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A. Kumar et al.
structures have experienced attention primarily because of brilliant characteristics
of carbon. The below divisions briefly explains various modification techniques of
popular CNMs: graphene-based nanomaterials (G, GOs, rGOs), graphitic carbon
nitride (g-C3N4), carbon nanotubes (CNTs), nanodiamonds (NDs) and carbon
nanofibers (CNFs).
4.1 Modification of Graphene-Based Nanomaterials
Graphene is the fundamental building block of carbon nanomaterials. Graphene can
be modified to graphite, carbon nanotubes, and fullerenes using different processes
such as wrapping, rolling, and stacking. The principal synthetic routes to grapheme
are chemical cleavage and bulk graphite exfoliation into single-layer graphene
(G). Geim and co-workers discovered single-layer grapheme by exfoliating stacked
graphite with the help of Scotch tape. In the same way, pyrolysis of camphor with the
help of chemical vapor deposition (CVD) on Ni foils have been used to synthesize
Planar Few-Layer Graphene (PFLG) [33]. Graphene has several advantages as an
adsorbent. It tends to agglomerate and form graphite because of stacking and dominant interplanar interaction. So it is required to perform surface functionalization of
GO, graphene, or rGO nanosheets with organic compounds or surfactants to reduce
the aggregation. GO was functionalized using large alkyl chain CTAB through ionic
interactions by [34] to improve the hydrophobicity of GO, which can help in its
removal after adsorption from aqueous solution. The dye taking capacity was seen to
be 2767 mg/g of CTAB-GO for CR dye at pH = 3, and 298 K, which takes a time of
1 h. CR dye has a sulfonated group, negative in charge, that can enhance the adsorption at low pH with the help of electrostatic interactions of the dye with the head group
of the CTnAB-GO composite, positive in charge. Computational and experimental
studies were conducted [35] to determine the adsorption capacity of the drug sodium
diclofenac (s-DCF). These studies were performed on single vacancy graphene, pristine graphene, and graphene in nanoribbon form functionalized with various groups.
The introduction of functional groups enhances the adsorption on functionalized
graphene by s-DCF because of an increase in binding energies. [36] proposed that
heavy metal ions such as As (III), As (IV), and Pb (II) are separated by exceptional
adsorption capabilities of magnetic nanohybrid of GO with MnFe 2 O 4 NPs. This
was because of GO’s unique layered property, which allows large surface area and
excellent adsorption capabilities of magnetic NPs and GO. [37] utilized the nanohybrid material for the separation of cationic dyes from contaminated water. Very high
adsorption capacities and very strong reusability. The effectiveness of adsorption
to GO/rGO can be improved by functionalizing it with metals, biopolymers metal
chalcogenides, or by doping (N, S, etc.). [38] proposed carboxylated GO/chitosan
spheres as an effective adsorbent with a high adsorption capability of 78 mg/g for
Cu2 + fixation in both water and soil. Cu
2+ with high immobilization efficiency to
Cu
2+ bioaccumulation can be reduced to 50% in wheat seedlings by modification by
GO-COOH/CS spheres. These methods deliver an emerging approach in preparing
A. Kumar et al.
structures have experienced attention primarily because of brilliant characteristics
of carbon. The below divisions briefly explains various modification techniques of
popular CNMs: graphene-based nanomaterials (G, GOs, rGOs), graphitic carbon
nitride (g-C3N4), carbon nanotubes (CNTs), nanodiamonds (NDs) and carbon
nanofibers (CNFs).
4.1 Modification of Graphene-Based Nanomaterials
Graphene is the fundamental building block of carbon nanomaterials. Graphene can
be modified to graphite, carbon nanotubes, and fullerenes using different processes
such as wrapping, rolling, and stacking. The principal synthetic routes to grapheme
are chemical cleavage and bulk graphite exfoliation into single-layer graphene
(G). Geim and co-workers discovered single-layer grapheme by exfoliating stacked
graphite with the help of Scotch tape. In the same way, pyrolysis of camphor with the
help of chemical vapor deposition (CVD) on Ni foils have been used to synthesize
Planar Few-Layer Graphene (PFLG) [33]. Graphene has several advantages as an
adsorbent. It tends to agglomerate and form graphite because of stacking and dominant interplanar interaction. So it is required to perform surface functionalization of
GO, graphene, or rGO nanosheets with organic compounds or surfactants to reduce
the aggregation. GO was functionalized using large alkyl chain CTAB through ionic
interactions by [34] to improve the hydrophobicity of GO, which can help in its
removal after adsorption from aqueous solution. The dye taking capacity was seen to
be 2767 mg/g of CTAB-GO for CR dye at pH = 3, and 298 K, which takes a time of
1 h. CR dye has a sulfonated group, negative in charge, that can enhance the adsorption at low pH with the help of electrostatic interactions of the dye with the head group
of the CTnAB-GO composite, positive in charge. Computational and experimental
studies were conducted [35] to determine the adsorption capacity of the drug sodium
diclofenac (s-DCF). These studies were performed on single vacancy graphene, pristine graphene, and graphene in nanoribbon form functionalized with various groups.
The introduction of functional groups enhances the adsorption on functionalized
graphene by s-DCF because of an increase in binding energies. [36] proposed that
heavy metal ions such as As (III), As (IV), and Pb (II) are separated by exceptional
adsorption capabilities of magnetic nanohybrid of GO with MnFe 2 O 4 NPs. This
was because of GO’s unique layered property, which allows large surface area and
excellent adsorption capabilities of magnetic NPs and GO. [37] utilized the nanohybrid material for the separation of cationic dyes from contaminated water. Very high
adsorption capacities and very strong reusability. The effectiveness of adsorption
to GO/rGO can be improved by functionalizing it with metals, biopolymers metal
chalcogenides, or by doping (N, S, etc.). [38] proposed carboxylated GO/chitosan
spheres as an effective adsorbent with a high adsorption capability of 78 mg/g for
Cu2 + fixation in both water and soil. Cu
2+ with high immobilization efficiency to
Cu
2+ bioaccumulation can be reduced to 50% in wheat seedlings by modification by
GO-COOH/CS spheres. These methods deliver an emerging approach in preparing