posters 5th Asia-Pacific NMR Symposium 2013

Solid-State NMR Study of Surface Structure of CdSe Magic-Sized Nanoparticles (#181)

Yasuto Noda 1 , Kazuyuki Takeda 1 , K. Takegoshi 1 , Atsuo Kasuya 2
  1. Kyoto University, Sakyo, Kyoto, Japan
  2. Center for Interdisciplinary Research, Tohoku University, Sendai, Japan

The optoelectronic properties of semiconductor nanoparticles are influenced by their size as well as their surface structure. The former in the case of the diameter over 2 nm can be well characterized by TEM, while the latter is in general unclear. Here, we report on solid-state NMR study on the surface structure of octylamine-protected CdSe magic-sized nanoparticles (MSNPs) which give a typical doublet peak at 450 nm in a solution absorption spectrum. The 77Se and 113Cd surface sites were selectively observed using CP from the protons of the octylamines. The 77Se CP/MAS spectrum showed two sharp peaks at -630 ppm and -501 ppm, which were assigned from the contact-time dependence to the first layer site and the second layer site from the interface, respectively. For the 113Cd, the CP/MAS spectrum showed a single sharp peak at 563 ppm. On the other hand, the static CP spectrum revealed a pair of 113Cd CSA tensors, which happen to have the same isotropic values. The contact time dependence of each 113Cd signal was also measured. Considering several proposed models of the surface structures to satisfy the experimental results, we conclude that the CdSe MSNP forms a plate having the (110) surface of Wurtzite structure as the width-direction facet flattened at the atomic level.