Size and mobility of nanometer particles, clusters and ions

Tammet, Hannes

doi:10.1016/0021-8502(94)00121-e

Cited by 282 publications

(270 citation statements)

References 17 publications

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“…We therefore conclude the discussion with the final remark that the effects observed here for the first time had been advanced by Tammet's [19] warning that the accommodation coefficient depends on particle size. This suggest a revision of the common hypothesis that the collisions are inelastic (or elastic) independently of ion size.…”

Section: Relation Between Mobility Mass and Cluster Diametersupporting

confidence: 54%

“…This trend is in fact expected from the known tendency of very small clusters to reach densities larger than the bulk, as well as from the tendency for the collisions with the background gas to become more elastic [19]. What is surprising is the fact that these phenomena set in at such relatively large sizes and dominate initially over the opposing polarization effect.…”

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 86%

“…The m/z values at the center of each wave can be inferred from the m 1/3 data listed in Table 3 as a function of modulation number z and inverse mobility 1/Z. We now note that the mobility of a sphere with diameter d in the free-molecule range is given by eq 1 [19,20], where the subscript E is introduced as a reminder that this is just a model of limited generality: where, for aerosol particles in air, the coefficient ␤ is given by [21] ␤ ϭ 0.441 e(kT ⁄ ) 1⁄2 p (2)…”

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 88%

“…We note, nonetheless, that all previous studies using mobility-MS analysis have implicitly assumed that collisions with He atoms are elastic [22], even for rather large species such as proteins. In contrast, Tammet [19] has discussed the conditions under which transition from elastic to inelastic collisions would take place as the number of degrees of freedom increase, and he places it approximately at a cluster diameter of 2 nm. If the bulk density of the material composing the particle is and its value is not changed by the high curvature, we may relate the particle mass and diameter via:…”

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 99%

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Tandem mobility mass spectrometry study of electrosprayed tetraheptyl ammonium bromide clusters

Mora

Thomson

Gamero-Castaño

2005

J. Am. Soc. Mass Spectrom.

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Multiply charged electrospray ions from concentrated solutions of Heptyl 4 N ϩ Br Ϫ (designated A ϩ B Ϫ hereafter) in formamide are analyzed mass spectrometrically (MS) following mobility selection in ambient air in a differential mobility analyzer (DMA). Most of the sharp mobility peaks seen are identified as (AB) n A ϩ clusters, with 0 Յ n Յ 5. One anomalously abundant and mobile ion is identified as NH 4 ϩ (AB) 4 . Six ions in the (AB) n (A ϩ ) 2 series are also identified, completing and correcting earlier mobility data for singly and doubly charged ions up to masses of almost 9000 Da. The more mobile of two broad humps seen in the mobility spectrum includes m/z values approximately from 2500 up to 12,000 Da. It is formed primarily by multiply charged (AB) n (A ϩ ) z clusters with multiple ammonium bromide adducts. Because of overlapping of many peaks of different m/z and charge state z, only a few individual species can be identified by MS alone in this highly congested region. However, the spectral simplification brought about by mobility selection upstream of the MS reveals a series of broad modulations in m/z space, with all ions resolved in the second, third, . . .sixth modulation being in charge states z ϭ 2, 3, . . .6, respectively. Extrapolation of this trend beyond the sixth wave fixes the ion charge state (in some cases up to z ϭ 15) and mass (beyond m ϭ 175,000 u). This wavy structure had been previously observed and explained in terms of ion evaporation kinetics from volatile drops, though without mass identification. All observations indicate that the clusters are formed as charged residues, but their charge state is fixed by the IribarneThomson ion evaporation mechanism. Consequently, the measured curve of cluster diameter versus z yields the two parameters governing ion evaporation kinetics. Clusters with z Ͼ 1 and electrical mobility Z Ͼ 0.495 cm 2 /V/s are metastable and evaporate a singly charged cluster, probably (AB) 2 A ϩ , between the DMA and the MS. Plotting the electrical mobilities Z of the clusters in the form (z/Z) 1/2 versus m 1/3 (both proportional to cluster diameter) collapse the data for all cluster sizes and charge states into one single straight line for Z below 0.495 cm 2 /V/s. This linear relation reveals a uniform apparent cluster density of 0.935 g/cm 3 and an effective hard-sphere diameter of the air molecules of 0.44 nm. An anomalous mobility increase is observed at diameters below 3 nm. (J Am Soc Mass Spectrom 2005, 16, 717-732)

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Section: Relation Between Mobility Mass and Cluster Diametersupporting

confidence: 54%

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 86%

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 88%

Section: Relation Between Mobility Mass and Cluster Diametermentioning

confidence: 99%

See 2 more Smart Citations

Tandem mobility mass spectrometry study of electrosprayed tetraheptyl ammonium bromide clusters

Mora

Thomson

Gamero-Castaño

2005

J. Am. Soc. Mass Spectrom.

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“…For larger values of Ψ (much greater than unity), and for cluster ions significantly more massive than the background gas, the function L collapses to a form which leads to ion mobilities which are functions of neither the charge state nor the cluster diameter (the polarization limit) 53 . Combining equations (1a-d) leads to the relationship: …”

Section: Data Processing and Analysismentioning

confidence: 99%

Simultaneous ion and neutral evaporation in aqueous nanodrops: experiment, theory, and molecular dynamics simulations

Higashi

Tokumi

Hogan

et al. 2015

Phys. Chem. Chem. Phys.

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We use a combination of tandem ion mobility spectrometry (IMS-IMS, with differential mobility analyzers), molecular dynamics (MD) simulations, and analytical models to examine both neutral solvent (H2O) and ion (solvated Na + ) evaporation from aqueous sodium chloride nanodrops. For experiments, nanodrops were produced via electrospray ionization (ESI) of an aqueous sodium chloride solution. Two nanodrops were examined in MD simulations: a 2,500 water molecule nanodrop with 68 Na + and 60 Cl -ions (an initial net charge of z = +8), and (2) a 1,000 water molecule nanodrop with 65 Na + and 60 Cl -ions (an initial net charge of z = +5). Specifically, we used MD simulations to examine the validity of a model for the neutral evaporation rate incorporating both the Kelvin (surface curvature) and Thomson (electrostatic) influences, while both MD simulations and experimental measurements were compared to predictions of the ion evaporation rate equation of Labowsky et al [Anal Chim Acta, 2000, 406, 105-118]. To within a single fit parameter, we find excellent agreement between simulated and modeled neutral evaporation rates for nanodrops with solute volume fractions below 0.30. Similarly, MD simulation inferred ion evaporation rates are in excellent agreement with predictions based on the Labowsky et al equation. Measurements of the sizes and charge states of ESI generated NaCl clusters suggest that the charge states of these clusters are governed by ion evaporation, however, ion evaporation appears to have occurred with lower activation energies in experiments than was anticipated based on analytical calculations as well as MD simulations. Several possible reasons for this discrepancy are discussed.

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Kinetics of small ion evaporation from the charge and mass distribution of multiply charged clusters in electrosprays

2000

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The distribution of charge z and radii R in clusters electrosprayed from formamide solutions of tetraheptylammonium bromide was investigated by selecting those within a narrow range of electrical mobilities Z(1) in a first differential mobility analyzer (DMA), reducing their charge to unity by passage through a neutralizing chamber containing a radioactive (alpha) source, and measuring the mobilities Z(z) of the resulting discrete set of singly charged clusters in a second DMA. After correcting for the polarization contribution to cluster drag, the tandem DMA data yield the range of radii present at detectable levels for each charge state up to z = 9. Because small ion evaporation from electrospray drops leads to charge loss when a drop reaches a certain critical radius R(crit)(z), the measured maximum and minimum cluster radii associated with a given z can be used to infer the activation energy Delta for ion evaporation as a function of drop charge and curvature. These results confirm the Iribarne-Thomson ion-evaporation mechanism, and support earlier theoretical expressions for the functional form of Delta(z,R). The different phenomenon of ion evaporation from metastable multiply charged dry clusters is also observed at characteristic times of 1 s. Its activation energy is estimated as approximately 0.3 eV larger than for ion evaporation from the drops. This new process complicates the interpretation of the present measurements in terms of ion evaporation from liquid surfaces, but introduces no radical change in the picture. It helps understand why salt clusters with more than two or three charges are harder to see in mass spectrometers than in mobility studies under ambient conditions. Copyright 2000 John Wiley & Sons, Ltd.

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Size and mobility of nanometer particles, clusters and ions

Cited by 282 publications

References 17 publications

Tandem mobility mass spectrometry study of electrosprayed tetraheptyl ammonium bromide clusters

Tandem mobility mass spectrometry study of electrosprayed tetraheptyl ammonium bromide clusters

Simultaneous ion and neutral evaporation in aqueous nanodrops: experiment, theory, and molecular dynamics simulations

Kinetics of small ion evaporation from the charge and mass distribution of multiply charged clusters in electrosprays

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