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The solvation of electrons by an atmospheric-pressure plasma.

Rumbach P, Bartels DM, Sankaran RM, Go DB - Nat Commun (2015)

Bottom Line: The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer.We estimate an average penetration depth of 2.5 ± 1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination.Reactions with various electron scavengers including H(+), NO2(-), NO3(-) and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.

ABSTRACT
Solvated electrons are typically generated by radiolysis or photoionization of solutes. While plasmas containing free electrons have been brought into contact with liquids in studies dating back centuries, there has been little evidence that electrons are solvated by this approach. Here we report direct measurements of solvated electrons generated by an atmospheric-pressure plasma in contact with the surface of an aqueous solution. The electrons are measured by their optical absorbance using a total internal reflection geometry. The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer. We estimate an average penetration depth of 2.5 ± 1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination. Reactions with various electron scavengers including H(+), NO2(-), NO3(-) and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis.

No MeSH data available.


Related in: MedlinePlus

Absorbance behaviour in acidic solutions.Absorbance measurements for (H+)aq. The solid line is an analytical model that predicts the shift in the decay region to higher concentrations due to a competing reaction with (OH−)aq. Error bars represent the r.m.s. variance of the absorption signal at 90% confidence.
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f3: Absorbance behaviour in acidic solutions.Absorbance measurements for (H+)aq. The solid line is an analytical model that predicts the shift in the decay region to higher concentrations due to a competing reaction with (OH−)aq. Error bars represent the r.m.s. variance of the absorption signal at 90% confidence.

Mentions: We also studied the kinetics of the solvated electrons with (H+)aq derived from sulfuric acid (H2SO4) in a background solution of 0.163 M NaClO4. The experiments similarly showed a decrease in optical absorption with increasing scavenger concentration (Fig. 3). Note that the magnitude of the signal is significantly greater than the previous measurements. This is because the higher conductivity of the 0.163 M NaClO4 solution (15.5 mS cm−1) resulted in a larger current density, j, which caused the overall magnitude of the optical signal to become larger. Also, note that the critical concentration where the signal begins to decrease has been significantly shifted to higher concentrations, because second-order recombination, reaction (2), produces hydroxide (OH−), which will neutralize the acid in the interfacial region via


The solvation of electrons by an atmospheric-pressure plasma.

Rumbach P, Bartels DM, Sankaran RM, Go DB - Nat Commun (2015)

Absorbance behaviour in acidic solutions.Absorbance measurements for (H+)aq. The solid line is an analytical model that predicts the shift in the decay region to higher concentrations due to a competing reaction with (OH−)aq. Error bars represent the r.m.s. variance of the absorption signal at 90% confidence.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557361&req=5

f3: Absorbance behaviour in acidic solutions.Absorbance measurements for (H+)aq. The solid line is an analytical model that predicts the shift in the decay region to higher concentrations due to a competing reaction with (OH−)aq. Error bars represent the r.m.s. variance of the absorption signal at 90% confidence.
Mentions: We also studied the kinetics of the solvated electrons with (H+)aq derived from sulfuric acid (H2SO4) in a background solution of 0.163 M NaClO4. The experiments similarly showed a decrease in optical absorption with increasing scavenger concentration (Fig. 3). Note that the magnitude of the signal is significantly greater than the previous measurements. This is because the higher conductivity of the 0.163 M NaClO4 solution (15.5 mS cm−1) resulted in a larger current density, j, which caused the overall magnitude of the optical signal to become larger. Also, note that the critical concentration where the signal begins to decrease has been significantly shifted to higher concentrations, because second-order recombination, reaction (2), produces hydroxide (OH−), which will neutralize the acid in the interfacial region via

Bottom Line: The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer.We estimate an average penetration depth of 2.5 ± 1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination.Reactions with various electron scavengers including H(+), NO2(-), NO3(-) and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis.

View Article: PubMed Central - PubMed

Affiliation: Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556, USA.

ABSTRACT
Solvated electrons are typically generated by radiolysis or photoionization of solutes. While plasmas containing free electrons have been brought into contact with liquids in studies dating back centuries, there has been little evidence that electrons are solvated by this approach. Here we report direct measurements of solvated electrons generated by an atmospheric-pressure plasma in contact with the surface of an aqueous solution. The electrons are measured by their optical absorbance using a total internal reflection geometry. The measured absorption spectrum is unexpectedly blue shifted, which is potentially due to the intense electric field in the interfacial Debye layer. We estimate an average penetration depth of 2.5 ± 1.0 nm, indicating that the electrons fully solvate before reacting through second-order recombination. Reactions with various electron scavengers including H(+), NO2(-), NO3(-) and H2O2 show that the kinetics are similar, but not identical, to those for solvated electrons formed in bulk water by radiolysis.

No MeSH data available.


Related in: MedlinePlus