scholarly journals The Law of Parsimony and the Negative Charge of the Bubbles

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1003
Author(s):  
Stoyan I. Karakashev ◽  
Nikolay A. Grozev
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Inorganic Ions ◽  
Md Simulations ◽  
Water Interface ◽  
Negative Change ◽  
Air Water Interface ◽  
The Right ◽  
Positively Charged ◽  
Theoretical Developments

Why the bubbles are negatively charged? This is almost 100 years old question, which many scientists have striven and still are striving to answer using the latest developments of the MD simulations and various physical analytical methods. We scrutinize with this paper the basic literature on this topic and conduct our own analysis. Following the philosophical law of parsimony: “Entities should not be multiplied without necessity”, we assume that the simplest explanation is the right one. It is well known that the negative change of the Gibbs free energy is a solid criterion for spontaneous process. Hence, we calculated the energies of adsorption of OH−, H3O+ and HCO3− ions on the air/water interface using the latest theoretical developments on the dispersion interaction of inorganic ions with the air/water interface. Thus, we established that the adsorption of OH− and HCO3− ions is energetically favorable, while the adsorption of H3O+ is energetically unfavorable. Moreover, we calculated the change of the entropy of these ions upon their transfer from the bulk to the air/water interface. Using the well-known formula ΔG = ΔH − TΔS, we established that the adsorption of OH− and HCO3− ions on the air/water interface decreases their Gibbs free energy. On the contrary, the adsorption of H3O+ ions on the air/water interface increases their Gibbs free energy. Thus, we established that both OH− and HCO3− ions adsorb on the air/water interface, while the H3O+ ions are repelled by the latter. Therefore, electrical double layer (EDL) is formed at the surface of the bubble–negatively charged adsorption layer of OH− and HCO3− ions and positively charged diffuse layer of H3O+ ions.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

scholarly journals Spectroscopic BIL-SFG Invariance Hides the Chaotropic Effect of Protons at the Air-Water Interface

Atmosphere ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 396 ◽  
Author(s):  
Simone Pezzotti ◽  
Marie-Pierre Gaigeot
Keyword(s):  
Water Structure ◽  
Md Simulations ◽  
Interfacial Structure ◽  
Water Interface ◽  
Sum Frequency ◽  
Hydronium Ion ◽  
Sum Frequency Generation Spectroscopy ◽  
Air Water Interface ◽  
Ph Conditions ◽  
Shed Light

The knowledge of the water structure at the interface with the air in acidic pH conditions is of utmost importance for chemistry in the atmosphere. We shed light on the acidic air-water (AW) interfacial structure by DFT-MD simulations of the interface containing one hydronium ion coupled with theoretical SFG (Sum Frequency Generation) spectroscopy. The interpretation of SFG spectra at charged interfaces requires a deconvolution of the signal into BIL (Binding Interfacial Layer) and DL (Diffuse Layer) SFG contributions, which is achieved here, and hence reveals that even though H 3 O + has a chaotropic effect on the BIL water structure (by weakening the 2D-HBond-Network observed at the neat air-water interface) it has no direct probing in SFG spectroscopy. The changes observed experimentally in the SFG of the acidic AW interface from the SFG at the neat AW are shown here to be solely due to the DL-SFG contribution to the spectroscopy. Such BIL-SFG and DL-SFG deconvolution rationalizes the experimental SFG data in the literature, while the hydronium chaotropic effect on the water 2D-HBond-Network in the BIL can be put in perspective of the decrease in surface tension at acidic AW interfaces.

Temperature Dependence of the Air/Water Interface Revealed by Polarization Sensitive Sum-Frequency Generation Spectroscopy

2018 ◽  
Author(s):  
Daniel R. Moberg ◽  
Shelby C. Straight ◽  
Francesco Paesani
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Potential Energy Function ◽  
Md Simulations ◽  
Sum Frequency Generation ◽  
Water Molecules ◽  
Water Interface ◽  
Sum Frequency ◽  
Air Water Interface ◽  
Frequency Generation

<div> <div> <div> <p>The temperature dependence of the vibrational sum-frequency generation (vSFG) spectra of the the air/water interface is investigated using many-body molecular dynamics (MB-MD) simulations performed with the MB-pol potential energy function. The total vSFG spectra calculated for different polarization combinations are then analyzed in terms of molecular auto-correlation and cross-correlation contributions. To provide molecular-level insights into interfacial hydrogen-bonding topologies, which give rise to specific spectroscopic features, the vSFG spectra are further investigated by separating contributions associated with water molecules donating 0, 1, or 2 hydrogen bonds to neighboring water molecules. This analysis suggests that the low frequency shoulder of the free OH peak which appears at ∼3600 cm−1 is primarily due to intermolecular couplings between both singly and doubly hydrogen-bonded molecules. </p> </div> </div> </div>

Surface Properties of Plastocyanin at an Air-water Interface

1973 ◽  
Vol 28 (7-8) ◽  
pp. 397-400 ◽  
Author(s):  
S. S. Brody
Keyword(s):  
Free Energy ◽  
Dipole Moment ◽  
Surface Pressure ◽  
Nitrogen Atmosphere ◽  
Water Interface ◽  
Maximum Value ◽  
Energy Of Mixing ◽  
Air Water Interface ◽  
Mixed Film ◽  
Free Energy Of Mixing

Abstract The area/molecule, A, and surface potential, ⊿V , of plastocyanin (pcyan) at an air-water inter­ face varies with pH. At a pH of about 8.6 a maximum value is obtained for A and ⊿V. At a surface pressure of 3 dyn/cm A and ⊿V are 375 Å2 and 325 mV, respectively. The dipole moment is 2050 milliDebyes. Pcyan and chlorophyll α (chl) form a mixed film (free energy of mixing and interaction is negative). At a concentration of [pcyan] / [chl] ≈ 1 a maximum interaction is observed both for ⊿V and A (at pH 7.8). Irradiation of the mixed film, in a nitrogen atmosphere, results in an increase in A and ⊿V.

Particle Flock Motion at Air–Water Interface Driven by Interfacial Free Energy Foraging

Langmuir ◽  
2019 ◽  
Vol 35 (34) ◽  
pp. 11066-11070 ◽  
Author(s):  
Tianqi Chen ◽  
Dilip K. Kondepudi ◽  
James A. Dixon ◽  
James F. Rusling
Keyword(s):  
Free Energy ◽  
Interfacial Free Energy ◽  
Water Interface ◽  
Air Water Interface

Thermodynamics of chemical reactions

2005 ◽  
Author(s):  
Boris S. Bokstein ◽  
Mikhail I. Mendelev ◽  
David J. Srolovitz
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Chemical Reactions ◽  
Chemical Reaction ◽  
Chemical Equilibrium ◽  
Chemical Species ◽  
Chemical Thermodynamics ◽  
Chemical Equation ◽  
Definition Of ◽  
The Right

This chapter is devoted to chemical equilibrium. We will use thermodynamics to answer two main questions: (1) ‘‘In which direction will a chemical reaction proceed?’’ and (2) ‘‘What is the composition of the system at equilibrium?’’ These are the oldest and most important questions in all of chemical thermodynamics for obvious reasons. The answers to these questions represent the foundation upon which all modern chemical technologies rest. Consider the following chemical reaction: . . . aA = bB ⇆ cC + dD. (5.1) . . . A, B, C, and D represent the chemical species participating in the reaction and a, b, c, and d are the stoichiometric coefficients of these species. We refer to the species on the left side of this chemical equation as reactants and those on the right as products. The reaction in Eq. (5.1) can either go forward, from left to right (reactants to products), or backward, from right to left (products to reactants). Therefore, we see that the definition of which we call reactants and which products is arbitrary. Assume that Eq. (5.1) occurs at constant temperature and pressure. Under these conditions, the direction of the reaction is determined by the sign of the change of the Gibbs free energy.

Sign in / Sign up

Export Citation Format

Share Document