title: Extinction Coefficient of Gold Nanostars.
abstract: Gold nanostars (NStars) are highly attractive for biological applications due to their surface chemistry, facile synthesis and optical properties. Here, we synthesize NStars in HEPES buffer at different HEPES/Au ratios, producing NStars of different sizes and shapes, and therefore varying optical properties. We measure the extinction coefficient of the synthesized NStars at their maximum surface plasmon resonances (SPR), which range from 5.7 × 108to 26.8 × 108M-1cm-1. Measured values correlate with those obtained from theoretical models of the NStars using the discrete dipole approximation (DDA), which we use to simulate the extinction spectra of the nanostars. Finally, because NStars are typically used in biological applications, we conjugate DNA and antibodies to the NStars and calculate the footprint of the bound biomolecules.
authors.affiliation: Dept. of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.
authors.forename: Helena
authors.initials: H
authors.lastname: de Puig
authors.affiliation: Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge, MA USA 02139; Winchester Engineering Analytical Center, Food and Drug Administration. Winchester MA USA 01890.
authors.forename: Justina O
authors.initials: JO
authors.lastname: Tam
authors.affiliation: Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge, MA USA 02139; Winchester Engineering Analytical Center, Food and Drug Administration. Winchester MA USA 01890.
authors.forename: Chun-Wan
authors.initials: CW
authors.lastname: Yen
authors.affiliation: Institute for Medical Engineering and Science, Massachusetts Institute of Technology Cambridge, MA USA 02139; Dept. of Microbiology and Immunobiology, Harvard Medical School, Boston 02115.
authors.forename: Lee
authors.initials: L
authors.lastname: Gehrke
authors.affiliation: Dept. of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Hamad-Schifferli
keywords: DDA; DDSCAT; Gold nanostar; HEPES; discrete dipole approximation; molar extinction coefficient; multibranched gold nanoparticle; nanoflower; optical properties