Introduction to Nanoscience and Nanotechnology. Chris Binns

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Introduction to Nanoscience and Nanotechnology - Chris Binns


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difference in biological activity is clear. The location of Mace Head where the aerosol composition was measured is shown in the top image. (b) Composition of aerosol in different size ranges. The region from 0.06 to 0.125 μm (60–125 nm) shows the nanoparticle abundance. In winter they are undetectable but during phytoplankton blooms they are abundant. The data is given for the different particle types: Sea salt (produced by the bubble‐bursting mechanism), NH4, non‐sea‐salt (NSS) SO4, NO3, water‐soluble organic carbon (WSOC) and water‐insoluble organic carbon (WIOC).

      Source: Reproduced with the permission of the Nature Publishing Group from C. O'Dowd et al. [18].

      Not just the products of life but life itself are thrown out of the sea by the bursting bubble route that produces sea‐salt particles. Among the soup of microscopic organisms that live near ocean surfaces are bacteria and viruses. The ones thrown out of the sea join the general atmospheric aerosol of nanoparticles and act as CCNs. In the arctic, they are thought to be a significant contribution to the CCNs responsible for clouds [19].

image

      Source: NCdave. https://commons.wikimedia.org/wiki/File:Sunspot_Numbers.png, Licensed under CC BY‐SA 3.0 (https://creativecommons.org/licenses/by‐sa/3.0/deed.en).

      Nanoparticles themselves do not stop at the top of the Earth's atmosphere and cosmic particles (referred to as “dust” by astronomers) are spread throughout space from a number of sources. Supernovae (Figure 2.1e) have already been mentioned but others include outflowing material from carbon‐rich stars, which is rich in silicon carbide and titanium carbide particles [21] as well as various forms of pure carbon particles including fullerenes (see Chapter 3). As with the particle populations measured in the Earth's atmosphere, when measured as the number density or surface area, it is nanoparticles (<100 nm) that dominate the distribution (Figure 2.2). Thus nanoparticles provide a significant proportion of the solid surface area in space on which chemical reactions can take place.

      Dust particles accelerate the process of condensation of gas clouds by gravity to form stars and planets thus nanoparticles were an important ingredient in the initial formation of our own sun and its planets, including the Earth. It is interesting to note that the special behavior of nanoparticles compared to the bulk matter discussed in Chapter 1 is also important in this context. For example, a significant fraction of particles produced by supernova explosions contain iron (from the core of the exploding star) and are magnetic. The magnetic interaction between the particles in space, which is orders of magnitude stronger than their gravitational attraction, can significantly accelerate the process of condensation and for this to work the particles must be single‐domains, that is, permanently magnetized. As discussed in the previous chapter this requires that they are smaller than a critical size of about 100 nm. Once stars and planets are formed they produce interplanetary particles by various processes. For example, in our own solar system the Jovian satellite Io, which it has a very high volcanic activity sprays vast quantities of particles into the rest of the solar system [22].


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