Preparation, characterization, and spectroscopy study on CdSe quantum dots linked to multi-walled carbon nanotubes

Abstract We present spectroscopy study on cadmium selenide (CdSe) quantum dots (QDs) with different particle sizes linked to multi-walled carbon nanotubes (MWCNTs), so-called (CdSe-QDs/MWCNTs), in the ultraviolet and visible frequency range. Drude-Lorentz (DL) model has been used for fitting the absorption spectra for the samples under investigations. Quantitative information about the different excitonic bands and the particle sizes of CdSe-QDs were obtained from the fitting curves and their components. Furthermore, noncontact terahertz time-domain spectroscopy technique was used to compare the optical properties of the MWCNTs and CdSe-QDs/MWCNTs. Using DL model, the optical conductivities have been estimated from the optical parameters obtained from the data extracted from the differential complex terahertz analysis in the frequency range of 0.06–3 THz. The results illustrate that the optical conductivity of MWCNTs is smaller compared to the CdSe-QDs/MWCNTs due to the increased number of free electrons transferred from CdSe QDs and the availability of mobile carriers.