Scientists in Sweden have shown that it is possible to sort and count nanoparticles, even once they have formed aggregates, which could be of importance in the cosmetics industry particularly for sunscreen formulators.
Nanoparticles of a substance can be counted and the size distribution can be determined by dispersing the nanoparticles into a gas, however researchers from the University of Gothenburg have studied a different method using aggregating systems.
"Nanoparticles are already used in many everyday products, such as sunscreen and cosmetics. It is important to be able to determine their size, shape and surface area, in order to be able to improve their properties within various areas of application," said Ann-Cathrin Johnsson of the Department of Chemistry at the University of Gothenburg.
Thesis focused on aggregating systems
Certain types of nanoparticles can start to aggregate in specific conditions, and sometimes a so called gel may form. Ann-Cathrin Johnsson's thesis work studied one of these aggregating systems; colloidal silica.
"I started with a method that had been used only for analysing nanoparticles that had not aggregated, and developed it further,” she explained.
“Nanoparticles that have aggregated can be analysed individually if a colloidal silica gel, which contains these aggregated nanoparticles, is first diluted and then dispersed into the gas phase. If the samples are analysed immediately after being diluted, this method gives an accurate picture of the gelated system.”
Different size, different properties
Given the scrutinizing that nanomaterials and nanotechnology are under, particularly in cosmetics, it could provide useful for formulators to be accountable for the number and size of particles in formulations.
A nanoparticle is a particle with a diameter that is much smaller than one millionth of a metre. Such small particles are not influenced by gravity and thus they do not fall to the bottom of a liquid or gas, and instead spread out throughout the container.
Their area of contact with the surrounding medium is very large due to their small size, and as a result there are many different and beneficial properties than that of larger particles of the same substance.