Abstract
Zn0.9Cd0.1S nanoparticles doped with 0.005–0.24 M cobalt have been prepared by co-precipitation technique in ice bath at 280 K. For the cobalt concentration >0.18 M, XRD pattern shows unidentified phases along with Zn0.9Cd0.1S sphalerite phase. For low cobalt concentration (≤0.05 M) particle size, dXRDis ~3.5 nm, while for high cobalt concentration (>0.05 M) particle size decreases abruptly (~2 nm) as detected by XRD. However, TEM analysis shows the similar particle size (~3.5 nm) irrespective of the cobalt concentration. Local strain in the alloyed nanoparticles with cobalt concentration of 0.18 M increases ~46% in comparison to that of 0.05 M. Direct to indirect energy band-gap transition is obtained when cobalt concentration goes beyond 0.05 M. A red shift in energy band gap is also observed for both the cases. Nanoparticles with low cobalt concentrations were found to have paramagnetic nature with no antiferromagnetic coupling. A negative Curie–Weiss temperature of −75 K with antiferromagnetic coupling was obtained for the high cobalt concentration.
Highlights
Semiconductor nanoparticles have generated great fundamental and technical interests due to novel size-tunable properties and, in potential applications as optoelectronic devices and biomedical tags [1,2,3,4,5]
A negative Curie–Weiss temperature of -75 K with antiferromagnetic coupling was obtained for the high cobalt concentration
The introduction of transition metal (TM) into nonmagnetic semiconductors provide another possible way for generation of diluted magnetic semiconductors (DMS) [3, 12]
Summary
Semiconductor nanoparticles have generated great fundamental and technical interests due to novel size-tunable properties and, in potential applications as optoelectronic devices and biomedical tags [1,2,3,4,5]. Recent advances have led to the exploration of tunable optical properties by changing their constituent stoichiometries in mixed ternary nanoparticles [11]. In nanoparticles the systematic tuning of their band gap can be controlled by alloy formation as well as by size variation. Cobalt-doped Zn0.9Cd0.1S alloyed (Zn0.9Cd0.1S: yCo) nanoparticles with different cobalt doping concentrations were prepared by the co-precipitation method. The relationship of physical properties of Zn0.9Cd0.1S: yCo nanoparticles to the doping amount is explored systematically. Cobalt-doped Zn0.9Cd0.1S alloyed nanoparticles were synthesized using the co-precipitation method without capping ligand or surfactant. Magnetic measurements were taken with superconducting quantum interference device (SQUID) magnetometer (QD MPMSXL)
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