In situ application of polyelectrolytes in zinc oxide nanorod synthesis: Understanding the effects on the structural and optical characteristics

We report a facile and simple means of synthesizing a macroscopic array of ZnO nanorods with high feature densities using a modified hydrothermal approach that involves the in situ introduction of polyelectrolyte. The ZnO nanorod arrays with heights of 1.5 μm and diameters of 350 nm were consistently reproducible and were bestowed with the advantage of in situ process tunability offered by employing polyethylenimine (PEI) as a surface modifying agent. The fabrication combines benefits from the hydrothermal approach in terms of process simplicity and flexibility and from the use polyelectrolyte that offers a better nanorod surface, quenched defect levels and enhancement of the UV band edge emission. Structural and elemental analysis of the PEI-modified and unmodified nanorods emphasize the fact that the intentional introduction of PEI results in a nanorod with better surface quality as evidenced by photoluminescence (PL) spectra. The tunability of the feature dimensions of the nanorods and an analysis of the bulk and surface (surface defect) responses to the PL point to significant promise of high density orthogonal nanorods in a number of optoelectronic applications. While the defects in the ZnO nanorods can point towards the application of ZnO nanorods in charge trap flash memory devices, highly crystalline, size tunable, high aspect ratio nanorods find applications as building components in solid state lighting.

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► Inexpensive protocol to produce macroscopic high density array of ZnO nanorods.
► A high density of 1.3 × 109 cm−2 over large area is observed for the nanorods.
► Emphasize on dual role of PEI in size tailoring and in enhancing surface quality.
► PL emission map to delineate the role of PEI in ZnO surface quality enhancement.
► Feature-tunable protocol to realize desired morphologies of ZnO nanostructures.