Cluster Ions Research Articles

Novel polyaryl isatin polyelectrolytes with flexible monomers for anion exchange membrane fuel cells

The stability of the anion exchange polyelectrolytes is closely tied to the durability of anion exchange membrane fuel cells. Given their excellent alkali resistance, ether-free polymer backbones have attracted considerable attention for use in anion-exchange polyelectrolytes. Herein, a series of side-chain-type poly(terphenylene-co-dibenzyl N-(6-bromohexyl)-isatin) copolymers (QAPTDBHI-n) were synthesized via superacid-catalyzed polymerization and a subsequent quaternization reaction. The cyclic cardo groups in the backbones enabled the formation of nanovoids, which facilitated ionic clusters’ self-aggregation. The introduction of flexible bibenzyl monomers provided the polymers with a spatially foldable structure, promoting the aggregation of ion clusters and strengthening interchain interactions. Compared with the membrane without flexible monomers, QAPTDBHI-n membranes exhibited higher hydroxide conductivity (>115 mS cm−1 at 80 °C), outstanding mechanical stability (tensile strength: 50.91–60.76 MPa, elongation at break: 14.27%–26.06%), and superior alkali resistance (1 M NaOH at 80°C for >1500 h and <9.5% OH− conductivity loss). Regarding fuel cell performance, the AEMFC based on QAPTDBHI-40 ionomer achieved a peak power density of 1.14 W cm−2 (H2–O2) and 0.86 W cm−2 (H2-Air, CO2 free) at 80 °C due to its higher water uptake, OH− conductivity, and lower phenyl concentration.

Charge transport in highly acidic glass-forming protic ionic liquids tailored by zwitterionic precursors.

Highly acidic protic ionic liquids (PILs) are promising materials for potential electrochemical applications due to their high proton conductivity and excellent thermal stability. Still, little is known about the correlation between charge transport and structural dynamics as well as the proton transport mechanism despite the large body of literature on this topic. Here, we have examined the charge transport and structural dynamics by employing broadband dielectric spectroscopy in two highly acidic PILs in their supercooled liquid and glassy states, which included the same anion [TfO]- and different cations, [Tau]+ vs [Ahs]+. Unlike many other ionic liquids, the conductivity relaxation time τe of two studied PILs is substantially faster than the structural relaxation time τα. The decoupling behavior between charge transport and structural dynamics of two materials, which is manifested by a decoupling index Rτ, varies between 0.3 and 2.3 over the temperature range above Tg. Moreover, "Walden" plots of the molar conductivity vs the viscosity qualify both compounds as "Super ILs." All findings support the physical picture of large, polar, and orientationally correlated ion clusters, where the slow α-relaxation can be identified as structural relaxation associated with cooperative reorientations of the cluster macrodipole. In contrast, the shortest timescale for diffusive charge transport, τe, is 1-2 decades shorter than τα, implying that proton hopping is triggered by "single particle" (ions or ion pair) rotations and jumps on a sub-length scale of the cluster size, a dynamics being present even in the glassy state as indicated by a strong β-relaxation. These results demonstrate the practicality of employing highly acidic PILs in electrochemical fields.

A novel proton exchange membrane with long-range ordered proton transport pathways through modulation of interfacial interactions via amino-functionalized polyhedral oligomeric silsesquioxane-grafted graphene oxide

Nano octa-aminopropyl polyhedral oligomeric silsesquioxane (OA-POSS) was grafted into graphene oxide (GO) via covalent bonding to synthesize OA-POSS-g-GO. A novel SP/OA-POSS-g-GO proton exchange membrane was prepared by adding sulfonated poly (ether ether ketone) (SPEEK, SP). OA-POSS was well dispersed on GO to form an ordered acid-base pair with SPEEK, which facilitated the construction of continuous ion channels. GO as a carrier facilitated the construction of long-range proton conduction pathways in the membrane. The strong interactions between OA-POSS and SPEEK along with the synergistic effect of GO modulate the size of ionic clusters and increased the bound water ratio within the membrane. The conductivity of the SP/OA-POSS-g-GO-2 membrane (80 °C, 95% RH) reached 0.2096 S⋅cm−1, which was 1.7 times higher than that of the SPEEK membrane (0.1265 S⋅cm−1). The conductivity of the SP/OA-POSS-g-GO-2 membrane increased at 100 °C and 40% RH, while that of the SPEEK membrane decreased with the temperature increased above 80 °C. The maximum power density of the single cell assembled from the composite membrane reached 305.8 mW⋅cm−2 at 80 °C and 95% RH, which was 1.4 and 1.3 times higher than that of the SPEEK and Nafion 117 membrane, respectively.

Highly conductive anion-exchange membrane based on poly(acenaphthylenyl aryl piperidinium) π-π self-assembly

The use of strong intermolecular interaction force to promote the formation of ion transport channels is one of the common methods to increase the conductivity of AEMs. In this work, a series of poly(acenaphthylenyl aryl piperidinium) membranes and ionomer were prepared by ultra-strong acid-catalyzed polymerization. The π-π self-assembly of acenaphthylene monomer promoted the aggregation of piperidinium cation and the formation of efficient ion transport channel, which was confirmed by well aggregated transmission electron micrographs of the ion clusters. Therefore, the prepared membrane had desirable conductivity (173.38 mS cm−1 at 80 °C). Meanwhile, the membrane exhibited excellent alkaline stability (99 % retention of conductivity in 3 M NaOH solution immersed at 80 °C for 1000 h), acceptable dimensional stability (swelling rate < 27.78 % at 80 °C), and high mechanical properties (tensile strength >33.9 MPa). The H2/O2 fuel cell assembled based on the prepared QPANTP-20 membrane and ionomer exhibited peak power density of 266 mW cm−2 at 80 °C.

Flat-gain L-band amplifier containing AlPO4 units in aluminophosphosilicate erbium-doped fibers.

We present a flat-gain single-stage L-band erbium-doped fiber amplifier (EDFA) with a gain ripple of ±0.7 dB from 1580 to 1615 nm, by using aluminophosphosilicate erbium-doped fiber (APS-EDF) with an estimated AlPO4 composition of 13.3 mol%. A series of APS-EDFs were fabricated with increasing AlPO4 and Er concentrations, while maintaining a low background loss of 0.031 ± 0.005 dB/m and preventing Er ion clustering. The spectroscopic study shows a slightly narrowing Er cross section and flattened emission cross-section spectrum in the L-band with more AlPO4, thus favoring the L-band amplification with an improved gain flatness. Also, the gain coefficient, gain saturation, and temperature-dependent gain characteristics were reported. A better temperature tolerance was observed with increasing AlPO4.

Evidence for nanosized magnetic clusters of Ce-ions in the archetypal heavy fermion metal CeB6

Fine details of crystal structure of archetypal CeB6 hexaboride with heavy fermions are studied at temperatures 85 and 500 K by precise X-ray diffraction technique. Small static Jahn-Teller distortions of a simple cubic lattice are observed at these temperatures, leading to emergence of (i) dynamic charge stripes along selected directions <110>, <100>, and <111> in the crystals in combination with (ii) vibrationally coupled pairs of Ce ions. Instead of a Currie-Weiss type behavior, the temperature dependence of magnetization M∼(T − TCrand)−0.8 with TCrand∼TQ∼3.3 K was deduced in a wide temperature range 5–800 K for various directions of external magnetic field, which indicates the Griffiths phase formation with nanosized clusters of magnetic ions in CeB6. Moreover, in contrast to the scenario of a single-ion Kondo lattice, when revealing the power-law behavior of the magnetic contribution ρm(T)∼T−0.4 to the resistivity in the range of 8–90 K, we conclude in favor of the regime of weak localization of charge carriers in CeB6. Fourier maps of electron density confirm the conclusion about the nanosized magnetic clusters of Ce ions in this archetypal strongly correlated electron system with unusual magnetic ground state.

Insights into the structure and Ion transport of pectin-[BMIM][PF6] electrolytes.

We investigate the effect of pectin on the structure and ion transport properties of the room-temperature ionic liquid electrolyte 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) using molecular dynamics simulations. We find that pectin induces intriguing structural changes in the electrolyte that disrupt large ionic aggregates and promote the formation of smaller ionic clusters, which is a promising finding for ionic conductivity. Due to pectin in [BMIM][PF6] electrolytes, the diffusion coefficient of cations and anions is observed to decrease by a factor of four for a loading of 25 wt. % of pectin in [BMIM][PF6] electrolyte. A strong correlation between the ionic diffusivities (D) and ion-pair relaxation timescales (τc) is observed such that D ∼ τc-0.75 for cations and D ∼ τc-0.82 for anions. The relaxation timescale exponents indicate that the ion transport mechanisms in pectin-[BMIM][PF6] electrolytes are slightly distinct from those found in neat [BMIM][PF6] electrolytes (D∼τc-1). Since pectin marginally affects ionic diffusivities at the gain of smaller ionic aggregates and viscosity, our results suggest that pectin-ionic liquid electrolytes offer improved properties for battery applications, including ionic conductivity, mechanical stability, and biodegradability.

Unraveling the Molecular Dynamics of Glucose Oxidase Desorption Induced by Argon Cluster Collision.

The bombardment of a protein multilayer target by an energetic argon cluster ion beam enables protein transfer onto a collector in the vacuum while preserving their bioactivity (iBEAM method). In parallel to this new soft-landing variant, protein transfer in the gas phase is a prerequisite for their characterization by mass spectrometry. The successful transfer of bioactive lysozymes (14 kDa) by cluster-induced soft landing and its mechanistic explanation by molecular dynamics (MD) simulations have sparked an important inquiry: Can heavier biomolecules be desorbed while maintaining their tridimensional structure and hence their bioactivity? To address this question, we employed MD simulations using a reactive force field (ReaxFF). Specifically, the Ar cluster-induced desorption of glucose oxidase from either a gold substrate or a lysozyme underlayer was modeled using the LAMMPS code. First, the force field parameters were trained by computing the dissociation energetics of a series of organic molecules with ReaxFF and DFT, in order to realistically describe N-S and O-S interactions in the bombarded glucose oxidase molecule. Second, bombardment simulations investigated the effects of cluster size (ranging from 1000 to 10000 Ar atoms) and kinetic energy (1.5 and 3.0 eV/atom) on the structural features and energetics of the desorbing glucose oxidase. Our results show that large argon clusters (≥7000) are needed to desorb glucose oxidase from a gold surface, yet protein fragmentation and/or pronounced denaturation occur. However, the transfer of structurally preserved glucose oxidase in the gas phase is predicted by the simulations when an organic layer is used as a substrate.

Molecular dynamics simulation on thermophysical properties and local structure of ternary chloride salt for thermal energy storage and transfer system

Ternary chloride salt (NaCl–KCl–MgCl2) is considered as a potential high temperature thermal storage material owing to its low melting point, excellent thermal properties and low cost. However, the thermophysical properties of ternary chloride salts are difficult to measure under high-temperature conditions. In this study, the microscopic model of ternary chloride salt is constructed by Materials Studio software. The ratio of Na ions, K ions, Mg ions and Cl ions in the simulation system is determined according to the molar ratio of NaCl–KCl–MgCl2 eutectic ternary chloride salt. The total number of ions is identified based on computational resources and the accuracy of simulation results, and the number of the four ions in the system is finally determined. LAMMPS software is used to simulate the microstructure and calculate the thermal properties. Simulation results indicate that as the temperature increases, the distance between cluster ions increases, while the coordination number decreases, resulting in the ion association weakens. Simulation results of thermophysical properties are in good agreement with the experimental measurements. The decrease in density and viscosity is attributed to the weakening of ion association with increasing temperature. All the results are expected to provide reliable guidance for the design and preparation of next-generation concentrating solar thermal energy storage materials.

Focused ion beams from GaBiLi liquid metal alloy ion sources for nanofabrication and ion imaging

In this work, we present an overview of nanopatterning and imaging applications using newly developed workflows with focused ion beams (FIBs) produced with a GaBiLi liquid metal alloy ion source. The primary beam of this source type contains gallium, bismuth, and lithium as well as cluster ions which can be separated quickly using a Wien filter. Lithium ion milling has been applied to generate heptamer-arranged nanohole arrays in gold films with high resolution. Workflows for two-step bowtie nanofabrication using lithium and bismuth ions from the same source have been established. Furthermore, we present ion beam imaging results that were obtained with lithium ions on various sample materials. Combining the large sputter yield and high depth resolution of heavy bismuth ions with the high lateral imaging resolution of light lithium ions enables 3D nanoscale tomography using different ion species generated from the same source. Sample tilt is not required due to the top-down geometry of the FIB.

Highly efficient ultrasound-driven Cu-MOF/ZnWO4 heterostructure: An efficient visible-light photocatalyst with robust stability for complete degradation of tetracycline

Metal-organic frameworks (MOFs) are a significant class of porous, crystalline materials composed of metal ions (clusters) and organic ligands. The potential use of copper MOF (Cu-BTC) for the sonophotocatalytic degradation of Tetracycline (TC) antibiotic was investigated in this study. To enhance its catalytic efficiency, S-scheme heterojunction was created by combining Cu-BTC with Zinc tungstate (ZnWO4), employing an ultrasound-assisted hydrothermal method. The results demonstrated that the Cu-BTC/ZnWO4 heterojunction exhibited complete removal of TC within 60 min under simultaneous irradiation of visible light and ultrasound. Interestingly, the sonophotocatalytic degradation of TC using the Cu-BTC/ZnWO4 heterojunction showed superior efficiency (with a synergy index of ∼0.70) compared to individual sonocatalytic and photocatalytic degradation processes using the same heterojunction. This enhancement in sonophotocatalytic activity can be attributed to the formation of an S-scheme heterojunction between Cu-BTC and ZnWO4. Within this heterojunction, electrons migrated from Cu-BTC to ZnWO4, facilitated by the interface between the two materials. Under visible light irradiation, the built-in electric field, band edge bending, and coulomb interaction synergistically inhibited the recombination of electron-hole pairs. Consequently, the accumulated electrons in Cu-BTC and holes in ZnWO4 actively participated in the redox reactions, generating free radicals that effectively attacked the TC molecules. This study offers valuable perspectives on the application of a newly developed S-scheme heterojunction photocatalyst, demonstrating its effectiveness in efficiently eliminating diverse recalcitrant pollutants via sonophotocatalytic degradation.

Characterisation of gaseous iodine species detection using the multi-scheme chemical ionisation inlet 2 with bromide and nitrate chemical ionisation methods

Abstract. The multi-scheme chemical ionisation inlet 1 (MION1) enables rapid switching between the measurement of atmospheric ions without chemical ionisation and neutral molecules using various atmospheric pressure chemical ionisation methods. In this study, we introduce the upgraded version, the multi-scheme chemical ionisation inlet 2 (MION2). The new design incorporates enhanced ion optics, resulting in increased reagent ion concentration, ensuring a robust operation, and enabling the use of multiple chemical ionisation methods with the same ionisation time. In order to simplify the regular calibration of MION2, we developed an open-source flow reactor chemistry model called MARFORCE. This model enables quantification of the chemical production of sulfuric acid (H2SO4), hypoiodous acid (HOI), and hydroperoxyl radical (HO2). MARFORCE simulates the convection–diffusion–reaction processes occurring within typical cylindrical flow reactors with uniform inner diameters. The model also includes options to simulate chemical processes in the following two scenarios: (1) when two flow reactors with different inner diameters are connected and (2) when two flows are merged into one using a Y-shaped tee, although with reduced accuracy. Furthermore, the chemical mechanism files in the model are compatible with the widely used Master Chemical Mechanism (MCM), allowing for future adaptation to simulate other chemical processes in flow reactors. Furthermore, we conducted a comprehensive characterisation of the bromide (Br−) and nitrate (NO3-) chemical ionisation methods with different ionisation times. We performed calibration experiments for H2SO4, HOI, and HO2 by combining gas kinetic experiments with the MARFORCE model. The evaluation of sulfur dioxide (SO2), water (H2O), and molecular iodine (I2) involved dilution experiments from a gas cylinder (SO2), dew point mirror measurements (H2O), and a derivatisation approach combined with a high-performance liquid chromatography quantification (I2), respectively. Our findings indicate that the detection limit is inversely correlated with the fragmentation enthalpy of the analyte–reagent ion (Br−) cluster. In other words, stronger binding (resulting in a larger fragmentation enthalpy) leads to a lower detection limit. Additionally, a moderately longer ionisation time enhances the detection sensitivity, thereby reducing the detection limit. For instance, when using the Br− chemical ionisation method with a 300 ms ionisation time, the estimated detection limit for H2SO4 is 2.9×104 molec. cm−3. Notably, this detection limit is even superior to that achieved by the widely used Eisele-type chemical ionisation inlet (7.6×104 molec. cm−3), as revealed by direct comparisons. While the NO3- chemical ionisation method remains stable in the presence of high humidity, we have observed that the Br− chemical ionisation method (Br−–MION2) is significantly affected by the air water content. Higher levels of air water lead to reduced sensitivity for HO2 and SO2 under the examined conditions. However, we have found that a sharp decline in sensitivity for H2SO4, HOI, and I2 occurs only when the dew point exceeds 0.5–10.5 ∘C (equivalent to 20 %–40 % RH; calculated at 25 ∘C throughout this paper). For future studies utilising the atmospheric pressure Br− chemical ionisation method, including Br−–MION2, it is crucial to carefully consider the molecular-level effects of humidity. By combining approaches such as the water-insensitive NO3-–MION2 with Br−–MION2, MION2 can offer more comprehensive insights into atmospheric composition than what can be achieved by either method alone. By employing instrument voltage scanning, chemical kinetic experiments, and quantum chemical calculations, we have conclusively established that the presence of iodine oxides does not interfere with the detection of HIO3. Our comprehensive analysis reveals that the ions IO3-, HIO3⚫NO3-, and HIO3⚫Br−, which are detected using the Br− and NO3- chemical ionisation methods, are primarily, if not exclusively, generated from gaseous HIO3 molecules within atmospherically relevant conditions.

Assessment and prediction of hexavalent chromium vulnerability in groundwater by Geochemical modelling, NOBLES Index and Random Forest Model

Unregulated chromite mining causes enrichment of hexavalent chromium in the groundwater. Due to unpredictable monsoonal recharge and anthropogenic dependencies on groundwater, the depth and extent of chromium pollution becomes extremely difficult to demarcate. For this specific objective, the present study was carried out in order to explore the potential of a coupled surface and sub-surface modelling approach in Sukinda valley, which accounts for 97–98 % of the total chromite reserve of India. Through ionic speciation, saturation state and clustering analysis, the most probable source and corresponding mineral stability state was investigated. In order to trace the extent, status and severity of the problem, both hydrogeologic parameters as well as the geogenic soil parameters were taken into account to develop DRASTIC, DRASTIC-L as well as NOBLES Index. While DRASTIC and DRASTIC-L model provided assessment of vulnerability due to surface leaching of contaminants, NOBLES index, speciation analysis and geochemical model provided sub-surface assessment of vulnerability due to chromium. MRSA and SPSA sensitivity analysis were applied in order to understand the most critical factor that can dominantly control the surface contamination in the groundwater. Random Forest (RF) based machine learning techniques were applied in order to integrate the sub-surface as well as surface characteristics for the purpose of prediction of chromium in the groundwater. The present study therefore presents a novel methodology of risk assessment for regions where either extensive mining activities are operational or in regions with abandoned mines with operative acid mine drainage.

Charge‐Selectively Permeable Self‐Healing Microcapsules

AbstractMicrocapsules possessing a selective permeability are well‐suited vessels for conducting cell studies or chemical reactions that require selective exchanges of reagents over a prolonged time. Most currently reported microcapsules are single‐use delivery carriers since cargo is only released in significant amounts if their shells are damaged or the release relies on passive diffusion. Stable capsules possessing a selective, rapidly interchangeable permeability, which enables their repeated loading and unloading with selected reagents remain to be shown. Here, capsules are introduced that are composed of thin, viscoelastic, charge‐selective shells made of surfactants that are functionalized with a chelator, 3‐hydroxy‐4‐pyridinonone and crosslinked with appropriate nm‐sized ion clusters, for example composed of Fe3+/Tris or Al3+/Tris ion clusters. The charge selectivity of the shell permeability can be conveniently tuned with the crosslinking ion clusters. It is demonstrated that these capsules can be repeatedly loaded and unloaded with well‐defined substances. This feature enables their application as re‐usable selectively permeable filters to remove certain pollutants from solutions. These capsules are envisaged to be well‐suited for waste water treatment and as picoliter‐sized reaction vessels to selectively conduct chemical reactions within capsule cores while continuously supplying new reagents.

SPEEK-co-PEK-x proton exchange membranes with controllable sulfonation degree for proton exchange membrane fuel cells

Sulfonated poly(ether ether ketone)-poly(ether ketone) (SPEEK-co-PEK-x) copolymers with controlled degree of sulfonation are synthesized by the polycondensation reaction of varying monomer ratios. Compared with the traditional homopolymer sulfonated poly(ether ether ketone) (H-SPEEK), the SPEEK-co-PEK-x copolymer membrane has a high degree of sulfonation and excellent proton conductivity. Meanwhile, it also has favorable mechanical properties and stability. This is attributed to the introduction of the -PEK- segment. The SPEEK-co-PEK-75 membrane exhibits the highest conductivity (0.285 S cm−1) at 80 °C, 100% RH and when tests at 80 °C with 80% RH, the SPEEK-co-PEK-75 membrane reaches 0.0587 S cm−1. In addition, the tensile strength of the SPEEK-co-PEK-75 membrane reaches 47.66 MPa at room temperature. Moreover, the study investigates the impact of key variables on the single-cell performance of SPEEK-co-PEK-x membranes. The measured peak power densities of the SPEEK-co-PEK-75 membrane are 212 mW cm−2 and 495 mW cm−2 at 70% RH and 100% RH, which are 1.3 times and 1.7 times higher than that of the Nafion 117 membrane, respectively. After the 80 h durability test at 80 °C and 80% RH, the voltage of the SPEEK-co-PEK-75 membrane only drops by 4.8%. The presence of the -PEK- segment results in a more compact and connected distribution of hydrophilic ion clusters in the SPEEK-co-PEK-X membrane. This adjustment greatly enhances the performance of the membrane, making it an excellent candidate for proton exchange membrane in H2/air fuel cells.

Carboxymethyl cellulose capped zinc oxide nanoparticles dispersed in ionic liquid and its antimicrobial effects against foodborne pathogens

Zinc oxide nanoparticles (ZnO NPs) have been proven with antimicrobial function, but the high tendency to aggregate hinders their practical applications. To improve the dispersibility of ZnO NPs as antimicrobial agent, choline acetate (ChAc), a class of ionic liquids, was employed to facilitate the dispersion of ZnO NPs capped with carboxymethyl cellulose (CMC). In this study, ZnO-CMC NPs at various concentrations were added in DI water with or without ChAc followed by sonication. Uniform and small particles were observed in ChAc-dispersed ZnO-CMC (ChAc/ZnO-CMC) by atomic force microscopy and transmission electron microscopy, due to the formation of a double layer on their surface via the positive and negative charged ionic clusters from ChAc, thereby enhancing repulsion and inhibiting aggregation. The antimicrobial capacity was tested against two strains - Listeria monocytogenes (L. monocytogenes) and Escherichia coli K-12 (E. coli K-12), based on minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and bacteria growth kinetics. The ChAc/ZnO-CMC exhibited the strongest antimicrobial activities as compared with commercial ZnO and as-prepared ZnO-CMC without ChAc. The antimicrobial capacity was related to occurrence of cytolysis, disruption of cell walls and ROS production. Overall, ChAc/ZnO-CMC NPs hold great potential as an antimicrobial agent and may be incorporated into different food packaging films and coatings.

Anti-Stokes cooling in highly ytterbium doped phase separated aluminium-yttrium oxide glass by 4 K

Silica glass is a strong candidate in the development of radiation balanced fiber lasers and amplifiers due to its properties such as high stability, high mechanical robustness and chemical durability, thermal resistance, high purity and so on. However, low rare-earth ion solubility lead to inter-ionic energy transfers processes which cause multi-phonon relaxation through a non-radiative decay process and hinder it from being used for aforementioned applications as well as for optical cooling. In the present work, we report cooling to a record low temperature of −4 K from room temperature at atmospheric pressure in a novel silica based highly Yb doped phase separated oxide glass (named as PS: GAYY glass - aluminium: yttrium: ytterbium) using 20 W of 1037 nm pump wavelength. We further theoretically show a global minimum achievable temperature of ∼165 K in our glass. Here, the basic limitation for laser induced cooling in silica glass associated with the existence of clustering of rare earth ions is significantly mitigated. This was achieved by the addition of suitable co-dopants such as aluminum and yttrium which modified the local rare-earth ion environment to avoid clustering as well as reducing the phonon energy. The fabricated glass using modified chemical vapor deposition process in combination with a solution doping technique achieved a maximum doping concentration of 5.57 × 1026 ions/m3 and exhibits better performance than other silica-based host glasses in terms of both optical properties and laser cooling characteristics. We believe PS-GAYY glasses may open new avenues in the field of solid-state laser cooling, promising exciting and broad applications in radiation balanced lasers and amplifiers.

The endowment of monovalent anion selectivity and antifouling property to cross-linked ion-exchange membranes by constructing amphoteric structure

Ion exchange membranes (IEMs) with high monovalent-ion selectivity show promising application in ion resource recovery. In this work, we report a kind of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)-based on amphoteric ion exchange membranes (AIEMs) having cross-linked structure. Therein, four imidazolium-terminated aliphatic chains (2IM-nC, n = 3, 6, 9, and 12) with varied number of −CH2− were used as crosslinker for cross-linking membrane matrix. Small-angle X-ray scattering tests indicate that the ion cluster sizes of the four AIEMs are evaluated with values of 0.378, 0.384, 0.388 to 0.408 nm, which possibly render the enhanced mono-valent anion selectivity of as-prepared AIEMs. Tested in the electrodialysis (ED) filled with a mixture solution of 0.05 M NaCl + 0.05 M Na2SO4, at current densities of 2.5 mA·cm−2 and 5.0 mA·cm−2, the PSO42-Cl- values of cross-linked AIEM having longer alkyl chains are 20.41 and 22.51, respectively, which are higher than AIEM with shorter cross-linker alkyl chain under the same conditions (3.5). Due to the hydrophilic surface and hydrophilic/negatively charged zwitterionic surface of AIEM, act as useful barriers via physical blocking and electrostatic repulsion, respectively, the anti-fouling performance of IEMs is improved simultaneously. In view of the superior performance, it is believed that the structure–property relationship of AIEM developed here can serve as a guideline for advanced IEMs.

Matrix-Enhanced SIMS: The Influence of Primary Ion Species and Cluster Size on Ion Yield and Ion Yield Enhancement of Lipids.

Time-of-flight secondary ion mass spectrometry is one of the most promising techniques for label-free analysis of biomolecules with nanoscale spatial resolution. However, high-resolution imaging of larger biomolecules such as phospholipids and peptides is often hampered by low yields of molecular ions. Matrix-enhanced SIMS (ME-SIMS), in which an organic matrix is added to the sample, is one promising approach to enhancing the ion yield for biomolecules. Optimizing this approach has, however, been challenging because the processes involved in increasing the ion yield in ME-SIMS are not yet fully understood. In this work, the matrix α-cyano-4-hydroxycinnamic acid (HCCA) has been combined with cluster primary ion analysis to better understand the roles of proton donation and reduced fragmentation on lipid molecule ion yield. A model system consisting of 1:100 mol ratio dipalmitoylphosphatidylcholine (DPPC) in HCCA as well as an HCCA-coated mouse brain cryosection have been studied using a range of Bi and Ar cluster ions. Although the molecular ion yield increased with an increase in cluster ion size, the enhancement of the signals from intact lipid molecules decreased with an increase in cluster ion size for both the model system and the mouse brain. Additionally, in both systems, protonated molecular ions were significantly more enhanced than sodium and potassium cationized molecules for all of the primary ions utilized. For the model system, the DPPC molecular ion yield was increased by more than an order of magnitude for all of the primary ions studied, and fragmentation of DPPC was dramatically reduced. However, on the brain sample, even though the HCCA matrix reduced DPPC fragmentation for all of the primary ions studied, the matrix coating suppressed the ion yield for some lipids when the larger cluster primary ions were employed. This indicated insufficient migration of the lipids into the matrix coating, so that dilution by the matrix overpowered the enhancement effect. This study provides strong evidence that the HCCA matrix both enhances protonation and reduces fragmentation. For imaging applications, the ability of the analytes to migrate to the surface of the matrix coating is also a critical factor for useful signal enhancement. This work demonstrates that the HCCA matrix provides a softer desorption environment when using Bi cluster ions than that obtained using the large gas cluster ions studied alone, indicating the potential for improved high spatial resolution imaging with ME-SIMS.

Improvement of Lipid Detection in Mouse Brain and Human Uterine Tissue Sections Using In Situ Matrix Enhanced Secondary Ion Mass Spectrometry.

The potential of mass spectrometry imaging, and especially ToF-SIMS 2D and 3D imaging, for submicrometer-scale, label-free molecular localization in biological tissues is undisputable. Nevertheless, sensitivity issues remain, especially when one wants to achieve the best lateral and vertical (nanometer-scale) resolution. In this study, the interest of in situ matrix transfer for tissue analysis with cluster ion beams (Bin+, Arn+) is explored in detail, using a series of six low molecular weight acidic (MALDI) matrices. After estimating the sensitivity enhancements for phosphatidylcholine (PC), an abundant lipid type present in almost any kind of cell membrane, the most promising matrices were softly transferred in situ on mouse brain and human uterine tissue samples using a 10 keV Ar3000+ cluster beam. Signal enhancements up to 1 order of magnitude for intact lipid signals were observed in both tissues under Bi5+ and Ar3000+ bombardment. The main findings of this study lie in the in-depth characterization of uterine tissue samples, the demonstration that the transferred matrices also improve signal efficiency in the negative ion polarity and that they perform as well when using Bin+ and Arn+ primary ions for analysis and imaging.