Room-temperature phosphorescent (RTP) nitrogen-doped carbon dots (N-CDs) have attracted great interest but their efficiency is usually dependent on a solid matrix. Developing efficient matrix-free RTP CDs is still a great challenge. Here, a simple strategy is reported to synthesize efficient matrix free RTP N-CDs from citric acid (CA) and basic fuchsine (BF) via a single step hydrothermal process. The synthesized N-CDs show strong fluorescence in aqueous solution and the solid state, and the RTP lifetime is long-lived (51.9 ms at 298 K). The phosphorescence of the N-CDs is attributed to the formation of an internal hydrogen bonded network by the organic polymers on the surface of the N-CDs. This reduces the nonradiative transitions of the triplet excitons and mitigates oxygen quenching. The application of N-CDs as security inks is demonstrated.
Yanzhi Zhang,Xiang Guo,Minghao Zhang,Ruirui Cui,Jun Zhang,Chaoyong Deng
In this study, a Sm 3+ ion-doped double perovskite structure oxide was developed to obtain a novel Ca 2 GaNbO 6 : Sm 3+ orange-red phosphor, which has compensated for the lack of a red component in commercial wLEDs . The results of morphological features and phase structure have confirmed that the synthesized compound maintains the same structure as Ca 2 GaNbO 6, and that Sm 3+ successfully enters into the main lattice of Ca 2 GaNbO 6 . In terms of optical properties , the photoluminescence (PL) emission spectra monitored at 406 nm has the strongest emission peak at 599 nm and shows strong orange-red light. The spectral shapes of PL at different concentrations remain consistent without wavelength drift, and perform best when the concentration is 3 mol%, that is, the concentration quenching point is 3 mol%. The quenching phenomenon is believed to be mainly attributed to dipole-dipole (d-d) interaction. The Ca 2 GaNbO 6 : 0.03Sm 3+ phosphor shows excellent color purity (CP = 99.0 %) and low color temperature (CCT = 1664 K) in terms of chromaticity (CIE). In terms of heat resistance , the thermal stability of Ca 2 GaNbO 6 : 0.03Sm 3+ phosphor is 82.80 % (423 K). The internal quantum efficiency (IQE) is 34.4 %. In terms of applications, the wLEDs made of Ca 2 GaNbO 6 : 0.03Sm 3+ phosphor emits warm white light and exhibit excellent performance in color rendering index and correlated color temperature (CRI = 94.5, CCT = 3877 K). At the same time, Ca 2 GaNbO 6 : Sm 3+ phosphor shows good solubility in PVA . Research shows that Ca 2 GaNbO 6 : Sm 3+ phosphor has good performance in the fields of wLEDs and security ink.
Bu Lingli,Luo Tao,Peng Huanjun,Li Ling,Long Dengying,Peng Jingdong,Huang Jing
Nitrogen-doped carbon dots (N-CDs) with fluorescence excitation/emission maxima at 365/450 nm were prepared by a one-step hydrothermal approach. The dots possess remarkable photostability, fluorescence blinking and good biocompatibility, and this favors utilization in stochastic optical reconstruction microscopy (STORM). A spatial resolution down to ~60 nm was achieved when imaging HeLa cells using 647-nm laser excitation. This opens new possibilities for various super-resolution techniques based on stochastic optical switching. The remarkable optical properties of the N-CDs also enable them to be applied as invisible security ink for use in patterning, information storage and anti-counterfeiting. Further, it is found that the fluorescence of the N-CDs can be quenched by curcumin with high efficiency due to a combination of inner filter effect and static quenching. Based on this, a fluorometric assay with a detection limit of 21 ng mL −1 was developed for the determination of curcumin.
Schematic representation of the applications of N-doped carbon dots (N-CDs). Curcumin quenches the fluorescence of N-CDs with high efficiency. The remarkable optical properties of the N-CDs enable them to be applied in fluorescent ink, cell imaging and stochastic optical reconstruction microscopy (STORM).
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