U(VI) Adsorption and Speciation at the Acidic Silica/Water Interface Studied by Resonant and Nonresonant Second Harmonic Generation

Malin, Jessica N.; Holland, Joseph G.; Saslow, Sarah A.; Geiger, Franz M.

doi:10.1021/jp203091x

Cited by 24 publications

(28 citation statements)

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“…The surface-specificity of SFG makes this technique a perfect tool to probe the microscopic arrangement of molecules in the interfacial layers, and for this reason, it has been widely used to unravel the water structure at aqueous interfaces. There is no need to stress the relevance of aqueous interfaces in many fields, from the key role played by water-air interfaces in atmospheric chemistry [1][2][3][4], through the effect of the interfacial water structure on protein folding and peptide bond formation [5][6][7], to the importance of silica-water interfaces in pollutant transport in underground water in mineral dissolution but also for drug delivery in our bodies [8,9]. The unique molecular arrangement at aqueous interfaces is at the basis of all the cited phenomena and its characterization is henceforth pivotal.…”

Section: Introductionmentioning

confidence: 99%

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

et al. 2018

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Following our recent work [Phys. Chem. Chem. Phys. 20:5190–99 (2018)] that provided the means to unambigously define and extract the three water regions at any charged interface (solid–liquid and air–liquid alike), denoted the BIL (Binding Interfacial Layer), DL (Diffuse Layer) and Bulk, and how to calculate their associated non-linear Sum Frequency Generation Spectroscopy (SFG) χ2(ω) spectroscopic contributions from Density Functional Theory (DFT)-based ab initio molecular dynamics simulations (DFT-MD/AIMD), we show here that the χDL2(ω) signal arising from the DL water region carries a wealth of essential information on the microscopic and macroscopic properties of interfaces. We show that the χDL2(ω) signal carries information on the surface potential and surface charge, the isoelectric point, EDL (Electric Double Layer) formation, and the relationship between a nominal electrolyte solution pH and surface hydroxylation state. This work is based on DFT-MD/AIMD simulations on a (0001) α–quartz–water interface and on the air–water interface, with various surface quartz hydroxylation states and various electrolyte concentrations. The conclusions drawn make use of the interplay between experiments and simulations. Most of the properties listed above can now be extracted from experimental χDL2(ω) alone with the protocols given in this work, or by making use of the interplay between experiments and simulations, as described in this work.

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Section: Introductionmentioning

confidence: 99%

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

et al. 2018

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“…SHG is dipole forbidden in bulk media with inversion symmetry, but it can be generated from the surface and interfaces of nanoparticles where the inversion symmetry is broken. 37–39 The release of highly negatively charged miRNA from the surface of GNPs is an ideal candidate for SHG spectroscopy investigations. The SHG signal from this charged interface has two components given by the second-order susceptibility χ (2) , which is based on the two-photon spectroscopy, and the third-order susceptibility χ (3) , which is based on the electrostatic potential from the nanoparticle surface.…”

Section: Introductionmentioning

confidence: 99%

Monitoring the Photocleaving Dynamics of Colloidal MicroRNA-Functionalized Gold Nanoparticles Using Second Harmonic Generation

et al. 2015

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Photoactivated drug delivery systems using gold nanoparticles provide the promise of spatiotemporal control of delivery that is crucial for applications ranging from regenerative medicine to cancer therapy. In this study, we use second harmonic generation (SHG) spectroscopy to monitor the light-activated controlled release of oligonucleotides from the surface of colloidal gold nanoparticles. MicroRNA is functionalized to spherical gold nanoparticles using a nitrobenzyl linker that undergoes photocleaving upon ultraviolet irradiation. The SHG signal generated from the colloidal nanoparticle sample is shown to be a sensitive probe for monitoring the photocleaving dynamics in real time. The photocleaving irradiation wavelength is scanned to show maximum efficiency on resonance at 365 nm, and the kinetics are investigated at varying irradiation powers to demonstrate that the nitrobenzyl photocleaving is a one-photon process. Additional characterization methods including electrophoretic mobility measurements, extinction spectroscopy, and fluorimetry are used to verify the SHG results, leading to a better understanding of the photocleaving dynamics for this model oligonucleotide therapeutic delivery system.

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“…However, the pH dependence is minor under alkaline pH conditions because the surface deprotonation is complete and the surface site does not change anymore; this observation is in consistent with the experimental results. 6,7,[38][39][40] Moreover, at high pH values, the coordinating H 2 O ligands may be replaced by OH − , which may weaken the interaction between the surface sites and uranyl species. This phenomenon will be discussed in a later section.…”

Section: Resultsmentioning

confidence: 99%

“…These results are consistent with the experimental observations. [6][7][8][37][38][39][40][41] When the uranyl adsorbs on a surface covered by a monolayer of water, the coordination mode and geometry parameters are slightly changed, whereas the orientation of the water ligands slightly changes due to the interaction with the surrounding water molecules. The AIMD simulation employed on the water-silica model at 295.15 K showed that the aqua solution has little effect on the adsorption configuration, which is the similar to the DFT results without aqua solution.…”

Section: Resultsmentioning

confidence: 99%

“…[31][32][33][34][35][36] As a natural geologic material, silica is of great interest due to the abundance of silicate minerals in the environment, and its adsorption of uranyl has been studied experimentally. [6][7][8][37][38][39][40][41][42][43][44][45] However, to date, there are only few theoretical works to address this subject. It is thus highly desirable to characterize the adsorption of actinides on a silica surface.…”

Section: Introductionmentioning

confidence: 99%

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Adsorption of uranyl on hydroxylated α-SiO₂(001): a first-principle study

2015

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The adsorption of [UO2(H2O)5](2+) on a hydroxylated α-SiO2(001) surface was studied by periodic density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulation. The effects of pH, CO2, aqua solution and anionic ligands (OH(-), NO3(-) and Cl(-)) on the adsorption geometry and stability were investigated. The results show that the adsorption of uranyl on a hydroxylated α-SiO2(001) surface leads to the formation of inner-sphere complexes, in which the bidentate complex at the double deprotonated site is most favored. The binding strengths of bidentate and monodentate complexes at the same site are similar, and they become weaker as the number of protons increases at the adsorption site, indicating an enhancement of the adsorption strength at higher pH values within a certain range. Strong chemical interaction plays an important role in all inner-sphere complexes. The hydrogen bonds are formed between uranyl and the hydroxylated surface in all inner- and outer-sphere complexes. The presence of CO2 weakens the adsorption of uranyl on the surface by forming uranyl carbonate (CO3(2-), HCO3(-)) complexes. The effect of the anion ligands depends on their charged state and their concentration in solutions. The explicit treatment of water environment in the models has a slight effect on the adsorption configuration. These results are consistent with the experimental observations.

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U(VI) Adsorption and Speciation at the Acidic Silica/Water Interface Studied by Resonant and Nonresonant Second Harmonic Generation

Cited by 24 publications

References 73 publications

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

Monitoring the Photocleaving Dynamics of Colloidal MicroRNA-Functionalized Gold Nanoparticles Using Second Harmonic Generation

Adsorption of uranyl on hydroxylated α-SiO₂(001): a first-principle study

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U(VI) Adsorption and Speciation at the Acidic Silica/Water Interface Studied by Resonant and Nonresonant Second Harmonic Generation

Cited by 24 publications

References 73 publications

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

What the Diffuse Layer (DL) Reveals in Non-Linear SFG Spectroscopy

Monitoring the Photocleaving Dynamics of Colloidal MicroRNA-Functionalized Gold Nanoparticles Using Second Harmonic Generation

Adsorption of uranyl on hydroxylated α-SiO2(001): a first-principle study

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Adsorption of uranyl on hydroxylated α-SiO₂(001): a first-principle study