Microwave-Assisted Nonaqueous Sol−Gel Chemistry for Highly Concentrated ZnO-Based Magnetic Semiconductor Nanocrystals

Abstract

Various transition metal (TM) doped zinc oxide nanoparticles with the composition TM x Zn 1-x O (TM = V, Mn, Fe, Co, and Ni; x = 0.01-0.3) were prepared by a microwaveassisted nonaqueous sol-gel route in benzyl alcohol within a few minutes. The high doping levels in the range 20-30 atom % achieved for Co and Fe provide a promising opportunity to study the magnetic properties of such potential diluted magnetic semiconductors. However, only Fe 0.2 Zn 0.8 O was ferromagnetic at room temperature. The Co-doped sample showed Curie-Weiss behavior up to a doping level of 30 atom %. According to X-ray absorption fine structure (XAFS) measurements, at high doping levels the Fe-doped ZnO samples contain an increasing fraction of Fe 3þ ions (in addition to Fe 2þ ), whereas Co is predominantly in the oxidation state of þ2. Clustering of Fe ions into amorphous ferromagnetic Fe 3 O 4 within the ZnO host and the magnetic interactions between the Fe 3 O 4 regions is a possible explanation for the ferromagnetic properties.

Polyol synthesized aluminum doped zinc oxide nanoparticles - influence of the hydration ratio on crystal growth, dopant incorporation and electrical properties

“…plane. The incorporation of dopant atoms generally hinders the particle growth and decrease the crystallinity [21,22] but here we can show that an increase of the water content reduces the influence of the dopant on the crystal-growth, so that rod-shaped AZO particles with improved crystallinity can be synthesized.…”

“…For all 27 Al-NMR spectra Al6 is the dominating species whereas the other Al species can be recognized as well. It is obvious that the peaks for Al6, Al5 and Al4 int are very broad in contrast to Al4 sub what indicates that Al4 sub is located in a highly ordered, crystalline environment and Al6, Al5 and Al4 int in a disordered, amorphous environment [20][21][22]. A change of the peak intensities in dependence of the hydration ratio is noticeable.…”

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

“…The microwave assisted benzyl alcohol route has also been employed for the preparation of ZnO doped with variety of metals, such as Co, Ni, Fe, Mn, and V [151]. ZnO-based magnetic semiconductor nanocrystals with high concentrations of dopants were synthesized by this method.…”

Fast, microwave-assisted synthesis of monodisperse HfO2 nanoparticles

“…Microwaves couple directly to the molecules in the reaction mixture, resulting in a more efficient energy transfer and an often significant enhancement of the reaction rate (Kappe and Stadler 2005;Gabriel et al 1998;. Metal oxide nanoparticle synthesis in a microwave is already reported (Baghbanzadeh et al 2011;Bilecka et al 2011;Bilecka et al 2008) but to the best of our knowledge no literature is available for HfO2 nanoparticles. We also investigated the reaction mechanism in both the autoclave and the microwave reaction.…”