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Precise control over size and morphology of metal−organic frameworks (MOFs) is challenging but important for extending these hybrid materials to many more advanced applications, in particular for nanotechnology and device integration. Through studying parameters for the fabrication of nanosized Dy(BTC)(H 2 O) MOF crystals using sodium acetate as the modulator, this paper discloses two essential parameters for miniaturizing the size of MOF crystals to the nanometer scale. One is the proper acid−base environment of the reaction medium which governs deprotonation of the organic linker and, hence, the nucleation process. The other is the use of capping groups capable of inhibiting crystallites from growing. Combining these two parameters makes it possible to control the size and change the morphology of Dy(BTC)(H 2 O) crystals. A mechanism based on coordination modulation together with pH adjustment is proposed for the growth of nanosized MOF crystals.

High quantum yields (QY) and stable performances are prerequisites for implementing carbon dots in practical applications. In this study, we demonstrate that nitrogen-doped carbon dots (N-CDs), which were prepared via the hydrothermal treatment of citric acid (CA) and tris(hydroxymethyl)methyl aminomethane (Tris), have a high QY of 75%, together with excellent thermal and photo stability. These N-CDs deliver an excellent thermal stability performance over the temperature range of 25 °C to 95 °C, and even at a heating temperature of 90 °C for 360 min. Upon exposure to UV illumination with a radiant intensity of 20 mW cm, 96% fluorescence intensity is retained. This florescence stability performance is probably due to the chemical composition and steric effect of the nitrogen-doping agent. Furthermore, the remarkable optical properties of these N-CDs allow them to be used as invisible ink for loading important information and advanced anti-counterfeiting.

The syntheses, structures, and electroluminescent properties are described for two new lanthanide complexes Ln(HFNH)3phen [HFNH = 4,4,5,5,6,6,6-heptafluoro-1-(2-naphthyl)hexane-1,3-dione; phen = 1,10-phenanthroline; Ln = Eu3+ (1), Sm3+ (2)]. Both complexes exhibit bright photoluminescence at room temperature (RT) due to the characteristic emission of Eu3+ and Sm3+ ion. Several devices using the two complexes as emitters were fabricated. The performances of these devices are among the best reported for devices using europium complex and samarium complex as emitters. The device based on 1 with the structure ITO/TPD (50 nm)/1:CBP (10%, 40 nm)/BCP (20 nm)/AlQ (30 nm)/LiF (1 nm)/Al (200 nm) exhibits the maximum brightness of 957 cd/m2, current efficiency of 4.14 cd/A, and power efficiency of 2.28 lm/W with a pure red Eu3+ ion emission. Especially, at the high brightness of 200 cd/m2, the device of 1 still has a high current efficiency of 2.15 cd/A. The device of 2 with a three-layer structure of ITO/TPD (50 nm)/2 (50 nm)/BCP (20 nm)/LiF (1 nm)/Al (200 nm) gives the maximum brightness of 42 cd/m2, current efficiency of 0.18 cd/A. By the comparison of the electroluminescent properties of devices based on Eu(TTA3phen (TTA = 2-thenoyltrifluoroacteonate) and 1, we conclude that the polyfluoration on the alkyl group of the ligand and the introduction of the long conjugate naphthyl group into the ligand improve the efficiency of 1-doped devices, especially at high current densities.

Two novel bis‐cyclometalated iridium complexes are successfully applied in organic light‐emitting diodes (OLEDs). Because of their better carrier transport ability and shorter excited stated lifetimes, good electroluminescence performances of the complexes are observed.

In this study, solvent-dependent emitting carbon dots (CDs) were synthesized by simple one-step hydrothermal treatment of o-phenylenediamine (oPD).

With 2-(2,4-difluorophenyl)pyridine (dfppy) as the first cyclometalated ligand and different monoanionic N-heterocyclic carbenes (NHCs) as the second cyclometalated ligands, 16 blue or greenish-blue neutral iridium(III) phosphorescent complexes, (dfppy)2Ir(NHC), were synthesized efficiently. The obtained Ir(III) complexes display typical phosphorescence of 455-485 nm with quantum yields up to 0.73. By modifying the phenyl moiety in the NHCs with electron-withdrawing substituents (e.g., -F or -CF3) or replacing it with N-heteroaromatic rings (pyridine or pyrimidine), the HOMO-LUMO gaps are broadened, and the emissions shift to the more blue region accordingly. Furthermore, to extend the application scope of NHCs as the second cyclometalated ligands, five other Ir(III) complexes from blue to red were synthesized with different first cyclometalated ligands. Finally, the organic light-emitting diodes using one blue emitter exhibit a maximum current efficiency of 37.83 cd A(-1), an external quantum efficiency of 10.3%, and a maximum luminance of 8709 cd m(-2). Our results demonstrate that NHCs as the second cyclometalated ligands are good candidates for the achievement of efficient phosphorescent Ir(III) complexes and corresponding devices.

Owing to the difficulty in acquiring compounds with combined high energy bandgaps and lower‐lying intramolecular charge‐transfer excited states, the development of ultraviolet (UV) thermally activated delayed fluorescence (TADF) materials is quite challenging. Herein, through interlocking of the diphenylsulfone (PS) acceptor unit of a reported deep‐blue TADF emitter (CZ‐PS) by a dimethylmethylene bridge, CZ‐MPS, a UV‐emissive TADF compound bearing a shallower LUMO energy level and a more rigid structure than those of CZ‐PS is achieved. This represents the first example of a UV‐emissive TADF compound. Organic light‐emitting diode (OLED) using CZ‐MPS as the guest material can emit efficient UV light with emission maximum of 389 nm and maximum total external quantum efficiency (EQEmax) of 9.3%. Note that this EQEmax value is twice as high as the current record EQEmax (4.6%) for UV‐OLEDs. This finding may shed light on the molecular design strategy for high‐performance UV‐OLED materials.