We propose to continue the investigation of the organic surfactant shell's adsorption on colloidally stable semiconductor nanocrystals in hexane-d14 solution, the softness of this organic layer and its influence on the vibrational spectrum of the nanocrystals. PbS nanocrystals coated with oleic acid as the surfactant are technologically relevant for quantum dot-based solar cells and subject to long-term investigations by several research groups including our collaboration, utilizing electron microscopy, X-ray scattering, optical/NIR-spectroscopy, Raman spectroscopy, etc. We propose a combined approach using time-of-flight (TOF) and backscattering (NBS) spectroscopy on the same PbS nanocrystal solution to elucidate the dependence of the vibrational spectrum (using TOF) on the volume and dynamics of the oleic acid shell already measured by SANS and NBS in proposal 9-12-498, respectively. This experiment becomes feasible due to the previous complimentary characterization as well as the extremely high flux available at ILL, which is of paramount importance considering the relatively low volume fraction of the surfactant shell (approx. 1 monolayer on PbS with a diameter of 50 (±3) Å