Dielectrophoretic assembly of liquid-phase-exfoliated TiS3 nanoribbons for photodetecting applications

Liquid-phase exfoliation produces colloidal two-dimensional materials that can be assembled by dielectrophoresis to fabricate optoelectronic devices.

On the van der Pauw's method applied to the measurement of low thermal conductivity materials

The electrical van der Pauw's method has recently been extended to measure the thermal conductivity of different elements and compounds. This technique provides an easy way to determine the sample in-plane thermal conductivity by avoiding the influence of the thermal contact resistances. However, the reported calculated error values appear to be underestimated when dealing with the materials with low thermal conductivity (<5 W/Km) at room temperature. The causes of this underestimation are investigated in this communication and it has been found that they are due to the drastic influence of conduction heat losses through the thermo-resistance wires as well as the resulting modification of the sample temperature map. Both phenomena lead to experimental values of the sample thermal conductivity, which are systematically higher than the tabulated ones. The magnitude of this systematic error is ∼100% dealing with the samples of macroscopic dimensions, and low thermal conductivity indicated that the obtained accurate measurements can be quite challenging.

Hydrogen evolution using palladium sulfide (PdS) nanocorals as photoanodes in aqueous solution

Palladium sulfide (PdS) nanostructures are proposed to be used as photoanodes in photoelectrochemical cells (PECs) for hydrogen evolution due to their adequate transport and optical properties shown in previous works. Here, a complete morphological and electrochemical characterization of PdS films has been performed by different techniques. PdS flatband potential (Vfb=-0.65±0.05 V vs NHE) was determined by electrochemical impedance spectroscopy measurements in aqueous Na2SO3 electrolyte, providing a description of the energy levels scheme at the electrolyte-semiconductor interface. This energy levels scheme confirms PdS as a compound able to photogenerate hydrogen in a PEC. At last, photogenerated hydrogen rates are measured continuously by mass spectrometry as a function of the external bias potential under illumination, reaching values up to 4.4 μmolH2/h at 0.3 V vs Ag/AgCl.

Ultrasonic irradiation as a tool to modify the H-desorption from hydrides: MgH(2) suspended in decane

Effects of ultrasonic irradiation on magnesium hydride (MgH(2)) suspended in decane were investigated with the purpose of improving its hydrogen desorption process. Firstly, we have found that the presence of MgH(2) improves the sonolysis of decane enhancing the amount of hydrogen evolved during the sonication process. The sonicated-MgH(2) maintains its microstructural properties practically unaltered but a drastic reduction of the particle size of MgH(2) (down to approximately 20mum) as well as a high pressure MgH(2) phase are observed. However, no substantial modifications of H-kinetic properties of hydride occur as is determined by thermal desorption measurements. This could be attributed to decomposition of decane during sonication which leads to the formation of carbon compounds that hinder the thermal decomposition of MgH(2).