Linear optical studies on Ga9Ge27Se64 nanocolloidal solutions were carried out. Evidence for the existence of defect states in these nanoclusters are obtained from absorption spectra, and its occurrence is emphasized by analyzing the fluorescence and thermal diffusivity studies. An intermediate peak in the band tail of the absorption spectrum is observed at high concentration, and it is interpreted as the absorption due to localized defect states. Fluorescence emission corresponding to this peak confirms the same. The thermal diffusivity studies show that nanocolloidal solutions with less solute concentration have high thermal diffusivity. This indicates the existence of high defect states density which increases with the increase in cluster size, leads to scattering of phonons from the defect centers and in turn results in lowering of thermal diffusivity.