title: Silanization of Ag-deposited magnetite particles: an efficient route to fabricate magnetic nanoparticle-based Raman barcode materials.
abstract: Silica-coated Ag nanostructures usable as magnetic nanoparticle-based Raman barcode materials were developed. Initially, 283 nm sized spherical magnetite particles composed of 13 nm sized superparamagnetic Fe(3)O(4) nanoparticles were synthesized, and silver deposition was conducted using butylamine as the reductant of AgNO(3) in ethanol. The Ag-deposited Fe(3)O(4) (Fe(3)O(4)@Ag) particles are found to be efficient surface-enhanced Raman scattering (SERS) substrates with the enhancement factor at 632.8 nm excitation to be about 3 x 10(6). After SERS markers such as benzenethiol, 4-mercaptotoluene, 4-aminobenzenethiol, and 4-nitrobenzenethiol were adsorbed onto the silver surface, poly(allylamine hydrochloride) (PAH) was coated onto them using the layer-by-layer deposition method such that a subsequent base-catalyzed silanization could readily form a 60 nm thick silica shell around the PAH layer by a biomimetic process. The cross-linked silica shells effectively prevented the SERS-marker molecules from being liberated from the surface of the Fe(3)O(4)@Ag particles. Although the gram magnetization decreased nearly to one-half of the initial value because of coating with silver and silica, the remaining magnetization was nonetheless strong enough for the silica-coated Fe(3)O(4)@Ag particles to be used as barcode materials operating via SERS.
authors.affiliation: Department of Chemistry, Seoul National University, Seoul 151-742, Korea. kwankim@snu.ac.kr
authors.forename: Kwan
authors.initials: K
authors.lastname: Kim
authors.forename: Jeong-Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Hyang Bong
authors.initials: HB
authors.lastname: Lee
authors.forename: Kuan Soo
authors.initials: KS
authors.lastname: Shin
mesh_terms: D052203:Ferrosoferric Oxide / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012825:Silicon / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman
chemical_list: D012834:Silver; D052203:Ferrosoferric Oxide; D012825:Silicon