Figure 3. UV-vis absorption spectra of few-layer Bi₂Se₃.

(a) UV-vis absorption spectra of as-synthesized bulk and few-layer Bi₂Se₃ suspension. (b) UV-vis absorption spectra of few-layer Bi₂Se₃ suspension prepared with different sonication times in NMP. (c) UV-vis absorption spectra of few-layer Bi₂Se₃ suspension prepared with differrent ultrasonic times in CS-HAc. The upper part of resulting suspension of each sample after sonication was collected, and then centrifuged for 30 min at 1000 rpm to receive the supernatant as the measurement solution.