Portable single-sided NMR measurements at variable temperatures: Implementation of a thermo-controlled device and application to the heating of bread dough

A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.     

Numerical study of two-airfoil arrangements by a discrete vortex method

Theoretical and Computational Fluid Dynamics - The aerodynamic characteristics of two neighboring airfoils are greatly different from those of a single airfoil, for both attached and detached flow...     

The Reductive Dehydration of Cellulose by Solid/Gas Reaction with TiCl4 at Low Temperature: A Cheap,Simple, and Green Process for Preparing Anatase Nanoplates and TiO2/C Composites

Metal oxides and metal oxide/carbon composites are entering the development of new technologies and should therefore to be prepared by sustainable chemistry processes. Therefore, a new aspect of the reactivity of cellulose is presented through its solid/gas reaction with vapour of titanium(IV) chloride in anhydrous conditions at low temperature (80 °C). This reaction leads to two transformations both for cellulose and titanium(IV) chloride. A reductive dehydration of cellulose is seen at the lowest temperature ever reported and results in the formation of a carbonaceous fibrous solid as the only carbon‐containing product. Simultaneously, the in situ generation of water leads to the formation of titanium dioxide with an unexpected nanoplate morphology (ca. 50 nm thickness) and a high photocatalytic activity. We present the evidence showing the evolution of the cellulose and the TiO₂ nanostructure formation, along with its photocatalytic activity. This low‐temperature process avoids any other reagents and is among the greenest processes for the preparation of anatase and also for TiO₂/carbon composites. The anisotropic morphology of TiO₂ questions the role of the cellulose on the growing process of these nanoparticles.     

Modulation of the Physicochemical Properties of Donor–Spiro–Acceptor Derivatives through Donor Unit Planarisation: Phenylacridine versus Indoloacridine—New Hosts for Green and Blue Phosphorescent Organic Light‐Emitting Diodes (PhOLEDs)

This work reports a detailed structure–property relationship study of a series of efficient host materials based on the donor–spiro–acceptor (D‐spiro‐A) design for green and sky‐blue phosphorescent organic light‐emitting diodes (PhOLEDs). The electronic and physical effects of the indoloacridine (IA) fragment connected through a spiro bridge to different acceptor units, namely, fluorene, dioxothioxanthene or diazafluorene moiety, have been investigated in depth. The resulting host materials have been easily synthesised through short, efficient, low‐cost, and highly adaptable synthetic routes by using common intermediates. The dyes possess a very high triplet energy (E_T) and tuneable HOMO/LUMO levels, depending on the strength of the donor/acceptor combination. The peculiar electrochemical and optical properties of the IA moiety have been investigated though a fine comparison with their phenylacridine counterparts to study the influence of planarisation. Finally, these molecules have been incorporated as hosts in green and sky‐blue PhOLEDs. For the derivative SIA‐TXO₂ as a host, external quantum efficiencies as high as 23 and 14 % have been obtained for green and sky‐blue PhOLEDs, respectively.     

Insights into the Cascade Reaction of CO and Heteroallenes Mediated by Dinitrogen Hafnocene Complexes: The Indirect Effect of Nitride's Nucleophilicity

A DFT mechanistic exploration of the reactivity of the dinitrogen hafnocene complex, [{(η⁵‐C₅H₂‐1,2,4‐Me₃)₂Hf}₂(μ₂‐N₂)], towards mixtures of CO/CO₂ and CO/OCNtBu is reported. The crucial role of the nitride intermediate is highlighted, as well as the importance of the bridging mode of the cyanate ligand between the two Hf metal atoms throughout the process. Interestingly, the CO₂ addition to the nitride intermediate occurs through an outer‐sphere transition state, whereas the addition of the heteroallene is governed by the steric congestion imposed by cyclopentadienyl ligands.     

Ultrasmall Superparamagnetic Iron Oxide Nanoparticles with Europium(III) DO3A as a Bimodal Imaging Probe

A new prototype consisting of ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles decorated with europium(III) ions encapsulated in a DO3A organic scaffold was designed as a platform for further development of bimodal contrast agents for MRI and optical imaging. The USPIO nanoparticles act as negative MRI contrast agents, whereas the europium(III) ion is a luminophore that is suitable for use in optical imaging detection. The functionalized USPIO nanoparticles were characterized by TEM, DLS, XRD, FTIR, and TXRF analysis, and a full investigation of the relaxometric and optical properties was conducted. The typical luminescence emission of europium(III) was observed and the main red emission wavelength was found at 614 nm. The relaxometric study of these ultrasmall nanoparticles showed r₂ values of 114.8 mm ^?1_Fes^?1 at 60 MHz, which is nearly double the r₂ relaxivity of Sinerem^®.