Environmental Engineering Reference
In-Depth Information
34.4 Conclusions and Future Prospects
Mankind has drawn immense beneits from the advancement in science and technology.
However, on the other side of the spectrum, we are faced with the challenge of cleaning
up the after-products of industrial and agricultural activities, an offshoot of this develop-
ment. The large-scale use of different contaminants across the world has polluted many
water bodies. Graphene, with the perfect 2-D structure, spectacular properties that can
be modulated, and a surface that can be modiied, is an attractive candidate for novel
applications in environmental science, especially in the areas of contaminant sensing and
remediation. The last few years have seen an explosion in activities that are dedicated to
utilizing graphene in environmental science, and this chapter has illustrated the potential
of graphene or graphene-based materials for these applications. Wastewater remediation
is one area in which graphenic material has shown immense promise. The large surface
area and the surface structure make them an attractive candidate for various approaches.
Chemically synthesized GO/RGO is believed to be the irst graphenic material to ind
direct application in this area. Diverse approaches including adsorption, photocatalytic
and other catalytic degradation, CDI, and membrane separation-based removal have
been employed for this cause. The high utility of graphene-based materials in all these
strategies points toward the spectacular versatility of graphene. Hence, over the next few
years, water treatment could emerge as one of the chief areas of application for chemi-
cally modiied graphene. The presence of a variety of functional groups, which can be
easily leveraged for functionalizing graphene with speciic molecules, can lead to novel
targeted sensors. The chapter illustrated how graphene in combination with different
materials can be used for FET-based, electrochemical, FRET-based, or SERS-based sens-
ing applications. The mechanism and the part played by graphene to enhance the activity
are also described.
However, challenges still exist in this area. For example, although pristine graphene
(graphene with pure sp
2
hybridized carbon atoms) has tremendous capability for FRET-
based applications, it is highly hydrophobic, which limits the application. Similarly, GO
is highly hydrophilic but its electrical conductivity is comparatively very low. Likewise,
some challenges exist in the bulk production of soluble, well-deined graphene or graphene
derivatives. Cytotoxicity, the cellular uptake mechanism, and the intracellular metabolic
pathway of graphene and its derivates are not known in detail. Several opportunities also
exist in this direction. For example, one important and immediate challenge will be to use
graphene quantum structures, especially in sensing. As discussed in a previous section,
the presence of a band gap in these structures can give an additional tool for creating
sensors. GQDs are known to be luminescent, and this can lead to luminescence-based
sensing applications through appropriate modiications. It has to be reiterated that most
of the sensing applications are done with chemically derived graphene (GO/RGO) since
functionalization of pristine graphene with speciic molecules are not feasible. Most of the
properties (especially electrical properties) of graphene are greatly diminished in GO/
RGO. The conductivity, mobility, etc., are all very low in GO/RGO compared with pristine
graphene. Noncovalent binding of target molecules on pristine graphene is a viable option
but the weak binding is not stable. Thus, research is dedicated to formulate strategies that
can anchor functional groups on graphene without disturbing its sp
2
hybridization. If this
is realized, ultrafast sensors with ultralow detection capabilities can be realized. Research
in this direction is still in its infancy. Another possibility is to utilize graphene bilayers
and trilayers for sensing applications. The area of 2-D materials is ever growing and in
