Ultrasmall Metal Research Articles

Efficient Enzyme‐Metal Hybrid Catalysts Constructed with Polymer

AbstractRational design and construction of enzyme‐metal hybrid catalysts (EMHCs) with high activity and stability is challenging. Introducing polymers into EMHCs is a promising way to enhance the catalytic performance by controlling the synthesis of ultrasmall metal nanoparticles on enzymes, and altering the surface properties of EMHCs, which has been wildly applied in organic synthesis and biomedicine. This review summarizes three representative strategies for the construction of EMHCs with polymers, including: using enzyme‐polymer conjugate as nanoreactors, using polymers as self‐assemble modules, and using polymers as surface modifiers. The effects of polymers on morphology and catalytic activity of EMHCs are discussed. Finally, the research directions of this field are proposed.

In Situ Confinement of Ultrasmall Metal Nanoparticles in Short Mesochannels for Durable Electrocatalytic Nitrate Reduction with High Efficiency and Selectivity.

Electrocatalytic reduction is a sustainable approach for NO3 - removal and high-value N-containing compounds manufacturing, which, however, is strongly obstructed by sluggish kinetics, low selectivity, and poor stability. Herein, the in situ confinement of ultrasmall CuPd alloy nanoparticles in mesochannels of conductive core-shell structured carbon nanotubes@mesoporous carbon substrates (CNTs@mesoC@CuPd) via a simple molecule-mediated interfacial assembly method is reported. As a catalyst for electrocatalytic NO3 - reduction, the CNTs@mesoC@CuPd shows a splendid conversion efficiency (100%), N2 selectivity (98%), cycling stability (>30days), and removal capacity as high as 30000mgNg-1 CuPd, which are much superior to most of the prior reports. Notably, experimental (in situ testing and isotopic labeling) and theoretical results unveil that bimetallic and monometallic catalysts for electrocatalytic NO3 - reduction exhibit exclusive selectivity for N2 and NH3 , respectively. This in situ confinement strategy is universal for the synthesis of stable and highly accessible metallic catalysts, which opens an appealing way to synthesize advanced catalysts with high activity, selectivity, and stability.

Ultrasmall Cluster Model for Investigating Single Atom Catalysis: Dehydrogenation of 1-Propanamine by Size-Selected Pt1Zr2O7 Clusters Supported on HOPG.

The selective dehydrogenation of hydrocarbons and their functionalized derivatives is a promising pathway in the realization of endothermic fuel systems for powering important technologies such as hypersonic aircraft. The recent surge in interest in single atom catalysts (SACs) over the past decade offers the opportunity to achieve the ultimate levels of selectivity through the subnanoscale design tailoring of novel catalysts. Experimental techniques capable of investigating the fundamental nature of the active sites of novel SACs in well-controlled model studies offer the chance to reveal promising insights. We report here an approach to accomplish this through the soft landing of mass-selected, ultrasmall metal oxide cluster ions, in which a single noble metal atom bound to a metal oxide moiety serves as a model SAC active site. This method allows the preparation of model catalysts in which monodispersed neutral SAC model active sites are decorated across an inert electrically conductive support at submonolayer surface coverage, in this case, Pt1Zr2O7 clusters supported on highly oriented pyrolytic graphite (HOPG). The results contained herein show the characterization of the Pt1Zr2O7/HOPG model catalyst by X-ray photoelectron spectroscopy (XPS), along with an investigation of its reactivity toward the functionalized hydrocarbon molecule, 1-propanamine. Through temperature-programmed desorption/reaction (TPD/R) experiments it was shown that Pt1Zr2O7/HOPG decomposes 1-propanamine exclusively into propionitrile and H2, which desorb at 425 and 550 K, respectively. Conversely, clusters without the single platinum atom, that is, Zr2O7/HOPG, exhibited no reactivity toward 1-propanamine. Hence, the single platinum atom in Pt1Zr2O7/HOPG was found to play a critical role in the observed reactivity.

Universal rapid Joule carbothermal synthesis of flexible carbon/metal oxide lithiophilic membranes for high-performance lithium metal batteries

Surface engineering of carbon materials induces structural modulation with appealing functionalities for versatile applications. However, practical deployment demands simplified modification steps and time-saving operations. Microwave technology can produce a strong instant magnetic-heating effect, avoiding the presence of a temperature gradient to cause nanoparticle agglomeration and multiple synthesis stages. Herein, we propose a rapid Joule carbothermal synthesis of a 3D flexible carbon cloth with ultrasmall metal oxide nanoparticles (MOx@CC) upon microwave irradiation within several minutes. Owing to the extensive selection of metal precursors, this approach can be applied to achieve a variety of active metal oxide nanoparticles decorated on carbon cloth. Furthermore, the modified carbon cloth can serve as a lithiophilic framework to efficiently homogenize Li+ flux and mitigate the dendrite formation. Ascribed to these merits, a prototype of the prelithiation MOx@CC anode paired with the LiFePO4 cathode exhibits satisfactory performance upon repetitive cycling, highlighting the possibility for a safe battery system.

Depletion Driven Assembly of Ultrasmall Metal Nanoclusters: From Kinetically Arrested Assemblies to Thermodynamically Stable, Spherical Superclusters.

Nanoscale assembly of ultrasmall metal nanoclusters (MNCs) by means of molecular forces has proven to be a powerful strategy to engineer their molecule-like properties in multiscale dimensions. By leveraging depletion attraction as the guiding force, herein, we demonstrate the formation of kinetically trapped NCs assemblies with enhanced photoluminescence (PL) and excited state lifetimes and extend the principle to cluster impregnated cationic nanogels, nonluminescent Au(I)-thiolate complexes, and weakly luminescent CuNCs. We further demonstrate a thermal energy driven kinetic barrier breaking process to isolate these assemblies. These isolated assemblies are thermodynamically stable, built from a strong network among several discrete, ultrasmall AuNCs and exhibit several unusual properties such as high stability in various pH, strong PL, microsecond lifetimes, large Stocks shifts, and higher accumulation in the lysosome of cancer cells. We anticipate our strategy may find wider use in creating a large variety of MNC-based assemblies with many unforeseen arrangements, properties, and applications.

In-situ synthesis of ultra-small Ni nanoparticles anchored on palygorskite for efficient reduction of 4-nitrophenol

4-nitrophenol (4-NP) is an environmental pollutant with high toxicity and strong stability, which is difficult to degrade naturally. Reduction of 4-NP to 4-aminophenol (4-AP), an important chemical intermediate, is an economical and green method. The reduction process demands high-efficient catalysts, and ultra-small metal nanoparticles (NPs) are the great potential ones. Herein, ultra-small and monodisperse Ni nanoparticles (NiNPs) (5.1 nm) were successfully anchored on palygorskite (Pal), using nickel silicate (NiSi) as a welding-like joint, and the ultimate catalysts were NiNPs/NiSi/Pal nanocomposites. The NiNPs were in-situ reduced from the NiSi precursor, which was previously and in-situ grown on Pal. The size of NiNPs was adjustable by the NiSi precursor, while the size of the NiSi precursor was controlled by the etching degree cations of the crystal structure of Pal. The etching degree affected the amounts of octahedral released from Pal, and thus affected the amounts of freshly exposed SiO- bonds, which could capture Ni2+ ions, form SiONi bonds and promote the generation of NiSi. The as-prepared NiNPs/NiSi/Pal nanocomposites exhibited excellent catalytic activity for the reduction of 4-NP (52.67 × 10-3 s−1), and satisfactory recyclability. The excellent catalytic performance is mainly attributed to the full exposure of ultra-small NiNPs, which provides enough active sites and enables fast electron transfer between the catalysts and substrates. It is expected that the work could develop a new avenue for designation of ultra-small and monodisperse non-precious metal NPs, and contribute to the treatment of waste water containing 4-NP.

High-energy-density ferroelectric polymer nanocomposites utilizing the Coulomb-blockade effect

Ferroelectric polymers have been regarded as promising dielectric materials for high volumetric energy density dielectric capacitors due to their high dielectric constant and facile processability. However, ferroelectric dielectric polymers suffer from high intrinsic loss, resulting in low charge-discharge efficiency and insufficient breakdown strength. Here, a sandwich-structured ferroelectric polymer nanocomposite with high energy density is fabricated by sandwiching an array of ultra-small metal particles grown in-situ between two layers of ferroelectric polymers. Due to the unique Coulomb-blockade effect of the ultra-small metal particles, the nanocomposites with suitable distribution density of metal particles exhibit significantly suppressed leakage current density and superior breakdown strength. Compared with Au and Ag, the Pt particle with the highest work function is more effective in improving the capacitive performance of the polymer. In addition, it is revealed that within the theoretical particle size range where the Coulomb-blockade takes effect, the nanocomposite with larger metal particles exhibits better capacitive performance. The optimal composition with an extremely low fraction (0.07 vol%) of 10-nm-size Pt nanoparticles shows a remarkable discharge energy density of 28.6 J/cm3 and a charge-discharge efficiency of 76%. This method effectively suppresses the energy loss of ferroelectric polymers, and bypasses the dispersion issues in the traditional polymer nanocomposites, providing a new paradigm for fabricating high-energy-density and high-efficiency polymer dielectrics.

Screening of Protein-Based Ultrasmall Nanozymes for Building Cell-Mimicking Catalytic Vesicles.

Enzymes are an important component for bottom-up building of synthetic/artificial cells. Nanozymes are nanomaterials with intrinsic enzyme-like properties, however, the construction of synthetic cells using nanozymes is difficult owing to their high surface energy or large size. Herein, the authors show a protein-based general platform that biomimetically integrates various ultrasmall metal nanozymes into protein shells. Specifically, eight metal-based ultrasmall nano-particles/clusters are in situ incorporated into ferritin nanocages that are self-assembled by 24 subunits of ferritin heavy chain. As a nanozyme generator, such a platform is suitable for screening the desired enzyme-like activities, including peroxidase (POD), oxidase (OXD), catalase (CAT) and superoxide dismutase (SOD). After screening, it is found that Ru intrinsically possesses the highest POD-like and CAT-like activities, while Mn and Pt show the highest OXD-like and SOD-like activities, respectively. Additionally, the inducers/inhibitors of various nanozymes are screened from more than 50 compounds to improve or inhibit their enzyme-like activities. Based on the screened nanozymes and their inhibitors, a proof-of-conceptually constructs cell-mimicking catalytic vesicles to mimic or modulate the events of redox homeostasis in living cells. This study offers a type of artificial metalloenzyme based on nanotechnology and shows a choice for bottom-up enzyme-based synthetic cell systems in a fully synthetic manner.

Is there a common reaction pathway for chromium sulfides as anodes in sodium-ion batteries? A case study about sodium storage properties of MCr2S4 (M = Cr, Ti, Fe)

We present new insights into the electrochemical properties of three metal sulfides MCr2S4 (M = Cr, Ti, Fe) probed as anode materials in sodium-ion batteries for the first time. The electrodes deliver decent reversible capacities and good long-term cycle stability, e.g., 470, 375, and 524 mAh g−1 are obtained after 200 cycles applying 0.5 A g−1 for M = Cr, Ti, and Fe, respectively. The reaction mechanisms are investigated via synchrotron-based X-ray powder diffraction and pair distribution function analyses. The highly crystalline educts are decomposed into Na2S nanoparticles and ultra-small metal particles during initial discharge without formation of intermediate NaCrS2 domains as previously reported for CuCrS2 and NiCr2S4. After a full cycle, the structural integrity of MCr2S4 (M = Cr, Ti, Fe) is not recovered. Thus, the Na storage properties are attributed to redox reactions between nanoscopic to X-ray amorphous conversion products with only local atomic correlations M···S/S···S in the charged and M···M/Na···S in the discharged state.Graphical

Zeolite-encapsulated Cu nanoparticles with enhanced performance for ethanol dehydrogenation

The selective dehydrogenation of ethanol to acetaldehyde is one of the pivotal reactions for biomass valorization, wherein the well-defined and robust Cu-based solid catalysts are highly desired for potential practical application. Herein, ultra-small Cu metal nanoclusters (∼1.8 nm), encapsulated inside Silicate-1 (S-1), have been successfully fabricated by an in-situ approach. The as-synthesized Cu@S-1 catalyst shows a near quantitative ethanol conversion, a good acetaldehyde selectivity up to ∼90 %, and more importantly an excellent stability with no apparent deactivation even after a TOS of 110 h in the continuous dehydrogenation of ethanol to acetaldehyde at 523 K. Comprehensive and thorough characterization studies reveal that the spatial constraint environment of the zeolite could not only efficiently restrict the movements of Cu entities, which thus prevents the metal sintering during catalysis, but also induce a predominant amount of well-retained Cu+ species (up to ∼70 %) that play an essential role for the enhanced performance.

(Invited, Digital Presentation) Langmuir-Type In-Situ Doping Mechanism in Si1-xGex Epitaxial Growth by Chemical Vapor Deposition

Accurate knowledge of atomically controlled processing for group IV semiconductors is very important for the fabrication of Si-based ultrasmall metal–oxide–semiconductor (MOS) devices and Si-based heterodevices in ultralarge scale integration because high-performance devices require atomically ordered interface of heterointerfaces and doping profiles as well as strain engineering due to introduction of Ge and C into Si [1-6]. In this work, in-situ doping of dopant (P or B) and C in Si1-xGex (100) epitaxial growth using SiH4-GeH4-SiH3CH3-B2H6 or PH3- H2 gas mixtures at around 550 oC [7-9] is reviewed based on the Langmuir-type surface adsorption and reaction scheme and the experimental data.It is assumed that one SiH4 or GeH4 molecule in Si1-xGex growth is adsorbed at one free surface site in Si-Si, Si-Ge or Ge-Ge pair sites on the (100) surface and decomposes there, and that one dopant (SiH3CH3 or B2H6 or PH3) molecule occupies one free surface site, independently of SiH4 and GeH4 partial pressures.For in-situ doping of C, it is proposed that SiH3CH3 molecules are adsorbed and react at the pair sites and react at the B-occupied sites where B2H6 molecules have been adsorbed at the pair sites.For in-situ doping of B, it is proposed that B2H6 molecules are adsorbed and react at the pair sites and SiH4, GeH4, SiH3CH3 and B2H6 molecules react at the B-occupied sites.For in-situ P doping, it is proposed that both the P concentration and the Ge fraction x in Si1-xGex are enhanced by the self-limited adsorption of PH3 molecules with maximum 2 and maximum 1 atomic layers at the P-occupied sites where PH3 molecules have been adsorbed at Si-Si and Si-Ge pair sites, respectively and that the decrease of P concentration in Si1-xGex with increasing PH3 partial pressure in high P concentration region is caused by lower segregation coefficient of P at Si-Ge and Ge-Ge pair sites than that at Si-Si pair sites according to the Henry’s law.Fairly good agreement is obtained between all the experimental data and the calculated values using the modified Langmuir-type mechanism.These results open the way for generalization of atomically controlled surface reaction process in group IV semiconductors by CVD.[1] J. Murota: The Electrochemical Society Extended s, Fall Meeting, Detroit, Oct.17-21, 1982, Abs.No.226, p.363.[2] H. Ishii, Y. Takahashi and J. Murota, Appl. Phys. Lett., 47, 863 (1985).[3] J. Murota and S. Ono, Jpn. J. Appl. Phys., 33, 2290 (1994).[4] B. Tillack, B. Heinemann, D. Knoll, Thin Solid Films, 369, 189 (2000).[5] J. Murota, M. Sakuraba and B. Tillack, Jpn. J. Appl. Phys., 45, 6767 (2006).[6] B. Tillack, Y. Yamamoto, D. Bolze, B. Heinemann, H. Rücker, D. Knoll, J. Murota and W. Mehr, Thin Solid Films, 508, 279 (2006).[7] J. Murota, Y. Yamamoto, I. Costina, B. Tillack, V. Le Thanh, R. Loo and M. Caymax: ECS J. Solid State Sci. Technol., 7(6), P305 (2018).[8] J. Murota and H. Ishii, ECS J. Solid State Sci. Technol., 10(2), 024005 (2021).[9] J. Murota and H. Ishii, ECS J. Solid State Sci. Technol., 10(6), 064004 (2021).

Lethal Interactions of Atomically Precise Gold Nanoclusters and Pseudomonas aeruginosa and Staphylococcus aureus Bacterial Cells.

Ultrasmall metal nanoclusters (NCs) are employed in an array of diagnostic and therapeutic applications due to their tunable photoluminescence, high biocompatibility, polyvalent effect, ease of modification, and photothermal stability. However, gold nanoclusters' (AuNCs') intrinsically antimicrobial properties remain poorly explored and are not well understood. Here, we share an insight into the antimicrobial action of atomically precise AuNCs based on their ability to passively translocate across the bacterial membrane. Functionalized by a hydrophilic modified-bidentate sulfobetaine zwitterionic molecule (AuNC-ZwBuEt) or a more hydrophobic monodentate-thiolate, mercaptohexanoic acid (AuNC-MHA) molecule, 2 nm AuNCs were lethal to both Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacteria. The bactericidal efficiency was found to be bacterial strain-, time-, and concentration-dependent. The direct visualizations of the translocation of AuNCs and AuNC-cell and subcellular interactions were investigated using cryo-soft X-ray nano-tomography, transmission electron microscopy (TEM), and scanning TEM energy-dispersive spectroscopy analyses. AuNC-MHA were identified in the bacterial cytoplasm within 30 min, without evidence of the loss of membrane integrity. It is proposed that the bactericidal effect of AuNCs is attributed to their size, which allows for efficient energy-independent translocation across the cell membrane. The internalization of both AuNCs caused massive internal damage to the cells, including collapsed subcellular structures and altered cell morphology, leading to the eventual loss of cellular integrity.

Botryoidal nanolignin channel stabilized ultrasmall PdNP incorporating with filter membrane for enhanced removal of Cr(VI) via synergetic filtration and catalysis

Catalytic membrane technology, as a combination of membrane separation and catalysis, is a high-efficiency and feasible route for wastewater remediation. The controllable synthesis of ultrasmall metal nanoparticles on the membrane to maximize the size effect is a challenging task yet. Herein, the filter paper-based botryoidal nanolignin channel stabilized ultrasmall PdNP membrane (Pd@LNP/FP) was prepared by chemical crosslinking of epichlorohydrin (EPI), the nanolignin (LNP) serves as both reducing and capping agent for the in-situ synthesis of ultrasmall PdNP with enhanced active sites. The mean size of PdNP was effectively tuned from 1.76 to 2.09 nm by varying the LNP loading amount of composite membranes. The botryoidal LNP supported on FP also provides the nanoscale channel to keep reactants on active sites of ultrasmall PdNP to improve the catalytic performance of Pd@LNPE/FP. The complete removal of hazardous Cr(VI) required only 2.5 min using Pd@LNPE/FP membrane, the pseudo-first-order rate constant (k) is 1.2725 min−1, much higher than that of the Pd@LNPp/FP membrane prepared by physical composite (0.2885 min−1). Moreover, the rapid filtration-catalysis removal of Cr(VI) can be achieved by twice filtration, demonstrating the high efficiency and feasibility of Pd@LNPE/FP via synergetic filtration enrichment and catalysis reduction.

Iron single atoms and clusters anchored on natural N-doped nanocarbon with dual reaction sites as superior Fenton-like catalysts

Ultra-small metal clusters have emerged as one of the most promising alternatives to heterogeneous Fenton-like catalysts. Despite the high atom utilization and structural stability of catalysts with ultra-small clusters and single-atom sites, there is still challenging for the synthesis of these catalysts due to their facile aggregation. Herein, we successfully fabricated a catalyst (Fe-NC-900) with single-atom sites and ultra-small clusters by a ball milling method combined with subsequent pyrolysis process. Fe-NC-900 showed high efficiency and superior stability in the activation of peroxymonosulfate (PMS) for catalytic oxidation of refractory organic compounds. Chemical quenching experiments, electron paramagnetic resonance (EPR), in-situ Raman spectra, and electrochemical analysis indicated that the 1O2 oxidation was the main non-radical pathway rather than the high-valent iron oxidation and electron transfer mechanism for the degradation of RhB in the Fe-NC-900/PMS system. This work provides useful insights into the design and synthesis of the catalysts with single atoms and ultra-small clusters for practical applications in Fenton-like catalytic processes.

Ultra-fast phosphating synthesis of metastable crystalline phase-controllable ultra-small MPX/CNT (M = Pd, Pt, Ru) for polyalcohol electrooxidation

A general approach is reported for ultra-fast phosphating synthesis of a series of ultra-small (<5 nm) noble metal phosphides (MPX/CNT, M = Pd, Pt, Ru) which are successfully produced in just 75 s for the first time. The catalytic performance of the catalysts can be optimized by controlling the nanomaterials as the metastable crystalline phases. By altering the phosphorus source under the same conditions, the hexagonal structured Pd7P3 (NaH2PO2·H2O as P source) and monoclinic structured Pd6P (Na4P2O7 as P source) can be prepared successfully. Both of them exhibit excellent polyol oxidation performance in alkaline media. Monoclinic Pd6P/CNT and hexagonal Pd7P3/CNT have large ECSA which are confirmed as 82.1 m2 g−1 and 86.2 m2 g−1, respectively. Hexagonal Pd7P3/CNT has the highest mass activity of 6.14 A mgPd−1 (3.21 A mgPd−1 for Pd6P/CNT) for GOR, which far exceeded Pt/C (2.81 A mgPt−1). Meanwhile, the mass activity of monoclinic Pt5P2/CNT for EGOR achieved 12.4 A mgPt−1, which far exceeded Pt/C (6.8 A mgPt−1). The stability test proved that the activity decay of these catalysts was negligible after the 12-hour durability test. Meanwhile, they have excellent CO anti-poisoning abilities.

Ultrasmall Gold Nanoclusters-Enabled Fabrication of Ultrafine Gold Aerogels as Novel Self-Supported Nanozymes.

Metal aerogels represent an emerging type of functional porous materials with promising applications in diverse fields, but the fabrication of metal aerogels with specific structure and property still remains a challenge. Here, the authors report a new approach to fabricate metal aerogels by using ultrasmall metal nanoclusters (NCs) as functional building blocks. By taking D-penicillamine-stabilized gold NCs (AuNCs) with a diameter of 1.4nm as an example, Au aerogels with ultrafine ligament size (3.5nm) and good enzyme-mimic properties are synthesized. Detailed characterization shows that the obtained Au aerogels possess typical 3D self-supported porous network structure with high gold purity and surface area. Time-lapse spectroscopic and microscopic monitoring of the gelation process reveal that these ultrasmall AuNCs first grow into large nanoparticles before fusion into nanowire networks, during which both pH and the precursor concentration are identified to be the determining factor. Owing to their highly porous structure and abundant metal nodes, these self-supported Au aerogels display excellent peroxidase-like properties. This work provides a strategy for fabricating advanced metal aerogels by taking ultrasmall-sized metal NCs as building blocks, which also opens new avenues for engineering the structure and properties of metal aerogels for further advancing their applications.

Controlled Synthesis of Perforated Oxide Nanosheets with High Density Nanopores Showing Superior Water Purification Performance.

A method for creating genuine nanopores in high area density on monolayer two-dimensional (2D) metallic oxides has been developed. By use of the strong reduction capability of hydroiodic acid, active metal ions, such as FeIII and CoIII, in 2D oxide nanosheets can be reduced to a divalent charge state (2+). The selective removal of FeO2 and CoO2 metal oxide units from the framework can be tuned to produce pores in a range of 1-4 nm. By monitoring of the redox reaction kinetics, the pore area density can be also tuned from ∼0.9 × 104 to ∼3.3 × 105 μm-2. The universality of this method to produce much smaller pores and higher area density than the previously reported ones has been proven in different oxide nanosheets. To demonstrate their potential applications, ultrasmall metal organic framework particles were grown inside the pores of perforated titania oxide nanosheets. The optimized hybrid film showed ∼100% rejection of methylene blue (MB) from the water. Its water permeance reached 4260 L m-2 h-1 bar-1, which is 1-3 orders of that for reported 2D membranes with good MB rejections.

DNA-Assisted Creation of a Library of Ultrasmall Multimetal/Metal Oxide Nanoparticles Confined in Silica.

Supported ultrasmall metal/metal oxide nanoparticles (UMNPs) with sizes in the range of 1-5nm exhibit unique properties in sensing, catalysis, biomedicine, etc. However, the metal-support and metal-metal precursor interactions were not as well controlled to stabilize the metal nanoparticles on/in the supports. Herein, DNA is chosen as a template and a ligand for the silica-supported UMNPs, taking full use of its binding ability to metal ions via either electrostatic or coordination interactions. UMNPs thus are highly dispersed in silica via self-assembly of DNA and DNA-metal ion interactions with the assistance of a co-structural directing agent (CSDA). A large number of metal ions are easily retained in the mesostructured DNA-silica materials, and their growth is controlled by the channels after calcination. Based on this directing concept, a material library, consisting of 50 mono- and 54 bicomponent UMNPs confined within silica and with narrow size distribution, is created. Theoretical calculation proves the indispensability of DNA with combination of several organics in the synthesis of ultrasmall metal nanoparticles. The Pt-silica and Pt/Ni-silica chosen from the library exhibit good catalytic performance for toluene combustion. This generalizable and straightforward synthesis strategy is expected to widen the corresponding applications of supported UMNPs.

Robust continuous synthesis and in situ deposition of catalytically active nanoparticles on colloidal support materials in a triphasic flow millireactor

• A triphasic flow millireactor for nanoparticle synthesis and deposition is designed. • Tunability of nanoparticle loading on the support is demonstrated. • A versatile method shown for various support materials – TiO 2 , Al 2 O 3 and CeO 2 . • Mono-/bi-/tri- metallics nanoparticles are deposited on colloidal support material. Ultra-small noble metal nanoparticles, such as palladium, platinum and rhodium, are invaluable catalysts for the synthesis of a plethora of materials, ranging from pharmaceutical drugs to polymers and fertilizers due to their high catalytic activities and large surface area-to-volume ratios. In practice, these particles are typically deposited on larger-sized support materials to stabilize them against agglomeration, whilst maintaining catalytic activity. We choose colloidal deposition as the process to synthesize supported nanoparticles, as it enables the deposition of nanoparticles with complex compositions and shapes on the support material, since the physical properties of the colloid nanoparticles are not affected by the deposition process. In this paper, we demonstrate a robust triphasic flow millireactor for catalytic nanoparticle synthesis and their facile in situ deposition onto colloidal support materials with tunable metal loading from 5% to 23% and a high degree of control over the spatial distribution on the support material. We highlight the consistency and quality of the supported nanoparticles produced by the flow synthesis compared to their batch-synthesized counterparts. We also demonstrate the versatility of our method for different nanoparticles types, including bi-/tri-metallics (Pd 5 Pt 5 , Rh 5 Pt 5 , Ru 5 Pt 5 and Rh 3 Pd 4 Pt 5 ) and three different support materials - titania, alumina and ceria.

Synthesis of ultrasmall metal nanoparticles and continuous shells at the liquid/liquid interface in Ouzo emulsions.

Herein, we report a novel method to synthesize metal nanoparticle-shells (NP-shells) and continuous shells at the liquid/liquid interface, via an interfacial reaction in an Ouzo emulsion. Ouzo emulsions spontaneously form submicronic droplets with a narrow size distribution, without any energy-intensive process. The Ouzo system in this work comprises water, tetrahydrofuran (THF) and butylated hydroxytoluene (BHT), and forms BHT-rich droplets (∼100 nm). The addition of a reducing agent (NaBH4) in the aqueous phase, and of a metal precursor (AuPPh3Cl and/or Pd(PPh3)2Cl2) in the BHT-rich droplets, results in the formation of Au nanoparticles (AuNPs), continuous Pd shells, or bimetallic shells, at the interface of the droplets. Control over the NP-shell size was achieved by the addition of a water-soluble polymer during the synthesis, which in turn leads to smaller NP-shells.