Lanthanide-doped CaS Photostimulated Luminescence Nanomaterials And Their Optical Properties

Near-infrared?NIR?photostimulated luminescence?PSL?nanocrystals?NCs?have recently evoked considerable interest in the field of biomedicine,but are currently limited by the controlled synthesis of efficient PSL NCs.In this thesis,we report for the first time the controlled synthesis of CaS:Eu²⁺and CaS:Eu²⁺,Sm³⁺NIR PSL NCs through a high?temperature co?precipitation method.The optical properties and the underlying PSL mechanism of CaS:Eu²⁺,Sm³⁺NCs as well as their potential application for bioimaging have been comprehensively surveyed.The main results are as follows:1.High-quality CaS:Eu²⁺and CaS:Eu²⁺,Sm³⁺NCs are synthesized through a high-temperature co?precipitation method.Powder XRD patterns show that all diffraction peaks of the NCs can be well indexed into cubic CaS without any additional impurities.TEM images show that the as-synthesized CaS:Eu²⁺and CaS:Eu²⁺,Sm³⁺NCs are monodispersed and uniform in size distribution.By changing the reaction condition,the size of the NCs can be tuned from 15 nm to 25 nm.2.The role of Sm³⁺co?doping and the effect of thermal annealing on the optical properties of the CaS:Eu²⁺,Sm³⁺NCs as well as the charging and discharging processes and the trap depth distribution are comprehensively surveyed by means of photoluminescence,persistent luminescence,thermoluminescence,and PSL spectroscopies.3.The PSL properties of CaS:Eu²⁺,Sm³⁺NCs are systematically surveyed.The resulting NCs exhibit intense PSL of Eu²⁺at 650 nm with a fast response to stimulation in a broad NIR region from 800 nm to 1600 nm,a duration time longer than 2 h,and an extremely low power density threshold down to 10 mW cm^?22 at 980 nm.4.Furthermore,by taking advantage of the intense NIR PSL,we demonstrate the application of CaS:Eu²⁺,Sm³⁺NCs as sensitive luminescent nanoprobes for biotin receptor?targeted cancer cell imaging.These results reveal the great promise of CaS:Eu²⁺,Sm³⁺nanoprobes for autofluorescence?free bioimaging,and also lay a foundation for future design of efficient NIR PSL nanoprobes towards versatile bioapplications.