H2O Ions Research Articles

The Determination of Free Energy of Hydration of Water Ions from First Principles.

We model the autoionization of water by determining the free energy of hydration of the major intermediate species of water ions. We represent the smallest ions─the hydroxide ion OH-, the hydronium ion H3O+, and the Zundel ion H5O2+─by bonded models and the more extended ionic structures by strong nonbonded interactions (e.g., the Eigen H9O4+ = H3O+ + 3(H2O) and the Stoyanov H13O6+ = H5O2+ + 4(H2O)). Our models are faithful to the precise QM energies and their components to within 1% or less. Using the calculated free energies and atomization energies, we compute the pKa of pure water from first principles as a consistency check and arrive at a value within 1.3 log units of the experimental one. From these calculations, we conclude that the hydronium ion, and its hydrated state, the Eigen cation, are the dominant species in the water autoionization process.

Maillard reaction: formation, advantage, disadvantage and control. A review

The Maillard reaction (MR) is often known as the amino-carbonyl reaction, nonenzymatic browning, or protein glycation reaction. The non-enzymatic browning reaction is influenced by several factors like period, quantity of H2O, temperature, involved reactants, pH, and metal ions in food. During the production, processing, and storage of food, the MR is a crucial chemical process. While Maillard reaction products (MRPs) can enhance food quality during processing, some unfavorable reactions can also result in undesirable food effects. There are two sides to MRPs. The positive side is that these products have several advantages such as improvement in color, odor, flavor, and antioxidant ability. On the other hand, the negative side represents decreasing food quality and the nutritional value of some foods, as well as some health-related problems. The review involves several strategies by which MR could be controlled or prevented. These strategies were divided into two parts, the first is non-enzymatic which is done by adding functional ingredients that work to modify reducing sugars and amino groups and/or trapping of α-dicarbonyl compounds. The second is enzymatic, by using enzymes for example, fructosamine kinase, fructosamine oxidase, and lactose oxidase.

جسيمات النحاس النانوية المركبة في مصفوفة البوليمر الحيوي وتطبيقاتها في النشاط المضاد للبكتيريا

النحاس هو بديل أرخص من العديد من المعادن النبيلة مع مجموعة من التطبيقات المحتملة في مجال علم النانو وتكنولوجيا النانو. ومع ذلك ، فإن جسيمات النحاس النانوية لها قيود كبيرة ، والتي تشمل الأكسدة السريعة عند التعرض للهواء. لذلك ، تم تطوير مسارات بديلة لتجميع الجسيمات النانوية المعدنية في وجود البوليمرات والمواد الخافضة للتوتر السطحي كمثبتات ، ولتشكيل الطلاءات على سطح الجسيمات النانوية. هذه المواد الخافضة للتوتر السطحي والروابط البوليمرية مصنوعة من بتروكيماويات غير متجددة. نظرًا لمحدودية الموارد الأحفورية ، فإن إيجاد بديل متجدد وقابل للتحلل البيولوجي يعد أمرًا واعدًا ، حيث هدفت الدراسة إلى إعداد وتوصيف وتقييم الخصائص المضادة للبكتيريا لجسيمات النحاس النانوية. تم تحضير جسيمات النحاس النانوية باستخدام البوليمر الحيوي الجيلاتيني ، أيونات CuSO4.5H2O والهيدرازين كمثبت ، ملح سلائف وعامل اختزال على التوالي. ومع ذلك ، تم استخدام محلول فيتامين C و NaOH أيضًا كمضاد للأكسدة وضبط درجة الحموضة. تم تمييز جسيمات النحاس النانوية المركبة باستخدام التحليل الطيفي المرئي للأشعة فوق البنفسجية (UV-vis) ، التحليل الحراري الوزني (TGA) ، مسحوق قياسات زيتا المحتملة ، حيود الأشعة السينية (XRD) ، المجهر الإلكتروني لمسح الانبعاث الميداني والمجهر الإلكتروني النافذ (TEM). يؤكد طيف الامتصاص المرئي للأشعة فوق البنفسجية تكوين CuNPs ، والتي أظهرت أقصى امتصاص عند 583 نانومتر. أشارت النتائج التي تم الحصول عليها من TEM إلى انخفاض في حجم الجسيمات من التركيز المنخفض إلى التركيز العالي للمواد الداعمة. وجد أن التركيز الأمثل للجيلاتين هو 0.75٪ بالوزن. المواد الداعمة المستخدمة في هذا التركيب متوافقة حيوياً والمنتجات التي تم الحصول عليها مستقرة في الهواء. تُظهر CuNPs المُصنَّعة أنشطة واعدة مضادة للجراثيم ضد B. subtilis (B29) و S. aureus (S276) و S. choleraesuis (ATCC 10708) و E. coli (E266) كبكتيريا موجبة وسالبة الجرام على التوالي.

Component Fluctuation Modulated Gelation Effect Enable Temperature Adaptability in Zinc‐Ion Batteries

AbstractThe active H2O and slow ion kinetics behavior deteriorate the performance of aqueous zinc‐ion batteries at a wide temperature range, even in hydrogel electrolyte. Herein, a component fluctuation modulated gelation effect is applied to optimize Zn2+ solvation structure, realizing a balance between H2O activity limitation and Zn2+ kinetics retention. The as‐prepared hydrogel electrolyte via in situ copolymerization of [2‐(methacryloyloxy)ethyl] dimethyl‐(3‐sulfopropyl) and acrylamide in the electrolyte salt matrix facilitates stable overall performance at both normal and low temperatures. Theoretical calculations and experimental results attest that polymer functional groups exhibit a higher efficacy in substituting bound water in the Zn2+ solvated shell with the polymer content increasement, thereby alleviating water‐associated parasitic reactions. Furthermore, the hydrogel with abundant zwitterionic groups not only interacts with H2O to limit hydrolysis, but also constructs separated ionic migration channels to promote uniform and fast Zn2+ transport. As a result, the hydrogel electrolytes promote stable Zn2+ plating/stripping behaviors over 1050 h and 3000 h at 25 and −20 °C, respectively. The full batteries achieve a capacity retention of 98.8% over 2000 cycles at 25 °C and stably cycle for 600 times at −20 °C. This work yields novel insights into the development and design of hydrogel electrolytes.

Application of a novel numerical simulation to biochemical reaction systems.

Recent advancements in omics and single-cell analysis highlight the necessity of numerical methods for managing the complexity of biological data. This paper introduces a simulation program for biochemical reaction systems based on the natural number simulation (NNS) method. This novel approach ensures the equitable treatment of all molecular entities, such as DNA, proteins, H2O, and hydrogen ions (H+), in biological systems. Central to NNS is its use of stoichiometric formulas, simplifying the modeling process and facilitating efficient and accurate simulations of diverse biochemical reactions. The advantage of this method is its ability to manage all molecules uniformly, ensuring a balanced representation in simulations. Detailed in Python, NNS is adept at simulating various reactions, ranging from water ionization to Michaelis-Menten kinetics and complex gene-based systems, making it an effective tool for scientific and engineering research.

An ICT-based highly fluorescent isoquinoline scaffold for selective Hg(II) detection in real-water samples: Development of a smart, low-cost RGB-Arduino electronic platform

Selective detection and quantification of Hg2+ ions is crucial to minimize health and environmental risks. Fluorescent organic small-molecule probes have been expeditiously utilized owing to their unique set of improved properties. However, isoquinoline core has not been extensively explored as a fluorescence platform partly due to synthetic challenges. Herein, a serendipitously discovered synthetic route to access a small yet highly functionalized novel isoquinoline-based probe, IQ is reported. The synthesis is achieved through the in-situ generation of ammonia, followed by intermolecular [5C + 1 N] aza-annulation reaction with a ketendithioacetal-based precursor, P-IQ. IQ displayed excellent recognition ability towards Hg2+ ions in H2O:ACN (99:1, v/v) via ICT-off fluorescent quenching behavior. Comparative FT-IR, 1H/13C NMR, mass spectral studies, and DFT analyses were carried out to validate the suggested mechanisms. Reversible studies confirm the secondary recognition effect of in-situ generated (IQ + Hg2+) complex on cysteine. The binding constant and LOD were estimated to be 3.7 × 104 M−1 and 0.86 µM, respectively. Further, IQ was utilized to evaluate the mercury ion content in real water samples demonstrating its effectiveness in water quality monitoring. The practical utility of IQ was further explored by developing TLC strips, Whatman filter-paper strips, and a low-cost, portable Arduino-based platform. Arduino microcontroller is interfaced with an RGB sensor to detect color changes and quantify mercury concentration w.r.t. RGB values.

Nanopore rigidity as an atomic descriptor of ion-transfer kinetics in sieving membranes: Insights from two-dimensional g-C3N4

Kinetics of ions play a crucial role in the performance of materials for a wide range of applications, including solid electrolytes, fuel cells, and sieving membranes. However, establishing a quantitative correlation between microscopic characteristics of a material and kinetics of conducting species inside remains a major challenge. Combining first-principles and metadynamics methods, we investigate sieving behavior of two-dimensional graphitic carbon nitride (g-C3N4) for various species (H+, Na+, K+, and Cl−). We reveal that mechanism of proton conduction changes with a pore size of carbon-nitrogen ring in g-C3N4: varying from a pure H+ transportation when crossing narrow pores into a dual pathways (via both H+ and hydronium ions H3O+) when transmitting across wide pores. We introduce a novel local descriptor, nanopore rigidity (C), to quantify the rigidity of a material and relate the dynamics of sieving species to mechanics of the pore. The kinetic barrier of an arbitrary intercalating ion (ΔGion) can then be obtained via ΔGion=Cδρ2+B with B being a residual barrier of the pore and δρ being the local strain of the pore induced by the conducting ion. The descriptor as a microscopic metric can be extended to other porous materials, allowing a screening for electrochemical energy transition materials.

Identification of strong field ionization of H[formula omitted]O via electron emission from lower-lying molecular orbitals using rotational wave packet dynamics

We examine rotational wave packet dynamics of an asymmetric top, H2O, by calculating the time-dependent expectation values of the squared directional cosines with respect to three molecular a, b and c axes. From comparison between the Fourier transform spectra of these expectation values and that of the pump-probe delay dependent H2O+ yield recorded in our previous study (Kikuchi et al., 2023), we reveal that electrons are mainly emitted from the highest-occupied 1b1 orbital but are also emitted from lower-lying 3a1 orbital in the ionization of H2O in an intense laser field.

Early and Transient Formation of Highly Acidic pH Spikes in Water Radiolysis under the Combined Effect of High Dose Rate and High Linear Energy Transfer

(1) Background: Water radiolysis leads to the formation of hydronium ions H3O+ in less than 50 fs, resulting in the formation of transient acidic pH spikes in the irradiated water. The purpose of this study is to examine the time evolution of these spikes of acidity under irradiation conditions combining both high absorbed dose rate and high-LET radiation. (2) Methods: The early space–time history of the distributions of the various reactive species was obtained using our Monte Carlo multitrack chemistry simulation code IONLYS-IRT. To simulate different LETs, we used incident protons of varying energies as radiation sources. The “instantaneous pulse” (or Dirac) model was used to investigate the effect of dose rate. (3) Results: One major finding is that the combination of high dose rates and high LETs is clearly additive, with a very significant impact on the pH of the solution. For example, at 1 ns and for a dose rate of ~107 Gy/s, the pH drops from ~4.7 to 2.7 as the LET increases from ~0.3 to 60 keV/μm. (4) Conclusions: Confirming previous work, this purely radiation chemical study raises the question of the possible importance and role of these spikes of acidity in underpinning the physical chemistry and biology of the “FLASH effect”.

The Atomic Arrangement of the Sherwoodite Structural Unit: Redefinition of the Sherwoodite Vanadoaluminate Heteropoly Complex as [AlV4+V5+12O39]11−

Abstract Sherwoodite, putatively Ca4.5(AlV5+12V4+2O40)·28H2O, was among the early naturally occurring polyoxometalates to be reported from the Uravan Mineral Belt; the ideal formula of sherwoodite is here redefined as Ca5.5[AlV4+V5+12O39]·28H2O. In an earlier preliminary structure report (R = 22%), researchers defined the composition of vanadoaluminate heteropoly complex in sherwoodite as (AlV4+,5+14O40)n−, the first natural occurrence of that polyoxometalate cluster. The cluster forms a framework around intermolecular channels that contain disordered arrays of H2O and charge-balancing Ca ions. A detailed structure study described herein [a = 27.9085(7), c = 13.8090(5), space group I41/amd, R1 < 6%] reveals new details of the vanadoaluminate heteropoly complex, indicating that it crystallizes as a structural variant of the putative (AlV4+,5+14O40)n− vanadoaluminate complex, [AlV4+V5+12O39]11−. That variant is derived through the random removal of one of the two apical vanadate octahedra, elucidating the cause of difficulties in the refinement of the preliminary structure report. The [AlV4+V5+12O39]11− complex is capped on one end by a Ca atom that bonds to four octahedral apices in a half-occupied site, and on the opposite end by the V1 and O1 atoms in half-occupied sites, similar to the compound potassium 13-vanadanomangate(IV). The capping octahedron is the locus of the V4+ ions in the mixed-valence complex. New electron microprobe analyses yielded an empirical formula, on the basis of (V4+V5+12), of (Ca4.26Mg1.09Na0.35K0.04Sr0.03)[Al0.87(V4+V5+12)O39]·28.15 H2O.

The Effect of Air Injection for Formation of Radicals in Liquid Glow Discharge Plasma Electrolysis with K2SO4 Solution

Glow discharge is part of the phenomenon of plasma formation on the electrode side in contact with the electrolyte solution and begins with an electrolysis reaction with direct electric current. In this research, 0.02 M K2SO4 electrolyte was used, the anode in the form of tungsten and stainless steel for the cathode in a direct current plasma electrolysis reactor. The phenomenon of plasma formation is explained using a strong current and voltage characteristic curve. There are three plasma formation zones: the ohmic zone, the transition zone and the glow discharge plasma zone. Air injection affects the formation of glow discharge plasma and radicals. Without the injection of air, radicals formed only •OH, •H and •O with emission intensities of 20012 a.u, 10121 a.u and 10245 a.u. Air injection 0.8 L men-1 produced radicals •OH, •N, •N2*, •N2+, •H and •O with emission intensities of 30863a.u, 20139 a.u, 28540 a.u, 18023 a.u, 12547 a.u and 49800 a.u. Many radicals are generated when the plasma reaches stability. The plasma is dominated by H2O ionization, and the plasma is more stable if formed in the gas phase. Other results from this research at 0 L men-1, 0.2 L men-1, 0.4 L men-1 and 0.8 L men-1 stable plasma were formed at 675 V, 660 V, 650 V and 650 V. The plasma that can be seen from the bright light, the injection of air accelerates the formation of a gas envelope to reduce energy.

Manipulation of Ion Conversion in Dichloromethane-Enhanced Vacuum Ultraviolet Photoionization Mass Spectrometry of Oxygenated Volatile Organic Compounds.

The ion conversion processes in CH2Cl2-enhanced vacuum ultraviolet photoionization of oxygenated volatile organic compounds (OVOCs) have been systematically studied by regulating the pressure, humidity, and reaction time in the ionization source of a time-of-flight mass spectrometer. As the ionization source pressure increased from 100 to 1100 Pa, the main characteristic ions changed from CH2Cl+ to CH2Cl+(H2O), CH2OH+, and C2H4OH+ and then to the hydrated hydronium ions H3O+(H2O)n (n = 1, 2, 3). The total ion current (TIC) almost remained unchanged even if the humidity increased from 44 to 3120 ppmv, indicating interconversion between ions through ion-molecule reactions. The intensity of protonated methanol/ethanol (sample S) ion was almost linearly correlated with the intensity of H3O+(H2O)n, which pointed to the proton transfer reaction (PTR) mechanism. The reaction time was regulated by the electric field strength in the ionization region. The intensity variation trends of different ions with the reaction time indicated that a series of step-by-step ion-molecule reactions occurred in the ionization source, i.e., the primary ion CH2Cl+ reacted with H2O and converted to the intermediate product ions CH2OH+ and C2H4OH+, which then further reacted with H2O and led to the production of H3O+, and finally, the protonated sample ion SH+ was obtained through PTR with H3O+, as the ion-molecule reactions progressed. This study provides valuable insights into understanding the formation mechanism of some unexpected intermediate product ions and hydrated hydronium ions in dopant-enhanced VUV photoionization and also helps to optimize experimental conditions to enhance the sensitivity of OVOCs.

Zinc(II)-Based Ring-and-Rod Coordination Layer as an Excitation-Wavelength-dependent Dual-Emissive Chemosensor for Discriminating Fe3+, Cr3+, and Al3+ in Water.

The reactions of Zn(NO3)2, 3,6-bis(pyridin-3-yl)-9H-carbazole (bpycz), and 2,5-dihydroxyterephthalic acid (H4dhbdc) or 2-bromoterephthalic acid (Br-1,4-H2bdc) under hydro(solvo)thermal conditions yielded corresponding coordination polymers (CPs) {[Zn(H2dhbdc)(bpycz)]•0.5H2O}n (1) and [Zn(Br-1,4-bdc)(bpycz)]•2DMAc•H2O (2), respectively, with high thermal stability approaching 350 °C. CP 1 adopts a ring-and-rod layer structure, which is topologically described as a 4-connected net with the point symbol of 2•65. Two layers are interpenetrated in parallel interlocking mode to form a double 2D → 2D polyrotaxane entanglement with extra-framework void space of 19.6%. CP 2 has a non-interpenetrating ring-and-rod layer structure of 4-connected 2•65 net topology, with extra-framework void space of 16.6%. Thermally activated 1 and 2 revealed CO2 uptakes of 101.1 and 98.6 cm3 g-1, respectively, at P/P0 = 1 and 195 K. X-ray powder diffraction (XRPD) patterns confirmed that 1 and 2 both possessed high chemical stability in H2O, CH3OH, acetone, and DMF, and framework stability during gas adsorption-desorption. The H2O suspension of 1 displayed excitation-dependent dual-emissive properties, appearing at 432 nm upon excitation at 300 nm and at 528 nm upon excitation at 365 nm. Of note, 1 was capable of detection of Fe3+, Cr3+, and Al3+ ions in H2O, showing good anti-interference ability, excellent selectivity, and high sensitivity. More interesting, the dual-emissive properties make 1 to be an excellent luminescence chemosensor to screen Fe3+, Cr3+, and Al3+ from a pool of metal ions in H2O upon excitation at 300 nm via luminescence quenching effect and then discriminate Fe3+, Cr3+, and Al3+ upon excitation at 365 nm via luminescence quenching, unaltered, and enhancement responses, respectively. On the other hand, the H2O suspension of 2 demonstrated an excitation-independent emission appearing at around 430 nm, which could be utilized to sensitively detect Fe3+ and Cr3+ ions with good anti-interference ability and excellent selectivity via luminescence quenching effect. Further, 1 and 2 were recyclability and possessed cycling stability. The plausible sensing mechanisms for 1 and 2 toward Fe3+, Cr3+, and Al3+ were also explored in detail.

Spectroscopic and TD-DFT studies on the chromo-fluorogenic detection of cyanide ions in organic and aquo-organic media

A new naked-eye chromogenic and fluorogenic probe KS5 has been developed for the detection of CN– ions in neat DMSO and H2O:DMSO (1:1 v/v) media. The probe KS5 exhibited selectivity towards CN– and F− ions in organic and high selectivity towards CN– ions in aquo-organic media resulting in a colour change from brown to colourless and a turn-on fluorescence response. The probe could able to detect CN– ions via a deprotonation process, which was conceived by consecutive addition of hydroxide and hydrogen ions and confirmed using 1H NMR studies. The limit of detection (LOD) of KS5 towards CN– ions were in the range of 0.07–0.62 µM in both these solvent systems. Suppression of intra-molecular charge transfer (ICT) transition and photoinduced electron transfer (PET) process of KS5 by the added CN– ions are responsible for the chromogenic and fluorogenic changes observed, respectively. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations strongly supported the proposed mechanism along with the optical properties of the probe before and after the addition of CN– ions. To prove the practical applicability, KS5 was successfully utilized to detect CN– ions in cassava powder and bitter almonds as well as to determine CN– ions in various real water samples.

Multi-Step Nucleation of A Crystalline Silicate Framework via A Structurally Precise Prenucleation Cluster.

Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of open framework lattices such as zeolites and metal-organic frameworks, pre-organized multi-ion "secondary building units" (SBUs) have long been proposed as fundamental building blocks of the forming crystals. However, detailing the progress of multi-step reaction mechanisms in going from monomeric species to stable crystals and defining the structures of the intermediate SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q38polyanions formed through cross-linking and polymerization of smaller silicate monomers and other oligomers. These Q38 are stabilized by hydrogen bonds with surrounding H2O and tetramethylammonium ions (TMA+). When Q38 levels reach a threshold of~32% of the total silicate species nucleation within these clathrates occurs. Further growth proceeds through the incorporation of [(TMA)x(Q38)·nH2O](x-8) clathrate complexes into step edges on the crystals. These findings provide a clear picture of the multi-step nucleation process by which SBUs build a framework silicate lattice with implications for the synthesis of both functional materials and natural minerals.

Multi‐Step Nucleation of a Crystalline Silicate Framework via a Structurally Precise Prenucleation Cluster

AbstractHierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal–organic frameworks, pre‐organized multi‐ion “secondary building units” (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi‐step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small‐angle X‐ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q38 polyanions formed through cross‐linking and polymerization of smaller silicate monomers and other oligomers. These Q38 are stabilized by hydrogen bonds with surrounding H2O and tetramethylammonium ions (TMA+). When Q38 levels reach a threshold of ≈32 % of the total silicate species, nucleation occurs. Further growth proceeds through the incorporation of [(TMA)x(Q38)⋅n H2O](x−8) clathrate complexes into step edges on the crystals.

Selective Reagent Ion-Time-of-Flight-Mass Spectrometric Investigations of the Intravenous Anaesthetic Propofol and Its Major Metabolite 2,6-Diisopropyl-1,4-benzoquinone

The first detailed selected reagent ion-time-of-flight-mass spectrometric fundamental investigations of 2,6-diisopropylphenol, more commonly known as propofol (C12H18O), and its metabolite 2,6-diisopropyl-1,4-benzoquinone (C12H16O2) using the reagent ions H3O+, H3O+.H2O, O2+• and NO+ are reported. Protonated propofol is the dominant product ion resulting from the reaction of H3O+ with propofol up to a reduced electric field strength (E/N) of about 170 Td. After 170 Td, collision-induced dissociation leads to protonated 2-(1-methylethyl)-phenol (C9H13O+), resulting from the elimination of C3H6 from protonated propofol. A sequential loss of C3H6 from C9H13O+ also through collision-induced processes leads to protonated phenol (C6H7O+), which becomes the dominant ionic species at E/N values exceeding 170 Td. H3O+.H2O does not react with propofol via a proton transfer process. This is in agreement with our calculated proton affinity of propofol being 770 kJ mol−1. Both O2+• and NO+ react with propofol via a charge transfer process leading to two product ions, C12H18O+ (resulting from non-dissociative charge transfer) and C11H15O+ that results from the elimination of one of the methyl groups from C12H18O+. This dissociative pathway is more pronounced for O2+• than for NO+ throughout the E/N range investigated (approximately 60–210 Td), which reflects the higher recombination energy of O2+• (12.07 eV) compared to that of NO+ (9.3 eV), and hence the higher internal energy deposited into the singly charged propofol. Of the four reagent ions investigated, only H3O+ and H3O+.H2O react with 2,6-diisopropyl-1,4-benzoquinone, resulting in only the protonated parent at all E/N values investigated. The fundamental ion-molecule studies reported here provide underpinning information that is of use for the development of soft chemical ionisation mass spectrometric analytical techniques to monitor propofol and its major metabolite in the breath. The detection of propofol in breath has potential applications for determining propofol blood concentrations during surgery and for elucidating metabolic processes in real time.

Analysis of new particle formation events and comparisons to simulations of particle number concentrations based on GEOS-Chem–advanced particle microphysics in Beijing, China

Abstract. Aerosol particles play important roles in air quality and global climate change. In this study, we analyze the measurements of particle size distribution from 12 March to 6 April 2016 in Beijing to characterize new particle formation (NPF) using the observational data of sulfuric acid, meteorological parameters, solar radiation, and the mass concentration of fine particles (PM2.5, particulate matter with diameters less than 2.5 µm). During this 26 d campaign, 11 new particle formation events are identified with obvious bursts of sub-3 nm particle number concentrations and subsequent growth of these nucleated particles. It is found that sulfuric acid concentration in Beijing does not have a significant difference between NPF event and non-event days. Low relative humidity (RH) and high daily total solar radiation appear to be favorable for the occurrence of NPF events, which is quite obvious in this campaign. The simulations using four nucleation schemes, i.e., H2SO4–H2O binary homogeneous nucleation (BHN), H2SO4–H2O–NH3 ternary homogeneous nucleation (THN), H2SO4–H2O–ion binary ion-mediated nucleation (BIMN), and H2SO4–H2O–NH3–ion ternary ion-mediated nucleation (TIMN), based on a global chemistry transport model (GEOS-Chem) coupled with an advanced particle microphysics (APM) model, are conducted to study the particle number concentrations and new particle formation process. Our comparisons between measurements and simulations indicate that the BHN scheme and BIMN scheme significantly underestimate the observed particle number concentrations, and the THN scheme captures the total particle number concentration on most NPF event days well but fails to capture the noticeable increase in particle number concentrations on 18 March and 1 April. The TIMN scheme has obvious improvement in terms of total and sub-3 nm particle number concentrations and nucleation rates. This study provides a basis for further understanding of the nucleation mechanism in Beijing.

A High Kinetic Energy Ion Mobility Spectrometer for Operation at Higher Pressures of up to 60 mbar

High Kinetic Energy Ion Mobility Spectrometers (HiKE-IMS) are usually operated at absolute pressures around 20 mbar in order to reach high reduced electric field strengths of up to 120 Td for influencing reaction kinetics in the reaction region. Such operating points significantly increase the linear range and limit chemical cross sensitivities. Furthermore, HiKE-IMS enables ionization of compounds normally not detectable in ambient pressure IMS, such as benzene, due to additional reaction pathways and fewer clustering reactions. However, operation at higher pressures promises increased sensitivity and smaller instrument size. In this work, we therefore study the theoretical requirements to prevent dielectric breakdown while maintaining high reduced electric field strengths at higher pressures. Furthermore, we experimentally investigate influences of the pressure, discharge currents and applied voltages on the corona ionization source. Based on these results, we present a HiKE-IMS that operates at a pressure of 60 mbar and reduced electric field strengths of up to 105 Td. The corona experiments show shark fin shaped curves for the total charge at the detector with a distinct optimum operating point in the glow discharge region at a corona discharge current of 5 μA. Here, the available charge is maximized while the generation of less-reactive ion species like NOx+ is minimized. With these settings, the reactant ion population, H3O+ and O2+, for ionizing and detecting nonpolar substances like n-hexane is still available even at 60 mbar, achieving a limit of detection of just 5 ppbV for n-hexane.

Detecting Hexafluoroisopropanol Using Soft Chemical Ionization Mass Spectrometry and Analytical Applications to Exhaled Breath

Here we explore the potential use of proton transfer reaction/selective reagent ion-time-of-flight-mass spectrometry (PTR/SRI-ToF-MS) to monitor hexafluoroisopropanol (HFIP) in breath. Investigations of the reagent ions H3O+, NO+, and O2+• are reported using dry (relative humidity (rH) ≈ 0%) and humid (rH ≈ 100%)) nitrogen gas containing traces of HFIP, i.e., divorced from the complex chemical environment of exhaled breath. HFIP shows no observable reaction with H3O+ and NO+, but it does react efficiently with O2+• via dissociative charge transfer resulting in CHF2+, CF3+, C2HF2O+, and C2H2F3O+. A minor competing hydride abstraction channel results in C3HF6O+ + HO2• and, following an elimination of HF, C3F5O+. There are two issues associated with the use of the three dominant product ions of HFIP, CHF2+, CF3+, and C2H2F3O+, to monitor it in breath. One is that CHF2+ and CF3+ also result from the reaction of O2+• with the more abundant sevoflurane. The second is the facile reaction of these product ions with water, which reduces analytical sensitivity to detect HFIP in humid breath. To overcome the first issue, C2H2F3O+ is the ion marker for HFIP. The second issue is surmounted by using a Nafion tube to reduce the breath sample's humidity prior to its introduction into drift tube. The success of this approach is illustrated by comparing the product ion signals either in dry or humid nitrogen gas flows and with or without the use of the Nafion tube, and practically from the analysis of a postoperative exhaled breath sample from a patient volunteer.