States of graphene oxide and surface functional groups amid adsorption of dyes and heavy metal ions

Water pollution regarding dyes and heavy metal ions is crucial facing the world.How to effectively separate these contaminants from water has been a key issue.Graphene oxide(GO)promises the greenwater world as a long-lasting spotlight adsorbent material and therefore,harnessing GO has been the research hotspot for over a decade.The state of GO as well as its surface functional groups plays an important role in adsorption.And the way of preparation and structural modification matters to the performance of GO.In this review,the significance of the state of existence of stock GO and surface functional groups is explored in terms of preparation,structural modification,and adsorption.Besides,various adsorbates for GO adsorption are also involved,the discussion of which is rarely established elsewhere.

Multiple surface states,nontrivial band topology,and antiferromagnetism in GdAuAl_(4)Ge_(2)

Magnetic topological states of matter provide a fertile playground for emerging topological physics and phenomena.The current main focus is on materials whose magnetism stems from 3d magnetic transition elements,e.g.,MnBi_(2)Te_(4),Fe_(3)Sn_(2),and Co_(3)Sn_(2)S_(2).In contrast,topological materials with the magnetism from rare earth elements remain largely unexplored.Here we report rare earth antiferromagnet GdAuAl_(4)Ge_(2)as a candidate magnetic topological metal.Angle resolved photoemission spectroscopy(ARPES)and first-principles calculations have revealed multiple bulk bands crossing the Fermi level and pairs of low energy surface states.According to the parity and Wannier charge center analyses,these bulk bands possess nontrivial Z2 topology,establishing a strong topological insulator state in the nonmagnetic phase.Furthermore,the surface band pairs exhibit strong termination dependence which provides insight into their origin.Our results suggest GdAuAl_(4)Ge_(2)as a rare earth platform to explore the interplay between band topology,magnetism and f electron correlation,calling for further study targeting on its magnetic structure,magnetic topology state,transport behavior,and microscopic properties.

Analyzing the surface passivity effect of germanium oxynitride:a comprehensive approach through first principles simulation and interface state density

High-purity germanium(HPGe)detectors,which are used for direct dark matter detection,have the advantages of a low threshold and excellent energy resolution.The surface passivation of HPGe has become crucial for achieving an extremely low energy threshold.In this study,first-principles simulations,passivation film preparation,and metal oxide semiconductor(MOS)capacitor characterization were combined to study surface passivation.Theoretical calculations of the energy band structure of the -H,-OH,and -NH_(2) passivation groups on the surface of Ge were performed,and the interface state density and potential with five different passivation groups with N/O atomic ratios were accurately analyzed to obtain a stable surface state.Based on the theoretical calculation results,the surface passivation layers of the Ge_(2)ON_(2) film were prepared via magnetron sputtering in accordance with the optimum atomic ratio structure.The microstructure,C-V,and I-V electrical properties of the layers,and the passivation effect of the Al/Ge_(2)ON_(2)/Ge MOS were characterized to test the interface state density.The mean interface state density obtained by the Terman method was 8.4×10^(11) cm^(-2) eV^(-1).The processing of germanium oxynitrogen passivation films is expected to be used in direct dark matter detection of the HPGe detector surface passivation technology to reduce the detector leakage currents.

Scattering Resonance States and Partial Potential Energy Surface of Reaction I+HI(v=0)→IH(v′=0) +I

The partial potential energy surface of the I ＋ HI →IH ＋ I reaction involving the translational and vibrational motions has been constructed at the QCISD（ T ）//MP4SDQ level with the pseudo potential method that is helpful to interpreting the scattering resonance states. The lifetimes of the scattering resonance states in the title reaction obtained from the partial potential energy surface are about 90-120 fs, which agrees with the result of high-resolved threshold photodetachment spectroscopy of anion IHI^- measured by Neumark.

Vortex bound states influenced by the Fermi surface anisotropy

The spatial distribution of vortex bound states is often anisotropic,which is correlated with the underlying property of materials.In this work,we examine the effects of Fermi surface anisotropy on vortex bound states.The large-scale calculation of vortex bound states is introduced in the presence of fourfold or twofold Fermi surface by solving the Bogoliubov–de Gennes(BdG)equations.Two kinds of quasiparticles’behaviors can be extracted from the local density of states(LDOS)around a vortex.The angle-dependent quasiparticles will move from high energy to low energy when the angle varies from curvature maxima to minima of the Fermi surface,while the angle-independent quasiparticles tend to stay at a relatively higher energy.In addition,the weight of angle-dependent quasiparticles can be enhanced by the increasing anisotropy degree of Fermi surface.

Theoretical Research on Scattering Resonance States of Reaction I＋HI（v=O）→IH（v＇=0）＋I： Partial Potential Energy Surface and One-dimensional Quantum Reactive Scattering Calculation

把最小的精力反应路径基于结合的震动的潜在的曲线，反应 I+HIIH+I 的部分势能表面在 QCISD (T) 被构造 // 有假潜力的 MP4SDQ 水平方法。并且散布回声的形成机制这声明反应很好与部分势能表面被解释。因为联合震动的模式和翻译模式，这反应的散布回声状态应该属于 Feshbach 回声。与一个维的方形的潜在的井模型，回声宽度和 I+HI (=0 ) IH 的一生一起(“ =0 )+I state-to-state 反应被计算，它最好解释 IHI 阴离子的解决高度的阀值 photodetachment 光谱学由 Neumark 等表现了……

Passivation of PEA^(+)to CsPbI_(3)(110)Surface States:From the First Principles Calculations

This work investigates the effect of passivation on the electronic properties of inorganic perovskite CsPbI_(3)materials by using first-principles calculations with density functional theory(DFT).The passivation effect after the addition of Phenylethylamine(PEA+)molecule to CsPbI_(3)(110)surface is studied.The results of density of states(DOS)calculations show that the CsPbI_(3)(110)surface model with I atom terminated reveals new electronic DOS peaks(surface states)near the Fermi level.These surface states are mainly due to the contribution of I-5p orbital and are harmful to the CsPbI_(3)-based solar cells because they reduce the photoelectric conversion efficiency.The surface states near the Fermi level are significantly reduced,and the decline rate reaches 38.8%with the addition with PEA+molecule to the CsPbI3(110)surface.

XPS Analysis of Surface and Interface States for PTC DA/ p-Si Heterojunction

The surface and interface of heterojunction (HJ) formed with organic semiconductor (3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)) and inorganic semiconductor p-Si were measured and analyzed by X-ray photoelectron spectroscopy (XPS).The results indicate that, in PTCDA molecule,the binding energy ( E b) of C is 284.6 eV and 288.3 eV, corresponding to C of the perylene and C of the anhydride, respectively, and the binding energy of O is 531.3 eV and 531.1 eV, corresponding to C of C=O in the anhydrides and C of C-O-C, respectively. Moreover, PTCDA lost its anhydrides and only its perylenes were left in the HJ interface.

Electronic structure, Dirac points and Fermi arc surface states in three-dimensional Dirac semimetal Na_3Bi from angle-resolved photoemission spectroscopy

The three-dimensional（3D） Dirac semimetals have linearly dispersive 3D Dirac nodes where the conduction band and valence band are connected. They have isolated 3D Dirac nodes in the whole Brillouin zone and can be viewed as a 3D counterpart of graphene. Recent theoretical calculations and experimental results indicate that the 3D Dirac semimetal state can be realized in a simple stoichiometric compound A3Bi（A = Na, K, Rb）. Here we report comprehensive high-resolution angle-resolved photoemission（ARPES） measurements on the two cleaved surfaces,（001） and（100）, of Na3Bi. On the（001） surface, by comparison with theoretical calculations, we provide a proper assignment of the observed bands, and in particular, pinpoint the band that is responsible for the formation of the three-dimensional Dirac cones. We observe clear evidence of 3D Dirac cones in the three-dimensional momentum space by directly measuring on the kx–ky plane and by varying the photon energy to get access to different out-of-plane kzs. In addition, we reveal new features around the Brillouin zone corners that may be related with surface reconstruction. On the（100） surface, our ARPES measurements over a large momentum space raise an issue on the selection of the basic Brillouin zone in the（100） plane. We directly observe two isolated 3D Dirac nodes on the（100） surface. We observe the signature of the Fermi-arc surface states connecting the two 3D Dirac nodes that extend to a binding energy of ~150 me V before merging into the bulk band. Our observations constitute strong evidence on the existence of the Dirac semimetal state in Na3Bi that are consistent with previous theoretical and experimental work. In addition, our results provide new information to clarify on the nature of the band that forms the3 D Dirac cones, on the possible formation of surface reconstruction of the（001） surface, and on the issue of basic Brillouin zone selection for the（100） surface.

First principles calculations the Cu surface states of relationship between and relaxations

In this paper the relationship between the surface relaxations and the electron density distributions of surface states of Cu（100）, Cu（110）, and Cu（111） surfaces is obtained by first-principles calculations. The calculations indicate that relaxations mainly occur in the layers at which the surface states electrons are localized, and the magnitudes of the multilayer relaxations correspond to the difference of electron density of surface states between adjacent layers. The larger the interlayer relaxation is, the larger the difference of electron density of surface states between two layers is.

Electronic structure and defect states of transition films from amorphous to microcrystalline silicon studied by surface photovoltage spectroscopy

In this paper, surface photovoltage spectroscopy （SPS） is used to determine the electronic structure of the hydrogenated transition Si films. All samples are prepared by using helicon wave plasma-enhanced chemical vapour deposition technique, the films exhibit a transition from the amorphous phase to the microcrystalline phase with increasing temperature. The film deposited at lower substrate temperature has the amorphous-like electronic structure with two types of dominant defect states corresponding to the occupied Si dangling bond states （D^0/D^-） and the empty Si dangling states （D＋）. At higher substrate temperature, the crystallinity of the deposited films increases, while their band gap energy decreases. Meanwhile, two types of additional defect states is incorporate into the films as compared with the amorphous counterpart, which is attributed to the interface defect states between the microcrystalline Si grains and the amorphous matrix. The relative SPS intensity of these two kinds of defect states in samples deposited above 300℃ increases first and decreases afterwards, which may be interpreted as a result of the competition between hydrogen release and crystalline grain size increment with increasing substrate temperature.

Path-Following Control With Obstacle Avoidance of Autonomous Surface Vehicles Subject to Actuator Faults

This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles inevitably suffer from actuator faults in complex sea environments,which may cause existing obstacle avoidance strategies to fail.To reduce the influence of actuator faults,an improved artificial potential function is constructed by introducing the lower bound of actuator efficiency factors.The nonlinear state observer,which only depends on measurable position information of the autonomous surface vehicle,is used to address uncertainties and external disturbances.By using a backstepping technique and adaptive mechanism,a path-following control strategy with obstacle avoidance and fault tolerance is designed which can ensure that the tracking errors converge to a small neighborhood of zero.Compared with existing results,the proposed control strategy has the capability of obstacle avoidance and fault tolerance simultaneously.Finally,the comparison results through simulations are given to verify the effectiveness of the proposed method.

XPS Investigation on Surface and Interface Electronic States of Alq_3/ITO

The surface and interface electronic states of tris (8 hydroxyquinoline) aluminum (Alq 3)/indium tin oxide (ITO) were measured and analyzed by X ray photoelectron spectroscopy (XPS). The results indicated that, in Alq 3 molecule, the binding energy ( E b) of Al atoms is 70.7 eV and 75.1 eV, corresponding to Al(O) and Al(Ⅲ), respectively; The binding energy of C is 285.8 eV, 286.3 eV, and 286.8 eV, corresponding to C of C-C group, C-O, and C-N bond, respectively. N is the main peak locating at 401.0 eV, corresponding to N atom of C-N=C. O atoms mainly bond to H atom, with the binding energy of 533.2 eV. As the sputtering time of Ar + ion beam increases, Al 2p , C 1s , N 1s , O 1s , In 3d 5/2 and Sn 3d 5/2 peaks slightly shift towards lower binding energy, and Al 2p , C 1s and N 1s peaks get weaker, which contributes to diffusing the oxygen, indium and tin in ITO into Alq 3 layer.

Phase Diagram and Edge States of Surface States of Topological Superconductors

Majorana fermions in two-dimensional systems satisfy non-Abelian statistics. They are possible to exist in topological superconductors as quasi particles, which is of great significance for topological quantum computing. In this paper, we study a new promising system of superconducting topological surface state topological insulator thin films. We also study the phase diagrams of the model by plotting the Majorana edge states and the density of states in different regions of the phase diagram. Due to the mirror symmetry of the topological surface states, the Hamiltonian can be block diagonalized into two spin-triplet p-wave superconductors, which are also confirmed by the phase diagrams. The chiral Majorana edge modes may provide a new route for realizing topological quantum computation.

Tailoring topological corner states in photonic crystals by near-and far-field coupling effects

We explore the behaviors of optically coupled topological corner states in supercell arrays composed of photonic crystal rods,where each supercell is a second-order topological insulator.Our findings indicate that the coupled corner states possess nondegenerate eigenfrequencies at theΓpoint,with coupled dipole corner states excited resonantly by incident plane waves and displaying a polarization-independent characteristic.The resonance properties of coupled dipole corner states can be effectively modulated via evanescently near-field coupling,while multipole decomposition shows that they are primarily dominated by electric quadrupole moment and magnetic dipole moment.Furthermore,we demonstrate that these coupled corner states can form surface lattice resonances driven by diffractively far-field coupling,leading to a dramatic increase in the quality factor.This work introduces more optical approaches to tailoring photonic topological states,and holds potential applications in mid-infrared topological micro-nano devices.

Engineering d-band states of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material for photocatalytic syngas production

The d-band states of catalytic materials participate in adsorbing reactive intermediate species and determine the catalytic behaviors in CO_(2)reduction reactions.However,surface d-band states relating to the photocatalytic CO_(2)reduction reactions behaviors are rarely concerned.Herein,a slightly amount of Cd^(2+)is decorated on the surface of(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material(Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4))to tune the surface d-band states for improved CO_(2)+2reduction reactions.The Cd/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)is fabricated via the facile ions-exchange method to make that slightly Zn2+is substituted by Cd^(2+).The Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)exhibits much enhanced photocatalytic activity in CO_(2)reduction reactions to produce CO and water splitting to produce H_(2).Physical characterizations show that the energy band structure is not changed obviously.Density functional theory reveals that Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)possesses a closer shift of d-band center to Fermi level than(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4),suggesting easier adsorption of CO_(2)reduction reactive intermediates after Cd^(2+)decoration.Further calculations confirm that a relatively reduced adsorption Gibbs energy of reactive intermediates in CO_(2)reduction reaction is required on Zn atoms in Cd^(2+)/(CuGa)_(x)Zn_(1-2x)Ga_(2)S_(4)material,benefiting the photocatalytic CO_(2)reduction reactions.This work engineers surface d-band states by surface Cd^(2+)decoration,which gives an effective strategy to design highly efficient photocatalysts for syngas production.

Event-triggered model-free adaptive control for a class of surface vessels with time-delay and external disturbance via state observer

This paper provides an improved model-free adaptive control(IMFAC)strategy for solving the surface vessel trajectory tracking issue with time delay and restricted disturbance.Firstly,the original nonlinear time-delay system is transformed into a structure consisting of an unknown residual term and a parameter term with control inputs using a local compact form dynamic linearization(local-CFDL).To take advantage of the resulting structure,use a discrete-time extended state observer(DESO)to estimate the unknown residual factor.Then,according to the study,the inclusion of a time delay has no effect on the linearization structure,and an improved control approach is provided,in which DESO is used to adjust for uncertainties.Furthermore,a DESO-based event-triggered model-free adaptive control(ET-DESO-MFAC)is established by designing event-triggered conditions to assure Lyapunov stability.Only when the system’s indicator fulfills the provided event-triggered condition will the control input signal be updated;otherwise,the control input will stay the same as it is at the last trigger moment.A coordinate compensation approach is developed to reduce the steady-state inaccuracy of trajectory tracking.Finally,simulation experiments are used to assess the effectiveness of the proposed technique for trajectory tracking.

Sub-nano Layers of Li, Be, and Al on the Si(100) Surface: Electronic Structure and Silicide Formation

Within the framework of the density functional theory and the pseudopotential method,the electronic structure calculations of the“metal-Si(100)”systems with Li,Be and Al as metal coverings of one to four monolayers(ML)thickness,were carried out.Calculations showed that band gaps of 1.02 eV,0.98 eV and 0.5 eV,respectively,appear in the densities of electronic states when the thickness of Li,Be and Al coverings is one ML.These gaps disappear with increasing thickness of the metal layers:first in the Li-Si system(for two ML),then in the Al-Si system(for three ML)and then in the Be-Si system(for four ML).This behavior of the band gap can be explained by the passivation of the substrate surface states and the peculiarities of the electronic structure of the adsorbed metals.In common the results can be interpreted as describing the possibility of the formation of a two-dimensional silicide with semiconducting properties in Li-Si(100),Be-Si(100)and Al-Si(100)systems.

Effects of surface states over core-shell Ni@SiO_2 catalysts on catalytic partial oxidation of methane to synthesis gas

In the present work, core-shell Ni@SiO2 catalysts were investigated in order to evaluate the relevance of catalytic activity and surface states of Ni core as well as Ni nanoparticles size to catalytic partial oxidation of methane （POM）. The catalysts were characterized by N2 adsorption, H2-TPR, XRD, TEM and XPS techniques. The catalytic performance of the core-shell catalysts was found to be dependent on the surface states of catalyst, which influenced the formation of products. It was considered that carbon dioxide formed on the oxidized nickel sites （NiO） and carbon monoxide produced on the reduced sites （Ni）. The surface states of active metal in the dynamic were influenced both by the size of Ni core and the porosity of silica shell. However, the catalytic activity would be debased when the size of Ni core was under a certain extent, which can be ascribed to the fact the carbon deposition increased with the increasing content of NiO. The effects of surface states of Ni@SiO2 catalyst on the catalytic performance were discussed and the reaction pathway over Ni core encapsulated inside silica shell was proposed.

Influence of surface states on deep level transient spectroscopy in AlGaN/GaN heterostructure

Deep level transient spectroscopy（DLTS） as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors（HEMTs） has been widely utilized.The DLTS measurements under different bias conditions are carried out in this paper.Two hole-like traps with active energies of E_v ＋ 0.47 eV,and E_v ＋ 0.10 eV are observed,which are related to surface states.The electron traps with active energies of E_c-0.56 eV are located in the channel,those with E_c-0.33 eV and E_c-0.88 eV are located in the AlGaN layer.The presence of surface states has a strong influence on the detection of electron traps,especially when the electron traps are low in density.The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.