The green synthesis of nitrate (NO₃⁻) via electrocatalytic nitrogen oxidation reaction (NOR) is a promising strategy for artificial nitrogen fixation, which shows great advantages than traditional nitrate synthesis based on Haber–Bosch and Ostwald processes. But the poor N₂ absorption, high bond energy of N≡N (941 kJ·mol⁻¹), and competing multi-electron-transfer oxygen evolution reaction (OER) limit the activity and selectivity. Herein, we fabricated MXene-derived irregular TiO_2−x nanoparticles anchored Cu nanowires (Cu-NWs) electrode for efficient electrocatalytic nitrogen oxidation, which exhibits a NO₃⁻ yield of 62.50 μg·h⁻¹·mg_cat⁻¹ and a Faradaic efficiency (FE) of 22.04%, and a significantly enhanced NO₃⁻ yield of 92.63 μg·h⁻¹·mg_cat⁻¹, and a FE of 40.58% under vacuum assistance. The TiO_2−x/Cu-NWs electrode also shows excellent reproducibility and stability under optimal experimental conditions. Moreover, a Zn-N₂ reaction device was assembled with TiO_2−x/Cu-NWs as an anode and Zn plate as a cathode, obtaining an extremely high NO₃⁻ yield of 156.25 µg·h⁻¹·mg_cat⁻¹. The Zn-nitrate battery shows an open circuit voltage (OCV) of 1.35 V. This work provides novel strategies for enhancing the performance of ambient N₂ oxidation to obtain higher NO₃⁻ yield.

The toxicity of nanoparticles in a biological system is an integration of effects arising from surface functionality, particle size, ionic dissolution, etc. This complexity suggests that generalization of a material's toxicity may be inappropriate. Moreover, from a medicinal point of view, toxicity can be used for treatment of malignant cells, such as cancer. In this study, highly biocompatible carbon nanodots (gCDs) were synthesized by reacting citric acid and urea in glycerol, which resulted in abundant hydroxyl functional groups on the particle surface. gCDs show excitation-dependent photoluminescence but with bright green to yellow emission. Importantly, a series of toxicity assessments showed that as-synthesized gCDs possessed exceptional biocompatibilities to various biological entities including 18 bacteria species, Petunia axillaris seedlings, and Artemia franciscana nauplii. Furthermore, the particles were shown to have low to no toxic effects on human embryonic kidney (HEK-293), breast (MCF-7), and oral squamous (CAL-27) carcinoma cell lines. Of particular interest, the gCDs displayed antiproliferative activities against ovarian choriocarcinoma cells (JAr/Jeg-3 cell lines), which may be further explored for cancer drug discovery.