New 4-imino-4H-Chromeno[2,3-d]Pyrimidin-3(5H)-Amine: Synthesis, Cytotoxic Effects on Tumoral Cell Lines and in Silico ADMET Properties

The synthesis of new 4-imino-4H-chromeno[2,3-d]pyrimidin-3(5H)-amine in four steps including one step under microwave dielectric heating is reported. The structural identity of the synthesized compounds was established according to their spectroscopic analysis, such as FT-IR, NMR and mass spectroscopy. These new compounds were tested for their antiproliferative activities on seven representative human tumoral cell lines (Huh7 D12, Caco2, MDA-MB231, MDA-MB468, HCT116, PC3 and MCF7) and also on fibroblasts. Among them, only the compounds 6c showed micromolar cytotoxic activity on tumor cell lines (1.8 50 50 > 25 μM). Finally, in silico ADMET studies ware performed to investigate the possibility of using of the identified compound 6c as potential anti-tumor compound.

Boosting oxygen reduction activity and CO_(2) resistance on bismuth ferrite-based perovskite cathode for low-temperature solid oxide fuel cells below 600℃

Developing efficient and stable cathodes for low-temperature solid oxide fuel cells(LT-SOFCs) is of great importance for the practical commercialization.Herein,we propose a series of Sm-modified Bi_(0.7-x)Sm_xSr_(0.3)FeO_(3-δ) perovskites as highly-active catalysts for LT-SOFCs.Sm doping can significantly enhance the electrocata lytic activity and chemical stability of cathode.At 600℃,Bi_(0.675)Sm_(0.025)Sr_(0.3)FeO_(3-δ)(BSSF25) cathode has been found to be the optimum composition with a polarization resistance of 0.098 Ω cm^2,which is only around 22.8% of Bi_(0.7)Sr_(0.3)FeO_(3-δ)(BSF).A full cell utilizing BSSF25 displays an exceptional output density of 790 mW cm^(-2),which can operate continuously over100 h without obvious degradation.The remarkable electrochemical performance observed can be attributed to the improved O_(2) transport kinetics,superior surface oxygen adsorption capacity,as well as O_(2)p band centers in close proximity to the Fermi level.Moreover,larger average bonding energy(ABE) and the presence of highly acidic Bi,Sm,and Fe ions restrict the adsorption of CO_(2) on the cathode surface,resulting in excellent CO_(2) resistivity.This work provides valuable guidance for systematic design of efficient and durable catalysts for LT-SOFCs.

First-principles study on the alkali chalcogenide secondary compounds in Cu(In,Ga)Se_2 and Cu_2ZnSn(S,Se)_4 thin film solar cells

The beneficial effect of the alkali metals such as Na and K on the Cu（In.Ga）Se2 （CIGS） and Cu2ZnSn（S,Se）4 （CZTSSe） solar cells has been extensively investigated in the past two decades, however, in most of the studies the alkali metals were treated as dopants. Several recent studies have showed that the alkali metals may not only act as dopants but also form secondary phases in the absorber layer or on the surfaces of the films. Using the first-principles calculations, we screened out the most probable secondary phases of Na and K in CIGS and CZTSSe, and studied their electronic structures and optical properties. We found that all these alkali chalcogenide compounds have larger band gaps and lower VBM levels than CIGS and CZTSSe, because the existence of strong p-d coupling in CIS and CZTS pushes the valence band maximum （VBM） level up and reduces the band-gaps, while there is no such p-d coupling in these alkali chalcogenides. This band alignment repels the photo-generated holes from the secondary phases and prevents the electron-hole recombination. Moreover, the study on the optical properties of the secondary phases showed that the absorption coefficients of these alkali chalcogenides are much lower than those of CIGS and CZTSSe in the energy range of 0-3.4eV, which means that the alkali chalcogenides may not influence the absorption of solar light. Since the alkali metal dopants can passivate the grain boundaries and increase the hole carrier concentration, and meanwhile their related secondary phases have innocuous effect on the optical absorption and band alignment, we can understand why the alkali metal dopants can improve the CIGS and CZTSSe solar cell performance.

Theoretical study on the kesterite solar cells based on Cu_2ZnSn(S,Se)_4 and related photovoltaic semiconductors

The kesterite thin film solar cells based on the quaternary Cu2ZnSnS4 and Cu2ZnSnSe4 and their alloys Cu2ZnSn（S,Se）4 have been considered as environment-friendly and non-toxic alternatives to the currently commercialized CdTe and Cu（In,Ga）Se2 thin film solar cells. From the theoretical point of view, we will review how the group I2-II-IV-VI4 quaternary compound semiconductors are derived from the binary CdTe and the ternary CuInSe2 or CuGaSe2 through the cation mutation, and how the crystal structure and electronic band structure evolve as the component elements change. The increased structural and chemical freedom in these quaternary semiconductors opens up new possibility for the tailoring of material properties and design of new light-absorber semiconductors. However, the increased freedom also makes the development of high-efficiency solar cells more challenging because much more intrinsic point defects, secondary phases, surfaces, and grain-boundaries can exist in the thin films and influence the photovoltaic performance in a way different from that in the conventional CdTe and Cu（In,Ga）Se2 solar cells. The experimental characterization of the properties of defects, secondary phase, and grain-boundaries is currently not very efficient and direct, especially for these quaternary compounds. First-principles calculations have been successfully used in the past decade for studying these properties. Here we will review the theoretical progress in the study of the mixed-cation and mixed-anion alloys of the group I2-II-IV- VI4 semiconductors, defects, alkaline dopants, and grain boundaries, which provided very important information for the optimization of the kesterite solar cell performance.

全黄铜矿CuGaSe_(2)/CuInSe_(2)两端叠层太阳能电池的顶端设计与优化

近年来单结太阳能电池的光电转换效率逐步提高,但其最高效率受到Shockley-Queisser (SQ)极限的限制.为了超越SQ极限,学者们提出了叠层太阳能电池.本工作结合第一性原理计算和SCAPS-1D器件模拟对黄铜矿化合物CuGaSe_(2)/CuInSe_(2)叠层太阳能电池进行了系统的理论研究.首先通过第一性原理计算获取了CuGaSe_(2) (CGS)的微观电子结构、缺陷特性及对应的宏观性能参数,作为后续器件模拟CGS太阳能电池的输入参数.随后采用SCAPS-1D软件分别对单结CGS与CuInSe_(2) (CIS)太阳能电池进行了仿真模拟.单结CIS太阳能电池的模拟结果与实验值具有良好的一致性.对单结CGS电池而言,在短路电流(J_(sc))最高的生长环境下进一步模拟发现,将电子传输层(ETL)换为ZnSe后可提高CGS太阳能电池的开路电压(V_(oc))和PCE.最后,将优化后的CGS与CIS太阳能电池进行了两端(2T)单片串联的器件模拟,结果显示在生长环境为富Cu、富Ga、贫Se,生长温度为700 K时,2T单片CGS/CIS叠层太阳能电池的PCE最高为28.91%,高于当前最高的单结太阳能电池效率,展现出良好的应用前景.

天冬氨酸和谷氨酸及其甘氨酸二肽调控Caco-2细胞钙离子吸收的研究

为了探究天冬氨酸和谷氨酸及其甘氨酸二肽对钙离子吸收的影响机理,本文利用等温滴定量热技术、电化学、Caco-2细胞模型结合量子化学计算(密度泛函理论)对天冬氨酸和谷氨酸及其甘氨酸二肽与钙离子的相互作用进行了探究。结果表明,天冬氨酸和谷氨酸通过焓和熵驱动的放热反应与钙离子形成复合物,而其形成的二肽则是通过熵驱动的吸热反应与钙离子结合。此外,二肽比单独的氨基酸表现出更强的钙离子结合能力。量子化学计算表明,氨基酸/二肽中的羧基为钙离子的主要结合位点,在碱性条件下,会导致钙离子结合位点转移,氨基也可以参与钙离子结合。Caco-2细胞吸收实验表明,天冬氨酸和谷氨酸及其二肽均可促进钙的吸收,其中甘氨酸-谷氨酸二肽(Gly-Glu)的促进效果最好,促钙吸收率为1.33±0.115。此外,促钙吸收能力与钙离子结合能力之间没有明确的相关性,与其电子亲和力的关系更为密切。研究结果解释了天冬氨酸、谷氨酸及其甘氨酸二肽与钙之间的相互作用,为进一步开发钙补充剂提供科学依据。

Wire-in-Wire TiO_(2)/C Nanofibers Free-Standing Anodes for Li-Ion and K-Ion Batteries with Long Cycling Stability and High Capacity

Wearable and portable mobile phones play a critical role in the market, and one of the key technologies is the flexible electrode with high specific capacity and excellent mechanical flexibility. Herein, a wire-in-wire TiO_(2)/C nanofibers (TiO_(2) ww/CN) film is synthesized via electrospinning with selenium as a structural inducer. The interconnected carbon network and unique wire- in-wire nanostructure cannot only improve electronic conductivity and induce effective charge transports, but also bring a superior mechanic flexibility. Ulti-mately, TiO_(2) ww/CN film shows outstanding electrochemical performance as free-standing electrodes in Li/K ion batteries. It shows a discharge capacity as high as 303 mAh g^(−1) at 5 A g^(−1) after 6000 cycles in Li half-cells, and the unique structure is well-reserved after long-term cycling. Moreover, even TiO_(2) has a large diffusion barrier of K^(+), TiO_(2) ww/CN film demonstrates excellent perfor-mance (259 mAh g^(−1) at 0.05 A g^(−1) after 1000 cycles) in K half-cells owing to extraordinary pseudocapacitive contribution. The Li/K full cells consisted of TiO_(2) ww/CN film anode and LiFePO_(4)/Perylene-3,4,9,10-tetracarboxylic dianhydride cathode possess outstanding cycling stability and demonstrate practical application from lighting at least 19 LEDs. It is, therefore, expected that this material will find broad applications in portable and wearable Li/K-ion batteries.

Model-guided design of a high performance and durability Ni nanofiber/ceria matrix solid oxide fuel cell electrode

Mixed ionic electronic conductors(MIECs)have attracted increasing attention as anode materials for solid oxide fuel cells(SOFCs)and they hold great promise for lowering the operation temperature of SOFCs.However,there has been a lack of understanding of the performance-limiting factors and guidelines for rational design of composite metal-MIEC electrodes.Using a newly-developed approach based on 3 D-tomography and electrochemical impedance spectroscopy,here for the first time we quantify the contribution of the dual-phase boundary(DPB)relative to the three-phase boundary(TPB)reaction pathway on real MIEC electrodes.A new design strategy is developed for Ni/gadolinium doped ceria(CGO)electrodes(a typical MIEC electrode)based on the quantitative analyses and a novel Ni/CGO fiber-matrix structure is proposed and fabricated by combining electrospinning and tape-casting methods using commercial powders.With only 11.5 vol%nickel,the designer Ni/CGO fiber-matrix electrode shows 32%and 67%lower polarization resistance than a nano-Ni impregnated CGO scaffold electrode and conventional cermet electrode respectively.The results in this paper demonstrate quantitatively using real electrode structures that enhancing DPB and hydrogen kinetics are more efficient strategies to enhance electrode performance than simply increasing TPB.

Toxicity testing of four silver nanoparticle-coated dental castings in 3-D LO2 cell cultures

To address the controversial issue of the toxicity of dental alloys and silver nanoparticles in medical ap- plications, an in vivo-like LO2 3-D model was constructed within polyvinylidene fluoride hollow fiber materials to mimic the microenvironment of liver tissue. The use of microscopy methods and the measurement of liver-specific functions optimized the model for best cell performances and also proved the superiority of the 3-D LO2 model when compared with the traditional monolayer model. Toxicity tests were conducted using the newly constructed model, finding that four dental castings coated with silver nanoparticles were toxic to human hepatocytes after cell viability assays. In general, the toxicity of both the castings and the coated silver nanoparticles aggravated as time increased, yet the nanoparticles attenuated the general toxicity by preventing metal ion release, especially at high concentrations.

CALCULATIONS OF RIEMANN PROBLEMS FOR 2-D SCALAR CONSERVATION LAWS BY SECOND ORDER ACCURATE MmB SCHEME

Numerical solutions of Riemann problems for 2-D scalar conservation law are given by a second order accurate MmB (locally Maximum-minimum Bounds preserving) scheme which is non-splitting. The numerical computations show that the scheme has high resolution and non-oscillatory properties. The results are completely in accordance with the theoretical solutions and all cases are distinguished efficiently

通用河网二维水流模拟模式研究

通过对流域河网二维水流模拟问题的分析,提出了一个通用化的河网二维模拟概化模式,该模式将河网二维概化为"树状"河道计算单元、"环状"河道计算单元、"十字型"河道计算单元等河网二维基本单元,对这些河道计算单元的求解,构建流域型河网一二维耦合模式的求解模型,并由此建立了通用化的河网二维水流数学模型软件系统。通过"树状"河道二维计算单元求解模型的推导与实现,验证了概化模式的可行性,表明该思路可以应用于大型流域河网一、二维水流模拟,具有很好的应用推广价值。

Effects of guanidinium cations on structural,optoelectronic and photovoltaic properties of perovskites

Guanidinium(GA)cations are intentionally introduced in MAPbI_(3) perovskite by considering its potential capability of stabilizing the material through plenty of hydrogen bonds and mitigating hysteresis because of the zero dipole moment.The configurations of GA cation in film and its effects on structural,optoelectronic and photovoltaic properties of perovskite have been comprehensively studied by systematically modulating the GA ratio.It has been demonstrated that moderate GA cations can effectively passivate the defect surrounding perovskite grains,yielding an enhanced efficiency as high as~19,2%in a p-i-n type planar solar cells with the GA ratio of 15%.Further increasing the GA ratio deteriorates device performance,as extra GA cations hinder grain growth and thus reduce the grain size,which facilitates the defect generation around the enhanced interface.Moreover,a new two-dimensional(2 D)layered perovskite phase that features alternating GA and MA cations in the interlayer space(ACI)appears ultimately,while the ACI phase typically suffers from slow charge transportation across the parallel PbI2 octahedral layers separated by large A-site cations.

Hydrolysis mechanism of YbB_(2)C_(2)and the microstructure of the carbon derived from the hydrolysis reaction

Carbide-derived carbon(CDC)materials have gained great attention due to the excellent properties for various potential applications.Here,graphite crystal is formed during a room-temperature hydrolysis pro-cess of layered compound YbB_(2)C_(2).The formation mechanism can be demonstrated by a YbB_(2)C_(2)molecular cell:Yb^(3+)acts as a cathode where H_(2)O molecule is reduced to H atom and OH^(−)ion,while(B_(2)C_(2))^(3−)acts as an anode where OH−ion is oxidized to O atom.Then,YbB_(2)C_(2)molecular cell begins to disintegrate,i.e.,Yb^(3+)ion,B and C atoms dissociate from the molecular cell.The as-produced C atoms combine to form graphite crystal.The initial graphite crystal is a cabbage-like microsphere,and then it gradually disintegrates and transforms into layered graphite.In addition,YbB_(6),Yb_(3)(OH)_(3)n(BO_(3))_((3-n))sol,hydrogen,hydrocarbons,and carbon oxides form simultaneously.Our method provides a general and inexpensive route to obtain carbide-derived graphite crystal.

A series of dithienobenzodithiophene based small molecules for highly efficient organic solar cells

Three acceptor-donor-acceptor （A-D-A） small molecules DCAODTBDT, DRDTBDT and DTBDTBDT using dithieno[2,3-d：2＇,3＇-d＇]benzo[1,2-b：4,5-b＇]dithiophene as the central building block, octyl cyanoacetate, 3-octylrhodanine and thiobarbituric acid as the end groups were designed and synthesized as donor materials in solution-processed photovoltaic cells （OPVs）. The impacts of these different electron withdrawing end groups on the photophysical properties, energy levels, charge carrier mobility, morphologies of blend films, and their photovoltaic properties have been systematically investigated. OPVs device based on DRDTBDT gave the best power conversion efficiency （PCE） of 8.34%, which was significantly higher than that based on DCAODTBDT （4.83%） or DTBDTBDT （3.39%）. These results indicate that rather dedicated and balanced consideration of absorption, energy levels, morphology, mobility, etc. for the design of small-molecule-based OPVs （SM-OPVs） and systematic investigations are highly needed to achieve high performance for SM-OPVs.