Patterning of colloidal particles with chemically or topographically distinct surface domains (patches) has attracted intense research interest1–3. Surface-patterned particles act as colloidal analogues of atoms and molecules4,5, serve as model systems in studies of phase transitions in liquid systems6, behave as ‘colloidal surfactants’7 and function as templates for the synthesis of hybrid particles8. The generation of micrometre- and submicrometre-sized patchy colloids is now efficient9–11, but surface patterning of inorganic colloidal nanoparticles with dimensions of the order of tens of nanometres is uncommon. Such nanoparticles exhibit size- and shape-dependent optical, electronic and magnetic properties, and their assemblies show new collective properties12. At present, nanoparticle patterning is limited to the generation of two-patch nanoparticles13–15, and nanoparticles with surface ripples16 or a ‘raspberry’ surface morphology17. Here we demonstrate nanoparticle surface patterning, which utilizes thermodynamically driven segregation of polymer ligands from a uniform polymer brush into surface-pinned micelles following a change in solvent quality. Patch formation is reversible but can be permanently preserved using a photocrosslinking step. The methodology offers the ability to control the dimensions of patches, their spatial distribution and the number of patches per nanoparticle, in agreement with a theoretical model. The versatility of the strategy is demonstrated by patterning nanoparticles with different dimensions, shapes and compositions, tethered with various types of polymers and subjected to different external stimuli. These patchy nanocolloids have potential applications in fundamental research, the self-assembly of nanomaterials, diagnostics, sensing and colloidal stabilization.

The electrochemical reduction of CO 2 into renewable chemical products such as formic acid is an important and challenging goal. Traditional Pd catalysts suffer from CO poisoning, which leads to current density decay and short operating lifetimes. Here we explored the ability to control Pd nanoparticle surface morphology to amplify catalytic activity and increase stability in the electroreduction of CO 2 to formate. Through computational studies we have elucidated trends in intermediate binding which govern the selectivity and catalytic activity. We then rationally synthesized Pd nanoparticles having an abundance of highindex surfaces to maximize electrocatalytic performance. This catalyst displays a record current density of 22 mA/cm 2 at a low overpotential of −0.2 V with a Faradaic efficiency of 97%, outperforming all previous Pd catalysts in formate electrosynthesis. The findings presented in this work provide rational design principles which highlight morphological control of high-index surfaces for the effective and stable catalytic electroreduction of CO 2 to liquid fuels.

The organization of nanoparticles in constrained geometries is an area of fundamental and practical importance. Spherical confinement of nanocolloids leads to new modes of packing, self-assembly, phase separation and relaxation of colloidal liquids; however, it remains an unexplored area of research for colloidal liquid crystals. Here we report the organization of cholesteric liquid crystal formed by nanorods in spherical droplets. For cholesteric suspensions of cellulose nanocrystals, with progressive confinement, we observe phase separation into a micrometer-size isotropic droplet core and a cholesteric shell formed by concentric nanocrystal layers. Further confinement results in a transition to a bipolar planar cholesteric morphology. The distribution of polymer, metal, carbon or metal oxide nanoparticles in the droplets is governed by the nanoparticle size and yields cholesteric droplets exhibiting fluorescence, plasmonic properties and magnetic actuation. This work advances our understanding of how the interplay of order, confinement and topological defects affects the morphology of soft matter.

Conspectus The oxindole scaffold is a privileged structural motif that is found in a variety of bioactive targets and natural products. Moreover, derivatives of the oxindole structure are widely present in a number of biologically relevant compounds and are key intermediates in the synthesis of diverse natural products and pharmaceuticals. Therefore, novel methods to obtain oxindoles remain of high priority in synthetic organic chemistry. Over the past several decades, novel transition-metal-catalyzed methodologies have been applied toward the synthesis of a variety of heterocycles. A detailed mechanistic understanding facilitates the disruption of traditional catalytic pathways to access useful synthetic intermediates. The strategies employed have generally revolved around the generation of high-energy organometallic intermediates, which undergo cyclization reactions through domino processes. Domino cyclization methodologies are therefore attractive, as they allow facile access to functionalized oxindoles containing all-carbon quaternary centers or tetrasubstituted olefins with high chemo- and stereoselectivities. Furthermore, these developed synthetic strategies can often be easily applied in the syntheses of other related scaffolds. In this Account, we discuss the three unique strategies that our group has leveraged for the synthesis of valuable oxindole scaffolds. The first section in this Account outlines the use of an initial oxidative addition to a C­(sp2)–X bond, followed by a migratory insertion, yielding a neopentyl species amenable to a variety of subsequent functionalizations. From this reactive neopentyl metal species, we have reported C–X reductive eliminations, anionic capture cascade reactions, and intramolecular C–H functionalization processes. The second section of this Account summarizes our group’s findings on 1,2-insertions of a metal–nucleophile species across an unsaturation, generating a reactive organometallic intermediate; subsequent reactions with tethered electrophiles form the desired heterocyclic core. We have explored a wide array of transition metal-catalyzed strategies using this approach, including rhodium-catalyzed conjugate additions, an asymmetric copper-catalyzed borylcupration, and a palladium­(II)-catalyzed chloropalladation protocol. The final section of this Account details the use of dual-metal catalysis to perform a cyclization through a C–H functionalization–allylation domino reaction. Throughout this Account, we provide details of mechanistic studies that better enabled our understanding of the domino processes. Overall, our group has developed methods exploiting the unique reactivity of palladium, nickel, copper, rhodium, and ruthenium catalysts to develop methods toward a wide array of oxindole scaffolds. On the basis of the utility, diversity, and applicability of the strategies developed, we believe that they will prove to be highly useful in the syntheses of other important targets and inspire further development and mechanistic understanding of various metal-c...

Fundamental studies and practical use of metal nanoparticles (NPs) frequently depend on the ability to reproducibly synthesize large quantities of shape-specific NPs. For this reason, facile synthetic procedures are desired that will lead to large quantities of uniformly sized metal NPs exhibiting specific shapes. Here, we report a general approach to the large-scale synthesis of noble metal nanocrystals having well-defined shapes and a narrow size distribution. This method utilizes seed-mediated NP growth in aqueous suspensions of cationic surfactants and metal salts. It leads to a ∼60-fold increase in NP volumetric production capacity, compared to the most widely used solution-based synthetic methods. In addition, it uses up to 100 times less cationic surfactant than conventional solution-based methods. The applicability of the method is demonstrated in the synthesis of Pd nanocubes, rhombic dodecahedra, and polyhedrons with low index facets; branched Pd nanocrystals; alloy Pt/Pd nanocubes; Ag nanocubes. The advantages and limitations of the approach are discussed, including accessible shapes, growth kinetics, and the capability to scale up the synthetic procedure.