To improve the quality and durability of inorganic halide perovskite nanocrystals (NCs), ammonium halide and lead oxide (PbO) were separately employed for the synthesis of NCs with a tunable ratio of metal to halide. The halide-rich circumstance was therefore successfully set up and found to be beneficial for obtaining good quality NCs with high photoluminescence quantum yields and remarkable stability against purification compared to those qualities of previous regular methods with lead halide. The fabricated light-emitting diode (LED) devices with NCs made in a halide-rich circumstance demonstrated performance better than that of devices with NCs made in a halide-poor circumstance. A LED with CsPbBr 3 NCs with a 1:4 Pb:Br ratio showed an obvious improved maximal luminance of 12090 cd m −2 , a current efficiency of 3.1 cd A −1 , and an external quantum efficiency of 1.194%, which were much higher than those of devices with NCs synthesized by the regular method.

All inorganic cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite nanocrystals (PeNCs) are synthesized by employing polar solvent controlled ionization (PCI) method in precursors. The new strategy can be easily carried out at room temperature and allow to employ smaller amount of weaker polarity and a broader range of low-boiling low-toxic solvents. The as prepared CsPbX 3 PeNCs reveal tunable emission spectra from 380 to 700 nm and high quantum yields over 80% with narrow full width at half maximum (FWHM). Meanwhile, larger "effective Stokes shifts" of PeNCs in PCI method, which enlarges 200% more than other PeNCs in regular methods, are observed. Most interestingly, the PeNCs growth process is coupling with some typical crystals formations. The main morphologies of CsPbI 3 PeNCs are hybrid of nanorods and nanoparticles. The primary morphologies of CsPbBr x I 3-x and CsPbBr 3 PeNCs are nanowires, which are supposed to have great potentials for applying in laser arrays and highly sensitive photodetector applications. Furthermore, such superior optical is endowed to fabricate white light emitting diodes, which has wide color gamut covering up to 120% of the National Television Systems Committee color standard.

Semiconductor nanocrystals are intriguing because they show surface plasmon absorption features like noble metallic nanoparticles. In contrast with metal, manipulation of their unique plasmonic resonance could be easily realized by the free-carrier concentration. Here, it is demonstrated that MoO3–x nanodots can exhibit striking surface plasmon resonance located at near-infrared region under treatment of two different reducing agents. Furthermore, the tunable resonance mode has been achieved through appropriate redox processes. Refractive index sensing has been demonstrated by monitoring the plasmonic peak. The improved sensing application is ascribed to the enhanced electric field in the plasmonic nanocrystals. These new insights into MoO3–x nanodots pave a way to develop novel plasmonic applications such as photothermal therapy, light harvesting, and sensing.

922 wileyonlinelibrary.com www.particle-journal.com www.MaterialsViews.com COMMUNICATION achieved was 71.2 lm W −1 at an input current of 20 mA by employing a CIS QDs-based composite plate as the light convertor that was integrated with a blue LED chip. [ 26 ] The luminous effi ciencies of QD-WLEDs, however, are still obviously inferior to conventional phosphors-converted (pc) WLEDs, even if high-quality CIS QDs with 92% QY are employed. [ 9 ] The low effi ciency of QDs-based WLEDs can probably be attributed to two main factors. Firstly, micromolecules, such as penetrative oxygen or moisture, could corrode the surface ions and ligands of the QDs, resulting in defect trap states that cannot be ignored. [27][28][29] Secondly, the QDs tend to aggregate themselves because of incompatibility issues between the surface ligands and the ambient matrix. [30][31][32] Jang et al. [ 9 ] have developed a barrier layer formed of poly(vinylpyrrolidone) (PVP) and silica on the composite surface of the QDs to prevent photodegradation by oxygen molecules. The as-prepared remote-type WLEDs exhibited a luminous effi ciency of about 60 lm W −1 accompanied by good white-light quality at an input current of 20 mA. This assembled WLED proved to be effi cient, however, as the incompatibility between the surface organic ligands of the QDs and the polymer matrix remains, a gradually decaying light-converting effi ciency is inevitable due to aggregation of the QDs, especially after silicone high-temperature curing. Another strategy to improve the stability of QDs is the deposition of a compatible organic or inorganic layer on the quantum dots, by means of, for instance, surface modifi cation by amidocyanogen [ 5 ] or chemical growth of a silica layer. [ 2,24 ] QDs with compatible layers under ambient conditions showed an outstanding stability in the composite. However, the declining quantum effi ciency resulting from surface ligands phase transition at the initial stage remains a considerable challenge as they make the devices more vulnerable.In this communication, we use a low-cost paraffi n liquid to replace conventional octadecene (ODE) as the exclusive non-coordinating solvent for the synthesis of high-quality CIS QDs with core-shell structure. Mesoporous silica particles were combined with the QDs to obtain luminescent microbeans (LMBs) by a non-chemical method. These mesoporous structures do not only work as the barrier structure in the matrix to reduce the contact surface between the QDs and penetrative micro molecules, but also function as the lattice to avoid aggregation of the QDs. In order to reduce the thermal effect of the QDs from the InGaN chip, a composite plate with LMBs and poly(methyl methacrylate) (PMMA) was remotely packaged on a surface-mounted device (SMD) type LED to obtain a white-light device. The WLED demonstrated high stability, as well as a high luminous effi ciency. Quantum dots (QDs) have attracted widespread attention for use in white-light-emitting diodes (WLEDs) and QDs-based displays because of their high ...

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Various single-crystalline nanostructures of potassium tantalite-niobate (KTa 1-x Nb x O 3 , KTN) were synthesized by a hydrothermal method at 200 °C. Interesting structures including KTaO 3 nano-octahedrons, KTa 0.5 Nb 0.5 O 3 , KTa 0.35 Nb 0.65 O 3 , and KTa 0.77 Nb 0.23 O 3 nanocubes, KTa 0.25 Nb 0.75 O 3 tower-like nanostructures, and KNbO 3 truncated octahedrons were obtained. The amount of KOH and polyethylene glycol (PEG) is crucial for the formation of pure phase KTa 1-x Nb x O 3 with specific morphologies. The dissolution-precipitation growth mechanism should be accountable for the formation of perfect KTN cubes, and the competition between the supersaturation ratio and the surface energies of nanoclusters may react to the growth of octahedron and truncated octahedron KTN. The experimental results show that the formation of high-quality single-crystalline KTN with tower-like nanostructures may be ascribed to the oriented attachment mechanism.

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