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Colloidal copper(I) sulfide (Cu2–xS) nanocrystals (NCs) have attracted much attention for a wide range of applications because of their unique optoelectronic properties, driving scientists to explore the potential of using Cu2–xS NCs as seeds in the synthesis of heteronanocrystals to achieve new multifunctional materials. Herein, we developed a multistep synthesis strategy toward Cu2–xS/ZnS heteronanorods. The Janus-type Cu2–xS/ZnS heteronanorods are obtained by the injection of hexagonal high-chalcocite Cu2–xS seed NCs in a hot zinc oleate solution in the presence of suitable surfactants, 20 s after the injection of sulfur precursors. The Cu2–xS seed NCs undergo rapid aggregation and coalescence in the first few seconds after the injection, forming larger NCs that act as the effective seeds for heteronucleation and growth of ZnS. The ZnS heteronucleation occurs on a single (100) facet of the Cu2–xS seed NCs and is followed by fast anisotropic growth along a direction that is perpendicular to the c-axis, thus leading to Cu2–xS/ZnS Janus-type heteronanorods with a sharp heterointerface. Interestingly, the high-chalcocite crystal structure of the injected Cu2–xS seed NCs is preserved in the Cu2–xS segments of the heteronanorods because of the high-thermodynamic stability of this Cu2–xS phase. The Cu2–xS/ZnS heteronanorods are subsequently converted into single-component Cu2–xS and CuInS2 nanorods by postsynthetic topotactic cation exchange. This work expands the possibilities for the rational synthesis of colloidal multicomponent heteronanorods by allowing the design principles of postsynthetic heteroepitaxial seeded growth and nanoscale cation exchange to be combined, yielding access to a plethora of multicomponent heteronanorods with diameters in the quantum confinement regime.

ZnS shelling of I-III-VI2 nanocrystals (NCs) invariably leads to blue-shifts in both the absorption and photoluminescence spectra. These observations imply that the outcome of ZnS shelling reactions on I-III-VI2 colloidal NCs results from a complex interplay between several processes taking place in solution, at the surface of, and within the seed NC. However, a fundamental understanding of the factors determining the balance between these different processes is still lacking. In this work, we address this need by investigating the impact of precursor reactivity, reaction temperature, and surface chemistry (due to the washing procedure) on the outcome of ZnS shelling reactions on CuInS2 NCs using a seeded growth approach. We demonstrate that low reaction temperatures (150 °C) favor etching, cation exchange, and alloying regardless of the precursors used. Heteroepitaxial shell overgrowth becomes the dominant process only if reactive S- and Zn-precursors (S-ODE/OLAM and ZnI2) and high reaction temperatures (210 °C) are used, although a certain degree of heterointerfacial alloying still occurs. Remarkably, the presence of residual acetate at the surface of CIS seed NCs washed with ethanol is shown to facilitate heteroepitaxial shell overgrowth, yielding for the first time CIS/ZnS core/shell NCs displaying red-shifted absorption spectra, in agreement with the spectral shifts expected for a type-I band alignment. The insights provided by this work pave the way toward the design of improved synthesis strategies to CIS/ZnS core/shell and alloy NCs with tailored elemental distribution profiles, allowing precise tuning of the optoelectronic properties of the resulting materials.

Colloidal 2D semiconductor nanosheets (NSs) are an interesting new class of materials due to their unique properties. However, synthesis of these NSs is challenging and synthesis procedures for materials other than the well-known Pb- and Cd- chalcogenides are still underdeveloped. In this paper, we present a new approach to make copper indium sulfide (CIS) NSs and study their structural and optical properties. The CIS NSs form via self-organization and oriented attachment of 2.5 nm sized chalcopyrite CuInS2 nanocrystals (NCs), yielding triangular and hexagonal shaped NSs with a thickness of ~3 nm and lateral dimensions ranging from 20 to 1000 nm. The self-organization is induced by fast cation extraction, leading to attractive dipolar interactions between the NCs. Primary amines play a crucial role in the formation of the CIS NSs, both by forming in situ the cation extracting agent, and by preventing the attachment of NCs to the top and bottom facets of the NSs. Moreover, DFT calculations reveal that the amines are essential to stabilize the covellite crystal structure of the product CIS NSs. The NSs are indium-deficient and the off-stoichiometry gives rise to a plasmon resonance in the NIR spectral window.

The self-assembly of different nanocrystals into a binary superlattice is of interest for both colloidal science and nanomaterials science. New properties may emerge from the interaction between the nanocrystal building blocks that are ordered in close contact in three dimensions. Identification of the superlattice structure including its defects is of key interest in understanding the electrical and optical properties of these systems. Transmission electron microscopy (TEM) has been very instrumental to reach this goal but fails for complex crystal structures and buried defects. Here, we use electron tomography to resolve the three-dimensional crystal structure of a binary superlattice that could not be resolved by TEM only. The structure with a [PbSe]6[CdSe]19 stoichiometry has no analogue in the atomic world. Moreover we will show how tomography can overcome the clouding effects of planar defects on structure identification by TEM.

The 3D distribution of nanocrystals at the liquid-air interface is imaged for the first time on a single-particle level by cryogenic electron tomography, revealing the equilibrium concentration profile from the interface to the bulk of the liquid. When the surface tension of the liquid is decreased, the interaction of the nanocrystals with the liquid-air interface shifts from adsorption to desorption. Macroscopic surface tension measurements do not detect this transition, due to the presence of surface-active molecular species.

Particle growth is a major deactivation mechanism for supported metal catalysts. This study reveals that the impact of pore size on catalyst stability is very sensitive to the nanoscale metal distribution. A set of ex-nitrate CuZn/SiO2 catalysts was synthesised using SiO2-gel supports (pore size 5-23 nm). The catalyst compositions were adjusted to attain series of catalysts with either constant pore volumetric (1.6 Cu nm-3) or surface (2.0 Cu nm-2) overall metal loading. The procedures of thermal decomposition of the metal nitrate precursors were adjusted to achieve

Several commercially available samples consisting of agglomerated small mordenite crystallites with low Si/Al ratios (5.7–10 at/at) have been treated in aqueous NaOH solution. It was found that the porosity can be enhanced when the sodium hydroxide solution is sufficiently concentrated. Treatment in 1 M NaOH for 15 min resulted in inter-crystalline porosity and the mesopore volume was increased from 0.01 to 0.21 cm3 g−1 together with an increased external surface area from 36 to 85 m2 g−1. The micropore volume and crystallinity were preserved after the treatment. Both H-MOR and Na-MOR mordenite agglomerates have been successfully treated: the Na-MOR requires a longer contact time to obtain similar porosity. By carefully choosing the alkaline concentration and contact time, intra-crystalline mesoporosity can be obtained for mordenite with Si/Al ratios as low as 10. Catalytic tests with proton mordenite showed that alkaline treatment leads to more than one order of magnitude of activity gain in the liquid-phase alkylation of benzene with propene to form cumene, while selectivity is preserved. These results demonstrate that alkaline treatment also on high-aluminum content mordenites is an effective tool to enhance accessibility and thereby its catalytic performance.

We report the synthesis of ultranarrow (Zn,Cd)Te/CdSe colloidal heteronanowires, using ZnTe magic size clusters as seeds. The wire formation starts with a partial Zn for Cd cation exchange, followed by self-organization into segmented heteronanowires. Further growth occurs by inclusion of CdSe. The heteronanowires emit in the 530 to 760 nm range with high quantum yields. The electron-hole overlap decreases with increasing CdSe volume fraction, allowing the optical properties to be controlled by adjusting the heteronanowire composition.

Quantum dots form equilibrium structures in liquid dispersions, due to thermodynamic forces that are often hard to quantify. Analysis of these structures, visualized using cryogenic electron microscopy, yields their formation free energy. Here we show that the nanoparticle interaction free energy can be further separated into the enthalpic and entropic contributions, using the temperature dependence of the assembled structures. Monodisperse oleic acid-capped PbSe nanoparticles dispersed in decalin were used as a model system, and the temperature-dependent equilibrium structures were imaged by cryo-TEM, after quenching from different initial temperatures. The interaction enthalpy and entropy follow from van ’t Hoff’s exact equation for the temperature dependence of thermodynamic equilibria, now applied to associating nanoparticles. The enthalpic component gives the magnitude of the contact interaction, which is crucial information in understanding the energetics of the self-assembly of nanoparticles into ordered structures.

Electrostatic forces play an important role in the interaction between large transition metal complexes and lipid bilayers. In this work, a thioether-cholestanol hybrid ligand (4) was synthesized, which coordinates to ruthenium(II) via its sulfur atom and intercalates into lipid bilayers via its apolar tail. By mixing its ruthenium complex [Ru(terpy)(bpy)(4)](2+) (terpy = 2,2';6',2''-terpyridine; bpy = 2,2'-bipyridine) with either the negatively charged lipid dimyristoylphosphatidylglycerol (DMPG) or with the zwitterionic lipid dimyristoylphosphatidylcholine (DMPC), large unilamellar vesicles decorated with ruthenium polypyridyl complexes are formed. Upon visible light irradiation the ruthenium-sulfur coordination bond is selectively broken, releasing the ruthenium fragment as the free aqua complex [Ru(terpy)(bpy)(OH(2))](2+). The photochemical quantum yield under blue light irradiation (452 nm) is 0.0074(8) for DMPG vesicles and 0.0073(8) for DMPC vesicles (at 25 °C), which is not significantly different from similar homogeneous systems. Dynamic light scattering and cryo-TEM pictures show that the size and shape of the vesicles are not perturbed by light irradiation. Depending on the charge of the lipids, the cationic aqua complex either strongly interacts with the membrane (DMPG) or diffuses away from it (DMPC). Back coordination of [Ru(terpy)(bpy)(OH(2))](2+) to the thioether-decorated vesicles takes place only at DMPG bilayers with high ligand concentrations (25 mol %) and elevated temperatures (70 °C). During this process, partial vesicle fusion was also observed. We discuss the potential of such ruthenium-decorated vesicles in the context of light-controlled molecular motion and light-triggered drug delivery.

An important reason to prepare magnetic nanoparticles of uniform size and shape is to ensure uniform magnetic properties. However, here, we demonstrate that magnetic iron oxide crystals of 20 nm or less with a low polydispersity of the geometric size can nevertheless have a strikingly broad distribution of the magnetic dipole moment. A comparative study was performed on nanoparticles with near-perfect crystallinity, twinning defects, or a high density of dislocations. Size, shape, and crystal defects were characterized with electron microscopy and X-ray diffraction, and magnetic dipole moments were determined from magnetization curves of dilute colloidal dispersions. The largest divergence was found for spherical particles with 3.5% geometric size polydispersity and 35% magnetic size polydispersity due to crystal lattice defects that disrupt single-domain magnetic spin coupling. This is in stark contrast with the usual implicit assumption that uniform size and shape guarantee welldefined magnetic properties of the individual particles.

E-configured ethenylene-bridged periodic mesoporous organosilicas with ultra-large mesopores and unprecedented pore volumes have been developed for the first time.

Binary nanocrystal superlattices, that is, ordered structures of two sorts of nanocolloids, hold promise for a series of functional materials with novel collective properties. Here we show that based on electron tomography a comprehensive, quantitative, three-dimensional characterization of these systems down to the single nanocrystal level can be achieved, which is key in understanding the emerging materials properties. On four binary lattices composed of PbSe, CdSe, and Au nanocrystals, we illustrate that ambiguous interpretations based on two-dimensional transmission electron microscopy can be prevented, nanocrystal sizes and superlattice parameters accurately determined, individual crystallographic point and plane defects studied, and the order/disorder at the top and bottom surfaces imaged. Furthermore, our results suggest that superlattice nucleation and growth occurred at the suspension/air interface and that the unit cells of some lattices are anisotropically deformed upon drying.

The polyoxometalates or POMs (clusters comprising at least two metal and many oxygen atoms) have recently gained significant interest owing to their versatile architecture and especially their catalytic activities. Due to their high catalytic activity but low surface area, there is always a demand for making high surface area POMs. This work demonstrates the attachment of the anionic {Mo72Fe30} POMs to gibbsite nanoplatelets with a residual positive charge to form large surface area composites. The resulting composite reported here has been characterized using cryo-TEM imaging, EDX/STEM (elemental) analysis, ATR-IR spectroscopy, SAXS, electrophoretic mobility determination and XRD. The composite reported here could find application in catalysis.

In this paper we show that self-organization of colloidal PbSe and CdSe semiconductor nanocrystals with a size ratio of 0.57 leads to binary structures with a AB2 or a cuboctahedral AB13 lattice. The type of superlattice formed can be regulated by the relative concentration of both nanocrystals in the suspension.

Glycerol is an attractive renewable building block for the synthesis of di- and triglycerols, which have numerous applications in the cosmetic and pharmaceutical industries. In this work, the selective etherification of glycerol to di- and triglycerol was studied in the presence of alkaline earth metal oxides and the data are compared with those obtained with Na2CO3 as a homogeneous catalyst. It was found that glycerol conversion increased with increasing catalyst basicity; that is, the conversion increases in the order: MgO90 % at 60 % conversion) are obtained over CaO, SrO, and BaO. For these catalysts no substantial acrolein formation was observed. Furthermore, at the start of the reaction mainly linear diglycerol was produced, whereas at higher conversion degrees branched diglycerol started to form. In another series of experiments different types of CaO materials were prepared. It was found that these CaO-based materials not only differed in their surface area and number of basic sites, but also in their Lewis acid strength. Within this series the CaO material possessing the strongest Lewis acid sites had the highest catalytic activity, comparable to that of BaO, pointing towards the important role of Lewis acidity for this etherification reaction. Based on these observations a plausible alternative reaction scheme for glycerol etherification is presented, which considers the facilitation of the hydroxyl leaving process. Finally, the stability of the catalytic solids under study was investigated and it was found that colloidal CaO particles of about 50-100 nm can be spontaneously generated during reaction. Catalytic testing of these CaO colloids, after isolation from the reaction medium, revealed a very high etherification activity. Understanding the nature of these Ca-based colloids opens new opportunities for investigating supported colloidal particle catalysts to take advantage of both their hetero- and homogeneous nature.

Magnesium dihydride contains 7.7 wt % hydrogen. However, its application for hydrogen storage is impeded by its high stability and slow kinetics. Bringing the size of Mg(H2) into the nanometer range will not only enhance the reaction rates but has also been theoretically predicted to change the thermodynamic stability and destabilize the MgH2 with respect to Mg. However, the preparation of such small particles is a major challenge. We identified a method to prepare large amounts of nanometer-sized nonoxidized magnesium crystallites. The method is based on infiltration of nanoporous carbon with molten magnesium. The size of the Mg crystallites is directly influenced by the pore size of the carbon and can be varied from 2–5 to less than 2 nm. The majority of the nanocrystallites is not oxidized after preparation. No bulk magnesium was detected in the samples with nanoparticle loadings up to 15 wt % on carbon. These 3D supported nanomaterials present interesting systems to study how nanosizing and support interaction can steer the hydrogen sorption properties of metal hydrides.

We show that polyoxometalate (ammonium phosphomolybdate) Keggin in aqueous dispersions upon sonication spontaneously transforms into micrometer-sized, peapod-shaped structures. The formation of these peapods is preceded by the generation of spherical aggregates. The particles have been characterized experimentally by time-resolved dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning TEM with a high-angle annular dark field detector (STEM-HAADF) for energy-dispersive X-ray (STEM/EDX) elemental analyses. A pathway for the phenomenon is proposed.