Biopolymer-protected CdSe nanoparticles.

A synthetic procedure for the encapsulation of cadmium selenide (CdSe) nanoparticles in a sago starch matrix is introduced. The nanocomposite was investigated using structural, spectroscopic, and thermal methods. TEM micrographs of the nanocomposite showed spherical CdSe particles of 4-5 nm in size coated with a biopolymer layer. The absorption edges of both the aqueous solution and the thin film of the CdSe-starch nanocomposite were shifted toward lower wavelengths in comparison to the value of the bulk semiconductor. Infrared measurements revealed that the interaction of CdSe nanoparticles and starch chains takes place via OH groups. Although the onset of the temperature of decomposition of CdSe-starch nanocomposite is lower than that of the pure matrix, thermogravimetric analysis also showed that introduction of CdSe nanoparticles significantly reduced starch degradation rate leading to high residual mass at the end of the degradation process.

Study of Sago starch-CdS nanocomposite films: fabrication, structure, optical and thermal properties.

A synthetic procedure for the preparation of nanocomposite films of sago starch and CdS nanoparticles was introduced. The films were characterized using optical, structural, and thermal techniques. The formation of nanostructured CdS in the starch matrix was confirmed by a blue shift in the onset of absorption in the UV-VIS spectra of the nanocomposites. The average size of the nanoparticles varied from 3.6 to 5 nm, depending on the initial concentration of cadmium acetate during the nanocomposite preparation. Fluorescence measurements of the sago-CdS nanocomposite film showed broad emission in the orange-red part of the spectrum. DSC and TGA analyses revealed significant effects of CdS nanoparticles on the thermal properties of the starch matrix.

Preparation and properties of nano-sized Ag and Ag2S particles in biopolymer matrix.

Silver (Ag) and silver sulfide (Ag(2)S) nanoparticles were synthesized in a sago starch matrix. The resulting nanocomposites were investigated using structural, optical and thermal methods. XRD spectra of the nanocomposites confirmed the presence of nanostructured silver (cubic phase) and silver sulfide (monoclinic phase) in the matrix. TEM micrographs showed that the nanoparticles are mostly spherical in shape. Analyzes of the optical properties of the silver nanocomposite aqueous dispersions/solutions of various concentrations were carried out. The results and the theoretical considerations suggested that at high concentrations there is a release of silver nanoparticles from the composite in the water environment. Further dilution produces homogeneous solution in which silver nanoparticles are capped with starch macromolecules. TGA analysis revealed reduced thermal stability of the nanocomposites with respect to pure starch matrix.