Semiconductor-metal core-shell nanostructures by colloidal heterocoagulation in aqueous medium

Abstract

In contrast to complex syntheses for the preparation of colloidal nanocomposites in a core-shell structure proposed in the literature, we present herein a facile colloidal route based on a heterocoagulation process promoted by the electrostatic interaction among ceramic NiO nanoplatelets and metallic Ni nanoparticles (NPs). Before the heterocoagulation process, NiO and Ni were synthetized separately in presence of ultrasound, by chemical precipitation and chemical reduction of the same nickel precursor, respectively. After that, NiO-Ni core-shell nanostructures were prepared forcing the electrostatic interaction among surfaces in aqueous medium. The surface charge balances of both types of particles were tuned effectively by adjusting the pH in a free-additives suspension. For the surface modification of NiO by Ni, the ceramic suspensions maintain a positive zeta potential at pH 9, while the surface of metallic particles is negatively charged. Then the uniform coating of NiO platelets, by the electrostatically induced coagulation with Ni NPs, was favors. The degree of coverage and the formation of NiO-Ni core-shell nanostructures were followed referring the evolution of zeta potential with the geometric calculation in terms of size and morphology of both nanoparticles, and then corroborated by field emission scanning electron microscopy (FESEM).

Electrophoretic deposition of RGO-NiO core-shell nanostructures driven by heterocoagulation method with high electrochemical performance

“…The synthesis was made by mixing 8 mmol of nickel nitrate hexahydrated (Ni(NO 3 ) 2 , 99.9% purity; Panreac, Spain), and 40 mmol of ammonia (NH 3 , 28%, Panreac, Spain) in a total volume of 80 ml of aqueous solution. This procedure was previously described more in detail elsewhere [10,31,35].…”

In Situ Synthesis and Electrophoretic Deposition of NiO/Ni Core-Shell Nanoparticles and Its Application as Pseudocapacitor

“…In this way, a 0.5 NiO/Ni molar ratio was formulated in the suspension, considering a 100% synthesis reaction yield. Based on previous results [21], this NiO/Ni ratio will allow the completely covering of NiO platelets by Ni nanoparticles. On the other hand, one mixture 1 M in Potassium Hydroxide (KOH, Panreac, Madrid, Spain) and 3.9 M in monohydrate Hydrazine was prepared using deionized water (solution B).…”

“…The molar ratio of the reactants was [Ni +2 ]: [KOH]:[N 2 H 4 ], 1:10:39. This ratio was optimized in a previous work by Miguel et al [21].…”

“…In relation to the engineering viability study, EPD processing is the most reasonable option to use to shape pseudocapacitor electrodes. Many examples of this method has already been studied in previous works [6,10,[20][21][22][23] with the purpose of modify the surface of the final coating.…”

“…In one of our previous work we prepared core-shell nanostructures made on metallic nanoparticles covering the oxide nanoplatelets following an heterocoagulation process [21]. Wen et al have been developed an eruption combustion synthesis enhanced properties for dye-absorption and Li-storage [26].…”