Question 7

Question 1

q7a)

You want to synthesize hollow cubes as shown in the figure by a template approach. The gray spheres correspond to titania nanoparticles, while the black lines represent reduced graphene oxide (rGO). In a next step, you want to micropattern these hollow cubes on a substrate into triangular arrangements. The sketch is not in scale.

Propose a possible synthesis route to such hollow cubes. How would you assemble the two building blocks titania and rGO in such a structure?

Answer 1

Use layer-by-layer assembly and make use of the opposite charges:
- first start with the negative charged template (cube)
- put the template in the first solution with the titania nanoparticles in it (positive charged)
* - they attach to the template bc of electrostatic attraction
* - acidic solvent (for the positive charge of Trizma)
- wash and put cube in next solution with the negative charged rGO
- wash and put again in the solution with the titania
- heat to remove substrate

In general: control thickness by time you let the template in the solution, always wash afterwards

Question 2

q7b)

How would you synthesize the TiO2 nanoparticles and the reduced graphene oxide nanosheets?

Explain briefly

Answer 2

TiO2 nanoparticles:
- non-aqeous sol-gel: TiCl4 with benzyl alcohol and stabilized with Trizma (only hydrolysis and condensation) → positive charged

Reduced graphene oxide: top-down method
- oxidation of graphite to synthesize graphite oxide (Hummers method)
- sonificate graphite oxide → exfoliation of graphene oxide (GO)
- reduction to reduced graphene oxide (with NaBH4)

Question 3

q7c)

c) What template would you use for the synthesis of the hollow cubes and how would you synthesize it?

Describe briefly

Answer 3

Continuous flow lithography of polystyrene particles (polymerize with UV light → can controle shape of beam & height with tube height). Add sulfonate (SO4 2-) functional groups to make the negative charge.

Question 4

q7d)

Finally, you want to arrange these hollow cubes into triangular, micron sized patterns on a substrate.
How would you do that?

Answer 4

• Make a cube template in the triangular shape → attach directly there the titania and rGO → but only 5 sides covered.
• Capillarity-assisted particle assembly: with triangles patterned surface → have cubes with solvent in a meniscus movement over surface -> particles trapped in patterns (particles brought together by applying internal driving force (not self-assembly)