Regioselective Deposition of Metals on Seeds within a Polymer Matrix

We use scanning probe block copolymer lithographyin a two-step sequential manner to explore the deposition ofsecondary metals on nanoparticle seeds. When single elementnanoparticles (Au, Ag, Cu, Co, or Ni) were used as seeds, bothheterogeneous and homogeneous growth occurred, as rationalizedusing the thermodynamic concepts of bond strength and latticemismatch. Specifically, heterogeneous growth occurs when theheterobond strength between the seed and growth atoms is strongerthan the homobond strength between the growth atoms. Moreover,the resulting nanoparticle structure depends on the degree of lattice mismatch between the seed and growth metals. Specifically, alarge lattice mismatch (e.g., 13.82% for Au and Ni) typically resulted in heterodimers, whereas a small lattice mismatch (e.g., 0.19%for Au and Ag) resulted in core-shell structures. Interestingly, when heterodimer nanoparticles were used as seeds, the secondarymetals deposited asymmetrically on one side of the seed. By programming the deposition conditions of Ag and Cu on AuNiheterodimer seeds, two distinct nanostructures were synthesized with (1) Ag and Cu on the Au domain and (2) Ag on the Audomain and Cu on the Ni domain, illustrating how this technique can be used to predictively synthesize structurally complex,multimetallic nanostructures

Automated summary

Scanning probe block copolymer lithography was used to explore the deposition of secondary metals on nanoparticle seeds in a two-step sequential manner. The occurrence of heterogeneous and homogeneous growth can be rationalized using the concepts of bond strength and lattice mismatch. The resulting nanoparticle structure depends on the degree of lattice mismatch, and heterodimer nanoparticles as seeds lead to asymmetric deposition of secondary metals.