采用微乳液水热法制备了NaYF4:Yb3+,Er3+的上转换纳米氟化物,粉末X-射线衍射(XRD)图显示:反应时间在48h以内,NaYF4:Yb3+,Er3+纳米粒子产物并非NaYF4的单一相.水热时间延长到72h时,所得产物与PDF#28-1192相吻合,表明产物转变为单一的β-NaYF4.扫描电镜分析结果表明,NaYF4:Yb3+,Er3+纳米粒子随反应时间增加由立方相过渡为六方相,粒径大约在150-160nm.近红外荧光和上转换荧光光谱研究发现,下转换光谱最强发射峰位于1540 nm(对应于4I13/2—4I15/2);Yb3+(c/mol):Er3+(c/mol)=3∶1时上转换发射中心分别在523nm、538nm和655nm(分别对应2H11/2→4I15/2、4S3/2→4I15/2和4F9/2→I15/2跃迁).通过分析上转换发光机理,发现无论绿光发射还是红光发射均为双光子过程.%The fluoride upconversion material NaYF4: Yb3+, Er3+ was prepared via hydrothermal microemulsion method. The XRD pattern indicated that the product was not pure before 48h. When reaction time was prolonged to 72h the product was pure β-NaYF4. The SEM patterns showed that the nanoparticles were transformed from cubic phase to hexagonal phase with the reaction time increasing. The diameters of the particles are about 150-160nm. It was found that the predominant emission peak of downconversion spectrum located at 1540nm (corresponding to 4I13/2-4I15/2) . In the upconversion spectrum, when Yb3+(c/mol): Er3+(c/mol) = 3: 1, the emission centers were at 523nm、 538nm and 655nm respectively (corresponding to 2H11/2→4I15/2、4S3/2→4I15/2 and 4F9/2→4I15/2 respectively). Meanwhile, upconversion mechanism and process were also analyzed and we found that the red and green emissions were both due to two photons process.
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