Efficient Deep-Blue Light-Emitting Diodes from Highly Luminescent Eu2+-Doped Alkali Metal Halide Nanocrystals via Lattice Field Modulation.

Lead-halide perovskite nanocrystals (NCs) are promising for fabricating deep-blue (<460 nm) light-emitting diodes (LEDs), but their development is plagued by low electroluminescent performance and lead toxicity. Herein, the synthesis of 12 kinds of highly luminescent and eco-friendly deep-blue europium (Eu2+)-doped alkali-metal halides (AX:Eu2+; A = Na+, K+, Rb+, Cs+; X = Cl-, Br-, I-) NCs is reported. Through adjustment of the coordination environment, efficient deep-blue emission from Eu-5d → Eu-4f transitions is realized. The representative CsBr:Eu2+ NCs exhibit a high photoluminescence quantum yield of 91.1% at 441 nm with a color coordinate at (0.158, 0.023) matching with the Rec. 2020 blue specification. Electrically driven deep-blue LEDs from CsBr:Eu2+ NCs are demonstrated, achieving a record external quantum efficiency of 3.15% and half-lifetime of ∼1 h, surpassing the reported metal-halide deep-blue NCs-based LEDs. Importantly, large-area LEDs with an emitting area of 12.25 cm2 are realized with uniform emission, representing a milestone toward commercial display applications.

Wide-coverage and Efficient NIR Emission from Single-component Nanophosphors through Shaping Multiple Metal-halide Packages.

Wide-coverage near infrared (NIR) phosphor-converted LEDs possess promising potential for practical applications, but little is developed towards the efficient and wide-coverage NIR phosphors. Here, we report the single-component lanthanide (Ln3+ ) ions doped Cs2 M(In0.95 Sb0.05 )Cl6 (M=alkali metal) nanocrystals (NCs), exhibiting emission from 850 to 1650 nm with high photoluminescence quantum yield of 20.3 %, which is accomplished by shaping the multiple metal halide octahedra of double perovskite via the simple alkali metal substitution. From Judd-Ofelt theoretical calculation and spectroscopic investigations, the shaping of metal halide octahedra in Cs2 M(In1-x Sbx )Cl6 NCs can break the forbidden of f-f transition of Ln3+ , thus increasing their radiative transition rates and simultaneously boosting the energy transfer efficiency from host to Ln3+ . Finally, the wide-coverage NIR LEDs based on Sm3+ , Nd3+ , Er3+ -tridoped Cs2 K0.5 Rb0.5 (In0.95 Sb0.05 )Cl6 NCs are fabricated and employed in the multiplex gas sensing and night-vision application.

White Light Afterglow in Carbon Dots Achieved via Synergy between the Room-Temperature Phosphorescence and the Delayed Fluorescence.

Carbon dot (CD) based long-lived afterglow emission materials have attracted attention in recent years, but demonstration of white-light room-temperature afterglow remains challenging, due to the difficulty of simultaneous generation of multiple long-lived excited states with distinct chromatic emission. In this work, a white-light room-temperature long-lived afterglow emission from a CD powder with a high efficiency of 5.8% and Commission International de l'Eclairage (CIE) coordinates of (0.396, 0.409) is realized. The afterglow of the CDs originates from a synergy between the phosphorescence of the carbon core and the delayed fluorescence associated with the surface CN moieties, which is accomplished by matching the singlet state of the surface groups of the CDs with the long-lived triplet state of the carbon core, resulting in an efficient energy transfer. It is demonstrated how the long-lived afterglow emission of CDs can be utilized for fabrication of white light emitting devices and in anticounterfeiting applications.

Oxalic Acid Enabled Emission Enhancement and Continuous Extraction of Chloride from Cesium Lead Chloride/Bromide Perovskite Nanocrystals.

All-inorganic cesium lead halide perovskite nanocrystals (NCs) have demonstrated excellent optical properties and an encouraging potential for optoelectronic applications; however, mixed-halide perovskites, especially CsPb(Cl/Br)3 NCs, still show lower photoluminescence quantum yields (PL QY) than the corresponding single-halide materials. Herein, anhydrous oxalic acid is used to post-treat CsPb(Cl/Br)3 NCs in order to initially remove surface defects and halide vacancies, and thus, to improve their PL QY from 11% to 89% for the emission of 451 nm. Furthermore, due to the continuous chelating reaction with the oxalate ion, chloride anions from the mixed-halide CsPb(Cl/Br)3 perovskite NCs could be extracted, and green emitting CsPbBr3 NCs with PL QY of 85% at 511 nm emission are obtained. Besides being useful to improve the emission of CsPb(Cl/Br)3 NCs, the oxalic acid treatment strategy introduced here provides a further tool to adjust the distribution of halide anions in mixed-halide perovskites without using any halide additives.

Highly efficient and stable blue-emitting CsPbBr3@SiO2 nanospheres through low temperature synthesis for nanoprinting and WLED.

Inorganic perovskite quantum dots (QDs) have attracted wide attention in display and solid-state lighting because of their easily tunable band-gaps and high photoluminescence quantum yields (PLQY) of green light emission. However, some drawbacks limit their practical applications, including the low PLQY of blue light emission and the instability in the moisture environment. In this work, efficient blue-light emitting CsPbBr3 perovskite QDs with PLQY of 72% were developed through a bandgap engineering approach. The achieved blue-light emitting PLQY is much higher than the values acquired in the inorganic perovskite QDs in the literature. And the emission color of the as-prepared QDs can be facially tuned by only adjusting the reaction temperature. Further, the mono-dispersed perovskite QDs@SiO2 composites were constructed benefiting from the low temperature synthesis. The optical performance of the QDs could be well persisted even in the moisture environment. Finally, the as-prepared QDs@SiO2 composite was fabricated as the QD ink on the anti-counterfeit printing technology, from which the obtained pattern would emit varied color under UV lamp. And the as-prepared composites was also applied for fabricating WLED, with Commission Internationale de l'Eclairage (CIE) color coordinates of (0.33, 0.38) and power efficiency of 32.5 lm W-1, demonstrating their promising potentials in solid-state lighting.

Emitting color tunable carbon dots by adjusting solvent towards light-emitting devices.

Carbon dots (CDs), one of the most significant classes of carbon-based nanophosphors, have attracted extensive attention in recent years. However, few attempts have been reported for realizing CDs with tunable emissions, especially for obtaining the red-light emissions with high photoluminescence quantum yields. Herein, we synthesized CDs with different chromatic blue, green and red emissions by facilely changing the reaction solvent during hydrothermal conditions. The photoluminescence quantum yields of 34%, 19% and 47% for the blue, green and red emissions, respectively, were achieved. Furthermore, the solid-state CD/PVA composite films were constructed through mixing the CDs with PVA polymer, in which the self-quenching of photoluminescence of CDs had been successfully avoided benefiting from the formation of hydrogen bonds between the CDs and PVA molecules. Finally, the warm white light emitting diode (WLED) was fabricated by integrating CD/PVA film on a UV-LED chip. The WLED exhibited the Commission International de l'Eclairage coordinates (CIE) of (0.38, 0.34), correlated color temperature of 3913 K and color rendering index of 91, respectively, which were comparable with the commercial WLEDs.

Carbon dot/polyvinylpyrrolidone hybrid nanofibers with efficient solid-state photoluminescence constructed using an electrospinning technique.

Carbon dots (CDs) are the promising candidates for application in optoelectronic and biological areas due to their excellent photostability, unique photoluminescence, good biocompatibility, low toxicity and chemical inertness. However, the self-quenching of photoluminescence as they are dried into the solid state dramatically limits their further application. Therefore, realizing efficient photoluminescence and large-scale production of CDs in the solid state is an urgent challenge. Herein, solid-state hybrid nanofibers based on CDs and polyvinylpyrrolidone (PVP) are constructed through an electrospinning process. The resulting solid-state hybrid PVP/CD nanofibers present much enhanced photoluminescence performance compared to the corresponding pristine colloidal CDs due to the decrease in non-radiative recombination of electron-holes. Owing to the suppressed self-quenching of CDs, the photoluminescence quantum yield is considerably improved from 42.9% of pristine CDs to 83.5% of nanofibers under the excitation wavelength of 360 nm. This has great application potential in optical or optoelectronic devices.

Modulation of the photoluminescence in carbon dots through surface modification: from mechanism to white light-emitting diodes.

Carbon dots (CDs) have emerged as a new type of fluorescent material because of their unique optical advantages, such as high photoluminescence quantum yields (QYs), excellent photo-stability, excitation-dependent emissions, and low toxicity. However, the photoluminescence mechanism for CDs remains unclear, which limits their further practical application. Here, CDs were synthesized via a solvothermal route from citric acid and urea. Through the oxidation and reduction treatment of pristine CDs, the origin of the photoluminescence and the involved mechanism were revealed. We found that the blue/green/red emissions originated from three diverse emitting states, i.e. the intrinsic state, and C=O- and C=N-related surface states, respectively. Based on the as-prepared CDs, a pH sensor depending on the radiometric luminescence detection was developed. Furthermore, we constructed CD/PVP (PVP, polyvinylpyrrolidone) composite films, which exhibited white light emission with photoluminescence QYs of 15.3%. The white light emission with different correlated color temperatures (CCTs), from 4807 K to 3319 K, was obtained by simply changing the amount of PVP solution. Benefiting from the white light-emitting solid-state films, single-component white light-emitting diodes were fabricated with an average color rendering index value (Ra) of 80.0, luminous efficiency of 10.2 lm W-1, and good working stability, thus indicating a promising potential for practical lighting applications.

Doping Lanthanide into Perovskite Nanocrystals: Highly Improved and Expanded Optical Properties.

Cesium lead halide (CsPbX3) perovskite nanocrystals (NCs) have demonstrated extremely excellent optical properties and great application potentials in various optoelectronic devices. However, because of the anion exchange, it is difficult to achieve white-light and multicolor emission for practical applications. Herein, we present the successful doping of various lanthanide ions (Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Er3+, and Yb3+) into the lattices of CsPbCl3 perovskite NCs through a modified hot-injection method. For the lanthanide ions doped perovskite NCs, high photoluminescence quantum yield (QY) and stable and widely tunable multicolor emissions spanning from visible to near-infrared (NIR) regions are successfully obtained. This work indicates that the doped perovskite NCs will inherit most of the unique optical properties of lanthanide ions and deliver them to the perovskite NC host, thus endowing the family of perovskite materials with excellent optical, electric, or magnetic properties.

[High-intensity laser therapy combined with targeted hand function training for the treatment of grade 1-2 thumb carpometacarpal osteoarthritis].

OBJECTIVE: To explore clinical effect of high-intensity laser therapy(HILT) combined with targeted hand function training on pain and lateral pinch force in grade 1-2 thumb carpometacarpal(CMC) osteoarthritis(OA). METHODS: From April 2020 and April 2022, 42 female patients with thumb CMC OA grade 1 to 2, aged from 58 to 80 years old with an everage of (68.90±7.58) years old were divided into observation group of 21 patients who received HILT and targeted hand function training for 4 weeks, and 21 patients in control group who received ultrashort wave therapy combined with using of an orthosis for 4 weeks. Visual analogue scale(VAS) was applied to evaluate degree of pain, function of finger was evaluated by dynamometer to measure lateral pinch force at baseline, immediately following intervention at 4 and 12 weeks following intervention. RESULTS: VAS and lateral pinch force at immediately and 12 weeks after intervention betwwen two groups were better than that of before intervention(P<0.05). Compared with control group, the degree of pain in observation group improved more(immediately after intervention t=3.37, P<0.05, 12 weeks after intervention t=9.05, P<0.05), lateral pinch force higher than that of control group (immediately after intervention t=-2.55, P<0.05, 12 weeks after intervention t=9.51, P<0.05). CONCLUSION: High-intensity laser therapy combined with targeted hand function training is more effective than traditional methods in improving pain and lateral pinch force in grade 1-2 thumb carpometacarpal osteoarthritis.

A Molecular Engineering Strategy for Achieving Blue Phosphorescent Carbon Dots with Outstanding Efficiency above 50.

Highly efficient emission has been a long-lasting pursuit for carbon dots (CDs) owing to their enormous potential in optoelectronic applications. Nevertheless, their room-temperature phosphorescence (RTP) performance still largely lags behind their outstanding fluorescence emission, especially in the blue spectral region. Herein, high-efficiency blue RTP CDs have been designed and constructed via a simple molecular engineering strategy, enabling CDs with an unprecedented phosphorescence quantum efficiency of to 50.17% and a long lifetime of 2.03 s. This treating route facilitates the formation of high-density (n, π*) configurations in the CD π-π conjugate system through the introduction of abundant functional groups, which can evoke a strong spin-orbit coupling and further promote the intersystem crossing from singlet to triplet excited states and radiative recombination from triplet excited states to ground state. With blue phosphorescent CDs as triplet donors, green, red, and white afterglow composites are successfully fabricated via effective phosphorescence Förster resonance energy transfer. Importantly, the color temperature of the white afterglow emission can be widely and facilely tuned from cool white to pure white and warm white. Moreover, advanced information encryption, light illumination, and afterglow/dynamic visual display have been demonstrated when using these multicolor-emitting CD-based afterglow systems.

Synergistic regulation effect of magnesium and acetate ions on structural rigidity for synthesizing an efficient and robust CsPbI3 perovskite toward red light-emitting devices.

The structure of CsPbI3 nanocrystals (NCs) with excellent photoelectric properties easily collapses, which hinders their application in light-emitting diodes (LEDs). Herein, we accomplished the synthesis of efficient and stable CsPbI3 NCs by regulating structural rigidity under the synergistic effect of Mg2+ and AcO- ions. The introduced AcO- and Mg2+ ions increase surface steric hindrance and defect formation energy, which enhances the structural rigidity of the perovskite. As a result, the CsPbI3 NCs display an outstanding photoluminescence quantum yield of 95.7%, in conjunction with reduced defect state density, balanced carrier injection, and distinguished conductivity. Remarkably, the modified CsPbI3 NCs exhibit excellent stability under ambient conditions for 180 days and can even survive when the temperature reaches 150 °C. Given their enhanced structural rigidity, LEDs made from these modified CsPbI3 NCs exhibit a maximum luminance and an EQE of 3281 cd m-2 and 13.2%, respectively, which are significantly improved compared with those of unmodified CsPbI3 NC LEDs.

Thermally Enhanced and Long Lifetime Red TADF Carbon Dots via Multi-Confinement and Phosphorescence Assisted Energy Transfer.

Thermally activated delayed fluorescence (TADF) materials, which can harvest both singlet and triplet excitons for high-efficiency emission, have attracted widespread concern for their enormous applications. Nevertheless, luminescence thermal quenching severely limits the efficiency and operating stability in TADF materials and devices at high temperature. Herein, a surface engineering strategy is adopted to obtain unique carbon dots (CDs)-based thermally enhanced TADF materials with ≈250% enhancement from 273 to 343 K via incorporating seed CDs into ionic crystal network. The rigid crystal network can simultaneously boost reverse intersystem crossing process via enhancing spin-orbit coupling between singlet and triplet states and suppressing non-radiative transition rate, contributing to the thermally enhanced TADF character. Benefiting from efficient energy transfer from triplet states of phosphorescence center to singlet states of CDs, TADF emission at ≈600 nm in CDs displays a long lifetime up to 109.6 ms, outperforming other red organic TADF materials. Thanks to variable decay rates of the delayed emission centers, time and temperature-dependent delayed emission color has been first realized in CDs-based delayed emission materials. The CDs with thermally enhanced and time-/temperature-dependent emission in one material system can offer new opportunities in information protection and processing.

Study of Temperature on the Corrosion Behavior of Antibacterial Steel by a Large-Scale Multiphase Flow Corrosion Test Loop.

The System #2 flow loop used in this study is a 4-inch-diameter, high-temperature, high-pressure system. In situ corrosion and electrochemical measurements were performed using a homemade flat corrosion specimen and a three-electrode probe. The experiment results show that temperature has an accelerated influence on the corrosion of antibacterial alloy steel. With the increase of temperature and the presence of O2 in the environment, a loose and porous corrosion product film was formed on the surface of the resistant steel, which made it easier for the corrosion medium to enter the corrosion product film from the pore, thus accelerating the corrosion.

Efficient and Stable CF3PEAI-Passivated CsPbI3 QDs toward Red LEDs.

Oleylamine and oleic acid are common organic capping ligands used in the hot injection preparation of perovskite quantum dots (QDs). Their labile nature is responsible for the poor colloidal stability and conductivity that affect the performance of perovskite QD light-emitting diodes (LEDs). We introduced 4-trifluoro phenethylammonium iodide (CF3PEAI) directly in the synthesis and found that CF3PEAI efficiently modified the I- vacancy defects on the QD surface and partially substituted the surface capping ligand oleylamine. The strong electron pulling ability of F in CF3PEAI results in a more positive -NH3+ terminal compared to that of PEAI, which promotes tight bonding of CF3PEAI on the surface of CsPbI3 QDs. As a result, we achieved bright QDs with a photoluminescence quantum yield of 92% and efficient red LEDs. The maximal luminance was improved to 4550 cd m-2 for 685 nm red light, which was nearly 4.6-fold of the LEDs with plain CsPbI3 QDs. Additionally, the peak external quantum efficiency reached 12.5%.

Highly Stable and Efficient Mn2+ Doping Zero-Dimension Cs2ZnxPb1-xCl4 Alloyed Nanorods toward White Electroluminescent Light-Emitting Diodes.

Zero-dimensional (0D) crystal structure perovskite NCs have reemerged as promising materials owing to their superior long-term stability; however, their poor conductivity leads to the inferior electrical performances and critically restricts the optoelectronic application of 0D perovskite materials. Herien, the alloyed 0D crystal structure Cs2ZnxPb1-xCl4 nanorods (NRs) have been synthesized by the modified hot-injection method, which emits bright blue-violet light at 408 nm, and the optimized photoluminescence quantum yield (PLQY) reaches 26%. The Cs2Zn0.88Pb0.12Cl4 NRs display more excellent air stability and an order of magnitude higher conductivity than CsPbCl3 nanocube films. In addition, we dope Mn2+ ions into the Cs2Zn0.88Pb0.12Cl4 NRs, which accomplished the optimized PLQY of 40.3% and polarized emission with r = 0.19. The light-emitting diodes (LEDs) based on Mn2+ ion doped Cs2Zn0.88Pb0.12Cl4 NRs exhibit a chromaticity coordinate (CIE) of (0.36, 0.33), an EQE of 0.3%, and a maximum luminance of 98 cd m-2. This work has enriched ideas for the production of white light perovskite LEDs.

Solution-Processed Efficient Perovskite Nanocrystal Light-Emitting Device Utilizing Doped Hole Transport Layer.

Light-emitting devices (LEDs) with inorganic perovskite nanocrystals (PNCs) fabricated through the all-solution process have tremendous potential for new-generation illumination and displays on account of their large area and cost-effective manufacturing. However, the development of efficient solution-processed PNC LEDs remains challenge, which mainly results from the fact that only a few types of charge transport layers can be employed for the subsequent deposition steps, thus leading to injection barriers and charge injection imbalance inside these LEDs. Herein 4,4'-bis(carbazole-9-yl) biphenyl (CBP) is introduced as a dopant into the poly(9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine) (TFB) hole transport layer (HTL), which efficiently modulates the mobility of charge carrier as well as the energy level of the HTL, resulting in the barrier-free injection of the charge carrier in the as-fabricated solution-processed PNC LEDs. Consequently, the luminance of red LEDs (688 nm) reaches 2990 cd m-2, and the external quantum efficiency achieves 8.1%, which is the optimal performance for solution-processed PNC LEDs to date. Additionally, the turn-on voltage and roll-off have also been improved by the more balanced charge injection.

Bright Blue Light Emission of Ni2+ Ion-Doped CsPbClxBr3-x Perovskite Quantum Dots Enabling Efficient Light-Emitting Devices.

In recent years, significant advances have been achieved in the red and green perovskite quantum dot (PQD)-based light-emitting diodes (LEDs). However, the performances of the blue perovskite LEDs are still seriously lagging behind that of the green and red counterparts. Herein, we successfully developed Ni2+ ion-doped CsPbClxBr3-x PQDs through the room-temperature supersaturated recrystallization synthetic approach. We simultaneously realized the doping of various concentrations of Ni2+ cations and modulated the Cl/Br element ratios by introducing different amounts of NiCl2 solution in the reaction medium. Using the synthetic method, not only the emission wavelength from 508 to 432 nm of Ni2+ ion-doped CsPbClxBr3-x QDs was facially adjusted, but also the photoluminescence quantum yield (PLQY) of PQDs was greatly improved due to efficient removal of the defects of the PQDs. Thus, the blue emission at 470 nm with PLQY of 89% was achieved in 2.5% Ni2+ ion-doped CsPbCl0.99Br2.01 QDs, which increased nearly three times over that of undoped CsPbClBr2 QDs and was the highest for the CsPbX3 PQDs with blue emission, fulfilling the National Television System Committee standards. Benefiting from the highly luminous Ni2+ ion-doped PQDs, the blue-emitting LED at 470 nm was obtained, exhibiting an external quantum efficiency of 2.4% and a maximum luminance of 612 cd/m2, which surpassed the best performance reported previously for the corresponding blue-emitting PQD-based LED.

Effect of extremely high CO2 pressure on the formation of the corrosion film on 13Cr stainless steel.

The corrosion behaviors of 13Cr martensitic steel under different CO2 partial pressures (4-28 MPa) were investigated by weight loss tests and surface characterizations. The results show that the corrosion rate of 13Cr steel shows a sharp increase under higher CO2 pressure (28 MPa), which reached approximately 20-180 times as large as those under lower CO2 pressures (4-12 MPa). Under the lower CO2 pressures, a single-layered Cr(OH)3 passive film forms and completely covers the steel surface. However, when the CO2 pressure reaches 28 MPa, a very different corrosion film which contains an inner Cr(OH)3 passive layer and an outer FeCO3 layer forms, and the inner passive layer shows local damage. This phenomenon can be explained by the lower pH (∼2.75) and the higher H2CO3 concentration in the solution under the higher CO2 pressure.

Effective blue-violet photoluminescence through lanthanum and fluorine ions co-doping for CsPbCl3 perovskite quantum dots.

All-inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) have received considerable attention in optoelectronic applications owing to their excellent photoluminescence properties. However, low blue-violet fluorescence emission and instability limit their practical application. Herein, we propose to improve the optical properties of CsPbCl3 QDs by co-doping La3+ and F- ions. The co-doped perovskite QDs were successfully synthesized using the hot injection approach, and they exhibited bright blue-violet emission and a high photoluminescence quantum yield of 36.5%, which is one order higher than that of undoped QDs. Enhanced photoluminescence performance compared to the initial CsPbCl3 QDs could be attributed to efficient modification of defects (Cl vacancy) and increased radiative recombination rate by the introduction of the dopants. Moreover, the as-prepared La3+ and F- ions co-doped CsPbCl3 QDs exhibited potential application for anti-counterfeiting.