Nanoscience and Technology

Michael M Ngwenya (N02221351Y)

National University of Science and Technology
Zimbabwe
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CONTENTS
• Nanoscience (3)
• Nanotechnology (4)
• Nanoparticle Properties (5)
• Nanotechnology Particle Synthesis (6)
• Types of Nanotechnology (7)
• Synthesis - Physical and Chemical (8-16)
• Chemical Phenomenon (13)
• Applications (17-22)
• Analytical Methods (23)
• Nano-Pros and Cons (24)
• References (25) 2
• Nanoscience is the study of matter and phenomena at the nanoscale,
which is about 1 to 100 nanometers (10-9) in size. Nanoparticles are
microscopic particles that have a diameter less than 100 nm.

• A nanometer is one billionth of a meter, or about the length of a few atoms.

Nanoscience explores the unique properties and behaviors of materials at
this scale, such as quantum effects, surface effects, and self-assembly.

• Nanoscience also involves the creation and manipulation of nano particles,

nanostructures, which are structures that have at least one dimension in
the nanoscale.

• Some examples of nanostructures are nanowires, nanotubes, nanosheets,

and nanodots.
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Nanotechnology
• Nanotechnology is the application of nanoscience to create new
products, devices, and systems that have new functions and benefits.

• Nanotechnology uses nanomaterials, which are materials that have

nanoscale features, such as nanocrystals, nanocomposites, and
nanocoatings.

• Nanotechnology also uses nanodevices, which are devices that operate

on the nanoscale, such as nanosensors, nanomotors, and
nanoelectronics.

• Nanotechnology aims to exploit the advantages of nanomaterials and

nanodevices, such as high strength, low weight, high surface area, high
reactivity, and high conductivity. 4
Nanoparticle Properties
Some of the physical properties of nanoparticles are:

• They have a very large surface area to volume ratio, this makes them more
reactive and sensitive to external stimuli, such as light, heat, electric fields,
and magnetic fields.

• They have quantum effects, which means they behave according to the
rules of quantum mechanics rather than classical physics. This affects their
electronic, optical, magnetic, and mechanical properties, such as
conductivity, band gap, fluorescence, magnetization, and strength.

• They have size-dependent properties, which means their properties change

as their size changes. For example, the color of gold nanoparticles can vary
from red to purple depending on their size, because of the way they
interact with light.
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Nanotechnology Particle Synthesis
• Two basic strategies are used to produce nanoparticles: 'top-down' and 'bottom-up'. The
term 'top-down' refers here to the mechanical crushing of source material using a milling
process.
• In the 'bottom-up' strategy, structures are built up by chemical processes. The selection of
the respective process depends on the chemical composition and the desired features
specified for the nanoparticles.

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Types Of Nanotechnology Synthesis
The different types of nanotechnology are classified according to how they proceed (top-down
or bottom-up) and the medium in which they work (dry or wet):

Descending (Physical/top-down)
Mechanisms and structures are miniaturised at the nanometric scale — from one to 100
nanometres in size —. It is the most frequent to date, especially in electronics.

Ascending (Chemical/bottom-up)
Builing up a nanometric structure from a molecule, through a mounting or self-
assembly process you create a larger mechanism than the one you started with.

Dry nanotechnolgy
It is used to manufacture structures in coal, silicon, inorganic materials, metals
and semiconductors that do not work with humidity.

Wet nanotechnology
It is based on biological systems present in an aqueous environment — including genetic
material, membranes, enzymes and other cellular components . 7
 Synthesis - Physical Method (Top-down)
• Ball Milling - is a grinding process used to • Laser Ablation - involves using a high-energy
reduce bulk materials into fine particles, laser (1000-1350℃) to vaporize a target
which can be used to form nanoparticles. material, which then condense to form
Effective for producing a wide range of nanoparticles. Produces nanoparticles with
nanoparticles, including metal, ceramic,
and polymer nanoparticles. high purity and control over size and shape.

Neodymium-doped
Yttrium Aluminium
Garnet Laser
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Nucleation and Growth
• Nucleation is the phenomenon of the initiation of formation of nanocrystals in
solution. Small particles or nuclei appear, which are capable of growing. It is the
creation of nuclei upon which growth can occur.
Types of Nucleation
• Homogenous nuclei - Simultaneous formation and uniform distribution in solution.
• Heterogenous nuclei - Nucleation at different time.
Growth
• Arrested precipitation - Nuclei centers formed by vigorous mixing of the reactants.
This is precipitation by inducing starving conditions, if concentration growth is kept
small, nuclei growth is ceased due to lack of material.
• Oswald Ripening - it is whereby small particles dissolve and are consumed by larger
particles. As particles increase in size, solubility decreases.
Factors that affect growth are the stabilizing (capping) agents, concentration of
reactants, reducing agent, pH and time for heating. 9
Stabilizing agent
• Is a substance that is used to prevent the nanoparticles from clumping together. It
maintains the stability and dispersibility of the nanoparticles in a solution or
suspension.
Examples: Sodium Dodecyl Sulfate (SDS), polymers such as Polyvinyl Alcohol (PVA) or
Polyvinyl pyrolidone (PVP), and various surfactants.
Role of Stabilizing agent
• It prevents uncontrollable growth of particles, controls growth rate and particle size.
This facilitates particle solubility
Types of stabilization
• Steric Stabilization - the metal centers are surrounded by layers of material that are
bulky like polymers (silica polymers).
• Electrostatic stabilization - ions are adsorbed on the surface of the particles by
creating an electrical double layer. The coulombic repulsions between individual
particles prevents agglomeration.
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Precipitation
• The precipitation of solids from a metal ion containing solution is one of the most
frequently employed production processes for nanomaterials.

• Metal oxides as well as non-oxides or metallic nanoparticles can be produced by

this approach. The process is based on reactions of salts in solvents.

• A precipitating agent (sodium hydroxide, ammonia or hydrochloric acid) is added to

yield the desired particle precipitation, and the precipitate is filtered out and
thermally post-treated (at 60-80℃).

• In precipitation processes, particle size and size distribution, crystallinity and

morphology (shape) are determined by reaction kinetics (reaction speed). The
influencing factors include, beyond the concentration of the source material, the
temperature, pH value of the solution, the sequence in which the source materials
are added, and mixing processes.
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Synthesis of Silver Nanoparticles (Including Ag, Au, Pt, Pd, Co, etc)
• It involves preparation of the silver precursor, chemical reduction of the precursor to form nanoparticles
by using a reducing agent (Trisodium Citrate, Absorbic acid or Sodium borohydride) and stabilization to
prevent agglomeration.

M+ + Reductant -> Nanoparticle

• A suitable silver compound is used, Silver nitrate (AgNO3).

• Silver ions are reduced by chemical reduction using a reducing agent such as Trisodium Citrate (Na3C6H5O7)
by application of heat (maintained at 90-100℃):

3AgNO3(aq) + Na3C6H5O7(aq) -> 3Ag(s) + 3NaNO3(aq) + C6H5O73-(aq)

• The silver nanoparticles (AgNP's) are stabilized to prevent agglomeration and forming larger particles.
• Stabilizing agent (PVA or PVP on slide 10) adsorbs onto the
surface of the nanoparticles which prevents the AgNP's
from into contact with each other.

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Surface Plasmon Resonance (SPR)
phenomenon
It is the collective oscillation of the free
electrons on the surface of the
nanoparticles when they interact with
the electromagnetic radiation (EMR).
• Incident light creates oscillations on the
surface of the nanoparticles and EMR is
absorbed. This allows us to see the
unexpected colours of the metal colloids.
• The SPR wavelength and intensity
depend on the size, shape and
distribution of the nanoparticles, as well
as the surrounding medium.
• Silver colloids have a yellow colour while
Gold have Ruby red colour.
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 The sol-gel process is a method for producing solid materials from small molecules, especially
metal oxides.
The term sol refers to dispersions of solid particles in the 1-100 nm size range, which are finely
distributed in water or organic solvents.
It involves four main steps: Hydrolysis, Condensation, Gelation and Drying.
• Hydrolysis is the reaction of metal alkoxides or metal salts with water to form metal
hydroxides and alcohols. Titanium alkoxide can react with water to form titanium
hydroxide and ethanol (temperature maintained at 25-80℃):
Ti(OR)4(s) + 4H2O(l) -> Ti(OH)4(aq) + 4ROH(aq)
• Condensation is the reaction of metal-hydroxides with each other or with metal alkoxides
to form metal-oxygen bonds and water or alcohols:
Ti(OH)4(aq) + Ti(OR)4(aq) -> 2TiO2(s) + 4ROH(aq)
• Gelation is the formation of three-dimensional network of
metal-oxygen bonds that traps the solvent molecules
with the pores. This gives rise to polymerisation of
long chained compounds. 14
• The resulting product is a wet gel, which is a solid like material with high
porosity and surface area.
• Drying is the removal of the solvent molecules from the wet gel by
evaporation, supercritical extraction, or freezing-drying.
• The resulting product is a dry gel, which is a porous ceramic material with
nanoscale particles and pores.
• Due to the high porosity of the network, the particles typically have a large
surface area, i.e. several hundred square meters per gram.
• For coatings, the alkoxide initial solution of the sol-gel process can be
applied on surfaces of any geometry. After the wetting, the build-up of the
porous network takes place through gel formation, yielding thicknesses of
50-500 nm (coatings explained on next slide).
• Thicker layers, suitable as membranes for example, are created by repeated
wetting and drying. The sol-gel process can also be used to produce fibers.
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• Coating can help in making
xerogels by providing a
protective layer on the
surface of the nanoparticles
which can improve their
stability and prevent
agglomeration.

• Common coating materials

include silica polymers.

• Xerogel is a solid formed by

the dehydration of a gel.

• Aerogel is a porous, ultralight

solid-state substance, similar
to gel, in which the liquid
component is replaced with
gas.
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• Precipitation mentioned on slide 11
Applications - Nanoceramics
• Nanoceramics are ceramic materials fabricated from ultrafine particles, less than 100 nm
in diameter (as mentioned on slide 14), that have improved and unique properties
compared to conventional ceramic materials.

• Tile making is a process of producing ceramic tiles for covering floors, walls, and roofs.
Nanoceramics are used to enhance the strength, durability, and appearance of the tiles by
reducing the grain size, increasing the density, and modifying the surface properties of the
tiles.

• Nanoceramics are used as adsorbents, catalysts, membranes, and filters to remove

pollutants such as heavy metals, organic compounds, and microorganisms from water.

• Nanoceramics are used for tile making and water purification because of their high surface
area, porosity, and functionality. Water purification is a process of removing contaminants
from water to make it safe and clean for various purposes (continues on slide 18).

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• Nanoceramics are a type of nanomaterial that
have applications in water purification. They
can clean water by using a water purification
reactor that consists of Silver-Iron (Ag-Fe)
nanoparticles.

• Raw water flows into a water purification

reactor, where the nanoparticles are able to
attract and remove impurities from the water,
such as bacteria, viruses, heavy metals, and
organic pollutants.

• The water then flows through a treatment

process where the nanoparticles are separated
from the water using a magnetic rod. This
results in purified water that is safe for
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consumption.
• Nanotubes are nanometer-scale hollow tube-like
structures that are made of different kinds of
atoms or molecules.

• One of the most common and well-studied types

of nanotubes are carbon nanotubes (CNTs),
which are made of carbon atoms arranged in a
hexagonal lattice.

• Carbon nanotubes have remarkable properties,

such as high tensile strength, thermal
conductivity, and electrical conductivity. Carbon
nanotubes can be classified into three types:
armchair, zigzag, and chiral.

• Examples on next slide along with polymers and

on slide 22. 19
• Polymers are used in nanotechnology for various purposes, such as creating new materials,
enhancing the properties of existing materials, and delivering drugs or other molecules to
specific targets. Some examples of polymers used in nanotechnology are:

• Polymer-based nanoparticles: Composed of polymers or polymer-coated materials. They can

be used for drug delivery, imaging, sensing, catalysis, and other applications. For instance,
polymer-coated gold nanoparticles can be used as contrast agents for optical imaging, or as
carriers for anticancer drugs .

• Polymer nanocomposites: These are materials that combine polymers with nanoscale fillers,
such as carbon nanotubes, graphene, nanodiamonds, or metal oxides. For example, polymer
nanocomposites with carbon nanotubes can be used for flexible electronics, sensors,
actuators, or energy storage devices.

• Polymer nanofibers: Produced by techniques such as electrospinning, self-assembly, or

template synthesis. They can be used for tissue engineering, wound healing, drug delivery,
filtration, or scaffolds for cell growth. For example, polymer nanofibers with antibacterial
agents can be used for wound dressing or infection prevention. 20
Applications - Business of Nanotechnology
• The business of nanotechnology is the application of nanotechnology to create new products, services,
and markets that can generate economic value and social benefits. Sectors of impact are:

Healthcare - Nanotechnology can enable the development of new diagnostic tools, drug
delivery systems, therapeutics, and regenerative medicine. Nanosensors can detect diseases at
an early stage, nanoparticles can target and destroy cancer cells.

Electronics - Nanotechnology can improve the performance, functionality, and miniaturization

of electronic devices, such as transistors, memory, displays, sensors, and batteries. Nanowires
can increase the speed and density of circuits.

Energy - Nanotechnology can contribute to the production, storage, and conversion of clean
and renewable energy, such as solar (solar cell), wind, hydrogen, and biofuels. Nanomaterials
can increase the absorption and conversion of sunlight, nanocatalysts can facilitate the splitting
of water and the reforming of biomass.

Environment - Nanotechnology can help to prevent, monitor, and remediate environmental

pollution, such as air, water, and soil contamination. For example, nanofilters can remove 21
contaminants and pathogens from water.
Applications - Nanotechnology In Sports
• Carbon nanotubes (CNTs on slide 19) are nanoscale tubes of carbon atoms that have
exceptional mechanical, electrical, and thermal properties. CNTs can be used to
reinforce sports equipment, such as tennis racquets, golf clubs, and bicycles, to
make them stronger, lighter, and more responsive.

• Nanocoatings are thin layers of nanomaterials that can modify the surface
properties of sports materials, such as hardness, wear resistance, corrosion
resistance, and hydrophobicity. Nanocoatings can also be applied to sports apparel,
such as shoes, gloves, and jackets, to provide water repellency, stain resistance, and
antibacterial protection.

• Nanosensors are nanoscale devices that can detect and measure physical, chemical,
or biological signals. Nanosensors can measure parameters such as speed,
acceleration, force, temperature, heart rate, blood pressure, and glucose level.
Nanosensors can also provide feedback, alerts, and recommendations to optimize
the training, recovery, and performance of athletes. 22
• SPR spectrometer - measures changes in the refractive index of a thin
metal film on a sensor surface.

• Transmission Emission Microscopy (TEM) - to visualiz the size and

morphology of the nanoparticles.

• X-ray Diffraction (XRD) - used to determine the crystalline structure of

the nanoparticles.

• Electron microscopy, Acoustic spectroscopy, Optical microscopy,

Electrozone sensing, PCS (Dynamic Light Scattering)

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They can create challenges and
limitations for the industrial scale-
up and commercialization of
nanoproducts, such as the high cost
and complexity of the synthesis and
characterization of nanoparticles,
and the compatibility and
integration of nanoproducts with
existing systems and infrastructures.
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• Nanoscience Definition & Meaning - Merriam-Webster.
https://www.merriam-webster.com/dictionary/nanoscience.

• Nanotechnology vs Nanoscience: Meaning And Differences.

https://thecontentauthority.com/blog/nanotechnology-vs-nanoscience.

• Nanoscience explained — Science Learning Hub.

https://www.sciencelearn.org.nz/resources/1640-nanoscience-explained.

• Nanotechnology Applications, examples and advantages - Iberdrola.

https://www.iberdrola.com/innovation/nanotechnology-applications.

• Nanotechnology Innovations & Business Opportunities: A Review - SSRN.

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=2779151.

• Gopinath, P., Synthesis of Nanomaterials by Physical and Chemical method.

Lec 3. Department of Biotechnology Indian Institute of Technology
Roorkee. Accessed on Youtube.
• Marvel Studios, Antman (2016), Antman and the Wasp (2018).

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The End

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