Eu, Dy, Er, Yb, anhydrous, ≥99.9%), LnCl3.6H2O (Ln = Nd, Eu, Dy, Er, Yb; ≥99.9%), choline chloride
(98%), ethylene glycol (anhydrous, 99.8%), and urea (99.5%) were purchased
from Sigma-Aldrich.
from Alfa Aesar. All anhydrous chemicals were transferred to an Ar
atmosphere glovebox [(O2), (H2O) ≤ 5
ppm] for use and storage. choline chloride and urea were dried in
a vacuum oven (24 h, 80 °C) before being transferred into the
glovebox.