Computational and spectroscopic insights into 2-(3-methylureido)acetic acid (MUA) adsorption and sensing on coinage bimetallic nanoclusters

Ultrasmall bimetallic coinage nanoclusters are attractive platforms for drug delivery and chemical sensing because their electronic structure can be tuned by composition and surface functionalization. Here we use DFT, NCIs, and MD to examine how 2-(3-methylureido)acetic acid (MUA) binds to coinage clusters X6 and X4Y2 (X, Y = Ag, Au, Cu, Ni). Three binding motifs are considered, with the cluster approaching to the C O (MUA1), COOH (MUA2), or NH site (MUA3). For all metals, adsorption is exothermic and strongest when cluster interacts with the carbonyl oxygen, with particularly large binding energies for Ni- and Au-containing systems such as Ag4Ni2-MUA1, Cu4Ni2-MUA1 and Cu4Au2-MUA1. Changes in the frontier gap and the calculated recovery times point to composition-dependent conductivity and desorption kinetics, suggesting that these clusters can operate as reusable drug carriers and SERS-active sensing platforms. MD simulation on (111) metal slabs support cluster-level results and confirm robust MUA adsorption at room temperature.