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Maximum Surface E-Field and Absorbed Power Enhancement within Rh Segments as a Function of Its Porosity and Location within the Bimetallic NRs
Source publication
A variety of multisegmented nanorods (NRs) composed of dense Au and porous Rh and Ru segments with lengths controlled down to ca. 10 nm are synthesized within porous anodic aluminum oxide membranes. Despite the high Rh and Ru porosity (i.e., ∼40%), the porous metal segments are able to efficiently couple with the longitudinal localized surface plas...
Contexts in source publication
Context 1
... corresponds to the porous segment. For a dense Rh (Ru) segment, it is possible to independently enhance the surface Efield or the bulk absorption by locating the Rh (Ru) segment either at the end of the NR or in the center of the Au NR (see Tables 1 and S1 for the expected enhancement values of the surface E-field and the absorbed power for each NR composition and geometry). Indeed, locating the dense Rh (Ru) segment at the end of the Au rod leads to the highest surface E-field enhancement, expected to be 5.6 (11) times larger than when the segment is in the middle of the Au NR. ...Context 2
... similar trend is observed for porous Rh (Figure 7, lower row) and Ru segments ( Figure S6), although with some important differences. Our simulation results suggest that the porous nature of the Rh (Ru) segment provides E-field and P abs enhancements that are significantly larger than those provided by a dense Rh (Ru) segment (see Tables 1 and S1 and Figures 7 and S6). Additionally, even when the porous Rh (Ru) segment is located in the middle of the NR, the surface E-field enhancement is large, which is not the case when a dense Rh (Ru) segment is used. ...Similar publications
The work introduces a localized surface plasmon resonance (LSPR) sensor chip integrated with vertical-cavity surface-emitting lasers (VCSELs). Using VCSEL as the light source, the hexagonal gold nanoparticle array was integrated with anodic aluminum oxide (AAO) as the mask on the light-emitting end face. The sensitivity sensing test of the refracti...
Citations
... This demonstrates that the SiNW dimer morphology provides the largest E-field enhancement at 785 nm, which is confirmed by finitedifference time-domain (FDTD) electromagnetic simulations. 7,54,55 ■ RESULTS AND DISCUSSION VA-SiNW arrays were prepared via colloidal lithography using core−shell SiO 2 @PDMAEMA (poly(2-(dimethylamino)ethyl methacrylate)) colloidal particles with a SiO 2 diameter of (170 ± 7) nm and hydrodynamic diameter of the core−shell particle of (481 ± 75) nm (Figure 1). 53 These particles were selfassembled at the air−water interface and compressed using a Langmuir trough. ...
... The script of the advanced power analysis group by Lumerical was adjusted to derive and integrate the (E-field) 4 components over the volume of the 5 nm shell. 7,54 ■ ASSOCIATED CONTENT ...
We report the synthesis of vertically aligned silicon nanowire (VA-SiNW) oligomer arrays coated with Au nanoparticle (NP) monolayers via a combination of colloidal lithography, metal-assisted chemical etching, and directed NP assembly. Arrays of SiNW monomers (i.e., isolated NWs), dimers, and tetramers are synthesized, decorated with AuNPs, and tested for their performance in surface-enhanced Raman spectroscopy. The ∼20 nm AuNPs easily enter within the ca. 40 nm gaps of the SiNW oligomers, thus reaching the hot spot region. At 785 nm excitation, the AuNPs@SiNW dimer arrays provide the highest Raman signal, in agreement with electromagnetic simulations showing a high electric field enhancement at the Au/Si interface within the dimer gap region.
... With this, the contribution of the 1 nm thin shell around the AuNP, which is a measure for the overall surface E-field relevant for SERS, could be extracted. 74 ■ ASSOCIATED CONTENT ...
Gold nanoparticle/silicon composites are canonical substrates for sensing applications because of their geometry-dependent physicochemical properties and high sensing activity via surface-enhanced Raman spectroscopy (SERS). The self-assembly of gold nanoparticles (AuNPs) synthesized via wet-chemistry on functionalized flat silicon (Si) and vertically aligned Si nanowire (VA-SiNW) arrays is a simple and cost-effective approach to prepare such substrates. Herein, we report on the critical parameters that influence nanoparticle coverage, aggregation, and assembly sites in two- and three-dimensions to prepare substrates with homogeneous optical properties and SERS activity. We show that the degree of AuNP aggregation on flat Si depends on the silane used for the Si functionalization, while the AuNP coverage can be adjusted by the incubation time in the AuNP solution, both of which directly affect the substrate properties. In particular, we report the reproducible synthesis of nearly touching AuNP chain monolayers where the AuNPs are separated by nanoscale gaps, likely to be formed due to the capillary forces generated during the drying process. Such substrates, when used for SERS sensing, produce a uniform and large enhancement of the Raman signal due to the high density of hot spots that they provide. We also report the controlled self-assembly of AuNPs on VA-SiNW arrays, which can provide even higher Raman signal enhancement. The directed assembly of the AuNPs in specific regions of the SiNWs with a control over NP density and monolayer morphology (i.e., isolated vs nearly touching NPs) is demonstrated, together with its influence on the resulting SERS activity.
... This can be used to control the surface E-field enhancement at the end of metal NRs and the light absorption as a function of wavelength [43,44]. Interestingly, while the highest surface E-fields are observed at the ends of the plasmonic NR, electromagnetic simulations indicate that the highest bulk E-field and, thus, light absorption occurs in the middle of the NR [44]. [2]. ...
... By adjusting the aspect ratio of the metal NRs, it is possible to tune the longitudinal mode resonance frequency and, therefore, the energies at which the E-field will be enhanced (Figure 2a,b) [13,42]. This can be used to control the surface E-field enhancement at the end of metal NRs and the light absorption as a function of wavelength [43,44]. Interestingly, while the highest surface E-fields are observed at the ends of the plasmonic NR, electromagnetic simulations indicate that the highest bulk E-field and, thus, light absorption occurs in the middle of the NR [44]. ...
... This can be used to control the surface E-field enhancement at the end of metal NRs and the light absorption as a function of wavelength [43,44]. Interestingly, while the highest surface E-fields are observed at the ends of the plasmonic NR, electromagnetic simulations indicate that the highest bulk E-field and, thus, light absorption occurs in the middle of the NR [44]. ...
Thanks to their tunable and strong interaction with light, plasmonic nanostructures have been investigated for a wide range of applications. In most cases, controlling the electric field enhancement at the metal surface is crucial. This can be achieved by controlling the metal nanostructure size, shape, and location in three dimensions, which is synthetically challenging. Electrochemical methods can provide a reliable, simple, and cost-effective approach to nanostructure metals with a high degree of geometrical freedom. Herein, we review the use of electrochemistry to synthesize metal nanostructures in the context of plasmonics. Both template-free and templated electrochemical syntheses are presented, along with their strengths and limitations. While template-free techniques can be used for the mass production of low-cost but efficient plasmonic substrates, templated approaches offer an unprecedented synthetic control. Thus, a special emphasis is given to templated electrochemical lithographies, which can be used to synthesize complex metal architectures with defined dimensions and compositions in one, two and three dimensions. These techniques provide a spatial resolution down to the sub-10 nanometer range and are particularly successful at synthesizing well-defined metal nanoscale gaps that provide very large electric field enhancements, which are relevant for both fundamental and applied research in plasmonics.
EELS, SERS and electromagnetic simulations demonstrate large E-field enhancements at Rh segments located in the gap region of AuRh_Au nanorod heterodimers.
