• Freeze-Pump-Thaw: On a Schlenck line, place octadecene in a heavy-walled (critical) single-neck round bottom flask or a sealed Schlenk flask. Freeze it by immersing in liquid nitrogen. Once frozen, open the flask to high vaccum and pump for about 5 minutes. Keep the octadecene in liquid N2. Place solvent back under N2 and let thaw. Repeat 3 times. Remove solution using a needle and syringe into a N2 filled septa vial.
• Purging: So, this is what I do for octadecene. This is really hard on a vacuum pump so use a robust pump (Varian DS Rotary Vane Pump). Place octadecene in a round bottom flask. Heat to 110°C and place under vacuum for about 30 minutes. Refill with N2. Keeping under N2 atmosphere, bubble N2 or Argon into the flask using a long needle. Bubble for about an hour or two.
Store degassed octadecene in a glovebox.
M. Wang, D. Williams, G. Lahti, S. Teshima, D. Dominguez-Aguilar, K. J. Koski, Chemical intercalation of heavy metal, semimetal, and semiconductor atoms into 2D layered chalcogenides. 2D Materials, 5, 045005 (2018)
Procedure:
While it is possible to intercalate germanium using tin chloride, given the favorable redox potentials, germanium (II) bromide disproportionates at high temperatures to germanium metal and GeBr4. Thus, an intercalation reaction can be performed by heating the reactants and host to 150°C. This reaction works with any germanium halide. Buy and use what is cheapest (GeI2, GeCli2, GeBr2).
This reaction must be done in air-free conditions. Follow the setup according to Cr or setup the reaction with a Schlenk line as shown. Germanium halides must also be stored in a glovebox and tend to come in a scored glass capsule.
Octadecene is the solvent used for this reaction. It is possible to buy this anhydrous. Or just degass tech grade (above). Store degassed octadecene in a glovebox.
Prepare two stock solutions: a solution of 5 mL octadecene (stock solution 1) and a solution of 0.01 g GeBr2 in 5 mL degassed octadecene (stock solution 2). Use an air-free setup as according to Fig 3 (or following Cr). Place the 2D material or substrate in the round bottom flask, evacuate, and flush with N2. Under N2, inject the stock solution 1 of octadecene into the round bottom flask and heat to 170°C. Dropwise over the course of 1.5 hours, inject in the stock solution 2 of ~5 mM GeBr2 dissolved in 5 mL of degassed octadecene. Afterwards, remove the substrate with exposure to air and rinse repeatedly with acetone to remove excess octadecene and germanium bromide. Best to just make a bath of warm acetone and drop the substrate into it and wait about 3 minutes. Repeat as desired to intercalate more Ge.
How much can be intercalated into Bi2Se3 nanoribbons:
GeBr3
octadecene
time
~ intercalated in Bi2Se3
0.01 g
Total = 10 mL
1.5 hours
5 atm % ± 3%
Relevant Publications:
Supported by NSF DMR-1658019