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Leung K, Ilgen AG. Modeling separation of lanthanides via heterogeneous ligand binding. Phys Chem Chem Phys 2024. [PMID: 39018152 DOI: 10.1039/d4cp00880d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/19/2024]
Abstract
Individual lanthanide elements have physical/electronic/magnetic properties that make each useful for specific applications. Several of the lanthanides cations (Ln3+) naturally occur together in the same ores. They are notoriously difficult to separate from each other due to their chemical similarity. Predicting the Ln3+ differential binding energies (ΔΔE) or free energies (ΔΔG) at different binding sites, which are key figures of merit for separation applications, will help design of materials with lanthanide selectivity. We apply ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) to calculate ΔΔG for Ln3+ coordinated to ligands in water and embedded in metal-organic frameworks (MOFs), and ΔΔE for Ln3+ bonded to functionalized silica surfaces, thus circumventing the need for the computational costly absolute binding (free) energies ΔG and ΔE. Perturbative AIMD simulations of water-inundated simulation cells are applied to examine the selectivity of ligands towards adjacent Ln3+ in the periodic table. Static DFT calculations with a full Ln3+ first coordination shell, while less rigorous, show that all ligands examined with net negative charges are more selective towards the heavier lanthanides than a charge-neutral coordination shell made up of water molecules. Amine groups are predicted to be poor ligands for lanthanide-binding. We also address cooperative ion binding, i.e., using different ligands in concert to enhance lanthanide selectivity.
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Affiliation(s)
- Kevin Leung
- Geochemistry Department, MS 0750, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
| | - Anastasia G Ilgen
- Geochemistry Department, MS 0750, Sandia National Laboratories, Albuquerque, New Mexico 87185, USA.
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2
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Watts HD, Kubicki JD, Kabengi N. Connecting Thermodynamics of Alkali Ion Exchange on the Quartz (101) Surface with Density Functional Theory Calculations. J Phys Chem A 2022; 126:4286-4294. [PMID: 35762767 DOI: 10.1021/acs.jpca.2c02697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Periodic plane-wave density functional theory (DFT) calculations were performed on the α-quartz (SiO2) (101) surface to model exchange of adsorbed Li+ and either Na+, K+, or Rb+ in inner- and outer-sphere adsorbed, and aqueous configurations, which are charge-balanced with 2 Cl-. SiO- or SiOH groups represented the adsorption surface sites. The SiO- models included 58 H2O and 2 H3O+ molecules to approximate an aqueous environment, whereas the SiOH models had 59 H2O and 1 H3O+ molecules. The goal of this work is to calculate the heats of exchange for these alkali ions and to compare the results with those measured by flow microcalorimetry to ascertain the most probable mechanisms for these cations exchanging on the α-quartz (101) surface. Energy minimizations of each alkali ion adsorbed as outer-sphere complexes on SiOH surface sites, and as inner- and outer-sphere complexes on SiO- surface sites, were used to determine the energy of exchange (ΔEex) with Li+ for comparison with experimentally determined ΔHex values. Here, we present a novel method for calculating ΔEex using the difference in energies of geometry-optimized end member models. The aqueous and surface structures produced are similar to those observed experimentally. Although the trend for the calculated ΔEex values is consistent with those from the heats of exchange measured experimentally, the magnitude of our modeled ΔEex results is significantly larger than select experimental data from the literature [Peng, L. Zeta-Potentials and Enthalpy Changes in the Process of Electrostatic Self-Assembly of Cations on Silica Surface. Powder Technol. 2009, 193(1), 46-49]; we discuss the reasons for this discrepancy herein. The relative energy differences of the various configurations modeled have implications for the measurements of the surface charge via potentiometric titrations due to the more active role of alkali cations in quartz surface chemistry that have been previously considered as inert background electrolytes.
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Affiliation(s)
- Heath D Watts
- Department of Earth, Environmental & Resource Sciences, University of Texas at El Paso, El Paso, Texas 77968 United States
| | - James D Kubicki
- Department of Earth, Environmental & Resource Sciences, University of Texas at El Paso, El Paso, Texas 77968 United States
| | - Nadine Kabengi
- Department of Geosciences, Georgia State University, Atlanta, Georgia 30303, United States
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Leung K, Ilgen AG, Criscenti LJ. Interplay of physically different properties leading to challenges in separating lanthanide cations - an ab initio molecular dynamics and experimental study. Phys Chem Chem Phys 2021; 23:5750-5759. [PMID: 33662085 DOI: 10.1039/d1cp00031d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lanthanide elements have well-documented similarities in their chemical behavior, which make the valuable trivalent lanthanide cations (Ln3+) particularly difficult to separate from each other in water. In this work, we apply ab initio molecular dynamics simulations to compare the free energies (ΔGads) associated with the adsorption of lanthanide cations to silica surfaces at a pH condition where SiO- groups are present. The predicted ΔGads for lutetium (Lu3+) and europium (Eu3+) are similar within statistical uncertainties; this is in qualitative agreement with our batch adsorption measurements on silica. This finding is remarkable because the two cations exhibit hydration free energies (ΔGhyd) that differ by >2 eV, different hydration numbers, and different hydrolysis behavior far from silica surfaces. We observe that the similarity in Lu3+ and Eu3+ ΔGads is the result of a delicate cancellation between the difference in Eu3+ and Lu3+ hydration (ΔGhyd), and their difference in binding energies to silica. We propose that disrupting this cancellation at the two end points, either for adsorbed or completely desorbed lanthanides (e.g., via nanoconfinment or mixed solvents), will lead to effective Ln3+ separation.
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Affiliation(s)
- Kevin Leung
- Sandia National Laboratories, MS 1415, Albuquerque, NM 87185, USA.
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Saha S, Roy S, Mathi P, Mondal JA. Polyatomic Iodine Species at the Air-Water Interface and Its Relevance to Atmospheric Iodine Chemistry: An HD-VSFG and Raman-MCR Study. J Phys Chem A 2019; 123:2924-2934. [PMID: 30830779 DOI: 10.1021/acs.jpca.9b00828] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Iodine plays a key role in tropospheric ozone destruction, atmospheric new particle formation, as well as growth. Air-water interface happens to be an important reaction site pertaining to such phenomena. However, except iodide (I-), the behavior of other iodine species, for example, triiodide (I3-) and iodate (IO3-, the most abundant iodine species in seawater) at the aqueous interface and their effect on the interfacial water are largely unknown. Using interface-specific vibrational spectroscopy (heterodyne-detected vibrational sum frequency generation), we recorded the imaginary-χ(2) spectra (Imχ(2); χ(2) is the second-order electric susceptibility in OH stretch region) of the air-water interface in the presence of IO3-, I3-, and I- (≤0.3 M) in the aqueous subphase. The Imχ(2) spectra reveal that the chaotropic I3- is the most surface-active anion among the iodine species studied and decreases the vibrational coupling and hydrogen-bonding of interfacial water. Interestingly, the IO3-, even being a kosmotrope, is quite prevalent in the interfacial region and preferentially orients the interfacial water as "H-down" (i.e., water dipole moment is pointed toward the bulk water). Mapping of the OH stretch response of ion-affected water at interface (i.e., ΔImχ(2) = Imχ(2)air-water-iodine salt - Imχ(2)air-water) with that in the hydration shell of the respective ion (hydration shell water response is obtained by Raman multivariate curve resolution spectroscopy) reveals a correlative link between the ion's influence on the interfacial water and their hydration shell structure. The distinct water structure of stronger as well as weaker H-bonding in the hydration shell of the polyatomic IO3- anion promotes the anion to stay at the interfacial region. Thus, the surface prevalence of the iodine species and their effect on the interfacial water are perceived to be crucial for the transfer of iodine from seawater to the atmosphere across the marine boundary layer and the chemistry of iodine at aqueous aerosol surface.
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Affiliation(s)
- Subhamoy Saha
- Radiation & Photochemistry Division , Bhabha Atomic Research Centre, Homi Bhabha National Institute , Trombay, Mumbai 400085 , India
| | - Subhadip Roy
- Radiation & Photochemistry Division , Bhabha Atomic Research Centre, Homi Bhabha National Institute , Trombay, Mumbai 400085 , India
| | - P Mathi
- Radiation & Photochemistry Division , Bhabha Atomic Research Centre, Homi Bhabha National Institute , Trombay, Mumbai 400085 , India
| | - Jahur A Mondal
- Radiation & Photochemistry Division , Bhabha Atomic Research Centre, Homi Bhabha National Institute , Trombay, Mumbai 400085 , India
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Lützenkirchen J, Scharnweber T, Ho T, Striolo A, Sulpizi M, Abdelmonem A. A set-up for simultaneous measurement of second harmonic generation and streaming potential and some test applications. J Colloid Interface Sci 2018; 529:294-305. [DOI: 10.1016/j.jcis.2018.06.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 05/28/2018] [Accepted: 06/06/2018] [Indexed: 10/28/2022]
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DeWalt-Kerian EL, Kim S, Azam MS, Zeng H, Liu Q, Gibbs JM. pH-Dependent Inversion of Hofmeister Trends in the Water Structure of the Electrical Double Layer. J Phys Chem Lett 2017; 8:2855-2861. [PMID: 28561571 DOI: 10.1021/acs.jpclett.7b01005] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Specific ion effects (SIEs) are known to influence the acid/base behavior of silica and the interfacial structure of water, yet evidence of the effect of pH on SIEs is lacking. Here broadband vibrational sum frequency generation (SFG) spectroscopy was used to study SIEs on the water structure at the electrical double layer (EDL) of silica as a function of pH and monovalent cation identity from pH 2-12 at 0.5 M salt concentration. SFG results indicate a direct Hofmeister series of cation adsorption at pH 8 (Li+ < Na+ < K+ < Cs+), with an inversion in this series occurring at pH > 10. In addition, an inversion in SFG intensity trends also occurred at pH < 6, which was attributed to contributions from asymmetric cation hydration and EDL overcharging. The highly pH-dependent SIEs for silica/water have implications for EDL models that often assume pH-independent parameters.
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Affiliation(s)
- Emma L DeWalt-Kerian
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2R3, Canada
| | - Sun Kim
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2R3, Canada
| | - Md Shafiul Azam
- Department of Chemistry, Bangladesh University of Engineering and Technology (BUET) , Dhaka 1000, Bangladesh
| | - Hongbo Zeng
- Department of Chemical and Materials Engineering, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2R3, Canada
| | - Qingxia Liu
- Department of Chemical and Materials Engineering, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2R3, Canada
| | - Julianne M Gibbs
- Department of Chemistry, University of Alberta , 11227 Saskatchewan Drive, Edmonton, Alberta T6G 2R3, Canada
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Abstract
The physics and chemistry of mineral-water interfaces are complex, even in idealized systems. Our need to understand this complexity is driven by both pure and applied sciences, that is, by the need for basic understanding of earth systems and for the knowledge to mitigate our influences upon them. The second-order nonlinear optical techniques of second-harmonic generation and sum-frequency generation spectroscopy have proven adept at probing these types of interfaces. This review focuses on the contributions to geochemistry made by nonlinear optical methods. The types of questions probed have included a basic description of the structure adopted by water molecules at the mineral interface, how flow and porosity affect this structure, adsorption of trace metal and organic species, and dissolution mechanisms. We also discuss directions and challenges that lie ahead and the outlook for the continued use of nonlinear optical methods for studies of mineral-water boundaries.
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Affiliation(s)
- Paul A Covert
- Department of Chemistry, University of Victoria, V8W 3V6 Victoria, British Columbia, Canada;
| | - Dennis K Hore
- Department of Chemistry, University of Victoria, V8W 3V6 Victoria, British Columbia, Canada;
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Achtyl JL, Vlassiouk IV, Surwade SP, Fulvio PF, Dai S, Geiger FM. Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation. J Phys Chem B 2014; 118:7739-49. [DOI: 10.1021/jp410298e] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jennifer L. Achtyl
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Ivan V. Vlassiouk
- Measurement Science & System Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37931, United States
| | - Sumedh P. Surwade
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Pasquale F. Fulvio
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Sheng Dai
- Chemical
Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department
of Chemistry, University of Tennessee, Knoxville, Tennessee 37996, United States
| | - Franz M. Geiger
- Department
of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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Walter SR, Young KL, Holland JG, Gieseck RL, Mirkin CA, Geiger FM. Counting the number of magnesium ions bound to the surface-immobilized thymine oligonucleotides that comprise spherical nucleic acids. J Am Chem Soc 2013; 135:17339-48. [PMID: 24156735 DOI: 10.1021/ja406551k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Label-free studies carried out under aqueous phase conditions quantify the number of Mg(2+) ions binding to surface-immobilized T40 sequences, the subsequent reordering of DNA on the surface, and the consequences of Mg(2+) binding for DNA-DNA interactions. Second harmonic generation measurements indicate that, within error, 18-20 Mg(2+) ions are bound to the T40 strand at saturation and that the metal-DNA interaction is associated with a near 30% length contraction of the strand. Structural reordering, evaluated using vibrational sum frequency generation, atomic force microscopy, and dynamic light scattering, is attributed to increased charge screening as the Mg(2+) ions bind to the negatively charged DNA, reducing repulsive Coulomb forces between nucleotides and allowing the DNA single strands to collapse or coil upon themselves. The impact of Mg(2+) binding on DNA hybridization and duplex stability is assessed with spherical nucleic acid (SNA) gold nanoparticle conjugates in order to determine an optimal working range of Mg(2+) concentrations for DNA-DNA interactions in the absence of NaCl. The findings are consistent with a charge titration effect in which, in the absence of NaCl, (1) hybridization does not occur at room temperature if an average of 17.5 or less Mg(2+) ions are bound per T40 strand, which is not reached until the bulk Mg(2+) concentration approaches 0.5 mM; (2) hybridization proceeds, albeit with low duplex stability having an average Tm of 31(3)°C, if an average of 17.5-18.0 Mg(2+) ions are bound; and (3) highly stable duplexes having a Tm of 64(2)°C form if 18.5-19.0 Mg(2+) ions are bound, corresponding to saturation of the T40 strand.
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Affiliation(s)
- Stephanie R Walter
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States
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Saslow Gomez SA, Jordan DS, Troiano JM, Geiger FM. Uranyl adsorption at the muscovite (mica)/water interface studied by second harmonic generation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:11154-11161. [PMID: 22967014 DOI: 10.1021/es302879y] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Uranyl adsorption at the muscovite (mica)/water interface was studied by second harmonic generation (SHG). Using the nonresonant χ(3) technique and the Gouy-Chapman model, the initial surface charge density of the mica surface was determined to be -0.022(1) C/m(2) at pH 6 and in the presence of dissolved carbonate. Under these same conditions, uranyl adsorption isotherms collected using nonresonant χ(3) experiments and resonantly enhanced SHG experiments that probe the ligand-to-metal charge transfer bands of the uranyl cation yielded a uranyl binding constant of 3(1) × 10(7) M(-1), corresponding to a Gibbs free energy of adsorption of -52.6(8) kJ/mol, and a maximum surface charge density at monolayer uranyl coverage of 0.028(3) C/m(2). These results suggest favorable adsorption of uranyl ions to the mica interface through strong ion-dipole or hydrogen interactions, with a 1:1 uranyl ion to surface site ratio that is indicative of monovalent cations ((UO(2))(3)(OH)(5)(+), (UO(2))(4)(OH)(7)(+), UO(2)OH(+), UO(2)Cl(+), UO(2)(CH(3)COO(-))(+)) binding at the interface, in addition to neutral uranyl species (UO(2)(OH)(2) and UO(2)CO(3)). This work provides benchmark measurements to be used in the improvement of contaminant transport modeling.
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Affiliation(s)
- Sarah A Saslow Gomez
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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Holland JG, Geiger FM. Importance of length and sequence order on magnesium binding to surface-bound oligonucleotides studied by second harmonic generation and atomic force microscopy. J Phys Chem B 2012; 116:6302-10. [PMID: 22571519 DOI: 10.1021/jp301573g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The binding of magnesium ions to surface-bound single-stranded oligonucleotides was studied under aqueous conditions using second harmonic generation (SHG) and atomic force microscopy (AFM). The effect of strand length on the number of Mg(II) ions bound and their free binding energy was examined for 5-, 10-, 15-, and 20-mers of adenine and guanine at pH 7, 298 K, and 10 mM NaCl. The binding free energies for adenine and guanine sequences were calculated to be -32.1(4) and -35.6(2) kJ/mol, respectively, and invariant with strand length. Furthermore, the ion density for adenine oligonucleotides did not change as strand length increased, with an average value of 2(1) ions/strand. In sharp contrast, guanine oligonucleotides displayed a linear relationship between strand length and ion density, suggesting that cooperativity is important. This data gives predictive capabilities for mixed strands of various lengths, which we exploit for 20-mers of adenines and guanines. In addition, the role sequence order plays in strands of hetero-oligonucleotides was examined for 5'-A(10)G(10)-3', 5'-(AG)(10)-3', and 5'-G(10)A(10)-3' (here the -3' end is chemically modified to bind to the surface). Although the free energy of binding is the same for these three strands (averaged to be -33.3(4) kJ/mol), the total ion density increases when several guanine residues are close to the 3' end (and thus close to the solid support substrate). To further understand these results, we analyzed the height profiles of the functionalized surfaces with tapping-mode atomic force microscopy (AFM). When comparing the average surface height profiles of the oligonucleotide surfaces pre- and post- Mg(II) binding, a positive correlation was found between ion density and the subsequent height decrease following Mg(II) binding, which we attribute to reductions in Coulomb repulsion and strand collapse once a critical number of Mg(II) ions are bound to the strand.
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Affiliation(s)
- Joseph G Holland
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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Jordan DS, Saslow SA, Geiger FM. Exponential Sensitivity and Speciation of Al(III), Sc(III), Y(III), La(III), and Gd(III) at Fused Silica/Water Interfaces. J Phys Chem A 2011; 115:14438-45. [DOI: 10.1021/jp208843v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- David S. Jordan
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Sarah A. Saslow
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Franz M. Geiger
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
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Affiliation(s)
- Alberto Striolo
- School of Chemical, Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019, U.S.A
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Get charged up: Nonlinear optical voltammetry for quantifying the thermodynamics and electrostatics of metal cations at aqueous/oxide interfaces. Chem Phys Lett 2010. [DOI: 10.1016/j.cplett.2010.09.060] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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