(Au-Ag)₁₄₄(SR)₆₀ alloy nanomolecules were synthesized and characterized by ESI mass spectrometry to atomic precision. The number of Ag atoms can be varied by changing the incoming metal ratio and plateaus at ∼60. UV-vis data demonstrates that the electronic structure of the nanomolecules can be tuned by incorporation of silver atoms. Based on the proposed 3-shell structure of Au₁₄₄(SR)₆₀, we hypothesize that the Ag atoms are selectively incorporated in to the symmetry equivalent 60-atom shell—having Au₁₂, Au₄₂, Ag₆₀ concentric shells with 30 –SR–Au–SR– protecting units.

Au_38−nAg_n(SCH₂CH₂Ph)₂₄ alloy nanomolecules were synthesized, purified and characterized by MALDI TOF mass spectrometry. Similar to 25 and unlike 144 metal atom count AuAg alloy nanomolecules, incorporation of Ag atoms here results in loss or smearing out of distinct UV-vis features. We propose that the short and long staples contain Au atoms, while the inner core consists of both Au and Ag atoms.