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.