Zr⁴⁺/Be²⁺-doped Nanoparticles:Morphology Control,Upconversion Luminescence And Photoelectric Properties

Rare earth up-conversion nanoparticles have been widely used in medical imaging,bio-marker,anti-counterfeiting,etc.,mainly because of the following advantages:1)The morphology and size can be controlled by changing the reaction conditions,so as to satisfy the application requirements in various fields;2)Enhancement of fluorescence intensity can be achieved by means of matrix structure regulation,ions doping,the control of morphology and size.In this paper,a series of upconversion nanomaterials doped with ions are synthesized for the first time through a facile hydrothermal route.X-ray power diffraction analysis?XRD?,transmission electron microscopy?TEM?,field emission-scanning electron microscopy observations?SEM?,photoluminescence spectra?PL?,scanning Kelvin probe microscope?SKPM?and electrochemical workstation are used to explore the effect of doping ions on luminescence and photoelectric property.Moreover,the possible formation process and reaction mechanism for the obtained nanoparticles with various phases and morphologies is investigated and discussed systematically through time-dependent experiments.The main research contents are as follows:1.NaGd_0.78-xZr_xF₄:Yb³⁺,Er³⁺upconversion nanoparticles?UCNPs?are synthesized for the first time,and the shape of nanoparticles are hexagonal prisms with a smooth surface,uniform particle size,good dispersion,and no reunion phenomenon.We investigated the effect of doped ions on photoluminescence propreties and lattice structure,and we also measured the photoelectric current and surface potential of NaGd_0.78-xZr_xF₄:Yb³⁺,Er³⁺under the IR excitation to investigate the photoelectric properties.At the same time,we synthesized NaY_0.78-xZr_xF₄:Yb³⁺,Tm³⁺UCNPs and analysed the fluorescence properties and photoelectric properties through the same characterization in order to contrast the doping effect.2.We synthesized a series of nanoparticles under different reaction time in order to understand the shape growth process straightforwardly.The proposed mechanism of phase evolution and UC emission enhancement is investigated and discussed systematically.Through the comparison experiments,the effects of some experimental conditions and additives on the morphology of the up-conversion materials were explored.3.NaGd_0.78-xBe_xF₄:Yb³⁺,Er³⁺and NaY_0.78-xBe_xF₄:Yb³⁺,Tm³⁺nanoparticles are synthesized for the first time,and the shape of nanoparticles are hexagonal prisms with a smooth surface,uniform particle size,good dispersion,and no reunion phenomenon.We investigated the effect of doped ions on lattice structure.Since the doping of ions leads to a change in lattice symmetry,the fluorescence is enhanced,but the enhancement effect is not as good as the Zr⁴⁺doping effect.The results show that Zr⁴⁺and Be²⁺doping do not effect the morphology and size of the upconversion materials,but the doping of Zr⁴⁺and Be²⁺changes the lattice symmetry,so that the fluorescence intensity of the nanocomposites increases with the doping ion concentration.Moreover,the photoelectric current and surface potential of NaGd_0.78-xZr_xF₄:Yb³⁺,Er³⁺UCNPs was tested by SKPM and electrochemical workstation under the IR excitation.