Environmental Engineering Reference
In-Depth Information
7
NaNomaterials oN the Basis of ChelatiNg
ageNts, metal Complexes, aNd orgaNometalliCs
for eNviroNmeNtal purposes
Boris I. Kharisov
1,2
, Oxana V. Kharissova
2,3
, and Ubaldo Ortiz Méndez
2
1
Facultad de Ciencias Químicas, Universidad Autonoma de Nuevo León, Monterrey, Mexico
2
CIIDIT, Universidad Autónoma de Nuevo León, Monterrey, Mexico
3
Facultad de Ciencias Físico-Matemáticas, Universidad Autónoma de Nuevo León, Monterrey, Mexico
7.1
iNtroduCtioN
Chelating agents and their metal complexes are at the heart of modern coordination chemistry and in their original non-nano
forms were used for environmental protection, for instance, for increasing the solubility of heavy metals in soil and therefore in
enhancing phytoextraction [1]. In the past 20 years, in accordance with general developmental trends in nanoscience and
nanotechnology, a variety of nanomaterials and nanocomposites have been created. These materials have been used, among
other things, for environmental purposes, such as remediation/recovery/selective collection of metals from soils, water, or
seawater [2-6].
In this chapter, we will discuss available nanomaterials and nanocomposites containing metal complexes and a few
organometallic compounds used for the improvement of the environment. In addition to removal of heavy metals, they can
be applied in catalysis. Moreover, they have antibacterial, sorbent, and sensor properties and can be precursors for the
creation of other nanomaterials, utilized for environmental protection. N-, N,O-, S-, and P-containing ligands are the basis
of these nanomaterials/nanocomposites, including well-known materials in nanotechnology such as polyaniline (PANi)
and chitosan.
7.2
elemeNtal metals fuNCtioNalized with ChelatiNg ligaNds
A few functionalized (ligand-capped) or supported metal nanoparticles (NPs) (generally Au, Ag, Fe, and bimetallics formed
from them), containing chelating ligands, have been applied for remediation of toxic metals by their chelation, as sensors for
metal cations.
Multifunctional biocompatible nanochelators present a class of chelating agents that have the potential to compensate for the
drawbacks of traditional ligands used in chelation therapy. The nanoscale dimensions of these nanochelators allow for a high
surface to volume ratio to accommodate multiple ligands on the surface and have good solubility for easy absorption across the
blood-brain barrier. A series of such nanochelators on the basis of gold and iron NPs with chelating ligands that are analogues
of natural phytochelatin (PCh, Fig. 7.1) ligands found in plants were prepared [7, 8]. These natural PCh peptides are cysteine-rich
ligands that are known to take up metals with high affinity and specificity. Ligand-capped Au NPs (~4-nm metal core, ~340-bipy
