Brief introduction to nanomaterials, synthesis of nanomaterials via various methods

1. Advanced Nanomaterials and Their Applications
Dr.C. Karthikeyan
Dept. of Energy Science
Alagappa University, Karaikudi
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2. Content
• Significance of nanoscale – Surface area, quantum confinement effect,
penetration of a barrier – Tunnel effect. Types of nanocrystals – Zero
dimensional – One dimensional – Two dimensional – Three dimensional
nanostructured materials – Metals – Semiconductors – Ceramics –
Composites – Size dependent properties – Mechanical, physical and
chemical – Uniqueness in these properties compared to bulk and
microscopic materials.
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3. UNIT-I: INTRODUCTION
➢The nanoscopic scale (or nanoscale) usually refers to structures with a length
scale
➢usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter.
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5. • Mouse scan –circulation by radiolabeled nanoparticle
Molecular machine- nanotechnology
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6. • Nano scale materials often have very different properties from bulk
materials
• Ex: Colour and reactivity
Particle at nanometre size
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7. • At least one dimension (height, length or depth) is less than 100 nm
• Less than 100 nm thick, called nano film
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9. Natural nanomaterials
Peacock feather
Viral Capsid
Lotus effect Brazilian Crystal Opal
SEM micrograph of a butterfly wing
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10. Unique Characteristics of Nanoparticles
• Large surface to volume ratio
• High percentage of atoms/molecules on the surface
• Surface forces are very important, while bulk forces are not as
important.
• Metal nanoparticles have unique light scattering properties and
exhibit plasmon resonance.
• Semiconductor nanoparticles may exhibit confined energy states in
their electronic band structure (e.g., quantum dots)
• Can have unique chemical and physical properties
• Same size scale as many biological structures
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11. Nanoparticles Synthesis Methods
Physical processing methods
Physical and chemical processing methods
Top-Down:
Start with bulk material and cut away materials to
make Nanoparticles
Bottom-Up:
➢Building the materials to Nanoparticles.
➢Atom by atom, molecule by molecule or cluster by
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15. Significance of Nanoscale:
• The quantum mechanical properties of the particles influence at the nanoscale
➢By nanoscale design it is possible to vary micro and macroscopic properties
such as charge capacity, magnetization, melting temperature without changing
their chemical composition.
• Creation of new improved products.
• Availability of stronger, tougher and lighter materials for construction and
engineering.
• Nanoscale components have high surface area to volume ratio making them idle
for the use in composite materials, drug delivery and chemical storage.
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16. Significance of Nanoscale
• Nanosized metallic powders have been used for the production of the gas
tight materials and porous coatings.
• Nanostructured metal clusters and colloids are used in the special
catalytic applications.
• Nanostructured metal oxide films are used even as the gas sensors.
• Nanostructured metal oxide finds applications in rechargeable batteries for
cars and consumer goods
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17. Significance of Nanoscale:
• Sophisticated health treatment by using the nano particles in the drug delivery.
• Cheaper and cleaner energy production.
• Nanophase ceramics which are very ductile a elevated temperatures as compared
to the normal ones.
• Nanostructured semiconductors are used as window layers in solar cells.
• Cleaner drinking water due to the creation of filters (made by nano) that can
entrap organisms and toxins.
• Cleaner environment by removal of pollutants from the environment.
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18. Significance of Nanoscale
• Composite made by nanoparticle become more stronger (ie: grain size (10
nm) 7 times harder and tougher than grain size (100 nm)
Large surface area Chemically more active
Properties change
at nanoscale
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19. Significance of Nanoscale- Surface area
• Generally, surface area to volume ratio has a significant effect on the properties of
the material
• Firstly, materials made up of nanoparticles have a relative larger surface area when
compared to the same volume of material made up of bigger particles (bulk).
What is surface area to volume ratio?
➢ Amount of surface area or total
exposed area of a body relative to its
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20. Significance of Nanoscale- Surface area
➢Nanoparticles shows different properties compared to large particles of the
same materials.
➢Force of attraction is weak in large scale but in nanoscale are strong
➢In nanoparticle surface to volume ratio is large
➢Generally, atom in the surface more reactive than centre, so large surface
area means the materials is more active.
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21. Colour change at nanoscale
• Cu- transparent at nano scale
• Au nanosphere (50 nm) – green in colour
• Au (100 nm) – Orange in colour
• Au Bulk – yellow
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23. Quantum confinement effects
• Quantum confinement effects describe electrons in terms of energy levels,
potential wells, valence bands, conduction bands, and electron energy band
gaps.
• The quantum confinement effect is observed when the size of the particle is
too small to be comparable to the wavelength of the electron
potential well – is region surrounding a local minimum of
potential energy.
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24. The synthesis of nanomaterials, including
1. Top-down and
2. Bottom-up approaches,
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25. Types of nanocrystals
What do you mean by nanocrystals?
• Nanocrystals are aggregates of atoms that combine into a “cluster” (less than 1 μm in
size).
• particle having at least one dimension smaller than 100 nanometres
• Typical sizes range between 10 and 400 nm.
• Have unique physical and chemical properties than bulk solids and molecules.
They play an important role in the fabrication of many devices and modified materials
because of their unique physical and chemical properties, such as a large surface-area-to-
volume ratio, and their high mechanical strength
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26. Nanoparticles
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27. Types of nanocrystals
• Nanomaterials can be categorized into four types such as:
(1) inorganic-based nanomaterials; - different metal and metal oxide
nanomaterials.
(2) carbon-based nanomaterials; - Fullerenes, carbon nanotubes, graphene
and its derivatives, graphene oxide, nanodiamonds, and carbon-based quantum
dots.
(3) organic-based nanomaterials; - liposomes, micelles, and polymer
nanoparticles,
(4) composite-based nanomaterials. (nanomaterials with composite structure) -
nanofibers, nanorods, nanoparticles, and carbon nanotubes.
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28. Nanocrystals in drug delivery systems
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31. Quantum dot
▪ Quantum dot is nanocrystals
▪ 2 to 10 nm
▪ Made by Semiconductor
▪ It is also called fluorescent semiconductor nanocrystals, once it excited
with UV light, they emit particular fluorescent colour, depending on the
dot’s size
❑ Have unique optical and electronic properties that differ from bulk
❑ Ex: CdSe, PbSe, PbTe CK 31

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33. • Computing
• Q-LED
• Photovoltaics devices –increase efficiency –made
by simple chemical method
• Solar cells
• Cancer cell imageing
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34. • https://www.youtube.com/watch?v=S-SOEBTplOM
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35. 0D, 1D, 2D and 3D
• According to dimensions,
• 0 D –nanoparticle
• 1 D- nanotube, nanorods
• 2D-Nanothinfilm, nanocoating, nanolayers
• 3D- nanoprisms, nanoflowers
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36. 0D:
• All the dimensions in nanoscale, no dimension other than nano
• Ex: Quantum dot, nanoparticle, nanocluster, nanodots
1D:
• One dimension larger than nano
• Major growth in one dimension & growth is limited other 2 dimensions.
• Ex: nanowire, nanorod, CNT
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37. 2D:
• Two dimension larger than nano
• Plat-like shape
• Ex: graphene, nanofilms, nanoplates, nanonetworks
3D:
• Not confined nanoscale in any dimensions
• All the 3 dimensions larger than nano
• Major growth in all the 3 dimensions
• More complicated structure
• Ex: Graphite, Diamond, nanocomposite bundle of nanowires
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39. METAL NANOPARTICLE
• The term metal nanoparticle is used to described nanosized metals with
dimensions (length, width or thickness) within the size range 1‐100 nm.
• The existence of metallic nanoparticles in solution was first recognized by Faraday in
1857 and a quantitative explanation of their colour was given by Mie in 1908.
• Usually: Au, Ag, Cu, Pt, Pd, Ru, Re…
• - but: Fe, Ni.. (very reactive, very explosive)
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41. Metallic Nanoparticles Synthesis
• Ideally, metallic nanoparticles should be prepared by a method which:
❑ reproducible
❑ May control the shape of the particles
❑ Yields monodisperse metallic nanoparticles
❑ easy, cheap
❑ Use less toxic precursors: in water or more environmentally benign solvents (e.G.
Ethanol)
❑ Use the least number of reagents
❑ Use a reaction temperature close to room temperature
❑ With as few synthetic steps as possible (one‐pot reaction)
❑ Minimizing the quantities of generated by‐products and waste.
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42. Influence of reducing reagents
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43. Influence of reducing reagents
Sodium citrate Citric acid
SEM- Gold nanoparticles
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44. • TEM- Gold nanoparticles
• various pH range
a) 4.0
b) 4.5
c) 5.0
d) 5.5
e) 6.0
f) 6.5
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47. • In Catalysis:
• Catalysts based on metal NPs are:
• Highly active
• Selective
• Exhibit long lifetime for
• several kind of reactions
Applications of homogenous catalysts:
‐Olefin hydrogenation
‐Nitrile hydrogenation
‐Photoinduced electron transfer
Applications of heterogeneous catalysts:
Oxidation reactions
Hydrogenation
Hydrodechlorination
Synthesis of H2O2
Water ‐gas shift
• Colloidal Pt/Ru catalysts are used in direct methanol fuel cells –DMFCs
➢ Uniform metal nanoparticles – used to design of new ˝supercomputers˝ having a superior data
storage capacity
➢ Nickel NPs are used as magnetic recording medium, electrical conductive pastes, battery
materials, etc.
Applications of Metal Nanoparticles
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48. Applications of Metal Nanoparticles
• Biological Applications
Magnetic nanoparticles used as
• For binding BSA (Bovine Serum Albumin)
• For drug delivery
• For bio‐sensing
• For bio‐separations
Sensors
1. Electrochemical sensors ‐the introduction of metal
NPs (mostly supported) on the electrode can:
decrease the overpotentials of many electrochemical reactions
turn into reversible some redox reactions that are normally
irreversible in conventional unmodified electrodes
Examples: sensitive NO, H2O2and sugar and amino sacid
sensors
2. Biosensors:
can enhance the electron transfer between biomolecules
Ag NPs supported on glass –used as selective biosensors for the
biotinstreptavidin system
Photocatalysis (Ag Nps)
‐water splitting
‐degradation of organic pollutants
Biology and Medicine:Ag is a highly antimicrobial material
used in:
‐water purification
‐wound care
‐medical devices
‐drog delivery CK 52