Figure 2.
(a) Schematic representation of the setup for simultaneous acquisition of low-temperature MAS NMR spectra and PL spectra. The orange region represents a quantum dot film on the surface of the MAS rotor, within the rf coil. Blue and red lines represent optical fibers for exciting and collecting PL signals. (b) PL spectra of CdSxSe1-x/ZnS quantum dots applied to the surface of a MAS rotor containing a mixture of KBr powder and uniformly 15N,13C-labeled L-valine powder, obtained in a 9.4 T field with MAS at 6.5 kHz. In this case, the two quantum dots were mixed in an approximate 1:1 molar ratio. Indicated temperatures were determined from 79Br T1 values.