Polysaccharide Matrix-Induced Room-Temperature Phosphorescence of Organic Small Molecules

Organic materials capable of room-temperature phosphorescence have attracted much attention due to their potentials in the fields of optoelectronics, sensing and imaging.The development of environmentally friendly matrices for inducing room-temperature phosphorescence can provide feasible and sustainable ways for the applications.The present study was designed to achieve matrix-induced room-temperature phosphorescence using polysaccharides as dispersive substrates for organic small molecules.1-Naphthoic acid (NA) and 4,4'-biphenol (BP) were used as the chromophore to generate phosphorescence.NA and BP were doped in sodium carboxymethyl cellulose (CMC-Na), hyaluronic acid (HA) and chitosan, respectively.Room-temperature phosphorescence from NA and BP was observed in those doped polysaccharide films at ambient condition.The phosphorescence quantum yield of NA in the three polysaccharides was estimated to be about 0.03 and the average phosphorescence lifetime of NA in CMC-Na was estimated to be around 600 ms.The average phosphorescence lifetime of NA in HA and chitosan was estimated to be around 650 and 320 ms, respectively.The phosphorescence quantum yield decreased at high doping contents due to intermolecular quenching that may result from excimer formation and triplettriplet annihilation of NA.BP in CMC-Na presented a phosphorescence quantum yield of about 0.05, which did not decrease with the increase of doping concentration, and the phosphorescence lifetime was about 1000 ms.The phosphorescence quantum yield of BP in HA and chitosan is about 0.03 and 0.006, respectively.The average phosphorescence lifetime of BP in HA and chitosan was estimated to be around 740 and 210 ms, respectively.Infrared spectroscopic studies showed that the polysaccharide substrates formed hydrogen bonds with NA and BP chromophores.The combination of hydrogen bond formation between the matrix and the emissive molecules, the rigid environment of the matrix and the protection of the chromphore from ambient oxygen led to the observation of phosphorescence of organic molecules at room-temperature.NA-and BP-doped CMC-Na solutions can be used to prepare room-temperature phosphorescence patterns by inkjet printing, enabling phosphorescence information encryption.This study can provide a new feasible way for the development of environmentally friendly room-temperature phosphorescence materials.