Abstract
Transition-metal alkane-thiolates (i.e., organic salts with formula Me(SR)x, where R is a linear aliphatic hydrocarbon group, –CnH2n+1) undergo a thermolysis reaction at moderately low temperatures (close to 200 °C), which produces metal atoms or metal sulfide species and an organic by-product, disulfide (RSSR) or thioether (RSR) molecules, respectively. Alkane-thiolates are non-polar chemical compounds that dissolve in most techno-polymers and the resulting solid solutions can be annealed to generate polymer-embedded metal or metal sulfide clusters. Here, the preparation of silver and gold clusters embedded into amorphous polystyrene by thermolysis of a dodecyl-thiolate precursor is described in detail. However, this chemical approach is quite universal and a large variety of polymer-embedded metals or metal sulfides could be similarly prepared.
Highlights
New physical properties appear in a metallic phase when the size is reduced to a nanometric scale [1,2]
The color of nanoscopic coin metals is due to the easy polarization of these small metal domains under visible light; such phenomenon is known as surface plasmon resonance (SPR) and may produce very strong optical extinctions in well-defined spectral ranges
The microstructure of the obtained nanocomposite materials was imaged by transmission electron microscopy (TEM)
Summary
New physical properties appear in a metallic phase when the size is reduced to a nanometric scale (for example, spherical particles with a diameter of only a few nanometers) [1,2]. Depending on the metal type, the nanoscopic particles can be colored (Au, Ag, Cu), fluorescent (Au, Ag), superparamagnetic (Co, Ni, Fe), melting at lower temperatures, etc Such new properties are strictly size-dependent and they can be accurately tuned by changing the Polymers 2011, 3 morphology of the metallic phase (both size and shape) or making alloyed metal nanoparticles. In order to investigate the technological potential of such nanostructured material class (metal/polymer and metal-sulfide/polymer nanocomposites), the availability of a general chemical route adequate to produce different combinations of polymers and atomic or molecular clusters should. Noble-metals, semimetals, and metal sulfides can be produced by thermal decomposition of alkane-thiolates at moderately low temperatures (close to 200 °C) The use of such reactions for the preparation of thioether and disulfide molecules is known in organic chemistry [7]. Dodecyl-thiolates of gold, silver and other metals have been used because they derivate from an odorless thiol (dodecyl-thiol) and produce non-volatile thermolysis by-products, as required to avoid film foaming during the annealing process
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