Nanotechnology for Agriculture: Crop Production & Protection by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9789813293748
Publisher: Springer Singapore

10.5.2 Size and Shape

These properties are important factors influencing toxicity of nanoparticles. As particle size decreases, the ratio of surface area to mass increases and changes to the physical–chemical properties of the nanoparticle occur. Generally, a trend of increased toxicity with decreased particle size has been observed with toxic nanoparticles. This is consistent with the increased reactivity of smaller particles and is well illustrated in the case of silver and zinc oxide nanoparticles. For example, evaluations on the interaction of nanosilver upon immobilization on nanostructured silica particles against E. coli, showed size-dependent release of Ag+ ions. Released Ag+ was prominent when fine particles of dimensions less than 10 nm were used. Shape is another important characteristic that affects the properties of engineered nanoparticles. Particles with uneven and rough surfaces, or with irregular shapes, can have corners and edges that are biologically and chemically reactive. Atoms at these locations have a lower bonding coordination (weaker bonds) than bulk atoms, and therefore their reactivity and interactions with microorganisms are affected. Some commonly used shapes of engineered nanoparticles are spheres, rods, squares, hexagons, triangles, and pentagons prepared using various synthesis methodologies. The increased reactivity of edge containing nanoparticles and their correlation to increased toxicity is supported by several studies. For example, truncated triangular silver nanoplates displayed the strongest biocidal activity when compared to that of similar spherical and rod-shaped particles against E. coli (Karimi and Mohseni Fard 2017).

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