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Control of morphology in the synthesis of Rh nanocrystals can be used to precisely tailor the electronic surface structure; this in turn directly influences their performance in catalysis applications. Many works bring attention to the development of Rh nanostructures with low-index surfaces, but limited effort has been placed on the study of high-index and surface-defect-enriched nanocrystals as they are not favored by thermodynamics due to the involvement of high-energy surfaces and increased surface-to-volume ratios. In this work, we demonstrate an aqueous synthesis of concave Rh nanotetrahedra (CTDs) serving as efficient catalysts for energy conversion reactions. CTDs are surface-defect-rich structures that form through a slow growth rate and follow the four-step model of metallic nanoparticle growth. By tuning the surfactant concentration, the morphology of Rh CTDs evolved into highly excavated nanotetrahedra (HETDs) and twinned nanoparticles (TWs). Unlike the CTD surfaces with abundant adatoms and v...

Conventional gas sensors work upon changes in mechanical or conductive properties of sensing materials during a chemical process, which may limit availabilities of size miniaturization and design simplification. However, fabrication of miniaturized sensors with superior sensitivities in real-time and label-free probing of chemical reactions or catalytic processes remains highly challenging, in particular with regard to integration of materials into a desired smaller volume without losing the recyclability of sensing properties. Here, we demonstrate a unique bimetallic nanostructure, the Au–Pd–Au core–shell–frame nanobrick, as a promising archetype for fabrication of miniaturized sensors at nanoscale. Upon analysis of the aqueous synthesis, both ex situ and in situ, the formation of Au frames is consistent with selective deposition and aggregation of NaBH4-reduced Au nanoparticles at the corners and edges of cubic Pd shells, where the {100} surfaces, capped by iodide ions, are growth-limited. By virtue of ...

Platinum was coated on the surfaces of copper nanocubes to form Cu–CuPt core–alloy–frame nanocrystals with a rhombic dodecahedral (RD) shape. Co-reduction of Pt2+ ions and residual Cu+ ions in the supernatant of the Cu nanocube solution followed by the interdiffusion of Cu and Pt atoms over the core–shell interface allowed their formation. Growth in the ⟨100⟩ directions of the {100}-terminated Cu nanocubes resulted in the {110}-faceted rhombic dodecahedra. By the introduction of additional Pt precursor, the {100} vertices of the Cu–CuPt RD nanocrystals could be selectively extended to form spiny CuPt RD nanocrystals. After removing the Cu core template, both CuPt alloy RD and spiny CuPt alloy RD nanoframes (NFs) were obtained with Pt/Cu ratios of 26/74 and 41/59, respectively. Abundant surface defects render them highly active catalysts due to the open frame structure of both sets of NFs. The spiny RD NFs showed superior specific activity toward the oxygen reduction reaction, 1.3 and 3 times to those of t...

Here we report the hydrothermal synthesis of octahedral gold nanocrystals from an aqueous solution of HAuCl4, trisodium citrate, and cetyltrimethylammonium bromide (CTAB) surfactant. By heating the mixture at 110 °C for 6, 12, 24, 48, and 72 h, gold octahedra with approximate average sizes of 30, 60, 90, 120, and 150 nm can be obtained. The percent yield of octahedral nanocrystals is more than 90% for all the samples. Products formed at shorter reaction times were also examined. Structural characterization confirmed that the octahedra are bounded by entirely {111} faces. As particle size increases, the surface plasmon resonance (SPR) absorption band red-shifts from 543 to 635 nm. These monodisperse gold octahedra can spontaneously self-assemble into long-range ordered packing structures upon water evaporation. Three types of self-assembled structures with faces, edges, or corners of the octahedra contacting the substrates have been identified. Particle size can affect the type of packing structure they ad...