Fabrication and Optical Properties of Gold Semishells

Abstract

Gold (Au) nanoshells are known to exhibit many attractive optical properties caused by the excitation of localized surface plasmon resonances (LSPRs). Reducing the symmetry of these nanoshells has a number of interesting consequences, such as exciting different plasmon modes, making the optical response angle-dependent, and enhancing the local electric field intensity. In this paper, a versatile procedure involving ion milling has been developed to fabricate reduced-symmetrical Au semishells. This allows us to precisely control the reduced-symmetrical geometry and, particularly, the upward orientation of the created nanoaperture. These features, along with a combination of finite different time domain (FDTD) calculations, suggest Au semishell monolayer structures for a potential application in surface-enhanced Raman spectroscopy (SERS)-based biomolecule detection. Au semishells, additionally, exhibit advantageous features over Au nanoshells, for example, a more pronounced red shift of LSPR bands by tuning the aspect ratio, a larger tuning range of optical properties, increased optical absorption at higher wavelengths, and an enhanced local electromagnetic field.

Dual Symmetry Breaking in Gold-Silica-Gold Multilayer Nanoshells

“…As the cutoff height increases, the dipolar mode |ω // − 〉 1 and the quadrupolar mode |ω // − 〉 2 red shift, while the dipolar mode |ω // + 〉 1 exhibits nearly no shift. As the previous work shows [20,25], with the decrease in hole size (increase in cutoff height), the energy of the transverse modes |ω ⊥ o 〉 1 of nanocup increases and the mode |ω ⊥ o 〉 1 blue shifts, whereas the energy of the axial modes |ω // o 〉 1 of nanocup reduces and the mode |ω // o 〉 1 red shifts. Similar to the plasmon hybridization in Au-silica-Au nanoshells [6], the antisymmetric dipolar coupling modes |ω ⊥ Fig.…”

“…The nanostructures of shell cutting include the nanocap [19], the nanocup [20][21][22], and the perforated Ausilica-Au multilayer nanoshells [23], and so on. The shellcutting nanostructures can be fabricated by anisotropic etching [24,25] or template deposition [19]. This type of Electronic supplementary material The online version of this article (doi:10.1007/s11468-014-9750-z) contains supplementary material, which is available to authorized users.…”

“…Nonconcentric morphology of Au-silica-Au multilayer nanoshells was obtained by the nonuniform growth of a thin SiO 2 layer (10-20 nm) in chemical synthesis [15]. After functionally immobilizing these nanoparticles on the substrate to form a monolayer [27], the DSMNS nanoparticles can be achieved by anisotropic etching (such as ion milling) [25,27] on this asymmetric Au-silica-Au multilayer shells monolayer.…”

Tunable optical features from self-organized rhodium nanostructures

“…Conversely, the departure from sphericity due to asymmetry in the field of nanoparticles or presence of disordered ͑anisotropic͒ morphology can have a "diffuse" response resulting in a splitting of their dipole absorbance in to multiple bands. 2,3 These advances in the understanding of surface plasmon behavior of nanoparticles have indeed, provided several promising solutions for the confinement of light below their diffraction limit enabling 4,5 several technological breakthroughs including chemical and biochemical sensors, 6 plasmonics, 7 solar cells and lighting, 8 cancer treatments, 9 near-field optical microscopy, 10 etc. For example, the optical properties of Au and Ag nanostructures have been known for nearly 150 years, culminating in the niche application of their SPR in various fields.…”

“…In situ UV-visible experiments were performed using the above-mentioned procedure for understanding the growth kinetics. Further, to see the effect of Cl − ions on the absorption peaks of in situ formed Rh nanospheres, we have investigated SPR after the addition of 0.5 M RhCl 3 and Al using time dependent UV analysis. Figure 2 illustrates the emergence of two surface plasmon peaks at 375 nm and 474 nm, respectively, due to the difference in the surface roughness of these nanospheres, as can be evident from the associated transmission electron microscopy ͑TEM͒ images.…”