Nanotechnology for domestic water purification - Nanotechnology in Eco-efficient Construction - page 371

carbofuran, monochrotofos, etc.), the chemistry of supported noble metal
nanoparticles can comfortably be utilized for the complete removal of such
pesticides from drinking water. This aspect of complete removal of a wide
variety of pesticides makes the chemistry of supported noble metal nanopar-
ticles unique for drinking water purifi cation.
Noble metal nanoparticles are also found extremely important for ultra-
low concentration sensing of pesticides. Overall, there are two approaches
followed for ultra-low concentration detection of pesticides using gold
nanoparticles:

￿ changes in the signature properties of a functional group attached to
noble metal nanoparticle surface in the presence of organic molecules:
reported to reach a detection limit in ppt level (T. J. Lin et al. , 2006;
Rajan et al. , 2007; Sun et al. , 2008);
￿ changes in the optical properties of noble metal nanoparticles upon
interaction with pesticides (Burns et al. , 2006; Dubas and Pimpan, 2008).

Another interesting application area of noble metal nanoparticles in
drinking water purifi cation is the sequestration of heavy metals (Henglein,
1998). Also the functionalized noble metal nanoparticle surfaces can be
exploited for the detection of heavy metals (Ono and Togashi, 2004; Lee
et al. , 2007; Lu and Liu, 2007).
The anti-microbial effects of silver, in zerovalent and ionic form, have
been widely studied in great detail (Aymonier et al. , 2002; Sondi and Sondi,
2004; Jain and Pradeep, 2005; Sambhy et al. , 2006). Due to the numerous
scientifi c investigations published on this topic and its consequences in dif-
ferent applications, review articles may be consulted for a detailed under-
standing (Silver, 2003; Silver et al. , 2006; Neal 2008; Rai et al. , 2009; Sharma
et al. , 2009). The chemistry behind the biocidal activity of silver nanopar-
ticles, and the way silver ions act against micro-organisms are discussed in
the review by Pradeep and Anshup (2009a). While the precise details are
not yet elucidated, protein inactivation and loss of replication ability of
DNA are suggested. A few important observations are highlighted by
Pradeep and Anshup (2009a).

￿ ￿ ￿ ￿ ￿ ￿

Metal oxide nanoparticles

Wang et al. (2007) investigated the effect of size, fabrication method, and
morphology of ZnO nanoparticles as photocatalysts on the decomposition
of methyl orange. It was found that the preparation method was the most
important step and ZnO nanoparticle, 50 nm in diameter synthesized via
thermal evaporation method, provided the highest photocatalyst activity.
Alumina nanoparticles have been utilized for the removal of heavy
metals from drinking water (Kasprzyk-Hordern, 2004). The suggested