Distribution Of Metal Nanoparticles Research Articles

Bimetallic nickel–cobalt oxide nanoparticle/ electrospun carbon nanofiber composites: Preparation and application for supercapacitor electrode

Designing electrode materials by hybridizing components can enhance the final efficiency of energy storage systems. Herein, we study application of different precursors on the physicochemical and electrochemical behavior of the resulting hybrid electrode materials. Electrodes were prepared by electrospinning followed by heat treatment. There was an optimum ratio nickel/cobalt-based precursors yielding higher uniformity and even distribution of metallic nanoparticles on the surface of electrospun carbon nanofibers (ECNFs). Furthermore, the electrochemical characterizations confirmed the synergistic effect of two transition metal oxides components (bimetallic oxide) with an electrically conductive substrate in the form of hybrid electrode material. Consequently, the optimized hybrid electrode material, i.e., Ni0.25Co0.25Oxide/ECNF, exhibited a specific capacitance of 697.5 F/g with 94% capacitance retention even after 2000 cycles at 10 A/g current density. According to quantitative results, the Ni0.25Co0.25Oxide/ECNFs hybrid electrode material showed superior performance in the negative sweep rates for energy storage applications.

LK-5 glass surface modification by glass blowing method based on microsystem technology

This paper considers the possibility of modifying the surface LK-5 glass by glass blowing methods to solve the problems of creating an atomic clock and ensuring a controlled distribution of metal nanoparticles on its surface. The evolution of the formation of a spherical profile of a glass surface on a hermetically welded cavity in a glass-silicon system was studied experimentally and theoretically. Also, the possibility of modifying the spatial parameters of arrays of nanoparticles distributed on the glass surface has been demonstrated. The obtained experimental and theoretical data demonstrate sufficient convergence.

Iron and copper nanoparticles inside and outside carbon nanotubes: Nanoconfinement, migration, interaction and catalytic performance in Fischer-Tropsch synthesis

Carbon materials have attracted increasing attention as supports for metal catalysts. Iron-containing carbon nanotubes often promoted with copper have found application in Fischer-Tropsch synthesis, which provides an alternative way for conversion of renewable feedstocks to chemicals and fuels. In carbon nanotubes, the active phase can be nanoconfined inside the channels or localized on the outer surface. In most of previous work, the distribution of metal nanoparticles inside or outside carbon nanotubes is considered to be immobile during the catalyst activation or catalytic reaction.In this paper, we uncovered remarkable mobility of both iron and copper species in the bimetallic catalysts between inner carbon nanotube channels and outer surface, which occurs in carbon monoxide and syngas, while almost no migration of iron species proceeds in the monometallic catalysts. This mobility is enhanced by noticeable fragility and defects in carbon nanotubes, which appear on their impregnation with the acid solutions of metal precursors and precursor decomposition. Remarkable mobility of iron and copper species in bimetallic catalysts affects the genesis of iron active sites, and enhances interaction of iron with the promoter. In the bimetallic iron-copper catalysts, the major increase in the activity was attributed to a higher reaction turnover frequency over iron surface sites located in a close proximity with copper.

Photocatalytic dye degradation by graphene oxide doped transition metal catalysts

This study involved the synthesis and characterization of novel graphene oxide (GO) nanostructured materials modified with transition metal elements (Fe, Co, Ni, and Cu) as co-catalyst by using the chemical precipitation method. Microscopy analysis showed the formation and distribution of metal nanoparticles on the GO matrix and the co-existence of doped elements was identified using energy dispersive X-ray (EDX) spectroscopic analysis. The characteristic vibration bands of GO were examined by using Raman analysis. Brunauer-Emmett-Teller (BET) measurements confirmed decrement in the surface area of GO after metal addition. The photoelectrochemical performance and methyl orange (MO) degradation performance was investigated under ultraviolet light irradiation. The photocurrent of GO was significantly improved after the addition of metal nanoparticles. Predominantly, the Co and Ni-modified GO samples showed a high photocurrent generation of 64.9 μA/cm2 and 54.4 μA/cm2 respectively. The photocatalytic studies revealed that the modified GO samples exhibited greater dye degradation efficiency than the pristine GO. Among modified GO samples, Co and Ni-modified GO exhibited a remarkable photodegradation efficiency (84%) and rate constants (k = 13 ×10−3 min−1 & 16 ×10−3 min−1). The results imply that the Co and Ni-modified GO samples are the most efficient photocatalysts for MO dye removal.

Metal organic framework derived iron-nitrogen doped porous carbon support decorated with cobalt and iron as efficient nanocatalyst toward oxygen reduction reaction

Two porous carbon supports as N-doped carbon (NC) and Fe/N-co-doped carbon (Fe-NC), are obtained from ZIF-8 (zeolitic imidazolate framework) and Fe@ZIF-8, respectively, through the pyrolysis process. They are then decorated with transition metals using a modified polyol method to precipitate Fe, Co, and Fe–Co nanoparticles. The as-prepared catalysts are characterized by different physicochemical, morphological, and electrochemical characterization methods. Field emission scanning electron microscopy images show well-defined preserved polyhedron morphology for all prepared catalysts. Transmission electron microscopy images confirm a uniform distribution of metal nanoparticles through the surface of the supports. X-ray photoelectron spectroscopy results illustrate the existence of high content of graphitic and pyridinic nitrogen. Oxygen reduction reaction (ORR) results show the prepared support, which is in-situ doped with iron (Fe-NC), has better ORR performance than NC support. The results also display Co and Fe nanoparticles' coincident precipitation on the supports can improve ORR. This finding indicates both in-situ and ex-situ metal doping can be beneficial for good ORR performance. The optimum catalyst (Fe–Co/Fe-NC) illustrates enhanced ORR activity and stability with onset potential ~0.9VRHE in 0.1 M HClO4. Superior performance is associated with a synergistic effect between small and uniform dispersion of Co and Fe nanoparticles and appropriate nitrogen content.

Quantitative Determination of the Surface Distribution of Supported Metal Nanoparticles: A Laser Ablation–ICP–MS Based Approach

A laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) based method is proposed for the quantitative determination of the spatial distribution of metal nanoparticles (NPs) supported on planar substrates. The surface is sampled using tailored ablation patterns and the data are used to define three-dimensional functions describing the spatial distribution of NPs. The volume integrals of such interpolated surfaces are calibrated to obtain the mass distribution of Ag NPs by correlation with the total mass of metal as determined by metal extraction and ICP–MS analysis. Once this mass calibration is carried out on a sacrificial sample, quantifications can be performed over multiple samples by a simple micro-destructive LA–ICP–MS analysis without requiring the extraction/dissolution of metal NPs. The proposed approach is here tested using a model sample consisting of a low-density polyethylene (LDPE) disk decorated with silver NPs, achieving high spatial resolution over cm2-sized samples and very high sensitivity. The developed method is accordingly a useful analytical tool for applications requiring both the total mass and the spatial distribution of metal NPs to be determined without damaging the sample surface (e.g., composite functional materials and NPs, decorated catalysts or electrodic materials).

Understanding the relationship between particle size and ultrasonic treatment during the synthesis of metal nanoparticles

Ultrasonic treatment is an effective method for size refinement and dispersion of nanomaterials during their synthesis process. However, the quantitative relationship between ultrasonic conditions and particle size in the synthesis of metal nanoparticles has not been fully revealed. In this study, Cu nanoparticles were synthesized via the wet-chemical redox method under ultrasonic treatment, and statistical analysis on the evolution of particle size distribution was carried out. It was found that the particle size decreased exponentially with increasing ultrasonic power. A quantitative model was then proposed to describe the influence of ultrasonic power on the size distribution of metal nanoparticles from the perspective of the competition between the surface energy and the ultrasonic force. A relational expression of Rc∝γ47P-37 was revealed, and it was proved to fit well with the experimental results. Our study provides new experimental basis and theoretical method for understanding the mechanism of ultrasonic-induced size refinement of metal nanoparticles.

Interwrapping Distinct Metal-Organic Frameworks in Dual-MOFs for the Creation of Unique Composite Catalysts.

Incorporating metal nanoparticles (MNPs) inside metal-organic frameworks (MOFs) demonstrates superior catalytic properties in numerous reactions; however, the size and distribution of MNPs could not be well controlled, resulting in low product selectivity in catalysis by undergoing different catalytic reaction pathways. We report herein a facile strategy for integrating lattice-mismatched MOFs together to fabricate homogeneously distributed “dual-MOFs,” which are the ideal precursors for the preparation of MNPs@MOFs with unique catalytic properties. As a proof of concept, we successfully synthesize a dual-MOF HKUST-1/ZIF-8 for in situ creation of redox-active Cu NPs inside hierarchical porous ZIF-8 under controlled pyrolytic conditions. Combining the advantages of size-tunable Cu NPs in the molecular sieving matrix of ZIF-8, Cu@ZIF-8 demonstrates high activity and selectivity for transformation of alkynes into alkenes without overhydrogenation, which surpasses most of the catalysts in the literature. Therefore, this work paves a new pathway for developing highly efficient and selective heterogeneous catalysts to produce highly value-added chemicals.

Assessment of metallic nanoparticles as radioenhancers in gastric cancer therapy by Geant4 simulation and local effect model

Gastric cancer ranks as one of the most common and poor prognosis human malignancies. We investigated the radioenhancer effects of gold, silver, platinum, bismuth, iron oxide, titanium oxide and germanium nanoparticles on simulated gastric adenocarcinoma cells, irradiated with 6 MV X-rays in presence of 0.05 µM, 0.25 µM and 0.5 µM homogeneous distributed metal nanoparticles throughout the cell, including the nucleus, cytoplasm and extracellular matrix using Geant4 Monte Carlo simulation along with LEM radiobiological model. The survival reduction coefficient was obtained 0.5 for light nanoparticles including 0.5 μM titanium oxide, iron oxide and germanium and also 0.3–0.1 for heavy nanoparticles including 0.5 μM gold, silver, bismuth and platinum. Nanoparticle-mediated Enhancement Ratio for 0.5 μM internuclear Gold, Silver, Bismuth, Germanium, Platinum, Iron oxide and Titanium oxide nanoparticles was calculated to 0.10, 0.27, 0.26, 0.47, 0.09, 0.50, and 0.58, respectively. Radiosensitization by NPs may enhance therapeutic efficacy of gastric adenocarcinoma.

Size-controlled in situ synthesis of metal–polymer nanocomposite films using a CO2 laser

In situ synthesis of metal–polymer nanocomposite films by irradiating a CO2 laser for several seconds is a new alternative to fabricate metal–polymer nanocomposite films. The main features of this method are that the number density of the synthesized metal nanoparticles is very high so that the optical density easily exceeds 0.5 ~ 1.5 for the film thickness of ~ 200 nm, and owing to the short fabrication time and the use of non-focused laser beam, large-scale processing is possible. For this technique to be applicable for a variety of purposes, an important question is how and how much we can control the film properties. In this work, we demonstrate that the size and size distribution of metallic nanoparticles in the synthesized nanocomposite films can be well controlled by the choice of the laser power and irradiation time as well as the concentrations of nanoparticle precursor. Properties of the synthesized films can be roughly understood by considering the diffusion of metallic ions, atoms, and nanoparticles in the polymer film under the elevated temperature induced by the CO2 laser.

Metal-Organic Powder Thermochemical Solid-Vapor Architectonics toward Gradient Hybrid Monolith with Combined Structure-Function Features

The conversion of inorganic powders or metal powders into gradient components is typically achieved with the help of a non-uniform electric or pressure field. However, the current technologies are ineffective in converting powder into gradient-structured hybrid components with combined structure-function features because of the lack of a non-uniform field to control evolution of the structures. The present work addresses this challenge by taking advantage of uniformly distributed metal nanoparticles and non-uniformly distributed reactive gases generated during thermopyrolysis of metal-organic powder to generate gradient metal-carbon monolith via combined chemical vapor deposition and solid-state welding. The obtained monolith shows good mechanical strength and high catalytic activity, allowing it to be used as a working electrode for a seawater battery. This method connecting gas-solid-state synthesis together with processing may lead to other gradient hybrid monoliths in the future.A gradient carbon-metal hybrid component can be manufactured by thermopyrolysis of metal-organic framework powder. The non-uniformly distributed carbonaceous vapor and uniformly dispersed Co nanoparticles are essential for generating the gradient carbon monolith. This monolith exhibits good mechanical strength and high catalytic activity, and thus can be directly utilized as an electrode for a Mg/HO battery to generate electricity from seawater. The assembled battery shows power density comparable with that of a battery with Pt as the electrode.Direct manufacturing from powder to final component is of great significance for industry. However, it remains a challenge to develop a one-pot “powder-to-product” strategy to produce gradient hybrid components with combined structural and functional advantages. In this work, we report metal-organic powder thermochemical solid-vapor architectonics to direct zeolitic imidazolate framework powder into gradient cobalt/carbon monolith by utilizing in situ generated reactive vapor (non-uniform distribution) and Co nanoparticles (uniformly distributed) to achieve a combination of chemical vapor deposition/growth and solid-state welding. The gradient hybrid monolith possesses good mechanical stability, allowing it to be directly used as a freestanding working electrode for hydrogen evolution reaction in a seawater battery. This catalyst shows a low overpotential of 84 mV at a current density of 10 mA cm. Furthermore, a stable power generation of over 168 h in seawater has also been realized.

Efficient Noble-Metal-Free Catalysts Supported by Three-Dimensional Ordered Hierarchical Porous Carbon.

Development of heterogeneous catalysts has attracted increasing attention, owing to their remarkable catalytic performance and recyclability. Herein, we report well-developed heterogeneous catalysts with a three-dimensional ordered hierarchical structure, constructed from nickel or cobalt nanoparticles embedded in porous carbon. The obtained catalysts were fully characterized by several techniques. On account of the uniform distribution of metal nanoparticles in the porous carbon matrix and large diffusion channels that allow for effective mass transport, the catalysts exhibited superior catalytic performance for styrene epoxidation reaction. In particular, the catalysts showed good catalytic activity, high selectivity and excellent recyclability toward the styrene epoxidation. Thus, this facile approach developed allows for fabricating advanced heterogeneous catalysts with high catalytic activities for useful practical applications.

Structured Light by Rotating Au Nanoparticles in a Dynamic Distribution

Herein is reported the potential impact of the optical Kerr effect exhibited by rotating plasmonic nanoparticles on the generation of structured light. The third-order nonlinear optical properties exhibited by a round continuously variable distribution of metal nanoparticles incorporated in a dielectric substrate were analysed. The nanosystems were studied by using the finite difference method and TiO2-supported Au nanoparticles explored by a vectorial two-wave mixing technique. Attractive applications for developing quantum functions assisted by mechano-optical effects can be considered.

Porous carbon supported PtPd alloy nanoparticles derived from N-heterocyclic carbene bimetal complex as efficient bifunctional electrocatalysts

Pyrolysis of metal complexes has been recently reported as a facile and economic method for the design and large-scale synthesis of carbon supported metal materials. In particular, N-heterocyclic carbenes (NHCs) possess obvious advantages such as the strong binding to many metals, high stability and synthetic accessibility as compared to other ligands. In this work, the bimetal-NHC complex is pyrolyzed for the first time to synthesize the carbon supported PtPd alloy electrocatalyst (PtPd/CKN) for oxygen reduction reaction and hydrogen evolution reaction. The coordination of metal with NHC ligands strengthened the metal-support interactions, resulting in the stabilization of metal nanoparticles against agglomerations under high-temperature synthesis and catalytic reaction conditions. As a result, the optimal Pt2Pd3/CKN material possesses the uniform distribution of metal nanoparticles with the size of 2–4 nm and exhibits better electrocatalytic activity than commercial Pt/C. More importantly, the strong metal-support interaction effectively enhanced the durability of the alloy electrocatalyst with only 3 mV of negative shift after 10,000 cycles.

Selective transformation of ethanol to acetaldehyde catalyzed by Au/h-BN interface prepared on Rh(111) surface

Controlled shape and size distribution of metal nanoparticles for surface catalytic reactions are important. Through deposition onto the periodic surface of h-BN we can adjust these parameters of gold thereby we are able to influence the catalytic activity of the nanoparticles. In this study we investigated the decomposition of ethanol on gold nanoparticles supported on h-BN/Rh(111). High-resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD) methods have been used on the experimental side. Ethanol showed enhanced stability on Au/h-BN/Rh(111) system. The stabilization effect increases with gold coverage and saturates before gold reaches a continuous adlayer. High selectivity was observed towards “CO free” hydrogen, a small part of ethanol dissociated to hydrogen and acetaldehyde without further decomposition. Density functional theory (DFT) calculations delivered important information about the adsorption characteristics of ethanol and hydrogen on model Au/h-BN/Rh(111). The importance of low-coordinated negatively charged Au atoms is confirmed by DFT results.

PdAg Nanoparticles within Core-Shell Structured Zeolitic Imidazolate Framework as a Dual Catalyst for Formic Acid-based Hydrogen Storage/Production

Formic acid (FA; HCOOH) is one of the most promising candidates for the storage of hydrogen (H2). Herein, we report a H2 storage/production system based on the hydrogenation of CO2 and dehydrogenation of FA, using a nanostructured heterogeneous catalyst. Pd1Ag2 nanoparticles with an average size of 2.8 nm were encapsulated within a zeolitic imidazolate framework (ZIF-8) having a core-shell structure (ZIF-8@Pd1Ag2@ZIF-8). This composite displayed high activity and stability during both the hydrogenation of CO2 to produce FA and the dehydrogenation of FA into H2 and CO2. This improved performance is attributed to the use of ultrafine Pd1Ag2 nanoparticles as well as the spatial regulation of the nanoparticles within the reaction field. This study suggests a new strategy for controlling the spatial distribution of metal nanoparticles within MOFs so as to fine-tune the catalytic activity and selectivity of ZIF-8@metal nanoparticles@ZIF-8 catalysts.

Investigation of the Effects of Different Experimental Conditions on the Final Product of a Chemical Reduction Method Used to Fabricate Silver Nanoparticles

Metallic nanoparticles are a focus of interest for a diversity of scientific fields such as medical, engineering and agricultural fields. For such fields, metallic nanoparticles with controlled sizes are pursued for proper utilization in their prospect applications like radiation detection and drug delivery. In this paper, a parametric study was carried out to investigate the effect of different experimental conditions on the size distribution of metallic nanoparticles fabricated by a chemical reduction method. The study entailed modification of four experimental conditions: concentration of the metal precursor (AgNO3), concentration of the reducing agent (NaBH4), dropping rate of the reducing agent to the precursor solution and reaction temperature. A noticeable increase in the average size was observed with increasing the concentration of the reducing agent, decreasing the dropping rate and increasing the reaction temperature. Other changes were found to have negligible effects. Decreasing both the reaction temperature and the concentration of the reducing agent and increasing the dropping rate led to enhanced monodispersity of the size distribution. Changing the concentration of the metal precursor, on the other hand, had a negligible effect of dispersity. Finally, more particle aggregation was observed for both slow dropping rates and high reaction temperatures.

Au Nanoparticle-TiO2 Hybrids for Efficient Electron Transport Layer in Perovskite Solar Cells

The novel synthesis of Au nanoparticle-TiO2 composites has been demonstrated to achieve uniform distribution of metal nanoparticles in the matrix. The resulting composites with Au nanoparticles hol...

Distribution of metal nanoparticles in a plasma polymer matrix according to the structure of the polymer and the nature of the metal

The amount and distribution of metal nanoparticles in a plasma polymer matrix are studied according to the chemical structure of the polymer and the nature of the metal. The structure of the polymer (polyallylalcohol) is modified by varying the plasma parameters such as polymerization time, input power and discharge time. This study, done with silver, shows that when the polymer contains a lot of functional groups (here hydroxyl ones) with a rough surface, a high amount of silver, homogeneously distributed is inserted into the polymer. Moreover, three metals are studied: Ag, Cu and Sn. A higher quantity of silver and tin ions is inserted into the matrix compared to copper. Finally, two routes for the incorporation of silver nanoparticles are studied where the impregnation with the metallic salt and its reduction are done either in two stages or in one step with a single solution containing both the metallic salt and the reducing agent. The first method allows obtaining a higher amount of loaded silver with a homogeneous dispersion in the matrix.

Growth Kinetics of Individual Co Particles Ex-solved on SrTi0.75Co0.25O3-δ Polycrystalline Perovskite Thin Films.

A precise control of the size, density, and distribution of metal nanoparticles dispersed on functional oxide supports is critical for promoting catalytic activity and stability in renewable energy and catalysis devices. Here, we measure the growth kinetics of individual Co particles ex-solved on SrTi0.75Co0.25O3-δ polycrystalline thin films under a high vacuum, and at various temperatures and grain sizes using in situ transmission electron microscopy. The ex-solution preferentially occurs at grain boundaries and corners which appear essential for controlling particle density and distribution, and enabling low temperature ex-solution. The particle reaches a saturated size after a few minutes, and the size depends on temperature. Quantitative measurements with a kinetic model determine the rate limiting step, vacancy formation enthalpy, ex-solution enthalpy, and activation energy for particle growth. The ex-solved particles are tightly socketed, preventing interactions among them over 800 °C. Furthermore, we obtain the first direct clarification of the active reaction site for CO oxidation-the Co-oxide interface, agreeing well with density functional theory calculations.