Synthesis Of LaPO₄: Eu Fluorescent Nanoparticles And Its Application In Biological Analysis

In recent years, the use of biological labeling agents has greatly assisted the studies in the field of biology. Conventional biological labeling agents such as organic dyes and nano-gold have several limitations caused by their intrinsic properties, such as broad emission profiles, poor photochemical stability, intermittent emission, and cytotoxicity etc. Considering attractive optical and chemical features of Rare-earth fluorescent nanoparticles, such as low toxicity, large effective Stokes shifts, high fluorescence emission intensity and stability, narrow half emission peaks, long fluorescence lifetime as well as high resistance to photobleaching, blinking, and photochemical degradation, they were proposed to be a promising new class of biological labeling agents, which have the potentiality and ability to overcome a number of problems associated with the commonly used biological labeling agents, such as they could improve the detection sensitivity of biological molecules.Here, the LaPO4:Eu fluorescent nanoparticles were synthesized by hydrothermal method. The results showed that the best conditions to synthesize LaPO4:Eu nanoparticles were as follows:the reactants reacted at 130℃for 120 minutes; the ratio of Rare-earth ions, sodium citrate and sodium phosphate was 5:6.5:4; initial concentrations of the reactants were 0.1mol·L-1; pH values of reactive solution were 11.0; the molar percentage of europium ion doping concentrations was 30%. The fluorescence life of LaPO4:Eu nanoparticles was 1.96ms with good crystallization and monodispersion.The as-prepared oparticles were charactered. The results of XRD test showed that particles were LaPO4:Eu Crystal and belong to the hexagonal system. TEM tests showed that the crystallization was good and the average particle size was 37.3 nm through the particle size distribution experiment. IR experiment showed the LaPO4:Eu were wraped by citrate. The LaPO4:Eu nanoparticles can couple with BSA by covalence interaction, and the optimized experimental conditions were obtained. In solid-phase state, the flourescenc intensity of the LaPO4:Eu-BSA complex was proportional to the concentration of BSA, The linear equation was I=50.33c+160.0, with the correlation coefficient of 0.9855. Hereby, determination of BSA can be done.In the phosphate-buffered solution of pH 7.4, the LaPO4:Eu nanoparticles can label avidin by electrostatic interaction successfully. Moreover, avidin still kept their activity so that they reacted with D-biotin specifically. Using filter membrane as carrier, the fluorescence intensity of labled avidin-biotin was proportional to the concentration of the avidin in a certain range. The linear equation was I=715.26c+160.08, with the correlation coefficient of 0.9948. The experimental results showed that the synthesized LaPO4:Eu nanoparticles can be used as a common fluorescent markers for the detection of biological molecules.