Complex‐Surfactant‐Assisted Hydrothermal Route to Ferromagnetic Nickel Nanobelts

Abstract

Nickel is an important ferromagnetic material. Anisotropic magnetic nanoparticles are expected to exhibit interesting magnetic properties.[1] Nickel one-dimensional (1D) nanostructures have thus attracted much attention recently because of their potential applications in magnetic sensors and memory devices.[2] Different Ni 1D nanostructures have been successfully synthesized by various methods. [3±5] Currently, the fabrication of Ni nanowires mainly depends on a template technique that involves electrochemical deposition or metal± organic chemical vapor deposition (CVD) of metals into the nanopores of template materials, such as anodic alumina (AAO) film [3] and carbon nanotubes.[6] However, little work on the preparation of Ni 1D nanostructures in aqueous solution has been reported to date. [7] Such a solution-phase approach may provide a more promising technique for preparing 1D nanostructures than conventional methods in terms of cost and potential for large-scale production.[8] Here we report a complex-surfactant-assisted hydrothermal reduction method to synthesize single-crystal Ni nanobelts with high yield. Ni nanobelts were generated by reducing a Ni II -tartrate complex in alkaline solution and in the presence of a suitable surfactant at relatively low temperature (110 C). These nanobelts had typical widths of 500±1000 nm, a thickness of onlỹ 15 nm, and lengths of up to 50 lm. This new type of nanostructure of a ferromagnetic metal should be explored in physical property studies and for interesting applications as a new kind of nanoblock.Practically, the present approach to the synthesis of Ni nanobelts is similar to the process for electroless Ni plating. [9] In our study, sodium tartrate (Na 2 C 4 H 4 O 6 ) was used as the complexing reagent to form a complex, Ni(C 4 H 2 O 6 ) 2± . The formation of Ni II complex sharply decreased the free Ni 2+ concentration in the solution, which resulted in a relatively slow rate of generation of Ni atoms. A slow reaction rate was favorable for separating the growth step from the nucleation step. For this reason, we selected a high concentration of both tartrate and alkali. Nevertheless, we found that adjusting the concentrations of tartrate and NaOH was not sufficient for the formation of 1D nanostructures. In this case, only spongelike Ni particles were produced. In the solution-phase synthesis of nanocrystals, kinetically controlling the nucleation and growth rate could conceivably modulate the size and shape of the final products.[10] Some recent work has suggested that the shape of the nanocrystals can be effectively modulated by adding chemical capping reagents to the synthetic systems. It is believed that the selective interaction of the capping molecules on a facet of the first-formed nanoparticles is the key to anisotropic growth of nanoparticles. [4,11] In this work, in order to achieve the desired Ni nanobelts, the anion surfactant sodium dodecyl benzenesulfonate (SDBS) was introduced to the synthesis system. We found that SDBS had a remarkable effect o...

Ni/Ni3C Core–Shell Nanochains and Its Magnetic Properties: One-Step Synthesis at Low Temperature

“…4,5 Accordingly, a series of one-dimension (1D) nickel nanostructures including nanotubes, nanowires, nanorods, nanochains and nanoarrays have been synthesized. [6][7][8][9][10][11][12][13] A variety of one-dimensional (1D) core-shell structures were prepared to enhance the multifunctionality of these materials, and they have exhibited good characters in improving luminescent efficiency, magnetic property and as field effect transistors. [14][15][16][17] Many methods of preparation in high temperature, including a laser ablation method, a high-temperature route and a carbothermal reduction method, have been used to synthesize the core-shell nanomaterials.…”

Fabrication and magnetic properties of hierarchical nickel microwires with nanothorns

“…The H c value was also superior to that of the flower-like nanocones, nanospheres, nanowires, and nanoflowers, which was believed to be associated with the unique packing manner of the singly crystalline nanothorns in the hierarchical nanostructures [24,25]. This value, however, was much lower than that of the 1D nanorods (332 Oe) or nanobelts (640 Oe), which might be due to the fact that the assembly configuration as a total exhibits much lower anisotropy than that of isolated 1D nanocrystals [26,27]. When subjected to an external magnetic field, it is difficult for the hierarchical nickel microwires with nanothorns to be aligned simultaneously along the direction of the magnetic field like isolated nanorods or wires.…”

Preparation and growth mechanism of nickel nanowires under applied magnetic field

“…Figure 5 shows that their SEM images and the corresponding schematic reduce the reaction rate. This will improve the oriented growth of the nickel nuclei and form spherical particles [23]. In the second 10 min, the magnetic particles were subjected to magnetization in the magnetic field and aligned linearly by the magnetic force.…”