Plasma-Induced Formation of Ag Nanodots for Ultra-High-Enhancement Surface-Enhanced Raman Scattering Substrates

Quantum Science Research, Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304, USA.
Langmuir (Impact Factor: 4.46). 05/2007; 23(9):5135-8. DOI: 10.1021/la063688n
Source: PubMed

ABSTRACT We report here plasma-induced formation of Ag nanostructures for surface-enhanced Raman scattering (SERS) applications. An array of uniform Ag patterned structures of 150 nm diameter was first fabricated on a silicon substrate with imprint lithography; then the substrate was further treated with an oxygen plasma to fracture the patterned structures into clusters of smaller, interconnected, closely packed Ag nanoparticles (20-60 nm) and redeposited Ag nanodots ( approximately 10 nm) between the clusters. The substrate thus formed had a uniform ultrahigh SERS enhancement factor (1010) over the entire substrate for 4-mercaptophenol molecules. By comparison, Au patterned structures fabricated with the same method did not undergo such a morphological change after the plasma treatment and showed no enhancement of Raman scattering.

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Available from: Zhiyong Li, Sep 29, 2015
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    • "The characteristic of LSPR depends on the composition, size, array structure, and shape of silver nanostructures and the dielectric environment [4] [5]. Ag nanostructures have been formed by various lithographic techniques [5] [6]. Ag nanostructure has led to many important applications pertaining to a sensor. "
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    ABSTRACT: Ag nanostructure has been widely used for optical sensing applications for localized surface plasmon resonance (LSPR). Many efforts have been tried to fabricate and control silver nanostructure. The pore diameter of the nanoporous alumina mask with through-holes was controlled by two-time dipping in 5 wt% phosphoric acid at 30°C. Using the nanoporous alumina mask as an evaporation mask, size-controlled Ag nanodot arrays were directly formed on indium-tin-oxide coated glass. With this process, Ag nanodot arrays with different size (42 nm, 60 nm, 80 nm) could be fabricated in periodic patterns with same separation distance of 105 nm. A large area Ag nanodot array was fabricated from the hard-won alumina mask. Their LSPR properties are examined by UV-vis extinction spectroscopy.
    Nanotechnology (IEEE-NANO), 2012 12th IEEE Conference on; 01/2012
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    • "Theoretical analysis and experimental data suggest that a separation of less than 5 nm between aggregated nanoparticles is necessary for strong SERS enhancement[22]. However, this scale of controlled separation is still beyond the resolution of any scalable top-down fabrication approach[23]. An alternate approach is to utilize self-assembled nanostructures that are uniform enough on a macro scale so that a reasonably enhanced and reproducible SERS signal can be obtained. "
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    ABSTRACT: Metallic nanorods synthesized by oblique angle deposition on glass substrate are utilized as nano-scale structures that can be coated with SERS active metal to allow for excitation of surface plasmons. The synthesized nanorods have an average length of ~500-600 nm and are randomly distributed on the substrate. The SERS studies with Near-IR excitation at 785 nm show significant enhancement with good uniformity to detect sub-monolayer concentrations of 4-methylbenzenethiol and 1,2-benzendithiol probe molecules. The simple synthesis and the reproducibility of SERS measurement make these substrates a promising candidate for trace level detection of biological and chemical species.
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