Enhancing the Luminescence of La3Mg2NbO9:Mn4+ Phosphor through H3BO3 and Charge Compensator Co-Doping for Use in Plant Growth Lamps.

Mn4+-doped red-light-emitting phosphors have become a research hotspot that can effectively enhance photosynthesis and promote morphogenesis in plants. Herein, the red phosphor La3Mg2NbO9:Mn4+ was synthesized through the solid-state reaction method. The effects of adding H3BO3 and a charge compensator R+ (R = Li, Na, K) on the crystal structure, morphology, quantum efficiency, and luminous performance of the La3Mg2NbO9:Mn4+ phosphor were systematically analyzed, respectively. The results showed that adding H3BO3 flux and a charge compensator improved the quantum efficiency and luminescence intensity. The emission intensity of the phosphor was enhanced about 5.9 times when Li+ was used as the charge compensator, while it was enhanced about 240% with the addition of H3BO3 flux. Remarkably, it was also found that the addition of H3BO3 flux and a charge compensator simultaneously improved the thermal stability at 423 K from 47.3% to 68.9%. The prototype red LED fabricated using the La3Mg2NbO9:Mn4+,H3BO3,Li+ phosphor exhibited a perfect overlap with the phytochrome absorption band for plant growth. All of these results indicate that the La3Mg2NbO9:Mn4+,H3BO3,Li+ phosphor has great potential for use in agricultural plant lighting.

Photocatalytic hydrogen production and storage in carbon nanotubes: a first-principles study.

As it is a promising clean energy source, the production and storage of hydrogen are crucial techniques. Here, based on first-principles calculations, we proposed an integral strategy for the production and storage of hydrogen in carbon nanotubes via photocatalytic processes. We considered a core-shell structure formed by placing a carbon nitride nanowire inside a carbon nanotube to achieve this goal. Photo-generated holes on the carbon nanotube surface promote water splitting. Driven by intrinsic electrostatic field in the core-shell structures, protons produced by water splitting penetrate the carbon nanotube and react with photo-generated electrons on the carbon nitride nanowire to produce hydrogen molecules in the carbon nanotube. Because carbon nanotubes have high hydrogen storage capacity, this core-shell structure can serve as a candidate system for photocatalytic water splitting and safe hydrogen storage.

Analysis of the Rehabilitation Efficacy and Nutritional Status of Patients After Endoscopic Radical Thyroidectomy by Fast Track Surgery Based on Nutritional Support.

Objective: To investigate and analyze the effect of fast track surgery (FTS) based on nutritional support on the improvement of rehabilitation efficacy and nutritional status of patients after radical lumpectomy for thyroid cancer. Methods: Eighty-six patients admitted to our hospital for radical lumpectomy for thyroid cancer between April 2018 and April 2021 were selected, of which 40 patients admitted between April 2018 and April 2019 were included in the control group with conventional perioperative care. Forty-six patients admitted between May 2019 and April 2021 were included in the trial group with FTS care based on nutritional support. The two groups of patients were compared in terms of postoperative feeding time, length of stay, time out of bed, VAS scores, albumin (ALB), total protein (TP) and prealbumin (PA) levels, negative emotions [Mental Health Test Questionnaire (DCL-90)], quality of life [General Quality of Life Inventory (GQOLI-74)] and complication rates. Results: The patients in the trial group had shorter feeding time, hospitalization time and time out of bed than the control group (P < 0.05). After the intervention, ALB, TP and PA levels were higher in the trial group than in the control group vs. preoperatively (P < 0.05); VAS scores in the trial group were lower than VAS scores in the control group during the same period (P < 0.05). The postoperative DCL-90 scores of the trial group were lower than those of the control group (P < 0.05); the GQOLI-74 scores and total scores of the trial group were higher than those of the control group at the 3-month postoperative follow-up (P < 0.05). The overall incidence of complications such as hoarseness, choking on water, hand and foot numbness, wound infection, and hypocalemia was lower in the trial group than in the control group (P < 0.05). Conclusion: The implementation of FTS care based on nutritional support for patients after endoscopic radical thyroidectomyr can effectively improve the postoperative recovery and reduce their pain level, as well as help improve their nutritional status, negative emotions and improve their quality of life, which is worth promoting.

Spin-Dependent Polaron Dynamics in Organic Ferromagnets.

The spin-dependent polaron dynamics in organic ferromagnets under driven electric fields are investigated by using the extended Su-Schrieffer-Heeger (SSH) model coupled with a nonadiabatic dynamics method. It is found that the spin-down polaron with the same spin orientation as the radicals drifts faster than the spin-up one under the same driven electric field. In an applicable range of driven electric fields, the velocity of the spin-down polaron is about 3.4 times that of the spin-up one. The dynamical property of the polaron with each spin (up or down) is asymmetric upon the reversal of the driven electric fields. The diverse dynamical properties of polarons with specific spins can be attributed to the spin nondegenerate polaron energy levels, the dipole moment generated by the asymmetrical polaron charge distributions and the strong electron-lattice coupling in organic ferromagnets. Our findings are expected to be useful for improving organic ferromagnet based spintronic devices.

Two-dimensional XC6-enes (X = Ge, Sn, Pb) with moderate band gaps, biaxial negative Poisson's ratios, and high carrier mobility.

Graphene-based analogs and derivatives provide numerous routes to achieve unconventional properties and potential applications. Particularly, two-dimensional (2D) binary materials of group-IV elements are drawing increasing interest. In this work, we proposed the design of three 2D graphene-based materials, namely, XC6-enes (X = Ge, Sn, or Pb), based on first-principles calculations. These new materials possess intriguing properties superior to graphene, such as biaxial negative Poisson's ratio (NPR), moderate bandgap, and high carrier mobility. These XC6-enes comprise sp2 carbon and sp3 X (X = Ge, Sn, Pb) atoms with hexagonal and pentagonal units by doping graphene with X atoms. The stability and plausibility of these 2D materials are verified from formation energies, phonon spectra, ab initio molecular dynamic simulations, and elastic constants. The incorporation of X atoms leads to highly anisotropic mechanical properties along with NPR due to the unique tetrahedral structure and hat-shaped configuration. In the equilibrium state, all the XC6-enes are moderate-band-gap semiconductors. The carrier mobilities of the XC6-enes were highly anisotropic (∼104 cm-2 V-1 s-1 along the [010]-direction). Such outstanding properties make the 2D frameworks promising for application in novel electronic and micromechanical devices.

New Spiral Form of Carbon Nitride with Ultrasoftness and Tunable Electronic Structures.

The structural diversity and multifunctionality of carbon nitride materials distinct from pure carbon materials are drawing increasing interest. Using first-principles calculations, we proposed a stable spiral structure of carbon nitride, namely spiral-C3N, which is composed of sp2-hybridized carbon and pyridine nitrogen with a 60° helical symmetry along the z-direction. The stability was verified from the cohesive energy, phonon spectrum, and elastic constants. Despite the strong covalent bonds of the spiral framework, the spiral-C3N exhibits a hardness lower than 12.00 GPa, in sharp contrast to the superhardness of cubic carbon nitrides reported in previous literature, which can be attributed to the unique porous configuration. The softness of the spiral-C3N was also confirmed by the small ideal strengths, which are, respectively, 33.00 GPa at a tensile strain of 0.22 along the [1̅21̅0] direction and 18.00 GPa at a shear strain of 0.52 in the (0001)[1̅21̅0] direction. Electronic band structure of spiral-C3N exhibits metallic features. A metal-semiconductor transition can be triggered by hydrogenation of the pyridine nitrogen atoms of spiral-C3N. Such a new three-dimensional spiral framework of sp2-hyperdized carbon and nitrogen atoms not only enriches the family of carbon nitride materials but also finds application in energy conversion and storage.

Tunable electron property induced by B-doping in g-C3N4.

Graphitic carbon nitrides are a research hotspot of two-dimensional (2D) materials, which attract more and more attention from researchers. Topological properties are a focus in graphitic carbon nitrides materials. Using first-principles calculations, we modified the g-C3N4 (formed by tri-s-triazine) by B atoms, proposing a novel two-dimensional monolayer, g-C6N7B, which showed excellent stability verified by positive phono modes, molecular dynamic simulations and mechanical criteria. The valence band and conduction band touch at the Γ point. Interestingly, g-C6N7B is topologically nontrivial, because the valance and conduction band can be gapped by the spin-orbit coupling (SOC) effect associated with robust gapless edge states. Additionally, molecular dynamic simulations indicate that g-C6N7B will still maintain good geometry structure when the temperature is as high as 1500 K. The flexibility of g-C6N7B is confirmed by its elastic constants and Young's moduli. This work opens an avenue for graphitic carbon nitride materials with topological properties.

Structure and photoluminescence of Eu3+ doped Sr2InTaO6 red phosphor with high color purity.

The Eu3+-doped Sr2InTaO6 phosphors were obtained by solid-state reaction method and the phase purity of Sr2InTaO6:Eu3+ samples were investigated by the XRD patterns. The Rietveld refinements were conducted to further obtain crystal structure information and the results indicate Sr2InTaO6:Eu3+ samples crystallized in the monoclinic system with a P 121 space group. The optical band gap of Sr2InTaO6 was calculated to be 3.84 eV by the diffuse reflectance spectra, which are consistent with the result (3.823 eV) of density functional theory. Under 396 nm excitation, the Sr2InTaO6:Eu3+ phosphor showed a red photoluminescence band centered at about 624 nm due to the 5D0 → 7F2 transition. Monitored at 624 nm, the phosphors showed two wide bands from 200 nm to 500 nm, which originated from the charge-transfer band of Eu3+-O2- and f-f transitions of Eu3+ ions. The optimum luminous concentration is 0.12 because of the concentration quenching determined to be a quadrupole-quadrupole interaction. The luminescence decay lifetimes of the Sr2InTaO6:Eu3+ phosphors were milliseconds. Significantly, the temperature-dependent emission spectra of Sr2InTaO6:0.12Eu3+ phosphors exhibited good thermal stability and the CIE chromaticity coordinates of Sr2InTaO6:0.12Eu3+ were (0.6265, 0.3693) with high color purity. The present work demonstrated that the Sr2InTaO6:Eu3+ red-emitting phosphors show great application in lighting technology.

Chromatin 3D structure reconstruction with consideration of adjacency relationship among genomic loci.

BACKGROUND: Chromatin 3D conformation plays important roles in regulating gene or protein functions. High-throughout chromosome conformation capture (3C)-based technologies, such as Hi-C, have been exploited to acquire the contact frequencies among genomic loci at genome-scale. Various computational tools have been proposed to recover the underlying chromatin 3D structures from in situ Hi-C contact map data. As connected residuals in a polymer, neighboring genomic loci have intrinsic mutual dependencies in building a 3D conformation. However, current methods seldom take this feature into account. RESULTS: We present a method called ShNeigh, which combines the classical MDS technique with local dependence of neighboring loci modeled by a Gaussian formula, to infer the best 3D structure from noisy and incomplete contact frequency matrices. We validated ShNeigh by comparing it to two typical distance-based algorithms, ShRec3D and ChromSDE. The comparison results on simulated Hi-C dataset showed that, while keeping the high-speed nature of classical MDS, ShNeigh can recover the true structure better than ShRec3D and ChromSDE. Meanwhile, ShNeigh is more robust to data noise. On the publicly available human GM06990 Hi-C data, we demonstrated that the structures reconstructed by ShNeigh are more reproducible between different restriction enzymes than by ShRec3D and ChromSDE, especially at high resolutions manifested by sparse contact maps, which means ShNeigh is more robust to signal coverage. CONCLUSIONS: Our method can recover stable structures in high noise and sparse signal settings. It can also reconstruct similar structures from Hi-C data obtained using different restriction enzymes. Therefore, our method provides a new direction for enhancing the reconstruction quality of chromatin 3D structures.

Optical properties of a hexagonal C/BN framework with sp2 and sp3 hybridized bonds.

We investigated the optical properties and roles of sp2- and sp3-hybridized bonds of a hexagonal C/BN family using first-principles calculations. The calculated phonon dispersions confirm the dynamic stability of Hex-(BN)6C12 and Hex-C12(BN)6. The complex dielectric function evolves from the infrared to the ultraviolet region and has a significant anisotropy for different polarizations. The reflectivity and refractive index spectra show that the sp2-hybridized C atoms are more sensitive to the light from infrared to visible region than B-N pairs while the C atoms and B-N pairs have a similar sensitivity to high frequencies. The sharp peaks of the energy-loss spectrum are all concentrated in the 23-30 eV energy region, which can be used to identify these hexagonal structures. The calculated band structures show Hex-C24 and Hex-(BN)6C12 are metals, but Hex-C12(BN)6 and Hex-(BN)12 are semiconductors with indirect band gaps of 3.47 and 3.25 eV, respectively. The electronic states near the Fermi level primarily originate from sp2-hybridized atoms. In addition, sp2-hybridized bonds are the main elements affecting the optical and electronic structure of C/BN materials with sp2- and sp3-hybridizations. We expect that the results presented will help understand the optical properties of C/BN materials containing sp2- and sp3-hybridized C atoms and B-N pairs.

Tunable magnetic and half-metallic properties of the two-dimensional electron gas in LaAlO3/SrTiO3(111) heterostructures.

Half-metallic materials have gained a lot of attention because of their unique properties and applications in spintronic devices. Despite the fact that these materials have been studied by several research groups there are very limited studies on their heterostructure (HS) systems. In the current study we have investigated the electronic and magnetic properties of (LaAlO3)6.5/(SrTiO3)2.5(111) HS using density functional theory (DFT) calculations. We demonstrate that the system exhibits a 100% spin-polarized two-dimensional electron gas (2DEG) which is extremely confined to the Ti 3d orbitals of the SrTiO3 layers. In particular, this system can keep its half-metallic properties under different in-plane strains from -3 to 2%. This property proves that this material has relatively stable half-metallic properties. In addition, the conducting and magnetic ground states of the system can also be tailored by changing in-plane strain and interfacial cation intermixing of La and Sr (Sr ⇔ La intermixing). By increasing the in-plane lattice parameters, this system has the ability to evolve from a nonmagnetic to a ferromagnetic metal and then to a half-metal and by further increasing the in-plane lattice parameter it becomes a ferromagnetic insulator. Sr ⇔ La intermixing can destroy the original half-metallic properties and the system exhibits an AFM Mott-type insulator phase. Our results demonstrate that the system has high potential for application in the field of spintronics, and opens the prospect of using LaAlO3/SrTiO3(111) HSs to explore quantum phase transitions.

The role of sp2 and sp3 hybridized bonds on the structural, mechanical, and electronic properties in a hard BN framework.

A first-principles approach is used to systematically investigate the role of sp2 and sp3 hybridized bonds on the structural, mechanical, and electronic properties in a new BN phase (denoted Hex-(BN)12). Hex-(BN)12 has the same number of sp2 and sp3 hybridized atoms. The calculated cohesion energy, phonon frequencies, and elastic constants unambiguously confirm the structural stability of this compound. Due to the different types of hybridization and B-N covalent bonds with ionic characteristics, Hex-(BN)12 has unequal bond lengths and bond angles in these hybrid orbitals. These cause the relative energetic stability to be slightly lower than c-BN and w-BN. The hardness of Hex-(BN)12 is estimated to range from 33 to 40 GPa. The bond-breaking order under stress is sp3-sp3, sp2-sp3, and sp2-sp2. DFT calculations with the gradient approximation (GGA) and HSE06 functional indicate the electronic structure contains an indirect band gap at 3.21 and 4.42 eV, respectively. The electronic states in the region near the Fermi level primarily arise from the 2p orbitals in sp2-hybridized atoms. In general, sp3 bonded B and N atoms guarantee higher mechanical properties, and sp2 bonded atoms ensure ductility and even conductivity, although all changes vary with spatial structure. Hex-(BN)12 can be obtained from multilayer yne-BN, and BN nanosheets, nanotubes and nanoribbons under pressure.

First-principles prediction of a new Dirac-fermion material: silicon germanide monolayer.

From first-principles calculations, we proposed a silicon germanide (SiGe) analog of silicene. This SiGe monolayer is stable and free from imaginary frequency in the phonon spectrum. The electronic band structure near the Fermi level can be characterized by Dirac cones with the Fermi velocity comparable to that of silicene. The Ge and Si atoms in SiGe monolayer exhibit different tendencies in binding with hydrogen atoms, making sublattice-selective hydrogenation and consequently electron spin-polarization possible.

Isoelectronic doping of graphdiyne with boron and nitrogen: stable configurations and band gap modification.

Graphdiyne, consisting of sp- and sp(2)-hybridized carbon atoms, is a new member of carbon allotropes which has a natural band gap ~1.0 eV. Here, we report our first-principles calculations on the stable configurations and electronic structures of graphdiyne doped with boron-nitrogen (BN) units. We show that BN unit prefers to replace the sp-hybridized carbon atoms in the chain at a low doping rate, forming linear BN atomic chains between carbon hexagons. At a high doping rate, BN units replace first the carbon atoms in the hexagons and then those in the chains. A comparison study indicates that these substitution reactions may be easier to occur than those on graphene which composes purely of sp(2)-hybridized carbon atoms. With the increase of BN component, the band gap increases first gradually and then abruptly, corresponding to the transition between the two substitution motifs. The direct-band gap feature is intact in these BN-doped graphdiyne regardless the doping rate. A simple tight-binding model is proposed to interpret the origin of the band gap opening behaviors. Such wide-range band gap modification in graphdiyne may find applications in nanoscaled electronic devices and solar cells.