Synthesis and Microstructural Analysis of Benzylthiol-functionalized Au Nanocrystals
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Synthesis and Microstructural Analysis of Benzylthiol-functionalized Au Nanocrystals Floriana Vitale1,2, Luciana Mirenghi1, Emanuela Piscopiello1, Maria Lucia Protopapa1, Leander Tapfer1, Cinzia Giannini3, Antonietta Guagliardi3, Antonio Cervellino4, Giovanni Pellegrini5, Enrico Trave5, Giovanni Mattei5, Paolo Mazzoldi5, Ilaria Fratoddi2, and Maria Vittoria Russo2 1 Dept.of Physics Technology and New Materials (FIM), ENEA, Strada Statale Appia, Brindisi, I-72100, Italy 2 Dept.of Chemistry, University "La Sapienza", P.le Aldo Moro 5, Roma, I-00185, Italy 3 Institute of Crystallography, CNR, via Amendola 122/O, Bari, I-70126, Italy 4 ETH Zurich and PSI Villigen, Lab. for Neutron Scattering, Villigen PSI, CH-5232, Switzerland 5 Dept.of Physics, University of Padova, via Marzolo 8, Padova, I-35131, Italy
ABSTRACT We report on the synthesis and microstructural and microanalytical analysis of dodecanethiol and benzylthiol-stabilized Au nanoparticles (diameter range between 2 nm and 10 nm). Stable functionalized gold nanoparticles were synthesized by using two different routes: a two-phase liquid-liquid method and a one-phase method. The size, strain, shape and crystalline structure of the nanocrystals were determined by a full-pattern X-ray powder diffraction analysis and high-resolution electron microscopy. The chemical environment of the Au nanocrystals and their interaction with the thiols was investigated by X-ray photoelectron spectroscopy. Photoluminescence spectroscopy measurements show a characteristic IR emission at λ=960 nm of small sized Au nanocrystals (~3 nm). The origin of this IR emission line seems to be correlated to the Au-S bonding and the size of the nanoparticles. INTRODUCTION The organothiol-gold nanoparticles are arising great interest for their unique properties and potentialities for application in the diverse areas of optoelectronics, catalysis, chemical sensors, biosensors [1]. The covalently bound capping agent improves the solubility and stability of the gold nanoparticles and allows them to be functionalized with other functional groups. The organothiol surface monolayer stabilizes the gold nanoparticles relative to aggregation and their properties can be influenced by the nature of the capping agent. In fact, the choice to functionalize the gold nanoparticles with an aromatic thiol as benzylthiol arises from the idea to give more structural rigidity and compactness to thiol-gold nanoparticle system [2]. Our organothiol-gold nanoparticles were prepared by two different synthesis methods. The thiolfunctionalized gold nanoparticles were investigated by TEM and XRD (microstructural and morphological properties), XPS (chemical bonding and surface functionalization), and UV-Vis and PL spectroscopy (optical properties).
NANOPARTICLE SYNTHESIS Both dodecanethiol and benzylthiol (R-SH) gold nanoparticles were synthesized by employing two different approaches. The two-phase synthesis was performed following a well stated procedure [3,4]; however, the molar ratio of AuCl4-/R-SH, that in
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