Semiconducting polymers with specific absorption are useful in various applications, including organic optoelectronics, optical imaging, and nanomedicine. However, the optical absorption of a semiconducting polymer with a determined structure is hardly tunable when compared with that of inorganic semiconductors. In this work, we show that the optical absorption of polymer nanoparticles from one conjugated backbone can be effectively tuned through judicious design of the particle morphology and the persistence length of polymers. Highly absorbing near-infrared (NIR) polymers based on diketopyrrolopyrrole-dithiophene (DPP-DT) are synthesized to have different molecular weights (MWs). The DPP-DT polymer with a large molecular weight and high persistence length exhibited remarkably high optical absorption with a peak mass extinction coefficient of 81.7 L g⁻¹ cm⁻¹, which is one of the highest value among various photothermal agents reported to date. Particularly, the polymer nanoparticles with different sizes exhibit broadly tunable NIR absorption peaks from 630 to 811 nm. The PEGylated small polymer dots (Pdots) show good NIR light-harvesting efficiency and high non-radiative decay rates, resulting in a relatively high photothermal conversion efficiency in excess of 50%. Thus, this Pdot-based platform can serve as promising photothermal agents and photoacoustic probes for cancer theranostics.

具有特定吸收率的半导体聚合物可用于各种应用，包括有机光电，光学成像和纳米医学。但是，与无机半导体相比，具有确定结构的半导体聚合物的光吸收几乎不可调节。在这项工作中，我们表明可以通过明智地设计颗粒形态和聚合物的持久性长度，有效地调节一个共轭主链上聚合物纳米颗粒的光吸收。基于二酮吡咯并吡咯并二噻吩（DPP-DT）的高吸收性近红外（NIR）聚合物被合成为具有不同的分子量（MWs）。分子量大和持久长度高的DPP-DT聚合物表现出显着的高光吸收，峰值消光系数为81。^-1  cm ^-1，这是迄今为止报道的各种光热剂中最高的值之一。特别地，具有不同尺寸的聚合物纳米颗粒表现出从630至811nm的宽可调的NIR吸收峰。聚乙二醇化的小聚合物点（Pdot）显示出良好的近红外光收集效率和高的非辐射衰减率，从而导致相对较高的光热转换效率超过50％。因此，这个基于Pdot的平台可以用作癌症治疗学的有前途的光热剂和光声探针。