The obtained time domain THz pulses after transmission through the sample (Figure , a) solid lines) show a significant difference in amplitude and a phase shift when compared to the pulse that did not pass the sample (dashed lines). The observed shifts contain information about the charge carriers inside the nano-crystals. Since the THz pulse is of picosecond duration, it can be translated to the conductivity on the nanoscale by a fast Fourier transform as explained in detail in the SI.