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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5643_Библиотеки_им_академика_М_И_Перельмана.pdf
244 Herbal Pharmacopeia
step is to prepare a sol, which is then gelled, and the solvent is removed. ‘Sol’ and ‘gel’ are the two
components via which the sol- gel method is named (Khan et al., 2022). It has various names in the
following sorted according to how the solids are contained. Sol is an instance in which solids are
dispersed in a liquid in a colloidal fashion. On the other hand, solid polymers dispersed in a liquid
are called gel. There are essentially two steps in the sol- gel process: as in the case of hydrolysis and
condensation reactions. The hydrolysis process involves the use of water to cause break down in the
precursor’s bonds, which is the rst step towards forming the gel phase. Subsequent to the hydrolysis,
the condensation makes it possible to generate nanomaterials. The excess water is removed in order to
give the formed material its ultimate structure. Normally, the sol- gel technique employs chlorides and
metal oxides in precursors as they are used commonly (Ealia & Saravanakumar, 2017). The precursor
is mixed or shaken in a liquid so that we obtain a system with a liquid and suspended solid phase.
11.4.3.2 Spinning
Spinning is one of the techniques to produce nanoparticles in a reactor that is known as a spinning
disc reactor (SDR) (Khan et al., 2022). This method uses a rotating disc to be tted in a reactor or
chamber. This allows the control of other physical characteristics such as temperature. Normally, in
practice, the reactor is purged with nitrogen or with some other inert gas in order to minimize the
formation of chemical reactions (Dhand et al., 2015). Water and the precursor are placed in the reactor; as the disc rotates at different speeds, spinning occurs., The atoms/molecules then precipitate,
accumulate, and then desiccate and fuse. The nature of nanoparticles synthesized in the spinning
disc reactor depends on the various operating parameters, such as the ow rate of liquid, the position
of feed, the ratio of liquid to precursor, the speed of rotation of the disc, and the nature of the disc
surface, as stated in the work of Ealia and Saravanakumar (2017).
11.4.3.3 Microemulsion Technique
A microemulsion technique comprises of a minimum of three phases: the water constitutes the polar
phase; the oil or hydrocarbon liquid constitutes the non- polar phase; and the surfactant, which acts
as the surface- active agent. It is an optically transparent, macroscopically homogenous, thermally
stable as well as isotropic dispersion. The surfactant acts as a barrier to stop the droplets from
coalescing (Solanki & Murthy, 2011). The microemulsion system comprises spherical droplets of
water- in- oil (W/O) and oil- in- water (O/W) that are evenly spread out and have dimensions between
600 nm and 8000 nm (Dhand et al., 2015). The reverse micellar system with water in oil is a good
reaction site for nanoparticle synthesis. Simply put, micellas are lipid molecules arranged spherically in water- containing solutions. The amphipathic nature of fatty acids leads to the formation
of a micelle. This indicates that the long hydrophobic chain (hydrophobic regions) and the polar
head groups, which are hydrophilic regions, are both present in micelles. The outermost parts of the
micelles are hydrophilic regions, which are polar and drawn to water. Because the micelles are nonpolar, their hydrophobic tails are located away from water. The hydrophilic head of the surfactant,
responsible for forming the aqueous core, is situated within the reverse micelle, while the lipophilic
tail points outward, creating a water- in- oil (W/O) microemulsion. In a W/O microemulsion, metallic
nanoparticles are produced by combining two microemulsions that contain a reducing agent as well
as a metal salt. Typically, sodium borohydride serves as the reducing agent, and the surfactant used
is often Triton X- 100 (Solanki & Murthy, 2011).
11.4.3.4 Hydrothermal Synthesis
The hydrothermal synthesis method utilized high temperature as well as pressure, which causes
a heterogeneous reaction to take place in a water- based environment. Hence, the conditions, such
as the temperature, pH and pressure, purely impacts the properties that are required to synthesize
nanoparticles. This type of surface hydrophilicity makes these nanoparticles appropriate for biotechnological applications. The process can be carried out in two kinds of systems: continuous
hydrothermal or batch hydrothermal (Gan et al., 2020). While the continuous hydrothermal makes it
Nanoparticle Synthesis and Characterization for Herbal Drug Delivery 245
possible to achieve a higher rate of reaction in a shorter amount of time, the batch hydrothermal can
operate a system with the intended ratio phases. When two or more phases of matter, such as gels
and foams, are combined under carefully regulated pressure and temperature, a colloidal system is
created in a chemical solution. This method can produce nanoparticles. One advantage of using this
method is that it produces many NPs in the right shape, composition, size, and surface chemistry at
an affordable price (Abedini et al., 2013).
11.4.3.5 Electrochemical Synthesis
Electrochemical synthesis typically entails constructing chemical compounds inside an electrochemical cell. This technique has merits, including the elimination from consideration of halfreactions that could be wastage- prone and the required potential can be controlled to the desired
value (Sajid & Płotka- Wasylka, 2020). In recent times, there has been thorough research on producing silver nanoparticles through electrochemical synthesis methods. The cutting- edge method
required dissolving a metallic anode in an aprotic solvent for generating the silver nanoparticles.
However, these particles fall into the size range of 2–7 nm, while through the management of current density, the size can be accurately regulated. Counter electrodes provide an excellent possibility
for changing different electrochemical parameters and studying their effects on nal particle size.
The electrochemical generation of silver nanoparticles in an aqueous solution of polyvinyl alcohol
(PVA) was studied. PVA is a cheap man- made polymer which is safe, soluble in water, and biodegradable (Nešovic et al., 2020).
11.4.3.6 Polyol Synthesis
The polyol process is a transformative way to obtain metal- containing compounds when poly(ethylene
glycols) are used like the reaction medium. This serves not only as a solvent but also a reducing
agent wherein it is combined with other dissolved stabilizing agents (Rahman & Green, 2009).
Besides, this method synthesizes numerous types of nanoparticles including; metal oxide nanoparticles such as copper(I) oxide and zinc oxide, magnetic nanoparticles, and metal- based nanoparticles
such as silver, copper platinum (Pt) or palladium (Pd). In one case, polycrystalline copper(I) oxide
nanoparticles could have been formed using a copper nitrate precursor along with a poly(vinyl pyrrolidone) stabilizing agent followed by an ethylene glycol reducing agent. Such an approach presents exciting possibilities for the synthesis of many different kinds of metal- containing compounds
in a fast, efcient, and controlled manner all at once (Dhand et al., 2015).
11.4.3.7 Thermal Decomposition
Thermal decomposition is an endothermic reaction triggered by the application of heat, resulting
in the disruption of chemical bonds within a compound. If this decomposition leads to the release
of heat from the compound's structure, it establishes a positive feedback loop and can cause thermal runaway (Khan et al., 2022). Moreover, the infrared spectra and thermal decompositions of
the metal acetates and dicarboxylates were studied with respect to the metal- acetate compound
bonding. Thermal decomposition with copper, lead, and rare earth acetates was investigated using
thermogravimetry and differential thermal analysis, and desirable results were obtained (Ealia &
Saravanakumar, 2017).
11.4.3.8 Chemical Vapor Deposition & Chemical Vapor Synthesis
To get solid lms from the vapor phase, Chemical Vapor Deposition (CVD) is a method that relies
on chemical reactions at extremely high thermodynamic conditions (Khan et al., 2022). Under certain conditions, thin lms produced using the CVD process also contain ultrane particles. By subjecting the system to elevated temperatures, high supersaturations, longer residence periods, and
compact substrates among other conditions, CVD can facilitate production of nanoparticles (Ealia
& Saravanakumar, 2017). The chemical vapor deposition technique, whose operating conditions
have been altered for nanoparticle generation instead of a thin solid lm, is called chemical vapor
246 Herbal Pharmacopeia
synthesis (CVS). Vapor precursors, which can be solid, liquid, or gas, are generated inside a reactor
under specic conditions, initiating particle formation through a nucleation process and enabling
the production of multi- component or doped nanomaterials (Hachem et al., 2022). In the course
of chemical vapor synthesis, gaseous molecules undergo a chemical reaction to form a condensing
phase that allows the growth of particles. As soon as the temperature increases, so also does the rate
of particle formation. This method effectively produces nanoparticles of carbon, titania, and silica
(Dhand et al., 2015).
11.4.3.9 Plasma- Enhanced Chemical Vapor Deposition
Plasma- enhanced/plasma- assisted chemical vapor deposition (PACVD/PECVD) is a widely
employed technique for depositing thin lms. Plasma unequivocally amplies the chemical reactions required for generating thin lms and nanoparticles, as its name signies (Khan et al., 2022).
The PECVD unit consists of four main components: a power supply (either AC or DC), gaseous
precursors, a vacuum processing system, and a heater. Not only the nanoparticles but also thin lm
production occurs using plasma- enhanced chemical vapor deposition (PECVD) at relatively lower
temperatures compared to typical chemical vapor deposition (CVD). This process involves the participation of ionized species and radicals due to the partially ionized nature of plasma. The process
of synthesizing nanoparticles (NPs) from various materials was successfully demonstrated using
plasma- enhanced chemical vapor deposition (PECVD) (Dhand et al., 2015).
11.4.4 PHysical MetHods
In order to produce nanoparticles, physical methods can use electrical energy, mechanical pressure, thermal energy, or high- energy radiation to induce evaporation, material abrasion, melting,
or condensation. Typically, top- down operation is used by physical approaches. This method offers
the benet of producing nanoparticles that are uniform and monodisperse, without any contamination from solvents. However, given the substantial volume of waste generated during the synthesis
process, the physical processes are considered to be less cost- effective. Physical methods such as
high- energy ball milling, laser ablation, electrospraying, inert gas condensation, laser pyrolysis, and
melt mixing can be employed to produce nanoparticles.
11.4.4.1 High-Energy Ball Milling Process
Due to the exceptionally high temperatures and pressures involved, the high- energy ball milling process is classied as a mechanochemical synthesis process. High- energy ball milling was being introduced by John Benjamin in 1970, and he declared this method as a promising approach to produce
nanoparticles of various sizes and shapes (Xing et al., 2013). In this process, moving balls produce
kinetic energy that directly inuences the material which is being milled, which further causes the
breakage of the chemical bonds hence leading to smaller particles from the milled substances. This
all leads to exposure to new surfaces (Dhand et al., 2015).
11.4.4.2 Physical Vapor Deposition (PVD)
To create NPs and thin material layers, physical vapor deposition (PVD) methods are often used.
These methods typically produce particles ranging in size from a few nanometers to several micrometers. PVD, considered an eco- friendly vacuum deposition method, consists of three basic steps: (1)
vaporizing the material from a solid source, (2) nucleating and growing to obtain thin lms and NPs,
and (3) transporting the vaporized material. Common PVD techniques used for creating NPs include
sputtering, pulsed laser deposition, electron beam evaporation, and vacuum arc (Dhand et al., 2015).
11.4.4.3 Pyrolysis
Pyrolysis involves the thermal breakdown of a precursor material using a ame. The precursor is
subjected to high pressure as it enters the furnace and combusts in a liquid or vapor form through a
Nanoparticle Synthesis and Characterization for Herbal Drug Delivery 247
small opening (Khan et al., 2022). The resulting combustion gases, or byproducts, are categorized as
air to facilitate the recovery of nanoparticles. Some furnaces utilize plasma as well as lasers, instead
of ames, to achieve the high temperatures required for evaporation. Pyrolysis offers advantages
such as ease of use, cost- effectiveness, continuous operation, and high yield.
11.4.4.4 Melt Mixing
In the process of melt mixing, polymer and modied nanollers are homogenized using mechanical
mixing techniques, such as extrusion, kneading and occasionally injection molding (Kamal et al.,
2022). This can be regarded as the most applied mechanical process because it is easily integrated
with existing industrial processes while also being environmentally friendly. It is one of the initial
approaches to the preparation of polymer composites with NPs as llers for the creation of desired
material properties (Dhand et al., 2015).
11.4.4.5 Laser Ablation (LA) and Pulse Laser Deposition (PLD)
One of the most frequently used methods for the generation of nanoparticles is Laser Ablation
Synthesis in Solution (LASiS); this technique uses various solvents to create a vapor of a material
from its solid source using a high- powered laser beam to produce nanoparticles, excluding any other
chemicals or stabilizing agents (Khan et al., 2022). It is depicted that a laser beam (either continuous or pulsed) could be focused on a metal which is being submerged in an aqueous solution, leading to the formation of nanoparticles and plasma plumes (Dhand et al., 2015). This approach can
synthesized to produce a broader range of nanomaterials, for instance metallic nanoparticles, oxide
composites, and carbon nanomaterials (Ealia & Saravanakumar, 2017).
Colloidal nanoparticles in aqueous media could be generated by pulse laser ablation without the
involvement of any surfactants, and these are considered to be uniform particles. All the parameters,
for instance, ablation time, laser wavelength and uence as well as liquid environment are adjustable
to produce the nanoparticles of desired properties. Another vacuum- based technique, Pulsed Laser
Deposition (PLD), can be used to extract a substance from the target with the help of laser energy.
This causes reactions such as ionization, evaporation, and melting, resulting in ablation and the
deposition of material onto a substrate (Radicic et al., 2022).
11.4.4.6 Electron Beam Evaporation (EBE)
Electron beam evaporation (EBE) is another PVD process carried out in vacuum conditions. It
produces thin lms and nanoparticles (Dhand et al., 2015). The EBE system consists of three components, namely electron beam source, a vacuum unit and target materials. The current that passes
through the lament causes it to heat up and thereafter produce an electron beam. Magnets further
direct the focused electron beam to the target material. Regarding the Electron Beam Evaporation
method, the electron beam is responsible in heating the target material, which would later evaporate
when its boiling point is reached at a certain temperature. The evaporated material is then conveyed
and spread over the substrate. EBE has rapid deposition rates; hence, it can be used for a wide
range of materials that have varying electrical conductivities and deposits materials with higher boiling points compared to thermal evaporation. NPs with different sizes and shapes can be deposited
through the EBE process by the selection of proper process parameters and conditions (Bello et al.,
2014).
11.4.4.7 Inert Gas Condensation (IGC)
One of the oldest methods of NP synthesis involves the technique termed inert gas condensation
(IGC), which relies on cooled liquid nitrogen substrate holders and uses inert gases such as helium
or argon for NP production (Kumari et al., 2023). Inert gases are used to carry the evaporated materials, and liquid nitrogen is used to condense them onto the substrate. Hybrid nanoparticles can
be synthesized by atomic vapor phase condensation under high- pressure application by sputtering
multiple targets for instance silver, Iron and silicon (Benelmekki et al., 2015). In the process of DC
248 Herbal Pharmacopeia
sputtering − metal atom vapors are deliberately generated in close proximity to the target surface.
These vapors are then intentionally condensed into nanoclusters as they precisely move through the
aggregation zone. The nanoclusters are subsequently extracted and propelled by the signicant pressure disparity between the aggregation zone (10 mbar) and the deposition unit (10−5 mbar), before
being rmly placed onto the substrate (Dhand et al., 2015).
11.4.4.8 Flame Spray Pyrolysis (FSP)
At the time of writing, the ame spray process (FSP) technology is the most recent of all the ame
aerosol technologies (Teoh et al., 2010). The combustion process is a single- step process in which
the precursor is in a liquid state. The combustion enthalpy is signicantly higher, accounting for
more than 50% of the total energy released during combustion. Typically, an organic solvent is used
in this process. The production of nanoparticles necessitates the subsequent series of steps: (1) The
initial spray undergoes evaporation or decomposition, resulting in the formation of metal vapors. (2)
Nucleation arises because of supersaturation. (3) Growth occurs through the processes of sintering
and coalescence. (4) Particle aggregation is the result of chemical bonding, while agglomeration is
caused by physical interactions. It is a highly utilized method for creating complicated and effective nanoparticles. Liquid precursors can form particles by either the gas- to- particle or dropletto- particle pathway; however, the gas- to- particle route leads to more uniform particle sizes and
morphologies (Dhand et al., 2015).
11.4.4.9 Laser Pyrolysis
Vapor phase synthesis is the method used in CO2 laser pyrolysis (D’Amato et al., 2013). The process
produces condensable products as a result of chemical reactions induced by the laser at the interface
between the laser beam as well as the molecular ow of reactants in the gaseous and vapor phases.
One requirement for achieving energy coupling in the reaction system is that one of the reactants or
precursors must be capable of absorbing infrared (IR) CO2 laser radiation through resonant vibrational modes (Kozuch et al., 2023). In addition, inert photo- sensitizers such as sulphur hexauoride
(SF6), ammonia (NH3), ethylene gas (C2H4), and so on can be added to the reactants to facilitate the
energy transfer between precursors and the laser light. In contrast to alternative vapor phase techniques, laser pyrolysis enables more focused and swift heating, resulting in quick nucleation and
quicker quenching of particle growth (in a matter of milliseconds). In light of this, this process shows
promise for producing NPs with a narrow size distribution in the hot zone and an average diameter of
between 5 and 60 nm. Unfortunately, the nanoparticles attempt to aggregate as soon as they leave the
heated chamber, which leads to the creation of chains of nanoparticles (Dhand et al., 2015).
11.4.4.10 Nanolithography
Nanolithography involves the precise design of nanostructures, typically with at least one dimension ranging from 1 to 100 nm (Khan et al., 2022). It encompasses various processes such as optical, multiphoton, electron- beam, nanoimprint, and scanning probe lithography. Lithography, a key
technique in nanolithography, involves printing specic shapes or structures onto light- sensitive
materials by selectively removing portions of the material to achieve the desired shape as well as
structure. Nanolithography provides unparalleled precision in controlling the size along with shape
of nanoparticles and clusters, ranging from single particles to desired clusters. However, it requires
sophisticated equipment and entails signicant costs (Ealia & Saravanakumar, 2017).
11.4.4.11 Electrospraying Technique
The electrospraying method utilizes an electromechanical device to generate charged droplets. This
is achieved by taking a solution that contains the desired polymer as well as solvent into a syringe,
and applying a high voltage to the tip of the capillary (Anu Bhushani & Anandharamakrishnan,
2014). The solvent undergoes evaporation during its journey toward the counter electrode, resulting in the collection of particles or bers as the nal product. With the use of various solvents, it
Nanoparticle Synthesis and Characterization for Herbal Drug Delivery 249
is possible to create different types and sizes of nanoparticles (NPs) through the electrospraying
technique. These kinds of nanoparticles can be applied to treat many different serious diseases. The
capacity to produce uniform nanoparticle sizes, a quick preparation process, and bulk NP assembly
are just a few of the benets of using the electrospraying technique. However, due to thermal or shear
stresses in the syringe and drying process, this method may also result in the degradation of some
macromolecules (Dawadi et al., 2021). It is also possible to create engineered water nano- structures
(EWNS) from atmospheric water vapor by using the electrospraying technique. With a low toxicity
level and an impressive array of chemical, physical, biological, as well as morphological properties,
the 25 nm- sized EWNS has a remarkable mechanism of action (Pyrgiotakis et al., 2014).
11.4.5 biosyntHesis of nanoParticles
An environmentally friendly, low- toxic, economical, effective, as well as biodegradable method
for creating nanoparticles is biosynthesis, also known as green synthesis or bio- assisted synthesis
(Dhand et al., 2015). The formation of metal oxide nanoparticles and metal nanoparticles can be
achieved by using biological systems such as actinomycetes, plant extracts, fungi, bacteria viruses,
yeast and yeast- like species The formation of nanoparticles by chemical means carries certain risks−
for example, carcinogenic, genotoxic and cytotoxic risks. However, pressure, high energy and temperature are employed in the process of physical synthesis. The biosynthesis of nanoparticles offers
signicant advantages over physical and chemical methods due to its non- toxic nature, simplicity,
cost- effectiveness, ability to detoxify heavy metals, and environmental friendliness. It eliminates
the need for pressure, high temperature, and energy, along with toxic chemicals (Karunakaran et
al., 2023). Three steps are typically involved in biosynthesis: choosing a stabilizing agent, choosing
a reducing agent, and choosing a reaction medium. Biosynthesis could be categorized into three
main groups on the basis of the origin of raw materials, namely: biomolecules, microorganisms, and
extracts derived from plants.
11.4.5.1 Utilizing Biomolecules as Templates for Synthesis
To create nanoparticles, different biomolecules, including viruses, membranes, diatoms, and nucleic
acids, were used as templates. It is well known that transition metal ions have a strong afnity
for DNA, a biomolecular template. Nanoparticles of gold were prepared by cross- linking of DNA
hydrogel and by incorporating transition metal ions into the DNA macromolecules such as Au (III)
ions. The decrease of Au (III) also leads to the formation of single gold (Au) atoms and metal clusters to form gold nanoparticles adjacent to the DNA chain (Morikawa et al., 2021).
11.4.5.2 Microbial Synthesis
Most of the nanoparticles are produced within bioreactors that include algae, actinomycetes, yeasts,
fungi and the prokaryotic bacteria. Extensive scientic efforts have been channelled to the advancement of this method for the synthesis of gold, cadmium sulde, palladium, silver, titanium dioxide,
and others. Microbes uptake target ions from the surroundings and transform them into element metals through the enzymes released by their cellular actions (Zhang et al., 2011). On the basis of the
formation site, nanoparticle synthesis can be categorized into extracellular synthesis and intracellular synthesis. Another method of nanoparticle formation is intracellular biosynthesis in which metal
ions are taken into microorganism cells and then used with the aid of enzymes to form nanoparticles.
Otherwise, it can happen extracellularly when enzymes bind metal ions to the surfaces of microbial
cells. Metal ions are present in the bacteria cell by using the enzymes and anionic functional groups
that minimize interactions (Dhand et al., 2015).
11.4.5.3 Utilizing Botanical Extracts for Synthesis
Using plant extracts to produce nanoparticles through a green synthesis process is a highly efcient,
non- toxic, rapid, and environmentally friendly method. It has proven possible to create metal oxide
250 Herbal Pharmacopeia
FIGURE 11.2 Methods for preparation of nanoparticles.
and noble metal nanoparticles through green synthesis. Due to their roles as capping and reducing
agents, various plant biometabolites may contribute to the synthesis of nanoparticles. Terpenoids,
amino acids, hydrogenase, tartaric acid, quercetin, sequiterpenes, tannic acid, saponin, peptide, citric acid, secondary metabolites, avonoids, protein, phenolics, heterocyclic compounds, as well as
functional groups (alcohols, sulfhydryl, ketones, amines as well as carboxyl acids) are among the
reducing agents. The capping agents include pralines, peptides, extracellular proteins, tannic acid,
enzymes, tartaric acid, functional groups (such as ketones, carboxylic acid, aldehydes, alcohols, and
amines), and citric acid (Adeyemi et al., 2022).
11.4.6 MecHanical tecHniques
Nanoparticles can also be produced through mechanical means such as milling, mechanical alloying, as well as mechanochemical processes (Tulinski & Jurczyk, 2017). At low temperatures, the
milling method restores chemical interactions between surfaces. The mechanochemical technique
is a continuous welding process that minimizes agglomerations and appropriately selects milling
materials. To achieve efcient production, it is of utmost importance to thoroughly analyze the thermal treatment, stoichiometry of source materials, reaction pathways, as well as milling conditions
(Figure 11.2).
11.5 CHARACTERIZATION OF NANOPARTICLES
Characterization of materials entails studying materials with an aim of identifying their properties,
structures, and compositions by looking at chemical as well as the physical properties. The most
common classication of nanoparticles encompasses dimension, structure, as well as electric charge
that is determined by analysis with the aid of instruments such as Transmission electron microscopy
Nanoparticle Synthesis and Characterization for Herbal Drug Delivery 251
(TEM), Atomic force microscopy (AFM) as well as Scanning electron microscopy (SEM). Chemical
properties of nanoparticles include size, shape, color, refractive index, uorescence and others, while
physical properties include size, density, surface area, and others (Khan et al., 2022).
11.5.1 cHeMical
It is crucial to note that the applications of nanoparticles are closely coupled to their chemical nature
with regard to reactivity to target, and sensitivity to factors such as light, heat, moisture, atmosphere
and stability. Among the useful properties inherent to the nanoparticles are fungicidal, decontaminating, bactericidal, and anti- toxic effects, which is why the nanoparticles can be effectively used in
biomedical and ecological applications (Ealia & Saravanakumar, 2017). The following techniques
can be used to determine the stability of nanoparticles − for example, Ultraviolet- visible spectroscopy (UV- Vis), Transmission Electron Microscopy (TEM), dynamic light scattering, and zeta
potential (Sandhiya & Ubaidulla, 2020).
11.5.2 PHysical
Optical properties − for instance, coloration, ability to transmit, ability to absorb and ability to reect
light − are aspects of the physical characteristics of nanoparticles. These nanoparticles are also
effective in absorbing and reecting ultra violet (UV) light when they are incorporated in a solution
or used in forming a coating layer. Moreover, their mechanical properties, including malleability,
strength and exibility, elasticity or tensile strength affect their usefulness (Ealia & Saravanakumar,
2017). In addition, the magnetic and electrical characteristics, including resistivity, conductivity, and
semi- conductivity, have made it possible to utilize nanoparticles in current electronics and renewable power sources.
11.5.2.1 Particle Size Analyzer
The analysis of synthesized nanoparticles is heavily dependent on their morphology and particle
size distribution (Al- Gebory & Mengüç, 2018). Nanoparticles are primarily utilized for drug delivery and targeted drug administration. The size of the particles signicantly affects drug release;
smaller particles with larger surface areas lead to faster drug release as a greater proportion of the
loaded drugs are exposed to the surface. Conversely, drugs diffuse more slowly within larger particles. However, one of the disadvantages of smaller particles is their tendency to become aggregated
during nanoparticle dispersion storage and transportation. Therefore, there is a trade- off between
smaller particle size and the stability of nanoparticle dispersion (Chakraborty et al., 2016).
11.5.2.2 Surface Area Analysis
The surface area of the particles is calculated by adding up the areas of the surfaces that are exposed
on the particles, and then dividing that by the mass of the particles. The relationship between surface
area and particle size is an inverse one. The surface area of a powder can be determined by utilizing nitrogen adsorption. The Brunauer, Emmett, and Teller (BET) method is frequently employed
for the quantication of the overall surface area. Assuming that the particles are perfectly spherical
as well as having a narrow size distribution, the specic surface area can be used to calculate the
average particle diameter in nanometers using the formula below: dBET =6000/ñs. S represents the
specic surface area measured in square meters per gram, while ñ represents the theoretical density
measured in grams per cubic centimeter (Chakraborty et al., 2016).
11.5.2.3 Zeta Potential
As for the measure of the electrical charge in the surface of the nanoparticle, zeta potential is used.
The term zeta potential dened the ability of the measuring of the effective charge on the surface of
a nanoparticle that plays the most vital role in controlling the motion of the nanoparticle. This charge
252 Herbal Pharmacopeia
is protected by the bringing of ions of opposite charges close to the surface of the nanoparticle. The
above- described layers of ions run separately and jointly with the nanoparticle. There are claims that
the value of zeta potential has a straight link to the stability of the particles. The greater the value of
the potential, for example, the magnitude of the wave function is small and the electrostatic repulsion is larger leading to increase stability (Khatak & Dureja, 2015; Sandhiya & Ubaidulla, 2020).
11.5.2.4 Thermogravimetric Analysis (TGA)
Thermogravimetric analysis (TGA) is an analytical technique employed to investigate the weight
changes of a sample as a function of temperature and time at a well- dened thermal history (Kharisov
et al., 2014). This tool can be used for the characterization of inorganic as well as organic solid substances. Non- isothermal transitions of a substance can be understood with the help of differential
thermal analysis, which is a method of calorimetry that measures temperature and heat ux. This
technique also enables the selection of the right transition points, such as melting point and glass
transition, as well as crystallization point (Sandhiya & Ubaidulla, 2020).
11.5.2.5 Dynamic Light Scattering
Dynamic light scattering or photon correlation spectroscopy (also called PCS) is the most widely
applied technique in particle size analysis. Namely, if the precise set of conditions is applied, such
as an angle and optimal temperature in the case of the current experiment, dynamic light scattering
can serve as the means for the determination of the particle size and the polydispersity index of the
given material. The technique is useful in determining the surface charge and the physical state of
the emulsion (Sandhiya & Ubaidulla, 2020). DLS is highlighted as the most efcient technique for
quantifying the Particle Size Distribution, particularly for the Brownian particles within the nano
and submicron range in colloidal media (Chakraborty et al., 2016).
11.5.2.6 Scanning Electron Microscopy (SEM)
The magnication power of the scanning electron microscope (SEM) means its images have a high
depth of focus, which provide a realistic three- dimensional view of surface topography: SEMs are
therefore better suited to looking at the surface details of samples (Kumar & Seth, 2021). Electrons
emitted from a source are concerned in an electric eld gradient in a vacuum environment. It allowed
for the direct visualization and evaluation of the samples’ morphological features and was employed
in this work for morphological and sizing assessment. It has, however, proved of some use in the
determination of size distribution, but falls short in offering all the rounded details. When using
SEM to characterize samples, nanoparticles have to be dried, ground into a ne powder, placed
evenly on a sample stub, and spray- coated with conductive metal (usually gold) through the sputter
coater. The scanned sample done with high current density and narrow electron probe and information about the features of sample surface is extracted from the secondary electrons emitted from the
sample surface. This is of great concern because the nanoparticles have to withstand the electron
beams and the vacuum conditions that are likely to degrade polymers (Dawadi et al., 2021).
11.5.2.7 Nuclear Magnetic Resonance
Characterization of nanoparticles in terms of size and composition can be done using nuclear magnetic resonance (NMR). NMR offers a number of cues about the physicochemical properties of the
constituents in nanoparticles (Sandhiya & Ubaidulla, 2020).
11.5.2.8 Transmission Electron Microscopy (TEM)
Transmission electron microscopy TEM) is a high- amplication technique used to study the analysis of internal structures of materials using an electron beam that has to be passed through the
sample. It allows the examination of factors such as the structural surface of the carriers, their shape,
and formulations (Kumar & Seth, 2021). TEM images have clear and detailed information on the
size and dispersal intensities. The technique involves use of an electron beam through an ultra- thin
Nanoparticle Synthesis and Characterization for Herbal Drug Delivery 253
sample to obtain surface properties of the sample. Before subjecting a sample to TEM it has to
be diluted with distilled water, have a droplet placed on a carbon- stained copper grid and be possibly stained for visibility. To enhance the stability of nanoparticles, they can either be coated with
negative staining substances or the nanoparticles can be embedded in plastic to make them more
manageable. The other technique is to remove the sample, before placing it on vitreous ice and then
exposing it to liquid nitrogen (Sandhiya & Ubaidulla, 2020).
11.5.2.9 X-Ray Powder Diffraction (XRD)
X- ray diffraction (XRD) is a technique that studies the crystal structure of the powdered material
by observing the diffraction pattern, which is caused by X- ray pass through a powdered material.
It rapidly assesses the properties of crystalline materials and, if desired, produces the unit cell, and
atomic spacing data (Sandhiya & Ubaidulla, 2020). It is produced using an X- ray tube that has been
designed in a very elaborate manner to produce only one wavelength of radiation, something known
as monochromatic radiation. This radiation is deliberately beamed on the sample subject of analysis
(Sandhiya & Ubaidulla, 2020).
11.5.2.10 Evaluation of Recovery and Encapsulation Performance
Encapsulation efciency and recovery involve assessing the ability by which a drug is entrapped
in a carrier. After that, a volume of the sample is mixed with the organic solvent and then placed in
an ultrasonic bath for 30 minutes to extract the drug. The mixture is then spun at a xed rpm/min
for 10 min. and could be best estimated by High- Performance Liquid Chromatography (HPLC) or
ultraviolet (UV) spectroscopy (Sandhiya & Ubaidulla, 2020).
11.5.2.11 Atomic Force Microscopy
Atomic Force Microscopy (AFM) can be described as a complex imaging technique that employs
the contact modes of scanning at below the micrometer scale using a probe with atomic scale dimensions to measure the size of particles with great precision. By operating at contact and noncontact
modes, AFM forms topographical images with a high degree of resolution (Yadav et al., 2014). Its
capability to image non- conducting samples without special treatment makes it invaluable in visualizing complex biological as well as polymeric nano- and microstructures. Additionally, AFM stands
out by providing the most accurate description of particle size and size distribution without the need
for mathematical processing (Chakraborty et al., 2016).
11.5.2.12 UV-Visble Spectroscopy
An experiment sample is positioned halfway between the light source and a photodetector – a device
used in detecting and measuring the intensity of light striking (Kumar et al., 2012). In the UV- visible
absorption spectroscopy, the amount of intensity of a UV- visible light beam is determined before
and after passing through the sample. From these measurements, one can compare the HWHM at
two different wavelengths and thereby deduce the spectrum of the sample as a function of wavelength. As a rule, this information is presented in the form of an absorption spectrum where the
ordinate is the absorbance and the abscissa is the wavelength (Sandhiya & Ubaidulla, 2020).
11.5.2.13 Surface Plasmon Resonance
Nanoparticles exhibit specic absorption resonance wavelengths based on the natural frequency
of surface electrons interacting with light photons. This interaction involves oscillation against the
restoring force of positive nuclei, establishing a resonance condition (Sandhiya & Ubaidulla, 2020).
Nanoparticles at the nanoscale display unique optical properties not found in bulk materials or individual atoms. The optical characteristics of nanoparticles are heavily inuenced by particle size and
the surrounding medium. Additionally, UV light can be utilized to observe particle agglomeration,
as the movement of nanoparticles towards each other changes their pH, leading to their aggregation
(Al- Gebory & Mengüç, 2018).