DNA-encoded morphological evolution of bimetallic Pd@Au core-shell nanoparticles from a high-indexed core

Abstract

DNA-mediated synthesis of nanoparticles with different morphologies has proven to be a powerful method to synthesize and access many exclusive shapes and surface properties. While previous studies employ seeds that contain relatively low-energy facets, such as a simple cubic palladium seed in the synthesis of Pd-Au bimetallic nanoparticles, few studies have investigated whether DNA molecules can still exert their influence when the synthesis uses a seed that contains high-energy facets. Seeds that are enclosed by such high-energy facets or sites are known to act as easy nucleation sites in nanoparticles growth and could potentially suppress the effect of DNA. To answer this question, we herein report DNA-encoded control of morphological evolution of bimetallic Pd@Au core-shell nanoparticles from a concave palladium nanocube seed that contains high indexed facets. Based on detailed spectroscopic and SEM studies of time-dependent growth of the bimetallic nanoparticles, we found that each of 10-mer DNA molecules (T10, G10, C10 and A10) has a unique way of interacting with both the seed’s surface and the precursor. Among them, the most important factor is the binding affinity of the nucleobase to the Pd surface, with the A10 possessing the highest binding affinity and thus capable of stabilizing the seed’s high energy surfaces. Furthermore, for bases with lower binding affinity (T10, G10 and C10) than A10, the growth is completely dictated by the seed’s surface energy initially, but the later growth can still be influenced by the different DNA sequences, resulting in four unique morphologically different Pd@Au bimetallic nanoparticles. The effect of these DNA molecules with medium binding affinity can only be observed when there is more deposition of Au. Based on the above results, a scheme for the DNA controlled growth is proposed. Together these results have provided insights into factors governing DNA-mediated growth of core-shell structures using seeds with high-energy sites, and the insights can readily be applied to other bimetallic systems that adopt seed-mediated synthesis.

Discovery of and Insights into DNA “Codes” for Tunable Morphologies of Metal Nanoparticles

“…The concave cube was different in that it had extended edges and corners in the <111> and the <110> direction while the {100} facets were retained at the center . DNA was ultimately successful in controlling the final morphology of the Pd@Au core–shell nanocrystals but the effect of the high‐energy faceted seed cannot be ignored . The presence of T10 caused the formation of a gold shell with least deposition of gold along the {100} facet and more deposition in the <111> and <110> directions.…”

“…Further investigation of a similar system consisting of a concave palladium seed instead of a cubic seed, revealed the key influence of the core in a DNA‐mediated synthesis . The existence of high‐energy sites on the seed influences the initial deposition of gold onto the seed surface in the presence of DNA with low or medium binding affinity, such as T10 and G10, C10, respectively, resulting in an overall increased growth rate.…”

“…C) The SERS spectra of 4‐MBT modified on the surfaces of different Pd@Au core–shell nanoparticles grown from a concave Pd seed with various DNA sequences. Reproduced with permission . Copyright 2018, Springer Nature.…”

“…Furthermore, the NIR absorbing Pd@Au core–shell nanoparticles were used as SERS substrates for the same substrate with enhancement factors of up to ≈10 7 when excited by higher wavelength lasers. The enhancement factors depended on the morphology of the nanoparticles tracing back to the sequence of DNA utilized in the synthesis (Figure C) …”

Functional Macromolecule‐Enabled Colloidal Synthesis: From Nanoparticle Engineering to Multifunctionality

“…In addition to using DNA as a surface‐coating ligand to build monometallic nanoparticles, bicomponent nanostructures consisting of two disparate metals can also be fabricated using DNA‐enabled synthetic methods. Lu and co‐workers prepared bimetallic Pd@Au core–shell nanoparticles using DNA‐coated Pd nanocubes as seeds and investigated the relationship between the DNA sequence and the morphology of resulting structures . The morphology of resulting the nanoparticles was also DNA sequence‐dependent, which was inherently determined by binding affinity.…”