Manipulating the singular red emission in GdOF:Yb/Er nanosheets via defect engineering

Efficient tailoring of red emission in a selectively emitting Yb3+/Er3+ up-conversion (UC) system is of great significance for optical applications. In this study, we adopted a facile and effective method to obtain a pure red emission by defect engineering in GdOF:Yb3+/Er3+ (6/x mol%) nanosheets. It was observed that the defect engineering was realized by NaF etching of the precursors in a low-temperature water bath reaction. As a result, the probability of multi-phonon relaxation processes was increased, resulting in a red to green (R/G) ratio higher than 19 for all samples. The products perfectly inherited the sheet-like morphology of the precursors. Further-more, the effect of calcination temperature on the UC emission selectivity was demonstrated in GdOF:Yb3+/Er3+ nanocrystals. The R/G ratio of the samples obtained at 500 degrees C was increased by about 3-4 times compared with the samples obtained at different calcination temperatures. By combining the results with the outcomes of spectroscopic analyses, we simulated the role of defects in improving the R/G ratio of GdOF:Yb3+/Er3+ samples using a model. The exciting discovery of the ability of defect engineering to modulate UC emission selectivity not only provides a general method to tailor red emission in a Yb3+/Er3+ UC system, but also facilitates multicolor displays, anti-counterfeiting, and tissue bioimaging.