MALDI mass-spectrometry measurements are combined with self-consistent mean-field (SCF) calculations to detect and predict ligand phase separation on Ag nanoparticles. The experimental and theoretical techniques complement each other by enabling quantification of the nearest-neighbor distribution of a ligand mixture in a monolayer shell. By tracking a characteristic metallic fragment family, analysis of a MALDI spectrum produces a frequency distribution corresponding to specific ligand patterning. Inherent to the SCF calculation is the enumeration of local interactions that dictate ligand assembly. Interweaving MALDI and SCF facilitates a comparison between the experimentally and theoretically derived frequency distributions as well as their deviation from a well-mixed state. Thus, we combine these techniques to detect and predict phase separation in monolayers that mix uniformly or experience varying degrees of de-mixing, including microphase separation and stripe formation. Definition of MALDI removed as this is a commonly recognized technique.

MALDI mass-spectrometry measurements are combined with self-consistent mean-field (SCF) calculations to detect and predict ligand phase separation on Ag nanoparticles. The experimental and theoretical techniques complement each other by enabling quantification of the nearest-neighbor distribution of al igand mixture in am onolayer shell. By tracking ac haracteristic metallic fragment family,a nalysis of aM ALDI spectrum produces af requency distribution corresponding to specific ligand patterning. Inherent to the SCF calculation is the enumeration of local interactions that dictate ligand assembly.I nterweaving MALDI and SCF facilitates ac omparison between the experimentally and theoretically derived frequency distributions as well as their deviation from awell-mixed state.Thus,wecombine these techniques to detect and predict phase separation in monolayers that mix uniformly or experience varying degrees of de-mixing,i ncluding microphase separation and stripe formation. Definition of MALDI removed as this is ac ommonly recognized technique.The interfacial engineering of nanoparticles is an emergent area of research that is garnering significant interest for application in areas such as optics, [1] electronics, [2] and drug delivery. [3] Thus,i ti si mportant to exert control over the interface of nanoparticles,w hich dictates their degree of compatibility with and assembly in soft materials, [4] provides reactive sites for attachment of molecules,s uch as drug payloads, [3] and tunes the surface plasmon to awavelength of interest. [1] Thestarting point for interfacial modification is the self-assembled monolayer (SAM), or the layer of molecules (i.e., ligands) that form as hell around the nanoparticle.O ne strategy for controlling SAM properties involves the use of two or more ligands,r esulting in am ixed-ligand monolayer. On interfaces where ligands can attach and detach through adsorption/desorption equilibrium or move through surface diffusion, molecular simulations indicate that the phase separation of ligands occur for those with significant physical and/or chemical differences,s uch as alkane thiols with as ufficientc hain-lengthm ismatch. [5] Experimentally,e nsemble-basedm ethods,s ucha sF TIRs pectroscopy, or singlenanoparticle methods, such as scanning tunnelingm icroscopy (STM), have been used to interrogatel igandp hase separation. [6] However, such ensemble-based methodstypically yield semiquantitative resultso nm ixed ligand SAMs,a nd STM measurements of ligand phases eparationh aver ecentlyb een called into question. [7] Towardst he advancemento fs inglenanoparticle methods,w eh ave developed ac omplementary set of experimental and theoretical tools to probe the effects of nearest-neighbor interactions on ligand phase separation.Thee xperimental technique employed is MALDI mass spectrometry,a ne nsemble-based method which produces mass spectra of solid analytes through ionization with aU Vlaser, thereby accelerating analyte fragments towards ad etector that typically resolves species by time-of...