-Doped Carbon Dots Enhanced Hydrogen Carbonate-Hydrogen Peroxide Chemiluminescent Reaction and its Application in Ascorbic Acid Sensing.

Nitrogen-doped carbon dots (N-CDs) were prepared by self-exothermic procedure using grasshopper powder as a single precursor. The prepared N-CDs not only have excellent fluorescence properties, but also can catalyze and enhance the ultra-weak chemiluminescence of NaHCO3-H2O2. The reaction conditions of NaHCO3-H2O2-N-CDs CL were optimized. Under the optimal experimental conditions, when AA was added to the NaHCO3-H2O2-N-CDs CL system, AA had a significant inhibitory effect on the CL intensity of NaHCO3-H2O2-N-CDs. There was a good linear relationship between the calculated lg(I0/I) and the concentration of AA (C), and the calibration curve equation was lg(I0/I) = 0.03667C-0.00708 (µM). The established CL analysis method has a detection limit of 0.12 µM for AA and a linear range of 0-50 µM. The selectivity of CL method was evaluated, and the method was successfully applied to the determination of AA in vegetable and fruit samples. The spiked recoveries were between 88.9% and 118.9%, which indicated that the method was simple, rapid, and sensitive, and had great potential in the determination of AA in foods.

Low-temperature fabrication of high-entropy rare earth hexaboride powders

Herein, we report a low-temperature method for synthesizing high-entropy rare earth hexaboride powders by reaction among rare earth oxides, B4C, and Al powders. Al was used as a reducing and decarburization agent in this process, which further reduced the Gibbs free energy change for the reaction of RexOy with B4C to form REB6. By investigating the influence of reacting temperature and amount of Al added on preparation of LaB6, the optimum experimental conditions of this method were determined to be 1300 °C and 2 times the stoichiometric ratio of Al. Theoretical supports were proposed to verify the feasibility for formation of high-entropy borides. Then, multicomponent hexaborides La0.5Ce0.5B6, La0.33Ce0.33Nd0.33B6, and La0.25Ce0.25Nd0.25Sm0.25B6 as well as high-entropy hexaboride La0.2Ce0.2Nd0.2Sm0.2Eu0.2B6 powders were successfully prepared by doping with Ce, Nd, Sm, and Eu on LaB6. RE elements with different radius were uniformly distributed in the multicomponent boride powders without obvious segregation. More importantly, the lattice distortion and stress induced by the element substitution contribute to the reduction of the average powder particle size. Finally, the DTA-TG curves show that rare earth hexaborides have good oxidation resistances when the temperature is below about 1000 °C.

An electrochemical 3D platform using poly (alizarin red S) and magnetite nanoparticles for rapid recognition and determination of tryptophan enantiomers in whole blood samples

The construction of a simple and convenient electrochemical platform for the recognition of enantiomers is crucial for the life sciences and medical fields. Herein, a portable electrochemical 3D platform based on a carbon paste electrode modified (CPE) with poly (alizarin red S) (PARS) and magnetite nanoparticles (Fe3O4NPs) for the recognition and determination of tryptophan enantiomers from whole blood samples was developed. Several methods, including scanning electron microscopy (SEM), differential pulse voltammetry (DPV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), were used to evaluate the morphologies and electrochemical behaviors of the modified electrode. The synthesized magnetite nanoparticles are studied using SEM with energy-dispersive X-ray analysis (EDAX). Under the optimum experimental conditions, the current intensity ratio of d-Trp to l-Trp (ID/IL) was found to be 1.32 at PARS/Fe3O4NPs/CPE, according to the results of differential pulse voltammetry. Furthermore, the developed platform showed a good linear correlation between response current intensity and tryptophan enantiomer concentration, ranging from 0.001 to 0.2 mM. The detection limits for both d-Trp and l-Trp were found to be 0.3 µM. This study demonstrates that the designed platform is capable of rapidly detecting the enantiomeric ratio in a non-racemic tryptophan mixed solution. Finally, the proposed platform was used to identify the Trp enantiomers in human whole blood, confirming the effectiveness of the modified electrode in analyzing real samples. The electrochemical 3D platform is thus used not only to recognize tryptophan enantiomers but also exhibits a significant promise for practical uses.

Zirconia nanoparticles/carbon quantum dots modified carbon paste electrode as electrochemical sensor for determination of antiepileptic drug eslicarbazepine acetate in bulk and pharmaceutical dosage form

A new, sensitive and selective electrochemical method has been developed for determination of the antiepileptic prodrug eslicarbazepine acetate (ESL) that is used for the treatment of partial-onset seizures in adults with epilepsy. It belongs to the class of sodium channel blockers called dibenzoazepine family. A novel modified zirconia nanoparticles carbon paste nanocomposite, carbon dots sensor prepared from banana peels by solvothermal method has been fabricated. The voltammetric method is based on the direct anodic oxidation of ESL at the electrode surface using differential pulse voltammetry. Under the optimum experimental conditions, ESL exhibited a linear relationship in the range of 3.04 × 10-8 to 9.66 × 10-5 M with a lower detection limit of 7.57 × 10-9 M and quantification limit of 2.29 × 10-8 M. The proposed method was validated according to ICH guidelines and was applied for estimating ESL in raw material showing high accuracy and precision with successful application on tablet dosage form.