Cadmium sulphide nanoparticles embedded in polymeric matrices

Semiconductor nanoparticles represent a very interesting research topic mainly for the optoelectronics applications. The semiconductor particles exhibit properties dependent on the crystallites size, such as the band gap width and the linear optical characteristics (transmission and fluorescence cut-off) besides the non-linear characteristics (refractive index, second and third harmonic generation, two photons absorption, etc). The paper presents the synthesis of CdS nanocrystals and their integration in polymeric matrix. The effect of some polymers with different electrical charges, like polyvinyl alcohol, polyvinyl pyrrolidone, or copolymers maleic anhidride/styrene, maleic anhidride/vynil acetate upon the physico-chemical properties of nanocrystals generated in the aqueous phase was studied. The synthesized nanocrystals were dispersed in polymeric matrix and then were applied on glass support to form films. The properties of the prepared nanoparticles and also the deposited films were investigated by confocal laser scanning microscopy, UV-VIS and fluorescence spectroscopy. In this work we also deal with obtaining of thin films based on colloidal CdS imbedded in potassium silicate-based inorganic polymer. The starting solution was prepared by mixing CdS 10(-4) M aqueous colloidal solution with SSK (potassium silicate solution) aqueous solution (K2O/SiO2=1/5). We prepared several precursor solutions with CdS/SSK=1/1; 2/1; 3/1; 1/2; 1/3 ratios. The films have been obtained by the deposition of the above-mentioned mixture on a silicate glass substrate, by means of a special aluminum device based on "dragging method". After heat treatment, the films have been characterized by fluorescence spectroscopy, which revealed emission peaks at 450 nm, 465 nm, 500 nm, 525 nm and 540 nm, depending on the size of CdS nanocrystals. The microstructure of the films was proved by TEM (transmission electronic microscopy) analysis which presented the relative homogeneous morphology of the films.