Electromagnetic behavior of dielectric objects on metallic periodically nanostructured substrates

Abstract

In this research, we investigate the electromagnetic behavior of a metallic thin-film with a periodic array of subwavelength apertures when dielectric objects are located on it. The influence of size, geometry and optical properties of the objects on the transmission spectra is numerically analyzed. We study the sensitivity of this system to changes in the refractive index of the illuminated volume induced by the presence of objects with sizes from hundreds of nanometers (submicron-sized objects) to a few microns (micron-sized objects). Parameters such as the object volume within the penetration depth of the surface plasmon in the buffer medium or the contact surface between the object and the nanostructured substrate strongly affect the sensitivity. The proposed system models the presence of objects and their detection through the spectral shifts undergone by the transmission spectra. Also, we demonstrate that these can be used for obtaining information about the refractive index of a micron-sized object immersed in a buffer and located on the nanostructured sensitive surface. We believe that results found in this study can help biomedical researchers and experimentalists in the process of detecting and monitoring biological organisms of large sizes (notably, cells).

Applications of Hybrid Metal‐Dielectric Nanostructures: State of the Art

“…This resonant behavior generates strong enhancements of the electric field (hot spots) in the proximity (near-field regime) of the metallic structure. Both enhancement and confinement effects find applications in many different areas, [1] like sensing (contamination, biomedicine), [23][24][25][26][27][28][29][30][31][32][33][34][35][36] material analysis-like SERS, [37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54] Förster resonance energy transfer (FRET), [55,56] surface enhanced fluorescence scattering (SEFS), [57][58][59][60][61] nonlinear optics, [62][63][64] absorption spectroscopy, [44,65,66] solar cells [67,…”

“…This resonant behavior generates strong enhancements of the electric field (hot spots) in the proximity (near‐field regime) of the metallic structure. Both enhancement and confinement effects find applications in many different areas, [ 1 ] like sensing (contamination, biomedicine), [ 23–36 ] material analysis—like SERS, [ 37–54 ] Förster resonance energy transfer (FRET), [ 55,56 ] surface enhanced fluorescence scattering (SEFS), [ 57–61 ] nonlinear optics, [ 62–64 ] absorption spectroscopy, [ 44,65,66 ] solar cells [ 67,68 ] ), or optical communications. [ 47,69–71 ] To enhance the intensity of the electric field, aggregates of NPs, particularly dimers, two particles separated by a nanogap, or bow tie antennas have been suggested.…”

Optical inspection of manufactured nanohole arrays to bridge the lab-industry gap

“…Once it is measured it can be attached to the film and characterizes it for further uses. When the films are used as biosensors, it also maps their plasmonic performance and sets the background signal for detecting, for instance, micron-sized biological material (cells) distributed non-homogeneously on its surface [12,31].…”

“…Since the lack of homogeneity in some of the nano-features may lead to undesirable optical responses [11], their characterization and further quality-control is of paramount importance for their mass production. This is particularly important when micron-sized biological material is located at specific places on the sensing chip surface [7,12].…”

Plasmonic Biosensing for Label-Free Detection of Two Hallmarks of Cancer Cells: Cell-Matrix Interaction and Cell Division

“…EOT in metallic nanohole films is being explored as a tool for personalized medicine through the label-free analysis of live cells [ 15 , 16 ] because the EOT-based biosensors can reveal subtle changes in the interactions between the cells and the nanostructured films within the penetration depth of the excited plasmons [ 5 , 17 , 18 ]. The EOT-based techniques are suited to sense the outer layer of cells because the thickness of the plasmon penetration depth, for gold nanostructured films, is about 200 nm [ 19 ]. This region includes the actin cortex, which plays an important role in cellular processes such as cell division, cell migration and tumor cell invasion [ 20 , 21 ] by means of actin polymerization–depolymerization mechanisms.…”