A BODIPY‐Based Donor/Donor–Acceptor System: Towards Highly Efficient Long‐Wavelength‐Excitable Near‐IR Polymer Dots with Narrow and Strong Absorption Features

Bright long‐wavelength‐excitable semiconducting polymer dots (LWE‐Pdots) are highly desirable for in vivo imaging and multiplexed in vitro bioassays. LWE‐Pdots have been obtained by incorporating a near‐infrared (NIR) emitter into the backbone of a polymer host to develop a binary donor–acceptor (D–A) system. However, they usually suffer from severe concentration quenching and a trade‐off between fluorescence quantum yield (Φf) and absorption cross‐section (σ). Herein, we describe a ternary component (D1/D2–A) strategy to achieve ultrabright, green laser‐excitable Pdots with narrow‐band NIR emission by introducing a BODIPY‐based assistant polymer donor as D1. The D1/D2–A Pdots possess improved Φf and σ compared to corresponding binary D2–A Pdots. Their Φf is as high as 40.2 %, one of the most efficient NIR Pdots reported. The D1/D2–A Pdots show ultrahigh single‐particle brightness, 83‐fold brighter than Qdot 705 when excited by a 532 nm laser. When injected into mice, higher contrast in vivo tumor imaging was achieved using the ternary Pdots versus the binary D–A Pdots.