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. 2014 Nov 7;346(6210):1258361.
doi: 10.1126/science.1258361. Epub 2014 Oct 9.

Casting Inorganic Structures With DNA Molds

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Free PMC article

Casting Inorganic Structures With DNA Molds

Wei Sun et al. Science. .
Free PMC article

Abstract

We report a general strategy for designing and synthesizing inorganic nanostructures with arbitrarily prescribed three-dimensional shapes. Computationally designed DNA strands self-assemble into a stiff "nanomold" that contains a user-specified three-dimensional cavity and encloses a nucleating gold "seed." Under mild conditions, this seed grows into a larger cast structure that fills and thus replicates the cavity. We synthesized a variety of nanoparticles with 3-nanometer resolution: three distinct silver cuboids with three independently tunable dimensions, silver and gold nanoparticles with diverse cross sections, and composite structures with homo- and heterogeneous components. The designer equilateral silver triangular and spherical nanoparticles exhibited plasmonic properties consistent with electromagnetism-based simulations. Our framework is generalizable to more complex geometries and diverse inorganic materials, offering a range of applications in biosensing, photonics, and nanoelectronics.

Figures

Fig. 1
Fig. 1. Casting metal NPs with prescribed shapes using DNA nanostructure molds
(A) Design schematic for casting a Ag cuboid. Cyan and green dots denote (anti-)connectors. (B) Silver (yellow color) and gold (orange color) NPs cast within DNA molds (transparent layer). Ag, silver; Au, gold; QD, quantum dot (depicted as a cyan ball).
Fig. 2
Fig. 2. Mechanical simulations of the rectangular DNA mold
(A) Ground-state solution conformation predicted for DNA mold with a 21 nm by 16 nm by 30 nm cuboid cavity. (B and C) Under point-contact loading (B) and distributed-contact loading (C), the force-deformation F-δ response in x and y directions for the DNA mold in (A). k is the simulated stiffness value along the specific direction.
Fig. 3
Fig. 3. Casting Ag cuboids with prescribed dimensions
(A) A large view TEM image for the Ag NP grown within the DNA mold with a 21 by 16 by 30 nm (or 21-16-30 nm) cuboid cavity [as shown in (B)]. (B to D) Design (top row) and TEM images (rows 2–4) of the Ag NPs grown in the DNA molds with dimensions of 21-16-30 nm (B), 21-16-20 nm (C), and 16-16-20 nm (D). In row 1 of each panel, a small purple dot represents a Au seed. Cast Ag NP is shown in yellow. In rows 2–4 of each panel, a projection model is presented to the left of the TEM images. The TEM images shows from left to right: the empty DNA box, the DNA box decorated with the Au seed (small dark dots; see figs. S47 to S49 for large-field-of-view images), the DNA box containing the fully grown Ag NP (dark rectangles with rounded corners; see figs. S52 to S54 for large-field-of-view images).
Fig. 4
Fig. 4. Casting Ag and Au NPs with prescribed cross section shapes
In (A) to (D), the top row shows the design and the bottom row shows the TEM images of the empty barrel (left), the seed-decorated barrel (middle), and the fully grown NP (right). In the top row of each panel, a small purple dot represents a Au seed. Cast Ag NP is shown in yellow and Au NP is shown in orange. (A) A Ag NP with a 25 nm equilateral triangular cross section. See figs. S32, S42, and S56 for large-field-of-view images. (B) A Ag NP with a 22 nm – 24 nm – 28 nm right-angled triangular cross section. See figs. S34, S43, and S58 for large-field-of-view images. (C) A Ag NP with a 25 nm circular shape cross section. See figs. S36, S44, and S59 for large-field-of-view images. (D) A Au NP with 19 nm by 14 nm rectangle cross section. See figs. S23, S39, and S61 for large-field-of-view images. (E) EELS measurement for a Ag NP with a 25 nm equilateral triangular cross section [black, as in (A)] and a Ag sphere with 25 nm diameter circular cross section [red, as in (C)]. (F) The simulated EELS amplitude map for the dipolar resonant modes for a Ag NP with a 25 nm equilateral triangular cross section [as in (A), left] and a Ag NP with 25 nm diameter circular cross section [as in (C), right]. Colors represent simulated amplitude. The white and black dashed lines show the contour of the NP and the DNA mold, respectively.
Fig. 5
Fig. 5. Casting composite structures
(A) A Y-shaped Ag NP junction. Top, schematics; bottom, TEM images of a Y-shaped DNA barrel trimer (left), with seed-decoration (middle), and Ag NP grown within (right). See figs. S45 and S62 for large-field-of-view images. (B) A QD-Ag-QD composite structure. Top, schematics; bottom, TEM images of a DNA barrel with seed decoration (left), with QD attached (middle), and with Ag NP grown within (right). A small purple dot represents a Au seed. Cast Ag NP is shown in yellow. The streptavidin/PEG layer of QD is a depicted as a cyan ball. See figs. S46 and S63 for large-field-of-view images.

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