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Galvanic replacement (GR) of monometallic nanoparticles (NPs) provides a versatile route to interesting bimetallic nanostructures, with examples such as nanoboxes, nanocages, nanoshells, nanorings, and heterodimers reported. The replacement of bimetallic templates by a more noble metal can generate trimetallic nanostructures with different architectures, where the specific structure has been shown to depend on the relative reduction potentials of the participating metals and lattice mismatch between the depositing and template metal phases. Now, the role of reaction stoichiometry is shown to direct the overall architecture of multimetallic nanostructures produced by GR with bimetallic templates. Specifically, the number of initial metal islands deposited on a NP template depends on the reaction stoichiometry. This outcome was established by studying the GR process between intermetallic PdCu (i-PdCu) NPs and either AuCl 2 − (Au 1+ ) or AuCl 4 − (Au 3+ ), producing i-PdCu–Au heterostructures. Significantly, multiple Au domains form in the case of GR with AuCl 2 − while only single Au domains form in the case of AuCl 4 − . These different NP architectures and their connection to reaction stoichiometry are consistent with Stranski–Krastanov (SK) growth, providing general guidelines on how the conditions of GR processes can be used to achieve multimetallic nanostructures with different defined architectures. 

Plasmonic nanoparticles (NPs) have garnered excitement over the past several decades stemming from their unique optoelectronic properties, leading to their use in various sensing applications and theranostics. Symmetry dictates the properties of many nanomaterials, and nanostructures with low, but still defined symmetries, often display markedly different properties compared to their higher symmetry counterparts. While numerous methods are available to manipulate symmetry, surface protecting groups such as polymers are finding use due to their ability to achieve regioselective modification of NP seeds, which can be removed after overgrowth as shown here. Specifically, poly(styrene- b -polyacrylic acid) (PSPAA) is used to asymmetrically passivate cubic Au seeds through competition with hexadecyltrimethylammonium bromide (CTAB) ligands. The asymmetric passivation via collapsed PSPAA causes only select vertices and faces of the Au cubes to be available for deposition of new material ( i.e. , Au, Au–Ag alloy, and Au–Pd alloy) during seeded overgrowth. At low metal precursor concentrations, deposition follows observations from unpassivated seeds but with new material growing from only the exposed seed portions. At high metal precursor concentrations, nanobowl-like structures form from interaction between the depositing phase and the passivating PSPAA. Through experiment and simulation, the optoelectronic properties of these nanobowls were probed, finding that the interiors and exteriors of the nanobowls can be functionalized selectively as revealed by surface enhanced Raman spectroscopy (SERS). 

In this work, the local structures of durable, high-activity Bi 4 TaO 8 Cl–Bi 2 GdO 4 Cl intergrowth photocatalysts that were prepared in a molten flux are determined by pair distribution function analysis of X-ray total scattering data and correlated to their photocatalytic performance. This system gives understanding to how the local structure of photocatalysts can be manipulated controllably through incorporation of rigid and flexible layers via intergrowth formation to achieve high activity. This analysis revealed that the local symmetry and distortion of the [TaO 6 ] octahedra introduced through intergrowth formation and dictated by intergrowth stoichiometry correlate with their photocatalytic activity. That is, the greater the Ta–O–Ta bond angles, the higher the photocatalytic activity of a given intergrowth for the oxygen evolution reaction. Moreover, greater tilting of the [TaO 6 ] octahedra is associated with a larger band gap. This analysis was coupled with a structure mining approach to model the intergrowth structure by building supercells for refinement of the X-ray diffraction data. This analysis found that Ta- and Gd-domains are separated within the intergrowths, with large Gd-domains separated by small Ta-domains at high Gd% and the opposite for high Ta%. Taken together with Williamson–Hall analysis, our results highlight that the local structure of layered materials can be modulated through strain engineering enabled by the selection of rigid and flexible intergrowth layers, providing a new design pathway to high performance photocatalysts. 

Chiral plasmonic nanocrystals with varied symmetries were synthesized by l -glutathione-guided overgrowth from Au tetrahedra, nanoplates, and octahedra, highlighting the importance of chiral molecule adsorption at transient kink sites. Large g -factors are possible and depend on symmetry. Simulations of their chiroptical properties from tomographically obtained nanocrystal models further verify their chirality. 

The crystal structures of three β-halolactic acids have been determined, namely, β-chlorolactic acid (systematic name: 3-chloro-2-hydroxypropanoic acid, C 3 H 5 ClO 3 ) (I), β-bromolactic acid (systematic name: 3-bromo-2-hydroxypropanoic acid, C 3 H 5 BrO 3 ) (II), and β-iodolactic acid (systematic name: 2-hydroxy-3-iodopropanoic acid, C 3 H 5 IO 3 ) (III). The number of molecules in the asymmetric unit of each crystal structure ( Z ′) was found to be two for I and II, and one for III, making I and II isostructural and III unique. The difference between the molecules in the asymmetric units of I and II is due to the direction of the hydrogen bond of the alcohol group to a neighboring molecule. Molecular packing shows that each structure has alternating layers of intermolecular hydrogen bonding and halogen–halogen interactions. Hirshfeld surfaces and two-dimensional fingerprint plots were analyzed to further explore the intermolecular interactions of these structures. In I and II, energy minimization is achieved by lowering of the symmetry to adopt two independent molecular conformations in the asymmetric unit.