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A heterostructured nanocomposite MCM-41
RESUMO
Motivated by evidence that silver nanoparticles have found numerous technological applications we have explored in this work utilization of polythiocyanatohydroquinone as a new efficient reducing and stabilizing agent for the preparation of such nanoparticles. The formation of silver nanoparticles has been confirmed by the UV-Vis spectroscopy, X-ray powder diffraction and by transmission electron microscopy. The potentiometric and spectroscopy kinetic measurements during the nanoparticles growth are also presented. Thermodynamic activation parameters for the silver nanoparticle formation have been determined from the reaction kinetic studies at variable temperatures. On the ground of observations using these techniques, a mechanism for silver nanoparticle growth has been proposed. The narrow size (20-40 nm) and spherical shape distribution of the fabricated nanoparticles together with the high stability of colloids for sedimentation provide a firm basis for applications of the polythiocyanatohydroquinone polymer as a reducing and stabilizing material for the metal nanoparticles preparation and storage.
RESUMO
In this present study, silver nanoparticles were synthesized using synthetic humic substances (HSs) as reducing and stabilizing agents. Preference of synthetic HSs over natural humic matter is determined by a standardization problem resolution of the product due to the strict control of conditions of the synthetic HSs formation. It allows to receive the silver nanoparticles with the standardized biologically-active protective shell that is very important for their use, mainly in medicine. The concentration of sodium hydroxide, synthetic HSs, silver nitrate and temperature employed in the synthesis process are optimized to attain better yield, controlled size and stability by means of UV-visible technique. In the optimal reaction conditions the concentrated silver colloids (55 mM) with 99.99% yield are obtained which were stable for more than 1 year under ambient conditions. The received silver nanoparticles are characterized by UV-visible spectroscopy, X-ray diffraction (XRD), FT-IR spectroscopy and transmission electron microscopy (TEM). The antimicrobial activity of silver nanoparticles against fungal and bacterial strains is also shown.