Bulk and surface properties of matter including nanoparticles

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Particle Size Categories

  • Particles are grouped by diameter into coarse particles, fine particles, and nanoparticles.
  • Coarse particles (also called particulate matter or dust) have diameters between 1 × 10⁻⁵ m and 2.5 × 10⁻⁶ m.
  • Fine particles have diameters between 100 and 2500 nm (1 × 10⁻⁷ m to 2.5 × 10⁻⁶ m).
  • Nanoparticles are between 1 and 100 nm in size and usually contain only a few hundred atoms.
  • Atoms and simple molecules are around 100 times smaller than nanoparticles.
  • The terms PM2.5 and PM10 describe fine and coarse particles respectively, based on size in micrometres.

Scale

Scale

Nanoparticles and Nanoscience

  • Nanoscience is the study of structures that are 1–100 nm in size.
  • Research into the production and application of nanoparticles is called nanotechnology.
  • Nanoparticles are much smaller than fine particles, which are themselves smaller than coarse particles.
  • A nanometre is 1 × 10⁻⁹ m (0.000 000 001 m).
  • A micrometre is 1 × 10⁻⁶ m.
  • Nanoparticles may have different properties from the same material in bulk form.

Tio2

Tio2

Surface Area to Volume Ratio

  • Nanoparticles have a very high surface area to volume ratio.
  • As particles decrease in size, their surface area increases in relation to their volume.
  • As the side of a cube decreases by a factor of 10, the surface area to volume ratio increases by a factor of 10.
  • This high ratio is why nanoparticles may have different properties from the same material in bulk form.
  • It also means that smaller quantities of nanoparticles are needed to be effective compared to materials with larger particle sizes.
  • The surface area to volume ratio is important in catalysis and surface chemistry: the higher the ratio, the more surface area is available for reaction, so the better the catalyst.

Ratio

Ratio

Uses of Nanoparticles

  • The main industrial application of nanoparticles is in catalysis due to their high surface area to volume ratios.
  • Titanium dioxide in nanoparticle form is used in sunscreens as it blocks UV light but leaves no white marks on the skin.
  • The same chemical in bulk form is used as a white pigment in paints.
  • Fullerenes (nanoparticles made of carbon) are used in medicine and drug design as they are more easily absorbed and can deliver drugs to target areas more effectively.
  • Fullerenes are also used in electronic circuitry and as coatings for artificial limbs and joints.
  • Silver nanoparticles are sprayed onto fibres of medical clothing and surgical masks, giving the flexibility of a material with the added benefit of the antibacterial properties of silver.
  • Silver nanoparticle coated clothing can act as a built-in deodorant.

Sunscreen

Sunscreen

Advantages and Disadvantages of Nanoparticles

  • Nanoparticles have widespread uses and applications that can provide an immense advance in materials technology.
  • The use of nanoparticles is in its early stages, so there are still many unknown factors and potential risks.
  • There is a lack of understanding about how nanoparticles may affect health.
  • Although there have been no serious short-term side effects, there could be long-term side effects not yet detected because they haven't been in use long enough.
  • Even a small amount of toxicity in a nanoparticle would be multiplied due to the high surface area to volume ratio.
  • Nanoparticles are not easily disposed of by the body, which is a cause for caution in medical applications.

Risks

Risks

Ceramics, Polymers, Composites and Metals

  • Glass ceramics are transparent, strong, and insulate against heat; they are more durable than other materials, making them suitable for windows.
  • Soda-lime glass is made by heating a mixture of limestone, sand, and sodium carbonate until it melts, then cooling it.
  • Borosilicate glass is made using sand and boron trioxide and has a higher melting point than soda-lime glass.
  • Clay ceramics are hardened materials that resist compressive forces; clay hardens at high temperatures and when fired produces a very strong and hard material.
  • Polymers can be tailor-designed to have specific properties, can be opaque or transparent, are usually tough and flexible, and are poor conductors of heat and electricity.
  • Composites are made from two components: a reinforcement and a matrix; the matrix binds the reinforcement together.
  • Common composites include fibreglass and steel reinforced concrete; their properties depend on the reinforcement and matrix used, so they can be tailor-engineered.
  • Metals are shiny, malleable, and ductile, can be mixed to form alloys, and are good conductors of heat and electricity.

Materials

Materials

Effective Use of Materials

  • Glass and steel are extremely useful building materials due to their high strength and durability.
  • Glass is transparent, hard, and has high compressive strength, making it ideal for walls and windows.
  • Metals are used in electrical cabling and electronics because they conduct electricity; copper is commonly used as it is a good conductor and very malleable.
  • Aluminium is strong but light, giving it a high strength-to-weight ratio, making it ideal for airplanes.
  • Steel reinforced concrete has immense tensile and compressive strength, allowing it to be used as columns and supporting structures.
  • Carbon-fibre composites are extremely strong and low weight, used in aviation, aeronautics, and professional racing bicycles.
  • Polymers are poor conductors of heat and electricity, making them good thermal and electrical insulators; they are used to insulate electrical wiring to prevent shocks and overheating.
  • The low melting points and flexibility of polymers enable them to be moulded into many shapes.

Materials

Materials

Key Terminology and Calculations

  • Nanoparticle: a particle between 1 and 100 nm in size.
  • Coarse particle: a particle with a diameter between 1 × 10⁻⁵ m and 2.5 × 10⁻⁶ m.
  • Fine particle: a particle with a diameter between 100 and 2500 nm.
  • Surface area to volume ratio: the amount of surface area per unit volume; it increases as particle size decreases.
  • Nanoscience: the study of structures that are 1–100 nm in size.
  • Catalyst: a substance that increases the rate of a reaction without being used up.
  • Order of magnitude: a rough estimate of size, often to the nearest power of ten.
  • You should be able to calculate surface areas and volumes of cubes, and make order of magnitude calculations.

Slide

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Soal latihan

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  1. 1.Place the following particles in order of size, starting with the smallest.

    Easy
    • Coarse particles
    • Nanoparticles
    • Fine particles
  2. 2.What is the approximate size range of nanoparticles?

    Easy
    • A1–100 nm
    • B100–2500 nm
    • C2500–10,000 nm
    • D1–100 μm
  3. 3.Particle X has a diameter of 2.5 × 10⁻⁷ m. Which category is it most likely to belong to?

    Easy
    • ACoarse particles
    • BFine particles
    • CNanoparticles
    • DAtoms
  4. 4.Why are nanoparticles effective catalysts even when only a very small quantity is used?

    Easy
    • AThey are reactive compounds
    • BThey have a high surface area to volume ratio
    • CThey have a low boiling point
    • DThey can adopt different shapes
  5. 5.Nanoparticles usually contain only a few hundred atoms.

    Easy

    True or false?

  6. 6.As the side of a cube decreases by a factor of 10, its surface area to volume ratio decreases by a factor of 10.

    Easy

    True or false?

  7. 7.Which of the following are uses of nanoparticles? (select all that apply)

    Medium
    • ACatalysts
    • BSunscreens
    • CDrug delivery to cells
    • DExtracting iron from its ore
    • EDeodorants in clothing
  8. 8.Which of the following is NOT a use of nanoparticles?

    Easy
    • ADrug delivery to cells
    • BExtracting iron from its ore
    • CProducing suncreams
    • DCatalysts

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