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16 Carbon-Based Nanocarriers for Drug Delivery
spectroscopy, and X-ray diffraction (XRD). For a thorough characterization, many
approaches must be used as they each give diverse morphological, physical, and
chemical characteristics. The signicance and details of some of these characterization techniques related to CBNs are provided subsequently.
1.3.1 elecTron microscopy
The morphological investigation of CBNsand othernano-morphology may be carried out with the use of electron microscopicimaging techniques, including TEMand
SEM. The dimensionalities and morphological congurations, and orientations of
carbon-based nanomaterials, including graphene and its derivatives, CNTs, quantum
dots and nanodiamonds, can be observed at the initial stages through these microscopical investigations. Higher resolution and the most comprehensive morphological, crystal, and topographic assessment are possible with high-resolution (HR)
TEM. To determine the elementalcomposition of the CBNs, energy dispersive X-ray
analysis (EDX) is frequently used in conjunction with electron microscopy. The orientation/alignment of CNTsand the patterned surfaces resulting from the various
CNT growing processes were visualized usingSEM. SWCNTs and MWCNTs may
be differentiated, and their diameters measured using HRTEM. Moreover, HRTEMEDX is capable of detecting and identifying the existence of carbon-containing and
catalytic nanoparticles [35,159]. The potential of HRTEM to determine the chiral
indices of SWCNTs is more intriguing.
Moreover, it made it possible to recognize fullerenes (C60) within SWCNTs (peapod structures) [160] and even to see the deformation of tiny hydrocarbon molecules
that were contained within carbon nanotubes [161].
1.3.2 FTir specTroscopy
The existence of various functional groups in pristine and functionalized CBNs
can be validated through FTIR spectroscopic analysis. In the case of GO, the existence of oxygenated functional groups such ashydroxyl, carboxyl,and epoxy groups
was conrmed by FTIR. Although FTIR spectroscopy was widely employed for
functionalized CBNs, the intensity signals from FTIR spectroscopy are often weak.
Therefore,other methods, like Raman spectroscopy and XPS, are more suited for
assessing pristinecarbon nanomaterials [35].
1.3.3 UV-Vis specTroscopy
UV-Vis spectroscopy was frequently employed to evaluate the absorption bands of
numerous nanomaterials and nanocomposites, especially the materials that describe
photoactivity. A π-π* transition of aromatic C = C interactions may be seen in
graphene and CNTs, which exhibit a signicant absorption band at about 230 nm
[162]. Incidentally, graphene has a smaller percentage of sp
toGO, which illustrates how it is less transparent in the UV-visible spectrum. Such
distinct characteristic was utilized to analyze reduction reactions or determine the
degree of GO oxidation [163]. Also, as the quantity of layers in graphene climbs, the
2
carbons as compared
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absorbance of the material increases. Using this property, Sun etal. (2010) computed
the number of layers of graphene using UV-visible absorbance at 550 nm [164].
UV-vis spectrophotometry was utilized in the instance of CNTs to evaluate the
dispersion strategies of SWCNTs and MWCNTs since the intensity of the absorbance
rises as the dispersion is enhanced. Furthermore, UV-vis absorbance may be used to
estimate the concentration of CNTs that exist in a solution [35,165].
1.3.4 raman specTroscopy
The most adaptable tool for characterizing carbon-based nanomaterials is recognized
as the Raman spectroscopy investigation. Such a nondestructive characterization
method, which is widely employed for carbonaceous materials, yields critical fragments of information. This characterization techniqueenables one to examine functionalization, structure, and purity, among theother featuresof CBNs. According to
Raman spectroscopy, the D, G, and 2D peaks, which are located about 1350, 1580, and
2700cm-1, correspondingly, are where carbon allotropes may be distinguished. The
D-band (D-disorder) results from the out-of-plane vibrational modes, and it is evidence
of the inclusion of sp3 carbon, whereas the G-band (G-graphite) belongs to the axially
stretched (E2g) phase of graphite. As a result, the sp2-hybridized carbon atoms become
disordered, which results in the structural aberrations observed in the twisted graphene
sheet and/or tube ends. The second-order Raman scattering mechanism is the source
of the 2D band, which has almost twice the frequency of the D band [35,166].
The intensity ofthe G-band of graphene increases with the increase inthe number
of sheets. Moreover, this expansion broadens the 2D band in the plane of higherwavenumber [166]. This phenomenon was used by Ferrari etal. (2006) to design a system for
estimating the layers within graphene specimens [167]. The ratio of peak intensities ID/IG
is another intriguing statistic since it could be employed to assess the degree of disorder
in graphene. When thedefects are identied, two distinct phases have been outlined:
the rst stage depicts the transformation from pure graphite to nanocrystalline graphite
withlowerdefect density, while the second stage accounts for the shift from nanocrystalline graphite to mostly sp2 amorphous carbon ofhigherdefect density [168].
The ID/IG ratio is another tool for evaluating the purity of CNTs, although it is
relatively simple to comprehend. The proportion of defects increases as the ID/IG ratio
rises. In addition to the D and G bands, the radial breathing modes (RBMs)provide
another intriguing band, whichmay be detected at lower wavenumbers ranging from
160 to 350cm-1 [169]. These modes are produced through symmetric contractionand
expansion ofthe tubes along the tube’s axis. RBM could be employed to investigate the electronic framework via its intensity (I
diameter (dt) via its frequency (ω
). It could also be utilized to carry out an (n, m)
RBM
attribution of a solitary isolated SWCNT through the evaluation of both dt and I
Additionally, the identication of the RBM spectrum provides a clear indication of
the existence of SWCNTs. Inthe case ofMWCNTs, the RBM signal is barely perceptible. The reason for this is that the RBM band of wide-diameter tubesis often too
weak, and the ensemble median of the inner tube diameter enhances the signal. The
inverse relationship between RBM’s frequency and tube diameter is one of its most
appealing characteristics [35].
and to evaluate the nanotube
RBM)
RBM.
18 Carbon-Based Nanocarriers for Drug Delivery
1.3.5 X-ray phoToelecTron specTroscopy (Xps)
An effective qualitative investigation of the nanomaterials as well as the surface
chemistry of CBNs can be performed using the nondestructive characterization
method known as XPS. It serves as the most trustworthy characterization method for
determining the elemental composition, chemical state, and electronic state, along
with the functional groups present within the CBNs. The sp2 carbon (C-C), epoxy
(C-O), hydroxyl (C-OH),and carboxyl (COO) peaks in the XPS spectra (C1s)for GO
and GONS are located at binding energies of285, 287, and 290 eV, correspondingly
[100,170]. XPS examination was extensivelyused to evaluate variations in oxygenatedfunctional entitiesinGO and rGO.
1.3.6 X-ray DiFFracTion
The XRDtechniques play a signicant role in the assessment of amorphous and
crystalline materials by offering insights about phase recognition, lattice structure, and qualitative evaluation. This method can estimate interlayer spacing and
is effective for describing and identifying polycrystalline phases. Because of these
factors, XRD has been extensively used to track the oxidation of graphite and
the subsequent exfoliation of graphite oxide to graphene oxide. According to the
XRD pattern, pure graphite has a basal reection (002) peak at 2θ=26o (interlayer
spacing 0.34 nm), while graphite oxide was found at 2θ=12o (interlayer distance
0.7 nm). An interlayer extension in graphite oxide is caused by the complexation
of oxygen species among the graphite layers. As oxidation progressed, the (0 0 2)
diffraction line’s strength progressively faded until it eventually vanished. Simultaneously, oxidation enhanced the strength of the diffraction peak at 12o. The
peak at 12
The literature’s diverse research concluded that the peak emerged in the region
2θ =23.0–23.5°, which reects the rGO of (0 0 2) plane. The XRD pattern in
range 2θ=9–11.20°, on the other hand, reects the (0 0 1) plane of GO. Due to
the addition of hydrophilic groups brought about via oxidation and GO synthesis,
there is an increase in the interlayer spacing in the crystallographic planes of
graphite [100].
talline frameworks that exhibit a peak at 2θ=6o in the XRDspectra [173]. This
method makes it possible to determine the number ofSWCNTs present within every
bundle [159]. A (0 0 2) plane for apeak ofgraphite is visible in MWCNTs at 2θ=26o.
The growth of the MWCNTs has been demonstrated using these signals [35].
o
vanished after complete exfoliation of the graphite oxide [102,171,172].
In comparison to CNTs, as-produced SWCNTs have the propensity to form crys-
1.4 APPLICATIONS OF CBNS
The development of unique nanomaterials with extraordinary functionalities has
resulted in the expansion of nanotechnology in almost all commercial areas in recent
years. CBNs have potential applications as nanomaterials in a variety of elds,
including biomedical, energy, electronics, andenvironmental remediation.The enormous potential of these materials should continue to pique scientic interest, and any
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use of the new technology is anticipated to transform human civilization. Herein, we
briey cover studies on and applications for carbon-based nanomaterials and nanocompositesin therapeutics and environmental remediation.
1.4.1 TherapeUTics
The human race has been provided with a variety of nano-enabled commodities or
nanosystems, which are now used for a variety of biomedical applications. In the
realm of nanostructure purview, such nano-constructs and combinations with pharmaceuticals, enzymes, nucleic acids, viruses, proteins, cellular lipid bilayers, cellular
receptor sites, and antigens (crucial for immunotherapy) are multidimensional [174].
Agroup of nanosystems that have been extensivelyinvestigated for drug delivery
and other biomedical applications is theCBNs. Recently, they have demonstrated
effectiveness in elds including theranostics [175], cancer treatment [10,176], and
regenerative medicine [177]. (See Figure1.5)[178].
Certain characteristics of carbon nanomaterials, including their large surface
areas and outstanding electrical and mechanical characteristics, encourage their utilization in the diagnostic and therapeutic domains as well. The major advantages
over the utilization of CBNs in the eld of therapeutics and diagnostics are:
1. They may absorb a signicant amount of drug due to their supramolecular
“π–πstacking” characteristic.
2. CBNs can be used as novel therapeutic components due to their distinct
optical properties and easy fusion with illuminating components.
FIGURE 1.5 The Biomedical Application of Carbon-Based Nanomaterials. [Replicated with
permission from Mahor et al. (2021)] [178].
20 Carbon-Based Nanocarriers for Drug Delivery
3. CBNs have outstanding near-infrared (NIR) heat conversion competence
that makes them a good choice for photothermal treatment (PTT).
4. Therapeutic agents can be released under regulated conditions using tunable
surface chemistry.
The deployment of CBNs in the biomedical eld is hindered by theircolloidal stability in organic or aqueous environments [20]. Nevertheless, this could be resolved
by stimulating the surface of CBNsusing functionalization via covalent and noncovalent approaches. One such inevitable stage that modulates the surface by incorporating distinct functional entities is the functionalization of CBNs. There are
several methods for covalent functionalization, including oxidation,plasma treatments,dehydrogenation, etc. [178]. Due in signicant part to the surface modication of CBNs, which allows them to, for example, penetrate biological membranes,
theyhave been widely used in the administration of drugs. The therapeutic efcacy
of CBNs-assisted DDSs can be improved through their functionalization with certain targeting ligands such as aptamers and folic acid (FA), which also reduces their
cytotoxicity toward healthy cells.
Modest targeting molecules, such as FA [179], which targets folate receptors
espoused on the exterior of a range of robust cancerous cells, ligands with an afnity
for a particular receptor overexpressed on a particular malignant tumor [10,180], a
monoclonal antibody that recognizes tumor-associated antigens [181], and magnetic
nanoparticles [100], can also be incorporated with the drug-loaded CBNs. Such techniques allow for targeted delivery by receptor-mediated endocytosis or drug aggregation at the target region with the use of an externally applied magnetic eld. As
a result, functionalized CBNs have found use in the transport of proteins, enzymes,
nucleic acids, and biomolecules. CBNshave been used to administer anticancer drugs,
uorescent markers for tumor identication, PTT, and othertheranostics [100,178].
For thefunctions like point-of-care detection, the design of precise biosensors
is essential. Early and accuratediagnosis of conditions like cancer can increase a
patient’s likelihood of surviving [182]. Bioimaging is a technique that allows for the
molecular characterization and investigation of biological processes [183]; it may
examine a treatment plan in addition to aiding in illness detection. Owing to their
superior attributes of having a large surface area, being robust, and having outstanding electronic attributes, graphene-based materials were extensivelyemployed in bioimaging and biosensing applications [182]. The capacity to transport electrons and
the amphiphilicity of these nanomaterialsare two important properties that might
affect their potential for biosensing [184]. The aws in GO facilitate electron transfer,
whereas the functional groups enable surface modication and luminescent component binding [185]. Proteins, oligonucleotides, and antigens are typical examples of
detection molecules [186]. These can be covalently or non-covalently connected to
the horizon of graphene derivatives.
To detect CD59, a lung cancer biomarker, Chauhan etal. (2020) loaded anti-CD59
antigens onto graphite electrodes to form an immunosensor. The graphite rods were
coated with GO to increase their conductivity. The study provided a quick and
noninvasive lung cancer diagnostic method [187]. Arapid and accurate method of
detecting the lung cancer (NSCLC) biomarker CK19 in spiking human plasma was
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developed by Chiu et al. (2018) using a carboxyl-GO-modied biomaterial-based
SPR biosensor. SuchGO-COOH-based SPRchip, which has a positive linear range
(0.001–100 pg/mL) with shorter response times than a conventional SPR chip, outperformed it in terms of detection limits. They later discovered that a biosensor systembased on carboxyl-GO could identify CK19 at levels as low as 0.05 pg/mL in
10% serum proteins and 0.001 pg/mL in PBS solution [188].
CNTs have undergone extensive investigation toward the targeted and controlleddelivery of anticancer agents due to their distinct properties. CNTs are drug
carriers for several anticancer cancer medicines and efcient phototherapy stimulators due to their inherent optical characteristics. Because of their adaptability,
CNTs can be used therapeutically for a variety of cancers. At this time, a lot of
anticancer treatment strategies are aimed at eradicating tumor cells and the conditions that support them. Actively going after cancer cells can effectively remove
their parenchyma, but treating the tumor microenvironment unswervingly can stop
tumor cells from proliferating and spreading by upsetting their environment, which
also indirectly kills cancer cells [189]. Recently, Zhou etal. (2022) synthesized multifunctional and PEGylated MWCNTs for the targeted delivery of the anticancer
agent, Doxorubicin (DOX). Adipic acid (AA) was used as a cross-linking agent to
bind the targeted ligand of folic acid (FA) to hyperbranched poly-L-lysine (HBPLL).
Further, DOX was successfully integrated on the MWCNT-PEG-AA-HBPLL-FA
nanocarrier, and thein-vitro release of drugs was examined using a UV-Vis spectrophotometer. The in-vitro cytotoxicity and anticancer capabilities of DOX-loaded
nanocarrier were investigated in the human embryonic kidney (HEK293) and liver
cancer (HepG2) cells. The presented nanocarrier demonstrated effective drug loading
efciency, pH-responsive and targeteddrug release; this assessment is signicant as
it can get around some of the drawbacks of traditional cancer chemotherapy, like the
simplicity through which obtained nanoparticles attach to cancerous cells receptors,
which then quickly enter receptor-mediated endocytosis and deliver the drug to the
affected regions. At acidic pH levels, intracellular endosome surroundings showed a
signicant proportion of drug release rate. The nanoparticles have been reported to
have signicant cytotoxicity for HepG2 cells and low cytotoxicity for HEK293 cells.
[190]. ANovel SWCNTs-based DDS was designed by Yu etal. (2016) for the prolonged delivery of Paclitaxel (PTX). The sidewalls of SWCNTs were non-covalently
linked with chitosan to improve their biocompatibility. To achieve the cell-targeting
property, biodegradable hyaluronan was also added into the chitosan’s outer surface.
The results showed that PTX release depended on pH and was enhanced at lower pH
values (pH 5.5). The improved SWCNTs drastically lowered intracellular reactive
oxygen species (ROS), which may have boosted the activation of mitogen-activated
protein kinases and greatly facilitated cellular damage. Western blotting results
showed that apoptosis-related proteins were highly expressed in A549 cells. The
vitality of the A549 cells was decreased by PTX-loaded SWCNTs, as evidenced by
cell viability assays and a lactate dehydrogenase (LDH) release experiment [191].
In the family of CBNs, the graphene quantum dots (GQDs) are considered the
smallest derivatives of graphene. Owing to their tiny size, GQDs are able to cross
the blood-brain barrier (BBB) and deliver nucleic acid cargo to cell cytosols and
nuclei. Due to their low toxicity, high solubility, and luminous properties that make
22 Carbon-Based Nanocarriers for Drug Delivery
it straightforward to track drug release, GQDs are a great option for gene carriers.
Recently, Ghafary etal. (2017) established a distinctive nanoconjugate consisting of
GQDs, the chimeric peptide MPG-2H1, and plasmid DNA (pDNA)that is capable of
real-time monitoring and gene delivery [192]. The nanoconjugate was synthesized by
non-covalent interactions between each component. The enhanced complex achieved
transfection efciency that was approximately eight times greater than the typical
peptide-pDNA combination. The results of this study suggest that GQDs could perform well as a transfection vector for gene delivery applications. Due to the signicant presence of the sp2 domain and the possibility for “π-πstacking,” GQDs provide
greater drug loading in comparison to certain other nanomaterial drug carrier systems. Because these biomolecules must be covalently bonded to the edge groups, the
active sites on the edge of GQDs are unfortunately restricted to ligands, making it
doubtful that they will be exploited in gene delivery applications [192]. The promising outcomes of several studies on gene therapy employing CBNs haveboosted the
hopes of individuals seeking treatment. However, the regulatory clearances will take
a long time, even though this is a very different notion because the technology and its
implications for individuals seem mostly unstudied.
Carbon-based nanomaterials, with their superior mechanical and chemical properties, have displayed signicant potential for tissue engineering applications. CNTs
were effectively used in the development of medications for bone, cardiac, and neurological regeneration. Bone is capable of self-healing and rebuilding after mild
trauma or fractures. Nevertheless, in pathogenic injuries, acute bone attrition, or
core tumor excision, bone is no longer able to mend itself if the aws are greater
than a threshold size (5mm) [193,194]. This case reported a variety of treatments,
including xenografts, allografts, and autografts. Unfortunately, these methods have
serious disadvantages, including limited availability and donor site morbidity for
autografts, the risk of resistance and infection transmission for allografts, and the
probability of immunogenicity and a poor clinical prognosis for xenografts [194].
Consequently, a novel and highly promising approach involving the use of 3D constructions known as tissue-engineered synthetic bone scaffolds hasgained tremendous attention, which provides the support required for cell adhesion, growth, and
transformation. Tanaka etal. (2017) developed a 3D block construction consisting
of CNTs and compared its efciency as a scaffold for bone regeneration to that of
PET-reinforced gelatin. The articial structure and rat femoral bone had compressive strengths of 62.1 MPa and 61.86 MPa, respectively, and mechanical analysis
revealed no discernible differences. Cell adhesion occurred earlier on CNT scaffolds compared to collagen-reinforced PET scaffolds. Recombinant human BMP-2
was added, which boosted the ALP activity in the CNTs block and showed good
osteogenesis properties [195].
Corresponding to this, multiple investigations have shown that GO-based nanocarriers may effectively be used for muscle, skin, and cardiac tissue regeneration [10].
Altogether, CBNs showed excellent efcacy and capacity for drug administration
in regenerative medicine, gene therapy, and cancer treatments, which may indicate
a exible treatment option for diseasedindividuals. Despite the positive outcomes
of CBNsbiocompatibility trials, further research is needed to fully understand the
harmful effects and toxicity of carbon-based nanocarriers.
23Fundamentals of Carbon-Based Nanomaterials
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1.4.2 enVironmenTal remeDiaTion
There are signicant environmental degradation concerns as a result of the rise of
modern civilization, the expansion of urbanization, the expansion of industrial output,
and the intensication of transportation. Human productivity and routine everyday
activities are increasingly causing environmental disruption. Antibiotics, pesticides,
dyes, heavy metals, greenhouse gases, endocrine disruptors, and organic compounds
are just a few of the toxic emissions that are released into groundwater, soil, and
air, endangering both human health and the ecosystem [196]. According to the “UN
Global Water Development Report,2018,”around 80% of efuent from urban and
commercial operations is discharged into the environment without anypretreatment,
which either directly or indirectly degrades the quality of the water [197]. Generally,
efuent should be processed before being released into the environment because it
includes hazardous proportions of metallic ions, organic compounds, dyes, and other
cancer-causing substances [198]. Researchers have worked hard to identify a variety
of compounds that may effectively eliminate contaminants fromwastewater, including clay minerals, carbon-based materials, and both organic and inorganic nanomaterials [199].
Due to their outstanding physicochemical characteristics, CBNs have received
a lot of interest in the domain of environmental remediation. These nanomaterials
have higherspecic surface areas, superior acid stability, and heat resistance [197]. It
has been discovered that CBNs, with adsorption effectiveness > 80% andphotocatalytic degradation efciency > 98%, may efcaciously eliminate contaminants like
heavy metals,nitric oxide, dyes, hydrogen sulde,and pharmaceutical compounds
from the surroundings [196]. Throughout the past ten years, studies regarding the
utilization of CBNsin the remediation of pollutants have steadily increased (2012–
2021).Porous frameworks and functional units are themajorattributes ofadsorbent
in nature, which makes it possible to use CBNsin the prevention of environmental
pollution. Particularly at lower concentrations, photodegradation is a useful method
for the removal of organic compounds from contaminants. The optimum outcomes
in the photocatalytic breakdown of organic compounds are the nal products of carbon dioxide and water. In the case ofheavy metal ions, in addition to their deposition
on CBNs, metal ions may also be immobilized in the surroundings by the photocatalytic degradation of high-valent components to low-valent ones, followed by the
production of in-situ precipitates [197].
Signicant benets and potential for application-driven investigation have
been made possible by the distinct physicochemical characteristics of graphene
and related materials, specically through graphene oxide (GO). GO, with its2D
structure, highersurface area, oxygenatedfunctional entities, andfunctionalization
ability, delivered substantial potential for the removal of heavy metal ions, organic
pollutants, radioactive pollutants, and agricultural pollutants like pesticides and herbicides. Nevertheless, the stability and propensity for aggregation of GO in aqueous
environments result in a decline in itsperformance efciency. The effective surface
area of GO nanostructure tends to decrease with aggregation, which has an impact
on the overall effectiveness ofthe water treatment process. These restrictions could
be circumvented by functionalizing GO with inorganic nanomaterials as well as
24 Carbon-Based Nanocarriers for Drug Delivery
other functional groups. Recently, a unique nanocomposite based on GOand other
functionalized nanostructures has been designed for rapid, inexpensive, and effective
methods and used successfully to remove various types of contaminants [138].
To remove lead (Pb (II)) ionsfrom an aqueous system, Zarenezhad etal. (2021)
recently synthesized magnetic graphene oxide (MGO) and further functionalized it
usingMEA,melamine, andEthylenediamine (EDA).For process improvement, the
variables inuencing the adsorption of Pb (II) ions were examined. Acomparison
of the adsorption performances for nanocomposites such as MEA-MGO, M-MGO
and EDA-MGOrevealed 97.65%, 96.34%, and 98% removal efciency for lead ions,
respectively. Moreover, 98% elimination of Pb (II) was seen under ideal circumstances (Co= 20 ppm, X=40 mg, pH =4, t= 10 min) [200]. Utilizing the free
radical reaction approach, Pashaei-Fakhri etal. (2021) were able to effectively produce a nanocomposite hydrogel, particularly acrylamide/GO-bonded sodium alginate (AM-GO-SA) and acrylamide bonded sodium alginate (AM-SA) hydrogel. The
effectiveness of the developed hydrogel composites was assessed for the adsorption
ofcrystal violet dyes. It was discovered that AM-SAand AM-GO-SAeach had the
highest capacity for adsorption at 62.07 mg/g and 100.30 mg/g, correspondingly [201].
In a single step, Chen etal. (2019) demonstratedan entirely novel bio-adsorbent for
simultaneous photochemical reduction and dye adsorption. The bio-adsorbent was
synthesized usingGO, titanium dioxide (TiO2), and corn straw pith (CSP). The GO
and CSP serve as coats and stents, respectively. Nevertheless, TiO2 nanoparticles
are afxed to the adsorbent’s surface and serve as both an adsorbent with enhanced
hydrophilicity and a photochemical dye degradation agent. The direct use of the
adsorbent maize straw pith during pyrolysis offered a valuable and economical utilization for the agricultural commodity. The adsorption process was accomplished
via non-covalent interactions, includingπ–πstackings andelectrostatic interaction.
The conguration and structure of the GO loading with 5 weight percent and 20
weight percent TiO2 were excellent, with signicant removal efciency for pollutants
[202]. The potential use of GOnanoplatelets for the elimination of carbamazepine
was examined by Bhattacharya etal. in 2020. Response surface methodology (RSM)
Articial Neural Network modeling was used to signicantly improve the adsorption
system for the dosage of adsorbent, initial amount of carbamazepine, temperature,
and pH. At adsorbent dosage of 1g/L, pH 2, and 120 minutes of adsorption process,
the highest adsorption capacity was reported to be 9.2 mg/g andremoval efciency
of99%. [203].
In addition, to GO, other CBNs such as carbon quantum dots (CQDs) [204], CNTs
[197], and fullerene [24] have also been extensively utilized for environmental remediation applications. For instance, with their distinct PL attributes and signicant
conversion abilities, CQDs have delivered tremendous potential for the degradation of
dyes and other organic contaminants along with active pharmaceutical agents [205].
Recently, Zhou etal. (2019) used a microwave-assisted technique to produce carbon
dots (CDs), which were then divided into three distinct size fractions using size exclusion chromatography. The lack of a link between CD size and PL emission wavelength
demonstrates that the PL process is notdependent on quantum size. The light absorption characteristics and band gap of the CDs altered with particle size, as evidenced
by UV/vis absorption and diffuse reectance spectrometry. The photodegradation of
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organic dyes was carried out independently using each of the three CDs segments
beneath simulated sunlight exposure. It was discovered that as the dimension of the
particles reduced, the reactivity of the CDs wasincreased. The 2-nm CDs were able
to completely degrade both methylene blue (MB) andrhodamine B (RhB) in 150
minutes. The scavenger experiments revealed that the major components engaged in
the photodegradation of the dyes by the 2-nm CDs aresuperoxide radicals andholes.
Throughout the several cycles of dye degradation, these CDs demonstrated excellent
stability. The 2-nm CDs have alsodemonstrated decent p-nitrophenol photodegradation. For the rst time, thendings of this study describedthat bare carbon dots
might be used to degrade environmental pollutants [206].
Astudy done byQi etal. (2016) describedthat a facile solution-phase approach
could be used to effectively synthesize a variety of fullerene (C60)-modied anatase
TiO2 (a-TiO2) nanostructures of varied C60 proportions. Under UV-A light irradiation,
the photodegradation ofMBby pristine a-TiO2 and C60@a-TiO2 nanostructures was
evaluated, revealing that C60 signicantly improves the photocatalytic performance
of a-TiO2 nanoparticles with an ideal level of 2.0 wt%. They looked into the electronic conguration of the C60@a-TiO2 hetero-interfaces in conjunction with the density functional theory (DFT) computations to unveil the fundamental mechanism of
the C60 stacking on the photocatalytic performance. It was discovered that introducing C60 to the interface of a-TiO2 not only reduced the energy gap but also established
a new doping state across the valance and conduction band. As a consequence, the
C60@a-TiO2 nanocomposites would exhibit better photocatalytic activity due to the
effective charge separation and greater light adsorption caused by the existence of a
transitional electronic state [207].
The photocatalytic breakdown of organic contaminants is still a “black box”
technique, particularly in terms of the study of reactive component activity and the
determination of intermediate compounds, both of which are useful in evaluating
the catalytic characteristics of nanomaterials. The quantitative measurements of
intermediates online remain quite challenging. Future research may focus on developing quick online analysis to comprehend how organic contaminants degrade
through photocatalysis. The majority of nanostructures are still being developed
in laboratories and are thus difcult to produce and utilize on a large scale. CBNs
continue to struggle with high manufacturing costs and challenges with large-scale
production. To safeguard the homeland of mankind, environmental remediation
isreceiving a growing amount of attention worldwide. In the future, mass manufacturing and cost-reduction strategies will likely receive increased emphasis in
the R&D of CBNs. The advancement of methodologies might enable the mass production of inexpensive CBNs. Since CBNsare eventually discharged into the ecosystem, their toxicity in the natural surroundings must additionally be taken into
account [197].
It is unavoidable that a certain amount of CBNs would be discharged into
the atmosphere through their production operations when those are employed
forenvironmental remediation; hence, environmental nanoparticle residues need
to be factored in. Despite the fact that the study on the toxicity of nanostructures
in the ecosystem is still in its early stages, it is important to considerthe toxicity
of CBNs.
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