THQ–Xanthene: An Emerging Strategy to Create Next‐Generation NIR‐I/II Fluorophores

Near‐infrared fluorescence imaging is vital for exploring the biological world. The short emissions (<650 nm) and small Stokes shifts (<30 nm) of current xanthene dyes obstruct their biological applications since a long time. Recently, a potent and universal THQ structural modification technique that shifts emission to the NIR‐I/II range and enables a substantial Stokes shift (>100 nm) for THQ‐modified xanthene dyes is established. Thus, a timely discussion of THQ–xanthene and its applications is extensive. Hence, the advent, working principles, development trajectory, and biological applications of THQ–xanthene dyes, especially in the fields of fluorescence probe‐based sensing and imaging, cancer theranostics, and super‐resolution imaging, are introduced. It is envisioned that the THQ modification tactic is a simple yet exceptional approach to upgrade the performance of conventional xanthene dyes. THQ–xanthene will advance the strides of xanthene‐based potentials in early fluorescent diagnosis of diseases, cancer theranostics, and imaging‐guided surgery.