Using evolved gas analysis - mass spectrometry to characterize adsorption on a nanoparticle surface

The surface chemistry of nanoparticles is the key factor to control and predict their interactions with molecules, ions, other particles, other materials, or substrates, determining key properties such as nanoparticle stability or biocompatibility. In consequence, the development of new techniques or modification of classical techniques to characterize nanoparticle surfaces is of utmost importance. Here, a classical analysis technique, thermally evolved gas analysis - mass spectrometry (EGA-MS), is employed to obtain an image of the nanoparticle-solvent interface, unraveling the molecules present on the surface. As the use of complementary techniques is urged, the validity of EGA-MS characterization is corroborated by comparison with a previously reported surface characterization method. Previous studies were based on several experimental techniques and MD simulations using YF₃ nano/supraparticles and LaF₃ nanoparticles as model systems. We demonstrate the applicability of this technique in two differently sized systems and two systems composed of the same ions on their surface but with a different inorganic core (e.g. LaF₃ and YF₃ nanoparticles). The results described in this paper agree well with our previous results combining experimental techniques and MD simulations. EGA-MS not only revealed the ions attached to the nanoparticle surface but also shed light on their coordination (e.g. citrate attached to one or two carboxylate moieties). Thus, we show that EGA-MS is a useful and efficient technique to characterize the surface chemistry of nanoparticles and to control and predict their final properties.