Solution-Processed Nanostructured Hybrid Materials Based on Graphene Oxide Flakes Decorated with Ligand-Exchanged PbS QDs: Synthesis, Characterization and Optoelectronic Properties

Nanostructured hybrid materials based on the combination of semiconductor QDs and GO are promising candidates for different optoelectronic and catalytic applications and being able to produce such hybrid materials in solution will expand their possible range of applications. In the current work, capping ligand-exchange procedures have been developed to replace the lead oleate normally found on the surface of PbS QDs synthesized by the popular hot-injection method. After the capping ligand-exchange process, the QDs are water soluble, which makes them soluble in most GO solutions. Solution-processed nanostructured hybrid materials based on GO flakes decorated with ligand-exchanged (EDT, TBAI and L-Cysteine) PbS QDs were synthesized by combining PbS QDs and GO solutions. Afterward, the resulting hybrid materials were thoroughly characterized by means of FTIR, XPS, Raman, UV-Vis-NIR and photoluminescence spectroscopy, as well as SEM and TEM techniques. The results indicate a clear surface chemistry variation in the capping ligand-exchanged PbS QDs, showing the presence of the exchanged ligand molecules. Thin films from the solution-processed nanostructured hybrid materials were deposited by the spin coating technique, and their optoelectronic properties were studied. Depending on the capping ligand molecule, the photoresponse and resistance of the thin films varied; the sample with the EDT ligand exchange showed the highest photoresponse and the lowest resistance. This surface chemistry had a direct effect on the charge carrier transfer and transport behavior of the nanostructured hybrid materials synthesized. These results show a novel and accessible route for synthesizing solution-processed and affordable nanostructured hybrid materials based on semiconductor QDs and GO. Additionally, the importance of the surface chemistry displayed by the PbS QDs and GO was clearly seen in determining the final optoelectronic properties displayed by their hybrid materials.