Synthesis of gold nanocrystals in concurrently polymerizing organic-inorganic hybrid films
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Elvio Carlino and Davide Furlanetto Centro di Microscopia Elettronica - Laboratorio Nazionale INFM-TASC Area Scienze Park, 34012 Trieste, Italy
Cinzia Giannini Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, CNR-IC, sezione di Bari, 70125 Bari, Italy
Patrizia Imperatori Consiglio Nazionale delle Ricerche, Istituto di Struttura della Materia, CNR-ISM, sezione di Montelibretti, 00016 Monterotondo (Roma), Italy (Received 15 July 2004; accepted 14 February 2005)
Gold nanocrystals were formed and grown in simultaneously polymerizing hybrid organic–inorganic films. For the preparation of Au containing films, tetraethyl orthosilicate and methacryloxypropyltrimethoxysilane were separately hydrolyzed and the resulting sols were mixed, followed by the addition of a photoinitiator and a NaAuCl4 solution in methanol. The resulting solutions were spin-coated onto glass-substrates, and the so-formed films were irradiated with a solar simulator at powers ranging from 200 to 800 W. The irradiation resulted in simultaneous polymerization of the films and formation of gold nanoparticles. The irradiated films were characterized by x-ray diffraction measurements, ultraviolet–visible optical absorption spectroscopy and transmission electron microscopy studies. After irradiation at 800 W, the transmission electron microscopy experiments showed the presence of homogeneously distributed Au nanoparticles with a size distribution ranging from 2 to 12 nm. The interpretation of the results indicates that the Au particle growth depends on the matrix polymerization rate; enhancing the rate by increasing the irradiation power or the photoinitiator concentration results in smaller particle domains. This result is explained referring to influence of the polymerization rate on the diffusion of gold species through the host.
I. INTRODUCTION
The current intensive investigation of metal nanoparticles can be ascribed to their peculiar physical properties as well as to their potential applications in different fields ranging from biological labeling to optical materials.1–6 Nanoparticle chemical and structural stability in a host is of particular interest for preventing particle aggregation and chemical degradation and for studying the host– particle interaction in view of device processing. Polymeric hosts features such as low processing temperatures and processability give them a remarkable potential for
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0154 J. Mater. Res., Vol. 20, No. 5, May 2005
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the preparation of nanocomposites. The techniques used up until now for preparing metal nanoparticle–polymer nanocomposites can be broadly classified as follows: (i) mixing of the polymer matrix with a metal precursor and subsequent reduction of the latter;7,8 (ii) separate synthesis of the nanoparticles and subsequent mixing with the polymer;9 (iii) growth of the polymer around the pre-formed nanoparticles, a technique adopted i
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