Gold Cubes Research Articles

Shape dependent stripping behavior of Au nanoparticles toward arsenic detection: evidence of enhanced sensitivity on the Au (111) facet

This work reports a comparative study of gold cubes {100}, octahedra {111}, and rhombic dodecahedra {110} toward the detection of arsenic for the first time. Au octahedral nanoparticles were found to exhibit the highest sensitivity.

Investigation of electric field enhancement between metal blocks at the focused field generated by a radially polarized beam

A radially polarized beam possesses peculiar focusing properties compared with a linearly polarized beam, for example, the generation of a strong longitudinal field and zero intensity of the Poynting vector on the beam axis. In order to exploit these focusing properties, here we consider a system in which gold metal cubes are arranged along the propagation direction of the beam. An electric field enhancement of more than 20-times can be generated between two gold cubes separated by a distance λ/10 on the optical axis. This is because the energy of a radially polarized beam can propagate even if a metal cube is located on the beam axis, and a longitudinal field generated between the cubes can induce a surface plasmon mode. We show that these results are peculiar properties that cannot be produced with an incident linearly polarized beam. We also show that the beam can generate multiple regions of electrical field enhancement in the propagating direction when multiple metal cubes are arranged on the beam axis.

A surface plasmon resonance biosensor based on gold nanoparticle array

Using the finite-difference time-domain (FDTD) method, optical properties are investigated for a sensor comprising a two-dimensional array of gold cubes placed on quartz pillars on a quartz substrate. Background condition is analyzed for an approximate ideal collective resonance. It is found that the resonance intensity is mainly determined by the quartz etch depth, and the spectra valley position depends mainly on the lattice period. Thickness of the gold film affects the wavelength of the transmission spectra slightly, which gives a low processing tolerance requirement for fabrication. Sensitivity of the biosensor is also discussed, spectral sensitivity as high as 596.7nm/refractive index unit (RIU) is obtained in the visible light region, making it an excellent candidate for liquid detection.

Evolutionary Optimization of Optical Antennas

The design of nanoantennas has so far been mainly inspired by radio-frequency technology. However, the material properties and experimental settings need to be reconsidered at optical frequencies, which would entail the need for alternative optimal antenna designs. Here we subject a checkerboard-type, initially random array of gold cubes to evolutionary optimization. To illustrate the power of the approach, we demonstrate that by optimizing the near-field intensity enhancement, the evolutionary algorithm finds a new antenna geometry, essentially a split-ring-two-wire antenna hybrid that surpasses by far the performance of a conventional gap antenna by shifting the n=1 split-ring resonance into the optical regime.

Selective Laser Melting (SLM) of pure gold

This work presents an investigation into the Selective Laser Melting (SLM) of 24 carat gold (Au) powder with a mean particle size of 24μm. An SLM 100 system was used which is intended for production of highly detailed and intricate parts. Gold powder was tested for its properties such as tap density, Particle Size distribution (PSD) and reflectance etc. A suitable processing window was identified and gold cubes were produced using these parameters. Gold cubes were also checked for their internal porosity and mechanical properties.

Effect of Size, Shape, Composition, and Support Film on Localized Surface Plasmon Resonance Frequency: A Single Particle Approach Applied to Silver Bipyramids and Gold and Silver Nanocubes

AbstractLocalized surface plasmon resonances (LSPR), collective electron oscillations in nanoparticles, are being heavily scrutinized for applications in chemical and biological sensing, as well as in prototype nanophotonic devices. This phenomenon exhibits an acute dependence on the particle’s size, shape, composition, and environment. The detailed characterization of the structure-function relationship of nanoparticles is obscured by ensemble averaging. Consequently, single-particle data must be obtained to extract useful information from polydisperse reaction mixtures. Recently, a correlated high resolution transmission electron microscopy (HRTEM) LSPR technique has been developed and applied to silver nanocubes. We report here a second generation of experiments using this correlation technique, in which statistical analysis is performed on a large number of single particles. The LSPR dependence on size, shape, material, and environment was probed using silver right bipyramids, silver cubes, and gold cubes. It was found that the slope of the dependence of LSPR peak on size for silver bipyramids increases as the edges become sharper. Also, a plasmon shift of 96 nm was observed between similar silver and gold cubes, while a shift of 26 nm was observed, for gold cubes, between substrates of refractive index (RI) of 1.5 and 2.05.

Surface-specific overgrowth of platinum on shaped gold nanocrystals

Controlling the shape and composition of metal nanocrystals can be beneficial for tuning the optical or catalytic properties in a variety of applications. In this study, surface-specific overgrowth of platinum was found on shaped gold nanocrystals of cubes, octahedra and spheres. Platinum overgrowth was observed on the planar faces of gold cubes, while the overgrowth occurred at the vertices of gold octahedra, indicating that platinum was selectively reduced on the Au (100) surface for each gold nanocrystal shape. The platinum nuclei covered the entire surface for gold spheres, which don't have well-defined surfaces. As the Pt/Au ratio increased, a full platinum shell was formed. Solution-based UV-Vis absorption spectra of the composite nanocrystals showed that the absorption peak was red-shifted with increasing platinum coverage. The optical response of a single composite nanocrystal was measured by dark field microscope, which also demonstrated a red shift in the scattering spectrum with increasing platinum coverage. The extent of a red shift depended on the shape and composition of the composite nanocrystals.