arXiv subjects

Emese Toth

Publications and source records attributed to Emese Toth.

4 recordsLinked to original sources

arXiv2020

Spectral engineering via complex patterns of circular nano-object miniarrays: I. convex patterns tunable by integrated lithography realized by circularly polarized light

Illumination of colloid sphere monolayers by circularly polarized beams enables the fabrication of concave patterns consisting of circular nanohole miniarrays that can be transferred into convex metal nanoparticle patterns via a lift-off procedure. Unique spectral and near-field properties are achievable by tuning the geometry of the central nanoring and quadrumer of slightly rotated satellite nanocrescents and by selecting those azimuthal orientations that promote localized plasmon resonances. The spectral and near-field effects of hexagonal patterns made of uniform gold nanorings and nanocrescents, that can be prepared by transferring masks fabricated by a perpendicularly and obliquely incident single homogeneous circularly polarized beam, were studied to uncover the supported localized plasmonic modes. Artificial rectangular patterns made of a singlet nanoring and singlet nanocrescent as well as quadrumer of four nanocrescents were investigated to analyze the role of nano-object interactions and lattice type. It was proven that all nanophotonical phenomena are governed by the azimuthal orientation independent localized resonance on the nanorings and by the C2, C1 and U resonances on the nanocrescents in case of $\bar{E}$-field oscillation direction perpendicular and parallel to their symmetry axes. The interaction between localized surface plasmon resonances on individual nano-objects is weak, whereas scattered photonic modes have a perturbative role at the Rayleigh anomaly only on the larger periodic rectangular pattern of miniarrays. Considerable fluorescence enhancement of dipolar emitters is achievable at spectral locations promoting the C and U resonances on the composing nano-objects.

physics.optics↗

arXiv2020

Spectral engineering via complex patterns of circular nano-object miniarrays: II. concave patterns tunable by integrated lithography realized by circularly polarized light

Application of circularly polarized beams in interferometric illumination of colloid sphere monolayers enables the direct fabrication of rectangular patterns consisting of circular nanohole miniarrays in metal films. The spectral and near-field effects of complex rectangular patterns made of a central nanoring and slightly rotated satellite nanocrescents were studied in azimuthal orientations promoting the localized and propagating plasmon's coupling. To inspect the localized modes separately, spectral responses and near-field phenomena of hexagonal patterns composed of uniform nanorings and nanocrescents, that can be fabricated by a perpendicularly and obliquely incident single homogeneous circularly polarized beam, were investigated. To uncover the interaction of localized and propagating modes, artificial rectangular patterns composed of a singlet nanoring, singlet horizontal nanocrescent and quadrumer of four slightly rotated nanocrescents were analyzed. It was demonstrated that the interacting C2 and C1 localized resonances on the (approximately) horizontal nanocrescents in C orientation (($16^{\circ}$) $0^{\circ}$ azimuthal angle) and the azimuthal orientation (in)dependent localized resonance on the (nanorings) nanocrescents coupled with propagating surface plasmon polaritons (close to) in U orientation (($106^{\circ}$)$90^{\circ}$ azimuthal angle) result in similar split spectra. The spectral response of the complex miniarray pattern can be precisely tuned by varying the geometrical parameters of the moderately interacting nanoholes and the pattern period. Enhancement of dipolar emitter's fluorescence is demonstrated in appropriate configurations that have a potential application in bio-object detection.

physics.optics↗

arXiv2020

Mapping fluorescence enhancement of plasmonic nanorod coupled dye molecules

Plasmonically enhanced fluorescence is a widely studied and applied phenomenon, however only a comparative theoretical and experimental analyses of coupled fluorophores and plasmonic nanoresonators makes it possible to uncover, how this phenomenon can be controlled. A numerical optimization method was applied to design configurations that are capable of resulting in an enhancement of excitation and emission, moreover of both phenomena simultaneously in coupled Cy5 dye molecule and gold nanorod systems. Parametric sensitivity studies revealed, how the fluorescence enhancement depends on the molecule's location, distance and orientation. Coupled systems designed for simultaneous improvement exhibited the highest (intermediate directional) total fluorescence enhancement, which is accompanied by intermediate sensitivity to the molecule's parameters, except the location and orientation sensitivity at the excitation wavelength. Gold nanorods with a geometry corresponding to the predicted optimal configurations were synthesized, and DNA strands were used to control the Cy5 dye molecule distance from the nanorod surface via hybridization of the Cy5-labelled oligonucleotide. State-of-the-art dSTORM microscopy was used to accomplish a proof-of-concept experimental demonstration of the theoretically predicted (directional) total fluorescence enhancement. The measured fluorescence enhancement was in good agreement with theoretical predictions, thus providing a complete kit to design and prepare coupled nanosystems exhibiting plasmonically enhanced fluorescence.

physics.optics↗

arXiv2016

Detection of biomolecules and bioconjugates by monitoring rotated grating-coupled surface plasmon resonance

Plasmonic biosensing chips were prepared by fabricating wavelength-scaled dielectric-metal interfacial gratings on polymer film covered bimetal layers. Lysozyme biomolecules (LYZ) and gold nanoparticle bioconjugates (AuNP-LYZ) with 1:5 mass ratio were seeded onto the biochip surfaces. Comparison of the reflectance curves measured in a modified Kretschmann arrangement and computed numerically proved that monitoring the narrower secondary peaks under optimal rotated-grating coupling condition makes it possible to achieve enhanced sensitivity in biodetection. The enlarged resonance peak shift is due to the horizontally and vertically antisymmetric long-range plamonic modes propagating at the edge of the valleys and hills, which originate from Bragg scattered surface plasmon polaritons. The sensitivity is further increased in case of bioconjugates due to the coupled localized resonances on Au NPs.

physics.optics↗