Modelless X-Ray Scattering Study of a Silica Hydrosol Surface

TL;DR

This study uses advanced X-ray scattering techniques to analyze the surface structure of silica hydrosols, revealing fundamental deviations from classical capillary-wave theory due to low-frequency roughness and interface interference.

Contribution

It provides a modelless, detailed analysis of silica hydrosol surfaces using synchrotron radiation, highlighting deviations from existing theoretical predictions.

Findings

Reconstructed electron density profiles perpendicular to the surface.

Identified deviations from capillary-wave theory predictions.

Attributed deviations to low-frequency roughness and interface interference.

Abstract

The structure of the adsorbed layer of alkali ions on the surface of colloidal silica solutions with a particle size of ~27 nm has been studied by reflectometry and diffuse scattering of synchrotron radiation with a photon energy of about 71 keV. Electron density profiles in the direction perpendicular to the surface have been reconstructed from experimental data and spectra of the correlation function of heights in the surface plane have been obtained. The revealed deviation of the integral and frequency characteristics of the roughness spectra of the silica sol surface from predictions of the capillary-wave theory is of a fundamental character. This deviation is due to the contribution from roughnesses with low spatial frequencies and to the interference of diffuse scattering from different layer interfaces of the surface structure.