Controlled Synthesis,Luminescence And Functional Application Of Bismuth Containing Material

Inorganic luminescent materials activated by a small amount of dopants such as rare earth?RE?and transition metal?TM?ions,have achieved novel developments during the past decades.And these materials can be found in many kinds of optical application areas,such as optical amplifiers,fiber lasers and LEDs?light-emitting diodes?.However,these kinds of optical materials have achieved fundamental improvements and novel developments,it's hard to be significantly improved in a short period of time.So,more and more people focus on the luminescent materials of heavier main-group elements.Bismuth,one of p-block elements,is a typical representative of the third type of optical active centers.With respect to Bi-containing luminescent materials,this paper aims to:1)Synthesize stable and highly luminescent bismuth-containing nanoclusters,and study its optical property;2)Prepare a kind of Bi-containing crystalline material,and research the near-infrared?NIR?luminescent property by making detailed analysis of the fine structure.The specific results are as follows.First,we synthesized stable and highly visible-emitting Bi complex nanoclusters?NCs?through a one-pot wet chemical reaction method for the first time.The quantum yield of the sample is as high as 5.9%.Based on the detailed analyses of the structure,we demonstrated a model for the formation of these NCs.At last,we proposed the observed visible luminescence is attributed to the intrinsic electronic transition inherent to the whole NCs.Next,we firstly prepared the Bi-doped NIR-emitting polyoxometallate crystal by utilizing ion-exchange process and subsequent high-temperature annealing under N₂atmospheric conditions.The polyoxometallate crystal as host material has anion([SiW₁₂O₄₀]^4-)vacancies,which are utilized for selective water sorption and exchange of Bi ions.Interestingly,the observed NIR luminescence can be adjusted by changing the concentration of Bi ions and the annealing temperature.Based on the analysis of the structure,we identified that there are three kinds of Cs ions in the precursor and only the one with eight-coordination can be exchanged with Bi ions.The analysis of EXAFS shows Bi ions occupied the off-center position after exchanged with Cs ions.By refining the SXRD data we have confirmed the accurate position of Bi ions in the structure.Based on the combined evidences of optical Characterization and detailed structure analysis,we proposed the occurrence of intriguing NIR luminescence is derived from Bi-related defects formed under annealing,and different defective structures can result in different NIR emission.