Optimization of the Technique for Obtaining Selenium Nanoparticles Stabilized with Cocamidopropyl Betaine

With the aim of optimizing the technique for the synthesis of selenium nanoparticles stabilized with cocamidopropyl betaine, a multifactorial experiment with three input parameters and three levels of variation was carried out. The selenous acid, cocamidopropyl betaine, and ascorbic acid concentrations were considered as input parameters. The output parameters were the average hydrodynamic radius of the particles (r(av)) and ζ-potential. Photon correlation spectroscopy analysis revealed monomodal size distribution in all the samples. It was shown that the average hydrodynamic radius is most strongly influenced by the concentrations of selenous and ascorbic acids. The minimal size of the selenium nanoparticles (r(av) ≤ 20 nm) is achieved at selenous acid concentration of 0.05 to 0.15 M and at ascorbic acid concentrations of 0.0332 to 0.5 M. Acoustic and electroacoustic spectroscopy examination showed that the technique proposed allows formation of both positively (ζ-potential = +29.71 mV) and negatively (ζ-potential = –2.86 mV) charged nanoparticles. It was found that the ζ-potential of the selenium nanoparticles depends very heavily on the concentrations of the stabilizer and of selenous acid. For obtaining positively charged selenium nanoparticles the selenous acid concentration should not exceed 0.15 M and the cocamidopropyl betaine concentrations should be greater than 0.12 M. Negatively charged selenium nanoparticles are formed at selenous acid concentrations above 0.15 M and at cocamidopropyl betaine concentration under 0.12 M. The micelle structure for the positively charged and negatively charged selenium nanoparticles was proposed.