Design of a Low-Temperature Solar Heat Concentrator for the synthesis of ZnO nanostructures

 

Diagram and image of the CPC Solar Collector and SEM image of the synthesized ZnO

It has been widely reported that heat obtained from solar radiation can be applied to the synthesis of nanomaterials. In the case of zinc oxide (ZnO), the nanomaterial of interest in this study, it has previously been synthesized using high-temperature solar heat through Physical Vapor Deposition (PVD) methods.

In this work, a group of researchers from Mexico (CNyN-UNAM, CICESE, and UABC) propose evaluating a new approach for ZnO production through the design of a compound parabolic concentrator (CPC) with a cylindrical (tubular) receiver that generates heat at low temperatures.

The authors placed the precursors, zinc nitrate Zn(NO₃)₂ and sodium hydroxide (NaOH), inside the reactor where ZnO is produced. The reactor is in turn located within the CPC. In this setup, the collector serves both as a heat generator and as a reactor for synthesis.

The synthesis temperatures ranged from 50°C to 70°C. Using solar heat, pure ZnO crystalline clusters were obtained, with sizes ranging from 40.4 nm to 55.7 nm, and a band gap of 3.27 eV, slightly lower than that obtained by other methods at 50°C. The absorbance of the synthesized ZnO was 90%, regardless of the synthesis temperature.

This study confirmed that high-quality ZnO can be feasibly produced using low-temperature solar heat. This constitutes a new "green chemistry" approach and a renewable energy source for nanomaterial synthesis.

For more details, consult: Journal of Nanotechnology