Nanoparticle AgNPs

Silver nanoparticles [AgNP], on gum Arabic, gelatin or starch. Available as yellow-brownish liquids. They are water soluble in the form of 5-lOnm spheres (10-15nm for starch) and have UV with at 405-4 lOnm. The gum Arabic (GA), gelatin and starch stabilise these particles and can be used for sensor design applications, for in vitro as well as in vivo antimiciobial and antifungal purposes. 

In an exemplary work, Lakowicz and co-workers have used the MEF strategy to increase the detectability of Cy3- and Cy5-labeled DNA on solid substrates covered with silver island films (SIFs) and have found a five- to tenfold increase in intensity from the silver particle-coated quartz substrate compared with uncoated quartz (Fig. 18) [120]. As one would expect from the aforementioned, these enhanced intensities have been accompanied by dramatically shortened fluorescence lifetimes, which in turn has led to a significantly higher photostability of Cy3 and Cy5 in the presence of the silver nanoparticles (AgNPs). In this study, the SIFs have been composed of silver nanoparticles with a diameter of 100-300 nm. 

Thanks to the versatility of the Raman spectroscopy, nanoparticles AgNP(25) were used also to detect other policyclic aromatic pollutants (PAHs), like benzo [cjphenanthrene, triphenylene, and coronene [67]. In this case, selectivity is not as important as in other sensors, because the pollutant molecule can be in principle identified by its Raman spectrum. The affinity constants and the limits of detection of PAHs were also determined. In 2012, Coleman and co-workers developed a method to determine the critical micellar concentration (CMC) of cationic surfactants exploiting the SPB of a series of sulfonato calix [njarene-capped AgNPs [68]. The nanoparticles were synthesized by reducing AgNOs with sodium borohydride in aqueous solution in the presence of the sulfonate calix[n]arene derivatives 24, 26 and 27 (see Fig. 35.15) and characterized by TEM, DLS and UV-visible spectroscopy. Suspensions of the... 

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). 

In this report we describe the preparation of Ag nanoparticles (AgNP) in water by means of a modified (low-organics) Turkevich method, with the aim of verifying the feasibility of this procedure for the development of stable colloidal sols. The latter may be used for the deposition of AgNP over supports. 

---