Synthesis of CdS nanoparticles in solution and in a polyphosphazene matrix

The synthesis and characterization of a polymer composite system containing quantum-confined II-VI semiconductor particles entrapped in a polyphosphazene network is discussed. A hybrid material was constructed using a guest:host approach in which the ion transporting ability of [NP(OCH2CH2OCH2CH2OCH3)(2)](n) (MEEP) and MEEP-like polymers was exploited to allow the formation of matrix-encapsulated, nanometer-sized CdS particles. As a first step, a cadmium thioglycolate precursor [Cd-10(SCH2CH2OH)(16)](NO3)(4) was found to react in solution to generate stable, soluble, CdS particles. These particles were characterized and found to be 25 Angstrom in diameter. They exhibited an absorption at 362 nm, which was blue-shifted relative to the absorption of bulk CdS. This indicates a quantum confinement effect associated with nanometer-size particles. Second, a method was developed for the incorporation of CdS particles into a cross-linked polyphosphazene-based polymer network, and CdS particles were successfully grown within these polymer films. The CdS-containing polyphosphazene films were transparent and homogeneous. However, no significant control was achieved over the particle size dispersity. The polymer-encapsulated particles were larger than the solution-synthesized ones, with an average diameter of 70 Angstrom diameter. They demonstrated a correspondingly smaller blue shift in the absorption spectrum, with an absorption at 470 nm. The morphology of these particles was examined.