Highly Photoluminescent CsPbBr3/CsPb2Br5 NCs@TEOS Nanocomposite in Light-Emitting Diodes.

All-inorganic halide perovskite (CsPb2Br5) nanocrystals (NCs) have received widespread attention owing to their unique photoelectric properties. This work reports a novel strategy to control the phase transition from CsPbBr3 to CsPb2Br5 and investigates the effects of different treatment times and treatment temperatures on perovskite NCs formation. By controlling the volume of tetraethoxysilane (TEOS) added, the formation of different phases of perovskite powder can be well controlled. In addition, a white light-emitting diode (WLED) device is designed by coupling the CsPbBr3/CsPbBr3-CsPb2Br5 NCs@TEOS nanocomposite and CaAlSiN3:Eu2+ commercial phosphor with a 460 nm InGaN blue chip, exhibiting a high luminous efficiency of 57.65 lm/W, color rendering index (CRI) of 91, and a low CCT of 5334 K. The CIE chromaticity coordinates are (0.3363, 0.3419). This work provides a new strategy for the synthesis of CsPbBr3/CsPbBr3-CsPb2Br5 NCs@TEOS nanocomposite, which can be applied to the field of WLEDs and display devices.

A Real-Time Channel Prediction Model Based on Neural Networks for Dedicated Short-Range Communications.

Based on a multiple layer perceptron neural networks, this paper presents a real-time channel prediction model, which could predict channel parameters such as path loss (PL) and packet drop (PD), for dedicated short-range communications (DSRC). The dataset used for training, validating, and testing was extracted from experiments under several different road scenarios including highways, local areas, residential areas, state parks, and rural areas. The study shows that the proposed PL prediction model outperforms conventional empirical models. Meanwhile, the proposed PD prediction model achieves higher prediction accuracy than the statistical one. Moreover, the prediction model can operate in real-time, through updating its training set, to predict channel parameters. Such a model can be easily extended to the applications of autonomous driving, the Internet of Things (IoT), 5th generation cellular network technology (5G) and many others.

Efficient inverted quantum-dot light-emitting devices with TiO2/ZnO bilayer as the electron contact layer.

We have demonstrated an efficient inverted CdSe/CdS/ZnS core/shell quantum-dot light-emitting device (QD-LED) using a solution-processed sol-gel TiO2 and ZnO nanoparticle composite layer as an electron-injection layer with controllable morphology and investigated the electroluminescence mechanism. The introduction of the ZnO layer can lead to the formation of spin-coated uniform QD films and fabrication of high-luminance QD-LEDs. The TiO2 layer improves the balance of charge injection due to its lower electron mobility relative to the ZnO layer. These results offer a practicable platform for the realization of a trade-off between the luminance and efficiency in the inverted QD-LEDs with TiO2/ZnO composites as the electron contact layer.

AuBr3 Induces CsPb(Br/I)3 QDs to Self-Assemble into Nanowires.

Perovskite quantum dots can form various forms such as nanowires, nanorods, and nanosheets through self-assembly. Nanoscale self-assembly can be used to fabricate materials with excellent device properties. This study introduces AuBr3 into CsPb(Br/I)3 quantum dots, causing them to assemble into nanowires. The nanowires form because part of Au3+ is surface-doped to replace Pb2+, and the [PbX6]4- octahedral structure is distorted. The symmetry of the structural surface is broken, and a dipole-moment-induced field is generated, thus promoting self-assembly. Moreover, the presence of Au nanoparticles (NPs) causes a localized surface plasmon resonance and generates strong van der Waals forces that promote self-assembly. Finally, to test other applications of perovskite nanowires, the solution method is used to prepare films by compounding the sample solution and polystyrene (PS) for backlighted displays.

Tunable Green Light-Emitting CsPbBr3 Based Perovskite-Nanocrystals-in-Glass Flexible Film Enables Production of Stable Backlight Display.

Despite recent advances in producing perovskite-nanocrystals-in-glass (PNG) for display application, it remains challenging to achieve ultrapure and large-area CsPbBr3 PNG-based flexible films with tunable green emission. Herein, we report a facile strategy to produce flexible film containing CsPbBr3 PNG. Specifically, the achievement of CsPbBr3 PNG with tunable green emissions (517-528 nm) is realized by elaborate regulation of the glass precursor concentration and thermal treatment temperature by an in situ growth method. With the integration of red-light-emitting CsPbBrxI3-x PNG powder, the color gamut of as-prepared white-light-emitting sources can cover up to 126.27% of the NTSC 1953 standard and 93.9% of the Rec. 2020 standard. Notably, flexible and large-area white-light-emitting films can be readily obtained by sandwiching and gluing mixed PNG powders between two layers of hydrophobic and transparent PET films. Intriguingly, as-prepared PNG films exhibit excellent hydrothermal, photostability, and long-term operation stability, making them promising for practical ultrahigh-definition displays.

Biomolecule-assisted green route to Sb2S3 crystals with three-dimensional dandelionlike patterns.

This paper describes a simple biomolecule-assisted solvothermal approach to fabricate the three-dimensional (3D) Sb2S3 microsphere with a wealth of novel morphologies in the presence of L-cysteine, which served as both the sulfur source and the directing molecule in the formation of antimony sulfide nanostructures. The effects of different solvents, and polyvinylpyrrolidone (PVP) on the morphology, structure, and phase composition of the as-prepared Sb2S3 products were discussed. The formation of 3D dandelionlike Sb2S3 microsphere was probably via the mechanism of the orientated aggregation growth of the Sb2S3 particles under the complexing action of L-cysteine, and co-action of the surfactant PVP. The absorption spectra of as-prepared 3D dandelionlike Sb2S3 structures show an optical shoulder band gap of 1.81 eV, which is near to the optimum for photovoltaic conversion.

Nanobubbles promote nutrient utilization and plant growth in rice by upregulating nutrient uptake genes and stimulating growth hormone production.

Excessive application of chemical fertilizers can lead to serious environmental problems. In this study, we explored the use of nanobubble water for irrigation of crop rice as a means of reducing fertilizer use. The effect of nanobubbles on plant growth and nutrient uptake was evaluated in the laboratory, while crop yield and the efficiency of fertilizer use were evaluated in a field study. The laboratory experiments indicated that nanobubbles significantly improve plant height and root length in rice seedlings. Nanobubble treatment stimulated synthesis of the growth hormone gibberellin and upregulated the plant nutrient absorption genes OsBT, PiT-1 and SKOR, resulting in increased nutrient uptake and utilization by the roots. The field experiments verified the laboratory observations, showing that nanobubble treatment significantly increases rice yield by almost 8% when using similar levels of fertilizer as controls. Moreover, the same yield as controls was achieved with approximately 25% less fertilizer. As well as their impact on growth hormones and nutrient absorption genes, nanobubbles, due to hydrophobic and surface charge properties, enhance the release and absorption of soil nutrients, thereby reducing fertilizer demand. Overall, this study highlights a new and sustainable water irrigation strategy for enhancing crop yield and reducing chemical fertilizer waste.

Amplified spontaneous emission and random lasing using CsPbBr3 quantum dot glass through controlling crystallization.

By increasing the heat treatment temperature, the average size of CsPbBr3 quantum dots (QDs) in the glass matrix was increased, which contributed to a 5.5 fold increase of the optical gain coefficients. And the corresponding lasing threshold decreased from 0.752 mJ cm-2 to 0.138 mJ cm-2.

The preparation and up-conversion properties of full spectrum CsPbX3 (X = Cl, Br, I) quantum dot glasses.

All-inorganic perovskite (CsPbX3) quantum dots (QDs) have achieved unprecedented success in various applications due to their outstanding performance. Nevertheless, the inherent instability of these QDs severely limits their practical applications. Here, ultra-stable full visible spectrum CsPbX3 (X = Cl, Br, I) QD glasses are prepared successfully. For the first time, the full spectrum tunable up-conversion (UC) emission of CsPbX3 QD glasses ranging from 420 nm to 711 nm under excitation with an 800 nm femtosecond (fs) laser was achieved. Importantly, the two-photon absorption properties, the exciton binding energy and the UC full width at half maximum (FWHM) of CsPbCl1.5Br1.5 (blue), CsPbBr3 (green), and CsPbBr1.5I1.5 (red) QD glasses were studied in depth. Furthermore, CsPbCl1.5Br1.5 showed the highest exciton binding energy (∼87.5 meV), allowing the CsPbCl1.5Br1.5 QD glass to act as a good optical gain material that could more easily achieve amplified spontaneous emission (ASE).

Tb3+, Eu3+ Co-doped CsPbBr3 QDs Glass with Highly Stable and Luminous Adjustable for White LEDs.

Herein, we have introduced rare-earth cations Tb3+ and Eu3+ into CsPbBr3 QDs glass by conventional melt-quenching. Rare-earth cations like Tb3+ emit green light, causing the main peak of bromide lead cesium to exhibit some redshift, owing to the energy transfer between CsPbBr3 and Tb3+. To achieve adjustable light, Eu3+ emits red light, which was doped in this glass with different proportions to solve the problem of red deficiency. More importantly, Tb3+ and Eu3+ co-doped CsPbBr3 QDs glass shows a series of desirable characteristics due to the energy transfer between Tb3+ and Eu3+. Interestingly, the blue light radiated by blue chip can excite Tb3+, Eu3+, and CsPbBr3 perovskite effectively. We acquired high-performance white light-emitting diodes with color-rendering index, color coordinate transformation, and luminous efficiency of 85.7, 4945 K, and 63.21 lm/W under the current of 20 mA. This acquired Tb3+, Eu3+ co-doped CsPbBr3 QDs glass proved the significant feasibility of luminescent materials in solid warm light source.

Moderate fabrication and characterization of the microcrystalline Sr2CuO3 glass films with effective nonlinearities.

Since nonlinear optical materials used in the ultrafast all-optical switching is an important part for the modern optical technology, cuprates have been widely investigated for their specific Cu-O chain structure and intriguing optical properties. We present a new preparation method of microcrystalline Sr2CuO3 glass films on glass substrates combining spin-coating and co-sintering techniques. Then, the as-prepared samples were polished for different times to obtain microcrystalline Sr2CuO3 glass films with varying thickness. The influence of polishing time on the structure, the valence state and the nonlinear optical response were discussed, respectively. The purity of the Sr2CuO3 phase, surface morphology and the chemical composites of these synthesized glass films were given with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Importantly, optical absorption spectroscopy and Z-scan technique were used to measure linear absorption and third-order optical nonlinearity of the films. The experiments showed that third-order nonlinear susceptibility of the 140 min polished film sample with a thickness of 18 µm was up to 1.23 × 10-12 esu, indicating its potential application in the nonlinear field.

Ultrastability and color-tunability of CsPb(Br/I)3 nanocrystals in P-Si-Zn glass for white LEDs.

A series of CsPbBrxI3-x NC glasses, showing tunable emission (523-693 nm) controlled by different ratios of Br- and I-, were successfully prepared. The CsPbBrxI3-x NC glasses exhibited excellent optical properties and outstanding stability towards ambient conditions, water and heat.

CsPbBr3:xEu3+ perovskite QD borosilicate glass: a new member of the luminescent material family.

Eu3+ ions were introduced into the lattices of CsPbBr3 perovskite QDs and a tunable multicolour emission from CsPbBr3:xEu3+ perovskite QD glass was successfully obtained. Multicolour LEDs that were fabricated by combining the as-prepared CsPbBr3:xEu3+ QD glasses with a UV chip were also researched in this study.

Use of long-term stable CsPbBr3 perovskite quantum dots in phospho-silicate glass for highly efficient white LEDs.

We report the synthesis of CsPbBr3 QDs with great stability and high quantum yield in phospho-silicate glass, which was fabricated by using a heat-treatment approach, for white light emitting devices. QD glasses exhibited excellent photo- and thermal stability, and significantly prolonged the lifetime of light emitters under ambient air conditions.

Multicolour nitrogen-doped carbon dots: tunable photoluminescence and sandwich fluorescent glass-based light-emitting diodes.

The first use of the combination of ammonium citrate (AC) and ethylenediamine tetraacetic acid (EDTA) as coordinating precursors for the synthesis of highly fluorescent (quantum yield = 67%) multicolour nitrogen-doped carbon dots (CDs) is reported. Under UV light, these CDs emitted outstanding luminescence in colours from dark blue to red. Interestingly, a single component white-light CD point with high fluorescence efficiency was obtained by surface control. Alterations of the photoluminescence (PL) emission of these full-colour CDs were tentatively proposed to benefit from surface functional groups, such as C[double bond, length as m-dash]O and C[double bond, length as m-dash]N. An energy-level model was proposed to explain the continuously adjustable full-colour emission. The white light may be attributed to the overlap of diverse light emission induced by electron transitions between the energy levels. Subsequently, to avoid aggregation-induced solid-state fluorescence quenching, multicolour CD-based sandwich glasses with various colour emission was fabricated, which is anticipated to be compatible with the all-optical light-emitting diodes (LEDs). The facile preparation and outstanding optical features are believed to provide an alternative synthesis route and inspire more research into applications and CD-based materials of multicolour CDs.

Valence state control and third-order nonlinear optical properties of copper embedded in sodium borosilicate glass.

The integrated and transparent sodium borosilicate glasses that contain copper exhibiting different colors, that is, red, green, and blue were synthesized by combining the sol-gel process and heat treatment in H2 gas. To reveal substantially the cause of different colors in the glass, X-ray diffraction (XRD), transmission electron microscopy (TEM) and high resolution TEM (HRTEM) were systematically applied to investigate and determine the microstructure of the doped matter. The results showed three different crystals had formed in the red, green and blue glass, and the sizes of these crystals were range from 9 to 34, 1 to 6, and 1 to 5 nm, respectively. The valence state of copper was further analyzed by X-ray photoelectron spectroscopy (XPS) and electron energy loss spectroscopy (EELS). The third-order nonlinear optical properties of the glasses were investigated by using Z-scan technique at the wavelength of 800 nm. Interestingly, the third-order nonlinear absorption of the red, green, and blue glass can be successfully controlled from reverse saturable absorption, no absorption to saturable absorption and the optical nonlinear susceptibility χ((3)) of the red, green and blue glass were estimated to be 6.4 × 10(-14), 1.6 × 10(-14), and 2.6 × 10(-14) esu in the single-pulse energy of 0.36 µJ, respectively.

Exploring the effect of band alignment and surface states on photoinduced electron transfer from CuInS2/CdS core/shell quantum dots to TiO2 electrodes.

Photoinduced electron transfer (ET) processes from CuInS2/CdS core/shell quantum dots (QDs) with different core sizes and shell thicknesses to TiO2 electrodes were investigated by time-resolved photoluminescence (PL) spectroscopy. The ET rates and efficiencies from CuInS2/CdS QDs to TiO2 were superior to those of CuInS2/ZnS QDs. An enhanced ET efficiency was surprisingly observed for 2.0 nm CuInS2 core QDs after growth of the CdS shell. On the basis of the experimental and theoretical analysis, the improved performances of CuInS2/CdS QDs were attributed to the passivation of nonradiative traps by overcoating shell and enhanced delocalization of electron wave function from core to CdS shell due to lower conduction band offset. These results indicated that the electron distribution regulated by the band alignment between core and shell of QDs and the passivation of surface defect states could improve ET performance between donor and acceptor.

Synthesis of bulk-size transparent gadolinium oxide-polymer nanocomposites for gamma ray spectroscopy.

Heavy element loaded polymer composites have long been proposed to detect high energy X- and γ-rays upon scintillation. The previously reported bulk composite scintillators have achieved limited success because of the diminished light output resulting from fluorescence quenching and opacity. We demonstrate the synthesis of a transparent nanocomposite comprising gadolinium oxide nanocrystals uniformly dispersed in bulk-size samples at a high loading content. The strategy to avoid luminescence quenching and opacity in the nanocomposite was successfully deployed, which led to the radioluminescence light yield of up to 27 000/MeV, about twice as much as standard commercial plastic scintillators. Nanocomposites monoliths (14 mm diameter by 3 mm thickness) with 31 wt% loading of nanocrystals generated a photoelectric peak for Cs-137 gamma (662 keV) with 11.4% energy resolution.