Preparation And Luminescence Properties Of Novel Upconversion Nanomaterials And Their Application In Biological Detection

Upconversion nanoparticles have attracted wide attention because of their advantages such as large anti-Stokes shift,low potential biological toxicity,high chemical stability,little light damage to biological tissue,no autofluorescence interference and so on.However,there are still many problems in the upconversion nanomaterials,such as low intensity and overheating effect.In order to solve the problems,we take upconversion nanoparticles(UCNPs)as the main research object,focus on the synthesis of nanocrystals and their applications in the field of luminescence.The main contents are summarized as follows:the first chapter introduces the background of upconversion nanomaterials,including synthesis methods,surface modification and theirs application.In the second chapter,Na Yb_0.5Nd_0.5F₄@Na Yb_0.5Gd_0.49Tm_0.01F₄@Na Gd F₄ core-shell structure upconversion nanoparticles with high luminous properties were synthesized by coprecipitation method with rare earth acetate,oleic acid and octadecene,and modified with PAA ligands to detect copper ions in aqueous system.The third chapter mainly deals with the hydrothermal synthesis of orthorhombic KYb₂F₇:Er³⁺energy clusters,and studies the effects of the amount of KF,hydrothermal reaction time,different kinds of metal ions doped into KYb₂F₇:Er³⁺system and studied theirs effects on crystal phase and luminescence.In the fourth chapter,Na YF₄:Yb³⁺/Er³⁺UCNPs was synthesized by coprecipitation method as a luminescent carrier to explore the synthesis process of molecular imprinting.Main research contents and conclusions:(1)Core-shell structure Na Yb_0.5Nd_0.5F₄@Na Yb_0.5Gd_0.49Tm_0.01F₄@Na Gd F₄UCNPs,was prepared by coprecipitation method,and the dual-wavelength excitation upconversion emission of 980 nm and 808 nm was realized.At the same time,the surface ligands of upconversion nanoparticles were functionalized,and a new ligand polyacrylic acid(PAA)was added to study the energy transfer process of luminescence quenching after chelation of copper ions with PAA,so as to realize the detection of copper ions in aqueous phase.Finally,it is found that the detection limit of the detector is 0.1?M,and the fluorescence intensity quenching shows a linear response when the copper ion concentration is between 0.125?M to 2?M,which can be used for quantitative detection of copper ions.In addition,the detector shows high selectivity for copper ion in competitive experiments.(2)Orthorhombic KYb₂F₇:Er³⁺energy clusters with high luminescent properties were synthesized by hydrothermal method.The effects of reaction time,the amount of potassium fluoride and the doping of other non-luminescent cations(Ca²⁺,Y³⁺,Nd³⁺,Ti⁴⁺,Ge⁴⁺,Si⁴⁺)on the crystal phase and luminescence were studied systematically.It is found that when the temperature is 220?,the reaction time is 30 h and the dosage of potassium fluoride is 8mmol,the orthorhombic KYb₂F₇:Er³⁺energy cluster has the strongest intensity under the condition of Teflon autoclave stirring.When different kinds of ions(Ca²⁺,Y³⁺,Nd³⁺,Ti⁴⁺,Ge⁴⁺,Si⁴⁺)are doped into KYb₂F₇:Er³⁺energy clusters,the crystal phase does not change,but the luminescence intensity decreases slightly.However,the doping of Y³⁺enhances the luminescence of nanocrystals.In addition,the effect of temperature on the thermal coupling energy level of Yb³⁺and Er³⁺co-doped ion pairs is also studied.The absolute sensitivity Sa of KYb₂F₇:Er³⁺UCNPs reaches its maximum at 513 K,which is 0.0022 K^-1.The maximum relative sensitivity Sr is 0.018 K^-1 at 233 K,indicating that the nanocrystalline is a promising material for optical temperature measurement.(3)Na YF₄:Yb³⁺/Er³⁺UCNPs with high luminescence properties were synthesized by coprecipitation method as luminescent carriers,and their surfaces were modified by Si O₂ to explore the process of synthesizing molecularly imprinted layer.The results show that the molecularly imprinted layer without target molecules can be successfully coated by basic characterization.However,after adding the target molecule peimine,the fluorescence spectrum of the nanocrystals did not change before and after washing,so it can be inferred that the target molecule is not connected in the molecular imprinting layer,so there is no process of energy transfer with the nanocrystals.As a result,peimine can not be specifically recognized.