Ultrabright Dibenzofluoran‐Based Polymer Dots with NIR‐IIa Emission Maxima and Unusual Large Stokes Shifts for 3D Rotational Stereo Imaging

Abstract

Emerging organic molecules with emissions in the NIR‐II region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR‐IIa (1300 nm) region faces challenges due to the intrinsic energy gap law. Up to current stage, all reported organic NIR‐IIa emitters belong to polymethine‐based dyes with small Stokes shifts (< 50 nm) and low quantum yield (≤ 0.015%). However, such polymethines have proved to cause self‐absorption with constrained emission brightness, limiting advanced development in deep‐tissue imaging. Here we design a new NIR‐IIa scaffold based on rigid and highly conjugated dibenzofluoran core terminated by amino‐containing moieties that reveal emission peaks of 1230–1305 nm. The quantum yield is at least 10 times higher than all synthesized or reported NIR‐IIa polymethines (Figure 1) with extraordinarily large Stokes shifts of 370–446 nm. DBF‐BJ was further prepared as a polymer dot to demonstrate its in vivo 3D stereo imaging of mouse vasculature with a 1400 nm long‐pass filter.This article is protected by copyright. All rights reserved