Synthesis Flashcards
There are 2 general approaches to synthesize nanomaterials: bottom-up and top-down. Describe them and list the advantages and disadvantages of each approach.
Top-down: Have bulk material and break it down through milling or grinding.
(+) fast way to produce a lot of material
(-) require a lot of force, poor control over the particles produced. Risk for contamination
Must be material available
require good quality of the starting material
Bottom-up: Build from smaller pieces.
(+) better control, homogenous chemical composition, less defects. Can synthesise non-existing material, high quality
(-) expensive, r, not easy to scale up
Briefly describe milling
Milling: grinding material. Liquid in the mill – disperse the particles as much as possible. Balls of high abrasion-resistant materials
Briefly describe thermolysis
Thermolysis: starting material as liquid/gas/solid is vaporized by energy source, reactive species formed. Cooled down, where nanoparticles have formed through aggregation. Depending on the amount of energy and cooling shape and size can be tuned.
Briefly describe sol-gel
Sol-gel:
Starting material in gel/solution
Form it into more jelly material, liquid removed
Calcinate the material
How are gold nanoparticle typically produced? Describe the role of the different reagents used in the synthesis protocol.
Typically done by reduction of gold salts. There is a reduction agent – as in lab: citrate
Stabilization agents are added to prevent aggregation.
Conditions and additives can be used to tune size and shape. GoldNP grow until all citrate is reduced –> tune size. Ligands can be linked to stabilizing agent
How is mesoporous silica produced? Which parameters are important to be controlled during the synthesis of mesoporous silica and why?
Condensation of silica species to a template consisting of surfactants. Surfactants from micelles in the reaction solution, micelles acts as a template for the silica
Mix solvent + surfactant/template + silica precurosor
Remove template by heating
A number of factors are important to be controlled during synthesis
- Source of silica
- Type of surfactant
- pH and composition of the reaction mixture
- Temperature
- Time
- Calcination conditions
How are dendrimers synthesized?
What are the advantages and disadvantages of such methods?
Divergent or convergent synthesis
Divergent: assembled from a multifunctional core, extended outwards by a serious of reaction. Inside –> out
(+) can make larger constructs
(-) impurities can impact function and symmetry. Difficult to purify
Convergent: build from small molecules that end up at the surface of the sphere. Reactions proceed inwards and are eventually attached to the core
Outside –> in
(+) easier to remove impurities, more monodisperse, control
(-) limited size, crowding steric effect
What are the methods used for the synthesis of carbon nanotubes? Which techniques are used to purify carbon nanotubes?
Vaporized graphite in both cases –> cool down –> aggregates
Electric arc – electricity -> vaporization
laser ablation - laser ->vaporization
chemical vapor deposition –> carbon containing gas, catalyst -> energy -> reactive carbon -> deposited in substrate coated with catalyst
Purification
Density gradient ultracentrifugation
Filtration
Chromatography
Oxidation: oxidize impurities and defect nanotubes
Acid treatment: remove metal catalyst
Annealing
Mention the characteristics of dendrimers and their potential applications in medicine.
Tree like structures. Central core with branches
Dense surface and hollow core
Applications:
- Targeted drug-delivery
- Targeted radiosensitizer delivery
- Macromolecular carriers
- Surface engineering
- Biomimetic materials
What are the challenges in the production of fullerenes?
Time consuming, low yield, expensive, difficult purification (soot, sizes)
