Laser desorption/ionization mass spectrometry analysis of monolayer-protected gold nanoparticles
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- Yan, B., Zhu, Z., Miranda, O.R. et al. Anal Bioanal Chem (2010) 396: 1025. doi:10.1007/s00216-009-3250-6
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Monolayer-protected gold nanoparticles (AuNPs) feature unique surface properties that enable numerous applications. Thus, there is a need for simple, rapid, and accurate methods to confirm the surface structures of these materials. Here, we describe how laser desorption/ionization mass spectrometry (LDI-MS) can be used to characterize AuNPs with neutral, positively, and negatively charged surface functional groups. LDI readily desorbs and ionizes the gold-bound ligands to produce both free thiols and disulfide ions in pure and complex samples. We also find that LDI-MS can provide a semi-quantitative measure of the ligand composition of mixed-monolayer AuNPs by monitoring mixed disulfide ions that are formed. Overall, the LDI-MS approach requires very little sample, provides an accurate measure of the surface ligands, and can be used to monitor AuNPs in complex mixtures.