Studying the Internal Structure of Lamellar Systems

The SAXSpace system was used to characterize nano-structured lamellae present in a surfactant sample. The internal structure (core-shell) of the lamellae could be precisely determined.

Introduction

Small-Angle X-ray Scattering is a valuable tool to characterize samples containing nano-sized lamellae. These structures play an important role in several surfactant applications like detergents and drug carriers as well as in biomembranes.

SAXS allows you to gain an insight into the structure of such materials due to its sensitivity to electron density variations. Therefore the internal lamellar structure of such systems can be determined, i.e. the thickness of the core and the shell, lamella repeat distance and the long range order.

Experimental and Results

A surfactant sample was measured at 25 °C using the SAXSpace system. The background-subtracted scattering curve is shown in Figure 1. The power law decay of the scattering curve at small scattering angles is characteristic for a lamellar structure.


Fig.1 Background-subtracted scattering curve

The Pair-Distance Distribution Function (PDDF) was calculated using program GIFT1. The PDDF is a histogram of all distances within a particle and therefore represents the nanoparticle’s maximum size and its shape. In order to determine the internal structure of the lamellae, the PDDF was converted into the radial electron-density profile ("deconvolution") using program DECON1.


Fig. 2 Radial electron-density profile

The resulting radial electron-density profile (Figure 2) can be used to estimate the dimensions of the core-shell structure of the lamella:




1 O. Glatter, J. Phys.: Condens. Matter 18 (2006) 2403

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