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Fluorescence imaging in the second near‐infrared II (NIR‐II) window is opening up new possibilities in bioimaging due to its low scattering rate within the tissue. The integration of 2D materials with NIR‐II fluorescence will enable the development of multifunctional imaging probes. However, there are very few 2D materials that can fluoresce in the NIR‐II range. Monolayer WSe2 is a potential 2D material, but its photoluminescence (PL) around 790 nm is still far from the NIR‐II range due to its bandgap of 1.54 eV. In this study, it is investigated the electronic structures, dielectric functions, and PL spectra for Te, I, and Cr‐doped monolayer WSe2, as well as W and S vacant monolayer WSe2. Most of the defected monolayer WSe2 remain semiconductors, except for a few configurations exhibiting metallic properties after making vacancies. Among the monolayer WSe2 under investigation, the Cr‐doped WSe2 performs the best, exhibiting a strong PL peak in NIR‐II with a decreased bandgap around 1.0 eV. As increasing Cr concentration, the peak shifts further toward the red end of the spectrum due to an enhancement of p–d transition. The results provide a useful guideline for material synthesis applied in NIR‐II bioimaging and other biophysics. [ABSTRACT FROM AUTHOR]

The construction of nanozymes at the atomic level that hold structural stability and high enzyme-like activity is now a key factor in the optimization of an artificial enzyme. Single-atom metal/cerium oxide (CeO2)-based nanozymes have been demonstrated to possess a variety of enzymatic activities and radical scavenging abilities, which are mainly attributed to the single-atom active site, redox valence states, and abundant defect chemistry. Here, we developed a single-atom Pd/CeO2 nanostructure by aqueous phase synthesis that exhibits the advantages of high yield and good stability. The Pd/CeO2 nanostructure possesses peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) activities as well as reactive nitrogen species free-radical scavenging activity, exhibiting multienzyme-like activities and stability compared with CeO2 and other metal-based nanozymes. It is worth mentioning that the Pd/CeO2 nanostructure exhibits high POD-mimicking activity with a reaction rate of 0.88 μM/min, about 5 times higher than that of the CeO2 nanozyme. In addition, the CAT-like activity of the Pd/CeO2 nanostructure is excellent, and its scavenging rate of hydrogen peroxide reached nearly 100% at a concentration of 50 ng/μL. The present work shows that single-atom Pd substitution is a promising strategy for the design of CeO2 nanozymes to exert better effects on biomedical applications, especially with diseases related to oxidative stress. [ABSTRACT FROM AUTHOR]

Excessive accumulation of reduced nicotinamide adenine dinucleotide (NADH) within biological organisms is closely associated with many diseases. It remains a challenge to efficiently convert superfluous and detrimental NADH to NAD + . NADH oxidase (NOX) is a crucial oxidoreductase that catalyzes the oxidation of NADH to NAD + . Herein, M 1 M 2 (M i =V/Mn/Fe/Co/Cu/Mo/Rh/Ru/Pd, i = 1 or 2) mated-atom nanozymes (MANs) are designed by mimicking natural enzymes with polymetallic active centers. Excitingly, RhCo MAN possesses excellent and sustainable NOX-like activity, with K m-NADH (16.11 μM) being lower than that of NOX-mimics reported so far. Thus, RhCo MAN can significantly promote the regeneration of NAD + and regulate macrophage polarization toward the M2 phenotype through down-regulation of TLR4 expression, which may help to recover skin regeneration. However, RhRu MAN with peroxidase-like activity and RhMn MAN with superoxide dismutase-like activity exhibit little modulating effects on eczema. This work provides a new strategy to inhibit skin inflammation and promote skin regeneration.