Electrostatic Control of the Thermoelectric Figure of Merit in Ion-Gated Nanotransistors

Semiconductor nanostructures have raised much hope for the implementation of high-performance thermoelectric generators. Indeed, they are expected to make available reduced thermal conductivity without a heavy trade-off on electrical conductivity, a key requirement to optimize the thermoelectric figure of merit. Here, a novel nanodevice architecture is presented in which ionic liquids are employed as thermally-insulating gate dielectrics. These devices allow the field-effect control of electrical transport in suspended semiconducting nanowires in which thermal conductivity can be simultaneously measured using an all-electrical setup. The resulting experimental data on electrical and thermal transport properties taken on individual nanodevices can be combined to extract ZT, guide device optimization and dynamical tuning of the thermoelectric properties

A Novel Tripodal Ligand with Organosulfur Alligator Clips for Deposition of Tetrairon(III) Single Molecule Magnets on Gold

A propeller-like tetrairon(III) complex functionalized with two 1,2-dithiolan-3-yl groups was synthesized and magnetically characterized. The compound has formula [Fe4(thioctic)2(dpm)6] and was specifically designed to be grafted on gold surfaces. It was prepared by reacting [Fe4(OMe)6(dpm)6] (Hdpm = dipivaloylmethane) with a new tripodal ligand, H3thioctic, obtained by esterification of 2,2-bis(hydroxymethyl)-propane-1,3-diol with (±)-alpha-lipoic acid (also known as thioctic acid). Direct current and alternating current magnetic measurements revealed single-molecule magnet behaviour with an effective anisotropy barrier of 14.0(1) K resulting from a high spin (S = 5) ground state and an easy-axis anisotropy

Introduction of Ester and Amino Functions in Tetrairon(III) Single-Molecule Magnets: Synthesis and Physical Characterization.

International audienc

Introduction of Ester and Amido Functions in Tetrairon(III) Single-Molecule Magnets: Synthesis and Physical Characterization

Tetrairon(III) complexes with a propeller-like structure derived from [Fe4(OMe)6(dpm)6] (1) (Hdpm = 2,2,6,6-tetramethylheptane-3,5-dione) are providing a growing class of Single Molecule Magnets (SMMs) displaying unprecedented synthetic flexibility and ease of functionalization. Herein we report the synthesis, crystal structures and magnetic properties of two novel tetrairon(III) SMMs, [Fe4(esterC5)2(dpm)6] (2) and [Fe4(amideC5)2(dpm)6]·Et2O·4MeOH (3·Et2O·4MeOH), in whichfunctionalization of the cluster core is achieved using ester and amido linkages, respectively. To this aim, two new tripodal ligands were prepared by acylation of pentaerythritol (2,2-bis(hydroxymethyl)-propane-1,3-diol) and TRIS (2-amino-2-(hydroxymethyl)propane-1,3-diol), namely H3esterC5 =RC(O)OCH2C(CH2OH)3 and H3amideC5 = RC(O)NHC(CH2OH)3 with R = n-butyl. The compounds were structurally investigated by single-crystal XRD, which demonstrated coordination of the tripodal ligands to the cluster core. The products display SMM behavior with anisotropy barriers Ueff/kB~=11 Kdue to a high-spin (S = 5) ground state and an easy axis anisotropy, described by D = -0.421 cm-1 in 2and -0.414 cm-1 in 3·Et2O·4MeOH. The departure of Ueff from the total splitting of the S = 5 ground multiplet, U/kB~=15 K, has to be ascribed to the sizeable rhombic anisotropy that characterizes the two compounds (E = 0.021 cm-1 in 2 and 0.019 cm-1 in 3·Et2O·4MeOH), as confirmed by master matrixcalculations of the temperature-dependent relaxation time

Ionic Liquids Can Significantly Improve Textile Dyeing: An Innovative Application Assuring Economic and Environmental Benefits

Owing to economic reasons, the textile dyeing industry generally employs traditional and absolutely no-eco-friendly processes: very large quantities of water are indeed required together with a large number of added chemicals which represent dramatic environmental issues. In order to improve the sustainability of the process, we have investigated the dyeing of wool, polyester, and cotton with disperse Red 13 using ionic liquids as the sole additive. The results obtained in isothermal dyeing at 95 C show an outstanding effect of the ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium chloride. This ionic liquid assures efficient dyeing of polyester and wool in open vessels, in the absence of whichever auxiliary agent with total dyebath exhaustion, thus allowing in principle the recycling of the dye bath! The environmental benefits arising from the substitution of a number of usually employed auxiliary agents with only an ionic liquid are highlighted together with the economic ones. This article reports for the first time, to the best of our knowledge, dyeing processes for several kinds of fibers (cotton, wool, and polyester) employing exclusively three components: pure disperse dye, water, and an appropriate ionic liquid. (Figure Presented)

Slow Magnetic Relaxation from Hard-axis Metal Ions in Tetranuclear Single-Molecule Magnets.

International audienc