Single-electron transport in electrically tunable nanomagnets

We study a single-electron transistor (SET) based upon a II–VI semiconductor quantum dot doped with a single-Mn ion. We present evidence that this system behaves like a quantum nanomagnet whose total spin and magnetic anisotropy depend dramatically both on the number of carriers and their orbital nature. Thereby, the magnetic properties of the nanomagnet can be controlled electrically. Conversely, the electrical properties of this SET depend on the quantum state of the Mn spin, giving rise to spin-dependent charging energies and hysteresis in the Coulomb blockade oscillations of the linear conductance.

BETA Zeolite Thin Films Supported on Honeycomb Monoliths with Tunable Properties as Hydrocarbon Traps under Cold-Start Conditions

A high percentage of hydrocarbon (HC) emissions from gasoline vehicles occur during the cold-start period. Among the alternatives proposed to reduce these HC emissions, the use of zeolites before the three-way catalyst (TWC) is thought to be very effective. Zeolites are the preferred adsorbents for this application; however, to avoid high pressure drops, supported zeolites are needed. In this work, two coating methods (dip-coating and in situ crystallization) are optimized to prepare BETA zeolite thin films supported on honeycomb monoliths with tunable properties. The important effect of the density of the thin film in the final performance as a HC trap is demonstrated. A highly effective HC trap is prepared showing 100 % toluene retention, accomplishing the desired performance as a HC trap, desorbing propene at temperatures close to 300 °C, and remaining stable after cycling. The use of this material before the TWC is very promising, and works towards achieving the sustainability and environmental protection goals.

Spectrally tunable light source based on light-emitting diodes for custom lighting solutions

This study describes a novel spectral LED-based tunable light source used for customized lighting solutions, especially for the reconstruction of CIE (Commission Internationale de l’Éclairage) standard illuminants. The light source comprises 31 spectral bands ranging from 400 to 700 nm, an integrating cube and a control board with a 16-bit resolution. A minimization algorithm to calculate the weighting values for each channel was applied to reproduce illuminants with precision. The differences in spectral fitting and colorimetric parameters showed that the reconstructed spectra were comparable to the standard, especially for the D65, D50, A and E illuminants. Accurate results were also obtained for illuminants with narrow peaks such as fluorescents (F2 and F11) and a high-pressure sodium lamp (HP1). In conclusion, the developed spectral LED-based light source and the minimization algorithm are able to reproduce any CIE standard illuminants with a high spectral and colorimetric accuracy able to advance available custom lighting systems useful in the industry and other fields such as museum lighting.

Mesostructured zeolites: bridging the gap between zeolites and MCM-41

Surfactant-templating is one of the most versatile and useful techniques to implement mesoporous systems into solid materials. Various strategies based on various interactions between surfactants and solid precursors have been explored to produce new structures. Zeolites are invaluable as size- and shape-selective solid acid catalysts. Nevertheless, their micropores impose limitations on the mass transport of bulky feed and/or product molecules. Many studies have attempted to address this by utilizing surfactant-assisting technology to alleviate the diffusion constraints. However, most efforts have failed due to micro/mesopore phase separation. Recently, a new technique combining the uses of cationic surfactants and mild basic solutions was introduced to synthesise mesostructured zeolites. These materials sustain the unique characteristics of zeolites (i.e., strong acidity, crystallinity, microporosity, and hydrothermal stability), including tunable mesopore sizes and degrees of mesoporosity. The mesostructured zeolites are now commercially available through Rive Technology, and show superior performance in VGO cracking. This feature article provides an overview of recent explorations in the introduction of mesoporosity into zeolites using surfactant-templating techniques. Various porous materials, preparation methods, physical and catalytic properties of mesostructured zeolites will be discussed.

Paving the way for methane hydrate formation on metal–organic frameworks (MOFs)

The presence of a highly tunable porous structure and surface chemistry makes metal–organic framework (MOF) materials excellent candidates for artificial methane hydrate formation under mild temperature and pressure conditions (2 °C and 3–5 MPa). Experimental results using MOFs with a different pore structure and chemical nature (MIL-100 (Fe) and ZIF-8) clearly show that the water–framework interactions play a crucial role in defining the extent and nature of the gas hydrates formed. Whereas the hydrophobic MOF promotes methane hydrate formation with a high yield, the hydrophilic one does not. The formation of these methane hydrates on MOFs has been identified for the first time using inelastic neutron scattering (INS) and synchrotron X-ray powder diffraction (SXRPD). The results described in this work pave the way towards the design of new MOF structures able to promote artificial methane hydrate formation upon request (confined or non-confined) and under milder conditions than in nature.