Video Experimental Relacionado

Updated: May 5, 2026

Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy

Probing the Structure and Dynamics of Interfacial Water with Scanning Tunneling Microscopy and Spectroscopy

Published on: May 27, 2018

¿Entropía o entalpía? La segunda generación armónica de láminas líquidas revela diferentes mecanismos de adsorción de

Shane W Devlin^1,2,3, David J Hoffman⁴, Jake D Koralek⁴

¹Department of Chemistry, University of California, Berkeley, California 94720, United States.

Journal of the American Chemical Society

|August 8, 2025

Resumen

Los investigadores investigaron la adsorción de iones en las interfaces de líquidos utilizando espectroscopia avanzada. Descubrieron que las fuerzas motrices termodinámicas opuestas gobiernan el comportamiento de los iones en las interfaces aire-agua versus agua-heptano, impactando la química de los aerosoles y la catálisis.

Área de la Ciencia:

Química Física
Ciencias de la superficie
Espectroscopia

Sus antecedentes:

La adsorción de iones en las interfaces líquido-líquido es crucial para comprender la química heterogénea de los aerosoles, la catálisis "en el agua" y los sistemas biológicos.
Los estudios experimentales están limitados por los desafíos en la creación de interfaces limpias y la exploración de superficies enterradas.
Los esfuerzos teóricos han proporcionado la mayoría de las ideas sobre los mecanismos de adsorción de iones microscópicos.

Objetivo del estudio:

Investigar experimentalmente los detalles microscópicos de la adsorción de iones en una interfaz líquido-líquido hidrofóbico.
Para superar las limitaciones de los enfoques experimentales y teóricos anteriores.
Para revelar las fuerzas motrices termodinámicas para la adsorción de iones en interfaces distintas.

Principales métodos:

Utilizó láminas líquidas planas de flujo libre para crear interfaces estables y accesibles.
Se utiliza la espectroscopia de segunda generación armónica (SHG) de rayos UV profundos para la detección de superficies.
Las isotermas de Langmuir dependientes de la temperatura medidas para la adsorción de aniones tiocianato.

Principales resultados:

Adsorción de iones medida simultáneamente en las interfaces aire-agua y agua-heptano.
Información de fase obtenida a través de la interferencia de la señal entre múltiples interfaces.
Contribuciones entrópicas y entálpicas desenredadas a la energía libre de adsorción de Gibbs.

Conclusiones:

La adsorción aniónica exhibe fuerzas termodinámicas opuestas en las interfaces aire-agua y agua-heptano.
Los iones se estabilizan en la interfaz aire-agua por entalpía favorable.
Los iones se estabilizan en la interfaz agua-heptano por entropía favorable.

Más Videos Relacionados

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Interfacial Molecular-level Structures of Polymers and Biomacromolecules Revealed via Sum Frequency Generation Vibrational Spectroscopy

Published on: August 13, 2019

Author Spotlight: Unveiling the Potential of VSFG Microscopy in Studying Mesoscopically Heterogeneous Self-Assembled Structures

Author Spotlight: Unveiling the Potential of VSFG Microscopy in Studying Mesoscopically Heterogeneous Self-Assembled Structures

Published on: December 1, 2023

Videos de Conceptos Relacionados

Enthalpy of Solution

Enthalpy of Solution

There are two criteria that favor, but do not guarantee, the spontaneous formation of a solution:

Entropy

Entropy

Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...

Third Law of Thermodynamics

Third Law of Thermodynamics

A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero.

Entropy and Solvation

Entropy and Solvation

The process of surrounding a solute with solvent is called solvation. It involves evenly distributing the solute within the solvent. The rule of thumb for determining a solvent for a given compound is that like dissolves like. A good solvent has molecular characteristics similar to those of the compound to be dissolved. For example, polar solutions dissolve polar solutes, and apolar solvents dissolve apolar solutes. A polar solvent is a solvent that has a high dielectric constant (ϵ...

Entropy

Entropy

The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...

Entropy and the Second Law of Thermodynamics

Entropy and the Second Law of Thermodynamics

The second law of thermodynamics can be stated quantitatively using the concept of entropy. Entropy is the measure of disorder of the system.
The relation between entropy and disorder can be illustrated with the example of the phase change of ice to water. In ice, the molecules are located at specific sites giving a solid state, whereas, in a liquid form, these molecules are much freer to move. The molecular arrangement has therefore become more randomized. Although the change in average...