Electronic structures and optical properties of Zn-dopedβ-Ga_2O_3 with different doping sites

The electronic structures and optical properties of intrinsic β-Ga2O3 and Zn-dopedβ-Ga2O3 are investigated by first-principles calculations. The analysis about the thermal stability shows that Zn-doped β-Ga2O3 remains stable. The Zn doping does not change the basic electronic structure of β-Ga2O3, but only generates an empty energy level above the maximum of the valence band, which is shallow enough to make the Zn-doped β-Ga2O3 a typical p-type semiconductor. Because of Zn doping, absorption and reflectivity are enhanced in the near infrared region. The higher absorption and reflectivity of ZnGa（2） than those of ZnGa（1） are due to more empty energy states of ZnGa（2） than those of ZnGa（1） near Ef in the near infrared region.

Electrochemical Synthesis of Novel Zn-Doped TiO_2 Nanotube/ZnO Nanoflake Heterostructure with Enhanced DSSC Efficiency

The paper reports the fabrication of Zn-doped TiO_2 nanotubes(Zn-TONT)/ZnO nanoflakes heterostructure for the first time,which shows improved performance as a photoanode in dye-sensitized solar cell(DSSC).The layered structure of this novel nanoporous structure has been analyzed unambiguously by Rutherford backscattering spectroscopy,scanning electron microscopy,and X-ray diffractometer.The cell using the heterostructure as photoanode manifests an enhancement of about an order in the magnitude of the short circuit current and a seven-fold increase in efficiency,over pure TiO_2 photoanodes.Characterizations further reveal that the Zn-TONT is preferentially oriented in [001] direction and there is a Ti metal-depleted interface layer which leads to better band alignment in DSSC.

Structure and properties of Li-rich Zn-doped LiNbO_3 Crystal

The Li-rich Zn-doped LiNbO 3 (LN) crystals were grown by the Czochralski method. The structure of the crystals was measured by ultraviolet-visible absorption spectra. The results indicated that the Li-rich Zn-doped LN crystals had the same characteristics as the pure LN crystal. After Zn 2+ entered into the lattice of Li-rich Zn-doped LN crystal, it replaced Nb Li firstly. When there was no Nb Li , Zn 2+ replaced Li + then. The second harmonic generation (SHG) property of Li-rich Zn-doped LiNbO 3 crystal was measured. The results showed that the SHG conversation efficiency of Li-rich Zn-doped LiNbO 3 crystals was higher than that of Zn-doped LiNbO 3 crystals.

Metal-organic framework-derived, Zn-doped porous carbon polyhedra with enhanced activity as bifunctional catalysts for rechargeable zinc-air batteries

Zinc-air batteries have recently attracted considerable interest owing to the larger storage capacity and lower cost compared to their lithium-ion counterparts. Electrode catalysts for the oxygen reduction reaction （ORR） and oxygen evolution reaction （OER） play a critical role in the operation of rechargeable zinc-air batteries. Herein, we report a simple and scalable strategy to fabricate porous carbon polyhedra using Zn-doped Co-based zeolitic imidazolate frameworks （ZnCo-ZIFs） as precursors. Strikingly, Zn doping leads to smaller Co nanoparticles and higher nitrogen content, which in turn enhances the ORR and OER activities of the obtained porous carbon polyhedra. The synergistic effect of the N-doped carbon and cobalt nanoparticles in the composite, the improved conductivity resulting from the high graphitization of carbon, and the large surface area of the porous polyhedral structure resulted in porous carbon polyhedra with excellent ORR and OER electrocatalytic activity in alkaline media. More importantly, air cathodes based on the optimal porous carbon polyhedra further exhibited superior performance to Pt/C catalysts in primary and rechargeable zinc-air batteries.

Reply to Comments on "Structural,Optical,and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique'' by K.Usharani and A.R.Balu published in Acta Metall.Sin.(Engl.Lett.) 28(1),64–71(2015)

Following are the comments for the queries raised by Prof. Pawel E. Tomaszewski on our published paper entitled ＂Structural, Optical, and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique＂ by K. Usharani and A.R. Balu published in Acta Metall. Sin.

Boosting Zn-ion storage capability of self-standing Zn-doped Co_(3)O_(4)nanowire array as advanced cathodes for high-performance wearable aqueous rechargeable Co//Zn batteries

Neutral aqueous rechargeable Co_(3)O_(4)//Zn batteries with high-output voltage and outstanding cycling stability have yielded new insights into wearable energy-storage devices.To meet the increasing demand for a means of powering wearable and portable devices,the development of a high-performance fiber-shaped Co//Zn battery would be highly desirable.However,the intrinsically poor conductivity of C 03O4 significantly restricts the application of these high-capacity and high-rate aqueous rechargeable battery.Encouragingly,density functional theory(DFT)calculations demonstrate that the substitution of Zn for Co^(3+)leads to an insulatormetal transition in the Zn-doped Co_(3)O_(4)(Zn-Co_(3)O_(4)).In this study,we used metallic Zn-Co_(3)O_(4)nanowire arrays(NWAs)as a novel binder-free cathode to successfully fabricate an all-solid-state fiber-shaped aqueous rechargeable(AFAR)Co//Zn battery.The resulting fiber-shaped Co//Zn battery takes advantage of the enhanced conductivity,increased capacity,and improved rate capability of Zn-Co_(3)O_(4)NWAs to yield a remarkable capacity of 1.25 mAh·cm^(-2)at a current density of 0.5 mA·cm^(-2),extraordinary rate capability(60.8%capacity retention at a high current density of 20 mA·cm^(-2))and an admirable energy density of 772.6 mWh·cm^(-3).Thus,the successful construction of Zn-Co_(3)O_(4)NWAs provides valuable insights into the design of high-capacity and high-rate cathode materials for aqueous rechargeable high-voltage batteries.

Structural and optical properties of Zn-doped β-Ga_2O_3 films

Intrinsic fi-Ga203 and Zn-doped β-Ga203 films were prepared using RF magnetron sputtering. The effects of the Zn doping and thermal annealing on the structural and optical properties are investigated. In compar- ison with the intrinsic β-Ga203 films, the microstructure, optical transmittance, optical absorption, optical energy gap, and photoluminescence ofZn-doped β-Ga203 films change significantly. The post-annealed β-Ga203 films are polycrystalline. After Zn doping, the crystallization deteriorates, the optical band gap shrinks, the transmittance decreases and the UV, blue, and green emission bands are enhanced.

Comments on "Structural,Optical,and Electrical Properties of Zn-Doped CdO Thin Films Fabricated by a Simplified Spray Pyrolysis Technique'' by K.Usharani and A.R.Balu Published in Acta Metall.Sin.(Engl.Lett.) 28(1),64–71(2015)

The commented paper [1] presents the results on structural, optical, and electrical properties of Zn-doped CdO thin films. Unfortunately, there are several mistakes and errors not found by any of referees. It is necessary to show these mistakes or misleading statements to avoid their use in the future papers by authors and other peoples.

Characterization of Zn-doped GaN grown by metal–organic vapor phase epitaxy

The point defects and photoluminescence(PL)spectra of gallium nitride(GaN)epilayers with Mg,Zn,and unintentional doping were investigated in this study.The concentration of point defects(Ga vacancy and its related complexes)in the Zn-doped GaN is consistent with that in the Mg-doped GaN,but lower than that in undoped GaN.It is suggested that Zn(Mg)atoms occupy Ga sites and suppress the formation of Ga vacancies.Comparing the blue luminescence(BL)band intensity of GaN:Zn with that of GaN:Mg,a factor of 10 strong PL intensity demonstrates that a moderate incorporation of Zn to GaN is likely to improve the structural quality of GaN.Detailed studies on 2.93 eV BL band for GaN:Zn reveal that the Zn related BL band behaves as a donor-acceptor pairs character.For the acceptor level,isolated Zn_(Ga)with the activation energy of 0.386 eV above the valence band is obtained from temperature-dependent PL measurements,whereas the deep donor defect responsible for the 2.93 eV band is deduced to be 164 meV below the conduction band.An O_(N)-H complex model is suggested to explain the deep donor origin.

Understanding the promotional effects of trace doped Zn in Co/NC for efficient one-pot catalytic conversion of furfural to 2-methyl-tetrahydrofuran

2-methyl-tetrahydrofuran(2-MTHF)is a promising biofuel or fuel additive with excellent burning property,a versatile new-style solvent in organic synthesis,and an important medical intermediate.In this work,a one-pot selective conversion of furfural(FA)into 2-MTHF was carried out over Zn doped Co/NC catalysts.The Zn-Co/NC-1 catalyst with trace Zn dopant(0.38 wt%)exhibited the best performance(yield of 2-MTHF:93.8%).According to the characterizations,it was found that the Zn not only incorporates into the carbon support but also partially dopes into Co nanoparticles.Subsequently,theoretical calculations demonstrated that the doping of Zn in carbon support can effectively enhance the electron transfer from the support to the metallic Co particle,leading to the electron-rich Co surface.The presence of Zn was found to promote the dissociation of hydrogen and to lower the diffusion barrier of hydrogen atom,in favor of the hydrogenation/hydrodeoxygenation processes.Furthermore,the Zn doped models exhibit much lower barrier in breaking C–OH bond of FOL,resulting in higher activity for hydrodeoxygenation of FOL.These theoretical results are consistent with the in situ FT-IR analysis of adsorption substrates and intermediates over Zn doped catalyst.This work reveals the mechanism of dopant Zn tailoring the electronic structure and catalytic performance of active sites,providing a deep insight into the design of economical and high-performance catalysts for hydrogenation/hydrodeoxygenation of biomass feedstocks.

Photocatalytic synergistic biofilms enhance tetracycline degradation and conversion

Tetracyclines are refractory pollutants that cause persistent harm to the environment and human health.Therefore,it is urgently necessary to develop methods to promote the efficient degradation and conversion of tetracyclines in wastewater.This report proposes a photobiocatalytic synergistic system involving the coupling of GeO_(2)/Zn-doped phosphotungstic acid hydrate/TiO_(2)(GeO_(2)/Zn-HPW/TiO_(2))-loaded photocatalytic optical hollow fibers(POHFs)and an algalebacterial biofilm.The GeO_(2)/Zn-HPW/TiO_(2) photocatalyst exhibits a broad absorption edge extending to 1000 nm,as well as high-efficiency photoelectric conversion and electron transfer,which allow the GeO_(2)/Zn-HPW/TiO_(2)-coated POHFs to provide high light intensity to promote biofilm growth.The resulting high photocatalytic activity rapidly and stably reduces the toxicity and increases the biodegradability of tetracycline-containing wastewater.The biofilm enriched with Salinarimonas,Coelastrella sp.,and Rhizobium,maintains its activity for the rapid photocatalytic degradation and biotransformation of intermediates to generate the O_(2) required for photocatalysis.Overall,the synergistic photocatalytic biofilm system developed herein provides an effective and efficient approach for the rapid degradation and conversion of water containing high concentrations of tetracycline.