Theoretical Simulation and Focused Ion Beam Fabrication of Gold Nanostructures for Surface-Enhanced Raman Scattering (SERS)

Dhawan, Anuj; Gerhold, Michael; Vo‐Dinh, Tuan

doi:10.1007/s12030-008-9017-x

Cited by 35 publications

(20 citation statements)

References 21 publications

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“…Due to the well-established strengths of SERS including a lack of photobleaching/photodegradation, the ability to perform multiplexed bioanalysis using a single laser wavelength, and narrow spectral width of Raman bands, the multiplexing capability of Raman and SERS techniques is excellent in comparison to the other spectroscopic alternatives, thus opening new horizons to many applications in medical diagnostics, environmental exposure assessment, drug development and high throughput screening. Improved knowledge of the plasmonics effect and advances in theoretical calculation and simulation studies of the electromagnetic enhancements [33, 50–53] will lead to the design and fabrication of plasmonics-active nanostructures with optimal enhancement properties.…”

Section: Discussionmentioning

confidence: 99%

Plasmonic nanoprobes for SERS biosensing and bioimaging

Vo‐Dinh¹,

Wang

Scaffidi

2009

Journal of Biophotonics

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This article provides an overview of the development and application of plasmonic nanoprobes developed in our laboratory for biosensing and bioimaging. We describe the use of plasmonics surface-enhanced Raman scattering (SERS) gene probes for the detection of diseases using DNA hybridization to target biospecies (HIV gene, breast cancer genes etc.). For molecular imaging, we describe a hyperspectral surface-enhanced Raman imaging (HSERI) system that combines imaging capabilities with SERS detection to identify cellular components using Raman dye-labeled silver nanoparticles in cellular systems The detection of specific target DNA sequences associated with breast cancer using “molecular sentinel” nanoprobes and the use of a plasmonic nanosensor to monitor pH in single cells are presented and discussed. Plasmonic nanosensors and nanoprobes have been developed as sensitive and selective tolls for environmental monitoring, cellular biosensing, medical diagnostics and high throughput screnning.

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Section: Discussionmentioning

confidence: 99%

Plasmonic nanoprobes for SERS biosensing and bioimaging

Vo‐Dinh¹,

Wang

Scaffidi

2009

Journal of Biophotonics

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201

122

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“…The FDTD software uses the Lorentz-Drude dispersion 51–52, 79 model described above in Section 3.1. In the FDTD calculations, a continuous plane wave (633-nm for simulating the laser employed for SERS measurements) propagating in the z direction and having the electric field (E-field) polarized in the x direction was incident on the gold-coated silicon nanowire structures.…”

Section: 0 Results and Discussionmentioning

confidence: 99%

Plasmonic Nanoparticles and Nanowires: Design, Fabrication and Application in Sensing

et al. 2010

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This study involves two aspects of our investigations of plasmonics-active systems: (i) theoretical and simulation studies and (ii) experimental fabrication of plasmonics-active nanostructures. Two types of nanostructures are selected as the model systems for their unique plasmonics properties: (1) nanoparticles and (2) nanowires on substrate. Special focus is devoted to regions where the electromagnetic field is strongly concentrated by the metallic nanostructures or between nanostructures. The theoretical investigations deal with dimers of nanoparticles and nanoshells using a semi-analytical method based on a multipole expansion (ME) and the finite-element method (FEM) in order to determine the electromagnetic enhancement, especially at the interface areas of two adjacent nanoparticles. The experimental study involves the design of plasmonics-active nanowire arrays on substrates that can provide efficient electromagnetic enhancement in regions around and between the nanostructures. Fabrication of these nanowire structures over large chip-scale areas (from a few millimeters to a few centimeters) as well as FDTD simulations to estimate the EM fields between the nanowires are described. The application of these nanowire chips using surface-enhanced Raman scattering (SERS) for detection of chemicals and labeled DNA molecules is described to illustrate the potential of the plasmonics chips for sensing.

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“…This process is also not conducive to fabrication of SERS substrates over a large area, specifically 6-inch wafers. Moreover, the smallest sizes of nano-scale gaps between metallic nano-structures using electron beam lithography and FIB are greater than ~ 10-15 nm 29 . Although SERS based substrates based on disordered metallic nanowires, ordered metallic nanowires, as well as metal-coated silicon or germanium oxide nanowires have been described in the past literature, the ability to reproducibly develop ordered metallic nanowires with controlled sizes, shapes, and sub-10 nm gaps between the nanowires has not been presented previously.…”

Section: Introductionmentioning

confidence: 99%

“…An earlier work in our laboratory has involved the development of planar solid substrates covered with a monolayer of nanospheres that are coated with a thin layer of silver, thus producing a plasmonics-active 2D nanospheres arrays 13 . Recently, Vo-Dinh et al 29 reported the formation of metallic nanostructures on planar substrates and tips of optical fibers by employing focused ion beam milling (FIB). This process is also not conducive to fabrication of SERS substrates over a large area, specifically 6-inch wafers.…”

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confidence: 99%

Fabrication of novel plasmonics-active substrates

Dhawan

Gerhold

et al. 2009

SPIE Proceedings

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This paper describes methodologies for fabricating of highly efficient plasmonics-active SERS substrates -having metallic nanowire structures with pointed geometries and sub-5 nm gap between the metallic nanowires enabling concentration of high EM fields in these regions -on a wafer-scale by a reproducible process that is compatible with large-scale development of these substrates. Excitation of surface plasmons in these nanowire structures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. The methodologies employed included metallic coating of silicon nanowires fabricated by employing deep UV lithography as well as controlled growth of silicon germanium on silicon nanostructures to form diamond-shaped nanowire structures followed by metallic coating. These SERS substrates were employed for detecting chemical and biological molecules of interest. In order to characterize the SERS substrates developed in this work, we obtained SERS signals from molecules such as p-mercaptobenzoic acid (pMBA) and cresyl fast violet (CFV) attached to or adsorbed on the metal-coated SERS substrates. It was observed that both gold-coated triangular shaped nanowire substrates as well as gold-coated diamond shaped nanowire substrates provided very high SERS signals for the nanowires having sub-15 nm gaps and that the SERS signal depends on the closest spacing between the metal-coated silicon and silicon germanium nanowires. SERS substrates developed by the different processes were also employed for detection of biological molecules such as DPA (Dipicolinic Acid), an excellent marker for spores of bacteria such as Anthrax. IntroductionIn recent years, there has been extensive research aimed at developing plasmonics-active substrates that generate high surface enhanced Raman scattering (SERS) signals resulting in high sensitivities and specificities towards chemical and biological molecules adsorbed on the substrates 1-20 . The advantage of employing SERS as a sensing platform is that SERS spectra exhibit narrow spectral features characteristic of the detected analyte species which allows label-free and specific detection of these species in the presence of multiple other molecules in complex mixtures. Raman scattering can be described as an inelastic light scattering process in which a target sample on which light is incident absorbs one photon and emits another photon at the same time, the second photon being either at a lower frequency (i.e. Stokes scattering) or at a higher frequency (i.e. Anti-Stokes scattering) than the incident light frequency. While Raman scattering cross-sections are extremely small -typically between 10 -30 to 10 -25 cm 2 per molecule -thereby limiting its ability to detect the analyte species, Surface enhanced Raman scattering (SERS) increases the Raman scattering cross-section substantially enabling the application of this process for extremely sensitive and specific detection of the analytes 1-3 . Reports on the large SE...

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Theoretical Simulation and Focused Ion Beam Fabrication of Gold Nanostructures for Surface-Enhanced Raman Scattering (SERS)

Cited by 35 publications

References 21 publications

Plasmonic nanoprobes for SERS biosensing and bioimaging

Plasmonic nanoprobes for SERS biosensing and bioimaging

Plasmonic Nanoparticles and Nanowires: Design, Fabrication and Application in Sensing

Fabrication of novel plasmonics-active substrates

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