Optical coherence tomography (OCT) is an imaging technique affording noninvasive optical biopsies. Like for other imaging techniques, the use of dedicated contrast agents helps better discerning biological features of interest during the clinical practice. Although bright OCT contrast agents have been developed, no dark counterpart has been proposed yet. Herein, plasmonic copper sulfide nanoparticles as the first OCT dark contrast agents working in the second optical transparency window are reported. These nanoparticles virtually possess no light scattering capabilities at the OCT working wavelength (≈1300 nm); thus, they exclusively absorb the probing light, which in turn results in dark contrast. The small size of the nanoparticles and the absence of apparent cytotoxicity support the amenability of this system to biomedical applications. Importantly, in the pursuit of systems apt to yield OCT dark contrast, a library of copper sulfide nanoparticles featuring plasmonic resonances spanning the three optical transparency windows is prepared, thus highlighting the versatility and potential of these systems in light-controlled biomedical applications.

中文翻译：

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等离子体等离子硫化铜纳米粒子使光学相干断层扫描中产生暗对比度。

光学相干断层扫描（OCT）是提供无创光学活检的成像技术。像其他成像技术一样，专用造影剂的使用有助于在临床实践中更好地识别感兴趣的生物学特征。尽管已经开发出了明亮的OCT造影剂，但尚未提出任何深色的对比剂。在此，报道了在第二光学透明窗中起作用的作为第一OCT深色造影剂的等离子体铜硫化物纳米粒子。这些纳米粒子实际上在OCT工作波长（约1300 nm）下不具有光散射能力。因此，它们仅吸收探测光，从而导致暗对比度。纳米粒子的小尺寸和明显的细胞毒性的缺乏支持了该系统对生物医学应用的适应性。