Synthesis and Characterization of Spectroscopically Encoded Nanocomposites
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Synthesis and Characterization of Spectroscopically Encoded Nanocomposites Baker Jawabrah Al-Hourani1,2, Sheng Dai1, Ramon A. Alvarez-Puebla1, Juan P. Bravo-Vasquez1, and Hicham Fenniri1,2 1 NRC National Institute for Nanotechnology, 11421 Saskatchewan Drive, Edmonton, AB, T6G 2M9, Canada 2 Chemistry Department, University of Alberta, 11227 Saskatchewan Drive, Edmonton, AB, T6G 2G2, Canada ABSTRACT Three sulfur-containing styrene monomers with different leaving groups, 4-vinylphenyl ethanethioate, 1,2-bis(4-vinylphenyl)disulfane, and butyl(4-vinylphenyl)sulfane, were synthesized through nucleophilic substitution/addition reactions and purified through column chromatography. In aqueous solution, these monomers could bind to the surface of gold nanoparticles and form self-assembled monolayers (SAMs). SAMs were analyzed by Raman spectroscopy and showed SERS activity with enhancement factors of more than 105. In addition, SAMs were also formed on the surface of gold/silver nano-island films. The bulk Raman and SERS spectra of monomers on different gold nanostructured materials were very similar. The enhancement factors and the formation of SAMs depended on monomer structure and fabrication method. Also depending on the deposition conditions, laser induced polymerization of the mercaptostyrene monomers SAMs was observed.
INTRODUCTION Because of the enhanced mechanical, optical, optoelectronic and magnetic properties of nanocomposites, nanoparticle–polymer composites have attracted great interest [1]. It has been shown that the introduction of colloidal nanoparticles into a polymer matrix produces materials with unique properties [2,3]. However, agglomeration and uneven distribution of nanoparticles in the polymer matrix is still a problem that needs to be resolved. An effective way to prevent agglomeration involves the covalent immobilization of the inorganic nanoparticles inside the polymer matrix. Sulfur-containing polymers are of great interest for such application because of the high affinity of sulfur for transition metals [2]. Besides the fabrication of nanostructured composites, the polymer/nanoparticle interaction could give rise to the enhancement of the Raman vibrational spectrum, which is known as surface-enhanced Raman scattering (SERS) [4]. In this study, three sulfur containing compounds with different thio-functional groups were synthesized, self-assembled on either gold nanoparticles or nano-island films, and their spectroscopic properties investigated. EXPERIMENTAL PART Instrumentation. Gas chromatography-Mass spectrometry measurements were perfomed on an Agilent GC–MSD-5973N system. FTIR spectra were recorded on an FTS 7000 FTIR spectrometer using KBr pellets. NMR was carried out on a Varian 600 MHz broad-band spectrometer with TMS as internal reference. The Raman and SERS experiments were monitored with a Nicolet Almega XR Dispersive Raman spectrometer equipped with a microscope and CCD camera. The surface plasmon resonance (SPR) spectra were collected in a
HP8453 UV-Vis spectrophotome
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