Introduction to Nanoscience and Nanotechnology. Chris Binns

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Introduction to Nanoscience and Nanotechnology - Chris Binns


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1.14 shows a plot of the strain (relative elongation of a sample) vs. stress (load) for various nanostructured aluminum alloys compared to normal (coarse‐grained) aluminum alloy [14]. The plastic limit or yield strength occurs at the point where the slope changes, and it is seen that nanostructured materials have a value that is up to four times higher than the conventional material. This is a dramatic increase in strength but even higher values have been found in other metals, for example, a 10‐fold increase in copper [15]. A problem with nanostructured materials is also revealed by the plot, however, and that is that they fail (break) at relatively low strains. Problems such as this are being addressed by improvements in processing [15].

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      Source: Reproduced with the permission of Elsevier Science from N. Lopez et al. [16].

      Chapter 8 deals in detail with nanoparticles interacting with living systems, and the introduction described types of nanoparticles that could be used for treating cancer (see Figure I.5). In this section, just one type of application will be considered where size is important and that is nanoparticles, mostly silver, interacting with bacteria and viruses, which has become an increasingly important area for medical research. It has been known for some time that silver is highly toxic to a wide range of bacteria, and silver‐based compounds have been used extensively in bactericidal applications. This property of silver has caused great interest especially as new antibiotic‐resistant strains have become a serious problem in public health. For example, in 2017, such bacteria killed more than 35 000 people in the United States alone [17] and any method of attacking them, not involving normal antibiotics, is becoming increasingly important.

      Before the discovery of antibiotics, silver was used as an antiseptic in the treatment of open wounds and burns. The highly reactive silver ions can bind to the bacterial cell walls inhibiting the cell respiration or they can pass into the cell and denature the bacterial DNA, which inhibits the replications and ultimately leads to cell distortion and death. Silver in the form of chemical compounds applied to wound dressings, although effective, was shown to be less effective than conventional antibiotics [18].


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