Surfactant-imposed interference in the optical characterization of GaP nanocrystals

We report on the complications in optical characterization of GaP nanoparticles grown by colloidal chemistry. It is demonstrated that upon exposure to relatively mild heating conditions, the surfactants utilized to arrest growth and/or agglomerization lead to thermal decomposition products, which exhibit optical properties similar to those observed for nanocrystals with broad size distributions. The origin of this photoluminescence is still unknown; however, photoluminescence measurements of surfactants of different purities indicate that the impurities may be responsible for the emission. The results of this study demonstrate the potential complications associated with studying the optical properties of GaP nanocrystals prepared in the presence of commonly utilized surfactants. They suggest that more reliable assignment of the spectral features of nanocrystals can be afforded by a more detailed understanding of the optical properties associated with the surfactants and or their thermal decomposition products.