Nitrogen-doped-carbon-coated hexagonal cobalt oxyhydroxide/reduced graphene oxide nanocomposite for sensitive and selective detection of nitrite in human hepatoma cells

Tunable Impedance of Cobalt Loaded Carbon for Wide-Range Electromagnetic Wave Absorption

Impedance matching modulation of the electromagnetic wave (EMW) absorbers toward broad effective absorption bandwidth (EAB) is the ultimate aim in EMW attenuation applications. Here, a Joule heating strategy is reported for preparation of the Co-loaded carbon (Co/C) absorber with tunable impedance characteristics. Typically, the size of the Co can be regulated to range from single-atoms to clusters, and to nanocrystals. The varied sizes of the Co combined with different graphitization degrees of carbon can result in different relative input impedances and electromagnetic loss, leading to the tunable EMW absorption properties of the Co/C absorber. By meticulously coalescing the different prepared Co/C, the working frequency can be easily tuned, covering Ku, X, and C bands. Furthermore, the Co/C demonstrates a high EMW attenuation due to its unique dielectric loss capability and magnetic loss characteristics. The abundant interfaces of Co/C can also contribute to the enhanced interfacial polarization for improving EMW attenuation. This work demonstrates the importance of optimizing the metal and carbon interaction to the impedance matching toward wide EAB of the EMW absorbers.

Tumor acidity-activatable photothermal/Fenton nanoagent for synergistic therapy

Intracellular formation of therapeutic agents has become one of the effective ways for cancer-specific treatment. Herein, a tumor acidity-activatable photothermal/Fenton nanoagent (denoted as CoPy) was constructed based on oxidized zeolitic imidazolate framework-67 (oxZIF-67) nanosheet and pyrrole (Py) monomer for synergistic therapy. The CoPy showed negligible toxicity to normal cell models RAW264.7 and 3T3 cell lines, and could be degraded by ascorbic acid in normal physiological conditions. However, once uptaken by 4T1 cells, the acidic pH led to the release of Co³⁺, which served as a strong oxidant to induce the polymerization of Py to form polypyrrole (PPy) for site-specific photothermal therapy (PTT). Most appealingly, the PPy could chelate the generated Co²⁺ in the polymerization process to initiate the Fenton-like reaction, which was more capable to produce highly toxic hydroxyl radical (•OH) for chemodynamic therapy (CDT) compared to the free Co²⁺ ones. In vitro and in vivo experiments demonstrated that all functionalities on CoPy worked collaboratively, and 78% of tumors were inhibited through cooperative PTT/CDT. Such a novel therapeutic nanoagent with tumor selectivity opens new opportunities for combinational treatment paradigms.