Crystal system: orthorhombic
| Photoluminescence peak position, nm |
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Starting materials: GeI4, HI, H3PO2, C4H9NH2
Product: Bright orange sheetlike crystals
Description: Grow the crystals under slowly-cooled aqueous hydriodic acid solutions. Perform all synthetic steps and crystal manipulations after synthesis in an inert atmosphere to prevent oxidation. Dissolve 0.709 g (1.22 mmol) of GeI4 in 50 mL 3 M HI solution at 80 °C. Raise the temperature of the solution to 98 °C and add 4 mL concentrated (50 wt %) aqueous H3PO2 solution. Allow the reduction of GeI4 to GeI2 to proceed for approximately 4 h, then add a solution of 0.491 g (2.44 mmol) of (C4H9NH2).HI in 3 mL of concentrated (57 wt %) aqueous HI, producing a yellow solution. Allow the resulting solution to sit at 80 °C in flowing argon until approximately 50% of the solution had evaporated and then slowly (2-5 °C/h) cool to -10 °C. Filter out the crystals under flowing argon and dry in argon at 80 °C.
Method: Photoluminescence
Description: Collect the photoluminescence spectra within several hours after the crystals were synthesized, and maintain the samples in an argon-filled cell during measurement to prevent degradation. The photoluminescence spectra were excited by 457.9 nm (2.71 eV) light from an argon ion laser. This light was strongly absorbed by each sample, ensuring that the observed luminescence came from the front side of the samples. The excitation density was below 1 W cm-2. Refer to Page 794 for details.