Mg doping reduced full width at half maximum of the near-band-edge emission in Mg doped ZnO films

Sol--gol method was employed to synthesize Mg doped ZnO films on Si substrates. The annealing temperature-dependent structure and optical property of the produced samples were studied. An interesting result observed is that increasing Mg concentration in the studied samples induces the full width at half maximum （FWHM） of their near-band-edge （NBE） emission decrease and the defect related emission of the corresponding sample suppresses drastically. The possible mechanism of the observed result is discussed.

Synthesis of nitrogen-doped single-walled carbon nanotubes and monitoring of doping by Raman spectroscopy

Nitrogen-doped single-walled carbon nanotubes （CNx-SWNTs） with tunable dopant concentrations were synthesized by chemical vapor deposition （CVD）, and their structure and elemental composition were characterized by using transmission electron microscopy （TEM） in combination with electron energy loss spectroscopy （EELS）. By comparing the Raman spectra of pristine and doped nanotubes, we observed the doping-induced Raman G band phonon stiffening and 2D band phonon softening, both of which reflect doping-induced renormalization of the electron and phonon energies in the nan- otubes and behave as expected in accord with the n-type doping effect. On the basis of first principles calculations of the distribution of delocalized carrier density in both the pristine and doped nanotubes, we show how the n-type doping occurs when nitrogen heteroatoms are substitutionally incorporated into the honeycomb tube-shell carbon lattice.

Effects of Heat-treatment Temperature on Eu^(3+) and Li^+ Co-doped ZnO Photoluminescence by Sol-gel Process

The photoluminescence （PL） characteristics of Eu^3＋ and Li^＋ co-doped ZnO PL materials against heat-treatment temperature were discussed. The PL xerogel and powder samples were prepared by solgel process. The emission spectra of all samples showed two broad bands peaking at 590 nm and 620 nm under UV-Vis excitation. But the relative intensity of red PL （620 nm） was much greater than that of green PL （590 nm） of the same sample, that s to say, the red color was the main luminescence. With heat-treatment temperature increase, the two kinds of colors PL intensity decreased, and both the red and green PL intensity of the xerogel samples was much greater than those of powder samples respectively. The XRD patterns revealed that Eu^3＋ ions were successfully incorporated in ZnO crystals in xerogel samples. When heat-treatment temperature reached 350 ℃, the Eu^3＋ began to separate out of the ZnO crystals and Eu2O3 crystals came into being. When the powder sample was subjected to UV-Vis excitation, the energy transfered from the host ZnO emission to Eu^3＋ became weaker than the xerogel sample.

Fabrication of Pd-Nb bimetallic doped organosilica membranes by different metal doping routes for H_(2)/CO_(2) separation

Monometallic doping has proved its superiority in improving either permselectivity or H_(2) permeability of organosilica membranes for H_(2)/CO_(2) separation,but it is still challenging to break the trade-off effect.Herein,we report a series of Pd-Nb bimetallic doped 1,2-bis(triethoxysilyl)ethane(Pd-Nb-BTESE,PNB)membranes with different metal doping routes for simultaneously improving H_(2) permeance and H_(2)/CO_(2) permselectivity by the synergetic effects of Pd and Nb.The doped Pd can exist in the BTESE network as nanoparticles while the doped Nb is incorporated into BTESE network forming Nb-O-Si covalent bonds.The metal doping routes significantly influence the microstructure of PNB networks and gas separation performance of the PNB membranes.We found that the PNB membrane with Pd doping priority(PNB-Pd)exhibited the highest surface area and pore volume,comparing with Nb doping priority(PNB-Nb)or Pd-Nb simultaneous doping(PNB-PdNb).The PNB-Pd membrane could not only exhibit an excellent H_(2) permeance of~10^(−6) mol·m^(−2)·s^(−1)·Pa^(−1) but also a high H_(2)/CO_(2) permselectivity of 17.2.Our findings may provide novel insights into preparation of bimetallic doped organosilica membranes with excellent H_(2)/CO_(2) separation performance.

Confinement of sulfur-doped NiO nanoparticles into N-doped carbon nanotube/nanofiber-coupled hierarchical branched superstructures:Electronic modulation by anion doping boosts oxygen evolution electrocatalysis

The search for non-precious and efficient electrocatalysts towards the oxygen evolution reaction(OER)is of vital importance for the future advancement of multifarious renewable energy conversion/storage technologies.Electronic modulation via heteroatom doping is recognized as one of the most forceful leverages to enhance the electrocatalytic activity.Herein,we demonstrate a delicate strategy for the in-situ confinement of S-doped Ni O nanoparticles into N-doped carbon nanotube/nanofiber-coupled hierarchical branched superstructures(labeled as S-Ni O@N-C NT/NFs).The developed strategy simultaneously combines enhanced thermodynamics via electronic regulation with accelerated kinetics via nanoarchitectonics.The S-doping into Ni O lattice and the 1 D/1 D-integrated hierarchical branched carbon substrate confer the resultant S-Ni O@N-C NT/NFs with regulated electronic configuration,enriched oxygen vacancies,convenient mass diffusion pathways and superior architectural robustness.Thereby,the SNi O@N-C NT/NFs display outstanding OER properties with an overpotential of 277 m V at 10 m A cm^(-2)and impressive long-term durability in KOH medium.Density functional theory(DFT)calculations further corroborate that introducing S-dopant significantly enhances the interaction with key oxygenate intermediates and narrow the band gap.More encouragingly,a rechargeable Zn-air battery using an air-cathode of Pt/C+S-Ni O@N-C NT/NFs exhibits a lower charge voltage and preferable cycling stability in comparison with the commercial Pt/C+Ru O_(2)counterpart.This study highlighting the concurrent consideration of electronic regulation,architectural design and nanocarbon hybridization may shed light on the future exploration of economical and efficient electrocatalysts.

Preparation of Ta-Doped TiO2 Using Ta2O5 as the Doping Source

A novel method for preparing Ta-doped Ti02 via using Ta2 05 as the doping source is proposed. The preparation process combines the hydrothernlal fluorination of Ta2O5 and the subsequent formation of Ta-doped TiO2 sol. The results show that the doped sample annealed at 393 K generates an unstable intermediate NH4 TiOF3, which converts into anatase TiO2 with the increase of temperature. After annealing at ≥673K, the Ta-doped TiO2 nanocrystals with the grain size 〈20nm are obtained. Both the XRD and TG-DSC results confirm that Ta doping prevents the anatase-rutile crystal transition of TiO2. The band gap values of the doped samples, as obtained by UV-vis diffuse reflectance spectra, are smaller than that of pure anatase TiO2. The first-principle pseudopotential method calculations indicate that Ta5＋ lies in the TiO2 lattice at the interstitial position.

Influence of different Fe doping strategies on modulating active sites and oxygen reduction reaction performance of Fe, N-doped carbonaceous catalysts

Fe/N/C catalysts,synthesized through the pyrolysis of Fe-doped metal–organic framework (MOF) precursors,have attracted extensive attention owing to their promising oxygen reduction reaction (ORR) catalytic activity in fuel cells and/or metal-air batteries.However,post-treatments (acid washing,second pyrolysis,and so on) are unavoidable to improve ORR catalytic activity and stability.The method for introducing Fe^(3+) sources (anhydrous Fe Cl_(3)) into the MOF structure,in particular,is a critical step that can avoid time-consuming post-treatments and result in more exposed Fe-N_(x) active sites.Herein,three different Fe doping strategies were systematically investigated to explore their influence on the types of active sites formed and ORR performance.Fe-NC(Zn^(2+)),synthesized by one-step pyrolysis of Fe doped ZIF-8 (Zn^(2+)) precursor which was obtained by adding the anhydrous Fe Cl_(3)source into the Zn(NO_(3))_(2)·6H_(2)O/methanol solution before mixing,possessed the highest Fe-N_(x)active sites due to the high-efficiency substitution of Zn^(2+)ions with Fe^(3+) ions during ZIF-8 growth,the strong interaction between Fe^(3+) ions and N atoms of 2-Methylimidazole (2-MIm),and ZIF-8’s micropore confinement effect.As a result,Fe-NC(Zn^(2+)) presented high ORR activity in the entire p H range (p H=1,7,and 13).At p H=13,Fe-NC(Zn^(2+)) exhibited a half-wave potential (E1/2) of 0.95 V (vs.reversible hydrogen electrode),which was 70 m V higher than that of commercial Pt/C.More importantly,Fe-NC(Zn^(2+)) showed superior ORR stability in neutral media without performance loss after 5,000 cycles.A record-high open-circuit voltage(1.9 V) was obtained when Fe-NC(Zn^(2+)) was used as a cathodic catalyst in assembled Mg-air batteries in neutral media.The assembled liquid and all-solid Mg-air batteries with high performance indicated that Fe-NC(Zn^(2+)) has enormous potential for use in flexible and wearable Mg-air batteries.

Li^(+)增强NaGd(WO_(4))_(2)∶Yb^(3+)/Er^(3+)荧光粉的上转换发光和温度传感性能

采用水热法制备了NaGd(WO_(4))_(2)∶0.05Yb^(3+)/0.005Er^(3+)/xLi^(+)(x=0,0.01,0.02,0.03,0.05)荧光粉。通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和光致发光(PL)谱等手段分析了样品的晶体结构、形貌和上转换发光性能。结果表明,Li的掺杂并未改变NaGd(WO_(4))_(2)∶Yb^(3+)/Er^(3+)荧光粉的四方相晶体结构,但在波长980nm激光二极管(LD)激发下,样品的上转换发光强度发生明显改变。随着x的增加,Er^(3+)的绿光和红光发光强度均呈现先升高后降低的趋势,当x=0.03时,发光强度达到最大值。上转换发光强度与泵浦功率的依赖关系表明,绿光和红光发射都属于双光子吸收过程。此外,采用基于Er^(3+)热耦合能级的荧光强度比(FIR)测温技术,研究了+NaGd(WO_(4))_(2)∶0.05Yb^(3+)/0.005Er^(3+)/0.03Li^(+)荧光粉在298~573K温度范围内的温度传感性能。该结果表明NaGd(WO_(4))_(2)∶0.05Yb^(3+)/0.005Er^(3+)/0.03Li^(+)荧光粉相对灵敏度(SR)在298K时达到最大值0.0119K^(-1),表明其在光学温度传感领域具有潜在的应用价值。

Li^(+)浓度对化学增强锂铝硅玻璃性能的影响

采用一步法化学增强工艺,研究了熔盐中Li^(+)的富集对不同厚度锂铝硅玻璃表面压应力、应力层深度、弯曲强度、硬度等性能的影响,选择Na_(3)PO_(4)作为熔盐除杂剂并对净化效果进行了评定。研究表明:熔盐中Li^(+)浓度增加至4800×10^(-6),3 mm化学增强锂铝硅玻璃的表面压应力、弯曲强度、硬度下降16.8%、16.8%、10.6%;8 mm化学增强锂铝硅玻璃的表面压应力、弯曲强度、硬度下降17.6%、14.7%、9.8%。熔盐中Li^(+)浓度的变化未对化学增强锂铝硅玻璃应力层深度产生明显影响。Na_(3)PO_(4)具有较好的除杂效果,化学增强锂铝硅玻璃的表面压应力、弯曲强度、硬度得到了明显的恢复,为保证化学增强锂铝硅玻璃在可见光波段具有较高的透光率,除杂剂Na_(3)PO_(4)的掺量不宜超过1%(质量分数)。

Effects of Host Doping on Spectral and Long-Lasting Properties of Sm^(3+)-Doped Y_2O_2S

Gd- or Lu-doped long afterglow red phosphor Y2O2S：Sm^3＋ was synthesized using the high temperature flux fusion method. The obtained phosphors were analyzed using X-ray diffraction to determine the crystal structure, and the phase analyses show that the product is in single phase. The luminescence spectra and decay curve were measured on a Hitachi F-4500 fluorescence spectrophotometer. The decay time was determined on an ST-900PM weak light photometer. The analyses show that host doping of Lu improves both luminescence and decay time of the materials. The concentration of doped Lu and Sm was varied in order to determine the optimal condition and to synthesize the product with the best properties. The mechanism of the long afterglow was also briefly discussed.

Enhancing multifunctional photocatalysis with acetate-assisted cesium doping and unlocking the potential of Z-scheme solar water splitting

Graphitic carbon nitride(g-C_(3)N_(4))has been extensively doped with alkali metals to enlarge photocatalytic output,in which cesium(Cs)doping is predicted to be the most efficient.Nevertheless,the sluggish diffusion and doping kinetics of precursors with high melting points,along with imprecise regulation,have raised the debate on whether Cs doping could make sense.For this matter,we attempt to confirm the positive effects of Cs doping on multifunctional photocatalysis by first using cesium acetate with the character of easy manipulation.The optimized Csdoped g-C_(3)N_(4)(CCN)shows a 41.6-fold increase in visible-light-driven hydrogen evolution reaction(HER)compared to pure g-C_(3)N_(4) and impressive degradation capability,especially with 77%refractory tetracycline and almost 100%rhodamine B degradedwithin an hour.The penetration ofCs+is demonstrated to be a mode of interlayer doping,and Cs–N bonds(especially with sp^(2) pyridine N in C═N–C),along with robust chemical interaction and electron exchange,are fabricated.This atomic configuration triggers the broadened spectral response,the improved charge migration,and the activated photocatalytic capacity.Furthermore,we evaluate the CCN/cadmium sulfide hybrid as a Z-scheme configuration,promoting the visible HER yield to 9.02 mmol g^(−1) h^(−1),which is the highest ever reported among all CCN systems.This work adds to the rapidly expanding field of manipulation strategies and supports further development of mediating served for photocatalysis.

Effect of the Doping Layer Concentration on Optical Absorption in Si δ-Doped GaAs Layer

We study in this paper the intersubband optical absorption of Si doped GaAs layer for different applied electric fields and donors concentration. The electronic structure has been calculated by solving the Schr?dinger and Poisson equations self-consistently. From our results, it is clear that the subband energies and intersubband optical absorption are quite sensitive to the applied electric field. Also our results indicate that the optical absorption depends not only on the electric field but also on the donor’s concentration. The results of this work should provide useful guidance for the design of optically pumped quantum well lasers and quantum well infrared photo detectors (QWIPs).

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.

Enhancing the stability of Ni Fe-layered double hydroxide nanosheet array for alkaline seawater oxidation by Ce doping

Electrocatalytic hydrogen production from seawater holds enormous promise for clean energy generation.Nevertheless,the direct electrolysis of seawater encounters significant challenges due to poor anodic stability caused by detrimental chlorine chemistry.Herein,we present our recent discovery that the incorporation of Ce into Ni Fe layered double hydroxide nanosheet array on Ni foam(Ce-Ni Fe LDH/NF)emerges as a robust electrocatalyst for seawater oxidation.During the seawater oxidation process,CeO_(2)is generated,effectively repelling Cl^(-)and inhibiting the formation of Cl O-,resulting in a notable enhancement in the oxidation activity and stability of alkaline seawater.The prepared Ce-Ni Fe LDH/NF requires only overpotential of 390 m V to achieve the current density of 1 A cm^(-2),while maintaining long-term stability for 500 h,outperforming the performance of Ni Fe LDH/NF(430 m V,150 h)by a significant margin.This study highlights the effectiveness of a Ce-doping strategy in augmenting the activity and stability of materials based on Ni Fe LDH in seawater electrolysis for oxygen evolution.

Co-doped BaFe_(2)As_(2) Josephson junction fabricated with a focused helium ion beam

Josephson junction plays a key role not only in studying the basic physics of unconventional iron-based superconductors but also in realizing practical application of thin-film based devices,therefore the preparation of high-quality iron pnictide Josephson junctions is of great importance.In this work,we have successfully fabricated Josephson junctions from Co-doped BaFe_(2)As_(2)thin films using a direct junction fabrication technique which utilizes high energy focused helium ion beam(FHIB).The electrical transport properties were investigated for junctions fabricated with various He^(+)irradiation doses.The junctions show sharp superconducting transition around 24 K with a narrow transition width of 2.5 K,and a dose correlated foot-structure resistance which corresponds to the effective tuning of junction properties by He^(+)irradiation.Significant J_c suppression by more than two orders of magnitude can be achieved by increasing the He^(+)irradiation dose,which is advantageous for the realization of low noise ion pnictide thin film devices.Clear Shapiro steps are observed under 10 GHz microwave irradiation.The above results demonstrate the successful fabrication of high quality and controllable Co-doped BaFe_(2)As_(2)Josephson junction with high reproducibility using the FHIB technique,laying the foundation for future investigating the mechanism of iron-based superconductors,and also the further implementation in various superconducting electronic devices.

The effects of Zn vacancies on ferromagnetism in Cu-doped ZnO films controlled by oxygen pressure and Li doping

Zn0.99Cu0.01O films were studied experimentally and theoretically. The films were prepared by pulsed-laser deposition on Pt（111）/Ti/SiO2/Si substrates under various oxygen pressures to investigate the growth-dependence of the ferromagnetic properties. The structural, magnetic, and optical properties were studied, and it was found that all the samples possess a typical wurtzite structure, and that the films exhibit room-temperature ferromagnetism. The sample deposited at 600 ℃ and an oxygen pressure of 10 Pa showed a large saturation magnetization of 0.83 μB/Cu. The enhanced ferromagnetism in the （Cu, Li）-codoped ZnO is attributable to the existence of Zn vacancies （Vzn）, as shown by first-principles calcu- lations. The photoluminescence analysis demonstrated the existence of Vzn in both Zn0.99Cu0.01 O and （Cu, Li）-codoped ZnO thin films, and this plays an important role in the increase of ferromagnetism, according to the results of first-principles calculations.

掺杂Li^(+)的NaGdF_(4)∶Yb^(3+)/Eu^(3+)上转换发光增强及防伪应用

稀土发光材料由于其良好的上转换发光性能已经逐渐成为荧光防伪领域的研究热点。首先采用水热法合成了一系列不同Li^(+)掺杂浓度的NaGdF_(4)∶Yb^(3+)/Eu^(3+)晶体,利用X射线衍射(XRD)、扫描电子显微镜(SEM)、上转换发射光谱测试等表征方法,对样品的形貌、尺寸和上转换发光性能进行了分析,并选择发光强度和效果最好的晶体应用于防伪识别。实验结果表明,NaGdF_(4)∶Yb^(3+)/Eu^(3+)/Li^(+)的XRD衍射图谱与标准六方相NaGdF4的衍射峰一致,衍射峰尖锐且没有杂峰,证明合成了高纯度高结晶度的NaGdF4∶Yb^(3+)/Eu^(3+)/Li^(+)晶体。晶体的SEM图可以看出生成的样品为纯六方相,分布均匀,无团聚现象。共掺Yb^(3+)/Eu^(3+)/Li^(+)对晶体的结构、形貌、尺寸几乎没有影响。从上转换发射光谱可以看出,15 mol%Li^(+)掺杂的NaGdF4∶Yb^(3+)/Eu^(3+)晶体绿色发光强度是未掺杂Li^(+)的样品的6倍。考察了980 nm激光器的功率变化对未掺杂Li^(+)以及掺杂15 mol%Li^(+)样品的上转换发光性能的影响,发现随着激发功率从0.8 W增加到2.2 W的过程中,上转换发光强度逐渐增强。拟合后得到样品上转换过程中的所需光子数n值接近于2,为双光子发光过程。对NaGdF4∶Yb/Eu/Li进行了荧光寿命测试,5D_(1)能级的荧光寿命是未掺杂的1.4倍。最后,将形貌均匀、发光强度强的NaGdF_(4)∶0.2Yb/0.02Eu/0.15Li制成防伪油墨,通过丝网印刷技术在纸张、玻璃、塑料等材料上印刷荧光防伪图案。在980 nm激光的泵浦下,防伪图案发出明亮的绿光。在自然环境下,纸张上的防伪图案有很好的隐蔽性。图案中的“safe”字样长度为5.5 mm,字母间距为0.5 mm,在980 nm激光的泵浦下,仍然可以分辨清楚。将印制有防伪图案的塑料暴露在室外自然环境下一个月,图案没有明显改变。表明NaGdF_(4)∶0.2Yb/0.02Eu/0.15Li制成的防伪图案分辨率高,易于识别,受环境影响小,在防伪识别方面具有良好的应用前景。

Mitigating kinetic hindrance of single-crystal Ni-rich cathodes through morphology modulation,nickel reduction,and lithium vacancy generation achieved by terbium doping

Single crystallization has proven to be effective in enhancing the capacity and stability of Ni-rich LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(SNCM)cathode materials,particularly at high cut-off voltages.Nevertheless,the synthesis of high-quality single-crystal particles remains challenging because of severe particle agglomeration and irregular morphologies.Moreover,the limited kinetics of solid-phase Li^(+)diffusion pose a significant concern because of the extended diffusion path in large single-crystal particles.To address these challenges,we developed a Tb-doped single-crystal LiNi_(0.83)Co_(0.11)Mn_(0.06)O_(2)(SNCM-Tb)cathode material using a straightforward mixed molten salt sintering process.The Tb-doped Ni-rich single crystals presented a quasi-spherical morphology,which is markedly different from those reported in previous studies.Tb^(4+)oping significantly enhanced the dynamic transport of Li^(+)ions in the layered oxide phase by reducing the Ni valence state and creating Li vacancies.A SNCM-Tb material with 1 at%Tb doping shows a Li^(+)diffusion coefficient up to more than 9 times higher than pristine SNCM in the non-diluted state.In situ X-ray diffraction analysis demonstrated a significantly facilitated H1-H2-H3 phase transition in the SNCM-Tb materials,thereby enhancing their rate capacity and structural stability.SNCM-Tb exhibited a reversible capacity of 186.9 mA h g^(-1)at 5 C,retaining 94.6%capacity after 100 cycles at 0.5 C under a 4,5 V cut-off.Our study elucidates the Tb^(4+)doping mechanisms and proposes a scalable method for enhancing the performance of single-crystal Ni-rich NCM materials.

Effects of N-doping concentration on the electronic structure and optical properties of N-doped β-Ga_2O_3

The electronic structures and the optical properties of N-doped β-Ga2O3 with different N-doping concentrations are studied using the first-principles method.We find that the N substituting O（1） atom is the most stable structure for the smallest formation energy.After N-doping,the charge density distribution significantly changes,and the acceptor impurity level is introduced above the valence band and intersects with the Fermi level.The impurity absorption edges appear to shift toward longer wavelengths with an increase in N-doping concentration.The complex refractive index shows metallic characteristics in the N-doped β-Ga2O3.

Effects of doping concentration on properties of Mn-doped ZnO thin films

This paper reports that the radio frequency magnetron sputtering is used to fabricate ZnO and Mn-doped ZnO thin films on glass substrates at 500 ℃. The Mn-doped ZnO thin films present wurtzite structure of ZnO and have a smoother surface, better conductivity but no ferromagnetism. The x-ray photoelectron spectroscopy results show that the binding energy of Mn2p3/2 increases with increasing Mn content slightly, and the state of Mn in the Mn-doped ZnO thin films is divalent. The chemisorbed oxygen in the Mn-doped ZnO thin films increases with increasing Mn doping concentration. The photoluminescence spectra of ZnO and Mmdoped ZnO thin films have a similar ultraviolet emission. The yellow green emissions of 4 wt.% and 10 wt.% Mn-doped thin films are quenched, whereas the yellow green emission occurs because of abundant oxygen vacancies in the Mn-doped ZnO thin films after 20 wt.% Mn doping. Compared with pure ZnO thin film, the bandgap of the Mn-doped ZnO thin films increases with increasing Mn content.