Showing papers on "Nanoparticle published in 2018"

Metal Catalysts for Heterogeneous Catalysis: From Single Atoms to Nanoclusters and Nanoparticles.

Abstract: Metal species with different size (single atoms, nanoclusters, and nanoparticles) show different catalytic behavior for various heterogeneous catalytic reactions. It has been shown in the literature that many factors including the particle size, shape, chemical composition, metal–support interaction, and metal–reactant/solvent interaction can have significant influences on the catalytic properties of metal catalysts. The recent developments of well-controlled synthesis methodologies and advanced characterization tools allow one to correlate the relationships at the molecular level. In this Review, the electronic and geometric structures of single atoms, nanoclusters, and nanoparticles will be discussed. Furthermore, we will summarize the catalytic applications of single atoms, nanoclusters, and nanoparticles for different types of reactions, including CO oxidation, selective oxidation, selective hydrogenation, organic reactions, electrocatalytic, and photocatalytic reactions. We will compare the results o...

A review of ZnO nanoparticles as solar photocatalysts: Synthesis, mechanisms and applications

Abstract: Persistent organic pollutants (POPs) are carbon-based chemical substances that are resistant to environmental degradation and may not be completely removed through treatment processes. Their persistence can contribute to adverse health impacts on wild-life and human beings. Thus, the solar photocatalysis process has received increasing attention due to its great potential as a green and eco-friendly process for the elimination of POPs to increase the security of clean water. In this context, ZnO nanostructures have been shown to be prominent photocatalyst candidates to be used in photodegradation owing to the facts that they are low-cost, non-toxic and more efficient in the absorption across a large fraction of the solar spectrum compared to TiO 2 . There are several aspects, however, need to be taken into consideration for further development. The purpose of this paper is to review the photo-degradation mechanisms of POPs and the recent progress in ZnO nanostructured fabrication methods including doping, heterojunction and modification techniques as well as improvements of ZnO as a photocatalyst. The second objective of this review is to evaluate the immobilization of photocatalyst and suspension systems while looking into their future challenges and prospects.

Carbothermal shock synthesis of high-entropy-alloy nanoparticles

Abstract: The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports [temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~10 5 K per second]. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.

Plasmonic Surface Lattice Resonances: A Review of Properties and Applications

Abstract: When metal nanoparticles are arranged in an ordered array, they may scatter light to produce diffracted waves. If one of the diffracted waves then propagates in the plane of the array, it may couple the localized plasmon resonances associated with individual nanoparticles together, leading to an exciting phenomenon, the drastic narrowing of plasmon resonances, down to 1–2 nm in spectral width. This presents a dramatic improvement compared to a typical single particle resonance line width of >80 nm. The very high quality factors of these diffractively coupled plasmon resonances, often referred to as plasmonic surface lattice resonances, and related effects have made this topic a very active and exciting field for fundamental research, and increasingly, these resonances have been investigated for their potential in the development of practical devices for communications, optoelectronics, photovoltaics, data storage, biosensing, and other applications. In the present review article, we describe the basic phy...

Direct observation of noble metal nanoparticles transforming to thermally stable single atoms.

Abstract: Single noble metal atoms and ultrafine metal clusters catalysts tend to sinter into aggregated particles at elevated temperatures, driven by the decrease of metal surface free energy. Herein, we report an unexpected phenomenon that noble metal nanoparticles (Pd, Pt, Au-NPs) can be transformed to thermally stable single atoms (Pd, Pt, Au-SAs) above 900 °C in an inert atmosphere. The atomic dispersion of metal single atoms was confirmed by aberration-corrected scanning transmission electron microscopy and X-ray absorption fine structures. The dynamic process was recorded by in situ environmental transmission electron microscopy, which showed competing sintering and atomization processes during NP-to-SA conversion. Further, density functional theory calculations revealed that high-temperature NP-to-SA conversion was driven by the formation of the more thermodynamically stable Pd-N4 structure when mobile Pd atoms were captured on the defects of nitrogen-doped carbon. The thermally stable single atoms (Pd-SAs) exhibited even better activity and selectivity than nanoparticles (Pd-NPs) for semi-hydrogenation of acetylene.

Nanoparticle-triggered in situ catalytic chemical reactions for tumour-specific therapy

Abstract: Tumour chemotherapy employs highly cytotoxic chemodrugs, which kill both cancer and normal cells by cellular apoptosis or necrosis non-selectively. Catalysing/triggering the specific chemical reactions only inside tumour tissues can generate abundant and special chemicals and products locally to initiate a series of unique biological and pathologic effects, which may enable tumour-specific theranostic effects to combat cancer without bringing about significant side effects on normal tissues. Nevertheless, chemical reaction-initiated selective tumour therapy strongly depends on the advances in chemistry, materials science, nanotechnology and biomedicine. This emerging cross-disciplinary research area is substantially different from conventional cancer-theranostic modalities in clinics. In response to the fast developments in cancer theranostics based on intratumoural catalytic chemical reactions, this tutorial review summarizes the very-recent research progress in the design and synthesis of representative nanoplatforms with intriguing nanostructures, compositions, physiochemical properties and biological behaviours for versatile catalytic chemical reaction-enabled cancer treatments, mainly by either endogenous tumour microenvironment (TME) triggering or exogenous physical irradiation. These unique intratumoural chemical reactions can be used in tumour-starving therapy, chemodynamic therapy, gas therapy, alleviation of tumour hypoxia, TME-responsive diagnostic imaging and stimuli-responsive drug release, and even externally triggered versatile therapeutics. In particular, the challenges and future developments of such a novel type of cancer-theranostic modality are discussed in detail to understand the future developments and prospects in this research area as far as possible. It is highly expected that this kind of unique tumour-specific therapeutics by triggering specific in situ catalytic chemical reactions inside tumours would provide a novel but efficient methodology for benefiting personalized biomedicine in combating cancer.

Ultrafine Co Nanoparticles Encapsulated in Carbon-Nanotubes-Grafted Graphene Sheets as Advanced Electrocatalysts for the Hydrogen Evolution Reaction.

Abstract: The rational design of an efficient and inexpensive electrocatalyst based on earth-abundant 3d transition metals (TMs) for the hydrogen evolution reaction still remains a significant challenge in the renewable energy area. Herein, a novel and effective approach is developed for synthesizing ultrafine Co nanoparticles encapsulated in nitrogen-doped carbon nanotubes (N-CNTs) grafted onto both sides of reduced graphene oxide (rGO) (Co@N-CNTs@rGO) by direct annealing of GO-wrapped core-shell bimetallic zeolite imidazolate frameworks. Benefiting from the uniform distribution of Co nanoparticles, the in-situ-formed highly graphitic N-CNTs@rGO, the large surface area, and the abundant porosity, the as-fabricated Co@N-CNTs@rGO composites exhibit excellent electrocatalytic hydrogen evolution reaction (HER) activity. As demonstrated in electrochemical measurements, the composites can achieve 10 mA cm-2 at low overpotential with only 108 and 87 mV in 1 m KOH and 0.5 m H2 SO4 , respectively, much better than most of the reported Co-based electrocatalysts over a wide pH range. More importantly, the synthetic strategy is versatile and can be extended to prepare other binary or even ternary TMs@N-CNTs@rGO (e.g., Co-Fe@N-CNTs@rGO and Co-Ni-Cu@N-CNTs@rGO). The strategy developed here may open a new avenue toward the development of nonprecious high-performance HER catalysts.

Seeded growth of single-crystal two-dimensional covalent organic frameworks

Abstract: Polymerization of monomers into periodic two-dimensional networks provides structurally precise, layered macromolecular sheets that exhibit desirable mechanical, optoelectronic, and molecular transport properties. Two-dimensional covalent organic frameworks (2D COFs) offer broad monomer scope but are generally isolated as powders comprising aggregated nanometer-scale crystallites. We found that 2D COF formation could be controlled using a two-step procedure in which monomers are added slowly to preformed nanoparticle seeds. The resulting 2D COFs are isolated as single-crystalline, micrometer-sized particles. Transient absorption spectroscopy of the dispersed COF nanoparticles revealed improvement in signal quality by two to three orders of magnitude relative to polycrystalline powder samples, and suggests exciton diffusion over longer length scales than those obtained through previous approaches. These findings should enable a broad exploration of synthetic 2D polymer structures and properties.

One-Pot Synthesis of Highly Stable CsPbBr3@SiO2 Core–Shell Nanoparticles

Abstract: The practical applications of CsPbX3 nanocrystals (NCs) have been limited by their poor stability. Although much effort has been devoted to making core–shell nanostructures to enhance the stability of CsPbX3 NCs, it is still very difficult to coat CsPbX3 NCs with another material on a single-particle level. In this work, we report a facile one-pot approach to synthesize CsPbBr3@SiO2 core–shell nanoparticles (NPs), in which each core–shell NP has only one CsPbBr3 NC. The formation process has been carefully monitored. It has been found that the formation rates, determined by reaction temperature, precursor species, pH value, etc., of both CsPbBr3 and SiO2 are critical for the successful preparation of core–shell NPs. Thanks to the protection of SiO2 shell, the product shows much higher long-term stability in humid air and enhanced stability against ultrasonication treatment in water than that of naked CsPbBr3 NCs. This work not only provides a robust method for the preparation of core–shell nanostructures ...

Surface Chemistry in Cobalt Phosphide-Stabilized Lithium–Sulfur Batteries

Abstract: Chemistry at the cathode/electrolyte interface plays an important role for lithium–sulfur batteries in which stable cycling of the sulfur cathode requires confinement of the lithium polysulfide intermediates and their fast electrochemical conversion on the electrode surface. While many materials have been found to be effective for confining polysulfides, the underlying chemical interactions remain poorly understood. We report a new and general lithium polysulfide-binding mechanism enabled by surface oxidation layers of transition-metal phosphide and chalcogenide materials. We for the first time find that CoP nanoparticles strongly adsorb polysulfides because their natural oxidation (forming Co–O–P-like species) activates the surface Co sites for binding polysulfides via strong Co–S bonding. With a surface oxidation layer capable of confining polysulfides and an inner core suitable for conducting electrons, the CoP nanoparticles are thus a desirable candidate for stabilizing and improving the performance o...

Antimicrobial Activity of Metal and Metal‐Oxide Based Nanoparticles

Abstract: With an increase in antibiotic resistance, a growing interest in developing new antimicrobial agents has gained popularity. Metal‐ and metal‐oxide‐based nanoparticles, surface‐to‐volume is able to distinguish bacterial cells from mammalian cells and can provide long‐term antibacterial and biofilm prevention. These nanoparticles elicit bactericidal properties through the generation of reactive oxygen species (ROS) that are able to target physical structures, metabolic pathways, and DNA synthesis of prokaryotic cells leading to cell death. In this progress report, a critical analysis of current literature on antimicrobial effect of metal and metal‐oxide nanoparticles are examined. Specifically, the antimicrobial mechanisms of metal ions and metal nanomaterials are discussed. Antimicrobial efficiency of nanomaterials is correlated with the structural and physical properties, such as size, shape, and/or zeta potential. A critical analysis of the current state of metal and metal‐oxide nanomaterial research advances our understanding to overcome antibiotic resistance and provide alternatives to combat bacterial infections. Finally, emerging approaches to identify and minimize metallic poisoning, specifically for biomedical applications, are examined.

Embedding MnO@Mn3 O4 Nanoparticles in an N-Doped-Carbon Framework Derived from Mn-Organic Clusters for Efficient Lithium Storage.

Abstract: The first synthesis of MnO@Mn3 O4 nanoparticles embedded in an N-doped porous carbon framework (MnO@Mn3 O4 /NPCF) through pyrolysis of mixed-valent Mn8 clusters is reported. The unique features of MnO@Mn3 O4 /NPCF are derived from the distinct interfacial structure of the Mn8 clusters, implying a new methodological strategy for hybrids. The characteristics of MnO@Mn3 O4 are determined by conducting high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy loss spectroscopy (EELS) valence-state analyses. Due to the combined advantages of MnO@Mn3 O4 , the uniform distribution, and the NPCF, MnO@Mn3 O4 /NPCF displays unprecedented lithium-storage performance (1500 mA h g-1 at 0.2 A g-1 over 270 cycles). Quantitative analysis reveals that capacitance and diffusion mechanisms account for Li+ storage, wherein the former dominates. First-principles calculations highlight the strong affiliation of MnO@Mn3 O4 and the NPCF, which favor structural stability. Meanwhile, defects of the NPCF decrease the diffusion energy barrier, thus enhancing the Li+ pseudocapacitive process, reversible capacity, and long cycling performance. This work presents a new methodology to construct composites for energy storage and conversion.

Methods for Synthesis of Nanoparticles and Fabrication of Nanocomposites

Abstract: This chapter deals with the synthesis of nanoparticles, and the synthesis and fabrication of nanocomposites—metal, ceramic, and polymeric. Various methods used to synthesize nanoparticles, such as coprecipitation, hydrothermal synthesis, inert gas condensation, ion sputtering scattering, microemulsion, microwave, pulse laser ablation, sol-gel, sonochemical, spark discharge, template synthesis, and biological synthesis, will be described. The synthesis of metal nanocomposites includes spray pyrolysis, liquid infiltration, the rapid solidification process, high-energy ball milling, chemical vapor deposition, physical vapor deposition, and chemical processes—sol-gel and colloidal. The synthesis of ceramic nanocomposites includes the powder process, polymer precursor process, and the sol-gel process. Finally, the fabrication of polymer nanocomposites includes intercalation, in situ intercalative polymerization, melt intercalation, template synthesis, mixing, in situ polymerization, and the sol-gel process. A summary with perspective concludes the chapter.

Polydopamine Nanoparticles as Efficient Scavengers for Reactive Oxygen Species in Periodontal Disease

Abstract: Antioxidative therapy has been considered an efficient strategy for the treatment of a series of excessive reactive oxygen species (ROS)-triggered diseases, including oxidative-stress-induced periodontal disease. However, current natural enzymes and nanozymes often show their high specificity toward given ROS and have insufficient antioxidative effects against multiple ROS generated in the diseases process. Meanwhile, multienzyme-based antioxidant defense systems are usually confined by the complicated synthesis as well as potential unwanted residue and toxicity. Various supports are highly needed to immobilize natural enzymes and antioxidants during the biorelated usages due to their low operational stability and difficulty of reuse. To overcome these limitations, we develop a high-performance platform by using biodegradable polydopamine nanoparticles (PDA NPs) as smart ROS scavengers in oxidative stress-induced periodontal disease. Although PDA-based materials are well-known to eliminate ROS both in vit...

Superhierarchical Cobalt-Embedded Nitrogen-Doped Porous Carbon Nanosheets as Two-in-One Hosts for High-Performance Lithium–Sulfur Batteries

Abstract: Lithium-sulfur (Li-S) batteries, based on the redox reaction between elemental sulfur and lithium metal, have attracted great interest because of their inherently high theoretical energy density. However, the severe polysulfide shuttle effect and sluggish reaction kinetics in sulfur cathodes, as well as dendrite growth in lithium-metal anodes are great obstacles for their practical application. Herein, a two-in-one approach with superhierarchical cobalt-embedded nitrogen-doped porous carbon nanosheets (Co/N-PCNSs) as stable hosts for both elemental sulfur and metallic lithium to improve their performance simultaneously is reported. Experimental and theoretical results reveal that stable Co nanoparticles, elaborately encapsulated by N-doped graphitic carbon, can work synergistically with N heteroatoms to reserve the soluble polysulfides and promote the redox reaction kinetics of sulfur cathodes. Moreover, the high-surface-area pore structure and the Co-enhanced lithiophilic N heteroatoms in Co/N-PCNSs can regulate metallic lithium plating and successfully suppress lithium dendrite growth in the anodes. As a result, a full lithium-sulfur cell constructed with Co/N-PCNSs as two-in-one hosts demonstrates excellent capacity retention with stable Coulombic efficiency.

Co(OH)2 Nanoparticle-Encapsulating Conductive Nanowires Array: Room-Temperature Electrochemical Preparation for High-Performance Water Oxidation Electrocatalysis

Abstract: It is highly desired but still remains challenging to design and develop a Co-based nanoparticle-encapsulated conductive nanoarray at room temperature for high-performance water oxidation electrocatalysis. Here, it is reported that room-temperature anodization of a Co(TCNQ)2 (TCNQ = tetracyanoquinodimethane) nanowire array on copper foam at alkaline pH leads to in situ electrochemcial oxidation of TCNQ- into water-insoluable TCNQ nanoarray embedding Co(OH)2 nanoparticles. Such Co(OH)2 -TCNQ/CF shows superior catalytic activity for water oxidation and demands only a low overpotential of 276 mV to drive a geometrical current density of 25 mA cm-2 in 1.0 m KOH. Notably, it also demonstrates strong long-term electrochemical durability with its activity being retrained for at least 25 h, a high turnover frequency of 0.97 s-1 at an overpotential of 450 mV and 100% Faradic efficiency. This study provides an exciting new method for the rational design and development of a conductive TCNQ-based nanoarray as an interesting 3D material for advanced electrochemical applications.

In Situ Thermal Atomization To Convert Supported Nickel Nanoparticles into Surface‐Bound Nickel Single‐Atom Catalysts

Abstract: The arrangement of the active sites on the surface of a catalysts can reduce the problem of mass transfer and enhance the atom economy. Herein, supported Ni metal nanoparticles can be transformed to thermal stable Ni single atoms, mostly located on the surface of the support. Assisted by N-doped carbon with abundant defects, this synthetic process not only transform the nanoparticles to single atoms, but also creates numerous pores to facilitate the contact of dissolved CO2 and single Ni sites. The proposed mechanism is that the Ni nanoparticles could break surface C-C bonds drill into the carbon matrix, leaving pores on the surface. When Ni nanoparticles are exposed to N-doped carbon, the strong coordination splits Ni atoms from Ni NPs. The Ni atoms are stabilized within the surface of carbon substrate. The continuous loss of atomic Ni species from the NPs would finally result in atomization of Ni NPs. CO2 electroreduction testing shows that the surface enriched with Ni single atoms delivers better performance than supported Ni NPs and other similar catalysts.

Effects of Size and Aggregation/Agglomeration of Nanoparticles on the Interfacial/Interphase Properties and Tensile Strength of Polymer Nanocomposites

Abstract: In this study, several simple equations are suggested to investigate the effects of size and density on the number, surface area, stiffening efficiency, and specific surface area of nanoparticles in polymer nanocomposites. In addition, the roles of nanoparticle size and interphase thickness in the interfacial/interphase properties and tensile strength of nanocomposites are explained by various equations. The aggregates/agglomerates of nanoparticles are also assumed as large particles in nanocomposites, and their influences on the nanoparticle characteristics, interface/interphase properties, and tensile strength are discussed. The small size advantageously affects the number, surface area, stiffening efficiency, and specific surface area of nanoparticles. Only 2 g of isolated and well-dispersed nanoparticles with radius of 10 nm (R = 10 nm) and density of 2 g/cm3 produce the significant interfacial area of 250 m2 with polymer matrix. Moreover, only a thick interphase cannot produce high interfacial/interphase parameters and significant mechanical properties in nanocomposites because the filler size and aggregates/agglomerates also control these terms. It is found that a thick interphase (t = 25 nm) surrounding the big nanoparticles (R = 50 nm) only improves the B interphase parameter to about 4, while B = 13 is obtained by the smallest nanoparticles and the thickest interphase.

Nanosized Metal Phosphides Embedded in Nitrogen‐Doped Porous Carbon Nanofibers for Enhanced Hydrogen Evolution at All pH Values

Abstract: Transition-metal phosphides (TMPs) have emerged as promising catalyst candidates for the hydrogen evolution reaction (HER). Although numerous methods have been investigated to obtain TMPs, most rely on traditional synthetic methods that produce materials that are inherently deficient with respect to electrical conductivity. An electrospinning-based reduction approach is presented, which generates nickel phosphide nanoparticles in N-doped porous carbon nanofibers (Ni2 P@NPCNFs) in situ. Ni2 P nanoparticles are protected from irreversible fusion and aggregation in subsequent high-temperature pyrolysis. The resistivity of Ni2 P@NPCNFs (5.34 Ω cm) is greatly decreased by 104 times compared to Ni2 P (>104 Ω cm) because N-doped carbon NFs are incorporated. As an electrocatalyst for HER, Ni2 P@NPCNFs reveal remarkable performance compared to other previously reported catalysts in acidic media. Additionally, it offers excellent catalytic ability and durability in both neutral and basic media. Encouraged by the excellent electrocatalytic performance of Ni2 P@NPCNFs, a series of pea-like Mx P@NPCNFs, including Fe2 P@NPCNFs, Co2 P@NPCNFs, and Cu3 P@NPCNFs, were synthesized by the same method. Detailed characterization suggests that the newly developed method could render combinations of ultrafine metal phosphides with porous carbon accessible; thereby, extending opportunities in electrocatalytic applications.

Fabrication, Characterization and Cytotoxicity of Spherical-Shaped Conjugated Gold-Cockle Shell Derived Calcium Carbonate Nanoparticles for Biomedical Applications

Abstract: The evolution of nanomaterial in science has brought about a growing increase in nanotechnology, biomedicine, and engineering fields. This study was aimed at fabrication and characterization of conjugated gold-cockle shell-derived calcium carbonate nanoparticles (Au-CSCaCO3NPs) for biomedical application. The synthetic technique employed used gold nanoparticle citrate reduction method and a simple precipitation method coupled with mechanical use of a Programmable roller-ball mill. The synthesized conjugated nanomaterial was characterized for its physicochemical properties using transmission electron microscope (TEM), field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). However, the intricacy of cellular mechanisms can prove challenging for nanomaterial like Au-CSCaCO3NPs and thus, the need for cytotoxicity assessment. The obtained spherical-shaped nanoparticles (light-green purplish) have an average diameter size of 35 ± 16 nm, high carbon and oxygen composition. The conjugated nanomaterial, also possesses a unique spectra for aragonite polymorph and carboxylic bond significantly supporting interactions between conjugated nanoparticles. The negative surface charge and spectra absorbance highlighted their stability. The resultant spherical shaped conjugated Au-CSCaCO3NPs could be a great nanomaterial for biomedical applications.

Eco-friendly preparation of zinc oxide nanoparticles using Tabernaemontana divaricata and its photocatalytic and antimicrobial activity.

Abstract: The present work reports the green synthesis of Zinc Oxide Nanoparticles (ZnO NPs) using aqueous Tabernaemontana divaricata green leaf extract. ZnO NPs have been characterized by X-ray diffraction (XRD), Ultra Violet–Visible (UV–Vis) studies, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Fourier Transform–Infra Red (FT–IR) analysis. XRD pattern analysis confirms the presence of pure hexagonal wurtzite crystalline structure of ZnO. The TEM images reveal the formation of spherical shape ZnO NPs with the sizes ranging from 20 to 50 nm. The FT–IR analysis suggests that the obtained ZnO NPs have been stabilized through the interactions of steroids, terpenoids, flavonoids, phenyl propanoids, phenolic acids and enzymes present in the leaf extract. Mechanism for the formation of ZnO NPs using Tabernaemontana divaricata as bioactive compound is proposed. As prepared ZnO NPs reveals antibacterial activity against three bacterial strains, Salmonella paratyphi, Escherichia coli and Staphylococcus aureus. The ZnO NPs shows higher antibacterial activity against S. aureus and E. coli and lesser antibacterial activity against S. paratyphi compared to the standard pharmaceutical formulation. Photocatalytic activity of synthesized ZnO NPs was analyzed for methylene blue (MB) dye degradation with sunlight. Almost complete degradation of dye occurred in 90 min. This nano-ZnO, prepared by eco-friendly method will be much useful for dye removal and bacterial decontamination.

Sinter-resistant metal nanoparticle catalysts achieved by immobilization within zeolite crystals via seed-directed growth

Abstract: Supported metal nanoparticle catalysts are widely used in industry but suffer from deactivation resulting from metal sintering and coke deposition at high reaction temperatures. Here, we show an efficient and general strategy for the preparation of supported metal nanoparticle catalysts with very high resistance to sintering by fixing the metal nanoparticles (platinum, palladium, rhodium and silver) with diameters in the range of industrial catalysts (0.8–3.6 nm) within zeolite crystals (metal@zeolite) by means of a controllable seed-directed growth technique. The resulting materials are sinter resistant at 600–700 °C, and the uniform zeolite micropores allow for the diffusion of reactants enabling contact with the metal nanoparticles. The metal@zeolite catalysts exhibit long reaction lifetimes, outperforming conventional supported metal catalysts and commercial catalysts consisting of metal nanoparticles on the surfaces of solid supports during the catalytic conversion of C1 molecules, including the water-gas shift reaction, CO oxidation, oxidative reforming of methane and CO2 hydrogenation. Supported metal nanoparticles are indispensable catalysts in industry, yet they are often subjected to severe sintering. Now, a general method based on metal immobilization within zeolite is reported for the preparation of highly sinter-resistant catalysts for a broad range of industrially relevant processes.

Ordered Pt3Co Intermetallic Nanoparticles Derived from Metal-Organic Frameworks for Oxygen Reduction.

Abstract: Highly ordered Pt alloy structures are proven effective to improve their catalytic activity and stability for the oxygen reduction reaction (ORR) for proton exchange membrane fuel cells. Here, we report a new approach to preparing ordered Pt3Co intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped metal–organic-framework (MOF)-derived carbon. In particular, the atomically dispersed Co sites, which are originally embedded into MOF-derived carbon, diffuse into Pt nanocrystals and form ordered Pt3Co structures. It is very crucial for the formation of the ordered Pt3Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal Pt3Co nanoparticle catalyst has achieved significantly enhanced activity and stability, exhibiting a half-wave potential up to 0.92 V vs reversible hydrogen electrode (RHE) and only losing 12 mV after 30 000 potential cycling between 0.6 and 1.0 V. The highly ordered intermetal...

Exciton–Plasmon Interaction between AuNPs/Graphene Nanohybrids and CdS Quantum Dots/TiO2 for Photoelectrochemical Aptasensing of Prostate-Specific Antigen

Abstract: A competitive-displacement reaction strategy based on target-induced dissociation of gold nanoparticle coated graphene nanosheet (AuNPs/GN) from CdS quantum dot functionalized mesoporous titanium dioxide (CdS QDs/TiO2) was designed for the sensitive photoelectrochemical (PEC) aptasensing of prostate-specific antigen (PSA) through the exciton–plasmon interaction (EPI) between CdS QDs and AuNPs. To construct such an aptasensing system, capture DNA was initially conjugated covalently onto CdS QDs/TiO2-modified electrode, and then AuNPs/GN-labeled PSA aptamer was bound onto biofunctionalized CdS QDs/TiO2 via hybridization chain reaction of partial bases with capture DNA. Introduction of AuNPs/GN efficiently quenched the photocurrent of CdS QDs/TiO2 thanks to energy transfer. Upon addition of target PSA, the sandwiched aptamer between CdS QDs/TiO2 and AuNPs/GN reacted with the analyte analyte, thus resulting in the dissociation of AuNPs/GN from the CdS QDs/TiO2 to increase the photocurrent. Under optimum condi...