Cu_2–xSe nanoparticles are part of a promising class of alternative plasmonic materials where the location, stability, and structural impact of charge carrier generation are crucial to their optoelectronic performance. Here, electron paramagnetic resonance spectroscopy is used to identify the location and dynamics of Cu²⁺ environments that form upon air-induced oxidation of Cu_2–xSe nanoparticles. The results indicate the formation of two distinct Cu²⁺ environments at or near the surface of the nanoparticle. The first environment can be assigned to Cu²⁺ bound to oleylamine capping ligands, and the second can be assigned to Cu²⁺ located in CuO domains. In addition, these experiments indicate that the observed Cu²⁺ environments are consistent with vacancy formation on the Cu sublattice, which are mobile (i.e., vacancy hopping) at temperatures down to 180 K. Taken together, our results elucidate time scales of air-mediated Cu oxidation in Cu_2–xSe nanoparticles, the chemical environments of the resulting Cu²⁺ species, and the impact of this oxidation on the overall particle crystallographic structure and optoelectronic properties.

中文翻译：

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Cu _{2– x} Se纳米粒子中表面铜（II）环境的演变

Cu _{2- x} Se纳米粒子是一种有前途的替代等离子体材料的一部分，其中电荷载流子产生的位置，稳定性和结构影响对其光电性能至关重要。在这里，电子顺磁共振波谱被用于识别在空气诱导下的Cu _{2– x} Se纳米粒子氧化后形成的Cu ²⁺环境的位置和动力学。结果表明在纳米粒子的表面处或附近形成了两个不同的Cu ²⁺环境。可以将第一个环境分配给与油胺封端配体结合的Cu ²⁺，将第二个环境分配给Cu ²⁺位于CuO域中。此外，这些实验表明，观察到的Cu ²⁺环境与Cu亚晶格上的空位形成是一致的，Cu子晶格在低至180 K的温度下是可移动的（即空位跳跃）。介导的Cu _{2– x} Se纳米颗粒中的Cu氧化，所得Cu ²⁺物种的化学环境以及这种氧化对整体颗粒晶体结构和光电性能的影响。