Nanomaterials

Question 1

What are Nanomaterials Synthesis approaches? Compare.

Answer 1

1) top-down (physical methods) : size reduction using mechanical force. bulk -> powder -> nanomaterials. preferred for industrial scale up. require expensive equipment and intensive energy without providing control over particle growth)
2) bottom up (physical & chemical methods) depends on assembly. atoms & molecules -> clsuters - > nanomaterials. fewer defects and more homogenous chemical composition

Question 2

What is the importance of nanomaterials?

Answer 2

1) High surface area: volume ratio
2) unique chemical and physical properties
3) exhibit surface plasmon resonance
4) high mechanical strength
5) surface modification and targeting
6) high catalytic activity

Question 3

3. Classification of nanomaterials

Answer 3

based on Dimensionality
1) 0D nanospheres & clusters: all in nanoscale (quantum dots, fullernes, AuNP, metalNP)
2) 1D Nanotubes wires & rods: 2 in nanoscale, 1 in microscale (metal nanorods, ceramic crystals, carbon nanotubes, metallic nanotubes, gold nanowires, polymers and nanofibers, self assembled structures
3) 2D thin films, plates & Layered structures: 1d in nansclae, 2d in microscale: carbon coated nanoplatesm graphene sheets, layered nanomaterials
4) 3D bulk NM & polycrystals: multiphase
nanocomposites where at least one phase
has a nanoscale external dimension (Liposomes, polycrystilline, dendrimer)

Question 4

What roles can nanomaterials take in optical biosensing?

Answer 4

1) Fluorescence Signal Generator
2) Fluorescence Quencher
3) Signal amplification probe (dye)

Question 5

What is Upconversion nanoparticles (UCNPs)

Answer 5

UCNPs are a unique class of optical nanomaterials doped with lanthanide ions, which can up-convert two or more lower-energy photons into one high-energy photon (shorter wavelength)

Question 6

How UCNPs work?

Answer 6

sequential absorption of pump photons:
1) a first absorption process excites the UCNP to a metastable excited level
2) further absorption may take place raising the ion to a higher excited state
3) As it relaxes to the ground state, UCNP releases a higher energy shorter wavelength photon