A facile method to prepare noble metal nanoparticles modified Self-Assembly (SAM) electrode

Noble metal nanoparticles (NPs) modified electrodes have shown promising applications in the areas of catalysis, (electro)chemical analysis and biosensing due to their unique characters. In this paper, we introduced a so-called ligand exchange method to prepare self-assembly (SAM) electrode modified with noble metal nanoparticles. The noble metal nanoparticles protected by weakly adsorbed tetraoctylammonium bromide (TOAB) were synthesized firstly, then self-assembly (SAM) dithiol-modified Au electrode (Au-SH_SAM) was immersed into the solutions containing TOAB-protected nanoparticles. Due to the strong interaction between the dithiol groups on the electrode and noble metal nanoparticles, the weakly adsorbed TOAB on the surface of noble metal NPs were replaced by dithiol groups. As a result, the TOAB protected NPs were anchored on the Au-SH_SAM template electrode surface by ligand exchange, obtaining noble metal NPs modified electrode with high quality and stability. By adjusting the soaking time, the coverage of nanoparticles on the Au-SH_SAM electrode surface could be controlled. The morphology and distribution of noble metal NPs on Au-SH_SAM surface was analysis by scanning tunneling microscope (STM), and their electrochemical property was studied by cyclic voltammetry (CV) in H₂SO₄ solution. The approach is proved as a universal way to prepare noble metal NPs modified SAM electrode.     

Engineering the epitaxial interface of Pt-CeO_2 by surface redox reaction guided nucleation for low temperature CO oxidation

The interface between metal nanoparticles(NPs) and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface. However, the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge.Herein, a guided nucleation strategy based on redox reaction between noble metal precursor and supportsurface is introduced to construct epitaxial interfaces between Pt NPs and CeO_2 support. The Pt/CeO_2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO_2 support to Pt NPs. Meanwhile, this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO_2, demonstrating its universal and feasible characteristics. This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces.     

A General Strategy Assisted with Dual Reductants and Dual Protecting Agents for Preparing Pt‐Based Alloys with High‐Index Facets and Excellent Electrocatalytic Performance

Synthesizing noble metallic nanoparticles (NPs) enclosed by high‐index facets (HIFs) is challenged as it involves the tuning of growth kinetics, the selective adsorption of certain chemical species, and the epitaxial growth from HIF enclosed seeds. Herein, a simple and general strategy is reported by using dual reduction agents and dual capping agents to prepare Pt‐based alloy NPs with HIFs, in which both glycine and poly(vinylpyrrolidone) serve as the reductants and capping agents. Due to the facilely tunable growth/nucleation rates and protecting abilities of the reductants and capping agents, Pt concave nanocube (CNC), binary Pt–Ni CNC, ternary Pt–Mn–Cu CNC, and Pt–Mn–Cu ramiform polyhedron alloy NPs terminated by HIFs as well as other NPs with well‐defined morphologies such as Pt–Mn–Cu nanocube and Pt–Mn–Cu nanoflower are obtained with this approach. Owing to the high density of low‐coordinated Pt sites (HIF structure) and the unique electronic effect of Pt–Mn–Cu ternary alloys, the as‐prepared Pt–Mn–Cu NPs show enhanced catalytic activity toward methanol and formic acid electro‐oxidation reactions with excellent stability. This work provides a promising methodology for designing and fabricating Pt‐based alloy NPs as efficient fuel cell catalyst.     

Electrochemical, photoelectrochemical, and piezoelectric analysis of tyrosinase activity by functionalized nanoparticles

The electrochemical and photoelectrochemical detection of tyrosinase (TR) activity (an indicative marker for melanoma cancer cells) is reported, using Pt nanoparticles (NPs) or CdS NPs as electrocatalytic labels or photoelectrochemical reporter units. The Pt NPs or CdS NPs are modified with a tyrosine methyl ester, (1), capping layer. Oxidation of the capping layer by TR/O2 yields the respective L-DOPA and dopaquinone products. The reduction of the resulting mixture of products with citric acid yields the L-DOPA derivative,(3), as a single product. The association of the (3)-functionalized Pt NPs or CdS NPs to a boronic acid monolayer-modified electrode enables the electrochemical transduction of TR activity by the Pt-NPs-electrocatalyzed reduction of H2O2 or the photoelectrochemical transduction of TR activity by the generation of photocurrents in the presence of triethanolamine as a sacrificial electron donor. The detection limits for analyzing TR corresponds to 1 U and 0.1 U by the electrochemical and photoelectrochemical methods, respectively. The association of the Pt NPs or CdS NPs to the functionalized monolayer electrode is followed by quartz crystal microbalance measurements.     

Structure determination of chitosan-stabilized Pt and Pd based bimetallic nanoparticles by X-ray photoelectron spectroscopy and transmission electron microscopy

Chitosan (CTS)-stabilized bimetallic nanoparticles were prepared at room temperature (rt.) in aqueous solution. Palladium (Pd) and platinum (Pt) were selected as the first metals while iron (Fe) and nickel (Ni) functioned as the second metals. In order to obtain the noble metal core-transition metal shell structures, bimetallic nanoparticles were prepared in a two-step process: the preparation of mono noble metallic (Pd or Pt) nanoparticles and the deposition of transition metals (Fe or Ni) on the surface of the monometallic nanoparticles. The structures of the nanoparticles were studied using X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The XPS results show that Pd and Pt exist mainly in zero valences. The presence of Fe and Ni in the bimetallic nanoparticles affects the binding energy of Pd and Pt. Moreover, the studies of O 1s spectra indicate the presence of Fe or Ni shells. The analyses of TEM micrographs give the particle size and size distributions while the high-resolution TEM (HRTEM) micrographs show the existence of noble metal core lattices. The results confirm the formation of noble metal core-transition metal shell structures.     

Aerosol Spray Drying Guided Synthesis of Ultrasmall Alloyed Bimetallic Nanoparticles Supported on Silica for Catalytic Semihydrogenation

Supported bimetallic nanoparticles (NPs) with ultrasmall sizes and homogeneous alloying are attractive for catalysis. However, facile synthesis of this type of material remains very challenging. Here, the aerosol drying impregnation method for rapid, scalable, and general synthesis of silica-supported bimetallic NPs is proposed. The method relies on aerosol spray drying to promote the mixing and dispersing of binary metal precursors on SiO₂. It is capable of controlling the composition and size of bimetallic NPs and avoids the use of expensive metal complex salts and complicated experiment procedures. Twelve permutations combining a noble metal (Pd, Ru, and Pt) and a base one (Fe, Co, Ni, and Cu) with ultrasmall sizes (1.4–2.2 nm in average size), uniform dispersion, and good alloying are synthesized. Interesting activity and selectivity trends in catalytic semihydrogenation of phenylacetylene over the supported Pd-based NPs can be observed. The silica-supported PdNi NPs deliver both high activity and styrene selectivity. Spectroscopic and density functional theory calculation results reveal the improved chemoselectivity originated from the suitably down-shifted d-band center of the PdNi NPs inducing an increased energy barrier for overhydrogenation and a weakened styrene adsorption.     

A versatile route for the synthesis of Pt-loaded mesoporous CNT heterostructure

Abstract

A simple and versatile route for the synthesis of mesoporous carbon nanotube (CNT)-supported platinum/tungsten carbide (Pt/WC) nanoparticles (NPs) was set up via vapor deposition process. Amorphous CNT (α-CNT) was used to immobilize Pt/WC NPs. Platinum 2,4-pentanedionate, hexacarbonyltungsten and α-CNTs were selected as raw materials. Large density of W₂C/Pt NPs was uniformly decorated on the wall of α-CNTs and W₂C NPs were amorphous structured. The diameters of Pt NPs ranged from 3 to 6?nm, with mean diameter of about 4?nm. This approach provides an efficient method to fabricate carbides or other non-carbides metal NPs on CNT for the in situ synergistic fabrication of heterostructures.     

Formation and mechanism of silicon nanostructures by Ni-assisted etching

Instead of noble metal like Pt, Au and Ag, cheap Ni nanoparticles (Ni NPs) were used to fabricate silicon nanostructures. Ni was found to be etched off during the etching process, while forming silicon nanostructures with very low reflectance of 1.59 % from 400 to 900 nm. The formation mechanism of silicon nanostructures by Ni-assisted etching was presented from the point of view of the low electronegativity of Ni. The Ni NPs were found being etched off during the assisted etching process, which implies that the transfer rate of electrons from Si to Ni is slower than that from Ni to O^? in the case of using Ni as assisted metal. The reason of sparser and deeper silicon nanostructures etched in lower H₂O₂ concentration solution is that the Ni NPs can be lasted for longer time in the etching solution with lower H₂O₂ concentration so that more silicon atoms will be oxidized and then removed for those under Ni NPs due to the hole transfer and those where uncovered by Ni NPs due to the hole diffusion.     

Resistive random access memory utilizing ferritin protein with Pt nanoparticles

This study reports controlled single conductive paths found in resistive random access memory (ReRAM) formed by embedding Pt nanoparticles (Pt NPs) in NiO film. Homogeneous Pt NPs produced and placed by ferritin protein produce electric field convergence which leads to controlled conductive path formation. The ReRAM with Pt NPs shows stable switching behavior. A Pt NP density decrease results in an increase of OFF state resistance and decrease of forming voltage, whereas ON resistance was independent of the Pt NP density, which indicates that a single metal NP in a memory cell will achieve low power and stable operation.     

相转移过程中贵金属纳米颗粒的自组装行为

采用湿化学法制备了系列贵金属纳米颗粒（Ag、Au、Pt和Rh）,并通过相转移过程实现了贵金属纳米颗粒的自组装,首先将水相中制备的贵金属溶胶与十二胺的乙醇溶液混合,然后将十二胺稳定的金属颗粒从极性的水相中转移到非极性的有机相中。这种方法不仅能实现金属纳米颗粒在基底上的自组装,而且有望应用于纳米颗粒自组装膜的制备中。     

Dimensional and compositional dependent analysis of plasmonic bimetallic nanorods

The individual noble metal nanoparticles (NPs) are combined to form alloys with improved optical response, cost effectiveness and better stability. The selection of noble metal alloy NPs for their better use in plasmonic applications is being made on the bases of surface plasmon resonance peak position, its intensity and full width at half maxima (FWHM). Presently, the effect of metal composition (x), aspect ratio (R), size and metal type on the longitudinal plasmon resonance (LPR) of noble metal Ag–Au alloy nanorods (NRs) has been studied by applying modified Gans theory including finite wavelength effects and found that the LPR shifts towards the longer wavelength region with increase in aspect ratio and size of the NR. Moreover, a linear relationship which is in good agreement to the experimental results between the plasmon resonance and aspect ratio has been obtained. The aspect ratio and NR width-dependent absorption efficiency and FWHM have also been calculated. Further, a negligible effect of metal composition and its type is found on the LPR.     

A novel reusable platinum nanocatalyst

Recyclability of noble metal catalysts is a challenging issue when dealing with their industrial applications. Smart pH-sensitive Pt nanoparticles were successfully prepared for the first time by using octa(N,N-diacetic acid phenylamine)silsesquioxane (OAPAS) as a macromolecular protective agent. As-prepared Pt nanoparticles can self-aggregate or redisperse by only changing the pH of the system solution. In the weak acidic or alkaline solution (pH > 4.0), the Pt nanoparticles dispersed homogenously; while in the acidic solution (pH = 2.5), they self-aggregated. The dynamic self-aggregation and redispersion processes of the Pt nanoparticles driven by pH changes were revealed by transmission electron microscopy measurements. Electrocatalytic experiments proved that the platinum nanoparticles as a recyclable catalyst showed excellent activity for the hydrogenation of aldehyde after runs of five times. Such platinum nanoparticles are thereby anticipated to have great potential functioning as “smart” catalysts for industrial applications.     

From Single Atoms to Nanoparticles: Autocatalysis and Metal Aggregation in Atomic Layer Deposition of Pt on TiO2 Nanopowder

A fundamental understanding of the interplay between ligand‐removal kinetics and metal aggregation during the formation of platinum nanoparticles (NPs) in atomic layer deposition of Pt on TiO₂ nanopowder using trimethyl(methylcyclo‐pentadienyl)platinum(IV) as the precursor and O₂ as the coreactant is presented. The growth follows a pathway from single atoms to NPs as a function of the oxygen exposure (P_O2 × time). The growth kinetics is modeled by accounting for the autocatalytic combustion of the precursor ligands via a variant of the Finke–Watzky two‐step model. Even at relatively high oxygen exposures (<120 mbar s) little to no Pt is deposited after the first cycle and most of the Pt is atomically dispersed. Increasing the oxygen exposure above 120 mbar s results in a rapid increase in the Pt loading, which saturates at exposures >> 120 mbar s. The deposition of more Pt leads to the formation of NPs that can be as large as 6 nm. Crucially, high P_O2 (≥5 mbar) hinders metal aggregation, thus leading to narrow particle size distributions. The results show that ALD of Pt NPs is reproducible across small and large surface areas if the precursor ligands are removed at high P_O2.     

A General and Straightforward Route to Noble Metal‐Decorated Mesoporous Transition‐Metal Oxides with Enhanced Gas Sensing Performance

Controllable and efficient synthesis of noble metal/transition‐metal oxide (TMO) composites with tailored nanostructures and precise components is essential for their application. Herein, a general mercaptosilane‐assisted one‐pot coassembly approach is developed to synthesize ordered mesoporous TMOs with agglomerated‐free noble metal nanoparticles, including Au/WO₃, Au/TiO₂, Au/NbO_x, and Pt/WO₃. 3‐mercaptopropyl trimethoxysilane is applied as a bridge agent to cohydrolyze with metal oxide precursors by alkoxysilane moieties and interact with the noble metal source (e.g., HAuCl₄ and H₂PtCl₄) by mercapto (? SH) groups, resulting in coassembly with poly(ethylene oxide)‐b‐polystyrene. The noble metal decorated TMO materials exhibit highly ordered mesoporous structure, large pore size (≈14–20 nm), high specific surface area (61–138 m² g^?1), and highly dispersed noble metal (e.g., Au and Pt) nanoparticles. In the system of Au/WO₃, in situ generated SiO₂ incorporation not only enhances their thermal stability but also induces the formation of ε‐phase WO₃ promoting gas sensing performance. Owning to its specific compositions and structure, the gas sensor based on Au/WO₃ materials possess enhanced ethanol sensing performance with a good response (R_air/R_gas = 36–50 ppm of ethanol), high selectivity, and excellent low‐concentration detection capability (down to 50 ppb) at low working temperature (200 °C).     

MOF‐Derived Bifunctional Cu3P Nanoparticles Coated by a N,P‐Codoped Carbon Shell for Hydrogen Evolution and Oxygen Reduction

Metal–organic frameworks (MOFs) have recently emerged as a type of uniformly and periodically atom‐distributed precursor and efficient self‐sacrificial template to fabricate hierarchical porous‐carbon‐related nanostructured functional materials. For the first time, a Cu‐based MOF, i.e., Cu‐NPMOF is used, whose linkers contain nitrogen and phosphorus heteroatoms, as a single precursor and template to prepare novel Cu₃P nanoparticles (NPs) coated by a N,P‐codoped carbon shell that is extended to a hierarchical porous carbon matrix with identical uniform N and P doping (termed Cu₃P@NPPC) as an electrocatalyst. Cu₃P@NPPC demonstrates outstanding activity for both the hydrogen evolution and oxygen reduction reaction, representing the first example of a Cu₃P‐based bifunctional catalyst for energy‐conversion reactions. The high performances are ascribed to the high specific surface area, the synergistic effects of the Cu₃P NPs with intrinsic activity, the protection of the carbon shell, and the hierarchical porous carbon matrix doped by multiheteroatoms. This strategy of using a diverse MOF as a structural and compositional material to create a new multifunctional composite/hybrid may expand the opportunities to explore highly efficient and robust non‐noble‐metal catalysts for energy‐conversion reactions.     

Regular arrays of monodisperse platinum/erbium disilicide core-shell nanowires and nanoparticles on Si(001) via a self-assembled template

We have developed a process for fabricating monodisperse noble metal/rare earth disilicide core-shell nanoparticles and nanowires in regular arrays on Si(001) with a density of 5 x 10(10) / cm2, and over areas > 1 mm2. Pt deposited via physical vapor deposition on a self-assembled rare earth disilicide nanowire template combined with reactive ion etching produces arrays of nanostructures. SEM images demonstrate the ability to select nanowires or nanoparticles as a function of Pt coverage. Statistical analysis of images of Pt nanoparticle arrays yield a mean feature size of 8 nm with a size variation of +/- 0.9 nm and interparticle spacing of approximately 15 nm.     

Recent Progress in Syntheses and Applications of Dumbbell‐like Nanoparticles

This paper reviews the recent research progress in the syntheses and applications of dumbbell‐like nanoparticles (NPs). It first describes the general synthesis of dumbbell‐like NPs that contain noble metal and magnetic NPs/or quantum dots. It then outlines the interesting optical and magnetic properties found in these dumbbell NPs. The review further highlights several exciting application potentials of these NPs in catalysis and biomedicine.     

Nonspherical Noble Metal Nanoparticles: Colloid‐Chemical Synthesis and Morphology Control

Metal nanoparticles have been the subject of widespread research over the past two decades. In recent years, noble metals have been the focus of numerous studies involving synthesis, characterization, and applications. Synthesis of an impressive range of noble metal nanoparticles with varied morphologies has been reported. Researchers have made a great progress in learning how to engineer materials on a nanometer length scale that has led to the understanding of the fundamental size‐ and shape‐dependent properties of matter and to devising of new applications. In this article, we review the recent progress in the colloid‐chemical synthesis of nonspherical nanoparticles of a few important noble metals (mainly Ag, Au, Pd, and Pt), highlighting the factors that influence the particle morphology and discussing the mechanisms behind the nonspherical shape evolution. The article attempts to present a thorough discussion of the basic principles as well as state‐of‐the‐art morphology control in noble metal nanoparticles.     

Memory characteristics of a self-assembled monolayer of Pt nanoparticles as a charge trapping layer

A self-assembled monolayer of Pt nanoparticles (NPs) was studied as a charge trapping layer for non-volatile memory (NVM) applications. Pt NPs with a narrow size distribution (diameter ～4?nm) were synthesized via an alcohol reduction method. The monolayer of these Pt NPs was immobilized on a SiO(2) substrate using poly(4-vinylpyridine) (P4VP) as a surface modifier. A metal-oxide-semiconductor (MOS) type memory device with Pt NPs exhibits a relatively large memory window of 5.8?V under ± 7?V for program/erase voltage. These results indicate that the self-assembled Pt NPs can be utilized for NVM devices.     

Preparation Ru,Bi monolayer modified Pt nanoparticles as the anode catalyst for methanol oxidation

Platinum nanoparticles were successfully electrodeposited on indium tin oxide (ITO) surface in the solution with hexachloroplatinic acid and copper ion by cyclic voltammogram method. The micrographs and structure of Pt nanoparticles were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The electrocatalytic properties of Pt nanoparticles/ITO or modified by Ru, Bi underpotential deposition (UPD) for methanol oxidation have been investigated by cyclic voltammetry (CV) and chronoamperometry (CA). High electroactivity and good long-term stability can be observed. These results indicate that Pt nanoparticles modified by UPD may have potential applications in designing noble metal catalysts of fuel cells with low loading and high activity at the atomic level.