Nano? Are you sure? - Uncovering the truth behind inconsistent particle size data and the three key steps of dispersion

Have you ever encountered this situation?

 

You're using what's supposed to be nano-grade material — yet your product ends up feeling coarse, with visible micron-sized particles.

The supplier told you it was nano-grade — yet the particle size distribution chart shows micron levels, or even two peaks.

 

Feeling unsure?

We're here to help you get to the bottom of it.

 

 

When working with nano- and micron-scale materials, particle size is a key parameter with major implications. However, different particle size measurement techniques often yield seemingly contradictory results. The most common example is the significant discrepancy between particle sizes observed using Scanning Electron Microscopy (SEM) and those measured by Laser Diffraction Analyzers.

 

Actually, this discrepancy is not a measurement error — the difference stems from the distinct principles behind the two techniques. SEM gives a real image of the particles, showing their actual size in a more qualitative and localized way. Laser diffraction, on the other hand, uses a light scattering model to calculate volume-based size distributions, representing statistical and overall trends.

 

This difference often leaves R&D personnel wondering: Which measurement is more reliable? What is the actual particle size?

 

The answer actually depends on which type of particle size you're looking for — primary particle size or secondary particle size.

 

Primary vs. Secondary Particle Size: Definition and Application

 

Term	Definition	Measurement Methods	Description
Primary Particle Size	The actual geometric size of a single, primary particle (single crystal or unit particle)	SEM, TEM, AFM	Represents the intrinsic size of the material; related to surface area, reactivity, and other microscopic properties.
Secondary Particle Size	The size of particle aggregates caused by agglomeration, adsorption, or dispersion in liquid environments	Laser Diffraction, Dynamic Light Scattering (DLS)	More reflective of the dispersion state in practical applications; influences macroscopic properties such as transparency and rheology.

 

 

 

Why do nanoparticles tend to agglomerate?

 

Cause	Explanation
High specific surface area	Smaller particles tend to adsorb gases and moisture more easily, forming hydrogen bonds and van der Waals forces.
High surface energy	To minimize system free energy, nanoparticles are naturally driven to attract each other and form aggregates.
Unstable surface charge	If the surface zeta potential is unstable, spontaneous aggregation is likely to occur.
Lack of surface modification	Bare particles have high interfacial tension with solvents or resins, leading to poor dispersion and repulsive interactions.

 

Recommended Dispersion Methods for Nanoparticles:

In addition to material-related factors such as particle size, distribution, and morphology, the following three key strategies can significantly improve nanoparticle dispersion and reduce agglomeration:

1. Surface Modification: Modify the surface of particles using silane or organic coatings. This alters the surface properties of inorganic powders, enhancing compatibility with organic resins and improving particle stability to reduce agglomeration.
2. Mechanical Dispersion: Break up agglomerates using high-shear equipment. Conventional mixing is insufficient—equipment such as bead mills, ball mills, three-roll mills, or high-pressure homogenizers is required to effectively deagglomerate nanoparticles.
3. Use of Dispersing Agents: Add dispersants to prevent re-agglomeration and achieve long-term, stable dispersion.

 

 

Let's explain this in a more relatable way. Dispersing nanoparticles is kind of like making a great salad. To get that perfect bowl of flavors and textures, you need to:

1. Wash the lettuce and lightly oil the chicken—this helps the dressing stick better and makes the meat cook faster and stay tender.
2. Mix everything evenly—ingredients that were clumped together start absorbing flavor uniformly. Crush the big chunks like nuts and boiled eggs to create a more pleasant mouthfeel.
3. Add dressing—it acts like a barrier that keeps ingredients from sticking together again, maintaining the ideal taste and texture of the whole salad.

 

If you don't have the appropriate equipment or are facing ongoing challenges with nanoparticle dispersion, we offer customized surface modification, ready-to-use dispersions, and complete solution services. Please fell free to contact us.

 

#Nanoparticles #Dispersion #Agglomeration #ParticleSize #SurfaceModification