Get charged up: Nonlinear optical voltammetry for quantifying the thermodynamics and electrostatics of metal cations at aqueous/oxide interfaces

Hayes, Patrick L.; Malin, Jessica N.; Jordan, David S.; Geiger, Franz M.

doi:10.1016/j.cplett.2010.09.060

Cited by 53 publications

(72 citation statements)

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“…When compared to the pristine single layer graphene, the population of defects within the defected graphene film does not appear to significantly alter the Mg(II) ion surface coverage, at least within our detection limit of 6 × 10 9 alkaline earth metal ions/ cm 2 . 56 We conclude that all three interfaces studied here have a low density of bound Mg(II) ions. A summary of the previously published results over bare fused silica 56 and the current results from the pristine and defected graphene is presented in Table 1.…”

Section: Resultsmentioning

confidence: 87%

“…The initial surface charge densities determined earlier for the pristine graphene (−0.0049(8) C/m 2 ) and defected graphene (between −0.009(3) and −0.010(3) C/m 2 ) were used to help constrain the fit. As we have noted previously, 56,69 the Gouy−Chapman model assumes a symmetric (1:1 or 2:2) analyte, which does not match our system of mixed monovalent and divalent electrolytes. While an expression for relating the interfacial potential to a 2:1:1 electrolyte solution has been derived, we are prevented from using this derivation as it cannot be expressed in a closed form for substitution into eq 2.…”

Section: Resultsmentioning

confidence: 95%

“…An in-depth analysis of these assumptions is available in a previous publication covering the sensitivity of the χ (3) method. 56 In this sensitivity analysis, we reported SHG signal detection limits as low as 10 −7 − 10 −8 V with 0.3 μJ input pulse energy. 56 As evident by eq 2, a decrease of the SHG intensity can be attributed to a decrease in the interfacial potential due to charge screening caused by the adsorption of counterions.…”

Section: Introductionmentioning

confidence: 95%

“…56 In this sensitivity analysis, we reported SHG signal detection limits as low as 10 −7 − 10 −8 V with 0.3 μJ input pulse energy. 56 As evident by eq 2, a decrease of the SHG intensity can be attributed to a decrease in the interfacial potential due to charge screening caused by the adsorption of counterions. Tracking the change of I SHG with increasing electrolyte concentration can produce valuable interface specific parameters, such as surface charge density, interfacial potential, and subsequently thermodynamic binding parameters.…”

Section: Introductionmentioning

confidence: 95%

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Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

et al. 2014

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This work reports thermodynamic and electrostatic parameters for fused silica/water interfaces containing cm(2)-sized graphene ranging from a single layer of pristine graphene to defected graphene. Second harmonic generation (SHG) measurements carried out at pH 7 indicate that the surface charge density of the fused silica/water interface containing the defected graphene (-0.009(3) to -0.010(3) C/m(2)) is between that of defect-free single layer graphene (-0.0049(8) C/m(2)) and bare fused silica (-0.013(6) C/m(2)). The interfacial free energy of the fused silica/water interface calculated from the Lippmann equation is reduced by a factor of 7 in the presence of single-layer pristine graphene, while defected graphene reduces it only by a factor of at most 2. Subsequent SHG adsorption isotherm studies probing the Mg(2+) adsorption at the fused silica/water interface result in fully reversible metal ion interactions and observed binding constants, Kads, of 4(1) - 5(1) × 10(3) M(-1) for pristine graphene and 3(1) - 4(1) × 10(3) M(-1) for defected graphene, corresponding to adsorption free energies, ΔGads, referenced to the 55.5 molarity of water, of -30(1) to -31.1(7) kJ/mol for both interfaces, comparable to Mg(2+) adsorption at the bare fused silica/water interface. Maximum Mg(2+) ion densities are obtained from Gouy-Chapman model fits to the Langmuir adsorption isotherms and found to range from 1.1(5) - 1.5(4) × 10(12) ions adsorbed per cm(2) for pristine graphene and 2(1) - 3.1(5) × 10(12) ions adsorbed per cm(2) for defected graphene, slightly smaller than those of for Mg(2+) adsorption at the bare fused silica/water interface ((2-4) × 10(12) ions adsorbed per cm(2)), assuming the magnesium ions are bound as divalent species. We conclude that the presence of defects in the graphene sheet, which we estimate here to be around 1.3 × 10(11) cm(2), imparts only subtle changes in the thermodynamic and electrostatic parameters quantified here.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 95%

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Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

et al. 2014

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“…The strength of the second harmonic electric field, E 2ω , that is produced at charged interfaces is a function of the incident fundamental electric field, E ω , the second-order susceptibility of the interface, χ (2) , the zero-frequency electric field corresponding to the interfacial potential produced by surface charges, Φ(0), and the third-order susceptibility, χ (3) , according to123456…”

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confidence: 99%

Phase-referenced nonlinear spectroscopy of the α-quartz/water interface

Ohno¹,

Saslow²,

Wang³

et al. 2016

Nat Commun

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253

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Probing the polarization of water molecules at charged interfaces by second harmonic generation spectroscopy has been heretofore limited to isotropic materials. Here we report non-resonant nonlinear optical measurements at the interface of anisotropic z-cut α-quartz and water under conditions of dynamically changing ionic strength and bulk solution pH. We find that the product of the third-order susceptibility and the interfacial potential, χ(3) × Φ(0), is given by (χ1(3)−iχ2(3)) × Φ(0), and that the interference between this product and the second-order susceptibility of bulk quartz depends on the rotation angle of α-quartz around the z axis. Our experiments show that this newly identified term, iχ(3) × Φ(0), which is out of phase from the surface terms, is of bulk origin. The possibility of internally phase referencing the interfacial response for the interfacial orientation analysis of species or materials in contact with α-quartz is discussed along with the implications for conditions of resonance enhancement.

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Mineral–Water Interaction

Gaigeot

Sulpizi

2016

Molecular Modeling of Geochemical Reactions

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Get charged up: Nonlinear optical voltammetry for quantifying the thermodynamics and electrostatics of metal cations at aqueous/oxide interfaces

Cited by 53 publications

References 54 publications

Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

Phase-referenced nonlinear spectroscopy of the α-quartz/water interface

Mineral–Water Interaction

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