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The method to regulate the concentration of graphene oxide (GO) via changing polarity of solution was developed, then the Tb(acac)n(PMA)n/GO composites were synthesized by coordination bond. The tunable photoluminescence property is achieved under different concentration of GO dispersion. The mechanism of tunable luminescence also is elucidated in details. Simultaneously, the strong thermal stability of Tb(acac)n(PMA)n/GO complexes series is performed because of the function of PMA, which suggests potential application in optical fields such as photo-electric device. [ABSTRACT FROM AUTHOR]

NaYF 4 :Yb, Er with nitrogen-doped graphene quantum dots (N-GQDs) mixture was synthesized by a simple one-pot hydrothermal method. The as-obtained mixture shows green color under the irradiation of infrared light (980 nm), and exhibits blue color by means of ultraviolet excitation (365 nm). The luminescence of NaYF 4 :Yb, Er and N-GQDs are not affected by each other. And the synthesized mixture directly incorporated into a polyvinyl alcohol (PVA) matrix can obtain a transparent luminescent film. The luminescent film also shows different luminescent colors under different light irradiation (980 nm or 365 nm). This result indicates that it has a potential application value in anti-counterfeiting packaging. • The NaYF 4 :Yb, Er with N-GQDs mixture was synthesized by a one-pot hydrothermal method. • The obtained material exhibits shows green color under 980 nm and blue color under 365 nm. • A polymer luminescent film was synthesized by self-assembly of the mixture and PVA. • The obtained film has a potential application value in anti-counterfeiting packaging. [ABSTRACT FROM AUTHOR]

• The NaYF 4 :Ln/NaYF 4 :Eu composite possesses up-conversion and down-shifting luminescence properties. • The composite possesses excellent compatibility and fluorescence purity. • They can be prepared into fluorescent patterns and provide a potentiality for anti-counterfeiting. Herein, a series of novel dual-mode NaYF 4 :Ln/NaYF 4 :Eu (Ln = Yb, Er, Tm) composites involving up-conversion and down-shifting luminescence have been prepared by a facile synthetic method. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray analysis, up-conversion and down-shifting fluorescence spectrometer were used to characterize the materials. By doping different lanthanide ions and tailoring the molar ratio of the doped lanthanide ions, three kinds of composites were obtained which could exhibit three-primary-color (red-green-blue, abbreviating as RGB) up-conversion luminescence under the irradiation of 980 nm laser, and generate red down-shifting color under the excitation of 393 nm. The composites show excellent photoluminescence properties, which attribute to NaYF 4 served as a major matrix for both the up-conversion and down-shifting materials. Moreover, the work provides a promising material for anti-counterfeiting application. [ABSTRACT FROM AUTHOR]