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Metal nanoclusters (NCs) as a new type of fluorescent material have been extensively explored because of their attractive set of features such as their ultrafine size, low toxicity, and excellent photostability. However, little progress has been made in producing water-soluble, homogeneous, and ultrabright metal NCs. In this study, gold NCs (AuNCs) with a photoluminescence quantum yield (QY) as high as 65% are synthesized in water through a simple blending route. Weak emission is observed from the 6-aza-2-thiothymine-protected AuNCs (ATT-AuNCs); however, the fluorescence intensity can be prominently enhanced by introducing l-arginine (Arg) into the capping layer. The fluorescence enhancement mechanism is systematically investigated by the measurements of ultraviolet-visible absorption spectroscopy, photoluminescence spectroscopy, fluorescence lifetime spectroscopy, transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, ¹H nuclear magnetic resonance, and calculations from density functional theory, with results isolating the vital role of the ligand shell and ruling out the effect of the gold core. The supramolecular host-guest assemblies formed between ATT capped on the gold core and the guanidine group of Arg make the capping ligands of ATT rigid. Subsequently, the intramolecular vibration and rotation of ATT are greatly suppressed, which reduce the nonradiative relaxation of excited states and, as a result, predominantly increase the luminescence QY of ATT-AuNCs. Further experiments demonstrate that a small change in guanidine substituents can arouse obvious changes in the photoluminescence features of NCs. We envision that this work will substantively contribute to the process of developing efficient synthetic routes to high-quality metal NCs. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) is a compelling candidate for next-generation electronics beyond conventional silicon-based devices due to the exhibition of a sharp metal-insulator transition. In this study, in order to realize functional VO2 film for flexible electronics, the growth of VO2 film directly on a transparent and flexible muscovite via van der Waals epitaxy is established. The heteroepitaxy and structural transition of VO2 films on muscovite are examined by a combination of high-resolution X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The unique metal-insulator transition of VO2 is further revealed with a change in electrical resistance over 10³ and a more than 50% variation of optical transmittance. Furthermore, due to the nature of muscovite, the VO2/muscovite heterostructure possesses superior flexibility and optical transparence. The approach developed in this study paves an intriguing way to fabricate functional VO2 film for the applications in flexible electronics. [ABSTRACT FROM AUTHOR]

Exciplex systems have become increasingly important due to their good performance in devices. Considering their bipolar transporting properties, exciplex systems with strong blue fluorescence and high triplet energies could potentially be ideal hosts for fluorescenceâ€"phosphorescence hybrid (Fâ€"P) white organic light-emitting diodes (WOLEDs). Here we achieved an efficient blue exciplex system formed with a new material (4-dimesitylboryl)phenyltriphenylamine (TPAPB) and 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (TPBi), which exhibited a high photoluminescence quantum yield of 44.1%. Using only these two organic materials, a high performance blue-emitting OLED was fabricated with a maximum external quantum efficiency (EQE) of 7.0 ± 0.4%. Such high efficiency is not only among the highest results of blue fluorescent organic light-emitting diodes (OLEDs) but also indicates that high Ï (fraction of excitons that can potentially radiatively decay) can be as well achieved via a TTA triplet up-conversion process. By simply doping an orange phosphor, the first Fâ€"P WOLED using an exciplex host system was realized with a single-emission-layer structure and merely three organic materials. The WOLED exhibits a maximum power efficiency, current efficiency, and EQE of 29.6 ± 0.2 lm Wâ€"1, 42.5 ± 0.3 cd Aâ€"1, and 15.7 ± 0.3%, respectively. To the best of our knowledge, this highly efficient and structurally simplified exciplex-based Fâ€"P WOLED is truly unprecedented. [ABSTRACT FROM AUTHOR]