Synthesis of non-stoichiometric NdxNi1−xOy nanotube arrays and magnetism, upconversion behavior

Non-stoichiometric NdxNi1−xOy nanotube arrays have been fabricated in an anodic alumina membrane (AAM) by filtering at subatmospheric pressure. The images of non-stoichiometric NdxNi1−xOy nanotube arrays and single nanotubes are observed by a scanning electron microscope (SEM) and a transmission electron microscope (TEM), respectively. Selected area electron diffraction (SAED), X-ray diffraction (XRD) and energy dispersive spectra (EDS) are employed to study the morphology and chemical composition of the nanotubes. The hysteresis loops characterized by a vibrating sample magnetometer (VSM) show that the easily magnetized direction of non-stoichiometric NdxNi1−xOy is perpendicular to the nanotube arrays and that these exhibit magnetic anisotropy as a result of the shape's anisotropy. The upconversion of a non-stoichiometric NdxNi1−xOy nanotube is investigated using a HITACHI (F-4500) high-pressure xenon lamp, the results indicate that the blue upconversion emission and the green upconversion emission occur respectively at 480 and 534 nm, excited by 808 nm.