Self-assembled S-scheme In_(2.77)S_(4)/K^(+)-doped g-C_(3)N_(4)photocatalyst with selective O_(2)reduction pathway for efficient H_(2)O_(2)production using water and air

The development of an efficient artificial H_(2)O_(2)photosynthesis system is a challenging work using H_(2)O and O_(2)as starting materials.Herein,3D In2.77S_(4)nanoflower precursor was in-situ deposited on K^(+)-doped g-C_(3)N_(4)(KCN)nanosheets using a solvothermal method,then In2.77S_(4)/KCN(IS/KCN)het-erojunction with an intimate interface was obtained after a calcination process.The investigation shows that the photocatalytic H_(2)O_(2)production rate of 50IS/KCN can reach up to 1.36 mmol g^(-1)h^(-1)without any sacrificial reagents under visible light irradiation,which is 9.2 times and 4.1 times higher than that of KCN and In2.77S_(4),respectively.The enhanced activity of the above composite can be mainly attributed to the S-scheme charge transfer route between KCN and In2.77S_(4)according to density functional theory calculations,electron paramagnetic resonance and free radical capture tests,leading to an expanded light response range and rapid charge separation at their interface,as well as preserving the active electrons and holes for H_(2)O_(2)production.Besides,the unique 3D nanostructure and surface hydrophobicity of IS/KCN facilitate the diffusion and transportation of O_(2)around the active centers,the energy barriers of O_(2)protonation and H_(2)O_(2)desorption steps are ef-fectively reduced over the composite.In addition,this system also exhibits excellent light harvesting ability and stability.This work provides a potential strategy to explore a sustainable H_(2)O_(2)photo-synthesis pathway through the design of heterojunctions with intimate interfaces and desired reac-tion thermodynamics and kinetics.

First-Principles Investigation of Charge Transfer Mechanism of B-Doped 3C-SiC Semiconductor Material

This study delves into the charge transfer mechanism of boron (B)-doped 3C-SiC through first-principles investigations. We explore the effects of B doping on the electronic properties of 3C-SiC, focusing on a 12.5% impurity concentration. Our comprehensive analysis encompasses structural properties, electronic band structures, and charge density distributions. The optimized lattice constant and band gap energy of 3C-SiC were found to be 4.373 Å and 1.36 eV respectively, which is in agreement with previous research (Bui, 2012;Muchiri et al., 2018). Our results show that B doping narrows the band gap, enhances electrical conductivity, and influences charge transfer interactions. The charge density analysis reveals substantial interactions between B dopants and surrounding carbon atoms. This work not only enhances our understanding of the material’s electronic properties, but also highlights the importance of charge density analysis for characterizing charge transfer mechanisms and their implications in the 3C-SiC semiconductors.

Tm^(3+)-doped tellurite glass with Yb^(3+) energy sensitized for broadband amplifier at 1400–1700 nm bands

A kind of novel experiment was disclosed as it possessed two bands of fluorescence emission at 1.4 and 1.6 μm, which were perfectly complimentary to the current C band of optic communication. The fluorescence was based on energy transfer and up-conversion processes between Tm^3＋ and Yb^3＋ under direct pumping of 975 nm LD. The spectra and lifetimes of Tm^3＋ fluorescence in the tellurite glass were described. The corresponding fluorescence characteristics and energy migration process were analyzed by the method of lifetime and intensity comparison. The mechanism of the up-conversion based IR fluorescence was presented upon analyzing the multi-photon pumping process. The potential advantages of Tm^3＋/Yb^3＋ co-doped tellurite glass as amplifier material were concluded.

Fabrication of Gd_(2)O_(3)-doped CeO_(2)thin films through DC reactive sputtering and their application in solid oxide fuel cells

Physical vapor deposition(PVD)can be used to produce high-quality Gd_(2)O_(3)-doped CeO2(GDC)films.Among various PVD methods,reactive sputtering provides unique benefits,such as high deposition rates and easy upscaling for industrial applications.GDC thin films were successfully fabricated through reactive sputtering using a Gd_(0.2)Ce_(0.8)(at%)metallic target,and their application in solid oxide fuel cells,such as buffer layers between yttria-stabilized zirconia(YSZ)/La0.6Sr0.4Co0.2Fe0.8O_(3−δ)and as sublayers in the steel/coating system,was evaluated.First,the direct current(DC)reactive-sputtering behavior of the GdCe metallic target was determined.Then,the GDC films were deposited on NiO-YSZ/YSZ half-cells to investigate the influence of oxygen flow rate on the quality of annealed GDC films.The results demonstrated that reactive sputtering can be used to prepare thin and dense GDC buffer layers without high-temperature sintering.Furthermore,the cells with a sputtered GDC buffer layer showed better electrochemical performance than those with a screen-printed GDC buffer layer.In addition,the insertion of a GDC sublayer between the SUS441 interconnects and the Mn-Co spinel coatings contributed to the reduction of the oxidation rate for SUS441 at operating temperatures,according to the area-specific resistance tests.

Tm^(3+)高掺杂的NaYF_(4)纳米颗粒制备与发光性能研究

为了研究Tm^(3+)高掺杂浓度下NaYF_(4)纳米颗粒的上转换发光性能,采用热分解法合成了六方相的NaYF_(4)∶Yb^(3+)/Tm^(3+)(20%/8%)纳米颗粒,并用X射线衍射对其结构进行了表征,用透射电子显微镜对其形貌和大小进行了表征.通过搭建上转换光谱测试系统,研究了在980 nm激光激发下NaYF_(4)∶Yb^(3+)/Tm^(3+)纳米颗粒的上转换发光光谱,并分析了其发光机制.通过计算475,513,650,744,805 nm处发光强度与激发光功率间的依赖关系,证明了其上转换发光过程为双光子过程.

Upconversion Luminescence Properties of Ho^(3+),Tm^(3+),Yb^(3+) Co-Doped Nanocrystal NaYF_4 Synthesized by Hydrothermal Method

Nanocrystal of upconversion （UC） phosphor Ho^3＋, Tm^3＋ , and Yb^3＋ co-doped NaYF4 was prepared by the hydrothermal method in the presence of the complexing agent EDTA. Under 980 nm diode laser excitation, the impact of different concentrations of Ho^3＋ ion on the UC luminescence intensity was discussed. The law of luminescence intensity versus pump power shows that the 474 nm blue emission, 538 nm green emission, and 642 nm red emission are all due to the two-photon process, while the 450 nm blue emission is a three-photon process. The UC mechanism and processes were also analyzed. The sample was characterized by transmission electron microscopy （TEM） and X-ray diffraction （XRD）. The result shows that Ho^3＋ ,Tm^3＋ , and Yb^3＋ co-doped NaYF4 prepared by the hydrothermal method exhibits a hexagonal nanocrystal.

Up-conversion photoluminescence characteristics of Yb^(3+):Er^(3+):Tm^(3+) co-doped borosilicate glasses

Yb^3＋：Er^3＋：Tm^3＋co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb^3＋ Er^3＋ and Tm^3＋ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb^3＋ Stark splitting levels to pump Tm^3＋ ions and there exists an optimum pump power. The concentration of the Tm^3＋ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the yb^3＋：Er^3＋：Tm^3＋ co-doped borosilicate glasses.

Luminescent characteristics of Tm^(3+)/Tb^(3+)/Eu^(3+) tri-doped Na_(5)Y_(9)F_(32) single crystals for white emission with high thermal stability

By using an improved Bridgman method,0.3 mol%Tm^(3+)/0.6 mol%Tb^(3+)/y mol%Eu^(3+)(y=0,0.4,0.6,0.8)doped Na_(5)Y_(9)F_(32)single crystals were prepared.The x-ray diffraction,excitation spectra,emission spectra and fluorescence decay curves were used to explore the crystal structure and optical performance of the obtained samples.When excited by 362 nm light,the cool white emission was realized by Na_(5)Y_(9)F_(32)single crystal triply-doped with 0.3 mol%Tm^(3+)/0.6 mol%Tb^(3+)/0.8 mol%Eu^(3+),in which the Commission Internationale de l’Eclairage(CIE)chromaticity coordinate was(0.2995,0.3298)and the correlated color temperature(CCT)was 6586 K.The integrated normalized emission intensity of the tridoped single crystal at 448 K could keep 62%of that at 298 K.The internal quantum yield(QY)was calculated to be~15.16%by integrating spheres.These results suggested that the single crystals tri-doped with Tm^(3+),Tb^(3+)and Eu^(3+)ions have a promising potential application for white light-emitting diodes(w-LEDs).

The effects of Er^(3+) ion concentration on 2.0-μm emission performance in Ho^(3+)/Tm^(3+) co-doped Na_(5)Y_(9)F_(32) single crystal under 800-nm excitation

Na_(5)Y_(9)F_(32) single crystals doped with ~0.8-mol% Ho^(3+),~1-mol% Tm^(3+),and various Er^(3+) ion concentrations were prepared by a modified Bridgman method.The effects of Er^(3+)ion concentration on 2.0-μm emission excited by an800-nm laser diode were investigated with the help of their spectroscopic properties.The intensity of 2.0-μm emission reached to maximum when the Er^(3+) ion concentration was ~1 mol%.The energy transfer mechanisms between Er^(3+),Ho^(3+),and Tm^(3+) ions were identified from the change of the absorption spectra,the emission spectra,and the measured decay curves.The maximum 2.0-μm emission cross section of the Er^(3+)/Ho^(3+)/Tm^(3+)tri-doped Na_(5)Y_(9)F_(32) single crystal reached 5.26 × 10^(-21) cm^(2).The gain cross section spectra were calculated according to the absorption and emission cross section spectra.The cross section for ~2.0-μm emission became a positive gain once the inversion level of population was reached 30%.The energy transfer efficiency was further increased by 11.81% through the incorporation of Er^(3+) ion into Ho^(3+)/Tm^(3+) system estimated from the measured lifetimes of Ho^(3+)/Tm^(3+)-and Er^(3+)/Ho^(3+)/Tm^(3+)-doped Na_(5)Y_(9)F_(32)single crystals.The present results illustrated that the Er^(3+)/Ho^(3+)/Tm^(3+)tri-doped Na_(5)Y_(9)F_(32) single crystals can be used as promising candidate for 2.0-μm laser.

Yb^(3+)和Tm^(3+)共掺透明磷酸盐微晶盐玻璃上转换发光性能

采用熔融冷却法制备了掺杂不同比例Yb^(3+)和Tm^(3+)的磷酸盐玻璃,通过在630℃保温1 h得到透明的微晶玻璃,对样品进行XRD测试,表明析出的晶体为Na_(3.6)Y_(1.8)(PO_(4))_(3),通过Jade6.0计算和TEM分析,其晶粒尺寸均在20~40 nm之间,小于可见光波长,透过率光谱表明,经过热处理之后微晶玻璃仍保持70%以上的透过率。研究了前驱体玻璃和微晶玻璃在980 nm LD泵浦下的上转换荧光光谱,微晶玻璃的上转换效率明显高于前驱体玻璃,在上转换荧光光谱中,475 nm处发射强烈的上转换蓝光,654 nm处发射微弱的红光,795 nm处发射较弱的红外光。随着Yb^(3+)掺杂浓度的增加其上转换效率先增大后减小,Yb^(3+)的掺杂浓度为0.9%时,产生浓度猝灭现象。通过分析上转发光强度与激光器泵浦功率之间的关系,在Yb^(3+)和Tm^(3+)共掺的磷酸盐微晶玻璃中,上转换蓝光、红光和红外光的发射均为双光子过程。解释了Yb^(3+)和Tm^(3+)在磷酸盐微晶玻璃中的上转换发光机制。利用CIE1931计算,可知Yb^(3+)和Tm^(3+)共掺磷酸盐微晶玻璃的上转换发光色度坐标落在了蓝光区域,有望用在光学储存、全色显示、蓝色防伪、蓝光激光玻璃等领域。

K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料的制备及其光催化性能研究

上转换材料与光催化剂复合可以产生吸收光谱“红移”的效果,对提高光催化剂的降解效率具有重要意义。为了提高CdS对近红外光的利用率,通过高温固相反应法合成了冰晶石结构上转换发光材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+),并采用高能球磨法将其与CdS复合制备出一种新型光催化复合材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS。采用X射线粉末衍射(XRD)、场发射扫描电镜(SEM)、荧光光谱(PL)和紫外-可见漫反射吸收光谱对其成分、结构和性能进行了系统表征。同时,对不同复合比例下制备的复合催化剂对罗丹明B(RhB)的光降解效率和K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料的光催化机理进行了研究。结果表明,K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)和CdS的最佳复合比为3.6∶1,上转换发光材料K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)的引入协同促进了CdS的光催化作用,光催化过程中·OH与·O^(2-)均参与了对RhB的降解,并且·OH起主要作用。此外,在最佳复合比下,经过80 min,K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS样品降解率达到99.9%,与未复合的CdS相比,降解率提高了近50倍。所有结果表明K_(3)ScF_(6)∶Tm^(3+),Yb^(3+)/CdS光催化复合材料在光催化领域具有潜在的应用价值。

Dy^(3+)/Tm^(3+)掺杂Na_(2)Gd(PO_(4))(WO_(4))的制备及发光性能研究

采用二次熔融的高温固相法合成了一系列Dy^(3+)/Tm^(3+)共掺钠-钆-磷钨酸盐(NGPW)荧光材料,研究了其光致发光特性和热稳定性,以及CIE与激发波长的映射关系。改变激发波长可以让NGPW∶2%Tm^(3+),xDy^(3+)(x=1%、2%、3%、4%、5%)荧光粉的颜色从蓝色-冷白色-暖白色-黄色连续变化。在356nm和363nm激发下,可实现白光发射。对共掺杂荧光粉的荧光衰减曲线进行表征,验证了该荧光粉中Dy^(3+)和Tm^(3+)之间存在能量转移。详细研究了能量传递效率和能量传递机理。NGPW∶2%Tm^(3+),xDy^(3+)荧光粉有望成为极具潜力的色彩可调的单组分荧光粉。

Preparation and photoelectric properties of Ho^(3+)-doped titanium dioxide nanowire downconversion photoanode

Ho^3＋-doped titanium dioxide（TiO2：Ho^3＋） downconversion（DC） nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho（NO3）3 aqueous solution. Moreover, TiO2：Ho^3＋ nanowires（HTNWs） were used as the photoanode in dye-sensitized solar cells（DSSCs） to investigate their photoelectric properties. Scanning electron microscopy（SEM） and X-ray diffraction（XRD） were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet-visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency（η） of the DSSCs with HTNWs photoanode doped with 4% Ho2O3（mass fraction） is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density（Jsc） of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.

白光LED用YVO_(4)∶Tm^(3+)蓝色荧光粉的制备及发光性能

白光LED是指稀土掺杂的荧光粉被蓝光芯片或紫外芯片激发后获得各种室温发白光的器件。该种光致发光的实现方式是一种新型全固态照明光源,具有节能、环保及绿色照明等优点,被誉为第四代照明光源。对于现代设施农业,480~500nm之间的蓝光有一种调整植物节律的作用,对植物生长是有益的。蓝光在绿色植物的光合作用和光形态中起着重要的作用,绿色植物通过叶绿素、胡萝卜素、叶黄素和光敏素来捕获太阳光进行光合作用,适合植物生长的LED灯可提高光合作用效率,但传统的光源由于光质问题难以调节光波长,在这种情况下,需要将太阳光谱成分中380 nm以下的紫外光转换成蓝光,可提高作物光能利用率。所以,高光效、高热稳定性蓝色荧光粉已成为全光谱照明、光生态农业等领域的重要材料。蓝色荧光材料在近紫外(NUV)芯片激发的白光用发光二极管(W-LED)的制造中起重要作用。采用高温固相法制备YVO_(4)∶Tm^(3+)蓝色荧光粉,通过X射线衍射仪、扫描电子显微镜、荧光光谱仪等检测手段对样品的物相结构、表观形貌及发光性能进行表征分析。结果表明:通过高温固相法1100℃下煅烧2 h可以制备出YVO_(4)∶Tm^(3+)蓝色荧光粉,粉体呈2μm左右的球形,激发峰位于319 nm紫外区域,发射峰位于479 nm蓝光区域,样品色坐标位于(0.1044,0.1224),是一种有望应用于白光LED的蓝色荧光粉。

Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃的上转换发光及其温度传感特性

通过传统的熔融淬火技术以及后续热处理法制备了Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃。通过DTA和XRD研究其热性质和LaF_(3)纳米晶的可控析出。通过透过光谱和上转换发光光谱研究了玻璃的光学性能。利用荧光强度比(FIR)技术研究了微晶玻璃样品在980 nm激光激发下的上转换发光光谱与温度的依赖关系。研究发现,该微晶玻璃样品在313~573 K温度范围内的最大绝对灵敏度Sa和最大相对灵敏度Sr分别为2.6×10^(-4)K^(-1)(573 K)和2.3×10^(-2)K^(-1)(313 K)。结果表明,Tm^(3+)/Yb^(3+)共掺含LaF_(3)纳米晶锗酸盐微晶玻璃在温度传感领域具有潜在的应用前景。

Preparation and characterization of Eu^(3+)-doped CaCO_3 phosphor by microwave synthesis

A Eu^3＋-doped CaCO3 phosphor with red emission was prepared by microwave synthesis. The scanning electron microscopy （SEM） image and laser particle size analysis show that the CaCO3：Eu^3＋ particles are needle-like in the length range of 5.0-10.0 μm. The results of X-ray diffraction （XRD） analysis, Fourier transform infrared spectroscopy （FT-IR）, and Raman spectroscopy indicate that pure aragonite CaCO3：Eu^3＋ is prepared using microwave irradiation and the Eu^3＋ ion as a luminescence center inhabits the site of Ca^2＋. The photoluminescence excitation （PLE） spectrum shows that the strong broad band at around 270 nm and weak sharp lines in 300-550 nm are assigned to the charge transfer band of Eu^3＋-O^2- and intra-configurational 4f-4f transitions of Eu^3＋, respectively. The photoluminescence （PL） spectrum implies that the red luminescence can be attributed to the transitions from the ^5D0 excited level to the ^7FJ （J = 0, 1, 2, 3, 4） levels of Eu^3＋ ions with the mainly electric dipole transition ^5D0 → ^7F2 （614 and 620 nm）, and the Eu^3＋ ions prefer to occupy the low symmetric site in the crystal lattice.

Characterization of the BaBiO_3-doped BaTiO_3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with T_c=155℃

BaBiO3-doped BaTiO3 （BB-BT） ceramic, as a candidate for lead-free positive temperature coefficient of resistivity （PTCR） materials with a higher Curie temperature, has been synthesized in air by a conventional sintering technique. The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature, Tc = 155℃, which is higher than that of BaTiO3 （≤ 130 ℃）. Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current （AC） resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data, the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature, indicating that the increase in overall resistivity is entirely due to a grain-boundary effect. Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency, the conduction mechanism is also discussed for a BB-BT ceramic system.

Green and red up-conversion emissions and thermometric application of Er^(3+) -doped silicate glass

The green and red up-conversion emissions centred at about 534, 549 and 663 nm of wavelength, corresponding respectively to the ^2H11/2 → ^4I15/2, ^4S3/2 → ^4I15/2 and ^4F9/2 → ^4I15/2 transitions of Er^3＋ ions, have been observed for the Er^3＋-doped silicate glass excited by a 978 nm semiconductor laser beam. Excitation power dependent behaviour of the up-conversion emission intensity indicates that a two-photon absorption up-conversion process is responsible for the green and red up-conversion emissions. The temperature dependence of the green up-conversion emissions is also studied in a temperature range of 296-673 K, which shows that Er^3＋-doped silicate glass can be used as a sensor in high-temperature measurement.

Promotional effect for SCR of NO with CO over MnO_(x)-doped Fe_(3)O_(4) nanoparticles derived from metal-organic frameworks

MnO_(x)-Fe_(3)O_(4) nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganesedoped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO(CO-SCR).Multi-technology characterizations were conducted to ascertain the properties of fabricated materials(e.g.,TGA,XRD,SEM,FT-IR,XPS,BET,H_(2)-TPR and O_(2)-TPD).Moreover,the interaction between reactants and catalysts was ascertained by in situ FT-IR.Experimental results demonstrated that Mn was an ideal promoter for iron oxides,resulting in decrease of crystallite size,improve reducibility property,enhance the mobility and the amount of lattice O^(2-) species,as well as strength the adsorption ability of active NO and CO to form multiple species(e.g.,nitrate and carbonate).The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal(E-R)and Langmuir-Hinshelwood(L-H)reaction pathway.

Three-photon-excited fluorescence of Tb^(3+)-doped CaO-Al_2O_3-SiO_2 glass by femtosecond laser irradiation

A near infrared to visible blue, green, and red upconversion luminescence in a Tb^3＋-doped CaO-Al2O3-SiO2 glass was studied, which was excited using 800 nm femtosecond laser irradiation. The upconversion luminescence was attributed to ^5D3→^7F5, ^5D3→^7F4, ^5D3→^7F3, ^5D4→^7F6, ^5D4→^7F5, ^5D4→^7F4, and ^5D4→^7F3 transitions of Tb^3＋. The relationship between upconversion luminescence intensity and the pump power indicated that a three-photon simultaneous absorption process was dominant in this upconversion luminescence. The intense red, green, and blue upconversion luminescence of Tb^3＋-doped CaO-Al2O3-SiO2 glass may be potentially useful in developing three-dimensional display applications.