Structural Modelling of Hybrid ZnO-CdSe Nano-Compounds Using X-ray Photoelectron Spectroscopy Depth-Profiling Technique.

Abstract

In the present work, ZnO nanoparticles were synthesized using chemical route method. Composition ratio for Zn:O and various oxidation states were determined using XPS (X-ray photoelectron spectroscopy) technique. The 1 hr calcined ZnO nanoparticles were found to the best due to their monodispersed nature (size ˜20 nm) and high purity. These nanoparticles were then used for synthesizing ZnO-CdSe nano-compounds. These nanocrystals were integrated with CdSe qdots (synthesized using Hot-Injection technique) of varied size (5 nm and 8 nm) via MPA (mercaptopropionic acid) as a linker to develop hybrid nano-compounds for photoactive applications like Quantum Dot sensitized solar cells (QDSSC's) etc. Here, the main objective of the work was to explore the structure of hybrid nano-compounds. XPS-depth-profiling technique was used as an investigation technique for the compositional and structural analyses of ZnO-CdSe nano-compounds. The compositional structure was analyzed layer wise (obtained by etching at different time of sputtering) for the exact position of ZnO and CdSe nanoparticles. On the basis of above study utilizing depth profiling technique of XPS and TEM images, it was found that high quality of hybrid nano-compounds can be synthesized with smaller sized quantum dots, as compared to larger sized quantum dots because of unbounded phosphorus (P) and selenium (Se). Also, it confirms the role of linker that strengthens the binding of CdSe quantum dots on the surface of ZnO thus making it hard to separate the anchored, interstitial CdSe completely which paves the way for the development of stoichiometric, structurally and morphologically-stable ZnO-CdSe nano-compounds.