Layered NbOCl2 kinetic degradation mechanism and improved second-order nonlinear optical responses

Abstract

NbOCl2 exhibits exceptional nonlinear optical response, particularly for second harmonic generation (SHG). However, the environmental degradation mechanism of NbOCl2 remains incompletely understood, posing challenges to device stability and optimization. This work demonstrates the kinetic degradation mechanism of 2D layered NbOCl2 and proposes a strategy to improve the stability of nano-sized materials. It is primarily driven by the preferential replacement of Cl– ions in NbOCl2 with OH– ions, which is regulated by storage temperature and H+ ions in the solution. Notably, the SHG response can be tuned effectively by altering the excitation power, degradation time, and irradiation wavelength. Additionally, the significant SHG of the NbOCl2 nanosheets is remarkably stable when protected by poly methyl methacrylate. These findings offer novel insights into kinetic degradation mechanisms and strategies to improve the stability of NbOCl2