Effect of Cd-phosphonate complex on the self-assembly structure of colloidal nanorods

A simple approach for finely ordered self-assembling CdSe/CdS nanorods (NRs) on a solid substrate by annealing is introduced. With appropriate Cd-phosphonate complex, NRs align into either parallel arrays or vertical ones depending on the concentration of NRs. The analysis of self-assembled NRs arrays in response to changes in NR concentration showed that the presence of Cd-phosphonate complex does influence the resulting self-assembled nanostructures. The melted Cd-phosphonate complex surrounding NRs during thermal annealing process serves as a media for NRs to self-assemble into an ordered structure. The surface photovoltage (SPV) spectra of vertically aligned NRs shows much stronger response compared to that of parallel aligned ones, which is caused by the direct pathways for charge transport and more effective photo-induced charge transport in the vertically aligned NRs structure. The result suggests that assembly direction and structure of CdSe/CdS NRs can be achieved by selecting the appropriate Cd-phosphonate complex in the synthesis and purification process.