Formation Of Cluster Ions Research Articles

Nanoparticle-Based LDI-MS Immunoassay for the Multiple Diagnosis of Viral Infections.

Many serious public health emergencies around the globe are caused by viral epidemics. Thus, developing a reliable method for viral screening is in high demand. Multiplex assays for simultaneous detection and fast screening of high-risk pathogens are especially needed. This study employs metal nanoparticles to generate specific mass spectral signals for different RNA viruses, which enables simultaneous detection of whole viruses by laser desorption/ionization mass spectrometry (LDI-MS). We developed a nanoparticle-based sandwich immunosorbent assay as a sensing platform for the detection of viruses and viral nonstructural protein by LDI-MS. Cellulose acetate membrane (CAM) serves as the substrate for the fabrication of the sandwich immunosorbent assay with the advantages of clean mass spectra and high enrichment of analytes. Antibody-modified metal nanoparticles (Ab-MNPs; M = Au or Ag) act as metallic biocodes for the LDI-MS detection. The signal amplification readout for the virus is through the pulsed laser-induced formation of metal cluster ions ([M n]+; n = 1-3) from the Ab-MNPs which specifically bind on the CAM. Our sensing system is effective for the detection of intact viruses [Enterovirus 71 (EV71) and Japanese encephalitis virus (JEV)], nonstructural protein 1 (NS1) of Zika virus (ZIKV), EV71-spiked human serum samples, and the simultaneous detection of EV71 and ZIKV. Our probe efficiently detects EV71 in real clinical serum samples with >95% agreement with RT-qPCR results. This high-throughput LDI-MS viral detection system is simple, reliable, and high-throughput. We believe this platform has the potential to be employed for the routine screening of patients with viral infections.

Physically-crosslinked anion exchange membranes by blending ionic additive into alkyl-substituted quaternized PPO

An additive-induced physically crosslinked system for use as anion exchange membranes was developed by blending an additive (DHBQA) containing both long alkyl (C12, dodecyl) and quaternary ammonium groups into a dodecyl-substituted and quaternary ammonium-functionalized PPO (poly(2,6-dimethyl-1,4-phenylene oxide)) (C12-PPO-QA). The additive, whose diammonium groups act as ion conductors, and whose long alkyl chains bind to the alkyl chains of the C12-PPO-QA polymer through van der Waals interactions, induced the formation of ion clusters as well as physical crosslinking of the C12-PPO-QA polymer. Controlling the amount of additive to maximize its intermolecular interactions with the polymer resulted in a PPO-10.8 membrane (10.8 wt% of additive relative to polymer) with very high ion conductivities of 49.2 mS cm−1 at 20 °C and 107.6 mS cm−1 at 80 °C and low swelling ratios of 18.2% at 20 °C and 33.3% at 80 °C, as well as excellent mechanical and alkaline stability. The H2/O2 single cell performance using PPO-10.8 reached a maximum power density about 60 mW cm−2, higher than that of the PPO-0 sample.

Coupled Multimodal Dynamics of Hydrogen-Containing Ion Networks in Water-Deficient, Sodium Hydroxide-Aluminate Solutions

The (meta)stability of low water activity sodium hydroxide/aluminate (Na+OH-/Al(OH)4-) electrolytes dictates kinetics in the Bayer process for aluminum refining and high-level nuclear waste processing. We utilized quasi-elastic neutron scattering (QENS) and proton nuclear magnetic resonance spectroscopy (1H NMR) in extremely concentrated sodium aluminate solutions to investigate the picosecond (ps) to microsecond (ms) timescale motions of H-bearing species (Al(OH)4- monomers/clusters, OH- and H2O). In the QENS data, in contrast to typical liquids, no short-time translational diffusion was observed at 293 K, but two types of localized motions were found: (i) local backbone tumbling or a formation of large hydrated ion clusters on the order of 40-60 ps; and (ii) much slower, complex, and collective dynamics of the ensemble of H-bearing species on the order of 350-750 ps. Variable temperature, pulsed field gradient, diffusion-ordered 1H NMR was used to determine the ensemble translational motion along with relaxometry to calculate rotational correlation coefficients. The ensemble rotational correlation times were on the order of 184-300 ps from 1H NMR, which is consistent with the timescale of the QENS components. Complementary molecular dynamics simulation of NaOH solutions exhibit extensive ion networks potentially responsible for the observed dynamical coupling of water with the motion of large hydrated ion clusters. Understanding these collective motions will aid in predicting the behavior of complex solutions during aluminum production and during nuclear waste processing.

Evaluation of a New Reagent-Ion Source and Focusing Ion-Molecule Reactor for Use in Proton-Transfer-Reaction Mass Spectrometry.

We evaluate the performance of a new chemical ionization source called Vocus, consisting of a discharge reagent-ion source and focusing ion-molecule reactor (FIMR) for use in proton-transfer-reaction time-of-flight mass spectrometry (PTR-TOF) measurements of volatile organic compounds (VOCs) in air. The reagent ion source uses a low-pressure discharge. The FIMR consists of a glass tube with a resistive coating, mounted inside a radio frequency (RF) quadrupole. The axial electric field is used to enhance ion collision energies and limit cluster ion formation. The RF field focuses ions to the central axis of the reactor and improves the detection efficiency of product ions. Ion trajectory calculations demonstrate the mass-dependent focusing of ions and enhancement of the ion collision energy by the RF field, in particular for the lighter ions. Product ion signals are increased by a factor of 10 when the RF field is applied (5000-18 000 cps ppbv-1), improving measurement precision and detection limits while operating at very similar reaction conditions as traditional PTR instruments. Because of the high water mixing ratio in the FIMR, we observe no dependence of the sensitivity on ambient sample humidity. In this work, the Vocus is interfaced to a TOF mass analyzer with a mass resolving power up to 12 000, which allows clear separation of isobaric ions, observed at nearly every nominal mass when measuring ambient air. Measurement response times are determined for a range of ketones with saturation vapor concentrations down to 5 × 104 μg m-3 and compare favorably with previously published results for a PTR-MS instrument.

Tailoring the nanophase-separated morphology of anion exchange membrane by embedding aliphatic chains of different lengths into aromatic main chains

Tuning the hydrophilic/hydrophobic nanophase-separated morphology to enhance the conductivity is a considerable challenge in the field of anion exchange membranes (AEMs). Here, a series of novel aliphatic-aromatic copolymer AEMs were designed by embedding flexible alkyl chains of different lengths into rigid main chain of poly(ether sulfone). Compared to traditional aromatic polymer, the aliphatic-aromatic copolymers had more flexible main chains and longer hydrophobic segments, both of which promoted the nanophase separation and the formation of ionic clusters. Increasing aliphatic chain length made the ionic clusters larger and more interconnected, but too long aliphatic chain led to the formation of smaller ionic clusters because the ionic groups were far away from each other. An optimum length of the aliphatic chain (8 C) existed for the nanophase-separated morphology with the biggest ionic clusters (around 8 nm), with which the membrane showed the highest conductivity. A peak power density of 159 mW cm−2 was obtained for the cell incorporating the 8 C membrane. Based on these, this study reveals a new direction to create a tunable nanophase-separated morphology for high-performance AEMs.

Features of the methane clusters formation in supersonic jets of methane and its mixtures with monatomic gases

This work demonstrates the methane clusters formation in supersonic free jets of methane mixtures with helium and argon. The dependence of the clusterization process properties on the carrier gas, the volume fraction of methane in the mixture at the selected of gas jet parameters is shown. Impact of the methane dissociative ionization, and methane clusters fragmentation in the detector of the mass spectrometer on the process of condensation was demonstrated. The presence of protonated cluster ions of methane and the increase in their proportion with growing size of clusters was established. The formation of cluster ions with an attached methyl, methylene or methylidene was discovered.

Time-resolved measurements of electron density in nanosecond pulsed plasmas using microwave scattering

In this work, microwave scattering was utilized to measure the electron number density produced in a nanosecond-long high-voltage breakdown of air between two electrodes in a pin-to-pin configuration. The approach allows tracing the absolute electron number in the plasma volume during the high-voltage pulse and the plasma decay for wide range of plasma and discharge parameters. Electron number density decayed on the timescale of about several μs governed by plasma-chemical processes including dissociative recombination, three-body attachment and formation of cluster ions.

Cellulose Nanofiber-Graphene Oxide Biohybrids: Disclosing the Self-Assembly and Copper-Ion Adsorption Using Advanced Microscopy and ReaxFF Simulations.

The self-assembly of nanocellulose and graphene oxide into highly porous biohybrid materials has inspired the design and synthesis of multifunctional membranes for removing water pollutants. The mechanisms of self-assembly, metal ion capture, and cluster formation on the biohybrids at the nano- and molecular scales are quite complex. Their elucidation requires evidence from the synergistic combination of experimental data and computational models. The AFM-based microscopy studies of (2,2,6,6-tetramethylpiperidine-1-oxylradical)-mediated oxidized cellulose nanofibers (TOCNFs), graphene oxide (GO), and their biohybrid membranes provide strong, direct evidence of self-assembly; small GO nanoparticles first attach and accumulate along a single TOCNF fiber, while the long, flexible TOCNF filaments wrap around the flat, wide GO planes, thus forming an amorphous and porous biohybrid network. The layered structure of the TOCNFs and GO membrane, derived from the self-assembly and its surface properties before and after the adsorption of Cu(II), is investigated by advanced microscopy techniques and is further clarified by the ReaxFF molecular dynamics (MD) simulations. The dynamics of the Cu(II)-ion capture by the TOCNF and GO membranes in solution and the ion cluster formation during drying are confirmed by the MD simulations. The results of this multidisciplinary investigation move the research one step forward by disclosing specific aspects of the self-assembly behavior of biospecies and suggesting effective design strategies to control the pore size and robust materials for industrial applications.

Group IIB-VIA semiconductor oxide cluster ions

Metal oxide cluster ions, MnOm± (M = Zn, Cd) and HgnOm− of various stoichiometry have been generated from solid IIB-VIA semiconductor oxides targets, (ZnO(s), CdO(s), and HgO(s)) by using pulse laser desorption ionization time of flight mass spectrometry with a laser of λ = 355 nm. Analysis of mass spectral data indicates the formation of stoichiometric cluster ions viz., (ZnO)n=1-30+ and (CdO)n=1-40+ along with –O bound anions, (ZnO)n=1-30O−, (CdO)n=1-40O− and (HgO)n=1-36O− from their respective solids. Further, metal oxoanions such as ZnOn=2,3−, CdOn=2,3,6−, and HgOn=2,3,6,7− have also been noted signifying the higher coordination ability of both Cd and Hg with O/O2/O3 species.

The Effect of Ionic Aggregates on the Transport of Charged Species in Lithium Electrolyte Solutions

In this investigation we focus on the problem of modeling the transport of the charged species (lithium ions) in electrolyte solutions with moderate and high salt concentrations (0.1M to > 2M), and consider the Nernst-Planck equation as a model of such processes. First, using a combination of magnetic resonance imaging (MRI) and inverse modeling (IM) we demonstrate that at higher concentrations the Nernst-Planck equation requires negative transference numbers in order to accurately describe the concentration profiles obtained from experiments. The need for such a physically inconsistent constitutive relation indicates the loss of validity of the Nernst-Planck equation as a model for this process. Next we consider the formation of ion pairs and clusters as a possible effect responsible for the appearance of negative transference numbers and derive an extended version of the Nernst-Planck system which accounts for these additional species. However, a careful analysis of this model reveals that incorporation of ion-pairing effects into the modeling will not change the transference numbers inferred from the experimental data via inverse modeling. This demonstrates that physical effects other than formation of ion pairs and clusters must be incorporated into the Nernst-Planck model in order for it to correctly describe ion transport at higher salt concentrations. One prime candidate for such effects is the motion of the reaction surface resulting from dendrite growth.

Mechanistic insights into chloride ion detection from the atmospheric-pressure afterglow of an argon inductively coupled plasma

Detection of chloride ion from chlorinated compounds is influenced by cluster ion formation in the afterglow of an ICP.

Chemical kinetics in an atmospheric pressure helium plasma containing humidity.

Atmospheric pressure plasmas are sources of biologically active oxygen and nitrogen species, which makes them potentially suitable for the use as biomedical devices. Here, experiments and simulations are combined to investigate the formation of the key reactive oxygen species, atomic oxygen (O) and hydroxyl radicals (OH), in a radio-frequency driven atmospheric pressure plasma jet operated in humidified helium. Vacuum ultra-violet high-resolution Fourier-transform absorption spectroscopy and ultra-violet broad-band absorption spectroscopy are used to measure absolute densities of O and OH. These densities increase with increasing H2O content in the feed gas, and approach saturation values at higher admixtures on the order of 3 × 1014 cm-3 for OH and 3 × 1013 cm-3 for O. Experimental results are used to benchmark densities obtained from zero-dimensional plasma chemical kinetics simulations, which reveal the dominant formation pathways. At low humidity content, O is formed from OH+ by proton transfer to H2O, which also initiates the formation of large cluster ions. At higher humidity content, O is created by reactions between OH radicals, and lost by recombination with OH. OH is produced mainly from H2O+ by proton transfer to H2O and by electron impact dissociation of H2O. It is lost by reactions with other OH molecules to form either H2O + O or H2O2. Formation pathways change as a function of humidity content and position in the plasma channel. The understanding of the chemical kinetics of O and OH gained in this work will help in the development of plasma tailoring strategies to optimise their densities in applications.

Tuning the Properties and Self-Healing Behavior of Ionically Modified Poly(isobutylene-co-isoprene) Rubber

The focus of this work is on the nature of self-healing of ionically modified rubbers obtained by reaction of brominated poly(isobutylene-co-isoprene) rubber (BIIR) with various alkylimidazoles such as 1-methylimidazole, 1-butylimidazole, 1-hexylimidazole, 1-nonylimidazole, and 1-(6-chlorohexyl)-1H-imidazole. Based on stress–strain and temperature dependent DMA measurements, a structural influence of the introduced ionic imidazolium moieties on the formation of ionic clusters and, as a consequence, on the mechanical strength and self-healing behavior of the samples could be evidenced. These results are fully supported by a molecular-level assessment of the network structure (cross-link and constraint density) and the dynamics of the ionic clusters using an advanced proton low-field NMR technique. The results show distinct correlations between the macroscopic behavior and molecular chain dynamics of the modified rubbers. In particular, it is shown that the optimization of material properties with regard to...

Plasma Decay in the Afterglow of High-Voltage Nanosecond Discharges in Unsaturated and Oxygenated Hydrocarbons

Results of experimental and theoretical study of plasma decay in the afterglow of high-voltage nanosecond discharges in gaseous ethylene and dimethyl ether at room temperature and pressures from 2 to 20 Torr are presented. Using a microwave interferometer, the time behavior of the electron density in the range from 2 × 1010 to 3 × 1012 cm–3 during plasma decay is investigated. By processing the experimental data, the effective coefficients of electron–ion recombination as functions of the gas pressure are obtained. It is found that these coefficients substantially exceed the recombination coefficients of simple hydrocarbon ions. This distinction, as well as the increase in the effective recombination coefficient with pressure, is explained by the formation of cluster ions in three-body collisions, which recombine with electrons more efficiently than simple molecular ions. The coefficients of three-body conversion of simple molecular ions into cluster ions in the plasmas of ethylene and dimethyl ether, as well as the coefficients of recombination of electrons with cluster ions in these gases, are determined by analyzing the experimental data.

Quantification of gas phase hydrogen peroxide and methyl peroxide in ambient air: Using atmospheric pressure chemical ionization mass spectrometry with O2−, and O2−(CO2) reagent ions

Instrumentation and ion chemistry are described for the measurement of hydrogen peroxide (H2O2) and methyl peroxide (CH3OOH) in ambient air by chemical ionization mass spectrometry (CIMS). A CIMS, designed and certified for aircraft deployment, was used in this work. The reagent gas was ultrapure air containing 400ppm CO2. The resultant reagent ions, O2− and O2−(CO2), form cluster ions with CH3OOH and H2O2, respectively, and are monitored at 80m/z [O2−(CH3OOH)] and 110m/z [O2− (CO2)(H2O2)]. The CIMS instrument was periodically calibrated using gas-phase standards generated from aqueous solutions. A Carulite-200® catalyst was used to remove peroxides from ambient air to blank the system to account for variations in the ambient air matrix. H2O2 also forms a stable cluster ion with O2− though its calibration behavior was more complex than that for O2−(CO2) in ambient air. The instrument was deployed on the National Center for Atmospheric Research Gulfstream-V aircraft. Representative measurements from the May-June 2012 Deep Convective Clouds and Chemistry experiment spanning altitudes between 0 and 13km over the south-central midwest and southeastern United States are shown. Laboratory experiments, airborne experiments and theoretical molecular modeling approaches were utilized to identify and select reagent ions and to understand the ion-molecule reactions for the formation of peroxide-ion clusters in the ambient air matrix under tropospheric conditions. The analytical viability of a particular ion-molecule adduct was supported by ab-initio molecular orbital calculations.

Sequential Dihydrogen Desorption from Hydride-Protected Atomically Precise Silver Clusters and the Formation of Naked Clusters in the Gas Phase.

We report the formation of naked cluster ions of silver of specific nuclearities, uncontaminated by other cluster ions, derived from monolayer-protected clusters. The hydride and phosphine co-protected cluster, [Ag18(TPP)10H16]2+ (TPP, triphenylphosphine), upon activation produces the naked cluster ion, Ag17+, exclusively. The number of metal atoms present in the naked cluster is almost the same as that in the parent material. Two more naked cluster ions, Ag21+ and Ag19+, were also formed starting from two other protected clusters, [Ag25(DPPE)8H22]3+ and [Ag22(DPPE)8H19]3+, respectively (DPPE, 1,2-bis(diphenylphosphino)ethane). By systematic fragmentation, naked clusters of varying nuclei are produced from Ag17+ to Ag1+ selectively, with systematic absence of Ag10+, Ag6+, and Ag4+. A seemingly odd number of cluster ions are preferred due to the stability of the closed electronic shells. Sequential desorption of dihydrogen occurs from the cluster ion, Ag17H14+, during the formation of Agn+. A comparison of the pathways in the formation of similar naked cluster ions starting from two differently ligated clusters has been presented. This approach developed bridges the usually distinct fields of gas-phase metal cluster chemistry and solution-phase metal cluster chemistry. We hope that our findings will enrich nanoscience and nanotechnology beyond the field of clusters.

Triiodide and mixed tri-halide anions from negative ion electrospray ionization of alkali halide solutions

Electrospray ionization of alkali halide solutions in the negative ion mode results in the formation of cluster ions of the general formula, (MX)nX−. However, alkali iodides form triiodide anion, I3−, in high abundance in addition to cluster ions. Br3− ions are observed in low abundance. Also, mixed tri-halide anions, I2Y−, are observed in high abundance when a small amount (<1%) of KI is added to other alkali halide solutions. These results are explained by the uniquely different physical characteristics of lithium and the iodide ions compared with others in the series.

Experimental studies on ion mobility in xenon-trimethylamine mixtures

In this paper we present experimental results for ion reduced mobilities (K0) in gaseous trimethylamine, TMA—(CH3)3N, and xenon-TMA mixtures for reduced electric fields E/N between 7.5 and 60 Td and in the pressure range from 0.5 to 10 Torr, at room temperature. Both in the mixtures and in pure TMA only one peak was observed in the time of arrival spectra, which is believed to be due to two TMA ions with similar mass, (CH3)3N+ (59 u) and (CH3)2CH2N+ (58 u), whose mobility is indistinguishable in our experimental system. The possibility of ion cluster formation is also discussed. In pure TMA, for the E/N range investigated, an average value of 0.56 cm2V−1s−1 was obtained for the reduced mobility of TMA ions. For the studied mixtures, it was observed that even a very small amount of gaseous TMA (∼0.2%) in xenon leads to the production of the above referred TMA ions or clusters. The reduced mobility value of this ion or ions in Xe-TMA mixtures is higher than the value in pure TMA: around 0.8 cm2V−1s−1 for TMA concentrations from 0.2% to about 10%, decreasing for higher TMA percentages, eventually converging to the reduced mobility value in pure TMA.

Investigation on Production of Cluster Ions Using Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

Surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) has become an indispensable tool in analysis of macromolecule and small molecule in solid and liquid samples. However, there were few studies focusing on the ionization mechanisms especially for the small molecules. In this work, the compounds of pyrene, coronene and rubrene with similar molecular structures were used to investigate the ionization mechanism via SALDI-MS. Additionally, the effect of laser power on product ions was also investigated. It was found that strong cluster ions peaks nM+ (M = pyrene, coronene) were observed for pyrene and coronene, and daughter ions of coronene by loss of C2H2 were also observed. On the contrary, no cluster ion was obtained for rubrene, only daughter ions with the losses of nC6H5 (n = 1, 2, 3) were acquired. Finally, the ionization mechanism was discussed. The formation of clusters of pyrene and coronene was attributed to the interaction of π-π bonds. For rubrene, the spatial barrier weakened the interaction of π-π bonds because the four phenyl groups were not on the same plane of skeleton structure, thus impeding the formation of cluster ions.

Synthesis and characterization of Torlon-based polyion complex for direct methanol and polymer electrolyte membrane fuel cells

An acid–base polyion complex membrane was synthesized by blending a polyamide-imide (Torlon) with sulfonated polyethersulfone (SPES), to make a sturdy proton-conducting electrolyte for portable fuel cells. The membrane was characterized by FTIR, XRD, TGA, SEM and UTM techniques. Chemical interactions between Torlon and SPES enabled the formation of ionic clusters that are useful for facilitating proton conduction and water sorption with prevention of fuel bypass. The complex exhibited high mechanical, thermal and oxidative stability with low methanol permeability (9.46 × 10−8 cm2/s). Sorption experiments showed the membrane to possess moderate affinity toward water with preferably low methanol uptake. Moreover, the blend membrane exhibited high proton conductivity (0.13 S/cm) at low humidity and high temperature conditions. To investigate the microstructure and transport behavior of the reported blend, molecular dynamics simulation based on COMPASS force field was performed. The diffusivity of hydronium ion obtained through simulation was used to calculate conductivity by Einstein equation. Proton conductivity obtained by simulation was validated by comparison with experimental data. Furthermore, the interaction of membrane functional groups with water and hydronium ion carrier was evaluated by radial distribution function. The study revealed the proposed complex to be an attractive, inexpensive alternative to state-of-the-art Nafion 117 membrane for fuel cell application.