RESUMEN
Upconverting infrared light into visible light via the triplet-triplet annihilation process in solid state is important for various applications including photovoltaics, photodetection, and bioimaging. Although inorganic semiconductors with broad absorption and negligible exchange energy loss have emerged as promising alternative to molecular sensitizers, currently, they have exclusively suffered from low efficiency and contained toxic elements in near-infrared (NIR)-to-visible upconversion. Here, we report an ultrathin bilayer film for NIR-to-visible upconversion based on atomically thin two-dimensional (2D) monolayer semiconductors. The atomic flatness and strong light absorption of 2D monolayer semiconductors enable ultrafast energy transfer and robust NIR-to-visible emission with a high upconversion quantum yield (1.1 ± 0.2%) at modest incident power (260 mW cm-2). Increasing layer thickness adversely quenches the upconversion emission, highlighting the 2D advantage. Considering the whole library of 2D semiconductors, the facile large-scale production and the ultrathin solid-state architecture open a new research field for solid-state upconversion applications.
RESUMEN
Long-term fertilization causes the differences in water, heat, nutrients and microbial activities between topsoil and deep soil, with consequences on the decomposition and turnover of straw carbon (C) in soils. At a long-term positioning experimental station in Shenyang Agricultural University, we mixed the topsoil (0-20 cm) and deep soil (40-60 cm) samples from different fertilization treatments with 13C-labeled straw for in-situ incubation. We analyzed the content of organic C and its δ13C value in soil aggregates, compared the difference in the distribution of straw C between topsoil and deep soil aggregates, and explored the effects of fertilization on the sequestration of straw C in soil aggregates. Compared with fertilization treatments (i.e., single chemical nitrogen fertilizer application and combination of organic manure with nitrogen fertilizer application), the treatment without fertilization increased the content of straw C of <0.053 mm aggregate in the topsoil by 106.7% and that of >0.25 mm aggregate in the deep soil by 34.2%. The contribution percentage of straw C to organic C of >0.053 mm aggregate in the deep soil was about two times of that in the topsoil. About 22.6% and 11.4% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of topsoil, and about 29.4% and 8.8% of straw C was distributed into the >0.25 mm and <0.25 mm aggregates of deep soil, respectively. In conclusion, straw addition promoted the regeneration and sequestration of carbon in deep soil macroaggregates and increased the carbon sequestration potential of deep soil.