Mitophagy has a critical role in maintaining cellular homeostasis through acidic lysosomes engulfing excess or impaired mitochondria, thereby pH fluctuation is one of the most significant indicators for tracking mitophagy. Then such precise pH tracking demands the fluorogenic probe that has tailored contemporaneous features, including mitochondrial-specificity, excellent biocompatibility, wide pH-sensitive range of 8.0–4.0, and especially quantitative ability. However, available molecular probes cannot simultaneously meet all the requirements since it is extremely difficult to integrate multiple functionalities into a single molecule. To fully address this issue, we herein integrate two fluorogenic pH sensitive units, a mitochondria-specific block, cell-penetrating facilitator, and biocompatible segments into an elegant silica nano scaffold, which greatly ensures the applicability for real-time tracking of pH fluctuations in mitophagy. Most significantly, at a single wavelength excitation, the integrated pH-sensitive units have spectra-distinguishable fluorescence towards alkaline and acidic pH in a broad range that covers mitochondrial and lysosomal pH, thus enabling a ratiometric analysis of pH variations during the whole mitophagy. This work also provides constructive insights into the fabrication of advanced fluorescent nanoprobes for diverse biomedical applications.

Tailoring the nanostructure/morphology and chemical composition is important to regulate the electronic configuration of electrocatalysts and thus enhance their performance for water and urea electrolysis. Herein, the nitrogen-doped carbon-decorated tricomponent metal phosphides of FeP₄ nanotube@Ni-Co-P nanocage (NC-FNCP) with unique nested hollow architectures are fabricated by a self-sacrifice template strategy. Benefiting from the multi-component synergy, the modification of nitrogen-doped carbon, and the modulation of nested porous hollow morphology, NC-FNCP facilitates rapid electron/mass transport in water and urea electrolysis. NC-FNCP-based anode shows low potentials of 248 mV and 1.37 V (vs. reversible hydrogen electrode) to attain 10 mA/cm² for oxygen evolution reaction (OER) and urea oxidation reaction (UOR), respectively. In addition, the overall urea electrolysis drives 10 mA/cm² at a comparatively low voltage of 1.52 V (vs. RHE) that is 110 mV lower than that of overall water electrolysis, as well as exhibits excellent stability over 20 h. This work strategizes a multi-shell-structured electrocatalyst with multi-compositions and explores its applications in a sustainable combination of hydrogen production and sewage remediation.