1. Could you explain the significance of your article to the non-specialist? 

Cadmium chalcogenide nanoparticles are well known for their photoluminescent properties. Their electronic structures can be tailored to give different colours by controlling the particles' size and architecture. Yet the complete characterization of the composition and structure of nanoparticles is notoriously difficult, and it is necessary to use numerous techniques which provide different pieces of information to build up a consistent picture. We have used solid state NMR to provide unique information which, in conjunction with photoluminescence spectra and powder X-ray diffraction, gives insight into atomic and nano-scale detail in CdSe/CdTe nanoparticles synthesised in tri-octyl-phosphine, both for the pure materials but more significantly and for the first time for particles composed of alloys and with layered structures. Furthermore, 13C NMR revealed the surprising feature that the organo-phosphorus coating ligands actively hop around the surface of the particle. 

2. What has motivated you to conduct this work? 

The primary interest in these materials was to explore their production and stability for potential use as photoluminescent markers in biological applications. However, the main motivation behind the work presented in this paper was to see what new and unique information solid state NMR could provide in the characterization of complex nanoparticles: Could we see size effects in the NMR of nuclei in nanoparticles? Could we distinguish homogeneous alloys from mixtures of nanoparticles of the two components? Could we observe the different components of deliberately layered nanoparticles and say something about the compositions of the layers?  

3. Where do you this work developing in the feature? 

Apart from applications to similar layered structures in other Cd materials (for instance we have immediate plans to look at CdS/ZnS nanoparticles) there are many possibilities for solid state NMR studies of other nanoparticle materials, e.g. 115In or 31P in InP nanoparticles or various metal nuclei in metal nanoparticles. 

4. Are their any particular challenges facing future research in this area? 

There are challenges for NMR in the study of nanoparticles containing quadrupolar nuclei where the distribution of environments inherent in such materials will give rise to distributions of quadrupolar broadening, such that perhaps only the most symmetrical environments will be detected. Studies at high field could circumvent or reduce this effect.