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Nanoparticle shapes: Quantification by elongation, convexity and circularity measures

Authors
  • Kopanja, Lazar
  • Lončar, Boris
  • Žunić, Dragiša
  • Tadić, Marin
Type
Published Article
Journal
Journal of Electrical Engineering
Publisher
Sciendo
Publication Date
Sep 28, 2019
Volume
70
Issue
7
Pages
44–50
Identifiers
DOI: 10.2478/jee-2019-0040
Source
De Gruyter
Keywords
License
Green

Abstract

The goal of the nanoparticle synthesis is, first of all, the production of nanoparticles that will be more similar in size and shape. This is very important for the possibility of studying and applying nanomaterials because of their characteristics that are very sensitive to size and shape such as, for example, magnetic properties. In this paper, we propose the shape analysis of the nanoparticles using three shape descriptors – elongation, convexity and circularity. Experimental results were obtained by using TEM images of hematite nanoparticles that were, first of all, subjected to segmentation in order to obtain isolated nanoparticles, and then the values of elongation, convexity and circularity were measured. Convexity Cx(S) is regarded as the ratio between shape’s area and area of the its convex hull. The convexity measure defines the degree to which a shape differs from a convex shape while the circularity measure defines the degree to which a shape differs from an ideal circle. The range of convexity and circularity values is (0, 1], while the range of elongation values is [1, ∞). The circle has lowest elongation (ε = 1), while it has biggest convexity and circularity values (Cx = 1; C = 1). The measures ε(S), Cx(S), C(S) proposed and used in the experiment have the few desirable properties and give intuitively expected results. None of the measures is good enough to describe all the shapes, and therefore it is suggested to use a variety of measures so that the shapes can be described better and then classify and control during the synthesis process.

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