Vapour-phase-transport rearrangement technique for the synthesis of new zeolites

Owing to the significant difference in the numbers of simulated and experimentally feasible zeolite structures, several alternative strategies have been developed for zeolite synthesis. Despite their rationality and originality, most of these techniques are based on trial-and-error, which makes it difficult to predict the structure of new materials. Assembly-Disassembly-Organization-Reassembly (ADOR) method overcoming this limitation was successfully applied to a limited number of structures with relatively stable crystalline layers (UTL, UOV, *CTH). Here, we report a straightforward, vapour-phase-transport strategy for the transformation of IWW zeolite with low-density silica layers connected by labile Ge-rich units into material with new topology. In situ XRD and XANES studies on the mechanism of IWW rearrangement reveal an unusual structural distortion-reconstruction of the framework throughout the process. Therefore, our findings provide a step forward towards engineering nanoporous materials and increasing the number of zeolites available for future applications.

Hetero CuOx/ZnO micro-/nanostructure: Carbothermal reduction–vapour phase transport

ZnO micro-/nanostructures were synthesized by the carbothermal reduction–chemical vapour transport method. This work is focused on the effect of the substrate temperature and Cu catalyst layer on the shape and geometry of ZnO micro-/nanostructures. The thermally oxidized Cu template affects the structure, chemical identity, optical and photoluminescence properties of the ZnO micro-/nanostructure and results in a CuOx/ZnO heterostructure. SEM studies give a direct evidence of the role of deposition temperature and Cu catalyst in the formation of a stable hemisphere based wire, a comb-like cantilever, a javelin-like tetrapod, a spherical and polyhedral cage of ZnO. XRD and Raman measurements confirm a hexagonal wurtzite structure of the ZnO micro-/nanostructure. The absorption edge of the ZnO/CuOx heterostructure is redshifted in comparison to the pure ZnO structure. PL studies indicate that the UV emission can be suppressed significantly while the green emission is enhanced due to the change in the morphology of ZnO micro-/nanostructures.

Grain-growth engineering and mechanical properties of physical-vapour-deposited InSe platelets

The present work demonstrates a novel use of physical vapour deposition for grain-growth engineering by optimizing supersaturation, which led to the evolution of stoichiometric indium monoselenide crystals, employing a custom-fabricated dual-zone furnace. The growth zone was kept at a constant temperature for different experimental runs (673–883 K), while the source zone was kept at a stable temperature of 1123 K. In this way, the temperature difference ΔT= 240–450 K resulted in a significant increase of the mass transport between the zones so as to accomplish bulk crystallization. At comparatively low supersaturation (ΔT= 240 K), the presence of nodules and flakes was observed. When ΔT= 250 K, multiple grains were formed owing to temperature asymmetry at the rough vapour–solid interface. A further increase in supersaturation (ΔT= 330 K) facilitated polyhedral grain growth, with distinct grain boundaries. A subsequent increment in ΔT(400 K) led to evolution of the polycrystalline morphology to well developed hexagonal platelets owing to adsorption of atoms on surface steps and kinks in accordance with the leading-edge growth mechanism. Energy-dispersive analysis by X-rays and X-ray diffraction experiments were carried out to confirm the structure and phase of crystals. Microindentation studies were done to assess the hardness and mechanical stability of the as-grown crystals in response to external loads in order to explore their suitability for solar cell applications. The investigations of bulk vapour phase transport, morphology and strengthening of InSe platelets provide pathways for the production of crystalline textures with versatile properties.

Enhanced detection of nitrogen dioxide via combined heating and pulsed UV operation of indium oxide nano-octahedra

We report on the use of combined heating and pulsed UV light activation of indium oxide gas sensors for enhancing their performance in the detection of nitrogen dioxide in air. Indium oxide nano-octahedra were synthesized at high temperature (900 °C) via vapour-phase transport and screen-printed onto alumina transducers that comprised interdigitated electrodes and a heating resistor. Compared to the standard, constant temperature operation of the sensor, mild heating (e.g., 100 °C) together with pulsed UV light irradiation employing a commercially available, 325 nm UV diode (square, 1 min period, 15 mA drive current signal), results in an up to 80-fold enhancement in sensitivity to nitrogen dioxide. Furthermore, this combined operation method allows for making savings in power consumption that range from 35% to over 80%. These results are achieved by exploiting the dynamics of sensor response under pulsed UV light, which convey important information for the quantitative analysis of nitrogen dioxide.

Single-crystalline ternary mixed metal oxide 1-dimensional nanostructures of Ir1−x−yRuxVyO2 by vapour phase transport

Highly single-crystalline Ir1−x−yRuxVyO2 nanowires were grown from metal oxide precursors on a Si wafer by a vapour transport process.

Probing luminescent Fe-doped ZnO nanowires for high-performance oxygen gas sensing application

Successful demonstration of Fe-doped ZnO nanowires using a facile vapour phase transport synthesis method for high-performance oxygen gas sensing application.