Nanoparticle and Pore Size and Size Distribution by SAXS

Small-Angle X-ray Scattering (SAXS) measures how X-rays are deflected at very small angles by nanoscale variations in electron density within a material. By analyzing the shape and intensity of the scattering curve, researchers can reconstruct how matter organizes on the nanometer scale. This reveals the size, shape, and distribution of nanoparticles, as well as the dimensions of pores or voids in porous materials.
When calibrated in absolute intensity units, SAXS data can be used to extract quantitative physical parameters, including:

• Average particle or pore diameter, reflecting the characteristic size of the scatterers or voids
• Number- or volume-weighted size distribution, providing insight into polydispersity
• Volume fraction or mass concentration, obtained from absolute intensity normalization

Moreover, by integrating the signal from the entire particle or pore ensemble, SAXS provides statistically robust results. Consequently, the measurements represent the full sample rather than a limited subset.

Modern laboratory instruments can determine particle or pore sizes sizes ranging from approximately 1 to 900 nanometers with high precision with high precision. In addition, when equipped with a USAXS (Ultra-SAXS) extension, the accessible range extends up to several micrometers. Therefore, this enables the study of multimodal or hierarchical systems, including aggregation or agglomeration phenomena that often occur during synthesis, storage, or processing.

SAXS can be applied to a broad variety of materials, from liquids and soft matter to solids and complex functional devices. Moreover, the technique is non-destructive, requires only a small quantity of sample, and accommodates many different physical forms without extensive sample preparation.

Because X-rays penetrate deeply into matter, researchers can directly analyze even opaque suspensions or dense powders. Thus, this versatility enables the study of:

• Liquids and dispersions – colloids, emulsions, nanofluids
• Dry powders – metallic, ceramic, or organic nanoparticles
• Gels and pastes – hydrated or concentrated systems
• Porous or solid nanostructures – catalysts, coatings, nanocomposites, and battery or energy storage materials

Additionally, SAXS measurements can also be performed in situ or operando. This provides insight into particle growth, aggregation, phase transitions, or structural evolution under realistic conditions such as temperature, humidity, flow, or electrochemical cycling. This capability makes SAXS an essential tool for understanding how nanostructure changes during synthesis and operation, linking structural dynamics directly to material performance.

SAXS combines precision, representativeness, and versatility in a single measurement technique. It provides quantitative structural information across a wide size range, typically from one nanometer up to several micrometers, without altering or damaging the sample.

Overall, through these combined features, SAXS delivers a comprehensive understanding of how nanoscale architecture influences material performance, from catalysts and polymers to batteries, membranes, and biological assemblies.