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Volumn 5, Issue 1, 2005, Pages 119-124

Nanophotonic crescent moon structures with sharp edge for ultrasensitive biomolecular detection by local electromagnetic field enhancement effect

Author keywords

[No Author keywords available]

Indexed keywords

BIOMOLECULAR DETECTION; ELECTROMAGNETIC FIELD ENHANCEMENT; NANOPHOTONIC CRESCENT MOON STRUCTURES; SHARP EDGE;

EID: 12844275925     PISSN: 15306984     EISSN: None     Source Type: Journal    
DOI: 10.1021/nl048232+     Document Type: Article
Times cited : (448)

References (31)
  • 21
    • 12844274934 scopus 로고    scopus 로고
    • note
    • Glass slides were thoroughly rinsed with deionized water (Millipore, > 18 MΨ) and dried under a stream of nitrogen gas. A thin layer of photoresist (Shipley S1818, Shipley, MA) was spin-coated on the cleaned glass substrates. Aqueous solutions of polystyrene colloids (300 nm; Duke Scientific, CA) were diluted in water to a volume fraction of 0.1%. A monolayer of sacrificial nanospheres was generated by drop-casting the dilute solution of the polystyrene colloids and allowed to dry overnight in a clean zone hood to minimize contamination of the samples by dust, and to stabilize the rate of evaporation. After the arrays of beads dried, a thin gold film was deposited by conventional electron beam evaporation. The sample substrate was placed above the gold source with certain tilt angle (∼30 °), and the angle can be adjusted ranging from 0° to 45°. The substrate rotates at a constant speed (∼60 rpm) during the deposition. The thickness at the bottom of the bowl is measured using TEM to be ∼100 nm. The shape of nanocrescent moons depends on the deposition thickness, angle, and the size of the sacrificial nanosphere template. The gold-coated colloids were released from the glass support into an aqueous suspension by lift-off with acetone. Next the gold-coated polymer nanospheres were collected by centrifugation (∼5000 rpm, 5-10 min) and were suspended in toluene to dissolve the polystyrene. The sample was then centrifuged and washed 3-4 times in water. The gold nanocrescent moons were collected and resuspended in water or ethanol to form diluted colloids that were subsequently dropped on a 100 μm thick glass substrate for spectrum measurement.
  • 23
    • 12844250585 scopus 로고    scopus 로고
    • note
    • A microscopy system combining dark-field scattering imaging and Raman spectroscopy is used to find "hot spots" and acquire Raman scattering spectra of R6G molecules adsorbed on a single gold nanocrescent moon. The system consist of a Carl Zeiss Axiovert 200 inverted microscope (Carl Zeiss, Germany) equipped with a darkfield condenser (1.2 < NA < 1.4), a true-color digital camera (CoolSNAP cf, Roper Scientific, NJ), and a 300 mm focal-length monochromator (Acton Research, MA) with a 1024 × 256-pixel cooled spectrograph CCD camera with compensation in ultraviolet and near-infrared region (Roper Scientific, NJ). A 2 μm wide aperture is placed in front of the entrance slit of the monochromator to keep only a single nanocrescent moon in the region of interest. The true-color scattering images of gold nanocrescent moons are taken using a 60 × objective lens (NA = 0.8) and the true-color camera with a white light illumination by a 100 W halogen lamp. The scattering spectra of gold nanocrescent moons are taken in visible light and infrared light regions separately, normalized with respect to the spectrum of a nonresonant nanoparticle (i.e., polystyrene) after the subtraction of background, then combined and normalized to unity. A 785 nm diode laser is used in our experiments as the excitation source of Raman scattering, and the laser beam (after attenuating neutral density filter) is focused by the same objective lens on single nanocrescent moon. The scattering and reflection light is then collected through the same optical pathway as the incident light and then through two 797 nm long-pass Raman filters (optical density > 6 below 797 nm and transmission > 90% above 800 nm, Omega Filters, VT). The Raman scattering light is resolved by a blaze grating of 300 grooves/mm and imaged by the spectrograph CCD.
  • 28
    • 12844257395 scopus 로고    scopus 로고
    • note
    • -7 × 10) = 6020 (∼6000).
  • 29
    • 12844281055 scopus 로고    scopus 로고
    • note
    • 5 can be obtained.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.