title: High quality gold nanorods and nanospheres for surface-enhanced Raman scattering detection of 2,4-dichlorophenoxyacetic acid.
abstract: Nearly monodisperse Au nanorods (NRs) with different aspect ratios were separated from home-synthesized polydisperse samples using a gradient centrifugation method. The morphology, size and its distribution, and photo-absorption property were analyzed by transmission electron microscopy, atomic force microscopy and UV-visible spectroscopy. Subsequently, using colloidal Au NRs (36.2 nm ×10.7 nm) with 97.4% yield after centrifugation and Au nanospheres (NSs) (22.9 ± 1.0 nm in diameter) with 97.6% yield as Au substrates, surface-enhanced Raman scattering (SERS) spectra of 2,4-dichlorophenoxyacetic acid (2,4-D) were recorded using laser excitation at 632.8 nm. Results show that surface enhancement factors (EF) for Au NRs and NSs are 6.2 × 10(5) and 5.7 × 10(4) using 1.0 × 10(-6) M 2,4-D, respectively, illustrating that EF value is a factor of ~10 greater for Au NRs substrates than for Au NSs substrates. As a result, large EF are a mainly result of chemical enhancement mechanisms. Thus, it is expected that Au NPs can find a comprehensive SERS application in the trace detection of pesticide residues.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, South China Agricultural University, Guangzhou, Guangdong 510642, People's Republic of China.
authors.forename: Jin-Liang
authors.initials: JL
authors.lastname: Jia
authors.forename: Han-Hong
authors.initials: HH
authors.lastname: Xu
authors.forename: Gui-Rong
authors.initials: GR
authors.lastname: Zhang
authors.forename: Zhun
authors.initials: Z
authors.lastname: Hu
authors.forename: Bo-Qing
authors.initials: BQ
authors.lastname: Xu
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis* / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry*; D006540:Herbicides / Q000032:analysis; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D012542:Scattering, Radiation; D013059:Spectrum Analysis, Raman / Q000295:instrumentation*; D014159:Transducers
chemical_list: D006540:Herbicides; D015084:2,4-Dichlorophenoxyacetic Acid; D006046:Gold