Nanoscale Phase Segregation on Binary-Coated Nanoparticles Analyzed by MALDI-MS: Influence of Patchy Morphology

Nanoscale phase segregation of several ligands on nanoparticle surfaces is a key feature that strongly impacts on the nanoparticle properties and hence on their final applications. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has appeared as a powerful technique to characterize the surface phase segregation of binary mixtures of ligands in nanoparticle self-assembled monolayers. By comparing the mass spectra of clusters of ligands desorbed by MALDI with calculated random distribution, nanoparticles can be classified by their degree of nanophase segregation. Here, the influence of the selected cluster size and ligand ratio on the classification segregation parameters has been theoretically explored. Two different segregation procedures have been evaluated yielding two different morphologies, elongated and random patches. Results show that segregation parameters are influenced, apart from general segregation, by the morphology of patches. This influence is different depending on the size of the selected clusters of ligands enabling the use of segregation parameter ratios to obtain morphological information. The simultaneous analysis of different cluster sizes can then be used to expand the applicability of this powerful technique providing more complete information of the nanoscale phase segregation and, therefore, enabling a better understanding of the nanostructure–properties relationship.