Label-free thermometry is a pivotal tool for many disciplines. However, most current approaches are only suitable for planar heat sources in steady state, thereby restricting the range of systems that can be reliably studied. Here, we introduce pump probe–based optical diffraction tomography (ODT) as a method to map temperature precisely and accurately in three dimensions (3D) at the single-particle level. To do so, we first systematically characterize the thermal landscape in a model system consisting of gold nanorods in a microchamber and then benchmark the results against simulations and quantitative phase imaging thermometry. We then apply ODT thermometry to resolve thermal landscapes inaccessible to other label-free approaches in the form of nonplanar heat sources embedded in complex environments and freely diffusing gold nanorods in a microchamber. Last, we foresee that our approach will find many applications where routine thermal characterization of heterogeneous nanoparticles samples in 3D or in non–steady state is required.

中文翻译：

---

光学衍射断层扫描非稳态测温

无标签测温是许多学科的关键工具。然而，大多数当前方法仅适用于稳态的平面热源，从而限制了可以可靠研究的系统范围。在这里，我们引入基于泵浦探针的光学衍射断层扫描（ODT）作为一种在单粒子水平上精确地绘制三维（3D）温度图的方法。为此，我们首先系统地表征由微室中的金纳米棒组成的模型系统中的热景观，然后根据模拟和定量相成像测温法对结果进行基准测试。然后，我们应用ODT测温法来解决其他无标记方法无法获得的热景观，这些热景观以嵌入复杂环境中的非平面热源和在微室中自由扩散的金纳米棒的形式出现。最后，我们预计我们的方法将找到许多需要对 3D 或非稳态异质纳米颗粒样品进行常规热表征的应用。