Luminescent nanoparticles with dual-mode long-lived luminescence are of great importance for their attractive applications in biosensing, bioimaging, and data encoding. Herein, we report the realization of up-and downconversion emission of Mn 2+ dopants in multilayer nanoparticles of NaGdF 4 :Yb/Tm@NaGdF 4 :Ce/Mn@NaYF 4 upon excitation at 980 and 254 nm, respectively. The dual-mode emission of the Mn 2+ dopants at 531 nm have a long-lived lifetime up to ∼30 ms as a result of the spin-forbidden optical transition of Mn 2+ within the 3d 5 configuration. After ceasing steady excitation at the two wavelengths, the long-lived feature of Mn 2+ luminescence allows a longer persistent time than lanthanide emissions, thereby enabling the ease of data decoding by a cell phone camera under a burst mode. The long-lived green upconversion emission also permits the generation of a long green tail emission upon dynamic excitation at 980 nm. These attributes make the as-prepared Mn 2+ -doped multilayer nanoparticles particularly attractive for multilevel anticounterfeiting.
Mo–Ni alloy nanoparticles were used as a bifunctional catalyst for ultrastable and efficient H2 production via membrane-free hybrid water electrolysis.
The development of earth-abundant catalysts for efficient hydrolysis of ammonia borane is of great importance in the conversion and utilization of hydrogen energy. Here, we report the synthesis of SiO 2 -encompassed Co@N-doped porous carbon assemblies as a new type of recyclable catalyst for the purpose by calcination of zeolitic imidazolate framework-67@SiO 2 microtubes at high temperatures under an N 2 atmosphere. We find that the surface layer of SiO 2 in the precursor microtubes is essential for the production of efficient catalysts by supplying an additional surface for Co nanoparticle dispersion in an effort to reduce their size. In addition, the SiO 2 layer renders a highly ordered arrangement of Co@N-doped porous carbon within the catalysts, possibly allowing the ease of mass transfer of ammonia borane within the catalysts. The optimized catalysts obtained via calcination at 800 °C show a set of remarkable catalytic benefits, including a high hydrogen generation rate of 8.4 mol min −1 mol (Co) −1 , a relatively low activation energy of 36.1 kJ mol −1 , and a remarkable reusability (at least 10 times). Our results can provide new insight into the design and synthesis of highly ordered SiO 2supported catalysts for different reactions.
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