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The M1 form of vanadium dioxide, which exhibits a reversible insulator-metal transition above room temperature, has been incorporated into nanoscale heterostructures through solution-phase epitaxial growth on the tips of rutile TiO2 nanorods. Four distinct classes of VO2-TiO2-VO2 nanorod heterostructures are accessible by modulating the growth conditions. Each type of VO2-TiO2-VO2 nanostructure has a different insulator-metal transition temperature that depends on the VO2 domain sizes and the TiO2-VO2 interfacial strain characteristics. [ABSTRACT FROM AUTHOR]

The M1 form of vanadium dioxide, which exhibits a reversible insulator-metal transition above room temperature, has been incorporated into nanoscale heterostructures through solution-phase epitaxial growth on the tips of rutile TiO2 nanorods. Four distinct classes of VO2-TiO2-VO2 nanorod heterostructures are accessible by modulating the growth conditions. Each type of VO2-TiO2-VO2 nanostructure has a different insulator-metal transition temperature that depends on the VO2 domain sizes and the TiO2-VO2 interfacial strain characteristics. [ABSTRACT FROM AUTHOR]

Conspectus Colloidal hybrid nanoparticles are solution-dispersible constructs that join together multiple distinct nanoscale materials through direct solid-solid interfaces. Given their multifunctionality and synergistic properties that emerge from interfacial coupling, hybrid nanoparticles are of interest for applications in biomedical imaging, solar energy conversion, heterogeneous catalysis, nanophotonics, and beyond. High-order hybrid nanoparticles, which incorporate three or more nanocrystal domains, offer greater tunability and functional diversity relative to one or two-component nanoparticles. The multiple heterojunctions within these structures can facilitate complex electromagnetic coupling as well as cooperative surface processes. Additionally, these materials can be used as model systems for studying fundamental structure-property relationships at the nanoscale that arise from particle coupling and interfacial exchanges. Limiting these advances is the inability to synthesize hybrid nanoparticles with precise morphologies and geometries. High-order hybrid nanoparticles can adopt more than one configuration, and each unique arrangement will have different heterointerfaces and, accordingly, different functions. Seeded-growth methods are among the most effective methods for producing high-quality hybrid nanoparticles. Engineering complex heterostructures using these stepwise reactions is in some ways conceptually analogous to the total synthesis of large organic molecules. However, unlike in molecular synthesis, the rules and guidelines that underpin the formation of hybrid nanoparticles are less understood. For example, when a third domain is added to a two-component heterodimer nanoparticle seed, several distinct types of hybrid nanoparticle products are possible, but only one is typically observed due to preferred growth at specific locations. The three-component heterotrimer products that preferentially form are not necessarily those that have the domain configurations and heterojunctions required to facilitate a targeted application. Different arrangements of the three nanoparticles that comprise a heterotrimer lead to distinct configurational isomers. Accordingly, understanding and controlling configurational isomerism in nanoparticle heterotrimers is foundational for engineering high-order hybrid nanostructures with targeted heterointerfaces, properties, and functionalities. This Account highlights recent insights into the pathways by which three-component nanoparticle heterotrimers form and how their configurations can be controlled and modified. In-depth microscopic investigations into the formation of heterotrimers by growing a third nanoparticle domain on a two-component heterodimer seed have revealed that in some cases indiscriminate nucleation first occurs on all exposed surfaces followed by surface-mediated migration and coalescence to the preferred interface. This insight helps to rationalize observed site-specific, chemoselective growth phenomena. Additionally, new approaches for directing growth in heterotrimer synthesis, such as protection-deprotection schemes inspired by organic chemistry, are becoming effective tools for constructing hybrid nanoparticles having nonpreferred domain configurations. Alternatives to traditional seeded-growth approaches are also emerging, including insertion reactions driven by saturation-precipitation processes and orthogonal transformations of preformed hybrid constructs using ion exchange. These and other recent advances are providing a powerful suite of synthetic tools that are anticipated to enable function-driven design of high-order hybrid nanoparticles having targeted properties and applications. [ABSTRACT FROM AUTHOR]

The ability to selectively form one crystal structure among several options in a polymorphic system is an important goal in solid-state synthesis. Nanocrystal cation exchange, which proceeds rapidly under mild conditions, can retain key structural features and yield otherwise inaccessible phases, but the extent to which crystal structure can be retained and therefore selectively targeted during such reactions has been limited. Here, we show that nanocrystals of digenite Cu2−xS transform to zincblende MnS and CoS upon cation exchange. Zincblende MnS and CoS, which are metastable in bulk, retain both the tetrahedral cation coordination and cubic close packed anion sublattice of digenite Cu2−xS. Comparison with wurtzite MnS and CoS, which have been accessed previously through analogous cation exchange of roxbyite Cu2−xS, demonstrates the selective formation of the related zincblende vs. wurtzite polymorphs by cation exchange of structurally distinct templates. [ABSTRACT FROM AUTHOR]

The ability to selectively form one crystal structure among several options in a polymorphic system is an important goal in solid-state synthesis. Nanocrystal cation exchange, which proceeds rapidly under mild conditions, can retain key structural features and yield otherwise inaccessible phases, but the extent to which crystal structure can be retained and therefore selectively targeted during such reactions has been limited. Here, we show that nanocrystals of digenite Cu2−xS transform to zincblende MnS and CoS upon cation exchange. Zincblende MnS and CoS, which are metastable in bulk, retain both the tetrahedral cation coordination and cubic close packed anion sublattice of digenite Cu2−xS. Comparison with wurtzite MnS and CoS, which have been accessed previously through analogous cation exchange of roxbyite Cu2−xS, demonstrates the selective formation of the related zincblende vs. wurtzite polymorphs by cation exchange of structurally distinct templates. [ABSTRACT FROM AUTHOR]

Nanoscale heterostructures that interface with multiple distinct materials provide opportunities to engineer functional complexity into single-particle constructs. However, existing synthetic pathways to such hybrid nanoparticles emphasize surface-seeded growth, which limits the scope of accessible systems. Here, we introduce an alternative approach that transforms isotropic nanocrystals into asymmetric, multicomponent Janus particles through sequential deposition, reactive phase segregation, and cation exchange processes that are mediated by an unusual class of reactive synthons. After Ag-Au seed particles had formed and had reacted with sulfur, a series of segregated Au1-xAgx-AgAuS and Au1-xAgx-Ag3AuS2 hybrid nanoparticles form. The AgAuS and Ag3AuS2 domains provide a synthetic entryway into solution-mediated cation exchange reactions, with the compositions of the Ag-Au-S synthons defining the components, morphologies, and interfaces of the hybrid nanoparticle products. Upon cation exchange with Pb2+, Au1-xAgx-AgAuS forms Ag1-xAux-PbS heterodimers while Au1-xAgx-Ag3AuS2 forms Ag1-xAux-Ag2S-PbS heterotrimers. The process by which isotropic metal nanoparticles transform into asymmetric hybrid nanoparticles through reactive Ag-Au-S synthons provides important insights that will be applicable to the retrosynthetic design of complex nanoscale heterostructures having expanded multifunctionality and synergistic properties. [ABSTRACT FROM AUTHOR]

Nanosheet heterostructures that directly interface multiple distinct metal chalcogenides are important two-dimensional materials with unique synergistic properties. Solution routes to these materials offer potential advantages over existing vapor deposition and exfoliation/restacking methods, but they remain difficult to implement and control. Here, we show that SnSe can be grown in solution on micrometer-sized GeSe nanosheets and establish guidelines for achieving controllable deposition. Heating GeSe nanosheets in oleylamine with various amounts of SnCl2 and TOP-Se reveals distinct regimes that favor growth of SnSe on the edge sites vs basal planes of GeSe. Using continuous injection to better control concentrations and reagent delivery, SnSe can be grown on GeSe to produce two distinct types of crystallographically aligned SnSe@GeSe nanosheet heterostructures. [ABSTRACT FROM AUTHOR]

Hybrid nanoparticles composed ofmultiple material systems providea platform for studying the coupling between nanoparticles with distinctproperties. Here, we describe a nontraditional synthetic pathway toAu-In2O3hybrid nanoparticles that contain twodistinct plasmonic domains: Au, with a localized surface plasmon resonance(LSPR) in the visible, and In2O3, with a LSPRin the mid-infrared. The hybrid nanocrystals are produced by slowlyintroduce In(III) stock solution to Au nanoparticle seeds using asyringe pump. Rather than forming through a traditional heterogeneousseeded-growth process, a series of in situand ex situstudies reveal an alternate multistep pathway. TheAu nanoparticles first combine with In to form an alloy of Au andIn, which is colloidally stable up to 300 °C in 1-octadecene.The Au-In alloy nanoparticles then transform into intermetallic AuIn2nanoparticles that are surrounded by a shell of amorphousindium oxide (AuIn2@InOx),followed by the final Au-In2O3heterodimersupon complete phase segregation. [ABSTRACT FROM AUTHOR]

Reacting MoAlB with ZnCl2 at 550 °C produces metastable Mo2AlB2 through a one-step topochemical transformation. This reaction showcases differences in reactivity between boride-based MAB phases and carbide-based MAX phases, which are solid-state precursors to an important family of 2-D materials. [ABSTRACT FROM AUTHOR]

Die rege Nachfrage nach komplexen Nanomaterialien mit präzise kontrollierten Architekturen und Grenzflächen hat zu einer enormen Entwicklung bei innovativen Syntheseverfahren geführt. Dieser Aufsatz beleuchtet Schlüsselstrategien für die chemische Umwandlung und schrittweise Synthese von anorganischen Mehrkomponenten ‐ Nanostrukturen, wobei existierende Umwandlungsreaktionen im Nanobereich in Klassen eingeordnet werden, die den bei der Synthese von organischen Molekülen verwendeten entsprechen. Ein Schwerpunkt liegt auf der Übertragung von Konzepten aus der Molekülsynthese auf nanoskalige Systeme: Dazu gehören unter anderem Ortsselektivität, Regio ‐ und Chemoselektivität, orthogonale Reaktivität, Kupplungsreaktionen, Strategien zum Schützen und Entschützen sowie Verfahren zur Trennung und Aufreinigung. Das so geschaffene Regelwerk stellt ein neues Modell für die “Totalsynthese” von komplexen anorganischen Nanostrukturen dar, dem die Prinzipien von mehrstufigen Totalsynthesen komplexer organischer Molekülverbindungen und Naturstoffe zugrundeliegen. Nanoskalige Totalsynthese: Ganz analog zur Totalsynthese von großen und komplexen molekularen Zielverbindungen lassen sich vielfältige Nanopartikel ‐ Reaktionsbibliotheken in „Totalsynthesen“ zum gezielten Aufbau komplexer nanoskaliger Mehrkomponenten ‐ Architekturen nutzen. [ABSTRACT FROM AUTHOR]

New synthetic innovations are rapidly being developed to address the demand for complex, next-generation nanomaterials with rigorously controlled architectures and interfaces. This Review highlights key strategies for the chemical transformation and stepwise synthesis of multicomponent inorganic nanostructures, with the existing nanoscale transformations categorized into classes of reactions that are related to those used in the synthesis of organic molecules. The application of concepts used in molecular synthesis-including site-selectivity, regio- and chemoselectivity, orthogonal reactivity, coupling reactions, protection/deprotection strategies, and procedures for separation and purification-to nanoscale systems is emphasized. Collectively, the resulting synthetic concept represents an emerging model for the synthesis of complex inorganic nanostructures on the basis of the guiding principles that underpin the multistep total synthesis of complex organic molecules and natural products. [ABSTRACT FROM AUTHOR]

Controlling the composition and phase formation of bulk and nanoscale solids underpins efforts to control physical properties. Here, we introduce a powerful new chemical pathway that facilitates composition-tunable synthesis, post-synthesis purification, and precise phase targeting in metal chalcogenide systems. `When metal sele-nides and sulfides react with trioctylphosphine (TOP) at temperatures that range from 65 to 270 °C, selenium and sulfur are selectively extracted to produce the most metal-rich chalcogenide that is stable in a particular binary system. This general approach is demonstrated for SnSe2, FeS2, NiSe2, and CoSe2, which convert to SnSe, FeS, Ni3Se2, and Co9Se8, respectively. In-depth studies of the Fe-Se system highlight the precise phase targeting and purification that is achievable, with PbO-type FeSe (the most metal-rich stable Fe-Se phase) forming exclusively when other Fe-Se phases, including mixtures, react with TOP. This chemistry also represents a new template-based nanoparticle "conversion chemistry" reaction, transforming hollow NiSe2 nano-spheres into hollow NiSe nanospheres with morphological retention. [ABSTRACT FROM AUTHOR]

Abstract: A solution precursor route has been used to synthesize a series of nanocrystalline rare-earth borates. Amorphous precursor powders are precipitated during an aqueous reaction between RE 3+ and NaBH4, and the isolated powders can be annealed in air at 700°C to form YBO3, NdBO3, SmBO3, EuBO3, GdBO3, and HoBO3. YBO3:Eu formed using this strategy shows red-orange emission properties that are similar to high-quality nanocrystals prepared by other methods. The materials have been characterized by FTIR spectroscopy, powder XRD, SEM, DSC, UV–Vis fluorimetry, and TEM with EDS and element mapping. [Copyright &y& Elsevier]

A variety of binary intermetallic compounds of late transition metals with low-melting post-transition metals have been synthesized in bulk quantities by reacting molten metal dispersions with fine metal powders in hot polyalcohol solvents. Fourteen distinct intermetallics were formed using this technique: SbSn, FeSn2, Cu6Sn5, CoSn3, Ni3Sn4, FeGa3, NiGa4, Cu9Ga4, CoGa3, Ni2In3, InSb, In5Bi3, InBi, and Bi3Ni. Notable among these are a low-temperature phase (α-CoSn3), textured intermetallic powders with anisotropic morphologies (α-CoSn3 and FeSn2), and superconductors (Bi3Ni and In5Bi3). Reaction pathway studies suggest that the molten low-melting metals diffuse into the larger higher melting powders, forming intermetallic compounds directly in a liquid-phase medium from bulk-scale powders of the constituent elements. Bulk-scale quantities of polycrystalline intermetallic compounds are obtained by reacting molten metal dispersions with fine metal powders in hot polyalchohol solvents. This low-temperature synthetic approach is general, yielding the following intermetallics: SbSn, FeSn2, Cu6Sn5, CoSn3, Ni3Sn4, FeGa3, NiGa4, Cu9Ga4, CoGa3, Ni2In3, InSb, In5Bi3, InBi, and Bi3Ni. [ABSTRACT FROM AUTHOR]

When reacted with trioctylphosphine at ~360 °C, rhodium nanocrystals convert to rhodium phosphide (Rh2P) nanocrystals. Careful control over synthetic variables, such as temperature, stabilizing ligands, and cosolvents, can result in Rh2P nanocrystals with shapes that reflect the Rh nanocrystal templates. Accordingly, Rh nanocrystals with multipod, cube- and triangle-derived shapes convert to Rh2P nanocrystals that maintain the shape of their Rh precursors. Both dense and hollow Rh2P nanocrystals can be generated using a single unified chemical conversion strategy. These empirical guidelines for generating a morphologically diverse library of Rh2P nanocrystals provide important insights into shape conservation using nanocrystal templates and will likely be portable to other multielement systems for which rigorous shape-controlled synthesis remains challenging. [ABSTRACT FROM AUTHOR]

The ability to control the shape of metal nanocrystals is critical to applications such as catalysis, magnetism, and plasmonics. Despite significant advances in controlling the shapes of single-metal nanocrystals, rigorous shape control of multimetal nanocrystals remains challenging, and has been limited largely to alloy systems of similar metals. Here we describe a robust strategy that produces shape-controlled intermetallic nanocrystals involving elements of notably different reduction potentials, reduction kinetics, and reactivity. The approach utilizes shape- and size-controlled β-Sn nanocrystals as reactive templates that can be converted into binary M-Sn (M = Fe, Co, Ni, Pd) intermetallic compounds by reaction with appropriate metal salt solutions under reducing conditions. The result, demonstrated in detail for the FeSn2 system, is a variety of nanostructures with morphologies that include spheres, cubes, hollow squares, U-shaped structures, nanorods, and nanorod dimers. Our experiments demonstrate a size- and shape-dependent reactivity toward the formation of hollow FeSn2 nanostructures and provide empirical guidelines for the formation of other intermetallic nanocrystals. In addition to those of FeSn2, nanocrystals of intermetallic PdSn, CoSn3, and NiSn3 can be formed using this same chemical conversion strategy. [ABSTRACT FROM AUTHOR]

Understanding how solids form is a challenging task, and few strategies allow for the elucidation of reaction pathways that are useful for designing new solids. Here, we describe an unusual multistep reaction pathway that leads to the formation of AuCuSn2, a new ternary intermetallic compound that was discovered as nanocrystals using a low-temperature solution route. The formation of AuCuSn2 using a modified polyol process occurs through a multistep pathway that was elucidated by taking aliquots throughout the course of the reaction and studying the products using a variety of techniques. The reaction proceeds through four distinct steps: (a) formation of Au nanoparticles at or near room temperature, mediated by a galvanic reaction between Au3+ and Sn2+ (forming Au0 and Sn4+, precipitated as SnO2 that forms a shell around the nanoparticles), (b) formation of NiAs-type AuSn nanoparticles, along with Cu and Sn, upon addition of NaBH4, (c) aggregation and thermal interdiffusion to form AuCuxSny alloy nanoparticles, and (d) nucleation of intermetallic AuCuSn2, which has an ordered NiAs-derived structure. The proposed mechanism was tested by starting the reaction with the AuSn intermediate. AuSn nanoparticles were synthesized separately and reacted with Cu and Sn nanoparticles, and ordered AuCuSn2 formed as expected. Elucidation of this reaction pathway has important implications for guiding the design of new intermetallic solids, as well as for controlling the synthesis of complex multimetal nanocrystals. [ABSTRACT FROM AUTHOR]

Intermetallic compounds and alloys are traditionally synthesized by heating mixtures of metal powders to high temperatures for long periods of time. A low-temperature solution-based alternative has been developed, and this strategy exploits the enhanced reactivity of nanoparticles and the nanometer diffusion distances afforded by binary nanocomposite precursors. Prereduced metal nanoparticles are combined in known ratios, and they form nanomodulated composites that rapidly transform into intermetallics and alloys upon heating at low temperatures. The approach is general in terms of accessible compositions, structures, and morphologies. Multiple compounds in the same binary system can be readily accessed; e.g., AuCu, AuCu3, Au3Cu, and the AuCu-II superlattice are all accessible in the Au-Cu system. This concept can be extended to other binary systems, including the intermetallics FePt3, CoPt, CuPt, and Cu3-Pt and the alloys Ag-Pt, Au-Pd, and Ni-Pt. The ternary intermetallic Ag2Pd3S can also be rapidly synthesized at low temperatures from a nanocomposite precursor comprised of Ag2S and Pd nanoparticles. Using this low-temperature solution-based approach, a variety of morphologically diverse nanomaterials are accessible: surface-confined thin films (planar and nonplanar supports), free-standing monoliths, nanomesh materials, inverse opals, and dense gram-scale nanocrystalline powders of intermetallic AuCu. Importantly, the multimetallic materials synthesized using this approach are functional, yielding a room- temperature Fe-Pt ferromagnet, a superconducting sample of Ag2Pd3S (Tc = 1.10 K), and a AuPd4 alloy that selectively catalyzes the formation of H2O2 from H2 and O2. Such flexibility in the synthesis and processing of functional intermetallic and alloy materials is unprecedented. [ABSTRACT FROM AUTHOR]

The new layered transition metal oxides NaRbLnMO5 (Ln = Nd, Sm, Eu, Gd; M = Nb, Ta) were synthesized by direct solid-state reaction. NaRbLaNbO5 crystallizes with a tetragonal unit cell [a=5.839(6) Å, c=8.313(1) Å] analogous to that of the related compound NaKLaNbO5, while NaRbLaTaO5 indexes to a larger monoclinic unit cell [a=9.577(2) Å, b=5.834(1) Å, c=8.323(2) Å, β=93.00(2)]. NaRbLnNbO5 can be prepared for Ln = Nd, Sm, Eu, Gd, and NaRbLnTaO5 can be prepared for Ln = Nd, Sm. Both series of compounds show the expected decrease in unit cell volume as the size of the lanthanide decreases. NaRbLaNbO5 is also amenable to ion exchange, forming Li2-xRbxLaNbO5 upon reaction with molten lithium nitrate. [Copyright &y& Elsevier]

A new multistep approach was developed to synthesize atomically ordered intermetallic nanocrystals, using AuCu and AuCu3 as model systems. Bimetallic nanoparticle aggregates are used as precursors to atomically ordered nanocrystals, both to precisely define the stoichiometry of the final product and to ensure that atomic-scale diffusion distances lower the reaction temperatures to prevent sintering. In a typical synthesis, PVP-stabilized Au-Cu nanoparticle aggregates synthesized by borohydride reduction are collected by centrifugation and annealed in powder form. At temperatures below 175 °C, diffusion of Cu into Au occurs, and the atomically disordered solid solution CuxAu1-x exists. For AuCu3, nucleation occurs by 200 °C, and atomically ordered AuCu exists between 200 and 400 °C. For AuCu3, an AuCu intermediate nucleates at 200 °C, and further diffusion of Cu into the AuCu intermediate at 300 °C nucleates AuCu3. Atomically ordered AuCu and AuCu3 nanocrystals can be redispersed as discrete colloids in solution after annealing between 200 and 300 °C. [ABSTRACT FROM AUTHOR]

Demonstrates a topochemical route to nondefect, three-dimensional perovskites from lamellar Dion-Jacobson and Ruddlesden-Popper precursors. Reduction of one of the ions in the precursor phase and concomitant loss of oxygen; Retention of anisotropic texture of the layered precursors in the product perovskite phase.

Transition-metal silicides are part of an important family of intermetallic compounds, but the high-temperature reactions that are generally required to synthesize them preclude the formation of colloidal nanoparticles. Here, we show that palladium, copper, and nickel nanoparticles react with monophenylsilane in trioctylamine and squalane at 375 °C to form colloidal Pd2Si, Cu3Si, and Ni2Si nanoparticles, respectively. These metal silicide nanoparticles were screened as electrocatalysts for the hydrogen evolution reaction, and Pd2Si and Ni2Si were identified as active catalysts that require overpotentials of -192 and -243 mV, respectively, to produce cathodic current densities of -10 mA cm-2. [ABSTRACT FROM AUTHOR]

We report predictive guidelines for the substoichiometric cation exchange of model two-component metal sulfide nanorods containing divalent cations of similar hardness. Unit cell volume changes, cation radii, solubility constants, and solid state interfaces influence selectivity during substoichiometric exchange of Cu+ when multiple products are possible. [ABSTRACT FROM AUTHOR]

Palladium is converted into palladium hydride, β-PdHx, in polyol solution using NaBH4 as a hydrogen source; nanocrystalline Pd reacts to form PdHx faster and at lower temperatures than bulk Pd, and can be made to release hydrogen to regenerate Pd. [ABSTRACT FROM AUTHOR]

Palladium is converted into palladium hydride, β-PdHx, in polyol solution using NaBH4as a hydrogen source; nanocrystalline Pd reacts to form PdHxfaster and at lower temperatures than bulk Pd, and can be made to release hydrogen to regenerate Pd. [ABSTRACT FROM AUTHOR]

The article focuses on self-assembled colloidal crystals. It discusses visualizing atomic crystal chemistry using microscopic analogues of inorganic solids. It states that colloidal crystallization can be achieved either through convective self-assembly, which takes hours to days, or by simple drop coating, which takes minutes. Microscopy methods are the best way to visualize the periodic arrangement of the monodisperse spheres in colloidal crystals. Scanning electron microscopy, where available, is particularly useful for obtaining high-resolution images of the individual submicron spheres, as well as the colloidal crystal lattice.

Integrating multiple materials in arbitrary arrangements within nanoparticles is a prerequisite for advancing many applications. Strategies to synthesize heterostructured nanoparticles are emerging, but they are limited in complexity, scope, and scalability. We introduce two design guidelines, based on interfacial reactivity and crystal structure relations, that enable the rational synthesis of a heterostructured nanorod megalibrary. We define synthetically feasible pathways to 65,520 distinct multicomponent metal sulfide nanorods having as many as 6 materials, 8 segments, and 11 internal interfaces by applying up to seven sequential cation-exchange reactions to copper sulfide nanorod precursors. We experimentally observe 113 individual heterostructured nanorods and demonstrate the scalable production of three samples. Previously unimaginable complexity in heterostructured nanorods is now routinely achievable with simple benchtop chemistry and standard laboratory glassware. [ABSTRACT FROM AUTHOR]

Nanoscale transition metal tellurides are important materials for a variety of applications. However, solution‐phase methods to synthesize nanoscale transition metal tellurides are not as well‐developed as for related sulfide and selenide systems. Here, we show that pre‐formed colloidal metal nanoparticles react with bis(trimethylsilyl)telluride to form their corresponding tellurides. Nanoparticles of Pd, Pt, and Ni convert to nanoscale particles of the layered transition metal dichalcogenides PdTe2, PtTe2, and NiTe2 upon reaction with bis(trimethylsilyl)telluride. When Pd nanoparticles instead react with a TOP‐Te complex (TOP = trioctylphosphine), PdTe forms. This result demonstrates that the metal telluride phase that forms can be controlled by the reactivity of the tellurium reagent. Other nanoparticles, including Co, Ag, and Rh, also form crystalline metal tellurides upon reaction with bis(trimethylsilyl)telluride, which indicates that this approach to synthesizing nanoscale transition metal tellurides is general. [ABSTRACT FROM AUTHOR]

The article reports on the ZnO-templated Synthesis of Wurtzite-Type ZnS and ZnSe nanoparticles. It states that significant attention was given to wide bandgap semiconductor nanocrystals because of their size-dependent properties and diverse applications. The article shows that ZnO nanoparticles, which adopt the WZ structure, can serve as structural templates for the controllable formation of WZ-type ZnS and ZnSe.

The article offers information about a study conducted to explore the implications of the discovery that nanocrystalline intermetallics undergo facile solution-mediated reaction to form derivative phases. The discovery provides a robust toolkit for systematically modifying the compositions and structures of multi-metal nanocrystals. Along with the discovery is the uncovering of the conversion strategy which produces important compounds that are difficult to make by other methods.

The precise placement of different materials in specific regions of a nanocrystal is important for many applications, but this remains difficult to achieve synthetically. Here we show that regioselectivity during partial cation exchange reactions of metal chalcogenide nano-crystals emerges from crystallographic relationships between the precursor and product phases. By maximizing the formation of low-strain interfaces, it is possible to rationally integrate three distinct materials within uniform spherical and rod-shaped colloidal nanoparticles to produce complex asymmetric heterostructured isomers. Through sequential partial exchange of Cu+ in Cu1.8S nanocrystals with Zn2+ and Cd2+, five distinct ZnS/CdS/ Cu1.8S nanosphere and nanorod isomers are accessible. [ABSTRACT FROM AUTHOR]

Complex heterostructured nanoparticles with precisely defined materials and interfaces are important for many applications. However, rationally incorporating such features into nanoparticles with rigorous morphology control remains a synthetic bottleneck. We define a modular divergent synthesis strategy that progressively transforms simple nanoparticle synthons into increasingly sophisticated products. We introduce a series of tunable interfaces into zero-, one-, and two-dimensional copper sulfide nanoparticles using cation exchange reactions. Subsequent manipulation of these intraparticle frameworks yielded a library of 47 distinct heterostructured metal sulfide derivatives, including particles that contain asymmetric, patchy, porous, and sculpted nanoarchitectures. This generalizable mix-and-match strategy provides predictable retrosynthetic pathways to complex nanoparticle features that are otherwise inaccessible. [ABSTRACT FROM AUTHOR]

Review: 197 refs. [ABSTRACT FROM AUTHOR]

Review: 91 refs. [ABSTRACT FROM AUTHOR]

Interfaces between nanoscale solids can facilitate coupling between dissimilar materials, leading to emergent and synergistic properties as well as mix-and-match multifunctionality. Seeded-growth methods, whereby one material is grown directly off of the surface of another, can lead to the formation of hybrid nanoparticles containing such solid-state heterojunctions. Successfully applying seeded-growth methods to the synthesis of hybrid nanoparticles, however, requires a precise balance of competing reaction variables, which limits the scope of materials that can be routinely incorporated into them and, accordingly, the types of achievable interfaces. Here, we describe an alternate pathway that overcomes key limitations of seeded-growth methods by synthetically deconvoluting the formation of particle-particle interfaces and the incorporation of desired materials components. Readily accessible hybrid nanoparticles can be rationally modified using sequential anion and cation exchange reactions which transform them into derivative products that contain different constituent materials but retain the preprogrammed morphologies and interfaces. Using Pt-MnO heterodimers as a synthetic entryway, we demonstrate the synthesis of seven different derivative Pt-MaXy (M = metal, X = chalcogen) heterodimers through integrated ion exchange pathways. We also demonstrate that tunable domain sizes are retained during complete multistep material transformations and that partial exchanges can be used to introduce morphologically sophisticated features into hybrid nanoparticles, including core@shell components. The sequential ion exchange reactions can also be applied to different domains of three-component hybrid nanoparticles, demonstrated for the transformation of Fe3O4-Pt-MnO into FeSx-Pt-Cu2S. Finally, the hybrid nanoparticle ion exchange reactions proceed with retention of anion sublattice structure across the particle-particle interfaces, demonstrating that crystallographic orientation and domain alignment are preserved. Collectively, these results demonstrate the wide-ranging applicability of sequential ion exchange reactions to controllably access a diverse library of colloidal hybrid nanoparticles across a wide range of materials, morphologies, and interfaces. [ABSTRACT FROM AUTHOR]

Data‐intensive discovery of water‐splitting catalysts can accelerate the development of sustainable energy technologies, such as the photocatalytic and/or electrocatalytic production of renewable hydrogen fuel. Through computational screening, 13 materials were recently predicted as potential water‐splitting photocatalysts: Cu3NbS4, CuYS2, SrCu2O2, CuGaO2, Na3BiO4, Sr2PbO4, LaCuOS, LaCuOSe, Na2TeO4, La4O4Se3, Cu2WS4, BaCu2O2, and CuAlO2. Herein, these materials are synthesized, their bandgaps and band alignments are experimentally determined, and their photoelectrocatalytic hydrogen evolution properties are assessed. Using cyclic voltammetry and chopped illumination experiments, 9 of the 13 materials are experimentally found to have bandgaps and band alignments that straddle the potentials required for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), as computationally predicted. During photocatalytic testing, 12 of the materials yield a measurable photocurrent. However, only three are found to be active for the HER, with Cu3NbS4, CuYS2, and Cu2WS4 producing H2 in amounts comparable to bare TiO2; a benchmark photocatalyst. This study provides experimental validation of computational bandgap and band alignment predictions while also successfully identifying active photocatalysts. [ABSTRACT FROM AUTHOR]

The ability to selectively synthesize one particular polymorph in a solid-state system having multiple crystal structures with the same composition is important for accessing desired properties. Solutionmediated reactions, including anion and cation exchange, that chemically transform colloidal nanoparticles with preprogrammed structural features into targeted products have emerged as a powerful platform for predictably accessing metastable polymorphs. While nanocrystal ionexchange reactions that retain anion sublattice features are well known, analogous reactions that preserve cation sublattice features are much less common, and guidelines for predictably targeting such sublattice features are not well established. Here, we report that both anion and cation sublattice features--hexagonal close-packed anions and tetrahedrally coordinated cations-can be preserved during cation exchange of roxbyite-type Cu2-xS nanocrystals to selectively produce wurtzite-type CoS and MnS. These polymorphs, which are metastable in bulk systems, form relative to other accessible structures having cubic close-packed anions and/or octahedrally coordinated cations. To facilitate these transformations, the scope of existing nanocrystal cation-exchange reactions was expanded to include 3d transition metal systems that previously have not been investigated in depth. [ABSTRACT FROM AUTHOR]

In the wake of the discovery of the remarkable electronic and physicalproperties of graphene, a vibrant research area on two-dimensional(2D) layered materials has emerged during the past decade. Transitionmetal dichalcogenides (TMDs) represent an alternative group of 2Dlayered materials that differ from the semimetallic character of graphene.They exhibit diverse properties that depend on their composition andcan be semiconductors(e.g., MoS2, WS2), semimetals(e.g., WTe2, TiSe2), true metals(e.g., NbS2, VSe2), and superconductors(e.g., NbSe2, TaS2). The properties of TMDs can also be tailored accordingto the crystalline structure and the number and stacking sequenceof layers in their crystals and thin films. For example, 2H-MoS2is semiconducting, whereas 1T-MoS2is metallic. Bulk 2H-MoS2possessesan indirectband gap, but when 2H-MoS2is exfoliated into monolayers, it exhibits directelectronic and optical band gaps, which leads to enhanced photoluminescence.Therefore, it is important to learn to control the growth of 2D TMDstructures in order to exploit their properties in energy conversionand storage, catalysis, sensing, memory devices, and other applications. [ABSTRACT FROM AUTHOR]

Fatty acid salts of transition metalsare known to undergo thermaldecomposition in high-boiling organic solvents. Although it is a straightforward,promising approach for generating colloidal metal oxide nanocrystalsin high yield, its widespread implementation is hindered by irreproducibility.Subtle structural variations and impurities are often introduced duringpreparation of the carboxylate precursors, which exhibit strong influenceon thermal decomposition, and the resulting nucleation and growthof oxide nanocrystals. Here, we studied the colloidal synthesis ofwurtzite-type CoO (wz-CoO) nanostructures via thermaldecomposition of Co(II) oleate complex [Co(OL)]2. UsingFourier transform infrared spectroscopy, we discovered that the conventionalmethod for preparing [Co(OL)]2gives rise to an isolableimpurity containing a free hydroxide moiety. Furthermore, [Co(OL)]2did not thermally decompose within the expected temperaturerange when the impurity was removed. In contrast, pencil-shaped wz-CoO nanorods were synthesized when no measures were takento remove the impurity, suggesting that the hydroxide functionalitymay facilitate the thermal decomposition. These insights enabled usto prepare size-and shape-controlled wz-CoO nanocrystalsusing purified [Co(OL)]2solutions, by incorporating additivesthat mimic the action of the hydroxide impurity. We also demonstratea simplified pathway to wz-CoO nanocrystals thatdoes not require chemical additives for thermolysis. [ABSTRACT FROM AUTHOR]

Colloidal hybrid nanoparticles, whichcontain multiple inorganicdomains that are joined together through solid–solid interfaces,exhibit particle multifunctionality as well as new and enhanced propertiesthat can emerge from the particle–particle interactions. Thesehybrid nanoparticles are typically synthesized using heterogeneousseeded nucleation of one nanoparticle on the surface of another aswell as using phase segregation, surface dewetting of core–shellnanoparticles, and the fusion of premade nanoparticles. However, toexpand the materials diversity and the potential range of applicationsof such systems, alternative routes to heterogeneous seeded nucleationare needed. Here, we show that solution–liquid–solidand related supersaturation-precipitation strategies, traditionallyused in the synthesis of 1D structures such as nanowires and nanorods,can also be applied to the synthesis of colloidal hybrid nanoparticles.Specifically, we show that colloidal Au and Ag nanoparticles can serveas seeds for the growth of colloidal Au–Ge and Ag–Geheterodimers upon reaction with Ge(HMDS)2(Ge(II)bis(hexamethyldisilylamide))at ∼290 and ∼320 °C, respectively. By modifyingthe size of the seed nanoparticles and the amount of Ge(HMDS)2, the widths and lengths of the Ge domains can be systematicallytuned. Additionally, the Ge domains can serve as site-selective templatesfor the galvanic deposition of metal nanoparticles, forming trimericAu–Ge–(Ag)nnanostructures.This alternate route to colloidal hybrid nanoparticles facilitatesthe integration of previously inaccessible group IV elements, andit could open the door to the design and synthesis of a wide rangeof new functional colloidal nanostructures. [ABSTRACT FROM AUTHOR]

High throughput theoretical methods are increasingly used to identify promising photocatalytic materials for hydrogen generation from water as a clean source of energy. While most promising water splitting candidates require co-catalyst loading and electrical biasing, computational costs to predict them a priori become large. It is, therefore, important to identify bare, bias-free semiconductor photocatalysts with small initial hydrogen production rates, often in the range of tens of nanomoles per hour, as these can become highly efficient with further co-catalyst loading and biasing. Here, we report a sensitive hydrogen detection system suitable for screening new photocatalysts. The hydrogen evolution rate of the prototypical rutile TiO2 loaded with 0.3 wt. % Pt is detected to be 78.0 ± 0.8 µmol/h/0.04 g, comparable with the rates reported in the literature. In contrast, sensitivity to an ultralow evolution rate of 11.4 ± 0.3 nmol/h/0.04 g is demonstrated for bare polycrystalline TiO2 without electrical bias. Two candidate photocatalysts, ZnFe2O4 (18.1 ± 0.2 nmol/h/0.04 g) and Ca2PbO4 (35.6 ± 0.5 nmol/h/0.04 g) without electrical bias or co-catalyst loading, are demonstrated to be potentially superior to bare TiO2. This work expands the techniques available for sensitive detection of photocatalytic processes toward much faster screening of new candidate photocatalytic materials in their bare state. [ABSTRACT FROM AUTHOR]

Topological materials have high carrier mobilities that can be maintained in the presence of crystal structure defects, which is useful for catalysis. Topological materials have been shown to be active catalysts, but it remains unclear if topology persists during catalysis. We studied the physical and chemical evolution of MoTe2 during photo‐ and electrocatalytic hydrogen production. This material offers a unique opportunity to directly compare a trivial semiconductor, 2H‐MoTe2, with a topological insulator, 1T'‐MoTe2, with comparable compositions, crystal structures, and surface roughnesses. We observed no major bulk changes in the materials after catalysis. The surfaces of the catalysts were significantly roughened and oxidized, but the carrier mobility of the topological phase remained high. These results suggest that topology persists during, and may be advantageous for, catalysis, and provide rationale for considering topology in the search for water‐splitting catalysts. [ABSTRACT FROM AUTHOR]

Tin sulfide, SnS, is a narrow band gap semiconductor comprised of inexpensive, earth abundant, and environmentally benign elements that is emerging as an important material for a diverse range of applications in solar energy conversion, energy storage, and electronics. Relative to many comparable systems, much less is known about the factors that influence the synthesis or morphology-dependent properties of SnS nanostructures. Here, we report the synthesis of colloidal SnS cubes, spherical polyhedra, and sheets and demonstrate their activity for the photocatalytic degradation of methylene blue. We also study their morphology-dependent polymorphism using an in-depth crystallographic analysis that correlates high-resolution TEM data of individual nanocrystals with ensemble-based electron diffraction and powder XRD data. These studies reveal that the crystal structure adopted by the SnS cubes and spherical polyhedra is expanded along the a and b axes and contracted along c, converging on a pseudotetragonal cell that is distinct from that of orthorhombic a-SnS, the most stable polymorph. All of the peaks observed in powder XRD patterns that are often interpreted as originating from a mixture of metastable zincblende-type SnS and a-SnS can instead be accounted for by this single-phase pseudotetragonal modification, and this helps to rationalize discrepancies that exist between theoretical predictions of SnS polymorph stability and interpretations of experimental diffraction data. This same crystallographic analysis also indicates the morphologies of the nanocrystals and the facets by which they are bound, and it reveals that the SnS cubes form through selective overgrowth of spherical polyhedral seeds. [ABSTRACT FROM AUTHOR]

Colloidal hybrid nanoparticles contain multiple domains that are directly fused together through a solid–solid interface, which facilitates synergistic interactions between the components that can lead to enhanced properties, as well as multifunctionality in a single particle. By nucleating one nanoparticle on the surface of another,a growing number of these hybrid nanoparticles can be synthesized. However, to rapidly expand the materials diversity of such systems,alternative routes to heterogeneous seeded nucleation are needed. Here, we show that solution-mediated chemical transformation reactions,which are well established for pseudomorphically transforming colloidal metal nanoparticles into derivative metal-containing phases, can also be applied to colloidal hybrid nanoparticles. Specifically, we show that Pt–Fe3O4heterodimers react with Pb(acac)2and Sn(acac)2at 180–200 °Cin a mixture of benzyl ether, oleylamine, oleic acid, and tert-butylamine borane to form PtPb–Fe3O4and Pt3Sn–Fe3O4heterodimers, respectively. This chemical transformation reaction introduces intermetallic and alloy components into the heterodimers,proceeds with morphological retention, and preserves the solid–solid interface that characterizes these hybrid nanoparticle systems. In addition, the PtPb–Fe3O4 heterodimers spontaneously aggregate to form colloidally stable (PtPb–Fe3O4 )n nanoflowers via a process that is conceptually analogous to a molecular condensation reaction. These reactions add to the growing toolbox of predictable manipulations of colloidal hybrid nanoparticles, ultimately expanding their materials diversity and range of potential applications. [ABSTRACT FROM AUTHOR]

Colloidal hybrid nanoparticles contain multiple nanoscale domains fused together by solid-state interfaces. They represent an emerging class of multifunctional lab-on-a-particle architectures that underpin future advances in solar energy conversion, fuel-cell catalysis, medical imaging and therapy, and electronics. The complexity of these 'artificial molecules' is limited ultimately by the lack of a mechanism-driven design framework. Here, we show that known chemical reactions can be applied in a predictable and stepwise manner to build complex hybrid nanoparticle architectures that include M-Pt-Fe3O4 (M = Au, Ag, Ni, Pd) heterotrimers, MxS-Au-Pt-Fe3O4 (M = Pb, Cu) heterotetramers and higher-order oligomers based on the heterotrimeric Au-Pt-Fe3O4 building block. This synthetic framework conceptually mimics the total-synthesis approach used by chemists to construct complex organic molecules. The reaction toolkit applies solid-state nanoparticle analogues of chemoselective reactions, regiospecificity, coupling reactions and molecular substituent effects to the construction of exceptionally complex hybrid nanoparticle oligomers. [ABSTRACT FROM AUTHOR]

Abstract: Au–Zn was used as a prototype binary system for exploring intermetallic phase accessibility in nanoparticle systems using low-temperature solution chemistry methods. By reacting Au nanoparticles with diethylzinc (Et2Zn) in oleylamine at temperatures of 250–300°C, nanoparticles of five distinct binary intermetallic compounds were accessible: Au3Zn, Au5Zn3, AuZn, Cu5Zn8-type γ-(Au,Zn), and Mg-type ɛ-(Au,Zn). A variety of nanoparticle shapes, including spheres, triangles, hexagons, and rods, are accessible in the Au–Zn system via a pseudomorphic reaction of Au nanocrystal shapes with Et2Zn. The Au–Zn nanoparticles have optical properties that vary with Zn content, ranging from a surface plasmon resonance peak at ∼495nm for Au3Zn to absorption in the ultraviolet region for the Zn-rich phases. [Copyright &y& Elsevier]

Abstract: The effect of adding Pt to a Pd/SiO2 catalyst for the direct formation of H2O2 in ethanol that contains H2SO4 and halide ions (Cl− or Br−) has been investigated. The addition of only 5atom% Pt to a catalyst that contained 0.5wt.% Pd resulted in a 2.5-fold increase in the rate of peroxide formation with only a small decrease in selectivity. The addition of substantially more Pt caused a decrease in the selectivity; whereas, the peroxide formation rate depended on the amount of Pt, as well as the type and amount of the halide. The Pt had no significant effect on the particle size distribution of the supported bimetallic catalysts. The positive role of Pt on the rate of H2O2 formation can be understood in terms of an electronic modification through which Pt partially reverses the negative influence that the halides have on hydrogen activation. [Copyright &y& Elsevier]

[Display omitted] • Zn and Fe-doped CuO nanosheets improve dye degradation under visible light. • Doping CuO enhances absorption and reduces recombination for higher photocatalytic activity. • Transition metal-doped 2D materials show potential for photocatalytic POPs remediation. Herein, we report a comprehensive investigation of Zn- and Fe-doped CuO nanosheets as promising photocatalysts for the degradation of organic dyes. These nanosheets were synthesized via a hydrothermal process and thoroughly characterized through spectroscopic and microscopic techniques. Photocatalytic degradation experiments using methylene blue (MB) and malachite green (MG) revealed a marked increase in efficiency within the doped CuO nanosheets when compared to their undoped counterparts. The degradation kinetics showed MB following a zero-order model and MG following a first-order model. In particular, Zn and Fe-doped CuO nanosheets outperformed undoped CuO, degrading 66% and 73% of MB and 85% and 90% of MG within specific timeframes, while undoped CuO achieved 62% and 76% degradation, respectively. Computational analysis conducted with Gaussian 09 software pinpointed reactive sites susceptible to radical and electrophilic attacks in the dyes. The enhanced performance is credited to transition metal doping, which induces a red shift in the optical band gap, thereby improving visible light absorption and diminishing electron-hole recombination. This study underscores the potential of transition metal doping in bandgap engineering for efficient visible light-assisted photocatalytic remediation. [ABSTRACT FROM AUTHOR]