Study On The Photocatalytic Ability Of Lithium Niobate

Lithium niobate?LiNbO₃,LN?is one of the most widely investigated materials because of its excellent piezoelectric,pyroelectric,and nonlinear optical properties.As far as the potential applications of LN nanoparticles?Nps?,the cell biolabeling for multiphoton microscopy,optoelectronic tweezers for handling small population of cells and the high antimicrobial activity for solution pollution control,quickly attracted the attention of researchers.The photocatalytic activity of LN is one useful integratable function of LN-based lab-on-chip platform for unraveling the biological complexity in population through degradation of the cells.However,the photocatalytic activity of LN still lacks investigation so far.In this paper,the photocatalytic activity of LN with different doping impurities is detailed investigations.Firstly,in this paper,Fe-Mn-codoped LiNbO₃ nanoparticles were prepared by a soft-chemistry route.The nanoparticle absorption in UV-Vis range was modified through photochromic effect,and their influence on the photocatalytic activity of the nanoparticles was evaluated by the degradation of rhodamine b under xenon lamp illumination.It was found that Fe-Mn-codoped LiNbO₃ nanocrystals with less Vis absorption exhibited higher photocatalytic efficiency for photocatalytic dye solution.The mechanism of tuning the photocatalytic activity through photochromic effect was proposed for Fe-Mn-codoped LiNbO₃ nanocrystals and the holes released through charge transfer from Mn³⁺are emphasized for the explanation of the photocatalytic behavior.Secondly,in this study,Mg-doped LiNbO₃ nanoparticles are prepared and their photocatalytic ability is studied for organic degradation application.It is found that their photocatalytic ability shows a pronounced dependence on the Mg-doping levels,and in particular an unusual threshold effect exists at the 2-mol%-doping level.Moreover,X-ray diffraction?XRD?,SEM,and differential scanning calorimetry?DSC?analyses show that the similar threshold effect also exists in the Mg-doping dependences of the crystalline anisotropy,morphology,and endothermic behavior of these LiNbO₃ nanoparticles.The relevance between the basic properties and the photocatalytic activity of the LiNbO₃ nanoparticles is discussed,and their Mg-doping dependences are finally connected with the(Nb_Li)⁴⁺and(Mg_Nb)^3–defects in the lattice.Finally,a real-time testing system of photodegradation,measuring the small fluctuations of absorption in open environment by using the theory of phase locked anti-interference,is designed and developed.This system is different from traditional measurement methods for non-repeated sampling,so it can perform degradation test for a small amount of biological fluids near surface of the film and block,and characterize the degradation performance accurately in real time.Using the real-time testing system,the photocatalytic activity of the LiNbO₃ thin film and bulk crystal is studied.