• In the prior arts, patent and non patent literature, there are few processes discussed for production of zinc oxide superstructures which incur high initial equipment cost & requires modifiers, seed layers, or surface directing agents which can compromise the purity of the developed nanostructures.
• Further, the above prior art techniques require variety of organic or inorganic ingredients with time-consuming processing steps, including heat treatment. Hence, there is a requirement of a simple process to address the above issues efficiently.

Present Patent talks about a process for preparation of zinc oxide (ZnO) superstructures by coupling Anodic Aluminum Oxide (AAO) template-assisted synthesis with alkali etching, wherein the process comprises a step of:

• Electro polishing ultrasonicallycleaned aluminum strips.
• Conducting first anodizationfor 1 hour;
• Oxide etching at 60ºC for 1 hour.
• Conducting second anodization for 2 hours.
• Thinning the alumina dielectric barrier layer by sequentially reducing the anodization voltage.
• Etching the sample in 5 wt. % phosphoric acids at 20°C for 45 min to widen the pores.
• Electrochemical deposition of zinc oxide (ZnO) nanowires within the AAO nanochannels.
• Hydroxide etching of ZnO nanowires embedded in the AAO template to obtain ZnO superstructures.

Further, it talks about various features for obtaining ZnO superstructure as shown: 

1. The Electro-polishing step is done at 20V DC, at 10⁰C for 60s including a mixture of perchloric acid & ethanol in 1:4 v/v ratio.
2. First & second anodization steps are conducted in an electrolyte of 0.3M oxalic acid solution at 20°C with a constant voltage of 45V DC.
3. In the hydroxide etching step, the nanowires are etched further for a period of 0 to 60 minutes under concentration range of 0.5 to 2M NaOH at a Temp. between 5 to 50°C.

In this instant, the process of obtaining ZnO superstructure along with outcomes are depicted in the figures.