Nano-materials

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Most of these are mine, but I have stolen adapted some of Ajay’s notes. I’m not gonna tell you, you can guess.

• 1 nanometer (nm) is equal to $1\times 10^{-9}$ meters
• Nanotechnology: study of how to produce and control very small structures, i.e. in the nano-scale
  • The nanoscale is anything between the size of 1 to 100 nano-metres

Nanoparticles

• Nanoparticles are particles of matter in the size of the nanoscale
• At least one dimension within the nanoscale
• Nanoparticles have different chemical and physical properties to their bulk counterparts due to the massive surface area to volume ratio
• E.g. gold is red as a nanoparticle

Manufacturing Nano-particles

• Nanoparticles are manufactured either from top down or bottom up:
• Top down is where larger particles are broken down into nanoparticles
• Bottom up is where single atoms and molecules are assembled into larger nano-structures

Quantum Dots

• Nanoparticles of dimension 2-10 nm made from compounds
• Bulk material is white, and visible while protecting from ultraviolet radiation (UVR)
• Absorbs all incident UV, but reflects all colours in the visible spectrum, therefore appears as white
• Smaller, therefore exhibits quantum properties
  • It is smaller than the wavelength of light thus light passes through it, and it does not reflect light - thus it is transparent
• However it still has UV deflecting capability due to quantum effects
• Sunscreen
  • Made from compounds such as $Ti{O}_2$ and $ZnO$
  • Quantum dots absorb all incident UVR due to quantum effects
  • Keeps us safe from UVR from sun
  • Appears white as it reflects all colours in the visible spectrum

Carbon Nanotubes (CNT)

• Covalent structure of formation $C_x$
• Cylindrical molecule consisting of rolled-up sheets of single-layer carbon atoms (graphene)
• Can be simple or multi-walled
• Tubular
• Mechanical tensile strength of up to 400 times that of steel
• Light-weight: density is $\frac{1}{6}$ of steel
• Good at conducting heat/electricity
• Hollow
• Resistant to corrosion
• Chemically stable
• Less than 100 nm in diameter
  • Can have a diameter of 1-2 nm

CNT Computers

• Carbon nanotubes are electrically conductive
• Stronger signals can be sent using far smaller transistors(semi-conductors) than is possible with silicon.
• CNT computers use about a tenth as much power as comparable silicon systems
• More sustainable

Silver Nano-particles

• Nano-particles composed of silver
• 1 - 100 nm
• High conductivity,
• Powerful signal capacity
• Biocompatibility
• Anti-bacterial properties
  • Also effective against various fungi, viruses, and algae

Nano-composites

• Nano-particles made of 2 or more different types of mater with significantly different properties
• Final nano-material has properties different(or sometimes a combination) to the individual components of the composite
• They are unique, as they exhibit properties that are different to (or sometimes a combination of) the individual components - they develop these due to quantum effects
• For a composite to be considered a nano-composite, at least 1 composite must be nano-scaled

Dendrimers:

• Nano-sized, radially symmetrical molecules
• Good materials for the development of nanotechnologies because of their well-defined structure and properties

Imaging Nanoparticles:

• Electron is aimed and fired at a surface, and rebounds back to a sensor
• Time is calculated, and thus distance, as we know the velocity

TEM - Transmission Electron Microscopy

• Uses an electron beam to image a nanoparticle sample using transmitted electrons
• TEM can reveal details at the atomic scale by magnifying nanometre structures up to 50 million times
• Doesn’t rely on light in the visible spectrum; produces higher resolution than light based imaging
• Most desired method for imaging

SEM - Scanning Electron Microscopy

• Uses electron beams to magnify infinitesimal features
• Electrons are deflected off object and then detected

STEM - Scanning Transmission Electron Microscopy

• Atomic scale resolution, better than SEM
• Can cause sample damage

AFM - Atomic-force Microscopy

• 3D characterisation of nanoparticles with sub-nanometre resolution
• Can directly create images of nanoparticles with dimensions between 0.5 to 50+ nano-metres

Safety of Nanoparticles:

• Nanoparticles can easily penetrate cell membranes and tissue
  • They could cause biochemical damage or even cancer
  • They can interact with biological systems
• There are many potential dangers as nanoparticles can be highly reactive or catalytic due to their large surface area to volume ratio
• People need to be careful when dealing with nanoparticles
  • They must wear correct equipment e.g. gloves
• The long term effects of nanoparticles in sunscreens is currently unknown