Environmental Engineering Reference
In-Depth Information
22
Development of IntellIgent nanomaterIals as
a strategy to solve envIronmental problems
Jose Ruben Morones-Ramírez
Chemical Engineering Department, School of Chemistry, Universidad Autónoma de Nuevo León, Pedro de Alba, S/N. Ciudad Universitaria,
San Nicolás de los Garza, Mexico
In the twenty-first century, our global society will face an important challenge: it will have to generate enough resources for the
increasing world population to subsist, while maintaining homeostasis in our earth's numerous ecosystems. In order to face
such a complex challenge, there will have to be significant breakthroughs and advances in the fields of environmental pollution,
as well as sustainable production of energy, water, and food. Nanotechnology, specifically in the areas of material synthesis and
development, will play an essential role in allowing us to accomplish such difficult tasks. This chapter will address the syn-
thesis, characterization, and environmental applications of “intelligent” materials, which have earned their name due to their
capability of dynamically responding to either external or internal stimuli. This characteristic allows them to be used in synthetic
systems that pretend to improve or at least mimic the properties within a biological system. The materials we will discuss here
are metallic and nonmetallic nanostructures and hybrid polymer-metal nanomaterials. Research in the engineering and design
of all the classified materials mentioned is imperative to stimulate the creation of new technologies and devices that will raise
the standard of living of the world population while being environment-friendly at the same time.
22.1
envIronmentally responsIve materIals as mechanIcal actuators
The fabrication of environmentally responsive mechanical actuators—valves being among the ones most studied—has been
possible with the use of environmentally responsive polymers [1-10]. These materials are capable of undergoing conforma-
tional changes and phase transitions upon local or external stimuli, and are therefore termed “smart” or “intelligent” materials
[11, 12]. As a result of their exhibited mechanical responses, they are excellent candidates for incorporation into microfluidic
systems. These materials have therefore successfully controlled flows [2-5, 13, 14] and delivered chemical entities [2, 15, 16]
in response to different environmental stimuli that turn actuators from “on” to “off.” They have potential applications in gener-
ating chemical gradients, which will translate into achieving a better spatiotemporal control of delivered reagents. In the fol-
lowing sections, we proceed to describe some of the different responsive materials that have been used in the literature to create
such mechanical actuators.
Figure 22.1 shows how responsive polymers are generally categorized as locally triggered or bulk-triggered. However, among
the most commonly studied responsive materials, there are four major types [11]: (1) bulk-triggered temperature-sensitive poly-
mers, such as the widely used poly ( N -isopropyl acrylamide) (PNIPAAm) [17] and elastin-like polypeptides [18, 19]; (2) bulk-
triggered pH-sensitive polymers [2, 20, 21], such as the commonly used acrylic acid [22], which contains carboxylate groups;
(3) other, not so frequently used polymers with bulk-triggered sensitivities to a wide range of physical stimuli such as pressure
 
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