不同pH条件下硫化钼纳米片吸附Cd(Ⅱ)的微观机制研究

本研究结合静态实验和X射线吸收精细结构谱学(EXAFS)评估了硫化钼纳米片对重金属Cd(Ⅱ)的吸附行为和微观机制。结果表明:Cd(Ⅱ)在硫化钼纳米片上的吸附受溶液pH、反应时间和温度的显著影响,但不受离子强度的影响。在pH 3.3~9.6范围内, pH升高显著促进了硫化钼对Cd(Ⅱ)的吸附量,但不改变吸收速率、吸附等温线和热力学。二级动力学模型能更好地拟合该吸附平衡,且内表面颗粒扩散模型显示了吸附过程中的三个典型阶段。等温线和热力学分析说明Cd(Ⅱ)在硫化钼上的吸附是异质性的、自发的、吸热的和不可逆的过程。EXAFS光谱学分析揭示了该吸附存在两种类型:在较低的pH(3.56,6.48)条件下,内表面络合以Cd–S配位键为主;在较高的pH(9.57)条件下,出现Cd(OH)2沉淀,且配位键以Cd–O和Cd–Cd的形式存在。这些研究结果对于评估重金属离子和硫化钼纳米片在分子水平上的作用机理提供了新的视野。

Plasma-induced grafting of acrylic acid on bentonite for the removal of U(VI) from aqueous solution

Fabrication of reusable adsorbents with satisfactory adsorption capacity and using environmentfriendly preparation processes is required for the environment-related applications. In this study,acrylic acid（AA） was grafted onto bentonite（BT） to generate an AA-graft-BT（AA-g-BT）composite using a plasma-induced grafting technique considered to be an environment-friendly method. The as-prepared composite was characterized by scanning electron microscopy, x-ray powder diffraction, thermal gravity analysis, Fourier transform infrared spectroscopy and Barrett–Emmett–Teller analysis, demonstrating the successful grafting of AA onto BT. In addition, the removal of uranium（VI）（U（VI）） from contaminated aqueous solutions was examined using the as-prepared composite. The influencing factors, including contact time,p H value, ionic strength, temperature, and initial concentration, for the removal of U（VI） were investigated by batch experiments. The experimental process fitted best with the pseudo-secondorder kinetic and the Langmuir models. Moreover, thermodynamic investigation revealed a spontaneous and endothermic process. Compared with previous adsorbents, AA-g-BT has potential practical applications in treating U（VI）-contaminated solutions.

EXISTENCE AND UNIQUENESS OF SOLUTIONS FOR NONLINEAR FRACTIONAL DIFFERENTIAL EQUATIONS WITH NON-SEPARATED TYPE INTEGRAL BOUNDARY CONDITIONS

In this paper, we study a boundary value problem of nonlinear fractional dif- ferential equations of order q （1 〈 q 〈 2） with non-separated integral boundary conditions. Some new existence and uniqueness results are obtained by using some standard fixed point theorems and Leray-Schauder degree theory. Some illustrative examples are also presented. We extend previous results even in the integer case q = 2.

DYNAMICAL BEHAVIOR OF A STOCHASTIC HBV INFECTION MODEL WITH LOGISTIC HEPATOCYTE GROWTH

This paper is concerned with a stochastic HBV infection model with logistic growth. First, by constructing suitable stochastic Lyapunov functions, we establish sufficient conditions for the existence of ergodic stationary distribution of the solution to the HBV infection model. Then we obtain sufficient conditions for extinction of the disease. The stationary distribution shows that the disease can become persistent in vivo.

QUALITATIVE ANALYSIS OF A STOCHASTIC RATIO-DEPENDENT HOLLING-TANNER SYSTEM

This article addresses a stochastic ratio-dependent predator-prey system with Leslie-Gower and Holling type II schemes. Firstly, the existence of the global positive solution is shown by the comparison theorem of stochastic differential equations. Secondly, in the case of persistence, we prove that there exists a ergodic stationary distribution. Finally, numerical simulations for a hypothetical set of parameter values are presented to illustrate the analytical findings.

Features of Darcy-Forchheimer flow of carbon nanofluid in frame of chemical species with numerical significance

Present work reports chemically reacting Darcy-Forchheimer flow of nanotubes.Water is utilized as base liquid while carbon nanotubes are considered nanomaterial.An exponential stretchable curved surface flow is originated.Heat source is present.Xue relation of nanoliquid is employed to explore the feature of CNTs (single and multi-wall).Transformation technique is adopted in order to achieve non-linear ordinary differential systems.The governing systems are solved numerically.Effects of involved parameters on flow,temperature,concentration,heat transfer rate (Nusselt number) with addition of skin friction coefficient are illustrated graphically.Decay in velocity is noted with an increment in Forchheimer number and porosity parameter while opposite impact is seen for temperature.Moreover,role of MWCNTs is prominent when compared with SWCNTs.

Improving the performance of arylamine-based hole transporting materials in perovskite solar cells： Extending π-conjugation length or increasing the number of side groups？

In this work, we prepared three simple arylamine-based hole transporting materials from commercially available starting materials. The effect of extending z-conjugation length or increasing the number of side groups compared with reference compound on the photophysical, electrochemical, hole mobility properties and performance in perovskite solar cells were further studied. It is noted that these two kinds of molecular modifications can significantly lower the HOMO level and improve the hole mobility, thus improving the hole injection from valence band of perovskite. On the other hand, the compound with more side groups showed higher hole injection efficiency due to lower HOMO level and higher hole mo- bility compared with the compound with extending π-conjugation length. The perovskite solar cells with the modified molecules as hole transporting materials showed a higher efficiency of 15.40% and 16.95%, respectively, which is better than that of the reference compound （13.18%）. Moreover, the compound with increasing number of side groups based devices showed comparable photovoltaic performance with that of conventional spiro-OMeTAD （16.87%）.

A STUDY OF A FULLY COUPLED TWO-PARAMETER SYSTEM OF SEQUENTIAL FRACTIONAL INTEGRO-DIFFERENTIAL EQUATIONS WITH NONLOCAL INTEGRO-MULTIPOINT BOUNDARY CONDITIONS

In this article, we discuss the existence and uniqueness of solutions for a coupled two-parameter system of sequential fractional integro-differential equations supplemented with nonlocal integro-multipoint boundary conditions. The standard tools of the fixed-point theory are employed to obtain the main results. We emphasize that our results are not only new in the given configuration, but also correspond to several new special cases for specific values of the parameters involved in the problem at hand.

Analytic solution for magnetohydrodynamic boundary layer flow of Casson fluid over a stretching/shrinking sheet with wall mass transfer

In this analysis,the magnetohydrodynamic boundary layer flow of Casson fluid over a permeable stretching/shrinking sheet in the presence of wall mass transfer is studied.Using similarity transformations,the governing equations are converted to an ordinary differential equation and then solved analytically.The introduction of a magnetic field changes the behavior of the entire flow dynamics in the shrinking sheet case and also has a major impact in the stretching sheet case.The similarity solution is always unique in the stretching case,and in the shrinking case the solution shows dual nature for certain values of the parameters.For stronger magnetic field,the similarity solution for the shrinking sheet case becomes unique.

Entropy optimization in cubic autocatalysis chemical reactive flow of Williamson fluid subjected to viscous dissipation and uniform magnetic field

This research elaborates magnetohydrodynamics (MHD) impact on non-Newtonian (Williamson) fluid flow by stretchable rotating disks.Both disks are rotating with different angular velocities and different stretching rates.Viscous dissipation aspect is considered for energy expression formulation.Entropy generation analysis is described via implementation of thermodynamic second law.Chemical processes (heterogeneous and homogeneous) subjected to entropy generation are introduced first time in literature.Boundary-layer approach is employed for modeling.Apposite variables are introduced for non-dimensionalization of governing systems.Homotopy procedure yields convergence of solutions subjected to computations of highly nonlinear expressions.The significant characteristics of sundry factors against thermal,velocity and solutal fields are described graphically.Besides,tabular results are addressed for engineering quantities (skin-friction coefficient,Nusselt number).The outcomes certify an increment in temperature distribution for Weissenberg (We) and Eckert (Ec) numbers.

Dual solutions in boundary layer flow of Maxwell fluid over a porous shrinking sheet

An analysis is carried out for dual solutions of the boundary layer flow of Maxwell fluid over a permeable shrinking sheet. In the investigation, a constant wall mass transfer is considered. With the help of similarity transformations, the governing partial differential equations（PDEs） are converted into a nonlinear self-similar ordinary differential equation（ODE）. For the numerical solution of transformed self-similar ODE, the shooting method is applied. The study reveals that the steady flow of Maxwell fluid is possible with a smaller amount of imposed mass suction compared with the viscous fluid flow. Dual solutions for the velocity distribution are obtained. Also, the increase of Deborah number reduces the boundary layer thickness for both solutions.

Ternary blend strategy in benzotriazole-based organic photovoltaics for indoor application

Organic photovoltaics(OPVs)suitable for application in indoor lighting environments can power a wide range of internet of things(Io T)related electronic devices.The ternary structure has huge advantages in improving the photovoltaic performance of OPVs,including broadening the light absorption,improving the charge transport,manipulating the energy loss(E_(loss))and so on.Herein,we use wide-bandgap photo-active materials,including the benzotriazole-based polymer donor(J52-F),chlorinated polymer donor(PM7)and A_(2)-A_1-D-A_1-A_(2)-structured acceptor(BTA3),to construct ternary OPVs for indoor light applications.Benefitting from the introduction of PM7 as the third component in J52-F:BTA3-based blend,a gratifying PCE of 20.04%with a high V_(OC)of 1.00 V can be obtained under the test conditions with an illumination of 300 lx from an LED lighting source with a color temperature of 3000 K.The excellent device performance is inseparable from the matched spectrum,enhanced light absorption and the reduced E_(loss),while the improved charge transport capability and suppression of carrier recombination also play an indelible role.Our work shows a potential material system to meet the requirement of devices applied under indoor light.Moreover,these findings demonstrate that designing multi-component OPVs is indeed a feasible way to further improve the performances of the photovoltaic energy conversion system for indoor applications.

Numerical treatment for Darcy-Forchheimer flow of carbon nanotubes due to an exponentially stretching curved surface

This article gives a numerical report to two dimensional(2D)Darcy-Forchheimer flow of carbon-water nanofluid.Flow is instigated by exponential extending curved surface.Viscous liquid in permeable space is described by Darcy-Forchheimer.The subsequent arrangement of partial differential equations is changed into ordinary differential framework through proper transformations.Numerical arrangements of governing frameworks are set up by NDSolve procedure.Outcomes of different sundry parameters on temperature and velocity are examined.Skin friction and heat transfer rate are also shown and inspected.

ON A COUPLED INTEGRO-DIFFERENTIAL SYSTEM INVOLVING MIXED FRACTIONAL DERIVATIVES AND INTEGRALS OF DIFFERENT ORDERS

By applying the standard fixed point theorems,we prove the existence and uniqueness results for a system of coupled differential equations involving both left Caputo and right Riemann-Liouville fractional derivatives and mixed fractional integrals,supplemented with nonlocal coupled fractional integral boundary conditions.An example is also constructed for the illustration of the obtained results.

Numerical simulation for Darcy-Forchheimer 3D rotating flow subject to binary chemical reaction and Arrhenius activation energy

Three-dimensional Darcy-Forchheimer nanoliquid flow in the presence of rotating frame and activation energy is inspected.Flow is developed through linearly stretching of the surface.Convection of heat and mass exchange is given due consideration.The novel characteristics in regards to Brownian dispersion and thermophoresis are retained.The variation in partial differential framework (PDEs) to nonlinear ordinary differential framework (ODEs) is done through reasonable transformations.Governing differential frameworks have been computed in edge of NDSolve.Discussion regarding thermal field and concentration distribution for several involved parameters is pivotal part.Physical amounts like surface drag coefficients,transfer of heat and mass rates are portrayed by numeric esteems.It is noticed that impacts of porosity parameter and Forchheimer number on the thermal and concentration fields are quite similar.Both temperature and associated thermal layer thickness are enhanced for larger porosity parameter and Forchheimer number.Temperature and concentration fields exhibit similar trend for the higher values of rotational parameter.Effects of thermal and concentration Biot numbers on the temperature and concentration fields are qualitatively similar.Higher Prandtl and Schmidt numbers correspond to stronger temperature and concentration fields.Larger nondimensional activation energy,temperature difference parameter and fitted rate constant yield weaker concentration field.Brownian motion parameter for temperature and concentration has reverse effects while similar trend is observed via thermophoresis parameter.

Three-dimensional flow of Powell–Eyring nanofluid with heat and mass flux boundary conditions

This article investigates the three-dimensional flow of Powell–Eyring nanofluid with thermophoresis and Brownian motion effects. The energy equation is considered in the presence of thermal radiation. The heat and mass flux conditions are taken into account. Mathematical formulation is carried out through the boundary layer approach. The governing partial differential equations are transformed into the nonlinear ordinary differential equations through suitable variables. The resulting nonlinear ordinary differential equations have been solved for the series solutions. Effects of emerging physical parameters on the temperature and nanoparticles concentration are plotted and discussed. Numerical values of local Nusselt and Sherwood numbers are computed and examined.

低温等离子体改性碳纳米管及其对U(Ⅵ)的吸附性能研究

采用低温等离子体法将O-磷酸乙醇胺(O-PEA)接枝到多壁碳纳米管表面(MWCNTs),并使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FTIR)、X射线衍射(XRD)和拉曼光谱(Raman)表征改性前后的MWCNTs的物化性质.通过静态吸附实验研究改性碳纳米管对溶液中U(Ⅵ)的吸附容量,同时,还研究了吸附时间、pH、离子强度和温度对吸附性能的影响.结果表明,通过低温等离子体法改性后的MWCNTs(PTMWCNTs-4)对U(Ⅵ)的吸附性能最好,其吸附容量大约是未改性MWCNTs吸附量的3倍.改性后的MWCNTs吸附速率更快. PTMWCNTs-4对U(Ⅵ)的吸附在pH<7.0条件下不受离子强度影响,属于内层络合机理;而在pH>7.0条件下受离子强度影响,属于外层络合机理或离子交换.热力学数据表明,吸附过程放热且可自发进行.本文为U(Ⅵ)的有效去除提供了一种新型环保的改性方法.

Two-dimensional organic-inorganic hybrid perovskite: from material properties to device applications

The two-dimensional（2D） perovskite（including pure-2D and quasi-2D） is formed by introducing large-group ammonium halides into conventional bulk perovskite. In the past twenty years, 2D perovskite materials were widely developed with the enriched species and advanced physicalknowledge in material characteristics as well as optoelectronic device applications. To review achievments in 2D perovskite,the fundamental mechanism and properties of 2D perovskite are introduced to offer insight into device performance.Moreover, the preparation methods of 2D perovskite films are summarized and compared. The latest successful applications of the 2D perovskite in the solar cells and light-emitting diodes fields, especially the advanced stability of 2D perovskite solar cells（PeSCs） and the efficient 2D perovskite lightemitting diodes（PeLEDs）, are also achieved. Furthermore, the challenges and outlook of 2D perovskite materials are proposed.

New-type highly stable 2D/3D perovskite materials:the effect of introducing ammonium cation on performance of perovskite solar cells

Perovskite solar cells(PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into(FAPbI3)0.85(MAPbBr3)0.15(FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)2.4(FA)n-1PbnI3n+1.4]0.85(MAPbBr3)0.15(n=3, 5, 7, 9 and 11)(A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts;A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency(PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.

Advanced partial nucleation for single-phase FA0.92MA0.08PbI3-based high-efficiency perovskite solar cells

To date, extensive research has been carried out,with considerable success, on the development of highperformance perovskite solar cells(PSCs). Owing to its wide absorption range and remarkable thermal stability, the mixedcation perovskite FAxMA1-xPbI3(formamidinium/methylammonium lead iodide) promises high performance. However, the ratio of the mixed cations in the perovskite film has proved difficult to control with precursor solution. In addition, the FAxMA1-xPbI3 films contain a high percentage of MA+and suffer from serious phase separation and high trap states, resulting in inferior photovoltaic performance. In this study, to suppress phase separation, a post-processing method was developed to partially nucleate before annealing, by treating the as-prepared intermediate phase FAI-Pb I2-DMSO(DMSO: dimethylsulfoxide) with mixed FAI/MAI solution. It was found that in the final perovskite, FA0.92MA0.08 PbI3, defects were substantially reduced because the analogous molecular structure initiated ion exchange in the post-processed thin perovskite films, which advanced partial nucleation. As a result, the increased light harvesting and reduced trap states contributed to the enhancement of open-circuit voltage and short-circuit current. The PSCs produced by the post-processing method presented reliable reproducibility, with a maximum power conversion efficiency of 20.80% and a degradation of ~30% for 80 days in standard atmospheric conditions.