Abstract Lanthanide-doped upconversion nanoparticles enable anti-Stokes emission via nonlinear processes, where low-energy excitation photons in the near-infrared window can be upconverted into high-energy emission ones in the visible or ultraviolet regions. The past decade has seen great success in the high-quality synthesis of upconversion nanoparticles with controlled structure, crystalline phase, size, and shape. The unique capacity of upconversion nanocrystals to undertake near-infrared excitation, amalgamated with their excellent luminescent characteristics, such as massive anti-Stokes spectral shift, sharp emission band, multicolor emission, and long luminescence lifetime, makes these nanomaterials prime candidates for a plethora of applications. Herein, we review the field of upconversion nanoparticles from the perspectives of fundamental luminescence mechanisms, new synthetic routes, and current practical approaches to tuning emission color and enhancing upconversion efficiency. In particular, we highlight the recent advances in utilizing upconversion nanocrystals for bioimaging, therapy, biosensing, neuroscience, super-resolution imaging, photoswitching, and lasing applications. We also discuss the key challenges and issues that are critical for the further implementation of upconversion nanoparticles in diverse settings.

中文翻译：

---

上转换纳米晶体的最新进展：为新兴应用扩展万花筒工具箱

摘要 掺杂镧系元素的上转换纳米粒子可以通过非线性过程实现反斯托克斯发射，其中近红外窗口中的低能激发光子可以上转换为可见光或紫外区的高能发射光子。在过去十年中，在高质量合成具有可控结构、晶相、尺寸和形状的上转换纳米粒子方面取得了巨大成功。上转换纳米晶体具有独特的近红外激发能力，再加上其优异的发光特性，如大规模反斯托克斯光谱偏移、尖锐的发射带、多色发射和长的发光寿命，使这些纳米材料成为大量的主要候选材料。应用程序。在此处，我们从基本发光机制、新合成路线和当前调节发射颜色和提高上转换效率的实用方法的角度回顾了上转换纳米粒子领域。我们特别强调了利用上转换纳米晶体进行生物成像、治疗、生物传感、神经科学、超分辨率成像、光开关和激光应用的最新进展。我们还讨论了对在不同环境中进一步实施上转换纳米粒子至关重要的关键挑战和问题。神经科学、超分辨率成像、光开关和激光应用。我们还讨论了对在不同环境中进一步实施上转换纳米粒子至关重要的关键挑战和问题。神经科学、超分辨率成像、光开关和激光应用。我们还讨论了对在不同环境中进一步实施上转换纳米粒子至关重要的关键挑战和问题。