The Interplay between Dynamics and Structure on the Dielectric Tensor of Nanoconfined Water: Surface Charge and Salinity Effect

Autor(es)

Coelho, Felipe Mourao ; Franco, Luis Fernando Mercier

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry B; v. 128, n. 47, p. 9-pg., 2024-11-16.

Resumo

Under confinement, the water dielectric constant is a second-order tensor with an abnormally low out-of-plane element. In our work, we investigate the dielectric tensor of an aqueous NaCl solution confined by a quartz slit-pore. The static dielectric constant is determined from local polarization density fluctuations via molecular dynamics simulations. In a pioneering investigation, we evaluate not only the effect of salinity but also surface charge. The parallel dielectric constant decreases with salinity due to dielectric saturation. From a dynamic perspective, the relaxation of water dipoles is slower within the hydration shells of ions. An anisotropic arrangement on the quartz surface results in preferred orientations of interfacial water molecules. By embedding charge, the surface structure changes, and extra dipole fluctuations in one direction may develop anisotropy in the parallel dielectric constant at the interface. Both surface charge and salinity increase the perpendicular dielectric constant. Nevertheless, the surface charge effect is more pronounced and may even recover the bulk dielectric constant value. The electric field established by the charged surface may disturb the planar hydrogen bond network at the interface, increasing out-of-plane dipolar fluctuations. Our work advances the knowledge of confined dielectric behavior, shedding light on the key role that charged surfaces play. (AU)

• Processo FAPESP: 20/13300-6 - Simulações de dinâmica molecular para estudo de propriedades de equilíbrio de misturas de fluidos confinados
• Beneficiário: Felipe Mourão Coelho
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto
• Processo FAPESP: 21/13068-9 - Termodifusão de CO2 em água: o impacto do gradiente geotérmico no sequestro de carbono em aquíferos salinos profundos via simulação molecular
• Beneficiário: Felipe Mourão Coelho
• Modalidade de apoio: Bolsas no Exterior - Estágio de Pesquisa - Doutorado Direto
• Processo FAPESP: 18/02713-8 - Dinâmica molecular de fluidos confinados: propriedades de equilíbrio e de transporte
• Beneficiário: Luís Fernando Mercier Franco
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores