The Research Energy In Transfer And Photocatalysis Of Rare Earth Ions For ZnO Nanoparticles

As the third-generation broadband popular semiconductor material,ZnO has been widely concerned by researchers for its simple preparation process,particularly the complex energy band structure of ZnO which is commonly used for constructing material systems with excellent photocatalytic properties.In this paper,ZnO:Eu³⁺and ZnO:Tb³⁺nanomaterials were prepared,analyzed for their morphology,composition and crystal structure,and the lattice defects in ZnO-doped nanomaterials were obtained by spectroscopic analysis.These lattice defects are caused by the charge imbalance doping of rare earth ions.The crystal defects form defective energy levels in the band gap of ZnO,and through energy transfer and electron transfer,the defective energy levels can capture electrons,thus achieving the separation of ZnO conduction band electrons from valence band holes,which contributes to the improvement of photocatalytic performance of rare-earth-doped nanomaterials.It is confirmed that both rare-earth-doped ZnO nanomaterials have relatively good photocatalytic performance.（1）Synthesized ZnO:Eu³⁺nanomaterials by chemical precipitation method.The microstructure and spectral properties of ZnO crystals were analyzed by varying the annealing temperature and Eu³⁺doping ratio,and the results showed that in the ZnO:Eu nanomaterials,the intrinsic defect O_i of ZnO plays a bridging role in the energy transfer with Eu³⁺,after the free electrons are excited to the ZnO conduction band and some electrons relax to the Oi defect energy level,the energy carried by the electrons is absorbed by the neighboring Eu³⁺,a charge transfer from ZnO to Eu³⁺occurs,which promotes the red emission of Eu³⁺.At the same time,once the trivalent Eu³⁺ions enter the ZnO lattice composed of divalent Zn²⁺,lattice defects such as O_i are inevitably generated in the ZnO lattice due to charge imbalance.These defects produce defective energy levels in the band gap of ZnO,which are capable of trapping electrons,thus promoting the charge separation of conduction band electrons from valence band holes and effectively promoting the photocatalytic performance of ZnO-based materials,and it is found that the rare earth-doped ZnO samples have good catalytic degradation efficiency for RhB.（2）Synthesis of ZnO:Tb³⁺nanomaterials was carried out by the solvothermal method.The microstructure and spectral properties of ZnO crystals were analyzed by varying the annealing temperature and Tb³⁺doping ratio,and the results showed that in ZnO:Tb³⁺nanomaterials,both Zn_i and V_O,the intrinsic defects of ZnO,are involved in the energy transfer between ZnO and Tb³⁺.After free electrons are excited to the ZnO conduction band and some electrons relax to the Zn_i and V_O defect energy levels,the energy carried by the electrons is absorbed by the neighboring Tb³⁺and the charge transfer from ZnO to Tb³⁺occurs,thus promoting the green emission of Tb³⁺.Meanwhile,when the trivalent Tb³⁺ions enter the ZnO lattice composed of divalent Zn²⁺,lattice defects such as Zn_i and V_O are inevitably generated in the ZnO lattice due to charge imbalance.These defects produce defective energy levels in the band gap of ZnO,which are capable of trapping electrons,thus promoting the charge separation of conduction band electrons from valence band holes and effectively promoting the photocatalytic performance of ZnO-based materials,and it is found that the rare earth-doped ZnO samples have good catalytic degradation efficiency for RhB.Above results explain the mechanism of energy transfer between ZnO and rare-earth ions theoretically,which is beneficial for the theoretical development of rare-earth materials on ZnO matrix for applications in optoelectronics,photocatalysis,bioimaging or fluorescent probes.