DNA-Mediated Morphological Control of Pd-Au Bimetallic Nanoparticles

Recent reports have shown that different DNA sequences can mediate the control of shapes and surface properties of nanoparticles. However, all previous studies have involved only monometallic particles, most of which were gold nanoparticles. Controlling the shape of bimetallic nanoparticles is more challenging, and there is little research into the use of DNA-based ligands for their morphological control. We report the DNA-templated synthesis of Pd-Au bimetallic nanoparticles starting from palladium nanocube seeds. The presence of different homo-oligomer DNA sequences containing 10 deoxy-ribonucleotides of thymine, adenine, cytosine, or guanine results in the growth of four distinct morphologies. Through detailed kinetic studies by absorption spectroscopy, scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM), we have determined the role of DNA in controlling Pd-Au nanoparticle growth morphologies. One major function of DNA is affecting various properties of the incoming metal atoms, including their diffusion and deposition on the Pd nanocube seed. Interestingly, nanoparticle growth in the presence of A10 follows an aggregative growth mechanism that is unique when compared to the other base oligomers. These findings demonstrate that DNA can allow for programmable control of bimetallic nanoparticle morphologies, resulting in more complex hybrid materials with different plasmonic properties. The capability to finely tune multimetallic nanoparticle morphology stems from the versatile structure that is unique to DNA in comparison to conventionally used capping agents in colloidal nanomaterial synthesis.