Synthesis,Luminescence Modulation And Imaging Of Novel Orthogonal Emission Upconversion Nanoparticals

In recent years,lanthanide ion-doped upconverting nanomaterials?UCNPs?have developed rapidly in the field of life sciences as a new type of inorganic fluorescent nanoparticles.Due to its unique optical properties,it has been widely used in new areas such as real-time detection,super-resolution imaging,optogenetics,etc.In addition,the photonswitchable up-converting fluorescence nanoparticles have attracted more attentions because they can not only achieve biomedical applications,but also exhibit unique value in optical anti-counterfeiting and optogenetics.Therefore,My thesis is mainly focuses on the synthesis and Luminescence Modulation of novel orthogonal emission upconversion nanoparticles,and explores its application in cell imaging.1.Up to now,rare-earth based elements as luminescent centers need to be doped into different shells of the composite structure in order to achieve the orthogonal upconversion emission,As a result,the emission spectrum is not usually pure enough due to the incomplete closure between different emission regions.To address these issues,we have successfully synthesized the"bone-like"orthogonal emission upconversion nanoparticals?NaErF₄:Yb/Tm@NaYF₄:Yb@NaNdF₄:Yb?by a simple thermal decomposition method.With 980 nm continuous laser excitations,it emit red luminescent signals while they emit green signals when exicited by 808nm continuous laser lights.By monitoring the real-time change of the morphology of the nanoparticles,the formation of the"bone-like"morphology is attributed to be the etching effect of the partial crystal faces.In addition,the properties of orthogonal emission are fine tuned by doping different concentrations of Yb³⁺and Tm³⁺in the Core and by designing different intermediate energy transfer layers.Finally,we conclude that the red emisiion of the nanoparticles at 980 nm excitation is due to the Tm³⁺-mediated emission of Er³⁺and the cross-relaxation of heavy doped Er³⁺ions.However,due to the fact that the number of sensitized photons are much fewer at808 nm excitations and the energy transfer pathway is much longer than that of 980excitations,the green emission at 808 nm excitations is mainly caused by the Nd³⁺sensitized energy transfer mechanism.2.On the basis of successful synthesis of a novel orthogonal emission upconversion nanoparticles,RGNPs,another SiO₂ layer is decorated onto surfaces of RGNPs to render them water-soluble and increase their biocompability to achieve the intracellular imaging.Briefly,orthogonal upconversion with core-shell-shell structure is firstly synthesized thermal decomposition method,and then further modified into water-soluble nanoparticals by surface silanization.Secondly,the CCK-8 method is further employed to explore the biocompatibility of the prepared RGNPs@SiO₂ nanoparticles.It shows that the cell survival still exceeds 95%after incubation with 400?g/mL RGNPs@SiO₂ for 24 h,indicating that RGNPs@SiO₂has good biocompatibility.In addition,confocal laser scanning microscopy?CLSM?imaging results show that the RGNPs@SiO₂ nanoparticles have the capabilities of Orthogonal imaging,which can be used as a visual tracking agent with an expectations of be applied to more accurate biological diagnosis.