Fig. 3.

(Color) XPS determined compositions of NH₂-SAMs on the 24 nm AuNP surface after undergoing a C11 NH₂-thiol ligand-exchange for different lengths of time (30 min to 61 days). The theoretical stoichiometric compositions for the C2 NH₂-thiol and C11 NH₁₁-thiol are also shown. The experimental data was renormalized without the Au, O, and Ti signals as discussed in the text.