Spontaneous Superlattice Formation in Nanorods Through Partial Cation Exchange

Abstract

Lattice mismatch strains are widely known to control nanoscale pattern formation in heteroepitaxy, but such effects have not been exploited in colloidal nanocrystal growth.We demonstrate a colloidal route to synthesizing CdS-Ag 2 S nanorod superlattices through partial cation exchange. Strain induces the spontaneous formation of periodic structures. Ab initio calculations of the interfacial energy and modeling of strain energies show that these forces drive the self-organization. The nanorod superlattices exhibit high stability against ripening and phase mixing. These materials are tunable near-infrared emitters with potential applications as nanometer-scale optoelectronic devices.

Formation Mechanism and Properties of CdS-Ag2S Nanorod Superlattices

“…The colloidal CdS nanorods are added to a solution of toluene, AgNO 3 , and methanol at -66 • C in air. 15 During the cation exchange reaction, the Ag + cations substitute for Cd 2+ cations within the nanorods, due to the preferential binding of MeOH to the divalent Cd 2 + ion than to Ag + (here Me stands for a methyl group). 19 This solid-state exchange reaction has been shown to take place on a millisecond timescale 19,20 on the nanoscale due to the small size of the nanocrystals and the high mobilities of Ag + and Cd 2+ within the crystalline lattices.…”

“…15 An image of the nanostructures modeled here is shown in Fig. 1(a), where segments of Ag 2 S have spontaneously formed within CdS nanorods in a periodic arrangement.…”

“…15 During cation exchange, dissolved Ag ions displace Cd cations from CdS nanorods also present in solution, resulting in islands of Ag 2 S in the CdS nanorods.…”

Design Principle of Telluride-Based Nanowire Heterostructures for Potential Thermoelectric Applications

“…Statistic result from Figure 4E gives an average of 4.186 ± 1.314 Bi 2 Te 3 plates per nanowire. Notably, analysis of the structure parameters of the "barbell" heterostructures prepared using the conditions described in Figure 3D, especially the positions of the Bi 2 Te 3 plates (the black dots in Figure 4E) in the nanowire heterostructures, indicates that the positions of isolated Bi 2 Te 3 plates on the nanowire body is totally random, which is significantly different from other mechanisms such as lattice strain-induced heterostructure formation 28 and further confirms the different growth mechanisms for the Bi 2 Te 3 plates on Te nanowire tips and bodies. Figure 4 shows the size distributions in the diameter ( Figure 4A, Te nanowire body) and the length ( Figure 4B, overall length) of the Te−Bi 2 Te 3 "barbell" nanowire heterostructures as well as in the length ( Figure 4C) and the thickness ( Figure 4D) of the Bi 2 Te 3 plates.…”

Seeded Growth of Highly Luminescent CdSe/CdS Nanoheterostructures with Rod and Tetrapod Morphologies

“…The PL QE of both w-CdSe and zb-CdSe nanocrystals strongly depends on passivation of the nanocrystal surface with organic ligands, varying between ~3 % and ~30% depending on sample history, e.g., the number of precipitation-redissolution steps applied to purify the nanocrystals from crude solution. We injected w-CdSe and zb-CdSe nanocrystals into the reaction mixture containing TOPO, TOP, n-octadecylphosphonic acid (ODPA), n-propylphosphonic acid (PPA), a Cd-ODPA complex and trioctylphosphine sulfide (TOPS) in concentrations optimized for synthesis of high-quality wurtzite-phase CdS (further referred to as "w-CdS") nanorods with long (001) axes ( Figure S1) [24].…”