Highly Stable Colloidal Lithium Niobate Nanocrystals with Strong Violet and Blue Emission

High-quality LiNbO₃ colloidal nanocrystals were synthesized by the sol-gel technique. Morphological, structural, and optical spectroscopy methods were used to characterize LiNbO₃ colloidal nanocrystals. To investigate the optical properties, UV-visible absorption spectroscopy was used, which showed that the absorption peak was around 250 nm. Zeta potential was used to determine the stability of colloidal LN nanoparticles. Selected area electron diffraction patterns and X-ray diffraction patterns indicated that the dried LiNbO₃ sol formed in the rhombohedral crystal system. Field-emission scanning electron microscopy and transmission electron microscopy were used to study the morphological properties, which showed that the average diameter of colloidal nanocrystals is about 23 nm. Finally, two emission peaks were observed at 420 (violet) and 485 nm (blue) wavelengths in the photoluminescence (PL) spectrum. Also, using the PL measurements, the quantum yield for colloidal LiNbO₃ was calculated to be 87% at an excitation wavelength of 250 nm. Experimental results have shown that highly stable LiNbO₃ colloidal nanocrystals were synthesized that have enough potential for quantum photonics applications such as waveguides. The highly stable colloidal form of LiNbO₃ nanocrystals has not been synthesized before, and the mentioned optical properties are reported for the first time.