Using reversed-phase liquid chromatography to monitor the sizes of Au/Pt core/shell nanoparticles

This paper describes the use of reversed-phase liquid chromatography (RPLC) to rapidly characterize Au/Pt core/shell nanoparticles (NPs) produced through seed-assisted synthesis. We monitored the sizes of Au/Pt core/shell NPs by using a porous silica-based RPLC column (pore size: ca. 100 nm) and 30 mM sodium dodecyl sulfate in deionized water as the mobile phase; the plot of the retention time with respect to the logarithm of the size of the Au NPs was linear (R2 = 0.997) for diameters falling in the range from 5.3 to 40.1 nm; from five consecutive runs, the relative standard deviations of these retention times were less than 0.4%. We used the optimal separation conditions of the RPLC system to study the effects that the rate of addition of the reducing agent and the volumes of the seed, shell precursor metal ion, and reducing agent solutions had on the sizes of the Au/Pt core/shell NPs. A good correlation existed between the sizes of the Au/Pt core/shell NPs determined through RPLC and those determined using transmission electron microscopy. RPLC appears to be a useful technique for monitoring the sizes of NPs and nanomaterials in general.