Controlled in situ growth of tunable plasmonic self-assembled nanoparticle arrays (original) (raw)
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ACS Nano, 2011
We describe a rapid, simple, room-temperature technique for the production of large-scale metallic thin films with tunable plasmonic properties assembled from size-selected silver nanoplates (SNPs). We outline the properties of a series of ultrathin monolayer metallic films (8À20 nm) self-assembled on glass substrates in which the localized surface plasmon resonance can be tuned over a range from 500 to 800 nm. It is found that the resonance peaks of the films are strongly dependent on the size of the nanoplates and the refractive index of the surrounding dielectric. It is also shown that the bandwidth and the resonance peak of the plasmon resonance spectrum of the metallic films can be engineered by simply controlling aggregation of the SNP. A three-dimensional finite element method was used to investigate the plasmon resonance properties for individual SNPs in different dielectrics and plasmon coupling in SNP aggregates. A 5À17 times enhancement of scattering from these SNP films has been observed experimentally. Our experimental results, together with numerical simulations, indicate that this self-assembly method shows great promise in the production of nanoscale metallic films with enormous electric-field enhancements at visible and near-infrared wavelengths. These may be utilized in biochemical sensing, solar photovoltaic, and optical processing applications.
Narrow plasmon mode in 2D arrays of silver nanoparticles self-assembled on thin silver films
Journal of Microscopy, 2008
Extinction spectra of 2D arrays of silver nanoparticles self-assembled on 5-20-nm-thick vacuum-deposited silver films exhibit extremely narrow plasmon mode in the blue spectral region, whereas the same particles self-assembled on thin films of Au, Cu, Cr and Ti damp the plasmon resonance. The observed narrowing was attributed to the plasmon coupling between the nanoparticles and between the nanoparticles and surface modes in the underlying silver film.
Periodic structures modified with silver nanoparticles for novel plasmonic application
Nanophotonics II, 2008
Forming structures similar to or smaller than the optical wavelength offers a wide range of possibilities to modify the optical properties of materials. Tunable optical nanostructures can be applied as materials for surface-enhanced spectroscopy, optical filters, plasmonic devices, and sensors. In this work we present experimental results on technology and properties of periodical, polymer based optical structures modified by ordered adsorption of silver nanoparticles. These structures were formed combining UV hardening and dip coating from colloidal solutions. We have investigated the influence of silver nanoparticles assembly on the ambient conditions (deposition temperature and time) and surface features (periodicities and shape) of the template micro structures. Optical absorbance as well as morphology of the structures containing silver nanoparticles were investigated by UV-VIS spectroscopy, AFM, SEM and optical microscopy. The influence of silver nanoparticles on the optical properties of the structures was investigated by polarized light spectroscopy (Grating Light Reflection Spectroscopy -GLRS). From the results of this study we propose a low cost procedure for fabricating structures that could be potentially new type of plasmonic sensors exploiting surface enhanced plasmon resonance in silver nano structures.
Broadband tunable plasmonic substrate using self-assembled gold-silver alloy nanoparticles
In the present work, a facile approach of Au-Ag alloy NPs fabrication is proposed for plasmonic inclusion appli-cative studies. These hybrid NPs were prepared by the sequential deposition of Ag, Au layers on a glass substrate via RF-sputtering followed by high-temperature annealing. Compositional and size controllability of the NPs was attained by changing the ratio of nominal thicknesses of the respective Au, and Ag layers during the deposition. LSPR red (blue) peak shift occurs with increasing layer thickness Au (Ag) signifying the peak sensitivity. The influence of geometrical, compositional, and background media for achieving LSPR-sensitivity is examined and validated by FDTD simulation studies. With the agreeable peak shift tendencies, the proposed study of broadband tunable LSPR-sensitivity is expected to provide a framework for a wide range of plasmonic applications.
Self-standing corrugated Ag and Au-nanorods for plasmonic applications
Journal of Materials Chemistry, 2011
We use home-made Si-supported anodized alumina thin film templates for the electrodeposition of large area self-standing Ag-and Au-nanorod (Au-NR) arrays. The deposition conditions chosen, i.e. electrolyte composition and deposition voltage, lead to a corrugated rod morphology, particularly for Au-NRs. Instantaneous nucleation followed by diffusion-controlled growth are thought to be the dominating mechanism for the morphology observed. Diffuse reflectance spectra show specific behaviours of Ag-and Au-NRs with longitudinal and transverse plasmon resonance modes and additional modes for Ag-NRs. The activity of the NR arrays as substrates for molecular detection using Raman scattering and Rhodamine 6G (R6G) as a model dye strongly depends on noble metal. R6G concentrations down to 1 pM are detected on the corrugated arrays yielding an effective enhancement factor (EF) of approximately 2 Â 10 10 for Ag-NRs and 1 Â 10 9 for Au-NRs. The latter is the highest ever obtained for Au-nanostructures. Both nanostructures provide an enhancement that is high enough to detect single molecules using Raman scattering. The results are rationalized in terms of morphology effects on electromagnetic field intensity.
Nanomaterials
This study demonstrates a new, robust, and accessible deposition technique of metal nanoparticle arrays (NPAs), which uses nanoporous anodic alumina (NAA) as a template for capillary force-assisted convective colloid (40, 60, and 80 nm diameter Au) assembly. The NPA density and nanoparticle size can be independently tuned by the anodization conditions and colloid synthesis protocols. This enables production of non-touching variable-density NPAs with controllable gaps in the 20–60 nm range. The NPA nearest neighbor center distance in the present study was fixed to 100 nm by the choice of anodization protocol. The obtained Au NPAs have the resonant scattering maxima in the visible spectral range, with a refractometric sensitivity, which can be tuned by the variation of the array density. The thickness of the NAA layer in an Aluminum-NAA-NPA multilayer system enables further tuning of the resonance frequency and optimization for use with specific molecules, e.g., to avoid absorption ba...
Strongly Coupled Plasmonic Modes on Macroscopic Areas via Template-Assisted Colloidal Self-Assembly
Nano Letters, 2014
We present ensembles of surface-ordered nanoparticle arrangements, which are formed by templateassisted self-assembly of monodisperse, protein-coated gold nanoparticles in wrinkle templates. Centimeter-squared areas of highly regular, linear assemblies with tunable line width are fabricated and their extinction cross sections can be characterized by conventional UV/vis/NIR spectroscopy.
The Journal of Physical Chemistry C, 2021
Localized surface plasmon resonance (LSPR) of metal nanoparticles are widely used to develop plasmonic sensors, which permit to detect minute amounts of molecular compounds. Two methods of measurements are commonly used. The first most common mode, which investigates the shift in wavelength of the LSPR induced by the analyte, requires the use of high-resolution monochromators. The second mode, based on self-reference or perfect absorbing systems, measures the changes of the signal intensity, and requires the use of sophisticated samples elaborated by lithography techniques. In this article, we adapt the very sensitive transmittance anisotropy spectroscopy technique with anisotropic plasmonic gold films, formed of slightly elongated nanoparticles easily elaborated by grazing deposition on microscopy glass slides. These films display two different LSPR, caused by their morphological anisotropy, as a function of the light polarization. Working at a single wavelength, we experimentally demonstrate an ultrahigh sensitivity to bulk refractive index sensing, with a resolution below δn=10-4. The factor of merit (FoM*), defined for intensity-based plasmonic sensors, reaches the outstanding value of 23 000, which is due to the null optical anisotropy signal initially measured, thus granting an enhanced optical contrast when changing the RI. Furthermore, sensitivity down to four avidin molecules per square micron of the sample is theoretically shown, which offers a promising route towards easily made ultra-sensitive miniaturized plasmonic sensors, compatible with microfluidic systems, without the need for a monochromator.