Up-conversion Multicolor Coding Achieved By Sensitizer Doping And Its Applications In Biological Detection

Rare-earth doped upconversion materials can absorb near infrared light and convert it into short-wavelength emission through multi-photon process.The unique luminescence mechanism result in many advantages including larger Stokes shift,low tissue autofluorescence,sharp emission peaks,high investigation depth,and high contrast.In addition,high photochemical stability and low toxicity is well suited for application in many biological fields like,for example,bioimaging,drug delivery,photodynamic therapy,and disease detection.Rare-earth doped up-conversion nanoparticles become the new focus of current research in the field of up-conversion luminescence.However,there are several questions need to be solved:(1)the application in the biological field requires nanocrystals have good biocompatibility and suitable particle size to overcome the steric hindrance of the cells.(2)In order to achieve high throughput and rapid detection,the low cost of the test strategy should be considered.(3)Biologically oriented up-conversion materials are usually specific and only work for single targets,which limits their application in biological detection.In order to explore the use of upconversion luminescence to realize biological detection multicolor coding,we successfully achieved well-crystallized,hexagonal phase,desirable size NaYF4:Yb3+,Er3+ nanocrystals doped with different concentrations of sensitizers Yb3+,the upconversion luminescence characteristics and the luminescent mechanism under different pump power were discuss in detail.In addition,the application of multi-target biological detection was discussed.According to experiment measuring results,the material obtained a good effect in a series of biological tests,which promotes the application potential of up-conversion materials in the field of polychromatic multiplexing.The main results achieved in this paper are as follows:(1)NaYF4:Yb3+,Er3+ upconversion nanocrystals doped with different concentrations of sensitizers were prepared by solvothermal methods with optimized conditions to obtain desirable Morphology and structure.The characterization results show that all the samples are hexagonal phase up-conversion nanoparticles with uniform particle size.Due to Yb3+ ions has smaller surface binding energy in the horizontal direction and larger particle size than Y3+ ions,the crystal grow further as the doping concentration increases.(2)In order to improve the performance of these samples,NaYF4:Yb3+,Tm3+(20%/2%)@NaYF4:Yb3+,Er3+(x%/2%,x=20.30,50.70,and 90)were synthesized by similar method.This method can reduce surface defects effectively and adjust the particle size easily,the effect of particle size on luminescence properties can be avoided conveniently.(3)The luminescent properties and UC mechanism of the material received further discussion and analysis.In this case,the materials with different upconversion red-green ratios were coupled to corresponding bacterial antibodies.Satisfactory results obtained in various biological tests,suggest that the synthesized sample with further modification has great potential for multi-color coding in the field of biological detection.