Preparation Of Flexible White Organic Fluorescent Nanofibrous Membranes And Study On Its Mechanism

White-light-emitting materials have attracted much attention due to their promising applications,especially in flat panel displays,general solid-state lighting sources and backlights for full-color displays.To achieve white-light emission,the emission spectrum should be wide enough to cover the entire visible region.Thus,it is hard to realize white-light emission for a single fluorescent dye.In recent years,donor-acceptor(D-A)systems have raised much interest because of the high emission efficiency.In most D-A system,if emissive molecules are too close,it is hard to obtain a broad band of emission within the visible spectrum because the energy transfer(ET)from donor to acceptor is too strong.Therefore,how to restrain ET has been proved to be challenging.Isolation of dyes,which can provide an appropriate spatial distribution for desirable ET to emit white light,turns out to be a good way to solve this ET problem.Coaxial electrospinning comes to mind,because it is an easy and efficient method to spatially isolate dyes and the uniform white-light emitting fibrous membrane can be easily achieved.Blue fluorescent dyes 1,8-naphthalic anhydride was chosen as the donor molecule and orange fluorescent dyes PMI prepared by ourselves was used as the acceptor molecule.Using coaxial electrospinning,PMI and 1,8-naphthalic anhydride were doped in the core-shell region of coaxial PLA porous fibers.When the mass ratio of donor-acceptor molecules was 1:1,the fibrous membrane emitted white light and its chromaticity coordinate was(0.26,0.33).The advantage of coaxial structure is that the spatial separation of two dyes can be easily accomplished,which can effectively impede the energy transfer(ET)of two dyes and make every individual fiber under microscopic size emit uniform white light.Compared to the single structure,energy transfer efficiency of donor-acceptor molecules in coaxial structure decreased from 78.43%to 18.06%.Polylactide(PLA)was used as the electrospun matrix due to its well pore-forming performance under humidity condition,and the formed porous structure could reduce the blocking effect of the polymer matrix on the fluorescent dyes effectively and realize white-light emission high-efficiently.Thus the novelty white-light-emitting fibrous membranes have their special performance,such as uniformity,flexibility,portability,tailorability and durability.