Particle Characterisation
From nanoparticles to macroscopic surfaces: The complete characterisation portfolio for particle size, shape, and zeta potential
Carina Santner a, Franz Ferraz a, Henrique Brasil b
a. Application Specialist, Particle Analysis & Surface Charge, Anton Paar GmbH, Austria b. Product Manager, Particle Analysis & Surface Charge, Anton Paar GmbH, Austria
From nanometre-sized particles to larger surfaces, the physical and electrostatic properties of materials are key to understanding how they behave in real- world situations. Among these properties, the size, shape, and zeta potential of particles are especially important. These factors affect how well particles work, how stable they are, and how they interact with each other and their environment. For example, the size and shape of a particle can determine its surface area and reactivity. Zeta potential, which refl ects the surface charge, helps explain the forces that keep particles apart or bring them together. A high absolute zeta potential value usually means particles repel each other strongly, which helps prevent them from clumping together and keeps the system stable. Together, these characteristics are essential to understanding and controlling particle performance in fi elds such as nanotechnology, pharmaceuticals, and materials science.
Different characterisation techniques for a broad range of samples
Dynamic image analysis: Understanding particle size and shape
Dynamic image analysis is an advanced technique to measure particle size and shape simultaneously. Particles are dispersed and recorded in motion using a high-speed camera. Specialised software then analyses these images to extract precise measurements of size and shape. By evaluating thousands of particles, this method provides detailed statistics about their physical features, making it ideal for applications where particle shape matters as much as size, like quality control or material development.
The Litesizer DIA series uses dynamic image analysis to measure particles as small as 0.5 µm and as large as 16,000 µm, covering everything from fi ne powders to coarse granules. Its standout feature is its three interchangeable dispersion units:
• Liquid Flow: For analysing particles suspended in fl uids. • Dry Jet: For free-fl owing powders. • Free Fall: For fragile or sticky materials.
This fl exibility ensures optimal sample dispersion for both wet and dry samples. Figure 2: Litesizer DIF 500 with the Liquid Flow Dispersion Unit.
DLS and ELS for nanoparticle analysis and colloidal stability Dynamic light scattering (DLS) and electrophoretic light scattering (ELS) are well-established techniques for characterising particles in suspension. DLS measures particle size by tracking fl uctuations in the intensity of scattered light, which occur as particles move randomly (Brownian motion). ELS, on the other hand, measures the frequency shifts of scattered light from particles in an electric fi eld to calculate zeta potential, a key indicator of colloidal stability.
The Litesizer DLS series combines DLS for particle size, advanced cmPALS-based ELS for zeta potential, and static light scattering (SLS) for molecular mass determination. Additional measurement modes, such as transmittance, multi-angle particle sizing, refractive index, and particle concentration measurements further extend its capabilities. The Litesizer DLS supports a wide range of applications in pharmaceuticals, nanotechnology, polymer science, and environmental research.
Figure 1: Litesizer DIA series with its three dispersion units (Liquid Flow, Dry Jet, and Free Fall).
Laser diffraction: Fast and reliable particle size measurement Laser diffraction is a popular and reliable method for measuring the size distribution of particles in a sample. With this technique, a laser beam shines through the sample, and the particles scatter the light at different angles depending on their size. Larger particles scatter light at smaller angles, while smaller particles scatter at wider angles. By analysing the pattern and intensity of this scattered light, the particle size distribution can be accurately determined.
The Litesizer DIF 500 can measure a wide range of particle sizes, from as small as 10 nanometres up to 3.5 millimetres. It uses advanced optics with powerful 10 mW and 25 mW lasers, and can detect scattered light over an exceptionally wide range of angles – from 0.01 ° to 170 °. This allows for precise measurements across many different types of samples. To ensure stable and accurate results, the system includes shock-absorbing parts that reduce the impact of vibrations from the environment. The sensitive optical components are also protected inside strong metal housing, which keeps out dust and shields the system from direct bumps or shakes. These design features help maintain the accuracy of measurements and extend the life of the instrument.
Figure 3: Litesizer DLS particle analyser with automatic angle selection.
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