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Halide perovskites are a class of semiconductors with strong direct interband transition and high mobility of charge carriers resulting in bright luminescence, which can be easily tuned chemically in a broad spectral range. Moreover, perovskites can be synthesized by means of simple wet chemistry approaches on arbitrary surfaces, opening new avenues for perovskites integration with a plethora of other functional materials. Here, this work reports on a versatile platform for reversible switching of halide perovskite's optical properties enabled by high‐index phase‐change materials (Ge‐Sb‐Te) serving as an active subnanolayer, which controls the perovskite film's behavior. Based on this approach, this work demonstrates micro‐QR‐coding and switchable bright emission, whose wavelength can be adjusted in the whole visible range. [ABSTRACT FROM AUTHOR]

New Pt-Co catalysts of hydrogen purification from CO impurities for fuel cells were fabricated via the deposition of monodispersed 1.7 nm Pt nanoparticles using laser electrodispersion on Co-modified ZSM-5 prepared by the Co(CH3COO)2 impregnation. The structure of prepared Pt-Co zeolites was studied by low-temperature N2 sorption, TEM, EDX, and XPS methods. The comparative analysis of samples with different Pt (0.01–0.05 wt.%) and Co (2.5–4.5 wt.%) contents on zeolites with the ratio of Si/Al = 15, 28, and 40 was performed in the CO-PROX reaction in H2-rich mixture (1%CO + 1%O2 + 49%H2 + 49%He). The synergistic catalytic action of Pt and Co on zeolite surface makes it possible to completely remove CO from a mixture with hydrogen in a wide temperature range from 50 to 150 °C; the high efficiency of designed composites with low Pt loading is maintained for a long time. The enhancement of PROX performance originates from the formation of new active sites for the CO oxidation at the Pt-Co interfaces within zeolite channels and at the surface. In terms of their activity, stability, and selectivity, such composites are significantly superior to known supported Pt-Co catalysts. [ABSTRACT FROM AUTHOR]

Tunable and ultracompact optical elements are highly important for the development of advanced nanophotonics. Such elements significantly expand the capabilities of photonic circuits and devices. Phase changing materials based on Ge‐Sb‐Te composition are very promising for tunable nanophotonic elements. This family of materials is excellent for the creation of tunable optical elements, since it has a non‐volatile reversible phase transition and exhibits a strong modulation of the dielectric permittivity in broad spectral range. In this work, fabrication of Ge‐Sb‐Te nanoparticles by laser ablation as well as strong and repeatable changing of their optical properties by fs‐laser irradiation are demonstrated. Beside the control of linear optical response, switchable second harmonic generation from Ge‐Sb‐Te nanoparticles over two orders of magnitude after the phase change is also demonstrated. [ABSTRACT FROM AUTHOR]