Silver/ions AgNPs

Elemental and ionic silver have long been known to hold antimicrobial properties, and within the last decade it has been discovered that nanoparticulate silver likewise can kill or inactivate a wide range of bacteria, viruses, fungi, and other microscopic organisms. It continues to be a matter of debate whether silver nanoparticles (AgNPs) differ from free silver ions in their mechanism of action or antimicrobial efficacy (Seil and Webster 2012 Sweet and Singleton 2011 Duncan 2011a). 

Figure 33 (a) Schematic representation of pseudorotaxane of dibenzylammonium ions and dibenzo-24-crown-8-ether. (b) Schematic representation of silica-silver core-shell aggregation from dibenzylammonium-functional silica 62 and crown-ether-functional AgNP 63. (c) TEM image of the cote-shell aggregates. Reproduced from Ryan, D. Nagle, L. Rtzmaurice, D. Nano Lett. 2004,4,573-575. ... 

The absorbance in the range of300 nm for all spectra (Figs. 16.1-16.4) can correspond to small AgNPs of 2—4 nm in size or Ag" ions. Taking in account an excess of reducing agent, it can be concluded that this peak deals with the presence in nanosystem only the silver particles less than 4 nm in size. 

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