Carbon dots (CDs) with excellent cytocompatibility, tunable optical properties, and simple synthesis routes are highly desirable for use in optical bioimaging. However, the majority of existing CDs are triggered by ultraviolet/blue light, presenting emissions in the visible/first near‐infrared (NIR‐I) regions, which do not allow deep tissue penetration. Emerging research into CDs with NIR‐II emission in the red region has generated limited designs with poor quantum yield, restricting their in vivo imaging applications due to low penetration depth. Developing novel CDs with NIR‐II emissions and high quantum yield has significant and far‐reaching applications in bioimaging and photodynamic therapy. Here, it is developed for the first time Fe‐doped CDs (Fe‐CDs) exhibiting the excellent linear relationship between 900–1200 nm fluorescence‐emission and pH values, and high quantum yield (QY‐1.27%), which can be used as effective probes for in vivo NIR‐II bioimaging. These findings demonstrate reliable imaging accuracy in tissue as deep as 4 mm, reflecting real‐time pH changes comparable to a standard pH electrode. As an important example application, the Fe‐CDs probe can non‐invasively monitor in vivo gastric pH changes during the digestion process in mice, illustrating its potential applications in aiding imaging‐guided diagnosis of gastric diseases or therapeutic delivery.

, the most abundant tea polyphenol, possesses excellent anti-inflammation properties. Emerging studies proved its potent potential as an immune checkpoint (ICP) inhibitor for anticancer therapy. However, the low bioavailability of EGCG reduces its treatment efficiency. In this work EGCG-based nanomedicine EGCG−ZIF-8@PDA−PEG (EZP) was developed via the coordination between ZIF-8 MOF and EGCG, followed by polydopamine and PEG functionalization for efficient tumor-targeting EGCG delivery. Results demonstrated that the EGCG loading rate in EZP reached up to 85%. Both in vitro and in vivo studies proved that the EZP nanoparticles were capable of inhibiting the expression of ICP molecules and modulating the inflammatory tumor microenvironment, evidenced by the suppression of PD-L1 expression, the reduction of inflammatory cytokines, and the resultant decline in the number of immunosuppressive cells, for instance, myeloid-derived suppressor cells, tumor-associated macrophages, and regulatory T cells. These synergistic effects significantly improved the infiltration of dendritic cells and T cells in tumors, realizing an inspiring antitumor effect.