Gold Nanostars For Surface-Enhanced Raman Scattering: Synthesis, Characterization and Optimization

Khoury, Christopher G.; Vo‐Dinh, Tuan

doi:10.1021/jp8054747

Cited by 631 publications

(629 citation statements)

References 32 publications

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“…A broad variety of SERS substrates have been fabricated over the past decade, e.g. nanorods 8 , nanocubes 9 , nanostars 10 , various particle arrays [11][12][13][14][15][16] and silver dendrites 17 . Recently electric field (E-field) enhancement factors (EF) above 10 8 to even 10 10 have been reported.…”

Section: Introductionmentioning

confidence: 99%

Wafer-Scale Leaning Silver Nanopillars for Molecular Detection at Ultra-Low Concentrations

Rindzevicius

Schmidt

et al. 2015

J. Phys. Chem. C

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Wafer-scale surface-enhanced Raman scattering (SERS) substrates fabricated using maskless lithography are important for scalable production targets. Large-area, leaning silver-capped silicon nanopillar (Ag NP) structures suitable for SERS molecular detection at extremely low analyte concentrations are investigated. Theoretical results show that isolated Ag NPs essentially support two localized surface plasmon (LSP) modes. The most prominent LSP resonance is observed in the near-infrared region (~800 nm) and can be tuned by changing the diameter of the silicon nanopillars (Si NPs). The corresponding electric field distribution maps indicate that the maximum E-field enhancement is found at the Ag cavity, i.e. the bottom part of the Ag cap. We argue that the plasmon coupling between the resonant Ag cap cavities contributes most to the enhancement of the Raman signal. We experimentally evaluate these findings and show that by exposing Si NPs to an O 2 -plasma the average Ag NP cluster size, and thus the overall inter-pillar coupling, can be systematically reduced. We show that deposition of Cr adhesion layers on Si NPs (>3 nm) introduce plasmon coupling loss to the Ag NP LSP cavity mode that significantly reduces the SERS intensity. Results also show that short exposures to the O 2 -plasma and the use of 1-3 nm Cr adhesion layers are advantageous for reducing the signal background noise from Ag NPs. In addition, influence of the Ag NP height and Ag metal thickness on SERS intensities is investigated and optimal fabrication process parameters are evaluated. Finally, the SERS spectrum from 100 pM of trans-1,2-bis (4-pyridyl) ethylene (BPE) is recorded showing distinct characteristic Raman vibrational modes. The calculated enhancement factor is of the order of 10 8 , and the SERS signal intensity exhibits a standard deviation of around 14% (660 data points) across a 5x5 mm 2 surface area.

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Section: Introductionmentioning

confidence: 99%

Wafer-Scale Leaning Silver Nanopillars for Molecular Detection at Ultra-Low Concentrations

Rindzevicius

Schmidt

et al. 2015

J. Phys. Chem. C

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“…These efforts have resulted in reliable methods for the fabrication of plasmonic nanorods, nanocubes, nanostars, and nanoplatelets. [17][18][19][20] Cyanine dyes are another class of materials that have been extensively studied, due to their use in spectral sensitization and potential applications in novel optoelectronic materials. These dyes have a tendency to aggregate under reduced solubility conditions or when adsorption occurs on particle or substrate surfaces.…”

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confidence: 99%

Coherent Plasmon-Exciton Coupling in Silver Platelet-J-aggregate Nanocomposites

Miller²,

et al. 2015

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Hybrid nanostructures that couple plasmon and exciton resonances generate hybridized energy states, called plexcitons, which may result in unusual light-matter interactions. We report the formation of a transparency dip in the visible spectra of colloidal suspensions containing silver nanoplatelets and a cyanine dye, 1,1′-diethyl-2,2′-cyanine iodide (PIC). PIC was electrostatically adsorbed onto the surface of silver nanoplatelet core particles, forming an outer J-aggregate shell. This core−shell architecture provided a framework for coupling the plasmon resonance of the silver nanoplatelet core with the exciton resonance of the J-aggregate shell. The sizes and aspect ratios of the silver nanoplatelets were controlled to ensure the overlap of the plasmon and exciton resonances. As a measure of the plasmon-exciton coupling strength in the system, the experimentally observed transparency dips correspond to a Rabi splitting energy of 207 meV, among the highest reported for colloidal nanoparticles. The optical properties of the silver platelet-J-aggregate nanocomposites were supported numerically and analytically by the boundary-element method and temporal coupled-mode theory, respectively. Our theoretical predictions and experimental results confirm the presence of a transparency dip for the silver nanoplatelet core Jaggregate shell structures. Additionally, the numerical and analytical calculations indicate that the observed transparencies are dominated by the coupling of absorptive resonances, as opposed to the coupling of scattering resonances. Hence, we describe the suppressed extinction in this study as an induced transparency rather than a Fano resonance.

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“…An important example is herein reported by Chirea [20]. Gold nanostars are multibranched nanoparticles with multiple plasmon resonances, of which the lower energy ones, corresponding to the nanostar tips and core-tip interactions, are the most sensitive to environmental changes [21,22]. The electrocatalytic properties of gold nanostars could be also strongly influenced by their sensitivity to environmental changes.…”

Section: The Present Issuementioning

confidence: 95%

New Trends in Gold Catalysts

Liotta

2014

Catalysts

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Gold is an element that has fascinated mankind for millennia. The catalytic properties of gold have been a source of debate, due to its complete chemical inertness when in a bulk form, while it can oxidize CO at temperatures as low as ~200 K when in a nanocrystalline state, as discovered by Haruta in the late 1980s [1]. Since then, extensive activity in both applied and fundamental research on gold has been initiated. The importance of the catalysis by gold represents one of the fasted growing fields in science and is proven by the promising applications in several fields, such as green chemistry and environmental catalysis, in the synthesis of single-walled carbon nanotubes, as modifiers of Ni catalysts for methane steam and dry reforming reactions and in biological and electrochemistry applications. The range of reactions catalyzed by gold, as well as the suitability of different supports and the influence of the preparation conditions have been widely explored and optimized in applied research [2]. Gold catalysts appeared to be very different from the other noble metal-based catalysts, due to their marked dependence on the preparation method, which is crucial for the genesis of the catalytic activity. Several methods, including deposition-precipitation, chemical vapor deposition and cation adsorption, have been applied for the preparation of gold catalysts over reducible oxides, like TiO2. Among these methods, deposition-precipitation has been the most frequently employed method for Au loading, and it involves the use of tetrachloroauric (III) acid as a precursor. On the other hand, the number of articles dealing with Au-loaded acidic supports is smaller than that on basic supports, possibly because the deposition of [AuCl4]− or [AuOHxCl4−x]− species on acidic supports is difficult, due to their very low point of zero charge. Despite this challenge, several groups have reported the use of acidic zeolites as supports for gold. Zeolites are promising supports for Au stabilization, because of the presence of ion-exchange sites, such as NH4+, that can be substituted by Au+ ions through the elimination of NH4Cl [3]. Moreover, zeolites, due to their high thermal stability, the presence of a large surface area and micropores, may hinder Au sintering. [...]

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Gold Nanostars For Surface-Enhanced Raman Scattering: Synthesis, Characterization and Optimization

Cited by 631 publications

References 32 publications

Wafer-Scale Leaning Silver Nanopillars for Molecular Detection at Ultra-Low Concentrations

Wafer-Scale Leaning Silver Nanopillars for Molecular Detection at Ultra-Low Concentrations

Coherent Plasmon-Exciton Coupling in Silver Platelet-J-aggregate Nanocomposites

New Trends in Gold Catalysts

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