Preparation and luminescence performance of rare earth agriculture-used light transformation composites

Rare earth elements (REEs) and their composites could promote the growth of agricultural products, which, hence, have been widely used in farms as an important trace fertilizer, especially in China. In this work, two kinds of rare earth organic complex europium-salicylic acid-[1,10-phenanthroline] (Eu(Sal)₃Phen) and praseodymium-salicylic acid-[1,10-phenanthroline] (Pr(Sal)₃Phen) were synthesized first. Then we prepared the Eu,Pr(Sal)₃Phen/LLDPE composites by adding Eu(Sal)₃Phen and Pr(Sal)₃Phen (with a weight ratio of Eu(Sal)₃Phen: Pr(Sal)₃Phen = 1:1) into the linear low-density polyethylene (LLDPE) matrix by mechanical mixing. The experiments of fluorescent properties showed that the composites can absorb ultraviolet light (UV) (wavelength range of 200–400 nm) and can emit red-orange light (wavelength range of 600–680 nm), which is necessary light source for growth crop. The fluorescent properties of Eu,Pr(Sal)₃Phen treated for different time at 160 °C and treated for 10 min at different temperatures have been tested. It has been found that the fluorescent intensity of the Eu,Pr(Sal)₃Phen reduced with the increase of treated time and treated temperature. Furthermore, the fluorescent properties of Eu,Pr(Sal)₃Phen/LLDPE composites placed at room temperature for different time have been analyzed. It has been proved that the decrease in the fluorescent intensity of the Eu,Pr(Sal)₃Phen/LLDPE composites is not evident within 3 months. Therefore, these composites meet the requirements of growth crop in one quarter, sufficiently.