Kinetics of ion-mediated directed self-assembly of one-dimensional chains of metal nanoparticles in solution

The synergistic optical, electronic, and chemical properties of metal nanoparticles present in close proximity have potential applications in energy, medicine, and sustainability. Fundamental studies and application development based on spontaneous self-assembly of one-dimensional (1D) chains of metal nanoparticles without external organization agencies have been pursued for over four decades. The spontaneous formation of 1D chains in a solution of stabilized spherical nanoparticles may be driven by the emergence of local anisotropy due to dipolar interaction, representing a trapped non-equilibrium state. Here, the kinetics of this broken symmetry in the "directed" self-assembly of spherical particles is studied to form a 1D chain. The 1D chain assembly of 10 nm Au particles that had been stabilized by electrostatic repulsion is initiated by adding a small amount of divalent cation salt. A phenomenological model is presented to explain the transition state controlling the kinetics of the 1D self-assembly. Experimental and simulation studies were combined to measure the kinetics of the chain growth over time which revealed a sharp transition between two growth processes that were analogous to addition and condensation polymerization.