How about "SiO2 nanoparticle and its optical application"?

I have a lecture of 3h, and I performed the Stober method to prepare SiO2 nanoparticles.

In the 1st hour of lecture, I demonstrated the reaction.

"These clear solutions are mixed....See! the solution becomes milky white."

Then, I explained the Stober method and the particle formation process.

http://en.wikipedia.org/wiki/St%C3%B6ber_process

The reaction will be observed within several minutes, and almost accomplished within 1 hour.

In the 2nd hour, I spread the dispersion of SiO2 nanoparticle onto a glass plate, and the plate was slowly dried.

In the 3rd hour, I got the dried film of SiO2 nanoparticle with beautiful opal color.

I explained the self-assembly of nanoparticles and the application of photonic crystal.

Next week, the SiO2 nanoparticles precipitated to form a opal layer in the bottle.

You just need TEOS, ethanol, water, and ammonia solution.

The conc ammonia solution stinks, but you can prepare the diluted solution before the class, it was not so bad smell.

You need to practice several times to optimize the reaction conditions, but not so difficult.

======================================

If you don't have 3 hours a day, silver or gold nanoparticles can be prepared.

A reaction of AgNO3 and NaBH4 with citric acid can immediately provide a yellow solution. When you use NaAuCl4, you will get a orange ~ wine-red solution.

http://en.wikipedia.org/wiki/Colloidal_gold

Silver and gold can change their color when they become the nanoparticles.

It is a quantum effect, "Plasmon". I demonstrated the synthesis and explained the theory.

http://en.wikipedia.org/wiki/Plasmon

I also explained a morphological control of gold nanoparticles by my method.

http://www.sciencedirect.com/science/article/pii/S0927775713005591

The gold nanoparticle synthesis with citrate by heating (Turkevich method) is a standard method, but it need the boiling condition. So, I am not sure if it is suitable for your case. You need a burner or electrical heating system. My lecture is in the ordinary class room, so, I could not use the fire and used the reaction of "just mixing".

Yu and Peng (see attached paper) is a pretty common method. You would need to prepare the Se solution ahead of time for the students in a glove box (the phosphines react vigorously if they come in contact with paper towels and air, so you need to advise the students to be careful with the syringe and always keep it in a fume hood). The oleic acid precursor is nice because it is much cheaper that the phosphonic acid which was more commonly used, as well the oleic acid eliminates the need for phosphine oxides and alkyl amines as solvents, which makes the synthesis more environmentally friendly.

The oleic acid synthesis will yield high quality CdSe nanocrystals, and the students will be able to observe the nanocrystal solution change color as the crystals grow, giving them a nice visual for a particle in a box. If you want to eliminate the need for phosphines, the paper also describes the synthesis of CdS which is phosphine free, and thus eliminates the need to have a glove box, though you will still need to maintain an inert atmosphere since you will heating the solvents above their flash point.

Thank you for the suggestion. However, my institution has rather meager resources. Se would be too expensive. We do not have a glove box. Working with something that reacts 'vigorously' with paper towels and air is something that basic chemistry students should not be performing on their own. And we do not have the means to perform experiments in an inert atmosphere.

I like the observable transitions you mentioned. Seeing changes with the naked eye is important for engaging students attention. We do have access to an IR spec, so we will be confirming composition with it.

Although not always considered as nanoparticles, undergrad students from a B. Sc. in Technology enjoyed a lot a 3-session lesson to prepare liposomes. They prepare them from egg yolk-phospholipids.

In a fume hood:

Session 1: (1) Mix egg yolk (0.5 gr) + 1.5 ml water + 4 ml metanol + 2 ml dichloromethane in a glass tube. (2) Incubate 30 min, (3) Add 2 ml water and vortex, wait to phase separation and, (4) Recover the organic phase and evaporate it under nitrogen. This is the total lipid extract. Keep it at -20oC (or frozen, at least).

Session 2: (1) Dissolve the lipid extract in dichloromethane. (2) Equilibrate a Sep-Pak silica gel column with dichloromethane, (3) Elute with 3 volumes of dichloromethane, followed by 3 volumes acetone, then with 3 volumes methanol, (4) Analyze the fractions by TLC to visualize phospholipids with molybdenum blue spray (to be sprayed by you since it is dissolved in acid). (5) Evaporate to dryness under nitrogen and keep at -20oC. NOTE: If you are not able to evaporate under nitrogen, you may take advantage of that since students will be able to notice ruptured phospholipids as well.

Session 3: (1) Add 3 ml water at 45oC to the phospholipid-containing methanol fraction (previously evaporated), (2) vortex, and sonicate for 10 min (alternate 1 min sonication-1 min glass bath cycles). Multilamellar vesicles are formed after vortexing, while sonication gives a clear suspension mostly composed of unilamellar vesicles, (3) Vesicles can be analyzed in a dynamic light scattering apparatus, or Zetasizer to determine the size distribution of liposomes. (4) Alternatively, the unilamellar vesicles, invisible if nanometric, may be analyzed by IR after evaporated in a KCl device.

How about "SiO2 nanoparticle and its optical application"?

I have a lecture of 3h, and I performed the Stober method to prepare SiO2 nanoparticles.

In the 1st hour of lecture, I demonstrated the reaction.

"These clear solutions are mixed....See! the solution becomes milky white."

Then, I explained the Stober method and the particle formation process.

http://en.wikipedia.org/wiki/St%C3%B6ber_process

The reaction will be observed within several minutes, and almost accomplished within 1 hour.

In the 2nd hour, I spread the dispersion of SiO2 nanoparticle onto a glass plate, and the plate was slowly dried.

In the 3rd hour, I got the dried film of SiO2 nanoparticle with beautiful opal color.

I explained the self-assembly of nanoparticles and the application of photonic crystal.

Next week, the SiO2 nanoparticles precipitated to form a opal layer in the bottle.

You just need TEOS, ethanol, water, and ammonia solution.

The conc ammonia solution stinks, but you can prepare the diluted solution before the class, it was not so bad smell.

You need to practice several times to optimize the reaction conditions, but not so difficult.

======================================

If you don't have 3 hours a day, silver or gold nanoparticles can be prepared.

A reaction of AgNO3 and NaBH4 with citric acid can immediately provide a yellow solution. When you use NaAuCl4, you will get a orange ~ wine-red solution.

http://en.wikipedia.org/wiki/Colloidal_gold

Silver and gold can change their color when they become the nanoparticles.

It is a quantum effect, "Plasmon". I demonstrated the synthesis and explained the theory.

http://en.wikipedia.org/wiki/Plasmon

I also explained a morphological control of gold nanoparticles by my method.

http://www.sciencedirect.com/science/article/pii/S0927775713005591

The gold nanoparticle synthesis with citrate by heating (Turkevich method) is a standard method, but it need the boiling condition. So, I am not sure if it is suitable for your case. You need a burner or electrical heating system. My lecture is in the ordinary class room, so, I could not use the fire and used the reaction of "just mixing".

I recommend the silver nanoparticles synthesis using sodium citrate. Maybe the silver nitrate is not that cheap but of course it can be find in general chemistry laboratory. You just need hotplate stirrer, magnetic bar, and glass bottle for reaction (of course glove for handling hot bottle)

It also a great way to show plasmon effect to the student by observe color change during reaction proceed.

Cobalt-iron oxide nano particles can be produced from their chloride solutions. The method is relatively simple and controllable.

You can go for synthesis of ZnO by Chemical route using plant extract

https://www.scientificamerican.com/article/bring-science-home-colloids/