Fluorescence properties of DES borne nanometric ZnO: temperature and structure effects

In this contribution, we describe the fluorescence properties of high purity nanometrical ZnO synthesized by precipitation in type-IV zinc nitrate-urea Deep Eutectic Solvent, a system inherently endowed with nanohomogeneities in its internal structure1 , that can be easily prepared by mixing the solid components with only little heating and limited workout procedures. The observed photo luminescence (PL) is remarkably brilliant and detailed investigations pointed out that the emitted radiation has quantum yield values that decrease when temperature is increased across a broad range, being very high at low temperature (77 K) but still appreciable up to 373 K. Such behaviour is perfectly reversible upon cooling and can be profited to assess external temperature with quite good confidence2 . In order to gain further insight on such response property, a series of Raman studies was performed, whose vibrational patterns were assigned according to the crystal structure revealed by XRD experiments. Additionally, the dependence on the system morphology was investigated with FE-SEM microscopy, that depicts different nanoscopical structural arrangements, unveiling the presence of nano lamellar moieties embedded into larger mesoporous domains