Spin transition nanoparticles made electrochemically

Abstract

Materials displaying novel magnetic ground states signify the most exciting prospects for nanoscopic devices for nanoelectronics and spintronics. Gas-diffusion electrocrystallization is a new method to produce these groundbreaking nanomaterials.

Synthesis of material libraries using gas diffusion electrodes

“…For instance, based on our experiments it is estimated (from the electric charge consumed), that the profuse amount of OH À rapidly produced (e.g., >1300 mol m À3 ), immediately results in a pH as high as 13-14 within the porosity of the cathode. 21 As the hydroxyl ions spread to the bulk electrolyte, systematic pH increases become consistently manifest in the electrolyte bulk (Fig. 2d).…”

“…22 However, at the electrochemical interface where the oxygen reduction reaction occurs, a profuse amount of OH À prevails, resulting in a local pH as high as 14. 21 Thus, the conditions for HO 2 À to be stable are met in the vicinity of the gas-diffusion cathode and throughout the diffusion layer. It is, in fact, this phenomenon that facilitates the onset of hydroxide supersaturation 23 and hence of the reactive precipitation (i.e., crystallization) of the different nanostructures, at the electrochemical interface (Fig.…”

“…The synthesis of nanostructures by GDEx provides very specic supersaturation conditions: (1) short nucleation and growth periods, (2) at high rates, and (3) avoiding the immediate agglomeration of the nanostructures formed. 21 The owing conditions impose only a temporary contact of metal ion precursors with the reactive species at the saturated electrochemical interface-rendering transient nucleation conditions. The possibilities of growth are feeble, as encountering other metal ions is restricted by their high dilution.…”

Arsenic immobilization as crystalline scorodite by gas-diffusion electrocrystallization

“…However, no one has investigated the immobilization of arsenic, even less so as crystalline scorodite, under cathodic conditions let alone using gas-diffusion electrodes. Therefore, our first aim was to demonstrate the gas-diffusion electrocrystallization (GDEx) process 19,20 as an alternative to remove arsenic from solution, preferably forming scorodite without the use of any primary minerals or seed crystals.…”

“…Concisely, the GDEx process produces reactive intermediates that precipitate metal ions in solution, resulting from the oxygen reduction reaction (ORR) at a gasdiffusion cathode. 19 Within this embodiment, GDEx has been described as a flexible and robust platform to synthesize numerous types of nanoparticles, including iron oxide nanoparticles 19 and spin transition nanoparticles, 20 as well as libraries of nanostructures. 21 Yet, it can also be employed for the recovery of metals and metalloids, often as functional materials.…”