Sol-Gel Synthesis of Highly Dispersed Cobalt Nanoparticles on Silica Thin Films

Abstract

Cobalt nanoparticles were synthesized on silica thin films by heat treating Co/silica films spun on thermally oxidized Si substrates. The as-deposited films were calcined in vacuum (∼0.03 Torr) for 2 h at 500 °C, followed by reduction in hydrogen at 650 °C for up to 15 h. The reduction process is characterized as one of time-dependent evolution of nanoparticles in both physical appearance and phase nature, eventually leading to the formation of well-dispersed Co nanoparticles, as ascertained by x-ray photoelectron spectroscopy and scanning electron microscopy. Slow conversion of Co ions into metallic Co observed in this study is ascribed to the absence of a Co3O4 phase that forms predominantly during calcination in air. Atomic force microscopy revealed a marked increase in the surface roughness of the film due to the development of nanoparticles. A distinct duplex-layer structure was observed in the reduced film, which consisted of the upper layer laden with nanoparticles and the lower layer essentially particle-free. The growth of the upper layer appears to be controlled by the upward diffusion of Co2+ in the film during the reduction process.

Fabrication and characterization of titania nanotube/cobalt sulfide supercapacitor electrode in various electrolytes

“…The Co 2p spectrum, shown inFigure 5a, contains a main peak located at a binding energy value of 779.8eV and a shake-up feature at higher binding energy. These peaks can be assigned to Co 2+ of CoS phase as supported by the literature[36][37][38][39]. Further, the Co-spectrum can be de-convoluted into couple of more constituent components corresponding to the following chemical states: CoO and Co(OH) 2 .…”

Cathodic deposition of interlaced nanosheet-like cobalt sulfide films for high-performance supercapacitors

“…The electrochemical behavior of the nanosheet CoS electrode was explored by cyclic voltammetry (CV) and galvanostatic charge-discharge tests in 1.0 M KOH aqueous solution using the aforementioned potentiostat. The CV was conducted in a potential interval between 20.2 V and 0.6 V vs. Ag/AgCl at scan rates ranging from 5 mV s 21 to 50 mV s 21 . The galvanostatic charge-discharge tests were performed within a potential range of 20.1 to 0.45 V vs. Ag/AgCl at charge-discharge current densities ranging from 4 to 40 A g 21 .…”

“…2a), the main peak located at the lower binding energy value (779.8 eV) and a shake-up feature at higher binding energies can be assigned to Co 2+ in CoS according to the literature. 10,[19][20][21] Furthermore, Fig. 2b shows that the binding energy value of S 2p in the thin film is around 162 eV, indicating that most of the S species exist as S 22 in the thin film.…”

“…The CoS spheres demonstrated that a specific capacitance of 249 F g 21 can be obtained at a current density of 4 A g 21 , which was 70% of that at 0.5 A g 21 . Yuan et al 13 dispersed amorphous CoS x nanodots onto functionalized multi-walled carbon nanotubes and a specific capacitance of 300 F g 21 was delivered at 3 A g 21 , which still remained 90% of that at 0.4 A g 21 . Hence, cobalt sulfides can be considered as promising electroactive materials for high-performance electrochemical capacitive energy storage applications.…”

Structural and magnetic properties of sputter deposited cobalt–silica nanocomposite thin films

“…The studies on magnetic properties of sputter deposited Co-SiO 2 thin films are limited in the literature [14,15]. However study of Co-SiO 2 system synthesized by other techniques like sol-gel and ion implantation has been done by several authors [6][7][8][16][17][18][19][20][21][22]. Therefore, the present work is focused on to fabricate Co-SiO 2 nanocomposite films by using DC/RF magnetron co-sputtering and investigate the effect of cobalt concentration on their magnetic behavior.…”