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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]

Zeolites and metal-doped zeolites are now widely considered as low-temperature hydrocarbon traps to be a part of emission control systems in automobiles. However, due to the high temperature of exhaust gases, the thermal stability of such sorbent materials is of great concern. To avoid the thermal instability problem, in the present work, laser electrodispersion was used to deposit Pd particles on the surface of ZSM-5 zeolite grains (SiO2/Al2O3 = 55 and SiO2/Al2O3 = 30) to obtain Pd/ZSM-5 materials with a Pd loading as low as 0.03 wt.%. The thermal stability was evaluated in a prompt thermal aging regime involving thermal treatment at temperatures up to 1000 °C in a real reaction mixture (CO, hydrocarbons, NO, an excess of O2, and balance N2) and a model mixture of the same composition with the exception of hydrocarbons. Low-temperature nitrogen adsorption and X-ray diffraction analysis were used to examine the stability of the zeolite framework. Special attention was paid to the state of Pd after thermal aging at varied temperatures. By means of transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV–Vis spectroscopy, it was shown that palladium, having been initially located on the surface of zeolite, undergoes oxidation and migrates into the zeolite's channels. This enhances the trapping of hydrocarbons and their subsequent oxidation at lower temperatures. [ABSTRACT FROM AUTHOR]

Pd/Al2O3 catalyst of the "crust" type with Pd loading of 0.03 wt.% was prepared by the deposition of 2 nm Pd particles on the outer surface of the alumina support using laser electrodispersion (LED). This technique differs from a standard laser ablation into a liquid in that the formation of monodisperse nanoparticles occurs in the laser torch plasma in a vacuum. As is found, the LED-prepared catalyst surpasses Pd-containing three-way catalysts, obtained by conventional chemical synthesis, in activity and stability in CO oxidation under prompt thermal aging conditions. Thus, the LED-prepared Pd/Al2O3 catalyst showed the best thermal stability up to 1000 °C. The present research is focused on the study of the high-temperature evolution of the Pd/Al2O3 catalyst in two reaction mixtures by a set of physicochemical methods (transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance UV-vis spectroscopy). In order to follow the dispersion of the Pd nanoparticles during the thermal aging procedure, the testing reaction of ethane hydrogenolysis was also applied. The possible reasons for the high stability of LED-prepared catalysts are suggested. [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]

BACKGROUND: Palladium particles with a size of 2 nm were obtained by laser electrodispersion (LED) and used to prepare the Pd‐ZnHZSM‐5(LED) catalyst (Pd = 0.0005 wt%). The deposition of the LED palladium particles on the surface of ZnHZSM‐5 provided a high dimethyl ether (DME) conversion into liquid hydrocarbons; the percentage of the unreacted intermediate (methanol) decreased by an order of magnitude and the selectivity for i‐alkanes increased (more than 80 wt%). The Pd‐ZnНZSM‐5(LED) catalyst showed higher activity and selectivity than the traditional Pd‐ZnНZSM‐5 catalyst (impregnation). RESULTS: The features of the catalytic action of Pd‐ZnHZSM‐5(LED) are associated with the high density of nanosized Pd0 and Pd2+ phases on the ZnHZSM‐5 surface. The LED particles are immersed in the surface of the zeolite to a maximum depth of 0.5 nm and do not penetrate deep into the pores of the zeolite. In Pd‐ZnНZSM‐5(LED), the zinc sites and palladium sites are separate. On Brønsted acid sites and zinc sites in the micropores of the zeolite occure target reactions. Part of arenes and unreacted alkenes exit the pores of zeolite are hydrogenated on the palladium. The product obtained on Pd‐ZnHZSM‐5(LED) is characterized by a high content of i‐alkanes (more than 80 wt%) and a low content of arenes (no more than 5 wt%). CONCLUSION: The results demonstrate the high promise of the LED method for the preparation of high‐performance catalysts with ultra‐low content of noble metal for conversion of oxygenates to synthetic liquid hydrocarbons with a high yield of i‐alkanes and low yield of arenes. © 2022 Society of Chemical Industry (SCI). [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]

NiPd bimetallic systems were for the first time synthesized by laser electrodispersion (LED) of the Ni77Pd23 alloy target followed by the deposition of produced bimetallic particles on a TEM copper grid and alumina granules. Selective area energy-dispersive analysis confirms the bimetallic nature of NiPd particles deposited on a TEM copper grid. Their mean size is 1.0 nm according to TEM. XPS data demonstrate that under deposition on alumina granules (total metal content of 0.005 wt.%), nickel in bimetallic particles nearly completely oxidizes to Ni2+ species predominantly in the form of aluminate. At the same time major part of palladium (84%) exists in Pd0 but oxidizes to Pd2+ (80%) during 6 months storage in air. Both metals are deposited on the external surface of alumina granules and localized in the same areas. In situ reduction of both metals by H2 in the catalytic cell of XPS spectrometer is hindered. Nickel is not reduced even at 450°C, confirming the formation of NiAlOx, whereas palladium is reduced at higher temperatures compared to a similar monometallic catalyst. Nevertheless, NiPd/Al2O3 catalyst is more efficient in gas-phase chlorobenzene hydrodechlorination at 150–350°C than Ni/Al2O3 and even Pd/Al2O3, and much more stable. The difference may be caused by the formation of new active sites due to the contact between Pd0 and NiAlOx-modified support, and the protective action of spinel reacting with HCl by-product. [ABSTRACT FROM AUTHOR]

Silicon-based structures comprised of crystalline silicon substrates and active layers of mixed silicon and gold nanoparticles were fabricated and characterized. Several layer compositions were studied. The investigated structures demonstrate very large spectral sensitivity (more than 10 A W−1) in the wide spectral range (400-1000 nm). Such large sensitivity implies presence of photocurrent amplification. A model which involves dual mechanism of the photoresponse was proposed in order to explain the appearance of the photocurrent amplification in the investigated structures. Spectral sensitivity of the structure with composite layer of Si and Au nanoparticles on Si substrate (Au volume fraction is ∼50%) at reverse bias voltage of −0.4 V. [ABSTRACT FROM AUTHOR]

We report a new technique of amorphous metal nanoparticles fabrication based on generation of liquid metal microdrops, their charging in electron flux with subsequent drops fission. Fission of charged metal drop occurs when its charge exceeds a critical value given by Rayleigh instability condition. Nanosize droplets, resulted from fission, cool down at extremely high rate to produce amorphous metal nanoparticles. Initial metal microdrops are generated at the end of an anode tip exposed to strong electric field and electron flux focused to the tip. The emitted drops then enter an electron beam where they are charged up to instability and are involved in fission process. To eliminate secondary electron emission (SEE) which can prevent drop charging we used electron beams of low energy. With beam energy properly chosen, SEE coefficient is less then unity for all drop sizes and drop charging up to unstable state is ensured. Granular films consisting of amorphous copper particles 2 nm in size are fabricated by the described technique. The results of atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies of the fabricated films are presented. Possible applications of the fabricated structures related to their unusual properties are considered. [ABSTRACT FROM AUTHOR]

Laser electrodispersion (LED) of metals is a promising technique for the preparation of heterogeneous catalysts as an alternative to wet impregnation of supports with the corresponding salt solutions. The LED technique can be used to deposit highly active chloride-and nitrate-free metal nanoparticles onto carbon or oxide supports. We report preparation and properties of new Ni-, Pd-, and Au-containing alumina-supported catalysts with low metal loadings (10-3-10-4 % mass) and their comparison with the previously studied carbon (Sibunit) supported systems. The catalysts demonstrate high stability and extremely high specific catalytic activity (by 2-3 orders of magnitude higher than for traditional catalysts) in the gas-phase hydrodechlorination (HDC) of chlorobenzene (CB). [ABSTRACT FROM AUTHOR]