Reactive Ion Research Articles

Development of a Controlled Humidity Differential Electrochemical Gas Monitoring System

Lithium-air batteries (LABs) represent a promising future battery technology due to their high energy density, although several challenges hinder them from achieving their theoretical performance. These challenges include clogging of the porous air cathode by insoluble discharge products and high overpotentials during cycling [1, 2]. A recent proposal to address these issues involves the reversible formation and oxidation of LiOH in nonaqueous LABs. Of course, LiOH-based LABs require a proton source to form LiOH from the electrochemical reaction of oxygen and lithium ions [3]; humidity in air is an obvious choice for the proton source, making the relative humidity of LAB feed gas an important parameter to control and monitor during LAB electrochemical analysis.For LABs, galvanostatic charge/discharge coupled with quantitative gas evolution/consumption measurement is essential to understand the electrochemical processes during battery operation. Here, we report an advanced operando pressure measurement system that allows the control and monitoring of humidity in the cell headspace while also tracing overall gas consumption and evolution. Our gas handling system generates humid air using a water-containing chamber with a temperature control vessel to generate water vapor. A mass flow controller mixes dry air with humid air to generate specific relative humidity and send it to the cell. Using various low-volume in-line sensors, our system can track headspace humidity, temperature, and pressure within a custom-modified Swagelok-type cell. The total headspace volume must be small (~mL) since gas consumption occurs on a μmol scale in our lab-scale cells. To minimize headspace and dead volume within the Swagelok-type cell, a digital humidity and temperature sensor with exceptional accuracy was integrated into a customized printed circuit board (PCB). This PCB is attached to the small dead-volume Tee connection. To control the humidity inside the cell and achieve sensor data simultaneously, all sensors in the monitoring system are controlled by a LabVIEW program (National Instruments). To show the utility of this new system, we will present analyses of nonaqueous and solid-state LAB cells that operate at various humidities and current rates, while employing various known 2 e- and 4 e- oxygen reduction catalysts.

Systematic Investigations of Surface Oxygen Functional Groups on Spherical Hard Carbon for Sodium-Ion Batteries

The surface activity of hard carbons and its effect on the formation of a stable solid electrolyte interface (SEI) in sodium ion batteries has gained significant interest in the scientific community over the last years. The surface of hard carbons thus plays a pivotal role within the cell, as it constitutes the interface between the bulk material and the electrolyte. Following pyrolysis of the carbon-rich precursor at high temperatures, various oxygen functional groups (OFGs) and defects, such as five- or seven-membered rings, are present on the surface of the resulting hard carbons. The influence of OFGs on the surface is however controversially discussed. On the one hand, irreversible reactions of sodium ions with OFGs lower the initial coulombic efficiency (ICE), which leads to a decreased energy density. On the other hand, OFGs may also serve as nucleation sites for the SEI leading to a more conductive interfacial phase for sodium ions. Although many approaches of additional oxygen functionalization on the surface of hard carbons have already been reported, they mostly employ harsh reaction conditions disregarding the morphological impact on the carbon surface.In our studies, oxo-functionalized polycyclic aromatic hydrocarbons (PAHs) are adsorbed on the surface to serve as model OFGs on surface oxygen deficient hard carbons. The versatility of functionalized pyrenes in combination with nondestructive adsorption enables independent investigations on the oxygen functionalization of the hard carbon surface. In the first step, native surface oxygen groups are cleaved from the pristine hard carbon through a high-temperature post-treatment in hydrogen atmosphere. Afterwards, selective re-introduction of surface OFGs is achieved through adsorption of oxo-functionalized pyrene derivatives such as 1-hydroxypyrene or 1-pyrenecarboxylic acid to simulate hydroxy or carboxylic surface functionalities. Additionally, various spatially configurations of surface OFGs can be mimicked by elongating the distance between the oxygen functionality and the pyrene backbone through a short alkyl chain (e.g. 1-pyrenebutyric acid).Our systematic approach of selectively re-introducing surface OFGs allows the discrimination between different surface OFGs and their influence on the SEI. The surface of our modified hard carbons is characterized by X-Ray photoelectron spectroscopy (XPS) and Raman spectroscopy to evaluate the oxygen content and determine the defect concentration. The electrochemical performance is assessed by rate performance tests and cyclic voltammetry in three-electrode half-cells with sodium metal as counter and reference electrode. Initial findings validate the correlation between surface oxygen functionalization determined by XPS and the electrochemical formation potential of the SEI during the first cycle. After high-temperature treatment in a hydrogen atmosphere, the surface oxygen content decreases from ~5% to 2%, leading to a significant lowering of the plateau capacity. Simultaneously, the ICE decreases from 79% to 55%. Cyclic voltammetry of deoxygenated hard carbon reveals that the SEI formation potential is shifted from ~1.0 V vs. Na towards lower potentials of ~0.3 V vs. Na indicating that different decomposition products are formed. Furthermore, rate performance is substantially deteriorated by the development of a modified SEI. Ex-situ XPS of cycled electrodes and electrochemical impedance spectroscopy are used to identify differences in the SEI composition and link them to the electrochemical performance of our spherical hard carbons.Figure: 1-Pyrenebutyric acid adsorbed on the surface of hard carbon highlighting the different possible spatially orientations of the oxygen functional group. Figure 1

Operando X-Ray CT Analysis of Silicon/Solid Electrolyte Mechanical Interface of All-Solid-State Battery during Charging and Discharging Reaction

Silicon has a theoretical capacity about 10 times that of graphite, so it is expected to be one of the next-generation anode materials to further increase the capacity of batteries. However, silicon has a large volume change during charging and discharging, which result in poor cyclability. Although morphological change of silicon has been shown in a lot of previous studies, most of them are ex-situ observations using electron microscopes such as SEM and are two-dimensional observations1). Moreover, many previous studies target liquid battery. It is necessary to understand the expansion and shrinkage mechanism of silicon to improve all-solid-state battery performance using silicon anode. Synchrotron X-ray computed tomography (X-ray CT) is a technique that can measure the internal structure of a battery in three dimensions with micrometer-order spatial resolution in a short time. In addition, operando X-ray CT measurement is possible under charging and discharging in an all-solid-state battery2). In this study, we analyzed that morphological changes of silicon during charging and discharging by operando X-ray CT measurements.We used LiNi1/3Co1/3Mn1/3O2 (NCM), Li6PS5Cl (LPSCl) and acetylene black (AB), which were mortar-mixed in a mass ratio of 1:1:0.1 as the cathode composite material, and Si, LPSCl and AB in a mass ratio of 1:2.78:0.42 as anode composite material. Si｜LPSCl｜NCM all-solid-state cells were assembled. X-ray CT measurements at SPring-8 BL20XU using 20 keV X-rays while performing constant current charge/discharge measurement at 2.3×10-3 A cm-2. The pixel resolution was 0.5 µm. A silicon particle was extracted from the X-ray CT images obtained from X-ray CT measurements to observe the morphological changes of silicon during charging and discharging reaction. Then, change of the silicon volume and the contact area fraction of silicon particle and LPSCl solid electrolyte were calculated.Volume expansion was observed with lithiation of silicon and volume shrinkage with delithiation of silicon. As the lithiation process, silicon density decreased, and silicon was observed to be darker. As the delithiation process, cracks appeared in the silicon particle as the expanded silicon shrank. In addition, the silicon/solid electrolyte interface changed so that the silicon formed shell voids at the surface of silicon particles. This indicates that the plasticity of the LPSCl solid electrolyte cannot follow the form change of the interface. However, shell voids in the interface were formed for all directions, but some parts remained in contact area between the silicon particle and the solid electrolyte. After the second cycle of lithiation, cracks in the particle and the voids in the interface between the silicon particle and the solid electrolyte that had been formed due to the shrinkage of silicon as the delithiation disappeared by the re-lithiation. However, the re-delithiation caused cracks in the particle in the same area and formed shell voids in the interface again. Moreover, as the second delithiation process, the number of cracks in the particle increased compared with that as the first delithiation. This suggests that the number of cracks in the particle increases as silicon repeated lithiation and delithiation, and so silicon is miniaturized. In addition, a correlation was confirmed between the silicon volume change and the contact area fraction change. After the first cycle, the volume didn’t return to pristine silicon volume and the contact area fraction was reduced compared to pristine silicon. The isolation of the silicon particle from the solid electrolyte interface is suggested to be one of the factors causing the poor cycle performance because of the lithium ion reaction path is limited.1) T. Li, J. Y. Yang, S.G. Lu, H. Wang and H. Y. Ding, Rare Metals, 32, 299-304 (2013).2) Y. Sakka, H. Yamashige, A. Watanabe, A. Takeuchi, M. Uesugi, K. Uesugi and Y. Orikasa, J. Mater. Chem. A, 10, 16602–16609 (2022).

Development and Validation of a Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for Therapeutic Drug Monitoring of Ceftolozane and Tazobactam in Human Plasma Microsamples.

Ceftolozane/tazobactam (C-T) is a novel beta-lactam/beta-lactamase inhibitor combination approved for the treatment of various infections caused by difficult-to-treat Pseudomonas aeruginosa. In critically ill patients, C-T may exhibit significant pharmacokinetic variability, both between individuals and within individuals, warranting therapeutic drug monitoring for clinical purposes. We aim to develop and validate a novel and sensitive analytical method for concurrently determining C and T in human plasma microsamples (3μL). The method was developed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with positive electrospray ionization and multiple reaction monitoring (MRM) detection modes, employing specific mass transitions for both drugs. Sample preparation was simple, and the chromatographic run lasted only 4 minutes. Validation was conducted according to European Medicines Agency (EMA) guidelines, encompassing specificity, sensitivity, linearity, precision, accuracy, matrix effect, extraction recovery, limit of quantification, and drug stability. The validated method was applied to measure C and T in 32 plasma samples collected from critically ill patients with multidrug-resistant, gram-negative, bacterial infections. The method ensured accurate (BIAS% 2.1-9.6 for C and -2.2 to 15.2 for T) and precise intraday CV% for C: 6.7-5.5; for T: 1.3-8.9; interday CV% for C 6.0-10.8; for T 4.1-10.2) measurements of C-T over a wide concentration range (0.2-200.0 mg/L for C and 0.1-100.0 mg/L for T). Overall, the recovery at quality control concentration levels was high for both C and T (mean values: 90-91 for C and 89-92 for T). Analyte stability was satisfactory in both human plasma and extracts under various storage conditions. The clinical applicability of the assay was confirmed by the reliably quantifying C and T in clinical plasma samples. The developed and validated LC-MS/MS method is sensitive and suitable for monitoring C and T in human plasma microsamples.

Development of an Ion Mobility Spectrometer Based on a Pulsed Photoelectric Effect Ionization Source.

Ion mobility spectrometry (IMS) is a compact and sensitive trace gas analysis instrument that ionizes the sample into ions for detection. Typically, an ion gate is used to cut the continuous ion beam into ion packets for separation and detection. However, commonly used ion gates suffer from complex structures or low ion transmission rates, making the gateless IMS a viable alternative. In this study, an IMS based on a pulsed photoelectric effect ionization source was designed. The photoelectrons were generated by irradiating a photoelectric material with a back-illuminated pulsed xenon lamp. This allows for low-energy photoelectron generation and the production of simple reactant ions (O2-(H2O)n) and thus negative product ions. The photoelectron current generated by this ionization source was analyzed, which can reach an intensity of a few microamperes and can be converted into an ion signal exceeding 10 nA. The introduction of the pulsed photoelectric effect ionization source makes it possible to generate separate ion packets and complete ion injection when a constant electric field is maintained in the ionization region. And with an assisted pulsed electric field in the ionization region, the resolving power of the system can be effectively improved to 1.85 times that of the constant electric field. The IMS developed in this study was used for the detection of common volatile hazardous chemicals, yielding effective results. The detection limit for phenol was below 1 ppb, and the dynamic response range exceeded 1 order of magnitude, which implies the potential applications of this IMS to detect substances with high electron affinity, such as explosives detection in public safety.

Ultra-thin SnS2 nanosheets grown on carbon nanofibers with high-performance in sodium-ion energy storage

SnS2 with two-dimensional layered structure has great application promising in the energy storage system due to its super high theoretical capacity. However, the serious volume expansion and low intrinsic conductivity are difficult to meet the commercial application of SnS2 in sodium-ion batteries (SIBs). Herein, SnS2/CNF was successfully prepared by simple electrospinning technique and hydrothermal method. Based on the synergistic effect between ultra-thin nanosheets and carbon nanofibers (CNF), the anode material not only shortened the path of electron transport, but also accelerated the sodium ion reaction kinetics, thus showed outstanding stability and reversibility SIBs. The SnS2/CNF displayed the excellent rate properties (352 mAh g-1 at 5 A g-1) as well as stable long term cycle performance (338 mAh g-1 at 3 A g-1 after 500 cycles). Furthermore, the SnS2/CNF//AC sodium-ion hybrid capacitor (SIHCs) exhibits excellent energy density and power density of 97 Wh kg-1/54 W kg-1. The capacity retention is 81 % after 2500 cycles at 1 A g-1. The SIHCs could light up to 100 LEDs easily, which thus exhibited great practical application potential in energy storage device.

Simulation study of the effect of electrode polarity on microscale corona discharge characteristics

Abstract The occurrence and application scenarios of micro-scale corona discharge are diverse, and the effect of micro-scale corona discharge mechanism and needle electrode polarity on corona discharge characteristics is still unclear. This paper establishes a microscale simulation model of pin-plate DC positive and negative corona fluid chemical reactions. The phenomenon of positive and negative corona discharge is being investigated. The internal discharge mechanism is analyzed from the microscopic point of view. Results demonstrate that positive corona discharge generates space charges that reduce the electric field strength between the needle electrode and amplify it between the plate electrodes. In contrast, negative corona discharge exhibits the opposite effect. The number of charged particles produced by microscale negative corona discharge is larger than that produced by positive corona, and the discharge phenomenon is more intense than that of positive corona. Under the simulation conditions in this paper, the ionization reaction rate of micro-scale positive and negative corona rises rapidly at the initial discharge. It will gradually remain stable after experiencing an upward pulse. The pulse peak value generated by micro-scale negative corona discharge is much higher than that of positive corona, and the pulse width of negative corona discharge is about half smaller than that of positive corona, which can reach a stable corona discharge state faster.

Hydrosilylation of Dihydrosilylium Ion Stabilized by Coordination of a σ‐Donating Ni(0) Ligand

AbstractThe hydrosilylation reactions of dihydrosilylium ion 2, stabilized by coordination of a σ‐donating Ni(0) fragment, has been investigated. Complex 2 with two reactive sites, dihydrosilylium and Ni(0) centers, readily reacts with diphenylacetylene via a selective mono‐hydrosilylation reaction to afford the corresponding Ni(0)‐stabilized (hydro)(vinyl)silylium ion 6. In the case of ethylene, three equivalents of olefin are consumed to give a cationic Ni(II)‐complex 7 featuring a Bu‐Si+‐NiII‐Et moiety with a NHC‐supported Si atom. DFT calculations indicate that the hydrosilylation proceeds by a classical (Chalk‐Harrod type) mechanism with the assistance of NHC ligand moving between Si and Ni centers according to their stabilization requirements.

Nano-Reactors Based on Ovotransferrin Organic Skeleton through a Ferroptosis-like Strategy Efficiently Enhance Antibacterial Activity.

The issue of bacterial resistance is an escalating problem due to the misuse of antibiotics worldwide. This study introduces a new antibacterial mechanism, the ferroptosis-like death (FLD) of bacteria, and an approach to creating green antibacterial nano-reactors. This innovative method leverages natural iron-containing ovotransferrin (OVT) assembled into an organic skeleton to encapsulate low-concentration adriamycin (ADM) for synthesizing eco-friendly nano-reactors. FLD utilizes the Fenton reaction of reactive oxygen species and ferrous ions to continuously produce ·OH, which can attack the bacterial cell membrane and destroy the cell structure to achieve bacteriostasis. The OVT@ADM nano-reactors are nearly spherical, with an average diameter of 247.23 nm and uniform particle sizing. Vitro simulations showed that Fe3+ in OVT@ADM was reduced to Fe2+ by glutathione in the bacterial periplasmic space, which made the structure of OVT loose, leading to a sustained slow release of ADM from OVT@ADM. The H2O2 continuously produced by ADM oxidized Fe2+ through the Fenton reaction to produce ·OH and Fe3+. The results of the antibacterial assay showed that OVT@ADM had a satisfactory antibacterial effect against S. aureus, and the inhibition rate was as high as 99.3%. The cytotoxicity results showed that the mitigation strategy significantly reduced the cytotoxicity caused by ADM. Based on the FLD mechanism, OVT@ADM nano-reactors were evaluated and applied to bacteriostasis. Therefore, the novel antibacterial mechanism and OVT@ADM by the green synthesis method have good application prospects.

Performance evaluation of SILAR deposited Rb-Doped ZnO thin films for photodetector applications

ZnO-based photodetectors (PDs) compose a remarkable optoelectronic device field due to their high optical transmittance, electrical conductivity, wide band gap, and high binding energy. This study examined the visible light photodetector performance of the pristine and Rubidium (Rb)-doped ZnO thin films. The influence of Rb doping amount (2, 4, and 6 wt% in solution) on the electrical, optical, and structural properties of the ZnO-based thin films produced by the Successive Ion Layer Adsorption and Reaction (SILAR) technique was analyzed. Structural analyses showed that all peaks correspond to hexagonal wurtzite structure with no other peak from Rb-based phases, suggesting the high quality of the crystalline pristine and Rb-doped ZnO thin films. The morphology of the thin films shows homogenous layers formed of nanoparticles where particle size was first decreased and then increased with the increasing Rb doping according to Scanning Electron Microscope (SEM) morphology analysis. Besides that, Raman spectroscopy analyses indicate that the phonon lifetimes of the ZnO-based thin films slightly increased due to the improvement of the crystal quality with the increasing amount of Rb in the SILAR solution. Photosensor measurements of the nanostructured pristine and Rb-doped ZnO thin films were measured at different light power intensities under the visible light environment. Photosensor properties were examined depending on the doping amount and light power density. In light of the literature review, our study is the first to produce Rb-doped ZnO thin films via the SILAR method, which has a promising potential for photosensor applications.Graphical

Triboiontronics with temporal control of electrical double layer formation

The nanoscale electrical double layer plays a crucial role in macroscopic ion adsorption and reaction kinetics. In this study, we achieve controllable ion migration by dynamically regulating asymmetric electrical double layer formation. This tailors the ionic-electronic coupling interface, leading to the development of triboiontronics. Controlling the charge-collecting layer coverage on dielectric substrates allows for charge collection and adjustment of the substrate-liquid contact electrification property. By dynamically managing the asymmetric electrical double layer formation between the dielectric substrate and liquids, we develop a direct-current triboiontronic nanogenerator. This nanogenerator produces a transferred charge density of 412.54 mC/m2, significantly exceeding that of current hydrovoltaic technology and conventional triboelectric nanogenerators. Additionally, incorporating redox reactions to the process enhances the peak power and transferred charge density to 38.64 W/m2 and 540.70 mC/m2, respectively.

Medically relevant radioisotope production through low energy heavy ion reactions

Medically relevant radioisotope production through low energy heavy ion reactions

Hydrochemical and Formation Mechanism Studies of Groundwater in Quaternary Aquifer in a Northern Plain of China: An Example of Beijing Plain

Beijing Plain is a very active part of Beijing city regarding the socio-economic and human activities of the region. Over the past four decades, Beijing’s economic development and the continuous drought for nearly 10 years in the 2000s have negatively impacted the groundwater quantity and quality. Therefore, it is necessary to investigate the present situation of groundwater chemistry in this region to develop a comprehensive database and orientation for future research on groundwater quality evaluation. Mathematical statistics, Piper’s trilinear diagram, Gibbs plots, the ion ratio method and PHREEQC software 3.7.3 were used to analyze the groundwater hydrogeochemical characteristics and formation mechanisms of the quaternary aquifers of the Beijing Plain area. Hydrogeochemical results indicated that the groundwater is slightly alkaline, with pH values ranging from 6.76 to 8.65 and an average value of 7.92. The order of major cations in groundwater was Ca2+ > Na+ > Mg2+ > K+ with average values of 66.54 mg/L, 50.58 mg/L, 23.78 mg/L, and 1.81 mg/L, respectively, while the order of major anions was HCO3− > SO42− > Cl− with average values of 284.89 mg/L, 52.1 mg/L and 35.5 mg/L, respectively. The groundwater chemical types are Mg-Ca-Cl-HCO3, Na-Ca-HCO3, Mg-Ca-HCO3 and Mg-Na-HCO3. Research on the main influencing factors and PHREEQC hydrogeochemical inverse simulations results along the four pathways selected confirmed that rock weathering with sulfate, silicate and carbonate rock mineral dissolution and Na+, Mg2+ and Ca2+ ion reaction exchange influenced groundwater hydrogeochemical characteristics of the quaternary aquifers of the Beijing Plain area. Understanding the formation mechanisms of hydrogeochemistry in quaternary plains provides guidance for future studies and, through suggestions and case studies, facilitates decision-making by policy-makers on the sustainable management of groundwater resources.

Synthesis of gold nanoparticles coated with glucose oxidase using PVP as passive adsorption linkage

Gold nanoparticles (AuNPs) have great potential as biosensors for glucose detection due to their high sensitivity, as well as their extraordinary physical and chemical properties that improve compatibility with different biorecognition molecules, such as glucose oxidase (GOx). In this work the D-glucose quantification was determined by using the traditional technique based on biochemical reaction of GOx and AuNPs functionalized with polyvinylpirrolidone (PVP) polymer and the enzyme. The AuNPs-PVP-GOx nanocomplexes were characterized by ultraviolet-visible (UV-Visible), Infrared (FTIR), and Raman spectroscopies, as well as scanning electron microscopy (SEM), Z potential, dynamic light scattering (DLS), and thermogravimetry analysis (TGA). In general, these techniques showed significant differences after each functionalization stage with PVP and GOx, for instance it was observed: the presence of different functional groups, an increase of hydrodynamic diameter from 48.60 to 198.77 nm, a shift of the band absorption to larger wavelength, a change in the surface potential and weight loss, and in the morphology of the nanocomplex, which confirm the functionalization. In addition, the enzymatic activity of the AuNPs-PVP-GOx was confirmed through the detection of triiodide ions by UV-Visible spectrophotometry, coming from the oxidation reaction of iodide ions in the presence of H2O2. Furthermore, the nanocomplex synthesized by passive adsorption was evaluated as a possible biosensor for the quantification of D-glucose using a colorimetric assay, obtaining greater sensitivity than the traditional method. These findings indicate that PVP can be used as a linkage medium between AuNPs and GOx, which in turn can be used as a biosensor for the detection of D-glucose at low concentrations in biological fluids.

Using dopants in the atmospheric pressure chemical ionization ion source to determine the site of protonation by ion mobility spectrometry.

Compounds like caffeine metabolites with more than one proton acceptor site can produce a mixture of isomeric protonated ions (protomers) in electrospray ionization and atmospheric pressure chemical ionization (APCI) ion sources. Discrimination between the protomers is of interest as the charge location influences ion structure and chemical and physical properties. Protonation of caffeine in an APCI ion source was studied using ion mobility spectrometry. The hydronium ions, H3O+(H2O)n, are the main reactant ions in the APCI ion source. Different dopant gases including NO2, NH3, and CH3NH2 were used to produce new reactant ions NO+, NH4 +, and CH3NH3 +, respectively. Density functional theory was employed to explain the experimental results and calculate the energies of the ionization reactions. The ion mobility spectrum of caffeine showed three peaks. In the presence of NO2 dopant and NO+ reactant ion, caffeine was ionized via charge transfer and formation of M+ ion. As NH3 and CH3NH2 are stronger bases than H2O, the reactant ions NH4 + and CH3NH3 + selectively protonated the more basic site of caffeine, that is, the imidazole nitrogen. Using these dopants, we could attribute the first ion mobility peak to M+ ion, the second peak to the protonation of caffeine at the carbonyl oxygen atom, and the third peak to the protonation of the imidazole nitrogen atom. The calculated collisional cross-sections of M+ and the protomers of caffeine confirmed the peaks' assignment. The criterion for the selection of an appropriate dopant is that its proton affinity (PA) should be between those of the proton acceptor sites of the molecule studied.

On the Arrival Time Distribution of Reacting Systems in Ion Mobility Spectrometry.

Ion mobility spectrometry (IMS) is a widely used gas-phase separation technique, particularly when coupled with mass spectrometry (MS). Modern IMS instruments often apply elevated reduced field strengths for improved ion separation and ion focusing. These alter the collision dynamics and further drive ion reaction processes that can change the analyte's structure. As a result, the measured arrival time distribution (ATD) can change with the applied reduced field strengths. In this work, we systematically study how the ion collision dynamics and the ion reaction dynamics, as a function of the reduced field strength, can alter the ATD. To this end, we investigate 2,6-di-tert-butylpyridine, methanol, and ethyl acetate using a home-built drift tube IMS coupled to a home-built MS and extensive first-principles Monte Carlo modeling. We show how elevated reduced field strengths can actually lower resolving power through increased ion diffusion and how the field dependency of the ion mobility can introduce uncertainties to collision cross sections (CCS) calculated from the measured mobilities. On top of the collision dynamics, we show how chemical transformation processes that alter the analyte's CCS, e.g., dynamic clustering or fragmentation, can lead to broadened, shifted, or non-Gaussian ATDs and how sensitive these processes are to the applied field strengths. We highlight how first-principles ion dynamics simulations can help to understand and even harness the mentioned effects.

Rearrangement, Elimination, and Ring-Opening Reactions of Cyclopropyl-Substituted Nitrenium Ions: A Computational and Experimental Investigation.

N-(4-Biphenylyl)-N-cyclopropyl nitrenium ion 5 and N-benzyl-N-cyclopropyl nitrenium ion (6) were generated through photolysis of their corresponding N-aminopyridinium ion photoprecursors. In the case of 5, stable products result from a combination of cyclopropyl ring expansion (N-biphenylazetium ion) and ethylene elimination (biphenylisonitrilium ion). When present in high concentrations, methanol can add to the cyclopropyl ring-forming N-3-methoxypropyl-N-biphenyl iminium ion. In contrast, the only detectable product from the N-benzyl-N-cyclopropyl nitrenium ion (6) is benzylisonitrile, resulting from the elimination of ethylene. Density functional theory (DFT) calculations predict the product distributions from the more stable biphenyl system 5 with reasonable accuracy. However, product distributions from the less stable benzyl system 6 are forecast with less accuracy.

Modeling and simulation of laser-ignited Al-PTFE reactive material in vacuum

Despite extensive investigations elucidating the initial response behavior of aluminized polytetrafluoroethylene (Al-PTFE) under atmospheric pressure, research on their response in lean-oxygen environments pertinent to propulsion and explosion scenarios is still lacking. This paper theoretically analyzes the multi-physical processes of laser-ignited Al-PTFE, identifying the initial response, main chemical reaction paths, and gas-phase product flow mechanisms. A dynamic reaction model of Al-PTFE considering material moving front, chemical reactions, gas-phase product dynamics, and variations in thermophysical properties, was developed. The robust coupling scheme in the model addresses nonlinear equations and fluid-solid coupling boundary conditions. Validation was achieved by comparing the ablation depth and plume number density field calculated by the model with the experimental results in the literature. The model reveals a positive correlation between laser fluence and both temperature growth rate and ablation depth of Al-PTFE, with the effects mainly observed in the full width at half maximum (FWHM) of the pulsed laser due to the thermal decomposition of the PTFE matrix. Simulations of the equilibrium constants and molar fractions of 19 components in the Al-PTFE ablation plume within the temperature range of 2000 K to 30,000 K at 0.001 Pa indicate that the equilibrium constants for dissociative reactions exceed those for ionization reactions, primarily in the early plume formation stages. Analysis of kinetic parameters and ambient pressure effects shows that during laser ablation, the maximum temperature of the plume initially appears near the ablation surface, shifting to the front, where the maximum velocity is always located. An elliptical shock wave forms due to adiabatic expansion of the plume, creating a cavity inside the plume. Lower ambient pressure increases plume expansion velocity, temperature, and size.

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

Improved high-performance liquid chromatography tandem mass spectrometry method for quantification of infliximab in pediatric plasma and its application in therapeutic drug monitoring.

The application of infliximab (IFX) to immune-mediated disease is limited by the significant individual variability and associated clinical nonresponse, emphasizing the importance of therapeutic drug monitoring (TDM). Because of the cross-reactivity, limited linear range, and high costs, the clinical application of the previous reported methods was limited. Here, an improved high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method was developed to address the issues. This study developed an improved bioanalytical HPLC-MS/MS method coupling nanosurface and molecular-orientation limited proteolysis technology. The commercially available compound P14R was selected as the internal standard. This method was developed with fewer volume of reagents and was thoroughly validated. The validated method was applied to TDM in pediatric inflammatory bowel disease (IBD). Chromatography was performed using a Shim-pack GISS-HP C18 metal-free column (3 μm, 2.1 × 100 mm) with a gradient elution of 0.1% formic acid in water and acetonitrile at 0.4 mL/min. Detection and quantitation were performed using electrospray ionization (ESI) and multiple reaction monitoring in the positive ion mode. The method was validated to demonstrate its selectivity, linearity, accuracy, precision, recovery, matrix effect, and stability. The method exhibited a linear dynamic range of 0.3-100 μg/mL, with intra- and inter-day precision and relative errors below 15%. The recovery and matrix effect were measured as 87.28%-89.72% and 41.98%-67.17%, respectively, which were effectively compensated by the internal standard. A total of 32 samples collected from 24 pediatric patients with IBD were analyzed using the validated method, and only 46.9% achieved the reported targeted trough level. This study developed an improved HPLC-MS/MS method for the quantitative determination of IFX concentration in human plasma. The accurate, reliable, and cost-effective method was validated and utilized in the analysis of clinical samples. The results confirmed the importance of TDM on IFX and the clinical application prospects of the improved method.