ISSN 0020-1685, Inorganic Materials, 2007, Vol. 43, No. 11, pp. 1160–1166. © Pleiades Publishing, Inc., 2007. Original Russian Text © K.Yu. Ponomareva, I.D. Kosobudsky, E.V. Tret’yachenko, G.Yu. Yurkov, 2007, published in Neorganicheskie Materialy, 2007, Vol. 43, No. 11, pp. 1295– 1302. 1160 INTRODUCTION The synthesis and characterization of nanoparticles are among the key issues of modern science [1–3]. In recent years, considerable interest has been centered on nanoparticles of semiconductor materials [4, 5], espe- cially on those of metal chalcogenides (CdS, ZnS, PbS). Polymer-matrix nanocomposites containing nanoparticles (quantum dots) are known to possess unique optical properties [4, 6–10]. The optical proper- ties of nanoparticles are very sensitive to structural defects inherent in the nanoscale state and also to defects produced during the preparation and stabiliza- tion of nanoparticles. The processes for the preparation of nanoparticles stabilized in solution or in the presence of polymers do not differ drastically [4]. In the chemi- cal synthesis of metal sulfides in a polymeric medium, H 2 S can be used as a sulfiding agent [8]. Also, use is often made of sodium sulfide [11, 12] or compounds containing active sulfur [13]. Murray et al. [14] used the bis(trimethylsilyl) derivatives (TMS) 2 E (E = S, Se, Te) to synthesize chalcogenides, with Cd(CH 3 ) 2 as the cadmium precursor. Zhou et al. [15] and Samokhvalov et al. [16] described an approach in which CdS nanoparticles (2.5–5.0 nm) are produced in a fatty acid monolayer from a cadmium salt of the same acid and dodecaneth- iol. Transition-metal sulfides are often synthesized in inverse micelles and Langmuir–Blodgett films [6, 16]. Samokhvalov et al. [17] modified CdS nanoparticles on the surface of SiO 2 nanogranules using a radical poly- merization initiator and then polymerized methyl meth- acrylate. As shown by Farme and Patten [18], CdS nanoparticles (2 nm) covered with reactive ligands can be joined by numerous paraxylylene groups to give a polymer containing uniformly distributed nanoparti- cles. In this paper, we describe the synthesis of cadmium sulfide nanoparticles via thermal destruction of thio- urea complexes. This approach was prompted by the fact that transition-metal complexes with thiourea as a sulfiding agent decompose on heating to form the cor- responding metal sulfides. Metal salts begin to react with thiourea (sulfiding agent) in solution, resulting in Cd–S coordination in the complex, which ensures the introduction of sulfur atoms into the nearest neighbor environment of the metal atoms. This, in turn, leads to the formation of structurally perfect sulfides. EXPERIMENTAL Samples for this investigation were prepared using a modified process for the synthesis of metal–polymer composites [19, 20]. The starting chemicals used were thiourea and cadmium acetate [21]. A solution of these reagents was added dropwise to a high-temperature polyethylene–oil solution at 260°ë. The reaction byproducts were removed by flowing argon, which was bubbled through the reaction mixture. The resultant paraffin-like material was transferred to a Soxhlet appa- ratus, and the oil was fully removed by hexane extrac- tion over a period of 8 h. The yellow powder thus obtained was stored in air until characterization. To gain insight into the mechanism underlying the formation of cadmium sulfide nanoparticles, we stud- ied samples of thiourea, metal acetates, a composite of CdS and high-pressure polyethylene (HPPE), and a cadmium acetate thiourea complex (reaction intermedi- ate). Synthesis and Properties of CdS Nanoparticles in a Polyethylene Matrix K. Yu. Ponomareva a , I. D. Kosobudsky a , E. V. Tret’yachenko a , and G. Yu. Yurkov b a Saratov State Technical University, Politekhnicheskaya ul. 77, Saratov, 410054 Russia b Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia e-mail: gy-yurkov@mail.ru Received April 23, 2007; in final form, June 25, 2007 Abstract—Nanocomposites of cadmium sulfide and high-pressure polyethylene have been synthesized. The mechanism of the thermal decomposition of thiourea complexes during the synthesis of cadmium sulfide nano- particles has been investigated. The nanoparticle size, composition, and structure of the nanocomposites have been determined by x-ray diffraction, transmission electron microscopy, IR spectroscopy, and EXAFS spectros- copy, and the thermal decomposition of the nanomaterials has been studied. DOI: 10.1134/S0020168507110027