Introduction - Nanotechnologies for Water Environment Applications - page 3

(e.g., microwaves techniques, combustion synthesis, delamination of layered materials,
controlled crystallization from amorphous precursors). Functionalization (via coating
and chemical modification) is an intermediate process that prepares NMs to be used for
certain applications. In his topic ' Engines of Creation: The Coming Era of
Nanotechnology ', K. Eric Drexler talks about the promises and dangers associated with
engineering at a molecular scale. Functionalization is a step that allows us to use surface
chemistry to engineer NMs so that unfavorable interaction between a biological entity
and a NP can be eliminated. For example, functionalizing carbon nanotubes (CNTs)
will change their surface chemistry and thereby their aggregation and deposition
behavior. It has also been found that functionalized CNTs can be photo-active and can
undergo chemical transformation when released in the environment. Therefore,
functionalization is an important step for developing green nanotechnology in the
pipeline of making NMs for reducing harmful impacts of emerging NPs to human health
and environment. Nanocompositions (via melt compounding or during polymerization,
blending and hot isostatic pressing, plasma spraying techniques, co-evaporation/co-
depostion methods) incorporate NPs into polymeric nanocomposites, resulting in
improved mechanical, electrical and optical properties, better barrier and flame retardant
behavior, etc. Applications of nanotechnology include, but not limited to, (a) security
(e.g., superior/ lightweight materials, advance computing, better sensors and sensor
networks, powerful munitions), (b) healthcare/medical (e.g., faster/cheaper diagnostic
equipment; novel drugs, targeted drug deliveries, biolabeling and detection, cancer
treatments), (c) consumer products (e.g., sunscreens/cosmetics, anti-counterfeit devices,
additives in paints, water- and stain-repellent textiles), (d) engineering (e.g., electronic
products, cutting tool bits, molecular sieves, abrasion-resistant coatings, self-cleaning
glass, lubricants and sealants/hydraulic additives), (e) transportation, (f) agriculture
(controlled delivery of herbicides and pesticides), (g) resources (e.g., energy saving and
utilization of renewable energy, dye-sensitized solar cells, fuel cell catalysts, increased
efficiency of hydrogen generation from water) and environmental areas (e.g.,
water/wastewater treatment, environmental remediation, new biocides). Each of these
aforementioned areas is only a tip of an iceberg of related applications.
Nanotechnology itself is evolving faster (Booker and Boysen, 2005; Willems &
van den Wildenberg, 2005; USEPA, 2007). The NMs of the first generation (between
1985 and 2001) only have passive nanostructures, such as nano-structured coating and
NMs (e.g., nano-metals, polymers, ceramics, catalysts, composites, NPs). The second
generation is between 2001 and 2015 with active nanostructures being
discovered/synthesized, such as amplifiers, transistors, targeted drugs and chemicals,
longer-lasting nano-batteries (fuel cells, solar cells), low-power but high-density
computer memory, adaptive structures, sensors and diagnostic nanoassays, high
performance nanocomposites, ceramics, metals, and membranes. Mass production will
be achieved for many NMs, such as NM-based solar cells, environmental/automotive
catalysts, all kinds of improved electrodes and sensors, cutting tool bits, biological