Nanoparticles and colloidal self-assembly

Gabriel Caruntu, Daniela Caruntu, Charles J. O'Connor

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

1 Scopus citations

Abstract

Nanotechnology is a burgeoning area of scientific research which comprises the production and manipulation of materials at the nanometer scale. Nanomaterials are commonly defined as solids whose constituent dimensions range between 1 and 100 nm, though the scale is usually extended to several hundreds of nanometers. As an example, the average width of a human hair is on the order of 105 nm whereas a single red blood cell is ∼5,000 nm and a DNA molecule has a diameter of 2-12 nm. Nanotechnology is a synergism of physical, chemical, biological, and engineering concepts having as a common characteristic the nanometer size. Considered of a pure scientific interest a few years ago nanoparticles are nowadays commonplace for the development of new cutting-edge applications in communications, data storage, optics, energy storage and transmission, environment protection, biology, and medicine due to their relevant optical, electrical, and magnetic properties. Their original properties, not encountered in the case of their bulk counterparts, can lead to a potentially tremendous scientific and technological progress. Moreover, all these potential applications are expected to impact profoundly every aspect of modern living. Unlike their bulk counterparts, nanomaterials present a reduced dimensionality associated with a very high surface/volume ratio that increases with decreasing particle size. Consequently, a large fraction of the constituting atoms will be found at the surface of the particles, rendering them highly reactive and inducing specific properties. Because the intrinsic properties of the nanoparticles, such as composition, crystallinity, size, and surface topography are crucial for their physical properties, the control of the structural characteristics through the chemical synthesis is highly desired. As the nanoparticle size/shape plays a crucial role on the unique material properties, studies of the particle size and shape evolution could be useful in providing a mechanistic insight into the manipulation and control of their properties and functionalities. Thus, for the design of novel advanced functional nanomaterials the uniformity of the shape and size of the nanoparticles is also a key issue. Nanoparticles are considered monodisperse when their size distribution is <5%. In the past decade, a particular interest has been paid to the development of new synthetic routes enabling the rigorous control of the morphology and size of the nanoparticles. To be used in advanced technologies, magnetic nanoparticles are particularly required to be highly dispersible in various media since they have the tendency to cluster and precipitate, which drastically reduce their efficiency. The preparation of nanoparticles can be achieved through different approaches, either chemical or physical including gaseous, liquid, and solid media. While physical methods generally tend to approach the synthesis of nanostructures by decreasing the size of the constituents of the bulk material (top-down approach), chemical methods tend to attempt to control the clustering of atoms/molecules at the nanoscale range (bottom-up approach). However, the chemical methods are the most popular, because they present several major advantages over the other conventional methods, i.e., they are highly reliable and cost effective, they allow a much more rigorous control of the shape and size of the nanoparticles and the agglomeration of the resulting particles can be alleviated by functionalization with different capping ligands. Since the literature pertaining to the synthesis of nanoparticles is vast and covers almost all types of materials, including some authoritative reviews on the preparation of metals, semiconductors and magnetic nanomaterials [1-5] an attempt to cover both the synthesis and characterization of the nanostructured materials is pointless. We will therefore give a brief survey on the use of the scanning electron microscopy on the characterization of nanostructured materials as well as providing some relevant examples covering different classes of nanostructured materials. It is noteworthy to mention that because of its lower magnification, the scanning electron microscopy gives information at a large scale about the size and morphology of the nanoparticles. However, for a complete characterization of the structural characteristics of the nanocrystalline materials, the scanning electron microscopy for nanoparticles is usually performed in conjunction with other experimental techniques, including atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction (XRD), as well as adsorptiondesorption (BET) isotherms.

Original languageEnglish
Title of host publicationScanning Microscopy for Nanotechnology
Subtitle of host publicationTechniques and Applications
PublisherSpringer New York
Pages306-356
Number of pages51
ISBN (Print)0387333258, 9780387333250
DOIs
StatePublished - 2007

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