Small molecule induced self-assembly of Au nanoparticles

Interest in one dimensional assemblies of metallic nanomaterials, particularly Au nanoparticles (NPs), has grown due to the optical properties and various applications of NPs in optoelectronics, biosensors, and nano-electronics. In general, one-dimensional alignments of Au nanostructures have been accomplished by using soft or hard templates, such as polymers, DNA, anodized aluminum oxide or even molecular templates. However, difficulties of nanoscale control and remnant byproducts through unwanted chemical reactions have become a limitation. In this paper, a no-template assembly was successfully carried out to produce one dimensional nanochains of Au NPs through N-ethyl-N'-(dimethylaminopropyl) carbodiimide (EDC) chemistry, where carboxylates on the surface of Au NPs are activated by EDC at room temperature. EDC is a fascinating candidate for nanomaterials assembly due to its easily chemical-activating ability as well as well-known biocompatibility. Physiochemical properties of the nanochains were characterized by TEM, AFM, UV/Vis, and FT-IR spectrophotometers, as well as zeta potential. Molecular dynamics (MD) simulations were also carried out in order to reveal the structuring mechanisms of the chains. Experimental and computational results indicate that the strong interaction between citrate-EDC-citrate and Au NPs was related to van der Waals forces and the Coulomb force of the functional groups, inducing delicate manipulation of the main bonding energy for self-assembly those NPs.