Physicochemical characteristics of silver nanoparticles: influence of carbonate alkalinity

Abstract

The potential effects of carbonate alkalinity, which occurs naturally in water systems, in the physicochemical behavior of chemically synthesized silver nanoparticles were investigated herein. UV–Vis spectrophotometer, Zeta-sizer, scanning electron microscope (SEM), and X-ray diffractometer (XRD) had been used to carry out analysis including formation, morphology, stability, optical properties, microstructural properties, and crystal imperfections of colloidal silver nanoparticles. Absorption spectra showed that silver nanoparticles had an absorption peak near 420\xa0nm, which corresponds to the surface plasmon resonance of silver nanoparticles. A gradual decay of absorption intensities, which reflects size variation, as the carbonate alkalinity increased was observed. According to Zeta potential and dynamic light scattering results, sample with 11.9 milliequivalents per liter of carbonate alkalinity was the most stable and of the least size. Conversely, enhanced agglomeration occurred for nanoparticles at higher carbonate alkalinity concentrations due to double layer compression and/or bridging. SEM images results clearly showed that as the carbonate alkalinity increased, crystallization process and agglomerations improved, while crystal imperfections minimized for the present silver nanoparticles Moreover, when the carbonate alkalinity of water was increased from zero up to 35.7\xa0meq/l, the crystallite size increased from 14.23 to 18.87\xa0nm, while the microstrain decreased from 25.44\u2009×\u200910 −4 to 19.18\u2009×\u200910 −4 . XRD patterns revealed that samples have a polycrystalline face-centered cubic (fcc) structure and nanometric dimensions. In conclusion, this work showed that AgNPs might be successfully synthesized under specific conditions of carbonate alkalinity. Potential stability, shape, and agglomeration could be interpreted as well.