Upconversion nanoparticles exhibit ordinary emission brightness for the existence of non-radiative transition induced by the surface defects, which fundamentally limits their promising applications. Here, a reconstruction process to rule out the amorphous layer and defects related to the surface of the as-synthesized particles is achieved with the use of 980-nm continuous laser irradiation. More importantly, the uniform morphology and monodispersibility of these nanoparticles are well preserved. Local heat induced via photothermal conversion of laser irradiation with the association with non-harmonic phonon coupling contributes to a tremendous improvement on the integral upconversion luminescence intensity. The upconversion intensity of Er³⁺ ions in sub–10-nm Ba₂LaF₇ nanoparticles enhances by more than 313-fold in the red emission, and subsequently, a bright luminescence originated from an individual particle could be observed under a multiphoton laser scanning luminescence microscopy. Our results suggest that this strategy could be extended to GdF₃, KLu₂F₇, and BaGdF₅ systems, which exhibit drastic enhancement of emission intensity unambiguously. The laser-induced surface reconstruction in this work is demonstrated to provide a direct and facile approach to enhance the upconversion intensity, which could offer the possibility for achieving high-resolution imaging.

由于存在由表面缺陷引起的非辐射跃迁，上转换纳米粒子表现出普通的发射亮度，从根本上限制了它们的应用前景。在此，通过使用980nm连续激光照射，实现了排除非晶质层和与合成后的粒子的表面有关的缺陷的重构处理。更重要的是，这些纳米颗粒的均匀形态和单分散性得到了很好的保留。通过激光辐照的光热转换以及与非谐波声子耦合相关的局部热有助于整体上转换发光强度的极大提高。低于10 nm的Ba ₂ LaF ₇中Er ³⁺离子的上转换强度纳米粒子的红色发射增强了313倍以上，随后，在多光子激光扫描发光显微镜下可以观察到源自单个粒子的明亮发光。我们的结果表明，该策略可以扩展到GdF ₃，KLu ₂ F ₇和BaGdF ₅系统，它们显示出明显增强的发射强度。这项工作中的激光诱导表面重建被证明可以提供一种直接而简便的方法来增强上转换强度，这可以为实现高分辨率成像提供可能性。