Resolving chemical species at the nanoscale is of paramount importance to many scientific and technological developments across a broad spectrum of disciplines. Hard x-rays with excellent penetration power and high chemical sensitivity are suitable for speciation of heterogeneous (thick) materials. Here, we report nanoscale chemical speciation by combining scanning nanoprobe and fluorescence-yield x-ray absorption near-edge structure (nano-XANES). First, the resolving power of nano-XANES was demonstrated by mapping Fe(0) and Fe(III) states of a reference sample composed of stainless steel and hematite nanoparticles with 50-nm scanning steps. Nano-XANES was then used to study the trace secondary phases in lithium iron phosphate (LFP) particles. We observed individual Fe-phosphide nanoparticles in pristine LFP, whereas partially (de)lithiated particles showed Fe-phosphide nanonetworks. These findings shed light on the contradictory reports on Fe-phosphide morphology in the literature. Nano-XANES bridges the capability gap of spectromicroscopy methods and provides exciting research opportunities across multiple disciplines.

纳米尺度上的化学物种的分离对于跨学科的许多科学技术发展至关重要。具有出色穿透力和高化学敏感性的硬X射线适合于异质（厚）材料的形成。在这里，我们通过结合扫描纳米探针和荧光产量x射线吸收近边缘结构（nano-XANES）报告了纳米级化学物种。首先，通过以50纳米扫描步骤绘制由不锈钢和赤铁矿纳米粒子组成的参考样品的Fe（0）和Fe（III）状态，证明了纳米XANES的分辨能力。然后，将纳米XANES用于研究磷酸铁锂（LFP）颗粒中的痕量次级相。我们观察到原始LFP中的单个Fe-磷化物纳米颗粒，而部分（去）锂化的颗粒则显示出Fe-磷化物纳米网络。这些发现为文献中有关铁磷形态的矛盾报道提供了启示。纳米XANES弥补了光谱显微镜方法的能力差距，并为跨多个学科提供了令人兴奋的研究机会。