Study On Design,Preparation And Properties Of New Sodium Alginate Based Room Temperature Phosphorescent Materials

With the advantages of long luminescence time and environmental sensitivity,room-temperature phosphorescent materials have an extensive application space in sensing,information and biological applications.Nonetheless,on account of the high cost,biological toxicity and environmental pollution of inorganic phosphorescent materials containing precious metals,organic room temperature phosphorescent materials with advantages of low cost,relatively friendly environment and rich variety have attracted people’s attention.As a natural polymer matrix with good biocompatibility and wide availability,sodium alginate has great potential for phosphorescent application.Many sodium alginate based materials with color adjustable properties have also been developed.Yet,most of these organic phosphorescent materials have a quite short phosphorescent lifetime and have difficulties in making full use of the structure advantage of sodium alginate to enhance phosphorescent performance.To boost the potential of sodium alginate based materials in phosphorescent field,a series of phosphorescent materials with ultralong lifetime up to 2 s are designed through the perfect combination of SA structure and phosphor design.Some materials also exhibit color-adjustable luminescence properties,and some applications are made possible by taking advantage of material properties.With a large number of active o-dihydroxyl active functional groups in sodium alginate,we proposed a B-O covalent strategy to construct water-treatable sodium alginate based ultralong lifetime room temperature phosphorescent materials,which can make full use of the covalent bond between sodium alginate’s o-dihydroxyl group and aromatic boric acid in the alkaline environment to inhibit the non-radiative transition and achieve long-lived luminescence.Compared with traditional doped phosphorescent materials based on hydrogen or ionic bonds with weak interactions,these phosphorescent materials prepared by this method contain covalent bonds with strong interactions,which can inhibit non-radiative transitions more effectively.Different from traditional polymer-based phosphorescent materials,this method has a simpler and faster preparation process.With this preparation strategy,we successfully prepared ultralong lifetime room temperature phosphorescent materials with high luminescence efficiency(maximum phosphorescent quantum yield of 23.22%,maximum phosphorescent lifetime of 5254 ms).In addition,phosphorescence switching or phosphorescence color regulation can be realized by adjusting humidity,chromophores type,excitation wavelength and delay time,etc.Based on the resonance energy transfer mechanism,fluorescence chromophores can be introduced to further control the afterglow color.Sodium alginate based phosphorescent film materials are equally difficult not to be fabricated through this B-O covalent method,as well as the anti-counterfeiting encryption via mold shaping.Due to the shortage of blue luminescent materials with excellent properties in the field of phosphorescence,blue organic room temperature phosphorescence has attracted persistent attention in the field of organic photoelectric application.Aiming at the problem that the high conjugation degree of phosphors will lead to the luminescence redshift and the short phosphorescence lifetime,reasonable design strategies should be explored and summarized to introduce appropriate functional groups and design phosphor structure to adjust energy levels and develop blue room temperature phosphorescence materials with ultralong lifetime.In another work of this paper,by adding phosphors with different aromatic rings/functional groups into sodium alginate matrix and preparing doped films,the influence of these aromatic ring structures/functional groups on the blue luminescence of algine-based phosphorescent materials was investigated.We found that carboxylic acid groups can not only promote intersystem crossing,but also promote blue shift of luminescence in aromatic ring structures with low conjugation,and achieve long lifetime blue phosphorescence in ultraviolet leds.This strategy has successfully achieved ultra-long lifetime room temperature blue phosphorescence in pure organic room temperature phosphorescence materials.It has the advantages of simple preparation process and excellent machinability,and provides a new research design for the development of new blue light materials.