title: Self-assembled large Au nanoparticle arrays with regular hot spots for SERS.
abstract: The cost-effective self-assembly of 80 nm Au nanoparticles (NPs) into large-domain, hexagonally close-packed arrays for high-sensitivity and high-fidelity surface-enhanced Raman spectroscopy (SERS) is demonstrated. These arrays exhibit specific optical resonances due to strong interparticle coupling, which are well reproduced by finite-difference time-domain (FDTD) simulations. The gaps between NPs form a regular lattice of hot spots that enable a large amplification of both photoluminescence and Raman signals. At smaller wavelengths the hot spots are extended away from the minimum-gap positions, which allows SERS of larger analytes that do not fit into small gaps. Using CdSe quantum dots (QDs) a 3-5 times larger photoluminescence enhancement than previously reported is experimentally demonstrated and an unambiguous estimate of the electromagnetic SERS enhancement factor of ≈10(4) is obtained by direct scanning electron microscopy imaging of QDs responsible for the Raman signal. Much stronger enhancement of ≈10(8) is obtained at larger wavelengths for benzenethiol molecules penetrating the NP gaps.
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, IL 60439, USA. aiqingchen@anl.gov.
authors.forename: Aiqing
authors.initials: A
authors.lastname: Chen
authors.forename: A Eugene
authors.initials: AE
authors.lastname: DePrince
authors.forename: Arnaud
authors.initials: A
authors.lastname: Demortière
authors.forename: Alexandra
authors.initials: A
authors.lastname: Joshi-Imre
authors.forename: Elena V
authors.initials: EV
authors.lastname: Shevchenko
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Gray
authors.forename: Ulrich
authors.initials: U
authors.lastname: Welp
authors.forename: Vitalii K
authors.initials: VK
authors.lastname: Vlasko-Vlasov