Monomer Ions Research Articles

Rapid Fingerprinting of High-Molecular-Weight Polymers by Laser Desorption-Ionization Using Through-Hole Alumina Membrane High-Resolution Mass Spectrometry

Residual acid found in the desorption ionization using through-holes alumina membranes (DIUTHAME) induces a reproducible protonation/in-source dissociation of polymers made of ester, amide, or siloxane moieties during their surface-assisted laser desorption ionization (SALDI) mass analysis. Deposited on the DIUTHAME chips in solution (solvent-based) or in pure form by melting the polymer powder in situ (solvent-free), high-molecular-weight nylons, silicone, or functionalized celluloses among other polymers are instantly fingerprinted by laser DIUTHAME high-resolution mass spectrometry (MS) with specific patterns resembling their direct analysis in real-time (DART) single-stage or tandem mass spectra. Depending on the polymer, two main types of fingerprints are observed with either the protonated monomer or product ions revealing the nature of the repeating unit or its functionalization. This technique allows a rapid molecular analysis of industrial homopolymers regardless of their molecular weight and complementary to DART with simple or no sample preparation and also promisingly applicable for copolymers.

A highly sensitive and selective sensor for trace uranyl (VI) ion based on a graphene-coated carbon paste electrode modified with ion imprinted polymer

Uranium is a kind of natural radionuclide, when the human body is exposed to higher uranium radioactive conditions, it will cause adverse effects on their health. Therefore, the analysis and detection of uranyl ions in the environment is a vital prerequisite for preventing uranium pollution. A bipolar bidentate ligand isophthalaldehyde-tetrapyrrole (IPTP) was first synthesized and a study was characterized by its structure and spectral properties. In the present work, an innovative electrochemical sensor by using IPTP as a ligand for uranyl (VI) ion (UO22+), α-methacrylic acid as functional monomer and uranyl (VI) ion as a template, a relatively stable structure was constructed by stirring at 35 °C. Then, the polymer sol-gel was acquired by combining sol-gel processing under alkaline conditions, which was added dropwise to the surface of a carbon paste electrode (CPE) which had been modified with graphene (GR). The introduction of graphene allowed the reduction peak current of uranyl ions to be increased significantly. Under the optimum experimental conditions (pH=5 and the adsorption time=20 min), the ion-imprinted sensor was designed by adopting differential pulse voltammetry (DPV) for the sensing of uranyl (VI) ions. The detection technique successfully achieved the determination of uranyl ion in the concentration range 1.0 × 10−10 mol L − 1 to 1.0 × 10−7 mol L − 1, in practical soil samples with excellent repeatability and recovery (97.3%-102.9%).

A Novel Electrochemical Sensor Based on Electropolymerized Ion Imprinted PoPD/ERGO Composite for Trace Cd(II) Determination in Water.

A novel electrochemical sensor based on electropolymerized ion imprinted poly (o-phenylenediamine) PoPD/electrochemical reduced graphene (ERGO) composite on glass carbon electrode (GCE) was fabricated for selective and sensitive determination of trace Cd(II) in water. ERGO was first deposited on the surface of GCE by electrochemical cyclic voltammetry (CV) scanning to enhance the electron transport activity at electrode surface. The ion imprinted polymer (IIP) of imprinted PoPD was then in situ electropolymerized on ERGO via CV scanning with oPD as functional monomer and Cd(II) ions as template, following removal of the template using electrochemical peroxidation method. The obtained imprinted PoPD/RERGO composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray energy spectroscopy (EDS) for the observation of their morphologies and components. The electrochemical behavior of the imprinted PoPD/ERGO/GCE was performed by CV and SWASV. The fabricated sensor of the imprinted PoPD/ERGO/GCE showed a good selectivity toward target Cd(II) ions in the presence of other heavy metal ions. Under the optimized experimental conditions, the sensor exhibited a good linear relationship between SWASV stripping peak values and Cd(II) concentration in the range of 1 to 50 ng/mL, with the limit of detection as 0.13 ng/mL (S/N = 3). The proposed electrochemical sensor of imprinted PoPD/ERGO/GCE was successfully applied for trace Cd(II) determination in real water samples.

Mass Isotopologue Distribution of dimer ion adducts of intracellular metabolites for potential applications in 13C Metabolic Flux Analysis.

13C Metabolic Flux Analysis (13C-MFA) is a powerful tool for quantification of carbon flux distribution in metabolic pathways. However, the requirement to obtain accurate labeling patterns, especially for compounds with low abundance, poses a challenge. Chromatographic separation and high sensitivity of the modern mass spectrometers (MS) alleviate this problem to a certain extent. However, the presence of derivatives such as in-source fragments, multimer ion adducts, and multiply charged ions result in reduced intensity of the molecular ion. While multimer ion adducts have been reported in the field of metabolomics, their presence is considered undesirable in quantitative studies. Here, we demonstrate a novel application of dimer ion adducts in calculating the mass isotopologue distribution (MIDs) of the corresponding monomer ions for public domain and in-house generated datasets comprising of 13C-labeling time-course experiments. Out of the 100 standard compounds analyzed, we could detect multimer ion adducts in 24 of the intermediate metabolites. Further, a subset of these multimer ions were detected in all the biological samples analyzed. Majority of these ion adducts were either not detected in the original study or labeled as a putative features. Regression analysis was performed to estimate the monomer MIDs from those of the dimer. This resulted in accurate estimation regardless of the biological system, chromatographic method, the MS hardware, or the relative abundance of the dimer ion. We argue that this analysis may be useful in cases where satisfactory data cannot be extracted from the chromatographic peaks of the monomer ions.

Cluster beams, nano-ripples, and bio applications

Gas cluster ions are aggregates of weakly bonded gas atoms or molecules. Upon the impact of an energetic gas cluster ion, multiple collisions occur between the target atoms and the atoms in the cluster ion. These impact processes are completely different from those of a collision-cascade process induced by a single atomic or molecular (monomer) ion. Although the impact process of gas cluster ions is different, ripples similar to those formed by monomer ions are formed by gas cluster ion impacts at oblique incidence. In this review, ripple formation by gas cluster ions is discussed with respect to their formation mechanism, characteristics, and applications as biosensors.

Experimental Study on the Biological Effect of Cluster Ion Beams in Bacillus subtilis Spores

Cluster ion beams have unique features in energy deposition, but their biological effects are yet to be examined. In this study, we employed bacterial spores as a model organism, established an irradiation method, and examined the lethal effect of 2 MeV C, 4 MeV C2, and 6 MeV C3 ion beams. The lethal effect per particle (per number of molecular ions) was not significantly different between cluster and monomer ion beams. The relative biological effectiveness and inactivation cross section as a function of linear energy transfer (LET) suggested that the single atoms of 2 MeV C deposited enough energy to kill the spores, and, therefore, there was no significant difference between the cluster and monomer ion beams in the cell killing effect under this experimental condition. We also considered the behavior of the atoms of cluster ions in the spores after the dissociation of cluster ions into monomer ions by losing bonding electrons through inelastic collisions with atoms on the surface. To the best of our knowledge, this is the first report to provide a basis for examining the biological effect of cluster ions.

Oxygen reduction reaction performance of Fe-N/C catalysts from ligand-iron coordinative supramolecular precursors

Simultaneous introduction of both transition metal and other inorganic elements into the carbon matrix has attracted great attention in the fabrication of carbon materials with high electrochemical properties. Herein, rational design of ligand-iron coordinative supramolecular precursors is achieved for the fabrication of Fe-N/C catalysts, which possess high oxygen reduction reaction (ORR) performance. A series of precursors are prepared by a simple coordination reaction between a three armed catechol monomer and iron ions. Particular interest is focused on tuning the doping species, surface area and morphology of the Fe-N/C catalysts through a simple selection of iron resources. We show that an Fe-N/C catalyst derived from Fe2(SO4)3 at a carbonization temperature of 800 °C, has the optimized ORR performance with an onset potential of 0.930 V and half-wave potential of 0.801 V. Detailed investigation indicates that the synergistic effect among doping elements of nitrogen and sulfur and the unique carbon structure determines the performance of the Fe-N/C catalysts. Our findings may be of significance for the fabrication of doped carbon materials using coordinative supramolecular polymers as precursors.

Reactive Tandem Ion Mobility Spectrometry with Electric Field Fragmentation of Alcohols at Ambient Pressure.

A tandem ion mobility spectrometer at ambient pressure with a reactive stage produced fragment ions by water elimination from protonated monomers of alcohols with carbon numbers three to nine. Protonated monomers of individual alcohols were mobility isolated in a first drift region and were fragmented to carbocations at 64 to 128 Td and 45 to 89°C. Precursor and fragment ions were mobility characterized in a second drift region. Enthalpies for fragmentation of ROH2+ to primary carbocations were calculated as 76 to 97 kJ/mol and enthalpies for subsequent charge migration to 2° carbocations were -49 to -58 kJ/mol. Plots of drift times for pairs of protonated monomer and fragment ions from alcohols, esters, alkanes, and aldehydes produced distinctive trend lines attributed to fragmentation paths characteristic of chemical class. Specific combinations of drift times for fragments and precursor ions provide additional chemical information for spectral interpretation in ion mobility spectrometry.

Fragmentation of Bi clusters by multiply charged ions

We report on collisions of multiply charged ions with free Bi nanoparticles in the gas phase. The nanoparticles contain up to 650 Bi atoms corresponding to a diameter of 3.5 nm. The stability limit of multiply charged Bi clusters has been investigated yielding appearance sizes for Bi clusters in charge states up to $q=6$, which are in good agreement with predictions of the liquid drop model. This finding underlines the metallic character of the Bi particles. By coincidence measurements the correlation between the dominant fragments ${\mathrm{Bi}}^{+}$ and ${{\mathrm{Bi}}_{3}}^{+}$ and larger multiply charged residues has been determined. The comparison of the kinetic energies with $Q$-value calculations within the liquid drop model allowed identifying specific decay processes as two-body asymmetric fission or multifragmentation events. The higher kinetic energies of singly charged monomer ions compared to that of trimer ions are explained by a higher fissility of the decaying system. Correlation islands for small fragments indicate different decay mechanisms based on two-step processes where a third undetected fragment can be emitted in the first or the second step.

Preparation and characterisation of a novel copper‐imprinted polymer based on β‐cyclodextrin copolymers for selective determination of Cu2+ ions

AbstractA novel ion‐imprinted polymer (IIP) using (6‐O‐butene diacid ester)‐β‐cyclodextrin (β‐CD‐MAH) as the functional monomer and copper ions as the template was developed for Cu2+ sensing. First, reactive β‐cyclodextrin (β‐CD) monomers with vinyl carboxylic acid functional groups were synthesised and were co‐polymerised with styrene via radical polymerisation. Then, the β‐CD copolymers were complexed with Cu2+ in order to obtain the IIP. The imprinting effect was realised by removing the template ions from the imprinted polymer. The structure, composition and morphology of the IIP were characterised by Fourier transform IR spectroscopy, energy‐dispersive spectroscopy and field‐emission SEM. The adsorption capacity was investigated by UV–visible spectroscopy in batch operation mode. The maximum adsorption capacity for the Cu2+ template ions was 28.91 mg g−1, and the adsorption selectivity was clearly illustrated from the increased sorption affinity towards Cu2+ ions over other competing ions. The adsorption was affected by the pH of the aqueous medium, and enhanced adsorption capacity was observed at pH 5. The prepared IIP could be used 10 times after its regeneration without significant loss of the adsorption capacity. © 2018 Society of Chemical Industry

Pressure dependence of singly and doubly charged ion formation in a HiPIMS discharge

Generation of singly charged Ar+ and Ti+, doubly charged Ar2+ and Ti2+, and of Ar2+ and Ti2+ dimer ions in a high power impulse magnetron sputtering (HiPIMS) discharge with a Ti cathode was investigated. Energy-resolved mass spectrometry was employed. The argon gas pressures varied between 0.5 and 2.0 Pa. Energy spectra of monomer ions are composed of low- and high-energy components. The energetic position of the high-energy component is approximately twice as large for doubly charged ions compared to singly charged ions. Intensities of Ar2+ and Ti2+ dimer ions are considerably smaller during HiPIMS compared to dc magnetron sputtering.

Analysis of Petroleum Products by Gel Permeation Chromatography Coupled Online with Inductively Coupled Plasma Mass Spectrometry and Offline with Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

We have examined the aggregation behavior of a typical atmospheric residue feedstock by gel permeation chromatography (GPC). The size profiles for compounds containing sulfur, vanadium, and nickel were determined online from elemental detection by inductively coupled plasma (ICP) mass spectrometry. Four fractions that vary in aggregation state were analyzed by positive atmospheric pressure photoionization (APPI) 9.4 T Fourier transform ion cyclotron resonance mass spectrometry (APPI FT-ICR MS). Results showed an inverse relationship between fraction aggregate size and monomer ion yield and revealed that aggregation tendency did not correlate with higher polar or aromatic species abundance. Aggregation in the atmospheric residue more closely correlated with increased relative abundance of larger and more aliphatic compounds. The molecular composition of the GPC aggregate fractions suggests that nonpolar intermolecular forces between saturated, long-chain alkyl substituents contribute more to aggregation th...

Protein depletion with bacterial cellulose nanofibers

In this study, we have reported a novel fabrication technique for human serum albumin (HSA) imprinted composite bacterial cellulose nanofibers (MIP-cBCNFs) used for the depletion of HSA selectively from artificial blood plasma for proteomic applications. Molecular imprinting was achieved by using metal ion coordination interactions of N‑methacryloyl‑(l)‑histidinemethylester (MAH) monomer and Cu(II) ions. MAH-Cu(II)-HSA complex was polymerized with bacterial cellulose nanofibers (BCNFs) under constant stirring at room temperature. The characterization of the MIP-cBCNFs was carried out by FTIR-ATR, SEM, contact angle measurements and surface area measurements. The adsorption experiments of HSA onto the MIP-BCNFs and NIP-BCNFs from aqueous HSA solutions were investigated in a batch system. The selectivity of the MIP-cBCNFs was investigated by using non-template human transferrin (HTR), and myoglobin (Myo). The relative selectivity coefficients of the MIP-cBCNFs were calculated as 4.73 and 3.02 for HSA/HTR and HSA/Myo molecules, respectively. In addition, the depletion of HSA from artificial human plasma was confirmed by SDS-PAGE and 2-D gel electrophoresis. As a result, it has been shown that metal ion coordination interactions contribute to specific binding of template when preparing MIP-cBCNFs for the depletion of HSA with a high adsorption capacity, significant selectivity and reusability.

Advances in Asphaltene Petroleomics. Part 3. Dominance of Island or Archipelago Structural Motif Is Sample Dependent

Asphaltene structure is one of the most controversial topics in petroleum chemistry. The controversy is centered on the organization of aromatic cores within asphaltene molecules (single aromatic core, island and multiple aromatic core, archipelago) and specifically the inconsistency between the island model and the composition of the products derived from asphaltene pyrolysis/thermal cracking. Such products are consistent with the coexistence of island and archipelago asphaltene structural motifs. However, the archipelago model continues to lack the widespread acceptance of the petroleum community, in part due to mass spectrometry results in support of the island model. In the first and second part of this series, we demonstrated that the disproportionally high atmospheric pressure photoionization (APPI) ionization efficiency (monomer ion yield) of island species is due to weak nanoaggregation of large aromatic cores which do not extensively aggregate in toluene, whereas more archipelago-dominant fractio...

Mineralogical, nanostructural, and Ca isotopic evidence for non-classical calcium phosphate mineralization at circum-neutral pH

Growth pathways of calcium (Ca) phosphate minerals are still under debate, but non-classical growth pathways, which encompass any mode of growth involving attachment of primary particles instead of monomer ions, are currently thought to dominate over classical mechanisms under a wide range of growth conditions. Cation desolvation during ion-by-ion growth is associated with the preferential uptake of isotopically light Ca in Ca-bearing phases, so the Ca isotope composition of Ca-bearing minerals can help to elucidate the dominant growth mechanism. Here, we combine stable Ca isotope analysis with mineralogical characterization and nanoscale imaging of growth features to determine for the first time the rate-dependent Ca isotope fractionation during seeded growth of hydroxyapatite (HAP) involving an octacalcium phosphate (OCP) precursor. Our data reveal that growth rates are strongly attenuated by pH, and that Ca isotope fractionation between the solid and growth solution is independent of growth rate between 1.9 × 10−9 and 2.8 × 10−8 mol Ca m−2 s−1. Moreover, nanoscale images of surface topography reveal direct deposition of primary particles on the HAP seed surface following sustained growth, providing visual evidence of a non-classical growth pathway. Together, these findings support the hypothesis that hydroxyapatite growth is dominantly non-classical. The process of cluster nucleation from the bulk solution and attachment of these clusters to the seeded HAP apparently does not involve a significant kinetic isotope effect, which implies that abiogenically formed Ca-phosphates likely preserve the Ca isotope composition of the fluid from which the crystals originated.

Advances in Asphaltene Petroleomics. Part 2: Selective Separation Method That Reveals Fractions Enriched in Island and Archipelago Structural Motifs by Mass Spectrometry

Advances in high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) enable molecular-level characterization of ultracomplex asphaltene samples. Such analyses most often reveal compounds that are highly aromatic but alkyl-deficient in nature and, thus, support the classical “island” model of asphaltene architecture. However, recent works that combine chromatographic separations with mass spectrometry for the analysis of crude oils have shown that differences in ionization may greatly affect the analysis of complex mixtures (known as the matrix effect). Simply, compounds that ionize with greater efficiency are preferentially observed and mask the detection of poorly ionized compounds. Asphaltenes are not immune to this phenomenon. In the first of this series (10.1021/acs.energyfuels.7b02873), it was demonstrated that asphaltenes generated by different precipitants showed greatly varied monomer ion yields (ionization efficiencies). This work focuses on the development of an ex...

High-energy collision-induced dissociation of histidine ions [His + H]+ and [His - H]- and histidine dimer [His2 + H

Histidine (His) is an essential amino acid, whose side group consists of an aromatic imidazole moiety that can bind a proton or metal cation and act as a donor in intermolecular interactions in many biological processes. While the dissociation of His monomer ions is well known, information on the kinetic energy released in the dissociation is missing. Using a new home-built electrospray ionization (ESI) source adapted to a double-focusing mass spectrometer of BE geometry, we investigated the fragmentation reactions of protonated and deprotonated His, [His + H]+ and [His - H]- , and the protonated His dimer [His2 +H]+ , accelerated to 6keV in a high-energy collision with helium gas. We evaluated the kinetic energy release (KER) for the observed dissociation channels. ESI of His solution in positive mode led to the formation of His clusters [Hisn + H]+ , n = 1-6, with notably enhanced stability of the tetramer. [His + H]+ dissociates predominantly by loss of (H2 O + CO) with a KER of 278meV, while the dominant dissociation channel of [His - H]- involves loss of NH3 with a high KER of 769meV. Dissociation of [His2 + H]+ is dominated by loss of the monomer but smaller losses are also observed. The KER for HCOOH loss from both [His + H]+ and [His - H]- is similar at 278 and 249meV, respectively, which suggests that the collision-induced dissociation takes place via a similar mechanism. The loss of COOH and C2 H5 NO2 from the dimer suggests that the dimer of His binds through a shared proton between the imidazole moieties.

Irradiation conditions of gas cluster ion beam for surface-activated bonding

The irradiation conditions of gas cluster ion beam (GCIB) for surface-activated bonding (SAB) were investigated. Since GCIB realizes bombardment with low energy (∼several eV/atom) and dense-energy deposition, it modifies the near-surface layer with low damage, which will be beneficial for surface-activated bonding. In this study, Cu–Cu bonding with GCIB irradiation was carried out as a preliminary study, and the irradiation conditions of Ar-GCIB were investigated. X-ray photoelectron spectroscopy (XPS) and contact angle measurements showed that the surface oxide on Cu was removed efficiently by oblique-incidence Ar-GCIB irradiations. Also, it was shown that sequential Ar-GCIB irradiations at normal and oblique incidences realized a smooth Cu surface. Cu–Cu bonding did not succeed for the pristine Cu or Cu irradiated with Ar monomer ions. In contrast, Cu–Cu bonding was realized with Ar-GCIB irradiation owing to surface oxide removal and smoothing effects.

Effect of dose and size on defect engineering in carbon cluster implanted silicon wafers

Carbon-cluster-ion-implanted defects were investigated by high-resolution cross-sectional transmission electron microscopy toward achieving high-performance CMOS image sensors. We revealed that implantation damage formation in the silicon wafer bulk significantly differs between carbon-cluster and monomer ions after implantation. After epitaxial growth, small and large defects were observed in the implanted region of carbon clusters. The electron diffraction pattern of both small and large defects exhibits that from bulk crystalline silicon in the implanted region. On the one hand, we assumed that the silicon carbide structure was not formed in the implanted region, and small defects formed because of the complex of carbon and interstitial silicon. On the other hand, large defects were hypothesized to originate from the recrystallization of the amorphous layer formed by high-dose carbon-cluster implantation. These defects are considered to contribute to the powerful gettering capability required for high-performance CMOS image sensors.

The structure of coronene cluster ions inferred from H2 uptake in the gas phase.

Mass spectra of helium nanodroplets doped with H2 and coronene feature anomalies in the ion abundance that reveal anomalies in the energetics of adsorption sites. The coronene monomer ion strongly adsorbs up to n = 38 H2 molecules indicating a commensurate solvation shell that preserves the D6h symmetry of the substrate. No such feature is seen in the abundance of the coronene dimer through tetramer complexed with H2; this observation rules out a vertical columnar structure. Instead we see evidence for a columnar structure in which adjacent coronenes are displaced in parallel, forming terraces that offer additional strong adsorption sites. The experimental value for the number of adsorption sites per terrace, approximately six, barely depends on the number of coronene molecules. The displacement estimated from this number exceeds the value reported in several theoretical studies of the bare, neutral coronene dimer.