Nanophosphor Application Centre, University of Allahabad, Allahabad 211002, India.
J Colloid Interface Sci. 2010 May 15;345(2):149-53. doi: 10.1016/j.jcis.2010.01.050. Epub 2010 Jan 25.
Single-phase ZnO:Co(2+) nanoparticles of mean size 2-8 nm were synthesized by a simple co-precipitation technique. X-ray diffraction analysis reveals that the Co-doped ZnO nanoparticles crystallize in wurtzite structure without any impurity phase. The wurtzite structure (lattice constants) of ZnO nanoparticles decrease slightly with increasing Co doping concentration. Optical absorption spectra show an increase in the band gap with increasing Co content and also give an evidence of the presence of Co(2+) ions at tetrahedral sites of ZnO and substituted for the Zn site with no evidence of metallic Co. Initially these nanoparticles showed strong ferromagnetic behavior at room temperature, however at higher doping percentage of Co(2+), the ferromagnetic behavior was suppressed, and antiferromagnetic nature was enhanced. The enhanced antiferromagnetic interaction between neighboring Co-Co ions suppressed the ferromagnetism at higher doping concentrations of Co(2+). Photoluminescence intensity owing to the vacancies varies with the Co concentration because of the increment of oxygen vacancies.
采用简单的共沉淀法合成了平均粒径为 2-8nm 的单相 ZnO:Co(2+)纳米粒子。X 射线衍射分析表明，Co 掺杂 ZnO 纳米粒子以纤锌矿结构结晶，没有任何杂质相。随着 Co 掺杂浓度的增加，纤锌矿结构（晶格常数）的 ZnO 纳米粒子略有减小。光学吸收光谱表明，随着 Co 含量的增加，带隙增加，并且还证明了 Co(2+)离子存在于 ZnO 的四面体位置，取代了 Zn 位，没有金属 Co 的证据。这些纳米粒子最初在室温下表现出强铁磁行为，然而，随着 Co(2+)掺杂百分比的增加，铁磁行为被抑制，反铁磁性质得到增强。相邻 Co-Co 离子之间增强的反铁磁相互作用抑制了 Co(2+)高掺杂浓度下的铁磁性。由于空位的存在，光致发光强度因 Co 浓度的增加而变化，因为氧空位的增加。
