Pd Nanocubes Research Articles

An Effective Strategy for Room-Temperature Synthesis of Single-Crystalline Palladium Nanocubes and Nanodendrites in Aqueous Solution

Nearly monodisperse single-crystalline palladium (Pd) nanocubes and nanodendrites have been successfully prepared in aqueous solution at room temperature, for the first time, mainly by utilizing the equilibrium between the dissolution and precipitation of the Pd-cetyltrimethylammonium bromide (Pd-CTAB) complexes. The morphology of the obtained Pd nanocrystals can be tuned by the addition of foreign halide ions (Cl− and Br−). The corresponding selected area electron diffraction (SAED) and X-ray diffraction (XRD) patterns confirmed that the synthesis of nanocubes and nanodendrites are single-crystalline pure Pd structures with fcc crystal lattice. A preliminary formation mechanism based on the dissolution and precipitation of the Pd-CTAB complexes and competitive adsorption between different ions on the nanoparticle surface has been proposed.

Electrochemical Biosensor of Nanocube-Augmented Carbon Nanotube Networks

Networks of single-walled carbon nanotubes (SWCNTs) decorated with Au-coated Pd (Au/Pd) nanocubes are employed as electrochemical biosensors that exhibit excellent sensitivity (2.6 mA mM(-1) cm(-2)) and a low estimated detection limit (2.3 nM) at a signal-to-noise ratio of 3 (S/N = 3) in the amperometric sensing of hydrogen peroxide. Biofunctionalization of the Au/Pd nanocube-SWCNT biosensor is demonstrated with the selective immobilization of fluorescently labeled streptavidin on the nanocube surfaces via thiol linking. Similarly, glucose oxidase (GOx) is linked to the surface of the nanocubes for amperometric glucose sensing. The exhibited glucose detection limit of 1.3 muM (S/N = 3) and linear range spanning from 10 muM to 50 mM substantially surpass similar CNT-based biosensors. These results, combined with the structure's compatibility with a wide range of biofunctionalization procedures, would make the nanocube-SWCNT biosensor exceptionally useful for glucose detection in diabetic patients and well suited for a wide range of amperometric detection schemes for clinically important biomarkers.

Single-phase aqueous approach toward Pd sub-10 nm nanocubes and Pd–Pt heterostructured ultrathin nanowires

Monodisperse, highly-selective sub-10 nm Pd and Rh nanocubes have been successfully synthesized and, for the first time, bimetallic Pd-Pt heterostructured ultrathin nanowires have been achieved through using Pd nanocubes as seeds by a one-pot, single-phase aqueous method.

Biosensor Capture Kinetics Model of Nanocube-Augmented Carbon Nanotube Networks

AbstractAu-coated Pd (Au/Pd) nanocubes (˜250 nm in width) connected via a network of single-walled carbon nanotubes (SWCNTs) have been employed as an electrochemical biosensor. As previously reported, these in situ Au/Pd nanocube SWCNT networks are capable of ultrasensitive amperometric sensing of glucose, with a sensitivity, detection limit, and linear sensing range greater than similar CNT-based glucose biosensors. The 3D mass diffusion of glucose molecules to the Au/Pd nanocube surfaces, forced convection environment of the testing vial, and Brownian motion of the Au/Pd nanocubes are all likely factors contributing to the strong electrochemical performance of the Au/Pd-SWCNT biosensor. In an effort to elucidate the effects of these contributing factors, this work demonstrates an analytical biosensor capture kinetics model that analyzes the analyte-biosensor mass transfer by molecular diffusion and convection due to both the fluid motion within the test vial and the Brownian motion of the Au/Pd nanocubes themselves.The biosensor capture kinetics model incorporates a quasi steady-state integrated incident flux equation to model mass diffusion of biomolecules to the surface of a 1D planar, 2D nanowire, and 3D nanosphere surface in Cartesian, cylindrical, and spherical coordinates respectively. A Burgers vortex model is introduced to analyze the biosensor diffusion boundary layer within a test vial that experiences fluid downwelling and upwelling within the vial center and boundaries due to the rotation of a magnetic stir bar. Finally the convection-diffusion equation simplified by Stokes flow is utilized to model the diffusion boundary layer of the Au/Pd nanocubes experiencing Brownian motion.Several key conclusions can be interfered from this model. First, a biosensor experiencing 3D mass diffusion will exhibit a greater analyte concentration flux of at least one order of magnitude greater than a biosensor experiencing 2D diffusion and 1D mass diffusion in quiescent and convective fluid environments. Additionally, mass transfer by convection increases the concentration flux to the biosensor by inhibiting the continued advancement of the analyte depletion layer around the biosensor. Furthermore, the Brownian motion model of the Au/Pd nanocubes is shown to improve the mass transfer to the biosensor surface, portraying a substantial increase in amperometric current signal output as compared to a similar electrochemical-based biosensor with stationary Au/Pd nanocubes. In summary, the results of the biosensor capture kinetics model corroborate the high sensitivities and low detection limits previously observed experimentally by Au/Pd nanocube-SWCNT biosensors.

Seed-Mediated Growth of Nearly Monodisperse Palladium Nanocubes with Controllable Sizes

Nearly monodisperse Pd nanocubes with controllable sizes were synthesized through a seed-mediated growth approach. By using Pd nanocubes of 22 nm in size as seeds, the morphology of the as-grown nanostructures was fixed as single-crystalline, which enabled us to rationally tune the size of Pd nanocubes. The formation mechanism of initial 22 nm nanocubes was also discussed. The size-dependent surface plasmon resonance properties of the as-synthesized Pd nanocubes were investigated. Compared with previous methods, the yield, monodispersity, perfection of the shape formation, and the range of size control of these nanocubes are all improved. These Pd nanocubes may have potential interests in surface-enhanced Raman scattering, sensors, catalysis, study of size-dependent properties, and fabrication of high-order structures.

Highly Selective Synthesis of Catalytically Active Monodisperse Rhodium Nanocubes

Monodisperse sub-10 nm Rh nanocubes were synthesized with high selectivity (>85%) by a seedless polyol method. The {100} faces of the Rh NCs were effectively stabilized by chemically adsorbed Br- ions from trimethyl(tetradecyl)ammonium bromide (TTAB). This simple one-step polyol route can be readily applied to the preparation of Pt and Pd nanocubes. Moreover, the organic molecules of PVP and TTAB that encapsulated the Rh nanocubes did not prevent catalytic activity for pyrrole hydrogenation and CO oxidation.

Cubic to Tetragonal Phase Transformation in Cold-Compressed Pd Nanocubes

Pd nanocubes with an average side length of approximately 10 nm were compressed up to 24.8 GPa in a diamond-anvil cell (DAC). In situ synchrotron X-ray diffraction was used to monitor structural changes, and a face-centered cubic (fcc) to face-centered tetragonal (fct) distortion was observed for the first time. This novel discovery not only provides new insights into the pressure-induced behavior of faceted nanocrystals of palladium and other noble metals but also gives guidance for finding new phases in close-packed metals.

Controlled Decoration of Single-Walled Carbon Nanotubes with Pd Nanocubes

Although there have been many reports of nanoparticle-decorated single-walled carbon nanotubes (SWCNTs), the morphology of the resulting nanoparticles has lacked consistency and control. The present work demonstrates a process for decorating SWCNTs with Pd nanoparticles that have a tendency toward a selective and distinct cubic shape. SWCNTs were synthesized from an embedded catalyst in a porous anodic alumina (PAA) template. A single galvanostatic electrodeposition created Pd nanowires that contacted the SWCNTs within the pores and Pd nanoparticles that decorated the SWCNTs above the surface of the PAA. A distinct change in potential was observed as nanoparticles nucleated on the SWCNTs. The effects of current density and deposition time on the morphology of the nanoparticles were studied. Optimal deposition parameters yielded Pd nanocubes with smooth and flat facets. The electrochemical response and resulting nanocubic deposits provide insights into the difference in electrochemistry between metallic an...

Facile synthesis of monodisperse palladium nanocubes and the characteristics of self-assembly

This paper reports a facile synthesis for monodisperse 85 nm Pd nanocubes in aqueous solution at room temperature. By using cetyltrimethylammonium bromide (CTAB) as a capping reagent and reducing K 2PdCl 6 with ascorbic acid, the formation of 85 nm Pd nanocubes was clearly confirmed by observing the field-emission scanning electron microscopy images. After dispersion into pure water and casting on the surface of glassy carbon (GC), Pd nanocubes were found to assemble to form a two-dimensional square array, presumably due to the effect of CTAB. In addition, simply allowing the Pd nanocubes to lie in solution on the smooth GC surface lead to the formation of a flat and continuous structure of assembled Pd nanocubes on the GC surface.

Corrosion‐Based Synthesis of Single‐Crystal Pd Nanoboxes and Nanocages and Their Surface Plasmon Properties

Inside out: Corrosive pitting and etching can be combined in a simple, elegant, and powerful method to transform single-crystal Pd nanocubes into nanoboxes (see SEM image) and nanocages in a one-pot synthesis without the involvement of exotic templates. Emptying the interiors enables the surface plasmon resonance peaks of the Pd nanostructures to be tuned from 410 to 520 nm.

Size-Dependence of Surface Plasmon Resonance and Oxidation for Pd Nanocubes Synthesized via a Seed Etching Process

Pd nanocubes between 8 and 50 nm in size were synthesized at the same concentration of Na2PdCl4 precursor by controlling the number of seeds formed in the nucleation stage. Increasing the concentration of FeCl3, an oxidative etchant for Pd, reduced the number of seeds and led to formation of larger Pd nanocubes. The larger nanocubes exhibited surface plasmon resonance peaks in the visible region, the locations of which matched with the results of the discrete dipole approximation calculation. While the nanocubes of 25 and 50 nm in size oxidized in air to form Pd@PdO core-shell structures, the 8-nm nanocubes were stable in air for over 90 days.