Measurement of the Energy Dissipated in the Electrostatic Spraying Process

Huberman, M. N.

doi:10.1063/1.1658716

Cited by 31 publications

(12 citation statements)

References 3 publications

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“…We note, however, that the feature of a narrow ion energy distribution can be expected only from ions originating at the meniscus, and not from those coming from the jet breakup point or from the drops in the case where both drops and ions are issued. 8,15 Fortunately, this downstream contribution is negligible ͑current-wise͒ in the data of Fig. 3.…”

Section: ͑2͒mentioning

confidence: 92%

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Source of heavy molecular ions based on Taylor cones of ionic liquids operating in the pure ion evaporation regime

Romero‐Sanz

Bocanegra

Mora

et al. 2003

Journal of Applied Physics

207

170

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Section: ͑2͒mentioning

confidence: 92%

“…V a has been inferred previously from stopping potential curves, 15 and found to be one or a few hundred volts below the needle potential, both for the ions and the drops. 14,9,16 It is therefore safe to take V a to be within 80%-90% of the needle voltage.…”

Section: ͑2͒mentioning

confidence: 98%

Source of heavy molecular ions based on Taylor cones of ionic liquids operating in the pure ion evaporation regime

Romero‐Sanz

Bocanegra

Mora

et al. 2003

Journal of Applied Physics

207

170

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“…We note, however, that earlier vacuum electrospray studies conducted with glycerol solutions observed a multitude of solvated ions including metastable ions and multiply charged species. 3,31,32,103 In general, the emitted cluster ions recorded in the MD simulations contain more nascent formamide molecules (that is, they are characterized by larger solvation numbers) than the clusters observed in the experiments where typical flight times (that is, the elapsed time between the instant of cluster generation and the moment of its detection) are of the order of 30 µs. The recorded occurrence of larger solvated ion clusters is likely to be correlated with the propensity of the solvent (formamide) to form hydrogen bonds (see Figures 11c-e).…”

Section: Discussionmentioning

confidence: 99%

“…Huberman 31 conducted an energy analysis of positive ions sprayed from a NaI-glycerol solution, and detected a feature that was attributed to metastable solvated ions losing a solvent molecule. Stimpson et al 32 Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

et al. 2008

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The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that forms being characterized by high surface-normal electric field strengths in the vicinity of 1 V/nm. Mass-to-charge ratios were determined for both positive and negative currents sprayed from NaI−formamide solutions with solute−solvent mole ratios of 1:8.4 and 1:36.9, and from KI−formamide solutions with mole ratios of 1:41 and 1:83. The molecular dynamics simulations were conducted on isolated 10 nm NaI−formamide droplets at mole ratios of 1:8 and 1:16. The droplet was subjected to a uniform electric field with strengths ranging between 0.5 and 1.5 V/nm. Both the experiments and simulations demonstrate a mixed charge emission regime where field-induced desorption of solvated ions and charged droplets occurs. The macroscopic parameters, such as average mass-to-charge ratio and maximum surface-normal field strengths deduced from the simulations are found to be in good agreement with the experimental work and consistent with electrohydrodynamic theory of cone-jets. The observed mass spectrometric Na+ and I− solvated ion distributions are consistent with a thermal evaporation process, and are correctly reproduced by the simulation after incorporation of the different flight times and unimolecular ion dissociation rates in the analysis. Alignment of formamide dipoles and field-induced reorganization of the positive and negative ionic charges in the interfacial region are both found to contribute to the surface-normal field near the points of charge emission. In the simulations the majority of cluster ions are found to be emitted from the tip of the jet rather than from the neck region next to the Taylor cone. This finding is consistent with the experimental energy distributions of the solvated ions which demonstrate that indeed most ions are emitted closer to the jet region, that is, beyond the cone-neck region where ohmic losses occur. This observation is also consistent with continuum electrohydrodynamic predictions of cluster-ion evaporation at surface regions of high curvature and therefore maximum surface electric field strengths, which may be the cone-neck region, the breakup region of the jet (usually near the tip of the jet), or the emitted charged droplets. In the nanoscale jets observed in this study, the regions of highest spatial curvature are at the ends of the jets where nascent drops either are forming or have just detached. The energetics, interfacial properties, instabilities, and fragmentation patterns of electrosprays made from formamide salt solutions are investigated in a mass spectrometric vacuum electrospray experiment and using molecular dynamics (MD) simulations. The electrospray source is operated in a Taylor cone-jet mode, with the nanojet that form...

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“…But the very high viscosity of this liquid is associated with small ionic mobilities and hence with electrical conductivities smaller than 0.05 S/m ͑a 19.3% solution by weight of NaI in glycerol has an electrical conductivity of 0.021 S/m͒. 29 The only report we know of a substance other than a liquid-metal leading to the evaporation of high currents of ions is for sulfuric acid. 13 This behavior corresponds clearly to a situation where the electrical conductivity is already too high (Kϳ10 S/m) for the transition between negligible to measurable ionic currents to be observable.…”

Section: A Working Fluid To Create Fields Eè1 Võnm In Vacuummentioning

confidence: 99%

Direct measurement of ion evaporation kinetics from electrified liquid surfaces

Gamero-Castaño¹,

Mora²

2000

The Journal of Chemical Physics

141

122

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When concentrated solutions of NaI in formamide with electrical conductivities K larger than 1.1 S/m are electrosprayed from a Taylor cone-jet in a vacuum, ions are evaporated at substantial rates from the surface of the meniscus and the drops. This constitutes a new source of ions and nanoparticles, where the relative importance of these two contributions is adjustable. The currents of ions are measured independently from those associated with drops by a combination of stopping voltage analysis and preferential scattering in a gas background. The magnitude E of the electric field at the surface of the drops and at the apex of the cone-jet is controlled through the electrical conductivity K of the liquid and its flow rate Q through the jet. E is related through available scaling laws for Taylor cone-jets to the ratios K/Q or I/Q, where I is the current of drops emitted by the jet. Ion currents are very small or null at typical K/Q values used in the past. A relatively small initial ion current is attributed to a few particularly sharp features present, perhaps associated with small satellite drops. At still higher K/Q this first ionization source saturates, and ion evaporation from the main drops begins to dominate (Eϳ1 V/nm). E can then be determined with little ambiguity, and the associated ion current is also measured over a broad enough range of electric fields to determine the ionization kinetics. At still higher K/Q the ion current from the drops approaches saturation, and ion evaporation directly from the meniscus becomes dominant. The total spray current then presents the anomaly of increasing rapidly at decreasing liquid flow rate. The ion current from the meniscus can also be measured in this regime over a broad range of K/Q, with qualitative agreement with the ionization measurements from the drops. But the relation established between K/Q and E becomes suspect because ion and drop currents are now comparable. A third approach to infer the ionization rate is based on the related disappearance of Coulomb explosions of the drops above a critical K/Q. These results are congruent with the model of Iribarne and Thomson, with an activation barrier for ion evaporation equal to 1.7 eVϪ(e 3 E/4⑀ 0) 1/2 .

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Measurement of the Energy Dissipated in the Electrostatic Spraying Process

Cited by 31 publications

References 3 publications

Source of heavy molecular ions based on Taylor cones of ionic liquids operating in the pure ion evaporation regime

Source of heavy molecular ions based on Taylor cones of ionic liquids operating in the pure ion evaporation regime

Nanojets, Electrospray, and Ion Field Evaporation: Molecular Dynamics Simulations and Laboratory Experiments

Direct measurement of ion evaporation kinetics from electrified liquid surfaces

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