Cluster Ions Research Articles

High ion exchange capacity perfluorosulfonic acid resine proton exchange membrane for high temperature applications in polymer electrolyte fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) have attract much attention from academic and industry, which can improve the catalyst activity, reduce Pt loading, enhance CO tolerance, and simplify water and heat management. High-temperature proton exchange membrane (HT-PEM) is the key component for HT-PEMFCs. Here, we provide an investigation of newly developed HT-PEM to evaluate its properties and performances in fuel cells above 90 °C. The HT-PEM exhibits an excellent proton conductivity of 136.1 mS cm−1 at 90 °C and 95% RH, and remarkable power density of 0.95 Wcm−2 at 105 °C and 80% RH. The stability and durability of HT-PEM are studied with varied testing methods. After the continuous operation at open circuit voltage (OCV) for 500 h and continuous dry-wet circulation for 20000 cycles at 90 °C, negligible change of OCV and hydrogen permeation current density are recorded, indicating good chemical and mechanical stability for HT-PEM. The improved property and performance originate from the new PFSA base material and improved morphology, in which the larger ionic clusters and continuous proton-transfer channels contribute to the superior performance, and the high glass transition temperature (Tg∼132 °C) induces good stability.

Experimental measurement and thermodynamic modeling of hydrate stability conditions in the methane + cyclopentane + tetra-n‑butyl ammonium chloride (TBAC) aqueous solution system

The present study investigates hydrate dissociation conditions in methane + cyclopentane (CP) and tetra-n‑butyl ammonium chloride (TBAC) aqueous solution. The experimental work was done using an isochoric vessel with varying compositions of the promoters in the pressure and temperature ranges of (1.42 to 4.90) MPa and (291.2 to 298.9) K, respectively. The methane hydrate dissociation pressure was predicted by the Gibbs minimization method. The findings denote that adding CP to the TBAC-containing system shifts the hydrate dissociation temperature of methane to higher values. The results also show an average increase of 12, 9, 5, and 3 K in hydrate dissociation temperature for 5, 10, 20, and 30 wt% TBAC in aqueous solution within the pressures. These results can be caused by the existence of more dodecahedral cages that are inhabited by methane. Thus, it makes hydrates more stable and increases the temperature of hydrate dissociation. On the other hand, adding TBAC to CP containing system has an inhibitor effect. The methane hydrate dissociation temperature was not changed sensibly when a 5 wt% TBAC was added to CP containing system. When the addition of the TBAC weight percentage to CP containing system is increased to 10, the average hydrate dissociation temperature decreases by 1 K within the pressures. When adding 20 and 30 wt% TBAC to CP containing system an average decrease of 2 K and 3 K in the hydrate dissociation temperature is resulted, respectively, within the pressures. The reduction in the hydrate dissociation temperatures can be attributed to salting-out and ion clustering. The experimental data and modeling results for the hydrate dissociation pressures exhibit an AARD of 2.4 %.

Using sputtering parameters to mitigate argon ion sputtering induced reduction of nickel in XPS

Argon ion sputtering for depth profiling in XPS results in the preferential sputtering of oxygen in certain oxide systems. Preferential oxygen removal results in the chemical reduction of the associated cation which is observed in spectra collected following sputtering. Characterizing the effects of different sputtering parameters and developing methods to account for and to minimize changes to chemical states during sputtering would allow for greater confidence in the qualitative and quantitative analysis of the chemical states observed after sputtering. In this study argon ion sputtering was performed with monatomic and clustered argon ions on thermally oxidized NiO. Parameters for monatomic and cluster sputtering were varied to observe their effects on the induced reduction. Results show that extensive reduction is experienced for monatomic sputtering irrespective of the energy and current chosen. For cluster argon ion sputtering, reduction was mitigated when selecting either large cluster sizes or low cluster energies. Sputtering for long periods of time with low energy clusters was observed to result in the removal of surface contaminants without concomitant reduction of the nickel oxide.

Preparation of calcium phosphate ion clusters through atomization method for biomimetic mineralization of enamel.

Dental enamel is a mineralized extracellular matrix, and enamel defect is a common oral disease. However, the self-repair capacity of enamel is limited due to the absence of cellular components and organic matter. Efficacy of biomimetic enamel mineralization using calcium phosphate ion clusters (CPICs), is an effective method to compensate for the limited self-healing ability of fully developed enamel. Preparing and stabilizing CPICs presents a significant challenge, as the addition of certain stabilizers can diminish the mechanical properties or biosafety of mineralized enamel. To efficiently and safely repair enamel damage, this study quickly prepared CPICs without stabilizers using the atomization method. The formed CPICs were evenly distributed on the enamel surface, prompting directional growth and transformation of hydroxyapatite (HA) crystals. The study revealed that the mended enamel displayed comparable morphology, chemical composition, hardness, and mechanical properties to those of the original enamel. The approach of repairing dental enamel by utilizing ultrasonic nebulization of CPICs is highly efficient and safe, therefore indicating great promise.

Fragmentation of water clusters formed in helium nanodroplets by charge transfer and Penning ionization.

Helium nanodroplets ("HNDs") are widely used for forming tailor-made clusters and molecular complexes in a cold, transparent, and weakly interacting matrix. The characterization of embedded species by mass spectrometry is often complicated by the fragmentation and trapping of ions in the HNDs. Here, we systematically study fragment ion mass spectra of HND-aggregated water and oxygen clusters following their ionization by charge transfer ionization ("CTI") and Penning ionization ("PEI"). While the efficiency of PEI of embedded clusters is lower than for CTI by about factor 10, both the mean sizes of detected water clusters and the relative yields of unprotonated cluster ions are significantly larger, making PEI a "soft ionization" scheme. However, the tendency of ions to remain bound to HNDs leads to a reduced detection efficiency for large HNDs containing >104 helium atoms. These results are instrumental in determining optimal conditions for mass spectrometry and photoionization spectroscopy of molecular complexes and clusters aggregated in HNDs.

A MODEL FOR SURFACE NANORELIEF FORMATION UNDER GAS CLUSTER ION IRRADIATION

A model for the evolution of surface nanorelief under irradiation with gas cluster ions is proposed. The model is based on consideration of individual collisions of clusters with a surface. The amount of substance sputtered from the collision area and the e ciency of its redeposition onto other surface elements are determined. The performance of the model is shown when compared with experimental data. The stages of smoothing of a harmonic relief are studied. A new measure of the e ectiveness of surface smoothing is proposed.

Water molecule elimination from the protonated methanol dimer ion-An example of a size-selective intracluster reaction.

The abundance of extraterrestrial methanol makes the reaction between methanol molecules in a molecular cluster a possible key step in the search for mechanisms for the formation of more complex molecules under the conditions of the interstellar medium as well as circumstellar and planetary atmospheres. The reaction leading to the formation of the dimethyl ether ion from a methanol molecule interacting with a protonated methanol ion via the elimination of a water molecule is a basic mechanism for the formation of complex organic molecules. Here, we experimentally examine such reactions in the gas phase, analyzing the production and reactivity of protonated cluster ions formed by the ionization of a supersonic jet of methanol. Focusing especially on the post-collisional relaxation of the protonated methanol dimer and trimer ions after high-energy single collisions, the results indicate a strong size selectivity favoring the occurrence of this reaction only in the dimer ion. To elucidate this behavior, the velocity distribution of the eliminated water molecule was measured using an event-by-event coincidence analysis. These results are interpreted using quantum chemical calculations of the dissociation pathways. It turns out that in the dimer case, two transition states are able to contribute to this intracluster reaction. In the trimer case, methanol evaporation appears as the most energetically favorable relaxation pathway.

Synthesis of Polar-functionalized Isotactic Polypropylenes Using Commercial Heterogeneous Ziegler-Natta Catalyst.

The efficient synthesis of polar-functionalized polypropylenes with high molecular weight and high stereoregularity represents a challenging task. This challenge becomes even more daunting when pursuing an industrially preferred heterogeneous process. This study demonstrated the realization of these goals through the use of commercial heterogeneous Ziegler-Natta catalysts in the copolymerization of propylene with ionic cluster polar monomers. The results revealed high copolymerization activity (∼1.1 × 107 g mol-1 h-1), moderate polar monomer incorporation ratios (∼4.9 mol %), high copolymer molecular weight (Mw > 105 g mol-1), high stereoregularity ([mmmm] ∼ 96%), and high melting temperature range (150-162 °C). The utilization of ionic cluster polar monomers improved the thermal stability as well as stereoselectivity of the catalyst. Moreover, the Ziegler-Natta catalyst can homopolymerize ionic cluster polar monomers with high activities (>104 g mol-1 h-1). The resulting polar-functionalized isotactic polypropylenes (iPP) exhibited superior tensile strength, impact strength, creep resistance, transparency, and crystallinity compared with nonpolar iPP. This enhancement was attributable to the dual roles of the ionic cluster polar monomer unit, serving as both a transparent nucleating agent and a dynamic cross-linking functionality. Furthermore, the polar-functionalized iPP exhibited improved compatibility with polar materials, offering benefits for applications in composites, recycling of mixed plastic wastes, 3D printing, and other fields. This study offered a comprehensive solution for the future industrial production of polar-functionalized iPP via copolymerization, bridging the gap between an efficient and practical copolymerization process from a synthetic chemistry perspective and enhanced material properties from an application perspective.

Elucidating the mechanisms of atmospheric new particle formation in the highly polluted Po Valley, Italy

Abstract. New particle formation (NPF) is a major source of aerosol particles and cloud condensation nuclei in the troposphere, playing an important role in both air quality and climate. Frequent NPF events have been observed in heavily polluted urban environments, contributing to the aerosol number concentration by a significant amount. The Po Valley region in northern Italy has been characterized as a hotspot for high aerosol loadings and frequent NPF events in southern Europe. However, the mechanisms of NPF and growth in this region are not completely understood. In this study, we conducted a continuous 2-month measurement campaign with state-of-the-art instruments to elucidate the NPF and growth mechanisms in northern Italy. Our results demonstrate that frequent NPF events (66 % of all days during the measurement campaign) are primarily driven by abundant sulfuric acid (8.5×106 cm−3) and basic molecules in this area. In contrast, oxygenated organic molecules from the atmospheric oxidation of volatile organic compounds (VOCs) appear to play a minor role in the initial cluster formation but contribute significantly to the consecutive growth process. Regarding alkaline molecules, amines are insufficient to stabilize all sulfuric acid clusters in the Po Valley. Ion cluster measurements and kinetic models suggest that ammonia (10 ppb) must therefore also play a role in the nucleation process. Generally, the high formation rates of sub-2 nm particles (87 cm−3 s−1) and nucleation-mode growth rates (5.1 nm h−1) as well as the relatively low condensational sink (8.9×10-3 s−1) will result in a high survival probability for newly formed particles, making NPF crucial for the springtime aerosol number budget. Our results also indicate that reducing key pollutants, such as SO2, amine and NH3, could help to substantially decrease the particle number concentrations in the Po Valley region.

Synergistic incorporation of Ti3C2Tx with sulfonated poly(phenylene oxide) membranes: Unravelling multifaceted advancements in physicochemical, electrochemical, and antibacterial domains for enhanced electrodialytic desalination

This study delves into the solution-phase incorporation of Ti3C2Tx nanosheets into sulfonated poly(phenylene oxide) (SPPO) to prevail the conventional challenge of distant ionic channels in membranes. A series of membranes incorporating MXene (Ti3C2Tx nanosheets) at varying weight percentages (1 wt%, 2 wt%, and 5 wt%) underwent meticulous scrutiny of their physicochemical and electrochemical attributes. Among this series, MXe-02 emerged as particularly noteworthy, showing remarkable water sorption (WS= 43.8%), ion exchange capacity (IEC: 1.65 ± 0.05 meqg−1), and ionic conductivity (IC: 2.83×10−2 S cm−1), coupled with minimal dimensional change of 8.57% compared to its pristine counterpart, SPPO-B (WS=35.70%, IEC: 1.03±0.05 meqg−1, IC: 1.98×10–2 S cm−1). Advanced analytical techniques such as atomic force microscopy (AFM) and field emission-scanning electron microscopy (FE-SEM) provided insights into hydrophilic-hydrophobic phase separation, ionic domain clustering, and membrane surface attributes pivotal for enhancing electrochemical properties. Beyond optimal concentrations (>2 wt%), a significant composite-agglomeration effect hindered further advancements in physicochemical and electrochemical aspects, as verified by zeta potential measurements. The optimized MXe-02 membrane boasted a notable transport number of 0.89 with a substantial limiting current density (Ilim = 45 mA cm−2), offering a wide window for swift electrodialytic desalination. Moreover, MXe-02 membranes demonstrated an energy consumption of 0.98 kWh kg−1 and 93.52% energy efficiency, affirming their efficacy for brackish water desalination. Antibacterial properties were evaluated against Escherichia coli and Staphylococcus aureus, revealing MXe-02 and MXe-05's distinct zones of inhibition against S. aureus, highlighting their excellent antibacterial efficacy against Gram-positive bacteria. This comprehensive study shows the intricate interplay of MXene-incorporated membranes, offering valuable insights for advancing electrochemical and antibacterial performance in water desalination.

Differential characteristics of the particles sputtered by gas cluster ions at elevated temperatures. Molecular dynamics simulation

The effect of the target temperature on sputtering by gas cluster ions was investigated using molecular dynamics simulation. The temperature of <111> copper target was set in range from 300 K to 1100 K, and bombarding 10 keV argon clusters had the size from 50 to 500 atoms. Sputter yield was found to increase with the temperature. The increase depended on the cluster size, and its value was much higher than it had been considered previously for nonlinear sputtering. Differential characteristics of the process, such as angular, energy, and time distributions of the sputtered atoms, as well as their initial positions, were obtained to promote understanding of the mechanisms involved. The dynamics of the collision crater size and its shape were described. The concept of temperature inside the collision area was used to explain the results.

From Molecular Constraints to Macroscopic Dynamics in Associative Networks Formed by Ionizable Polymers: A Neutron Spin Echo and Molecular Dynamics Simulations Study.

The association of ionizable polymers strongly affects their motion in solutions, where the constraints arising from clustering of the ionizable groups alter the macroscopic dynamics. The interrelation between the motion on multiple length and time scales is fundamental to a broad range of complex fluids including physical networks, gels, and polymer-nanoparticle complexes where long-lived associations control their structure and dynamics. Using neutron spin echo and fully atomistic, multimillion atom molecular dynamics (MD) simulations carried out to times comparable to that of chain segmental motion, the current study resolves the dynamics of networks formed by suflonated polystryene solutions for sulfonation fractions 0 ≤ f ≤ 0.09 across time and length scales. The experimental dynamic structure factors were measured and compared with computational ones, calculated from MD simulations, and analyzed in terms of a sum of two exponential functions, providing two distinctive time scales. These time constants capture confined motion of the network and fast dynamics of the highly solvated segments. A unique relationship between the polymer dynamics and the size and distribution of the ionic clusters was established and correlated with the number of polymer chains that participate in each cluster. The correlation of dynamics in associative complex fluids across time and length scales, enabled by combining the understanding attained from reciprocal space through neutron spin echo and real space, through large scale MD studies, addresses a fundamental long-standing challenge that underline the behavior of soft materials and affect their potential uses.

Pushing nano-aerosol measurements towards a new decade – technical note on the Airmodus particle size magnifier 2.0

Abstract. Accurate measurement of the size distribution of sub-10 nm aerosol particles is still a challenge. Here we introduce a novel version of the Airmodus particle size magnifier (PSM 2.0), which is a condensation-particle-counter-based instrument with a sizing range of 1–12 nm. The extended size range compared to the earlier PSM version enables the direct detection of forming clusters and particles as well as the study of their growth processes without the challenges related to particle charging. It also gives an overlap between the activation size distribution measurements with the PSM and mobility size distribution measurements with conventional mobility particle sizers. We compared the performance of PSM 2.0 to that of a mobility particle size spectrometer, the original A10 particle size magnifier, and a Neutral cluster and Air Ion Spectrometer (NAIS) during field measurements. Also, calibration results were compared against the A10 instrument. The results show that PSM 2.0 is able to activate sub-2 nm clusters and that the concentration and size distribution between 2–12 nm compare well, especially with the NAIS.

Multimodal mass spectrometry imaging identifies cell-type-specific metabolic and lipidomic variation in the mammalian liver

Spatial single-cell omics provides a readout of biochemical processes. It is challenging to capture the transient lipidome/metabolome from cells in a native tissue environment. We employed water gas cluster ion beam secondary ion mass spectrometry imaging ([H2O]n>28K-GCIB-SIMS) at ≤3μm resolution using a cryogenic imaging workflow. This allowed multiple biomolecular imaging modes on the near-native-state liver at single-cell resolution. Our workflow utilizes desorption electrospray ionization (DESI) to build a reference map of metabolic heterogeneity and zonation across liver functional units at tissue level. Cryogenic dual-SIMS integrated metabolomics, lipidomics, and proteomics in the same liver lobules at single-cell level, characterizing the cellular landscape and metabolic states in different cell types. Lipids and metabolites classified liver metabolic zones, cell types and subtypes, highlighting the power of spatial multi-omics at high spatial resolution for understanding celluar and biomolecular organizations in the mammalian liver.

Isomerism of Cyclodextrin Tetramer Induced by Alkali Halide Cluster Ions Observed by Ion Mobility Spectrometry-Mass Spectrometry.

Cyclodextrins (CDs) exhibit versatile self-assembly properties due to their hydrophilic and hydrophobic components, with applications such as drug delivery and selective binding. While research on CD self-assembly is extensive, limited studies have explored their aggregation behavior, particularly in interactions with small ionic guests. The present work investigates the structure of β-CD tetramers aggregated with alkali metal chloride clusters using ion mobility spectrometry-mass spectrometry (IMS-MS). The results revealed that diverse structures emerge in the tetramer depending on the alkali metal cluster size. Notably, the doubly charged tetramer exhibits distinct aggregation trends with specific numbers of MCl clusters for Na+ and K+ ions. After initially adopting a bucket-wheel structure with two internal cations, the structure transforms into a new isomer with a tetrahedral configuration upon cluster addition. The formation of the new isomer structure is closely linked to filling the cavity volume with MCl clusters and ionic interactions, which possibly compensate for the weakened hydrogen bonds between CDs. Theoretical calculations further support the structures, showing well-matched collision cross-section (CCS) values compared with the experimental CCS values. This study highlights the role of alkali metal chloride clusters as potential templates, leading to the formation of novel CD assemblies.

Quantitative assessment of nano-plastic aerosol particles emitted during machining of carbon fiber reinforced plastic

Focusing on the relatively unexplored presence of micro- and nano-plastic aerosol particles, this study quantitatively assessed the emission of nano-plastic particles during the machining of carbon fiber reinforced plastic (CFRP) in the working environment. Measurements of aerosol particles smaller than 1 µm in size were performed by aerosol mass spectrometry. The findings revealed that concentrations of carbonous aerosol particles (organic aerosol and refractory black carbon (rBC)) were higher during working hours than during non-working hours. Positive matrix factorization identified CFRP particles as a significant source, contributing an average of approximately 30% of concentration of carbonous aerosol particles during working hours. This source apportionment was corroborated by the presence of bisphenol A and F fragments, principal components of the epoxy resins used in CFRP, and was corroborated by similarities to the carbon cluster ion distribution observed in rBC during CFRP pipe-cutting operations. Further, the particle size distribution suggested the existence of plastic aerosol particles smaller than 100 nm. This study established the method to quantitatively distinguish nano-plastic aerosol particles from other aerosol particles in high temporal resolution and these techniques are useful for accurately assessing exposure to nano-plastic aerosol particles in working environments.

Model of Surface Nanorelief Formation under Irradiation with Gas Cluster Ions

Model of Surface Nanorelief Formation under Irradiation with Gas Cluster Ions

A multi-reflection time-of-flight setup for the study of atomic clusters produced by magnetron sputtering

The Greifswald multi-reflection time-of-flight setup has been extended with a magnetron sputtering gas aggregation source for the production of atomic cluster ions with sizes ranging from a single to thousands of atoms. This source, combined with a newly added quadrupole mass filter and a linear Paul trap, opens up the possibility of many new atomic-cluster studies not feasible with the setup before. The new components and their interfacing with the previous setup are described, and benchmarking as well as the first experimental results are presented. The capability of the system to handle singly charged ions with masses of several ten thousand atomic mass units is demonstrated.

Preferential Sputtering of Alloys by Gas Cluster Ions

Preferential Sputtering of Alloys by Gas Cluster Ions

Correlation of the Charge Resonance Interaction with Cluster Conformations Probed by Electronic Spectroscopy of Dimer Radical Cations of CO2 and CS2 in a Cryogenic Ion Trap.

Radical cations of dimeric clusters of carbon dioxide/disulfide, [(CX2)2]+• (X = O and S), form strong intracluster bonds through charge resonance (CR) interactions. We herein performed electronic photodissociation spectroscopy of [(CX2)2]+• while regulating the temperature under ambient and cryogenic conditions using a quadrupole ion trap. Both ions exhibited broad band absorption in the near-infrared-visible light region; it is called the "CR band", as a measure of the strength of the CR interaction. Strikingly, this band underwent a noticeable blue shift upon cryogenic cooling for [(CS2)2]+• while not for [(CO2)2]+•. On the basis of quantum chemical calculations with a coupled cluster method, the band shift was attributed to the variations in the relative population of two energetically close conformers found for [(CS2)2]+•. This study highlights a strong correlation between CR interactions and conformation of the radical dimer cations, demonstrating the exceptional significance of cryogenic cooling in the chemistry of ionic molecular clusters.