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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5604_Библиотеки_им_академика_М_И_Перельмана.pdf
Carbon-Based Nanomaterials: An Overview 15
synthesis of SWCNHs through the direct vaporization of graphite. Utilizing a prototype reactor designed for an estimated production of approximately 100 g/h of soot
at 30 kW, they identified optimal thermodynamic conditions that favoured nanohorn
formation. Analyses of the soot revealed a significant presence of well-structured
carbon nanostructures, predominantly SWCNHs, along with small quantities of
graphene foils and amorphous phase material [73]. Puretzky et al. similarly documented the continuous laser vaporization synthesis of SWCNHs. The use of continuous ablation with individual long laser pulses (around 20 ms) at elevated temperatures yielded the highest SWCNHs production rate, reaching approximately 10 g/
h[74]. The synthesized carbon nanohorns exhibit remarkable features, including a
high surface area, distinct horn-shaped morphology and potential applications in drug
delivery, energy storage and catalysis. These diverse synthesis methods are instrumental in enhancing our understanding of CNHs and expanding their applications in
the field of nanotechnology.
The synthesis methods for NDs have primarily involved the detonation technique [75], hot-filament chemical vapour deposition (HFCVD) [76], high-energy
ball milling of micro-diamond crystals, i.e. high-pressure high-temperature (HPHT)
[77], etc. The detonation method stands out as the predominant approach for largescale synthesis of NDs. This process involves detonating a mixture of carbon sources,
such as trinitrotoluene (TNT) and hexogen, within a metallic chamber in an atmosphere comprising N
and CO2. The obtained soot is collected and subjected to
2
purification processes to isolate NDs. Nevertheless, this method for synthesizing
NDs is costly, involving extreme synthesis conditions and demanding purification
procedures to achieveultra-pure NDs. A recently proposed efficient method involves
liquid-phase pulsed laser ablation, where a pulsed laser ablates a target material in
a liquid medium or dispersed solution. Thomas et al. [78] from graphene dispersions through the liquid-phase laser ablation technique, NDs have been successfully
synthesized. These ND samples exhibit a distinctive photo-absorption at 226 nm
and highlight excitation-dependent emission, resembling the behaviour observed in
carbon dots.
4 Properties of Carbon-Based Nanomaterials
Carbon nanomaterials have garnered significant attention in the realm of materials
research, owing to their distinct characteristics that encompass a noteworthy,elevated
carrier mobility, specific surface area, superior electrical conductivity, optical transparency and flexibility. These attributes have propelled their application across
various domains [79]. Comprising solely of carbon, these materials demonstrate
exceptional stability, excellent conductivity, low toxicity and environmental friendliness. The distinctive features of carbon nanostructures, notably graphene, which
has captivated the interest of scientific communities, are directly tied to its inherent
robustness, surpassing that of any other material approximately 200 times stronger
than steel while retaining malleability. Furthermore, it boasts about 97% transparency
16 S. K. Swain et al.
Fig. 6 Properties of carbon-based nanomaterials
in its pure state, displaying remarkable stability and chemical inertness, alongside a
substantial surface area capable of s tretching by approximately 20% [80]. Various
characteristics of nanomaterials based on carbon are outlined in Fig. 6.
4.1 Physicochemical Properties
Carbon, as an exceptional element in the periodic table, possesses an extraordinary
capacity to set of four valence electrons into various hybridization states, specifically sp
lent bonds and more delicate π–π bonds. The diverse hybridization states empower
carbon atoms to adopt various allotropic forms, with diamond and graphite serving
as primary prototypes, and to construct an extensive array of structures, ranging from
compact molecules to extended chains. Fullerene, carbon nanotubes and graphene
(including its derivatives) primarily consist of carbon atoms with sp
[81]. Nanodiamonds are predominantly composed of carbon atoms exhibiting sp
hybridization [82]. Carbon dots and graphene quantum dots feature a combination
of sp
Nanostructure, such as graphitic carbon nitride (g-CN), is comprised of graphitic
planes formed through the sp
are π-conjugated in nature [84]. The distinct arrangement of carbon atoms in the crystalline lattice of graphite or diamond corresponds to markedly differentphysical entities. Graphite manifests as a series of loosely bonded individual layers, with carbon
atoms forming a honeycomb structure within each layer. The less strength van der
3
,sp2and sp. This versatility results in the formation of both robust cova-
2
hybridization
2
- and sp3-hybridized carbon atoms, along with defects and heteroatoms [83].
2
hybridization of carbon and nitrogen atoms, which
3
Carbon-Based Nanomaterials: An Overview 17
Waals interaction between these layers results in quasi-free π electrons, contributing
to the semimetallic nature of graphite. The valence and conduction bands exhibit an
overlapping point in graphite, resulting in a zero optical gap. Consequently, graphite
appears dark with a high absorption coefficient. On the contrary, diamond adopts a
structure with four strong covalent bonds arranged along the axes of a tetrahedron
3
hybridization) and a face-centred Bravais lattice. This arrangement eliminates
(sp
electron mobility, resulting in a highly insulating material with a substantial optical
gap of up to 5.5 eV. The notably high optical gap positions pure diamond as one
of the most transparent materials. Apart from these two notable forms, carbon can
also take on amorphous structures. Like macroscopic allotropes, the characteristics
of a specific carbon nanostructure depend on the type of hybridization embraced by
carbon atoms. However, quantum confinement in nanometric dimensions or structural arrangements, such as in fullerenes, introduces variations in these properties
[79].
4.2 Thermal Properties
The thermal conductivity of carbon-based nanomaterials stands as a crucial physical property with significant implications in both scientific and engineering realms.
The strategic adjustment of thermal conductivity through structural engineering is a
prevalent practice aimed at meeting diverse application needs. Remarkably high
thermal conductivities have been documented, reaching values as substantial as
1600–4000 W/m·K for single-layered graphene and 2000–3500 W/m·K for SWCNT
[85]. These values far surpass the thermal conductivity of traditional materials like
golds and copper. However, when these nanomaterials are incorporated into bulk
materials with nanostructures such as mats, fibres, bundles, foams and aerogels, the
thermal conductivity experiences substantial impediments due to various factors.
Firstly, during large-scale production, impurities inevitably and structural impurities infiltrate the material, serving as symbolic dissipation sites for phonons. These
deformities, encompassing charged impurities, vacancies, functionalized groups and
Stone–Wales defects, present challenges in detailed interpretation. Recent research
has been particularly active in exploring the impact of defects on thermal transport. Secondly, within the fundamental units constituting these composite materials,
weak force of interactions, mainly hydrogen bonds and van der Waal force, results in
interconnections. This gives rise to elevated thermal contact resistance at interfaces,
resulting in a noteworthy reduction in thermal conductivity by several numeric values.
Additionally, graphite, MWCNTs and multi-layered graphene exhibit a pronounced
anisotropic structure [86]. Covalent bonding prevails in the in-plane direction, facilitating rapid phonon circulation. Conversely, along the out-of-plane direction, interlayer bonding relies solely on t he weak van der Waals force. The coupling energy
between carbon atoms of two layers through van der Waals forces is notably less
strong than that achieved through covalent bonding. Consequently, this gives rise
to pronounced anisotropic electrical and thermal transport properties. In the case
18 S. K. Swain et al.
of graphite, the thermal conductivity is merely 5.7–6.8 W/m.k in case of out-ofplane direction inter-layer bonding, which is lower than that observed in the in-plane
direction by two to three orders of magnitude [87].
4.3 Mechanical Properties
Carbon-based nanomaterials display remarkable mechanical properties, including
elevated elastic modulus and strength, coupled with terahertz frequency vibrations.
These distinctive attributes render them versatile for a myriad of applications in the
field of nanotechnology. Notably, graphene boasts an impressive modulus of elasticity,approximately 1 TPa [88]. Theoretical assessments indicate that single-walled
carbon nanotubes possess intrinsic tensile strengths in the remarkable range of 100–
200 GPa, ranking among the highest in existing materials [89]. Polymer composites incorporating nanodiamonds demonstrate exceptional mechanical strength [90].
Furthermore, studies reveal that fullerenes within fullerite maintain near-spherical
shapes even under high compressive strains, endowing fullerite with elastic properties up to densities of 2.5 g/cm
fullerites exhibit an observed increase in stiffness and strength [91]. The application of carbon-based nanomaterials in diverse technical applications is driven by
their outstanding attributes, specifically high stiffness and strength at an exceptionally small scale. Advancements in the research and development of nanomechanical resonator systems encompass a spectrum of nanotechnologies. This includes
the fabrication and precision control of carbon-based nanomaterials, the design of
nanodevices and the application of modelling and computational analyses [92].
3
. Under applied compression, all considered
4.4 Optoelectronic Properties
The extensively distributed electronic configuration arising from sp2hybridization
in carbon nanomaterials suggests their potential as high-migrated electronic materials. Furthermore, the ability to adjust the band gap of semiconducting carbon
nanomaterials by manipulating their diameter presents unique possibilities for
customizing optical and optoelectronic characteristics. Consequently, carbon nanomaterials, particularly CNTs and graphene, are frequently considered as promising
successors to traditional semiconducting materials like silicon in electronic and optoelectronic applications. The varied electronic properties of CNTs, influenced by
their chiral vectors and quasi-one-dimensional structure, present numerous attractive
possibilities for electronic applications. The unique electronic structure of graphene,
with its honeycomb lattice and carbon atoms bonded through sp
further enhances its suitability for optoelectronic applications. Notably, graphene’s
linear dispersion with a zero band gap suggests the potential for highly tunable optical
excitations, resulting in a featureless optical absorption spectrum across wavelengths
2
-hybridized bonds,
Carbon-Based Nanomaterials: An Overview 19
from 300 to 2500 nm [93]. A monolayer of graphene efficiently absorbs 2.3% of incident light with minimal reflection (<0.1%) over this wavelength range. The transmittance of graphene (1-πα ~ 97.7%) is determined by the effective fine structure
constant (α), dependent on the dielectric constant of the surrounding environment.
Graphene exhibits an absorption peak at 250 nm, attributed to a saddle-point singularity near the M point in the Brillouin zone [94]. While graphene itself lacks luminescence, its chemical derivatives, such as graphene oxide (GO), demonstrate photolumi-
2
nescence, believedto originate from sp
carbon islands within GO or oxygen-induced
defect sites. The objective is to establish a forum where researchers can disseminate
their discoveries concerning the utilization of carbon nanotubes, graphene, carbon
dots and carbon-based nanocomposites in various devices, including but not limited
to transistors, field-effect transistors (FETs), solar cells, photodiodes, sensors, interconnects energy storage devices, light-emitting diodes, photodetectors and flexible
devices.
4.5 Antimicrobial Properties
When examining carbon nanomaterials characterized by a comparable orbital
hybridization of carbon atoms, notable distinctions emerge in their antibacterial
activity and underlying mechanisms based on their dimensionalities. Moreover, it
has become known that the antibacterial efficacy of carbon nanomaterials is intricately tied to their size and surface area. Specifically, augmenting the surface area
of nanoparticles through size reduction enhances their interaction with bacteria,
thereby improving their antibacterial activity. In a broader context, the antimicrobial
effectiveness of nanoparticles hinges on a range of factors, including their composition, surface modifications, intrinsic properties and the specific type of microorganism under consideration. Additionally, the nature and presence of surface functional groups, as well as potential doping, contribute to the nuanced antimicrobial
activity displayed by these nanomaterials [95]. In their pristine state, the majority
of carbon nanomaterials exhibit limited antibacterial efficacy and demonstrate low
selective toxicity against bacteria compared to mammalian cells. To enhance water
solubility and dispersibility, surfactants and polymers are commonly employed
with carbon nanomaterials. This approach increases the likelihood of contact and
strengthens interactions with bacteria, thereby boosting antibacterial activity. Additionally, functionalizing carbon nanomaterials with specific functional groups and
bioactive molecules enhances their bacterial targeting capabilities. The introduction of new properties or functions through decorating with metal/semiconductor
or doping heteroatoms or nanoparticles further improves antibacterial effectiveness.
Mechanical damage to bacterial outer membranes or cell walls is a characteristic
feature of nearly all types of zero-dimensional carbon nanomaterials. The impact
on cell wall or membrane integrity caused by exposure to one-dimensional carbon
nanomaterials, such as CNTs, can be assessed by measuring the leakage of intracellular components like DNA and RNA. Specifically, both SWCNTs and short/long
20 S. K. Swain et al.
MWCNTs exhibit a “needle-like” attack on bacterial cell walls, inhibiting bacterial
growth through membrane depolarization. The destruction of bacterial membranes
resulted due to two-dimensional carbon nanomaterials like graphene oxide nanowalls
(GONWs) and reduced graphene nanowalls (RGNWs), a blade/knife-like action.
Carbon nanomaterials across various dimensionalities exhibit the ability to inflict
mechanical damage on bacterial outer membranes or cell walls. However, the intensity of this mechanical damage varies among carbon nanomaterials with different
dimensionalities. This discrepancy is likely attributed to the distinct types of contact
interactions between carbon nanomaterials and bacterial outer membranes or cell
walls, characterized as point, line and plane interactions at the interfaces of 0D, 1D
and 2D carbon nanomaterials with bacteria, respectively.Moreover, the effectiveness
of mechanical damage can be influenced by several factors, including the diameter,
length and dispersion of the carbon nanomaterial, as well as bacterial culture conditions such as shaking speed. Carbon nanomaterials can generate reactive oxygen
species (ROS) through light-dependent or light-independent reactions, leading to
ROS-dependent oxidative antibacterial effects. Upon photoexcitation, carbon nanomaterials can serve as photosensitizers, inducing photodependent ROS production
to eliminate bacterial cells. Apart from directly causing damage to bacterial cells,
certain carbon nanomaterials with expansive surface areas have the ability to enclose
bacterial cells, isolating them from their nutrient environment and leading to bacterial
inactivation [96]. Studies have reported that the primary mechanisms underlying the
bacteriostatic properties of CNTs include the disruption of cell membrane integrity;
interference with metabolic processes; alterations in cellular morphology and an
increased efflux of plasmid DNA, RNA and cytoplasmic materials [97].
4.6 Biological Properties
The advantages conferred by their small size make carbon-based nanomaterials
appealing for navigating biological barriers, although nanoscale size alone does not
qualify as nanotechnology. Carbon-based nanomaterials possess inherent physicochemical properties with potential applications in various biological contexts.
Graphene, with its expansivesurface area and facile functionalization, holds promise
in numerous areas, particularly in drug delivery. Novoselov et al. emphasized that
graphene derivatives, owing to their large surface area and delocalized π electrons,
can solubilize and bind drug molecules, presenting potential as drug delivery vehicles,
provided high drug loading and suitable in vivo drug distribution and release profiles
can be achieved. CNTs exhibit strong optical absorption in the near-infrared, Raman
scattering, and photo-acoustic properties, expanding their scope for in vivo applications with potential bioimaging and tracing functions alongside drug delivery. CNTs
have been extensively studied as drug carriers, with doxorubicin being a common
model drug. Noncovalent interactions facilitate drug loading onto CNTs. CNTs also
interact with DNA, prompting research into their potential use for gene delivery
Carbon-Based Nanomaterials: An Overview 21
or delivering small interfering RNA (siRNA). Additionally, CNTs have been intensively investigated for various imaging modalities, including fluorescence, photoacoustic and Raman imaging. Fullerenes, particularly C60, have garnered attention
as drug and gene delivery vehicles. Metallofullerenol nanoparticles, fullerene derivatives with a metal atom inside a fullerene cage, are under investigation for their
unique mechanical, thermal and electrochemical properties. Gadolinium (Gd)-based
metallofullerenes, specifically, are being developed as innovative contrast agents
with potential anticancer properties. These derivatives have demonstrated intrinsic
inhibitory activity against breast cancer cells, blocking epithelial-to-mesenchymal
transition and efficiently eliminating breast cancer stem cells, thereby impeding
tumour initiation and metastasis. Another significant area in nanomedicine involves
imaging and diagnostics, where carbon-based nanomaterials, including functionalized fullerenes like C60 with metals, serve as contrast agents and radiotracers [98].
Graphene finds extensive application in biosensors due to its remarkable sensitivity,
which can be attributed to its superb electrochemical properties. The high sensitivity is further enhanced by the strong ionic interaction between the negatively
charged –COOH groups and the positively charged nucleobases, along with the
robust π–π stacking between the nucleobases and the honeycomb carbon framework of graphene. Graphene oxide, on the other hand, exhibits dynamic interaction
capabilities with the probe, contributing to the transduction of specific responses
towards target molecules. This transduction process is facilitated through various
mechanisms such as fluorescence, Raman scattering and electrochemical reactions
[99].
5 Applications of Carbon-Based Nanomaterials
5.1 Environmental Remediation
The preservation of the environment has emerged as a significant social concern.
Despite the implementation of numerous legislations governing effluent discharges,
there remains a pressing need for effective remediation processes to address
complexity in biodegradable possessions and toxicity of pollutants. The wellestablished possessions of CNs, specifically their substantial and precisely defined
surface area coupled with a mesoporous nature, make them ideal for the development of air pollutants surveillance tools. CNTs have been recognized as a prominent
component for remediating a diverse array of organic and inorganic hazardous wastes
when compared to traditional sorbents like clay, zeolite and activated carbon. This
superiority arises from their enhanced chemical and physical associations, accelerating attainment of equilibrium, excellent sorbent ability and customizable surface
chemistry. Extensive research has been conducted on the adsorption approaches of
toxic organic waste molecules on CNTs. Various concurrent mechanisms come into
22 S. K. Swain et al.
play, including hydrophobic interactions occurring on the exterior part of CNTs, π–
π interactions, hydrogen bonding and electrostatic attractions. Raw CNT surfaces
exhibit hydrophobic characteristics and demonstrate a pronounced preference for
adsorbing hydrocarbons over alcohols. Unlike t he bulky nature of activated carbon,
graphene and GO possess a nano-sized structure and intrinsically boasts a large
surface area. Moreover, the functionalities grafted onto the GO surface significantly
contribute to unfolding the sheets, exposing them to foreign contaminants. This
modification also serves as a pivotal step in preventing the aggregation of GO into
flocculates in water, thereby potentially impacting the utilization performance to
eradicate contaminates. Like CNTs, fullerene molecules exhibit a distinctive physical adsorption action towards distinct organic and organometallic compounds, a
phenomenon strongly attributed to the influence of dispersive interaction forces. A
robust interaction takes place between the surface of fullerene and organic components through π–π stacking, facilitated by the encompassment of both the interior
and exterior surfaces of fullerenes by homogeneous π electrons [100].
5.2 Agriculture
The growing global population has led to a surge in food demand, necessitating
the widespread utilization of fertilizers. The escalating costs to farmers are driven
by resource constraints and the inefficient utilization of fertilizers. Nanotechnology holds significant promise for customizing fertilizer production to achieve
specific chemical compositions, enhancing nutrient use efficiency,thereby potentially
reducing environmental repercussions and increasing plant productiveness. Moreover, the regulated release and precise administration of nanoscale active components
can unlock the possibilities of sustainable and methodicalness agriculture [101]. CNs
stand out as particularly intriguing substances to be incorporated into multipurpose
advanced agricultural sensors. In recent studies, researchers havedirected their attention towards understanding the functionality of these CNMs in identifying and evaluating various analytes such as agrochemicals, fertilizers, micronutrients, pesticides,
insecticides and nutrients for the purpose of screening plant maturation and improvement. Utilizing agro-chemical sensing systems facilitates the creation of stable, accurate and rapid monitoring for specific molecules [102]. The researchers carry out
electron transport investigation on mung bean plants once the plants exposed to CD
systematically. The outstanding luminescence characteristic of CD is responsible to
alleviate the photosynthesis process with the aid of electron transportation from CD
to chloroplast of the mung bean plants. In this process, CD acts as electron donor and
increases the transformation speed of light energy into electricity energy and subsequently to chemical energy as assimilatory power adenosine triphosphate (ATP) and
nicotinamide adenine dinucleotide phosphate. Further, the presence of CD provides
suitable environment to improve the evolution of oxygen, noncyclic photophosphorylation and ATPgeneration in deserted chloroplast of mung beans. Additionally, it has
been observed that the charge on the CNs influences its mobility within the plant.
Carbon-Based Nanomaterials: An Overview 23
Fig. 7 Environmental and agricultural applications of carbon-based nanomaterials
MWCNTs influence the photosynthesis pathway of trees and crops by elevating
the transportation rate of electron and boosting the photochemical quantum yield
of photosystem II up to 12% in comparison to controlled experimental environment. Examining fullerene, rGO and MWCNTs, researchers also discovered that
at elevated concentrations of CNs there was a notable increase in numerous phytohormones, which help in improvement of plant’s growth [103]. Potential actions of
carbon-based nanomaterials in different environmental and agricultural sectors are
depicted in Fig. 7.
5.3 Biofuel
The current demand for sustainable solid, liquid or gaseous fuel cells leads to inspire
researchers to develop fuel cells derived from biomass, which are generally known
as biofuels. Utilizing materials characterized by a high specific area and significantly enhanced electrical conductivity will contributeto the development of efficient
24 S. K. Swain et al.
energy conversion devices. CNs play a crucial role in direct electron transfer owing
to their expansive surface areas and heightened levels of conductivity [104, 105].
These materials have been employed to facilitate direct electron transfer between
the redox responsive locations of enzymes and the surface of electrode. The success
of this exploratory path relies on the proximity of the redox-active enzyme to the
CNs. CNTs possess intrinsic conductivity, enabling electrical intercommunication
with enzyme. CNTs facilitate this electrical intercommunication via an electronhopping approach among the immobilized redox sites of enzymes. GQDs exhibit
exceptional conductivity, large exterior area, non-injurious and good biocompatible characteristics. These remarkable possessions provide an ideal assistance for
enzyme loading, facilitating the direct transfer of electrons between enzyme active
sites and the electrode surface [106]. Wen et al. fabricated a diminutive biofuel
cell utilizing SWCNH-modified carbon fibre microelectrodes as the substrate. They
employed glucose dehydrogenase as the biocatalyst on these modified microelectrodes, demonstrating a highly efficient and stable electrocatalyst for the oxidation
of the nicotinamide adenine dinucleotide [107].
5.4 Energy Storage
CNs and nanotechnologies have been validated to serve as competent technologies
in the designing of exemplary and productive energy storage devices. In contrast to
traditional energy materials, CNs showcase unique characteristics related to surface
and size variations, including morphological, electrical,optical and mechanical properties, which prove beneficial in enhancing energy conversion and storage capacity
[108]. Constructed with sp
stability owing to the absence of dangling bonds along their walls. This characteristic enables CNTs to withstand high voltage or current. Furthermore, the predominantly exohedral surfaces of CNTs facilitate easy ion access. Of utmost significance, CNTs boast high electrical conductivity, a feature that contributes to reducing
system resistance and is crucial for scalability. As a result, CNTs are recognized as a
vital candidate for the next-generation electrode in supercapacitors [109]. Moreover,
several peculiarities of SWCNHs make them appealing materials for implementation in energy storage application, including their substantially high surface area;
tailor-able pore layout and excellent ability to transport electron, phonon and heat.
SWCNHs have demonstrated significant feasibility to be implementing in electrochemical energy storage systems, including supercapacitors and storage batteries,
owing to their capacitive behaviour [110].
2
-hybridized carbon, CNTs exhibit exceptional chemical