title: Tuning and maximizing the single-molecule surface-enhanced Raman scattering from DNA-tethered nanodumbbells.
abstract: We extensively study the relationships between single-molecule surface-enhanced Raman scattering (SMSERS) intensity, enhancement factor (EF) distribution over many particles, interparticle distance, particle size/shape/composition and excitation laser wavelength using the single-particle AFM-correlated Raman measurement method and theoretical calculations. Two different single-DNA-tethered Au-Ag core-shell nanodumbbell (GSND) designs with an engineerable nanogap were used in this study: the GSND-I with various interparticle nanogaps from ∼4.8 nm to <1 nm or with no gap and the GSND-II with the fixed interparticle gap size and varying particle size from a 23-30 nm pair to a 50-60 nm pair. From the GSND-I, we learned that synthesizing a <1 nm gap is a key to obtain strong SMSERS signals with a narrow EF value distribution. Importantly, in the case of the GSND-I with <1 nm interparticle gap, an EF value of as high as 5.9 × 10(13) (average value = 1.8 × 10(13)) was obtained and the EF values of analyzed particles were narrowly distributed between 1.9 × 10(12) and 5.9 × 10(13). In the case of the GSND-II probes, a combination of >50 nm Au cores and 514.5 nm laser wavelength that matches well with Ag shell generated stronger SMSERS signals with a more narrow EF distribution than <50 nm Au cores with 514.5 nm laser or the GSND-II structures with 632.8 nm laser. Our results show the usefulness and flexibility of these GSND structures in studying and obtaining SMSERS structures with a narrow distribution of high EF values and that the GSNDs with < 1 nm are promising SERS probes with highly sensitive and quantitative detection capability when optimally designed.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 151-747, South Korea.
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Jwa-Min
authors.initials: JM
authors.lastname: Nam
authors.forename: Ki-Seok
authors.initials: KS
authors.lastname: Jeon
authors.forename: Dong-Kwon
authors.initials: DK
authors.lastname: Lim
authors.forename: Hyoki
authors.initials: H
authors.lastname: Kim
authors.forename: Sunghoon
authors.initials: S
authors.lastname: Kwon
authors.forename: Haemi
authors.initials: H
authors.lastname: Lee
authors.forename: Yung Doug
authors.initials: YD
authors.lastname: Suh
mesh_terms: D004247:DNA / Q000032:analysis / Q000737:chemistry* / Q000235:genetics*; D053768:Metal Nanoparticles / Q000737:chemistry*; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D004247:DNA