Because of the remarkable efficiency in phototherapeutic modality, organic chromophores with the ability to absorb near-infrared (NIR) light have been regarded as powerful bullets against many intractable diseases. However, the suboptimal disease-targeting effect of NIR chromophores is still an obstacle to clinical applications because they may cause undesirable NIR injuries to healthy tissues. In light of the acidic conditions stemming from severe microenvironments in some diseased tissues, developing “turn-on”-type NIR chromophores with acid-responsive photophysical properties would be a feasible approach for promoting disease selectivity. In this focus review, strategies for designing pH-sensitive NIR organic chromophores are summarized based on the analysis of their photophysical relaxation processes, including the enhancement of internal conversion and intersystem crossing of those chromophores in response to acidic conditions. The former is beneficial for promoting the photothermal conversion efficiency, and the latter facilitates the generation of singlet oxygen species. In addition, the applications of some representative pH-sensitive NIR chromophores are also exemplified and highlighted to provide a perspective for disease-selective photothermal therapy and photodynamic therapy.

由于光疗法的显着效率，具有吸收近红外（NIR）光能力的有机发色团被认为是抵抗许多顽固性疾病的强大子弹。但是，NIR发色团对疾病的靶向效果欠佳仍然是临床应用的障碍，因为它们可能对健康组织造成不良的NIR损伤。鉴于某些患病组织中严重的微环境导致的酸性条件，开发具有酸响应性光物理特性的“开启”型近红外发色团将是提高疾病选择性的一种可行方法。在此重点综述中，基于对pH敏感的NIR有机发色团的光物理弛豫过程的分析，总结了设计策略，包括响应酸性条件而增强这些发色团的内部转化和系统间杂交。前者有利于提高光热转化效率，而后者有利于单线态氧物种的产生。此外，还举例说明并突出了一些代表性的pH敏感NIR发色团的应用，为疾病选择性光热疗法和光动力疗法的发展提供了前景。