Abstract
The present study reports the production of upconverter nanostructures composed by a yttrium oxide host matrix co-doped with ytterbium and europium, i.e., Y2O3:Yb3+/Eu3+. These nanostructures were formed through the dissociation of yttrium, ytterbium and europium oxides using acetic, hydrochloric and nitric acids, followed by a fast hydrothermal method assisted by microwave irradiation and subsequent calcination process. Structural characterization has been carried out by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM) both coupled with energy dispersive X-ray spectroscopy (EDS). The acid used for dissociation of the primary oxides played a crucial role on the morphology of the nanostructures. The acetic-based nanostructures resulted in nanosheets in the micrometer range, with thickness of around 50 nm, while hydrochloric and nitric resulted in sphere-shaped nanostructures. The produced nanostructures revealed a homogeneous distribution of the doping elements. The thermal behaviour of the materials has been investigated with in situ X-Ray diffraction and differential scanning calorimetry (DSC) experiments. Moreover, the optical band gaps of all materials were determined from diffuse reflectance spectroscopy, and their photoluminescence behaviour has been accessed showing significant differences depending on the acid used, which can directly influence their upconversion performance.
Highlights
Upconverter materials are characterized by having the ability to emit photons with higher energy than the photons that were absorbed [1]
No other weight loss steps or peaks are observed, indicating that the complete conversion of the yttrium oxycarbonate into Y2O3 has occurred. These results are in agreement to what is described in literature [45,48] and to what was observed on in situ X-ray diffraction (XRD) results (Figure 3)
Microwave syntheses revealed itself to be an efficient way for successfully doping the Y2O3 host matrix after dissociating the primary oxides with different acids
Summary
Upconverter materials are characterized by having the ability to emit photons with higher energy than the photons that were absorbed [1]. Medium Weak Weak Weak n.a. In the past few years, these rare earth oxides have attracted an increasing attention due to their possible use in several applications such as luminescence devices [7,8], color displays [9,10], optical detectors [11,12], telecommunications [5], upconverter lasers and photonics [13,14,15], catalysis [16], biomedicine [17,18] and solar cells [1,19,20], mainly due to their chemical, electronic, and optical properties resulting from the 4f electronic shells [21]. The obtained nanostructures were fully characterized by X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Ultra Violet- Visible – Near Infrared (UV-VIS-NIR) spectroscopy, and photoluminescence
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