Nanoparticle size is represented by APPS & APS. Which one is the correct practice of representation
In the European Union ‘nanomaterial’ means a natural, incidental or manufactured material containing particles, in an unbound state or as an aggregate or as an agglomerate and where, for 50 % or more of the particles in the number size distribution, one or more external dimensions is in the size range 1 nm-100 nm.
Primary particles. These are inorganic or organic structures held together by atomic or molecular bonding. They are the "fundamental" particles; they cannot be separated into smaller particles except by the application of ultrahigh energy. In any sample they are usually present at only a fraction of a percent.
Aggregates. These comprise two or more primary particles tightly bound together by rigid chemical bonding resulting from sintering or cementation, which is the coalescence of particles by processes other than heat/pressure, i.e., precipitation of ionic salts onto surfaces during manufacture. Aggregates are typically formed when powders are heated, compressed, or dried from suspension. They have a large interfacial area of contact between each particle and the force necessary to rupture these bonds is considerable. Aggregates constitute, for all practical purposes, the largest single fraction of any particle size distribution (PSD) that one can hope to achieve in formulation.
Agglomerates. These are collections of aggregates, loosely held together at point-to-point contact by weak electromagnetic forces, van der Waals forces, mechanical friction, and interlocking. Agglomerates are formed when fine particles are handled, shaken, rolled or stored undisturbed in a single position. They can readily be broken apart with proper dispersion techniques.
If the nanoparticles exist in a dry powder form and have formed aggregates then a reasonable primary particle size may be obtained by using either TEM or by calculating an average particle diameter using a measured BET surface area. It is important to point out that the difference observed between the calculated value from BET surface area and the TEM results is due to a small amount of surface being lost due to the primary particles forming aggregates.
If the aggregate particle size is preferred, a combination of microscopy or light scattering method, either dynamic or static light scattering, may be appropriate.
If your particles are suspended in a stable solution and have not formed aggregates, either TEM or dynamic light scattering method would provide good primary particle size information.
https://ec.europa.eu/jrc/sites/default/files/irmm_nanomaterials_(online).pdf
- Badges
- Science topic
- Similar topics
- Chemistry
- Nanotechnology
- Nanostructured Materials
- Nanoparticles