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Pearson:
1.2 Nanotechnology:
- Nanotechnology: A branch of materials science that investigates the design properties and applications of materials produced on this scale.
- Nano - Particles larger than individual atoms, but smaller than the wavelength of light, thus cannot be viewed through optical microscopes
- Nanoscale: structures that are between 1 - 100 nanometers across.
- Nanometer (nm): $10^{-9}$ m wide
- Nanomaterials: substances that can be both natural and synthetic, that are composed of single units that exist in the nanoscale.
- Family of carbon molecules called fullerenes!!
- 3 dimensional structures formed by networks of carbon
- Most prominent one is one that forms a cylindrical tube called carbon nanotube
- Formed from a flat, 2-dimension layer of carbon atoms arranged in hexagons, known as graphene.
- Carbon nanotubes are really strong and stiff
- Top-down fabrication:
- Starts with material of a larger scale than desire, which is selectively removed or the size of the material is progressively reduced, by grinding, until the required size and shape is achieved.
- Most commonly used technique for manufacturing
- Advantages:
- Large quantities of material can be produced
- Very cheap
- Decent uniformity
- Disadvantages:
- Limited to simplicity
- Limited to scale of tools (how precise can it be?)
- Bottom-up fabrication:
- Physically growing, or building, materials atom by atom/molecule by molecule.
- Like chemical syntheses, but on a nanoscale.
- ‘Self-assembling’ nanomaterials?
- Nanoparticles:
- A specific type of nanomaterials, usually spherical particles with diameters of about 1-100 nm.
- In this size range, properties start to change. e.g. Gold is usually golden, but in nanoparticles it can take numerous colours.
- Normally sunscreens contain metal oxides, however when zinc nanoparticles are used, they interact with light differently and appear clear.
- Colloids:
- A mixture where one insoluble substance is dispersed in another. Colloids contain particles on the nanoscale that do not settle out of the mixture over time.
- A homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance
4.4 Metallic Nanomaterials:
Lucarelli :)
8.9: Fullerenes:
- A recently discovered allotropic form of carbon.
- A new group of fullerenes, Carbon Nanotubes was discovered in Japan.
- Fullerenes: Three-dimensional structures formed by networks of carbon atoms.
- Visualise carbon nanotubes as a graphene sheet rolled into a cylinder shape.
- Ends of CNTs are usually open or capped off using a hemispherical arrangement of carbon atoms bonded into interlocking pentagon and hexagon arrangements.
- CNTs are $1\times10^{-9}$m or 1 nanometre wide by diameter, but can be as long as several micrometres - a thousandth of a millimeter, $1 \times 10^{-6}$.
- CNTs can have an unlimited length, and can be produced with multiple walls with multiple concentric CNTs with increasing diameter being fit into one another. (Multi Walled Nanotubes (MWNTs))
- Atoms in CNTs are bonded through covalent bonds, giving CNTs a lot of strength/flexibility.
- They are also very light as they are comprised of carbon. This creates a super-strong lightweight material.
- CNTs also have weird electrical properties.
- Used as semiconductors/conductors.
- Can conduct 1000 times better than copper and silver.
- They can conduct with little to no heating effect (radiation emitted?)
- This means CNTs have a lot of potential for electrical devises.
- Fullerenes have a lot of surface area, and can be molecular containers. They also bond to surfaces and other structures really well.
- Thus, they have many applications
- Nanotechnology: A new field of scientific endeavour focused on the study and potential application of fullerenes, nanoparticles and other similar structures.
8.10 Nanotechnology:
- Nanoparticles: Particles with at least one dimension in the 1-100 nanometre range.
- Nanoparticles have unique properties due to quantum effects, as a result of a small particle size.
- For example, Zinc and Titanium oxide are commonly used in sunscreen and cosmetics.
- In general, they are used as “macro particles”. This means small particles but larger than nanoparticles.
- This makes a visible white opaque layer!
- Instead, using $ZnO$ and $TiO_2$ as nanoparticles allows for a quantum effect, as they become invisible while still absorbing UV.
- In general, these quantum effects greatly impact optical properties.
- This is because nanoparticles, with their quantum effects, interact differently with light.
- However, differently sized nanoparticles also can produce unique properties.
- For example, Cadmium Selenide as a nanoparticle will produce different visible light when UV light is shone onto a solution containing them.
- These particles are known as “quantum dots”.
- (They affect the wavelength of light, with smaller dots producing shorter wavelengths and vice versa.)
- CNTs also have electrical properties that differ from Carbon’s.
- These electrical properties make it a really good conductor and semiconductor, allowing computers to be compacted further as semiconductors are built within a nanometre’s range.
- Silver has many antibacterial and antifungal effects, which is further enhanced when used in nanoparticle form.
- This is due to an increase in surface area, a common property of fullerenes.
- Nanodevice research!!! - uses in medical field, e.g. for diagnosis/detection/treatment of cancer
- Dendrimers - nanosized nanoparticle structures
- They can be designed as molecular carriers, which can carry molecules that recognise cancer, kill cancers, recognise a dead cancer cell, signal a cancer cell’s death, etc.
- Using dendrimers in this fashion, one can kill cancer cells, while reporting its efficiency.
- NOTE: This would mean literally no side effects, as its only killing cancer (the bad stuff) and doesn’t work like radiation which also kills healthy cells (the good stuff)
- These devices are called therapeutic nanodevices, and use quantum dots, nanoshells and nanopores.
8.11 Nanocomposites.
- Nanoparticles have been around for a long time, despite nanotechnology being very new.
- Carbon black(soot), an amorphous form of carbon is largely comprised of carbon particles in the nanometre range.
- Used as an additive in rubber for tyres, as its really strong. Tyres have 25% of its rubber made of carbon black.
- More amounts of carbon black will make the rubber more conductive, preventing build-ups of static electricity. - useful to prevent accidents.
- Nanocomposites: Materials created by adding nanosized particles of one material to a matrix of a bulk material (metal, polymer, ceramics(recall Pearson))
- Nanocomposites have numerous advantages and more useful properties:
- Mechanical strength
- Electrical/thermal conductivity
- Optical properties
- Used in manufacturing of plastics - nanotubes or graphene is added.
- 1-5% concentration of nanoparticles in nanocomposites can increase stiffness by 50%, and mechanical strength by 20%
- They slow down cracks from forming as they have high tensile strength.
- Can be used in lithium ion batteries - comprised of electrodes, which are usually made of graphite - carbon nanotubes, graphene sheets and nanocomposites have been suggested as replacements.
- Carbon-silicon nanocomposite material seems to be promising
- Silicon has good energy storage, but breaks down as it contracts and expands when charges are discharged.
- This is where nanoparticles of carbon come in, as they can maintain a rigid structure, while still having the high energy storage of silicon.
Examples of Nanomaterials:
- Carbon
- Gold
- Silver
- Zinc Oxide
- Cadmium selenide
- Titanium oxide
- Amorphous silica ($SiO_2$)
- Copper
- Iron
Advantages of nanomaterials: have been listed above
Disadvantages of nanomaterials:
- SAFETY CONCERNS:
- important rule: the properties of nanoparticles differ from the parent material in bulk form.
- e.g. glass fibre particles are very harmful, and brick workers use breathing masks to prevent exposure. In contrast, glass in bulk form is inert and harmless.
- Very hard to make:
- The production of nanomaterials requires a complex design and production infrastructure. There are numerous means to create nanoparticles, however they are usually very expensive and exclusive.
WACE Study Guide Review:
- In general, the properties (physical + chemical) of bulk materials remains constant regardless of size.
- However, as particle size becomes small, then properties can change drastically.
https://www.dummies.com/article/academics-the-arts/science/nanotechnology/why-you-want-nanotechnology-in-your-life-198989
IJSO_Bohr__Spectra_and_the_Quantum_Atom_4.pdf
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