As conjugated polymer nanoparticles (CPNs) have attracted growing interest as photoacoustic (PA) imaging contrast agents, revelation of the relationship between the molecular structure of conjugated polymers and PA property is highly in demand. Here, three donor–acceptor‐structured conjugated polymer analogs are designed, where only a single heteroatom of acceptor units changes from oxygen to sulfur to selenium, allowing for systematic investigation of the molecular structure–PA property relationship. The absorption and PA spectra of these CPNs can be facilely tuned by changing the heteroatoms of the acceptor units. Moreover, the absorption coefficient, and in turn the PA signal intensity, decreases when the heteroatom changes from oxygen to sulfur to selenium. As these CPNs exhibit weak fluorescence and similar photothermal conversion efficiency (≈70%), their PA intensities are approximately proportional to their absorption coefficients. The in vivo brain vasculature imaging in this study also demonstrates this trend. This study provides a simple but efficient strategy to manipulate the PA properties of CPNs through changing the heteroatom at key positions.

中文翻译：

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硫属元素化物变化在共轭聚合物纳米粒子中用于脑血管成像的光声性能的分子工程。

随着共轭聚合物纳米粒子（CPNs）作为光声（PA）成像造影剂引起了越来越多的兴趣，迫切需要揭示共轭聚合物的分子结构与PA性能之间的关系。在这里，设计了三个供体-受体结构的共轭聚合物类似物，其中只有一个受体单元的杂原子从氧到硫到硒发生变化，从而可以系统地研究分子结构-PA性质之间的关系。这些CPN的吸收光谱和PA光谱可以通过改变受体单元的杂原子来轻松调节。此外，当杂原子从氧变成硫再变成硒时，吸收系数以及PA信号强度都会降低。由于这些CPN表现出弱荧光和类似的光热转换效率（≈70％），因此它们的PA强度大约与其吸收系数成正比。这项研究中的体内脑血管成像也证明了这一趋势。这项研究提供了一种简单而有效的策略，通过改变关键位置的杂原子来操纵CPN的PA特性。