Abstract
In the experimental work leading to this contribution, the parameters of the ultrasound treatment (temperature, output power, emission periodicity) were varied to learn about the effects of the sonication on the crystallization of Ni nanoparticles during the hydrazine reduction technique. The solids were studied in detail by X-ray diffractometry, dynamic light scattering, thermogravimetry, specific surface area, pore size analysis, temperature-programmed CO2/NH3 desorption and scanning electron microscopy. It was found that the thermal behaviour, specific surface area, total pore volume and the acid-base character of the solids were mainly determined by the amount of the nickel hydroxide residues. The highest total acidity was recorded over the solid under low-power (30 W) continuous ultrasonic treatment. The catalytic behaviour of the nanoparticles was tested in a Suzuki-Miyaura cross-coupling reaction over five samples prepared in the conventional as well as the ultrasonic ways. The ultrasonically prepared catalysts usually performed better, and the highest catalytic activity was measured over the nanoparticles prepared under low-power (30 W) continuous sonication.
Highlights
Nanoparticles (NPs) are commonly defined as solid materials with at least one dimension in the 1–100 nanometer size range including even polycrystalline systems with nano-sized crystallites [1]
In the X-ray diffractograms (Figures S1 and S2, Supporting Information), the three reflections with Bragg indices 111, 200 and 220 can be observed indicating the successive evolution of face-centred cubic structure of Ni crystallites (JCPDS#04-0850) in the ultrasonically-aided syntheses as well as those performed with mechanical stirring or without stirring (Figure S2)
To map the exact effect of the ultrasound treatment at various temperature on the formation of nickel nanoparticles detailed investigations were performed between 5 ◦C and 75 ◦C (Figure 1)
Summary
Nanoparticles (NPs) are commonly defined as solid materials with at least one dimension in the 1–100 nanometer size range including even polycrystalline systems with nano-sized crystallites [1]. The dimensions of the nanoparticles are comparable to those of biological moieties like viruses (20–50 nm), proteins (5–50 nm) or genes (2 nm wide and 10–100 nm long) revealing the potential to tag or address these units with NPs. some nanoparticles are ferromagnetic, and they can be led by an external magnetic field, their utilization in cancer research or in healing processes as targeted drug delivery system is a research field in the lime-light [8,9]. Some nanoparticles are ferromagnetic, and they can be led by an external magnetic field, their utilization in cancer research or in healing processes as targeted drug delivery system is a research field in the lime-light [8,9] Their special and tuneable physicochemical properties are connected to wide range of industrial uses (e.g., nano-carbon: fillers and black pigment, titania nanoparticles: UV protection, whitening pigment and solar cell) [10]. The relatively easy control of shape and size of nanoparticles, the enhanced specific surface area compared to the bulk-phase variants make possible to rationally design the materials for catalytic applications [1,11]
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