Ranking of As-Received Micro/Nanoparticles by their Surface Energy Values at Ambient Conditions

Abstract

Nanoparticles have been widely applied in many applications due to their specific physical or chemical properties that differ from the bulk counterparts. Because nanoparticles vary significantly in composition and geometry, the comparison of their interaction with another matter is difficult, although in many cases, to characterize and assort nanoparticles in a quantified way is highly desired. Among the many properties of nanoparticles, the surface energy is especially important in evaluating their potential affinity to the environment. Pretty elegant techniques have been developed to evaluate the surface energy of pure metal oxides. However, heating or acid treatment would destroy the real surface conditions, for example, organic coatings outside of the particles. An effective method has to be developed to determine the surface energy of the as-received natural particles, whether they are pure, contaminated, or prehydrated. We designed a technique to quantitatively evaluate the surface energy of the as-received nanoparticles. The surface energies of a series of as-received nanoparticles can be evaluated and ranked at ambient conditions without heating or acid/base treatment. The values obtained for TiO2 solid and for 0.1 μm aluminum particles match those records in the literature well. The result out of this research also enables the comparison between solid particles on different size levels, for example, from millimeter to the nanoscale. The surface energy of nanoparticles is closely related to their wettability performance. Therefore, the ranking of solids on a various size scales according to the surface energy would enable the quantitative study of their interactions with their environmental neighbors, for example, proteins and cells.