%A Ashley M. Smith
%T Quantitative Analysis of Metal Nanoparticle Ligand Shells
%X Nanoparticles (NPs) are used in an increasingly large number of applications ranging from coatings to sensing. Gold (Au) NPs, in particular, are emerging as some of the most well-studied and versatile particle types due to their facile synthesis, high stability, and wide range of morphologies. For these and all colloidal NPs, the surface chemistry can significantly impact physical properties and performance in downstream applications. The first step in leveraging this tunability is to develop analytical approaches to describe surface chemical features. Here, we introduce analytical approaches and resulting chemical insights that allow one to quantify, predict, and control the extent of ligand exchange on a range inorganic NPs.

We present data to establish the dynamic range, chemical resolution, and substrate generality of our NMR-based ligand quantification approach. First, we determine ligand density values for thiolated single-moiety ligand shells. We then use these data to describe ligand exchange behavior with a second, thiolated molecule to identify trends in AuNP functionalization efficiency as a function of ligand properties and exchange methodologies. Finally, we use our quantification method to analyze a diversity of particle shapes, sizes, and compositions.

In the studied systems, several trends emerge that ultimately serve as design rules for the generation of well-controlled ligand shells on metal NPs. In particular, we find that AuNPs functionalized with thiolated molecules exhibit a range of exchange efficiencies that strongly depend on the structure of the existing ligand shell. Further, we demonstrate that ligand incorporation into the final ligand shell varies based on the strength of the ligand binding moiety and binding affinity to the AuNP, with stoichiometric loading more closely achieved in cases where the ligands have a weaker affinity for the NP as well as with ligands that exhibit limited intermolecular interactions. Finally, we discuss the ligand loading trends in relation to particle size, composition, and shapes to probe how these aspects of particle morphology may or may not influence the ligand loading. Taken together, the reported results provide advances in the fundamental understanding of mixed ligand shell formation and are important for the use of AuNPs in a variety of applications.
%D 2017
%K Gold nanoparticles, ligands, quantification, surface chemistry
%I University of Pittsburgh
%L pittir31472