Dendritic Pt–Cu nanoparticles were synthesized by a facile one-step method with the help of surfactant Brij58 at room temperature, and we also studied the effects of different Pt–Cu ratios on the morphology and size of nanoparticles. In addition, we further tuned the morphology of the Pt–Cu nanostructures by introducing bromide ions, eventually leading to the appearance of some tripod-like structures. Compared with dendritic Pt–Cu and commercial Pt black, these tripod-like Pt–Cu nanostructures exhibited higher electrocatalytic activity and CO tolerance for catalyzing methanol oxidation.
Voltammetric dealloying is employed here to investigate the correlations between catalytic performance and surface composition and structure, taking ethanol oxidation reaction (EOR) on Pd-Cu alloy surface as a case study. First, home-made PdCu/C with a mean particle size of ca. 3.11?±?0.6 nm is dealloyed by repetitive potential cycling in 0.5 M H2SO4. With dealloying cycles rising, the Cu component is gradually leached out and the corresponding Pd/Cu atomic ratio gradually increases from ca. 2.1 to 4.0; meanwhile, SEM images display that Pd-rich porous shell is formed due to dealloying-induced surface structural rearrangement, being verified by the appearance of ear-like peaks at ??0.015 V (vs. SCE) in CVs collected in 0.5 M H2SO4; furthermore, XPS spectra indicate that core-level binding energies of Pd 3d5/2 first positively shift to 336.1 eV and then oppositively move down to 334.9 eV, indicating that the d-band center of Pd composition is modulated by the dealloying treatment. Moreover, the voltammetric peak current densities for EOR follow the order of PdCu/C-DA15?>?as-prepared PdCu/C ??>?PdCu/C-DA30 ? commercial Pd/C ? PdCu/C-DA75, due to the modest downshift of Pd d-band center resulted by charge transfer and surface atomic rearrangement. In addition, the EOR durability gradually decays with the continuous loss of Cu, indicating that electro-oxidation of surface species also follows the so-called bi-functional mechanism. This work might provide some new insights into the catalysis enhancement by tuning the surface/interfacial structure of catalysts.
Graphical abstract The voltammetric peak current densities for ethanol oxidation on home-made PdCu/C catalysts gradually decrease with the dealloying cycles rising, suggesting that the surface voltammetric dealloyment could effectively modulate the surface composition and structure, so as to tune the catalytic performance.
Water dispersible boron nanoparticles have great potential as materials for boron neutron capture therapy of cancer and magnetic resonance imaging, if they are prepared on a large scale with uniform size and shape and hydrophilic modifiable surface. We report the first method to prepare spherical, monodisperse, water dispersible boron core silica shell nanoparticles (B@SiO2 NPs) suitable for aforementioned biomedical applications. In this method, 40 nm elemental boron nanoparticles, easily prepared by mechanical milling and carrying 10-undecenoic acid surface ligands, are hydrosilylated using triethoxysilane, followed by base-catalyzed hydrolysis of tetraethoxysilane, which forms a 10-nm silica shell around the boron core. This simple two-step process converts irregularly shaped hydrophobic boron particles into the spherically shaped uniform nanoparticles. The B@SiO2 NPs are dispersible in water and the silica shell surface can be modified with primary amines that allow for the attachment of a fluorophore and, potentially, of targeting moieties.
Molecular dynamics (MD) simulations were performed to investigate the role of core volume fraction and number of fusing nanoparticles (NPs) on the melting and solidification of Cu/Al and Ti/Al bimetallic core/shell NPs during a superfast heating and slow cooling process, roughly mimicking the conditions of selective laser melting (SLM). One recent trend in the SLM process is the rapid prototyping of nanoscopically heterogeneous alloys, wherein the precious core metal maintains its particulate nature in the final manufactured part. With this potential application in focus, the current work reveals the fundamental role of the interface in the two-stage melting of the core/shell alloy NPs. For a two-NP system, the melting zone gets broader as the core volume fraction increases. This effect is more pronounced for the Ti/Al system than the Cu/Al system because of a larger difference between the melting temperatures of the shell and core metals in the former than the latter. In a larger six-NP system (more nanoscopically heterogeneous), the melting and solidification temperatures of the shell Al roughly coincide, irrespective of the heating or cooling rate, implying that in the SLM process, the part manufacturing time can be reduced due to solidification taking place at higher temperatures. The nanostructure evolution during the cooling of six-NP systems is further investigated.
A novel nano-size MnxOy/clinoptilolite catalyst of high activity for propane-SCR reaction of NOx at low temperatures has been synthesized by a hydrothermal method in a temperature range of 80–180 °C. The optimum synthesis temperature resulting in maximum NOx conversion was 150 °C. An optimum manganese oxide loading of 0.2 wt.% results in the best catalytic behavior (71% NOx conversion). All catalysts exhibited an optimal propane-SCR reaction temperature of 200 °C. The optimum catalyst produces no detectable CO (GHSV 27,000 h) at 200 °C. Manganese in the optimum catalyst exists as Mn2+ (37.8%), Mn3+ (14.2%), and Mn4+ (48%).
Graphical abstract Flake-like manganese oxide nanostructures (indicated by an arrow in the TEM picture) next to the clinoptilolite zeolite sheet-like crystals result in a promising low-temperature propane-selective catalytic reduction of NOx.
Novel feather duster-like nickel sulfide (NiS) @ molybdenum sulfide (MoS2) with hierarchical array structure is synthesized via a simple one-step hydrothermal method, in which a major structure of rod-like NiS in the center and a secondary structure of MoS2 nanosheets with a thickness of about 15–55 nm on the surface. The feather duster-like NiS@MoS2 is employed as the counter electrode (CE) material for the dye-sensitized solar cell (DSSC), which exhibits superior electrocatalytic activity due to its feather duster-like hierarchical array structure can not only support the fast electron transfer and electrolyte diffusion channels, but also can provide high specific surface area (238.19 m2 g?1) with abundant active catalytic sites and large electron injection efficiency from CE to electrolyte. The DSSC based on the NiS@MoS2 CE achieves a competitive photoelectric conversion efficiency of 8.58%, which is higher than that of the NiS (7.13%), MoS2 (7.33%), and Pt (8.16%) CEs under the same conditions.
Graphical abstract Novel feather duster-like NiS@MoS2 hierarchical structure array with superior electrocatalytic activity was fabricated by a simple one-step hydrothermal method.
We have investigated numerically the plasmonic effect on a two-dimensional periodic array of metallic nanostructures. The unit cell of the array has an Ag nanosphere and nanorod pair formed in a single structure. Three-dimensional finite element method is used for the study on the sensing performance within the optical spectra. The study takes into account the influences of the structural and material parameters, the rotational angle of the metal nanostructure, the number of metal nanostructure per unit cell, and the localized surface plasmon resonances. The proposed nanostructures function as a refractive index sensor with a sensitivity of 400 nm/RIU (RIU is the refractive index unit), showing the characteristics of low transmittance (T?=?3.90%), high absorptance (A?=?94.5%), and near-zero reflectance (R?=?0.15%), could be achieved by a triangular arrangement of nanostructures within a unit cell. We also show how the tailoring of the structural parameters relates to the specific sensing schematics of the sensor.
Graphical abstractx-y sectional plane of electric field intensity, electric force lines (pink lines), energy flows (green arrows) and surface charge density of type 2, corresponding to the surrounding testing medium of (a) n=1.00 and (b) n=1.33 around the PMNSs.
Ligand-free palladium nanoparticles supported on multi-walled carbon nanotubes (Pd/MWCNT) were prepared by the supercritical carbon dioxide (scCO2) deposition method using a novel scCO2-soluble Pd organometallic complex as a precursor. The precursor with the perfluoroalkyl chain group was synthesized and identified by microanalytic methods. The deposition was carried out at the temperature of 363.15 K and pressure of 27.6 MPa CO2. The prepared metallic nanoparticles were obtained with an average size of 2 nm. Pd/MWCNT was utilized as a heterogeneous catalyst in Suzuki cross-coupling reaction. The nanocatalyst was found very effective in Suzuki reaction and it could also be recovered easily from the reaction media and reused over several cycles without significant loss of catalytic activity under mild conditions.
Graphical Abstract Pd/MWCNT was prepared by the scCO2 deposition method using a new synthesized perfluroalkylated vic-dioxime Pd complex as the precursor. The prepared nanoparticle was very effective as catalyst and reusable for Suzuki cross coupling reaction under mild conditions.
Ternary composites of BiFeO3/graphene nanoplatelet (GNP)/epoxy composites were synthesized and its electromagnetic and microwave absorbing properties were studied; the main absorbing mechanism was illustrated. The phase, microstructure, and microwave absorbing properties were characterized by X-ray diffraction, scanning electron microscope, and vector network analyzer. The results indicated that the BiFeO3 was successfully synthesized and the GNP was uniformly distributed in the composites, and the complex permittivity of BiFeO3/GNP/epoxy composites increased with increasing the GNP content due to the interface polarization and conductance loss. The minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm when the GNP content was 2 wt%, and also the absorbing properties of (BiFeO3+GNP)/epoxy composites can be tailored by the GNP content and composite thickness, which may be used as a kind of absorbing materials with good absorbing performance and low density.
Graphical abstract The reflection loss curves and the simulated matching thickness of GNP-BiFeO3-epoxy composites with 2 wt% GNP content. As can be seen, the minimum reflection loss value was reached to ??45 dB at 9.25 GHz with the thickness of 1.4 mm, and also the quarter-wavelength matching theory can be used to illustrate the good absorbing properties of GNP-BiFeO3-epoxy composites.
Small core-shell Fe3O4@Pd superparamagnetic nanoparticles (MNPs) were obtained with good control in size and shape distribution by metal-complex thermal decomposition in organic media. The role of the stabilizer in the synthesis of MNPs was studied, employing oleylamine (OA), triphenylphosphine (TPP) and triphenylamine (TPA). The results revealed that, among the stabilizer investigated, the presence of oleylamine in the reaction media is crucial in order to obtain an uniform shell of Pd(0) in Fe3O4@Pd MNPs of 7?±?1 nm. The synthesized core-shell MNPs were tested in Pd-catalyzed Heck-Mizoroki and Suzuki-Miyaura coupling reactions and p-chloronitrobenzene hydrogenation. High conversion, good reaction yields, and good TOF values were achieved in the three reaction systems with this nanocatalyst. The core-shell nanoparticle was easily recovered by a simple magnetic separation using a neodymium commercial magnet, which allowed performing up to four cycles of reuse.
The most important limitation for boron neutron capture therapy of cancer is the selective accumulation of boron compounds in tumor tissues in significant quantities. In this paper, we describe the possibility to use magnetic Ni/Fe nanotubes as carriers for boron delivery. Carborane derivatives containing 10 and 21 boron atoms per molecule were immobilized on Ni/Fe nanotubes by covalent and ionic interactions. Magnetic properties of NTs were investigated by Mössbauer spectroscopy. Structure, element, chemical composition, and morphology of obtained magnetic nanotubes were studied by XRD, SEM-EDA, and FTIR spectroscopy. Results indicate success immobilization of carborane derivatives on Ni/Fe nanotubes and great potential to use them as carriers for boron neutron cancer therapy of cancer.
In this study Pt, Re, and SnO2 nanoparticles (NPs) were combined in a controlled manner into binary and ternary combinations for a possible application for ethanol oxidation. For this purpose, zeta potentials as a function of the pH of the individual NPs solutions were measured. In order to successfully combine the NPs into Pt/SnO2 and Re/SnO2 NPs, the solutions were mixed together at a pH guaranteeing opposite zeta potentials of the metal and oxide NPs. The individually synthesized NPs and their binary/ternary combinations were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS) analysis. FTIR and XPS spectroscopy showed that the individually synthesized Pt and Re NPs are metallic and the Sn component was oxidized to SnO2. STEM showed that all NPs are well crystallized and the sizes of the Pt, Re, and SnO2 NPs were 2.2, 1.0, and 3.4 nm, respectively. Moreover, EDS analysis confirmed the successful formation of binary Pt/SnO2 and Re/SnO2 NP, as well as ternary Pt/Re/SnO2 NP combinations. This study shows that by controlling the zeta potential of individual metal and oxide NPs, it is possible to assemble them into binary and ternary combinations.
Preparation, characterization, and electrocatalytic study of the electrodeposited Pt and Pd (e.g., Pt and PtPd) catalysts on titanium dioxide (TiO2) modified reduced graphene oxide (rGO) support for formic acid oxidation were performed. The catalyst composites are labeled as xPt/rGO-TiO2, xPtyPd/rGO-TiO2, and yPd/rGO-TiO2 where x and y are cycle numbers of metal electrodeposition (x and y?=?2–6). The characterizations of the catalysts were performed by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Small and dispersed metal nanoparticles are obtained on rGO-TiO2. The catalytic performances for formic acid oxidation were measured by cyclic voltammetry (CV) and chronoamperometry (CA). The electrocatalytic results reveal that the bimetallic 4Pt2Pd/rGO-TiO2 catalyst facilitates formic acid oxidations at the lowest potentials and generates the highest oxidation currents and also improves the highest CO oxidation compared to the monometallic 6Pt/rGO-TiO2 catalyst. According to the experimental data, the Pd and TiO2 enhance the electrocatalytic activity of the catalysts towards the formic acid oxidation; the improved catalytic performance of the prepared catalysts strongly relates to the high electrochemically active surface area (ECSA) investigated.
The distributed Bragg reflectors (DBRs) consisting of alternating layers of ZnO and heavy doped amorphous silicon (a-Si) have been fabricated by magnetron sputtering. It is novel to find that the optical absorptions exist in the stopband of the DBRs, and that many discrete strong optical absorption peaks exist in the wavelength range of visible to near-infrared. The calculated results by FDTD show that the absorptions in the stopband mainly exist in the first a-Si layer, and that the light absorbed by other a-Si layers inside contributes to the two absorption peaks in near-infrared range. The strong absorptions ranged from visible to infrared open new possibilities to the enhancement of the performance of amorphous silicon solar cells.
In recent years, two-dimensional confined catalysis, i.e., the enhanced catalytic reactions in confined space between metal surface and two-dimensional overlayer, makes a hit and opens up a new way to enhance the performance of catalysts. In this work, graphdiyne overlayer was proposed as a more excellent material than graphene or hexagonal boron nitride for two-dimensional confined catalysis on Pt(111) surface. Density functional theory calculations revealed the superiority of graphdiyne overlayer originates from the steric hindrance effect which increases the catalytic ability and lowers the reaction barriers. Moreover, with the big triangle holes as natural gas tunnels, graphdiyne possesses higher efficiency for the transit of gaseous reactants and products than graphene or hexagonal boron nitride. The results in this work would benefit future development of two-dimensional confined catalysis.
The rise in environmental issues due to the catalytic degradation of pollutants in water has received much attention. In this report, a facile method was developed for the generation of a novel thermosensitive Ag-decorated catalyst, SiO2@PNIPAM@Ag (the average particle size is around 540 nm), through atom transfer radical polymerization (ATRP) and mild reducing reactions. First, poly(N-isopropylacrylamide) (PNIPAM) was used to create a shell around mercapto-silica spheres that allowed for enhanced catalyst support dispersion into water. Second, through a mild reducing reaction, these Ag nanoparticles (NPs) were then anchored to the surface of SiO2@PNIPAM spheres. The resulting catalyst revealed catalytic activity to degrade various nitrobenzenes and organic dyes in an aqueous solution with sodium borohydride (NaBH4) at ambient temperature. The catalytic activity can be adjusted in different temperatures through the aggregation or dispersion of Ag catalyst on the polymer supporters, which is due to the thermosensitive PNIPAM shell. The ease of preparation and efficient catalytic activity of the catalyst can make it a promising candidate for the use in degrading organic pollutants for environmental remediation.
A nitrogen-doped reduced graphene oxide (N-RGO) nanosheet was synthesized by a simple hydrothermal method and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electrode microscopy. After being deposited as counter electrode film for dye-sensitized solar cells (DSSCs), it is found that the synthesized N-RGO nanosheet has smaller charge-transfer resistance and better electrocatalytic activity towards reduction of triiodide than the reduced graphene oxide (RGO) nanosheet. Consequently, the DSSCs based on the N-RGO counter electrode achieve an energy conversion efficiency of 4.26%, which is higher than that of the RGO counter electrode (2.85%) prepared under the same conditions, and comparable to the value (5.21%) obtained with the Pt counter electrode as a reference. This N-RGO counter electrode offers the advantages of not only saving the cost of Pt itself but also simplifying the process of counter electrode preparation. Therefore, an inexpensive N-RGO nanosheet is a promising counter electrode material to replace noble metal Pt.
Graphical abstract A nitrogen-doped reduced graphene oxide nanosheet was synthesized by a simple hydrothermal method, which is a promising counter electrode material to replace noble metal Pt.
Active iron-containing nanosized components have been formed on the lignin surface. The metal was deposited on the lignin from an ethanol solution of Fe(acac)3 and from a colloid solution of iron metal particles obtained beforehand by metal vapor synthesis. These active components are able to absorb microwave radiation and are suitable for microwave-assisted high-rate dehydrogenation and dry reforming of lignin without addition of a carbon adsorbent, as a supplementary radiation absorbing material, to the feedstock. The dependence of the solid lignin heating dynamics on the concentration of supported iron particles was investigated. The threshold Fe concentration equal to 0.5 wt.%, providing the highest rate of sample heating up to the reforming and plasma generation temperature was identified. The microstructure and magnetic properties of iron-containing nanoparticles supported on lignin were studied before and after the reforming. The Fe3O4 nanoparticles and also core-shell Fe3O4@γ-Fe-С nanostructures are formed during the reforming of lignin samples. The catalytic performance of iron-based nanoparticles toward the lignin conversion is manifested as increasing selectivity to hydrogen and syngas, which reaches 94% at the Fe concentration of 2 wt.%. It was found that with microwave irradiation under argon, hydrogen predominates in the gas. In the СО2 atmosphere, dry reforming takes place to give syngas with the СО/Н2 ratio of ~?0.9. In both cases, the degree of hydrogen recovery from lignin reaches 90–94%.
Graphical abstract The microwave-supported deposition of iron on the lignin surface gives active well defined nanoparticles Fe3O4 and also core-shell Fe3O4@γ-Fe-С nanostructures. These nanocomponents provide for high-rate microwave-assisted dehydrogenation and dry reforming of lignin.
A carbon-coated sulfur/polyacrylonitrile (C@S/PAN) core-shell structured composite is successfully prepared via a novel solution processing method. The sulfur/polyacrylonitrile (S/PAN) core particle has a diameter of ~ 100 nm, whereas the carbon shell is about 2 nm thick. The as-prepared C@S/PAN composite shows outstanding electrochemical performance in lithium/sulfur (Li/S) batteries delivering a high initial discharge capacity of 1416 mAh g?1. Furthermore, it exhibits ~ 89% retention of the initial reversible capacity over 200 cycles at a constant current rate of 0.1 C. The improved performance contributed by the unique composition and the core-shell structure, wherein carbon matrix can also withstand the volume change of sulfur during the process of charging and discharging as well as provide channels for electron transport. In addition, polyacrylonitrile (PAN) matrix suppresses the shuttle effect by the covalent bonding between sulfur (S) and carbon (C) in the PAN matrix.
It is well known that when nanoparticles (NPs) are exposed to biological fluid, it results into formation of nanoparticle protein corona, which has been the subject of extensive studies for the development of targeted drug delivery. In this work, we demonstrated the dynamic light scattering, fluorescence, and UV-visible spectroscopy as quantitative and qualitative tools to monitor adsorption of BSA protein onto silver nanoparticles (AgNPs). The adsorption resulted in significant gradual increase in average hydrodynamic radius of BSA-AgNP corona from 24 to 35 nm and its attainment of equilibrium point (saturation) that correlated with albumin concentration enables condition for bound and unbound protein adsorption to be interpreted. Using DLS, the dissociation constant (KD) was obtained for soft corona to be 2.09?±?0.30 μM. The UV-visible and fluorescence spectroscopy results were correlated with DLS. Loss of percent helicity in secondary structure of adsorbed BSA was monitored in both coronas as compared to native protein. Both coronas were found to be biocompatible with RBC membrane. Further, the results of adsorption isotherm model were used to validate the multilayer formation of albumin protein on silver nanoparticles. The obtained results would be relevant in the drug design development for tumor-targeted therapy.
