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We selectively improved the viewing angle characteristics and light extraction efficiency of blue thermally activated delayed fluorescence (TADF) organic light-emitting diodes (OLEDs) by tailoring a nanofiber-shaped Si 3 N 4 layer, which was used as an internal scattering layer. The diameter of the polymer nanofibers changed according to the mass ratio of polyacrylonitrile (PAN) and poly(methyl methacrylate) (PMMA) in the polymer solution for electrospinning. The Si 3 N 4 nanofiber (SNF) structure was fabricated by etching an Si 3 N 4 film using the PAN/PMMA nanofiber as a mask, making it easier to adjust parameters, such as the diameter, open ratio, and height, even though the SNF structure was randomly shaped. The SNF structures exhibited lower transmittance and higher haze with increasing diameter, showing little correlation with their height. However, all the structures demonstrated a total transmittance of over 80%. Finally, by applying the SNF structures to the blue TADF OLEDs, the external quantum efficiency was increased by 15.6%. In addition, the current and power efficiencies were enhanced by 23.0% and 25.6%, respectively. The internal light-extracting SNF structure also exhibited a synergistic effect with the external light-extracting structure. Furthermore, when the viewing angle changed from 0° to 60°, the peak wavelength and CIE coordinate shift decreased from 20 to 6 nm and from 0.0561 to 0.0243, respectively. These trends were explained by the application of Snell's law to the light path and were ultimately validated through finite-difference time-domain simulations.

The series of alkali-metal tin chloride sulfates A 3 Sn 2 (SO 4 ) 3- x Cl 1+2 x (A = K, Rb, Cs; x = 0, 1), K 3 Sn 2 (SO 4 ) 3 Cl, Rb 3 Sn 2 (SO 4 ) 2 Cl 3 , and Cs 3 Sn 2 (SO 4 ) 2 Cl 3 , were successfully synthesized through an improved mild hydrothermal method. Interestingly, in addition to the cation size effect, the structure-directing effect of anions induces different symmetries in the three title compounds, with K 3 Sn 2 (SO 4 ) 3 Cl being noncentrosymmetric, while Rb 3 Sn 2 (SO 4 ) 2 Cl 3 and Cs 3 Sn 2 (SO 4 ) 2 Cl 3 are centrosymmetric. Powder second-harmonic generation (SHG) measurements indicate that K 3 Sn 2 (SO 4 ) 3 Cl is a nonlinear optical material that is type I phase matchable with a weak SHG response (0.1× KDP). Photoluminescence tests reveal that the three title compounds emit strong greenish yellow, orange, and salmon light, respectively, under UV excitation, indicating that they are promising inorganic solid fluorescent materials. Simultaneously, a detailed structural analysis of all the known tin(II) halide sulfates has been performed, which will guide the systematic exploration of high-performance tin(II)-based functional materials in the future.

In this work, BaYF 5 :20%Yb 3+ /2%Er 3+ / x %Bi 3+ (abbreviated as BaYF 5 :Yb,Er,Bi x , where x = 0-3.0) upconversion nanoparticles (UCNPs) with various doping concentrations of Bi 3+ were synthesized through a simple hydrothermal method. The influence of the doping amount of Bi 3+ on the microstructures and upconversion luminescence (UCL) properties of the BaYF 5 :Yb,Er,Bi x UCNPs was studied in detail. The doping concentration of Bi 3+ has little influence on the microstructures of the UCNPs but significantly impacts their UCL intensities. Under excitation of a 980 nm near-IR laser, the observed UCL intensities for the BaYF 5 :Yb,Er,Bi x UCNPs display first an increasing trend and then a decreasing trend with an increase in the ratio x , giving a maximum at x = 2.5. A possible energy-transfer process and simplified energy levels of the BaYF 5 :Yb,Er,Bi x UCNPs were proposed. The potential of the BaYF 5 :Yb,Er,Bi x UCNPs as contrast agents for computerized tomography (CT) imaging was successfully demonstrated. An obvious accumulation of BaYF 5 :Yb,Er,Bi x in tumor sites was achieved because of high passive targeting by the enhanced permeability and retention effect and relatively low uptake by a reticuloendothelial system such as liver and spleen. This work paves a new route for the design of luminescence-enhanced UNCPs as promising bioimaging agents for cancer theranostics.

In general, searching the lowest-energy structures is considerably more time-consuming for bimetallic clusters than for monometallic ones because of the presence of an increasing number of homotops and geometrical isomers. In this article, a basin hopping genetic algorithm (BHGA), in which the genetic algorithm is implanted into the basin hopping (BH) method, is proposed to search the lowest-energy structures of 13-, 38-, and 55-atom PtCo bimetallic clusters. The results reveal that the proposed BHGA, as compared with the standard BH method, can markedly improve the convergent speed for global optimization and the possibility for finding the global minima on the potential energy surface. Meanwhile, referencing the monometallic structures in initializations may further raise the searching efficiency. For all the optimized clusters, both the excess energy and the second difference of the energy are calculated to examine their relative stabilities at different atomic ratios. The bond order parameter, the similarity function, and the shape factor are also adopted to quantitatively characterize the cluster structures. The results indicate that the 13- and the 55-atom systems tend to be icosahedral despite different degrees of lattice distortions. In contrast, for the 38-atom system, Pt 10 Co 28 , Pt 11 Co 27 , Pt 17 Co 21 , Pt 19 Co 19 , Pt 20 Co 18 , and Pt 30 Co 8 tend to be disordered, while Pt 21 Co 17 presents a defected face-centered cubic (fcc) structure, and the remaining clusters are perfect fcc. The methodology and results of this work have referential significance to the exploration of other alloy clusters.

Nitrogen (N) losses from agricultural production contribute to detrimental impacts on water, soil, air, and human health. However, it is still lacking in evaluating global N budgets in agricultural systems. Hence, we conducted a global analysis on the current status of the N flows in the agricultural systems, explored the possible mitigation measures and challenges, and investigated the existing regulations on controlling N pollution. Globally, agricultural soils received a total of 73 kg of N ha -1 year -1 on average, including N fertilizer plus manure (61%), atmospheric N deposition (10%), and N litters and fixation (29%). The estimated global NH 3 loss to total N inputs was 17%, which led to a loss of $15 billion year -1 . The N use efficiency (NUE) in Eastern China (33%) was much lower than that in the Eastern United States (65%) or Western Europe (61%), leaving much room to enhance the NUE to increase agricultural food production. Meanwhile, higher NH 3 losses from N fertilizers and manure were found in Eastern China (22%) than the Eastern United States (17%) and Western Europe (17%). We highlight the urgency to improve the NUE and decrease NH 3 loss with lower environmental consequences. Our results showed high potentials to mitigate NH 3 volatilization and enhance the NUE by various measures, such as substituting manure N for chemical fertilizer N, applying controlled release fertilizers, and urease inhibitors. These measures should be implemented in combination with the transfer of knowledge to farmers with new technologies and increasing the farm size to enhance the efficiency of agricultural production in the future.

CoMoO 4 has gained great attention as an anode material for lithium-ion batteries owing to its high theoretical capacity of 980 mAh g -1 and relatively high electrochemical activity. Unfortunately, CoMoO 4 anode also has some drawbacks such as low electronic/ionic conductivity, inferior cyclic stability, and relative severe volumetric expansion during the lithiation/delithiation process, greatly inhibiting its further development and application. Herein, we report Co 0.8 Zn 0.2 MoO 4 /C nanosheet composite constructed via a novel and facile one-stone-three-birds strategy. The preparation of the Co 0.8 Zn 0.2 MoO 4 /C nanosheet is based on the following two-step process: the formation of Co/Zn nanosheet precursors derived from Co/Zn-ZIF rhombic dodecahedra via solvothermal pretreatment, followed by a calcination treatment with molybdic acid (H 2 MoO 4 ) in air. The as-prepared Co 0.8 Zn 0.2 MoO 4 /C is monoclinic crystal structured composite with the in situ formed active carbon, which is well-defined nanosheet with a rough surface and mean thickness of 60-70 nm for a single sheet. This Co 0.8 Zn 0.2 MoO 4 /C nanosheet composite possesses a larger surface area of 37.60 m 2 g -1 , showing a mesoporous structure. When used as anode materials, the as-obtained Co 0.8 Zn 0.2 MoO 4 /C composite can deliver as high as a discharge capacity of 1337 mAh g -1 after 300 cycles at 0.2C and still retain the capacity of 827 mAh g -1 even after 600 cycles at 1C, exhibiting outstanding lithium storage performances. The higher capacity and superior cyclic stability of the Co 0.8 Zn 0.2 MoO 4 /C composite should be ascribed to the synergistic effect of the substitution of Zn 2+ , in situ composited active carbon and the as-constructed unique microstructure for the Co 0.8 Zn 0.2 MoO 4 /C composite. Our present work provides a facile one-stone-three-birds strategy to effectively construct the architectures and significantly enhance electrochemical performances for other transition metal electrode materials.

By introduction of K + , Rb + , and Cs + cations into the classical commercial nonlinear optical crystal LiB 3 O 5 (LBO), the series of novel mixed-alkali-metal borates Li 2.6 K 0.4 [B 5 O 8 (OH) 2 ] (K-LBO), Li 2.85 Rb 0.15 [B 5 O 8 (OH) 2 ] (Rb-LBO), and Li 2.9 Cs 0.1 [B 5 O 8 (OH) 2 ] (Cs-LBO) have been obtained under hydrothermal conditions. The steric hindrance effect generated by the introduction of large alkali-metal cations and partial substitution of small Li + cations broke the three-dimensional (3-D) framework of [B 3 O 7 ] 5- borate-oxygen clusters in LBO and resulted in a structure rearrangement to produce infrequent [B 10 O 26 ] 22- 2-D layers. The unique layered structure induced an increase in birefringence in A-LBOs (A = K, Rb, Cs), which is favorable for phase matching during second-harmonic generation. All three compounds are potential deep-ultraviolet nonlinear optical materials, which was proved by UV-vis-NIR diffuse reflectance spectroscopy and second-harmonic-generation measurements.

Developing efficient catalytic materials for electrochemical water splitting is important. Herein, uniformly dispersed and size-controllable iridium (Ir) nanoparticles (NPs) were prepared using a nitrogen-functionalized carbon as the support (Ir/CN). We found that nitrogen functionalization can simultaneously modulate the size of Ir NPs to substantially enhance the catalytically active sites and adjust the electronic structure of Ir, thereby promoting electrocatalytic activity for water splitting. Consequently, the as-synthesized Ir/CN shows excellent electrocatalytic performance with overpotentials of 12 and 265 mV for hydrogen and oxygen evolution reactions in basic medium, respectively. These findings may pave the way for designing and synthesizing other similar materials as efficient catalysts for electrochemical water splitting.

Nitrogen (N)-doped carbons combined with transition-metal nanoparticles are attractive as alternatives to the state-of-the-art precious metal catalysts for hydrogen evolution reaction (HER). Herein, we demonstrate a strategy for fabricating three-dimensional (3D) Cu-encased N-doped carbon nanotube arrays which are directly grown on Cu foam (Cu@NC NT/CF) as a new efficient HER electrocatalyst. Cu nanoparticles are encased here instead of common transition metals (Fe, Co, or Ni) for pursuing a well-controllable morphology and an excellent activity by taking advantage of its more stable nature at high temperature and in acidic or alkaline electrolyte. It is discovered that metallic Cu exhibits strong electronic modulation on N-doped carbon to boost its electrocatalytic activity for HER. Such a nanostructure not only offers plenty of accessible highly active sites but also provides a 3D conductive open network for fast electron/mass transfer and facilitates gas escape for prompt mass exchange. As a result, the Cu@NC NT/CF electrode exhibits superior HER performance and durability, outperforming most of the reported M@NC materials. Furthermore, the etching experiments together with X-ray photoelectron spectroscopy (XPS) analysis reveal that the electronic modulation from encased Cu significantly enhances the HER activity of N-doped carbon. These findings open up opportunities for exploring other Cu-based nanomaterials as efficient electrocatalysts and understanding their catalytic processes.

Ln 3+ -doped fluoride is a far efficient material for realizing multicolor emission, which plays an important part in full-color displays, biolabeling, and MRI. However, studies on the multicolor tuning properties of Ln 3+ -doped fluoride are mainly concentrated on a complicated process using three or more dopants, and the principle of energy transfer mechanism is still unclear. Herein, multicolor tunable emission is successfully obtained only by codoping with Tb 3+ and Eu 3+ ions in β-NaGdF 4 submicrocrystals via a facile hydrothermal route. Our work reveals that various emission colors can be obtained and tuned from red, orange-red, pink, and blue-green to green under single excitation energy via codoping Tb 3+ and Eu 3+ with rationally changed Eu 3+ /Tb 3+ molar ratio due to the energy transfer between Tb 3+ and Eu 3+ ions in the β-NaGdF 4 host matrix. Meanwhile, the energy transfer mechanism in β-NaGdF 4 : x Eu 3+ /y Tb 3+ (x + y = 5 mol %) submicrocrystals is investigated. Our results evidence the potential of the dopants' distribution density as an effective way for analyzing energy transfer and multicolor-controlled mechanism in other rare earth fluoride luminescence materials. Discussions on the multicolor luminescence under a certain dopant concentration based on single host and wavelength excitation are essential toward the goal of the practical applications in the field of light display systems and optoelectronic devices.