One constraint of semiconducting polymer dots (Pdots), especially those with near-IR emission, is their low effective emitter ratio (∼1.5 mole percent), which limits their pH sensing performance. The other critical issue of existing Pdot-based pH sensors is their poor photostability. To address these issues, we developed a series of Pdots by dendronizing the squaraine-based pH responsive near-IR emitter, which is covalently incorporated into the polyfluorene (PFO) backbone. The fluorescence self-quenching of the NIR squaraine emitter was effectively suppressed at a high emitter concentration of 5 mole percent. Through controlling the individually incomplete energy transfer from the amorphous PFO donor to the blue β-phase PFO and NIR squaraine emitter, we obtained a ratiometric pH sensor with simultaneously improved pH sensitivity, brightness, and photostability. The Pdots showed a fast and reversible pH response over the whole biological pH range of 4.7 to 8.5. Intracellular pH mapping was successfully demonstrated using this ultra-bright and photostable Pdot-based pH indicator.

中文翻译：

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通过对近红外发射器进行树突化处理，实现了高度光稳定的宽动态范围pH敏感型半导体聚合物点

半导体聚合物点（Pdots），尤其是具有近红外发射的聚合物点（Pdots）的一个制约因素是它们的有效发射极比率低（约1.5摩尔％），这限制了它们的pH传感性能。现有的基于Pdot的pH传感器的另一个关键问题是其光稳定性差。为解决这些问题，我们通过对基于方酸的pH响应近红外发射体进行了树突化处理，开发了一系列的Pdot，该发射体共价结合到聚芴（PFO）主链中。在5摩尔％的高发射体浓度下，NIR方酸类发射体的荧光自猝灭得到了有效抑制。通过控制从非晶态PFO供体到蓝色β相PFO和NIR方酸类发射体的不完全能量转移，我们获得了一种比例式pH传感器，同时提高了pH灵敏度，亮度，和光稳定性。Pdots在4.7至8.5的整个生物pH范围内均显示出快速且可逆的pH响应。使用这种超亮且光稳定的基于Pdot的pH指示剂成功地证明了细胞内pH定位。