Tuning the Electronic Structure of Sr2IrO4 Thin Films by Bulk Electronic Doping Using Molecular Beam Epitaxy

By means of oxide molecular beam epitaxy with shutter-growth mode, we fabricate a series of electron-doped （Sr1-xLax）2IrO4 （001） （x=0, 0.05, 0.1 and 0.15） single crystalline thin films and then investigate the doping dependence of the electronic structure utilizing in-situ angle-resolved photoemission spectroscopy. It is found that with the increasing doping content, the Fermi levels of samples progressively shift upward. Prominently, an extra electron pocket crossing the Fermi level around the M point is evidently observed in the 15% nominal doping sample. Moreover, bulk-sensitive transport measurements confirm that the doping effectively suppresses the insulating state with respect to the as-grown Sr2IrO4, though the doped samples still remain insulating at low temperatures due to the localization effect possibly stemming from disorders including oxygen deficiencies. Our work provides another feasible doping method to tune electronic structure of Sr2 IrO4.

The Principle of Introducing Halogen Ions Into β-FeOOH: Controlling Electronic Structure and Electrochemical Performance

Coordination tuning electronic structure of host materials is a quite effective strategy for activating and improving the intrinsic properties.Herein,halogen anion(X-)-incorporated β-FeOOH(β-FeOOH(X),X=F-,Cl-,and Br-) was investigated with a spontaneous adsorption process,which realized a great improvement of supercapacitor performances by adjusting the coordination geometry.Experiments coupled with theoretical calculations demonstrated that the change of Fe-O bond length and structural distortion of β-FeOOH,which is rooted in halogen ions embedment,led to the relatively narrow band gap.Because of the strong electronegativity of X-,the Fe element in β-FeOOH(X)s presented the unexpected high valence state(3+δ),which is facilitating to adsorb S032-species.Consequently,the designed β-FeOOH(X)s exhibited the good electric conductivity and enhanced the contact between electrode and electrolyte.When used as a negative electrode,the β-FeOOH(F) showed the excellent specific capacity of 391.9 F g-1 at 1 A g-1 current density,almost tenfold improvement compared with initial β-FeOOH,with the superior rate capacity and cyclic stability.This combinational design principle of electronic structure and electrochemical performances provides a promising way to develop advanced electrode materials for supercapacitor.

Review on modification routes for SnO_(x)-based anodes for Li storage:morphological structure tuning and phase structure design

Fascinating with high specific capacity and moderate lithiation potential,SnO_(x)-based materials have been intensively investigated as one of the most promising anodes for lithium-ion batteries.However,due to poor cycling stability,sluggish reaction kinetics,and limited electrochemical reaction reversibility,the development of SnO_(x)-based anodes has been hindered.And the current preparation and modification routes for SnO_(x)-based anodes lack direct and specific illustration.Herein,modification routes for SnO_(x)-based anodes have been emphasized.Firstly,to provide more direct instructions,the tuning routes of morphological structure for SnO_(x)-based electrodes(including slurry-based and self-supported)have been thoroughly discussed from the preparation perspective.Secondly,according to the properties of SnO_(x)-based anodes,the phase structure design ideas have also been properly classified and organized for addressing chemical reaction kinetics or thermodynamic issues.Finally,for future-oriented studies,new insights into the development and commercialization prospects of SnO_(x)-based anodes are also provided.This review,with comprehensive information on SnO_(x)-based anodes,aims to bring more specific guidance and valuable inspiration for peer researchers who are promoting the application of SnO_(x)-based materials for energy conversion and storage devices.

Hexagonal boron nitride adsorbent: Synthesis, performance tailoring and applications

Hexagonal boron nitride(h-BN),with unique structural and properties,has shown enormous potentitoward variety of possible applications.By virtue of partially-ionic character of BN chemical bonds anusually large specific surface area,h-BN-related nanostructures exhibit appealing adsorption propertiewhich can be widely applied for separation and purification towards energy and environment treatmenIn this review,recent progress in designing h-BN micro,nano-structure,controlled synthesis,performancoptimizing as well as energy and environment-related adsorption applications are summarized.Strategieto tailor the h-BN can be classified as morphology control,element doping,defect control and surfacmodification,focusing on how to optimize the adsorption performance.In order to insight the intrinsimechanism of tuning strategies for property optimization,the significant adsorption applications of h-Btowards hydrogen storage,CO2 capture,pollutants removal from water and adsorption desulfurization arpresented.

Bragg Grating Tuning Package Based on a Clamped Beam Structure

It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and theoretically demonstrate that new method can tune the Bragg wavelength without chirp. Further integration of this package can be used for FBG athermal/MEMS packaging.

Lorentz detuning and tuning system study of 3+1/2cell DC-SC photo-injector for PKU-FEL

A 3＋1/2cell DC-SC photo-injector for PKU-FEL facility is under development, which is an upgrade design of the successful 1-4-1/2cell DC-SC photo-injector. The Lorentz detuning and tuning structure for the 3＋1/2cell superconducting cavity is presented in this paper. The Lorentz force detuning coefficient is 1.2 Hz/（MV/m）^2 with double stiffening rings for the half cell and single stiffening rings between the adjacent TESLA cells. With the special stiffening structure, the 3＋1/2cell whole cavity needs only one tuner. The influences of the tuning on frequency shift, field flatness and average gradient are discussed in this paper. The simulation results show that the stiffening rings＇ design is successful.

Trivalent Yb/Ho/Ce tri-doped core/shell NaYF4 nanoparticles for tunable upconversion luminescence from green to red

Three types of β-NaYF_4nanoparticles, uncoated core（NaYF_4：Yb/Ho/Ce）, single-layer coated core@shell（NaYF_4：Yb/Ho/Ce@NaYF_4：Yb） and double-layer coated core@shell@shell（NaYF_4：Yb/Ho@NaYF_4：Yb@NaYF_4：Yb） with Ce^（3＋） doped in core, first and second shell, respectively, were synthesized through solvothermal method to investigate the cross-relaxation between Ho^（3＋） and Ce^（3＋） for the tunable upconversion luminescence. By doping Ce^（3＋） into different layers with different doping concentrations, a systematical investigation on the tunable upconversion luminescence from green to red was conducted. The results showed that a remarkable color tuning could be achieved from green to red when increasing the doping concentration of Ce^（3＋） in the same layer of Ho^（3＋）. And if Ce^（3＋） and Ho^（3＋） were separated in different layers, the color tuning would be depressed significantly due to the reduced cross-relaxation between Ho^（3＋） and Ce^（3＋）. Moreover, the UC emission intensity of core@shell and core@shell@shell was enhanced significantly compared with that of unmodified core nanoparticles.