DNA-mediated synthesis of nanoparticles is a powerful method to access exclusive shapes and surface properties. Previous studies employed seeds containing low-energy facets, such as a simple cubic palladium seed, in the synthesis of Pd-Au bimetallic nanoparticles; however, few studies have investigated whether DNA molecules are influential when a seed containing high-energy facets is used. Seeds enclosed by high-energy facets act as facile nucleation sites in nanoparticle growth and could suppress the effect of DNA. We report the DNA-encoded control of the morphological evolution of bimetallic Pd@Au core-shell nanoparticles from a concave palladium nanocube seed containing high-indexed facets. Based on detailed spectroscopic and microscopic studies of time-dependent growth of bimetallic nanoparticles, we found that the DNA molecules containing 10 repeating units of thymine, guanine, cytosine, or adenine (referred to as T10, G10, C10, and A10, respectively) show a unique interaction with the surface of the seed and the precursor. The most important factor is the binding affinity of the nucleobase to the Pd surface; A10 shows the highest binding affinity and can stabilize the high energy surfaces of the seed. Initially, the growth of bases with lower binding affinities (T10, G10, and C10) is completely dictated by the seed's surface energy, but later growth can be influenced by different DNA sequences, providing four Pd@Au bimetallic nanoparticles with unique morphologies. The effect of these DNA molecules with medium or low binding affinities can only be observed when more Au is deposited. We propose a scheme for DNA-controlled growth. These results provide insights into the factors governing the DNA-mediated growth of core-shell structures using seeds with high-energy sites, and the insights can be readily applied to other bimetallic systems.

The design and synthesis of bio-nano hybrid materials can not only provide new materials with novel properties, but also advance our fundamental understanding of interactions between biomolecules and their abiotic counterparts. Here, we report a new approach to achieving such a goal by growing CdS quantum dots (QDs) within single crystals of lysozyme protein. This bio-nano hybrid emitted much stronger red fluorescence than its counterpart without the crystal, and such fluorescence properties could be either enhanced or suppressed by the addition of Ag(Ⅰ) or Hg(Ⅱ), respectively. The three-dimensional incorporation of CdS QDs within the lysozyme crystals was revealed by scanning transmission electron microscopy with electron tomography. More importantly, since our approach did not disrupt the crystalline nature of the lysozyme crystals, the metal and protein interactions were able to be studied by X-ray crystallography, thus providing insight into the role of Cd(Ⅱ) in the CdS QDs formation.