Pollutant emissions during pyrolysis and combustion of waste printed circuit boards, before and after metal removal

The constant increase in the production of electronic devices implies the need for an appropriate management of a growing number of waste electrical and electronic equipment. Thermal treatments represent an interesting alternative to recycle this kind of waste, but particular attention has to be paid to the potential emissions of toxic by-products. In this study, the emissions from thermal degradation of printed circuit boards (with and without metals) have been studied using a laboratory scale reactor, under oxidizing and inert atmosphere at 600 and 850 °C. Apart from carbon oxides, HBr was the main decomposition product, followed by high amounts of methane, ethylene, propylene, phenol and benzene. The maximum formation of PAHs was found in pyrolysis at 850 °C, naphthalene being the most abundant. High levels of 2-, 4-, 2,4-, 2,6- and 2,4,6-bromophenols were found, especially at 600 °C. Emissions of PCDD/Fs and dioxin-like PCBs were quite low and much lower than that of PBDD/Fs, due to the higher bromine content of the samples. Combustion at 600 °C was the run with the highest PBDD/F formation: the total content of eleven 2,3,7,8-substituted congeners (tetra- through heptaBDD/Fs) was 7240 and 3250 ng WHO2005-TEQ/kg sample, corresponding to the sample with and without metals, respectively.

Giant magnetoresistance in ultrasmall graphene based devices

By computing spin-polarized electronic transport across a finite zigzag graphene ribbon bridging two metallic graphene electrodes, we demonstrate, as a proof of principle, that devices featuring 100% magnetoresistance can be built entirely out of carbon. In the ground state a short zigzag ribbon is an antiferromagnetic insulator which, when connecting two metallic electrodes, acts as a tunnel barrier that suppresses the conductance. The application of a magnetic field makes the ribbon ferromagnetic and conductive, increasing dramatically the current between electrodes. We predict large magnetoresistance in this system at liquid nitrogen temperature and 10 T or at liquid helium temperature and 300 G.

Influence of alkylphosphonic acid grafting on the electronic and magnetic properties of La2/3Sr1/3MnO3 surfaces

Self-assembled monolayers (SAMs) are highly promising materials for molecular engineering of electronic and spintronics devices thanks to their surface functionalization properties. In this direction, alkylphosphonic acids have been used to functionalize the most common ferromagnetic electrode in organic spintronics: La2/3Sr1/3MnO3 (LSMO). However, a study on the influence of SAMs grafting on LSMO electronic and magnetic properties is still missing. In this letter, we probe the influence of alkylphosphonic acids-based SAMs on the electronic and magnetic properties of the LSMO surface using different spectroscopies. We observe by X-ray photoemission and X-ray absorption that the grafting of the molecules on the LSMO surface induces a reduction of the Mn oxidation state. Ultraviolet photoelectron spectroscopy measurements also show that the LSMO work function can be modified by surface dipoles opening the door to both tune the charge and spin injection efficiencies in organic devices such as organic light-emitting diodes.