Preparation And Properties Of Oxide Based Luminescent Materials For Plant Light Supplement

Among the five elements of plant growth,light is particularly important.It not only provides energy for photosynthesis,but also participates in and influences various growth stages such as flowering and fruiting.Light works on plant growth only if it is absorbed.The light receptors in plants include chlorophyll and carotenoids which are involved in photosynthesis,as well as photosensitive receptors such as phytochrome,cryptochrome and phototropin that affect photomorphogenesis.Chlorophyll mainly absorbs blue and red orange light,carotenoid mainly absorbs blue light,phytochrome absorbs red and deep red light,cryptochrome and phototropin can absorb blue light,but ultraviolet,green and yellow light are rarely absorbed,so the Light Use Efficiency(LUE)in plants is not high.By converting the light that cannot be absorbed by plants in the solar spectrum into red and blue light,which is needed for photosynthesis,the LUE can be improved,thus accelerating plant growth.In view of the difference between the photosynthetic absorption spectra and the emission spectra of the luminescent materials used for plant light supplement,two kinds of oxide based luminescent materials are designed and prepared,their luminescent properties are systematically studied,and biological experiments are conducted on Chlorella.The specific research content and main results are as follows:(1)Two low-cost new hybrid phosphors are designed and prepared by high temperature solid-phase method:Al₂O₃:Cr³⁺/Y₃Al₅O₁₂:Ce³⁺(YAG:Ce³⁺)and Al₂O₃:Cr³⁺/(Ba,Sr)₂Si O₄:Eu²⁺(BOSE:Eu²⁺).It is expected to enhance the excitation intensity of blue light region and the overall emission intensity through photon transfer.The morphology of the sample is observed by scanning electron microscope,and the particle size of the sample is found to be irregular and in the order of?m.The luminescence properties of the samples are investigated by spectral characterization.Under blue excitation,the emission intensity of Al₂O₃:Cr³⁺/YAG:Ce³⁺is the strongest,followed by Al₂O₃:Cr³⁺/BOSE:Eu²⁺,and Al₂O₃:Cr³⁺is the weakest.The Al₂O₃:Cr³⁺/YAG:Ce³⁺sample has an ultra-wide excitation spectrum covering 325-650 nm,the emission peak is located at 696 nm,belonging to deep red light.Its quantum yield and thermal stability are also improved.In order to evaluate the feasibility of the sample as a solar conversion material,the total reflection spectrum of the sample is measured by using xenon lamp to simulate sunlight.In addition,the growth experiment of Chlorella is also carried out.After 7 days,the biomass of Chlorella increases by 9.7%compared with the control group,indicating that the Al₂O₃:Cr³⁺/YAG:Ce³⁺sample could effectively promote the growth of plants under sunlight.(2)Based on Ba₃CaK(PO₄)₃,Ba₃CaK_0.6Rb_0.4(PO₄)₃:Eu²⁺,Mn²⁺(BCKRP:Eu²⁺,Mn²⁺)samples are prepared by partially replacing K⁺with Rb⁺,Eu²⁺as sensitizer and Mn²⁺as activator.The crystal structure of BCKRP is studied,and it is found that there are five cationic sites which can be occupied by Eu²⁺in the structure.Therefore,the emission spectrum can be decomposed into five Gaussian peaks,and the corresponding relationship between the five lattice sites of Eu²⁺and gaussian peaks is analyzed.The spectra of BCKRP:Eu²⁺,Mn²⁺are characterized.The excitation spectra of the samples range from 240 nm to 450 nm,while the emission spectra have two peaks at 460 nm and 620 nm respectively,which are attributed to the 5d?4f transition of Eu²⁺and the~4T₁?~6A₁ transition of Mn²⁺.The variation of emission intensity with temperature is studied.And the results show that the thermal stability of Mn²⁺is ordinary,while the emission intensity of Eu²⁺varies linearly with temperature.The existence of energy transfer caused by dipole-dipole interaction is proved by decay time test.The Eu²⁺and Mn²⁺co-doping results in red and blue double emission of the samples.To verify the promotion effect of the samples on plant growth,chlorella growth experiment is carried out,and the results show that the sample can effectively promote the propagation of chlorella.