Electrochemical growth of superparamagnetic cobalt clusters

Abstract

The magnetization of stabilized cobalt colloids in tetrahydrofuran has been studied by a superconducting quantum interference device (SQUID) and magnetic balance measurements in dependence of applied magnetic field and temperature. The colloids are generated by a newly developed electrochemical method which allows one to generate clusters containing about 1000 atoms with a narrow size distribution. The final size distribution of the clusters is examined by high resolution transmission electron microscopy and small angle x-ray scattering. The magnetization curves have been determined with special emphasis on changes at the freezing point of the solution. The curves of the liquid phase can be reasonably described by the Langevin function and the magnetic moments of isolated cobalt clusters that have been recently measured by Stern–Gerlach experiments. Deviations that appear at the freezing point can be understood in terms of magnetic anisotropy effects. It is shown that the cluster sizes and the susceptibilities of the dispersions are related. Therefore the growth of the clusters during the electrolysis can be directly observed by measuring the susceptibility in dependence of the charge transport in the cell.

Adjusting the cation and anion nature in ionic liquids used for the growth control of nanoparticles of organic conductors

“…In addition to these chemical reasons, the ILs that we have selected ( Table 1) NPs, the electrode was rapidly passivated by the bulky long chains of (n-Oct)4NBr used as supporting electrolyte [14]. Vigorous stirring is necessary to favor the access of the electroactive species to the electrode.…”

Shape- and size-controlled electrochemical synthesis of cupric oxide nanocrystals

“…A number of metal oxides thin films, including ZnO [21,22], zirconium oxide [23], tungsten oxide [24], bismuth oxide [25], Cu 2 O [26] and CuO [27][28][29], have been synthesized via an electrochemical method. Reetz and co-workers [30][31][32][33] proposed a sacrificial anode electrochemical route to synthesize nanometal clusters. Mahamuni and co-workers further developed Reetz and co-workers' route to prepare ZnO and CuO nanocrystals (powders), using Zn (Cu) as a sacrificial anode in the electrochemical bath comprising of tetraoctylammonium bromide and MeCN-THF mix-solvent (ratio 4:1) [34,35].…”

Recent Advances in Metal Nanoparticles Stabilization into Nanopores of Montmorillonite and Their Catalytic Applications for Fine Chemicals Synthesis

“…Nanostructured colloidal metals require protective agents for stabilization and to prevent agglomeration. The main classes of protective groups are: polymers and block copolymers (152)(153)(154)(155); phosphines, amines, thioethers (156)(157)(158)(159)(160)(161)(162)(163)(164)(165)(166)(167)(168); propylene carbonate (169); long chain alcohols (170)(171)(172)(173)(174)(175)(176)(177)(178)(179)(180)(181)(182); surfactants (156,(183)(184)(185)(186)(187)(188)(189)(190)(191)(192); and organometallics (193).…”