Characterization of alginate-capped nanosilver by fractal and entropy analysis on its transmission electron microphotographs

Abstract

The study employs conventional techniques and quantitative image analysis tools to characterize alginate-capped nanosilver synthesized by green methods. Sodium Alginate (0.5 %, 1 % and 2 %) was used as a reducing and stabilizing agent. Presence of particles was confirmed by UV-vis Spectroscopy, with absorbance maxima of 412-413 nm for 0.5 %, 1 % and 2 % of polymer. Hydrodynamic sizes of particles recorded for 0.5 %, 1 % and 2 % polymer were 128.4 ± 1.5, 129.9 ± 3.6 and 148.6 ± 1.0 nm by DLS. TEM revealed roughly spherical to cuboidal particles ranging from 15-20 nm and clusters of 100 nm and Energy Dispersive X-ray Spectroscopy confirmed the presence of silver in the particles. Analysis of the TEM images was done in MATLAB R2016b using histogram equalisation for image enhancement and entropy filtering for image segmentation. These techniques revealed the surface pores and polymer distribution around the particle. Statistical analysis (ANOVA) was performed for the measured fractal dimensions of nanoparticles with polymer coating, width of particle together with polymer coating, and thickness of only polymer coating around the particle for various study groups. Significant differences (p < 0.05) were found both between and within the study groups for fractal dimensions of nanoparticles with polymer coating, width of nanoparticles and thickness of polymer coating alone. The analysis was successful in confirming presence and thickness of polymer layer on particles.

Keywords: Alginate; Bionanocomposites; Image analysis; Silver; TEM.