The SERS Activity of a Supported Ag Nanocube Strongly Depends on Its Orientation Relative to Laser Polarization

McLellan, Joseph M.; Li, † Zhi-Yuan; Siekkinen, and Andrew R.; Xia, Younan

doi:10.1021/nl070157q

Cited by 333 publications

(321 citation statements)

References 43 publications

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“…For the cube tag, we found that the 4-MBA signal from a cube orientated with a side diagonal axis parallel to the laser polarization was about two times higher than the configuration when the cube was oriented with one of the edges parallel to the laser polarization. This observation is consistent with the results for Ag nanocubes obtained in our previous work [42]. It can be concluded that the intensities of 4-MBA signals from individual tags supported on glass slides decreased in the order of dimer tag ( parallel) ) cube tag ðdiagonalÞ .…”

Section: Surface-enhanced Raman Scattering Properties Of the Dimer Tagsupporting

confidence: 92%

“…Therefore, it should give the strongest SERS signals. Hot spots could also be created at the corner sites of a cubic core of the cube tags [42,46], leading to a higher EF than the sphere tags with spherical cores. Because the three types of tags had a similar major LSPR peak (figure 2d ), the possibility of wavelength-dependent enhancement [43], where the SERS activity is maximized when the excitation source matched the LSPR peak of the tags, could be neglected.…”

Section: Surface-enhanced Raman Scattering Properties Of the Dimer Tagmentioning

confidence: 99%

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Silica-coated dimers of silver nanospheres as surface-enhanced Raman scattering tags for imaging cancer cells

Xia

2013

Interface Focus.

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One contribution of 10 to a Theme Issue 'Molecular-, nano-and micro-devices for real-time in vivo sensing'. Surface-enhanced Raman scattering (SERS) tags have been actively explored as a multiplexing platform for sensitive detection of biomolecules. Here, we report a new type of SERS tags that was fabricated by sequentially functionalizing dimers made of 50 nm Ag nanospheres with 4-mercaptobenzoic acid as the Raman reporter molecule, silica coating as a protective shell and antibody as a targeting ligand. These dimer-based tags give highly enhanced and reproducible Raman signals owing to the presence of a well-defined SERS hot spot at the junction between two Ag nanospheres in the dimer. The SERS enhancement factor (EF) of an individual dimer tag supported on a glass slide can reach a level as high as 4.3 Â 10 6 . In comparison, the EFs dropped to 2.8 Â 10 5 and 8.7 Â 10 5 , respectively, when Ag nanospheres and nanocubes with sizes similar to the spheres in the dimer were used to fabricate the tags using similar procedures. The SERS signals from aqueous suspensions of the dimer-based tags also showed high intensity and good stability. Potential use of the dimer-based tags was demonstrated by imaging cancer cells overexpressing HER2 receptors with good specificity and high sensitivity.

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Section: Surface-enhanced Raman Scattering Properties Of the Dimer Tagsupporting

confidence: 92%

Section: Surface-enhanced Raman Scattering Properties Of the Dimer Tagmentioning

confidence: 99%

Silica-coated dimers of silver nanospheres as surface-enhanced Raman scattering tags for imaging cancer cells

Xia

2013

Interface Focus.

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“…Because of the anisotropic structure of the GNRs, two plasmon resonance bands are induced by the transverse and longitudinal oscillations of free electrons 29 . Note that the SERS intensities depend strongly on both the orientation of the GNRs and the illumination direction of the laser 18,28,30 . When the long axis of the GNRs is perpendicular to the illumination direction of the incident light, a resonance condition in a far-field regime is satisfied resulting in significant amplification of the Raman signal ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Interfacial liquid-state surface-enhanced Raman spectroscopy

et al. 2013

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Oriented assemblies of functional nanoparticles, with the aid of external physical and chemical driving forces, have been prepared on two-dimensional solid substrates. It is challengeable, however, to achieve three-dimensional assembly directly in solution, owing to thermal fluctuations and free diffusion. Here we describe the self-orientation of gold nanorods at an immiscible liquid interface (that is, oleic acid-water) and exploit this novel phenomenon to create a substrate-free interfacial liquid-state surface-enhanced Raman spectroscopy. Dark-field imaging and Raman scattering results reveal that gold nanorods spontaneously adopt a vertical orientation at an oleic acid-water interface in a stable trapping mode, which is in good agreement with simulation results. The spontaneous vertical alignment of gold nanorods at the interface allows one to accomplish significant additional amplification of the Raman signal, which is up to three to four orders of magnitude higher than that from a solution of randomly oriented gold nanorods.

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“…[7] The strong dependence on laser polarization could be attributed to the difference in the electric field enhancements under different excitation directions. [15] When comparing the EF of a dimer and that of a single sphere, we found that the EF of an individual sphere was much lower than that of the corresponding dimer, indicating the hotspot phenomenon. Besides, the EF (1.7×10 8 ) for a dimer of 80-nm spheres with the laser polarization parallel to the dimer's long axis is almost ten times higher than that of the dimer of 30-nm spheres.…”

mentioning

confidence: 87%

Etching and Dimerization: A Simple and Versatile Route to Dimers of Silver Nanospheres with a Range of Sizes

Li¹,

Camargo²,

Au³

et al. 2009

Angewandte Chemie

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This paper describes a facile method that generates dimers of Ag nanospheres by etching Ag nanocubes with Fe(NO 3 ) 3 in ethanol with the assistance of poly(vinyl pyrrolidone) (PVP). During the etching process, the corners and edges of the Ag nanocubes were truncated off to generate spherical particles, accompanied by dimerization as a result of reduction in colloidal stability due to the addition of ionic species. Both ethanol and PVP play an important role in the etching and dimerization processes. By starting with Ag nanocubes of different sizes, we obtained welldefined dimers of Ag spheres 40, 63, and 80 nm in diameter with percentages of dimerization >60%. Since this approach can be used to fabricate dimers of Ag nanospheres with a range of different sizes, it allows for a systematic study of the hot-spot phenomenon in SERS. By correlating with SEM imaging, we measured the SERS enhancement factors for individual dimers from the three different samples, and an average value of 3.9×10 7 , 9.3×10 7 , and 1.7×10 8 was obtained, respectively.

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The SERS Activity of a Supported Ag Nanocube Strongly Depends on Its Orientation Relative to Laser Polarization

Cited by 333 publications

References 43 publications

Silica-coated dimers of silver nanospheres as surface-enhanced Raman scattering tags for imaging cancer cells

Silica-coated dimers of silver nanospheres as surface-enhanced Raman scattering tags for imaging cancer cells

Interfacial liquid-state surface-enhanced Raman spectroscopy

Etching and Dimerization: A Simple and Versatile Route to Dimers of Silver Nanospheres with a Range of Sizes

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