Effect of Mg Doping on Structural, Alloying, Electronic, Optical, and Bactericidal Properties of CunAg25-n Nanoclusters: A Computational Study

CuAg nanoparticles have been discussed in the literature for their bactericidal and localized surface plasmon resonance properties. The use of CuAg nanoparticles, however, faces the challenge of low miscibility between Cu and Ag. In this communication, employing first-principles calculations and classical molecular dynamics simulations, we demonstrate Mg doping at Ag sites to be a viable route to enhance the mixing tendency of the alloyed nanoclusters, while retaining the attractive bactericidal and localized surface plasmon resonance properties. The microscopic origin of enhanced mixing upon Mg doping is traced back to a depletion of the charge around the dopant and neighboring sites, which in turn causes charge accumulation in the interfacial region of the core-shell-like geometry of the clusters, resulting in enhancement of the covalency. This is evidenced in computed crystal orbital Hamiltonian populations. Calculated optical absorption shows that the Mg doping retains the strong absorption in the UV range, driving the surface plasmon resonance effect. Investigation of antimicrobial activity of the doped and undoped nanoparticles, by examining the DNA binding, establishes that Mg-doped CuAg clusters are even better bactericidal candidates, compared to undoped CuAg nanoparticles.