过渡金属Mn离子掺杂的半导体纳米晶研究进展

过渡金属掺杂的纳米材料具有高效、稳定和可调谐的可见-近红外发射光谱的特点,尤其是由于大的斯托克斯位移而抑制了发光材料自吸收的问题,已经成为光学材料中一个重要的分支。回顾了关于Mn离子掺杂纳米晶研究进展中的几个关键问题。得到晶核掺杂和生长掺杂方式相比于传统的"一锅法"在制备方式更有优势;从回顾关于Mn掺杂机理上的各种解释和在宿主纳米晶中引入大量的掺杂剂所面临的困难中,得出要获得掺杂浓度可控的量子点需要考虑纳米晶表面自清洁效应,纳米晶形状、晶体结构、晶面、表面活性剂以及Mn离子与宿主阳离子的尺寸差别引入的晶格压力等关键因素;利用理论和实验深刻解释了Mn离子的发光机理,指出宿主到Mn离子的高能量转移速率是获得高效的Mn离子发光的关键因素。通过对掺杂量子点的制备、掺杂机理以及发光机理的综合探讨,为制备掺杂浓度和掺杂位置可控的光学性能优良的掺杂量子点方面的研究提供参考。     

高发光强度上转换材料Y2O3 ∶Er,Yb纳米晶的制备

将反相乳液合成方法与水热处理方法相结合, 获得Y₂O₃ ∶Er,Yb纳米晶的前驱体, 经过一定温度灼烧, 获得了高发光强度的上转换Y₂O₃ ∶Er,Yb 纳米晶,经水热处理的纳米晶样品具有更好的晶体结构, 有利于激发电子在Er离子^{4F_9/2能级上的分布，进而导致红色发射强度极大地提高.}     

Energy transfer process between Eu3+ and wide-band-gap SnO2 nanocrystals in silica films studied by photoluminescence excitation and time-resolved photoluminescence techniques

Eu3+ions embedded in silica thin films codoped with SnO2 nanocrystals were fabricated by sol–gel and spin-coating methods.SnO2 nanocrystals with controllable sizes were synthesized through precisely controlling the Sn concentrations.The influences of doping and annealing conditions on the photoluminescence intensity from SnO2 nanocrystals are systematically investigated.The effective energy transfer from the defect states of SnO2nanocrystals to nearby Eu3+ions has revealed by the selective photoluminescence excitation spectra.The efficiency of the Forster resonance energy transfer is evaluated by the time-resolved photoluminescence measurements,which is about 29.1%based on the lifetime tests of the SnO2emission.     

Cu含量对喷射成形7055铝合金微观组织和力学性能的影响

通过拉伸试验、冲击试验以及微观组织观察试验,分析降低Cu含量对喷射成形7055铝合金强度、断裂韧性和微观组织的影响。力学性能试验表明,7055铝合金中Cu的质量分数由2.55%降低到2.17%时,对其强度和伸长率影响不大,但Cu含量降低后合金的断裂韧性显著提高。微观组织分析表明,Cu含量降低前晶界上存在粗大的Al₇Cu₂Fe相,Cu含量降低后晶界上的粗大析出相明显减少;断口分析表明,Cu含量降低前拉伸断口中存在较多的Al₇Cu₂Fe第二相,Cu含量降低后Al₇Cu₂Fe第二相明显减少。     

Gold-catalytic green synthesis of Cu2O/Au/CuO hierarchical nanostructure and application for CO gas sensor

Hierarchical Cu20/Au/CuO nanostructures have been achieved by water-based green fabrication at a low temperature. Precluding the requirement of the tem- plate removal, the generation of hierarchical architecture relied on the catalytic activity of gold nanoparticles attached on the Cu20 nanocubes. Notably, we creatively developed the dual-roles catalytic ability of gold, which not only remarkably increased the specific surface area of this architecture, but also provided the enhanced performance for gas sensing.     

Enhancement of magnetism of Zn0.95Co0.05O films by p-type Cu+ doping

Organic solar cells withμ-oxo-bridged gallium phthalocyanine dimer(GaPc dimer) and fullerene were produced by an evaporation method.A device based on the GaPc dimer provided a conversion efficiency of 4.2×10~(-3)%,which is better compared to a device based on phthalocyanine monomer.Dimerization effect was discussed with a molecular orbital calculation,and the crystalline phases of the present solar cells were investigated by X-ray diffraction.Further improvement of the efficiency was discussed on the bas...     

La0.7Ca0.3Mn1-xCuxO3的电输运特性

通过固相反应法制备不同掺杂浓度的La_0.7Ca_0.3Mn_1-xCu_xO₃（x=0~0.15）样品, 在77~300 K温度范围内测量了铜掺杂后样品电阻随温度的变化关系. 结果表明, 在未引入铜杂质时, 低温铁磁相的电阻率满足T^2.5关系, 顺磁相符合小极化子近邻跳跃模型; 在低掺杂下, 铁磁区可用T^4.5关系解释; 随着掺杂浓度的增加, 在铁磁区和顺磁区, 任何单一模型均与实验不相符, 表明高掺杂样品的电输运性质存在未知模型.      

Doping effect on thermoelectric properties of nonstoichiometric AgSbTe<Subscript>2</Subscript> compounds

Nonstoichiometric ternary thermoelectric materials Ag_0.84Sb_1.15M_0.01Te_2.16 (M=Ce, Yb, Cu) were prepared by a direct melt-quench and hot press process. The carrier concentration of all the samples increased after doping. Thermoelectric properties, namely electrical conductivity, Seebeck coefficient, and thermal conductivity, were measured from 300 to 673 K. The phase transition occurring at about 418 K representing the phase transition from β-Ag₂Te to α-Ag₂Te influenced the electrical transport properties. The electrical conductivities of Ce and Yb doped samples increased after doping from 1.9×10⁴ to 2.5×10⁴ and 2.3×10⁴ S·m⁻¹, respectively, at 673 K. Also, at room temperature, the Seebeck coefficient of the Ce doped sample relatively increased corresponding to the high carrier concentration due to the changes in the band structure. However, all the thermal conductivities increased after doping at low temperature. Because of the higher thermal conductivity, the dimensionless figure of merit ZT of these doped samples has not been improved.     

Effect of temperature and pH value on cation exchange performance of a natural clay for selective (Cu2t, Co2t) removal: Equilibrium, sorption and kinetics

This work aims at investigating the strain effect,created by varying pH solution and continuous heating cycle,on the cation exchange process in the case of Na-rich montmorillonite sample in contact with bi-ionic solution with variable concentration,saturated respectively by Co2+ and Cu2+ cations.The ionic exchange process is characterized using XRD analysis obtained through the comparison of experimental XRD patterns with calculated ones,which allowed us to determine several structural parameters related to the nature,abundance,size,position and organization of exchangeable cation and water molecule in the interlamellar space along the caxis.Indeed,the proposed theoretical models,for the stressed samples,show that the structure presents an interstratified hydration character and proves the coexistence of more than two ’’crystallite’’ specie in the structure.The perturbation types have an obvious effect on the selective exchange process for all stressed samples,where the interlayer space is characterized by the coexistence of more one exchangeable cation.     

Structure and transport studies on nanometer YBCO/PBCGO multilayers

We have fabricated M doped （M = Al, Co, Fe, Ga, Ni and Zn） PrBa2Cu3O7（PBCO）, i.e. PrBa2（CU1-xMx）3O7. The doping levels x are 0.05, 0.10, 0.15, and 0.20. X-ray data indicated no significant second phase for substituting Cu by Al, Co, Fe and Ga up to 20%. However impurity phases were detected for Ni and Zn substituted samples with doping levels equal to and higher than 15%. At 77 K the electrical resistivity of these compounds is orders in magnitude higher than that of PBCO. We also found that although the lattice parameters in the doped samples differ from PBCO, all samples remain orthorhombic. The lattice parameters of the doped sample are very close to those of YBa2CU3O7-δ （YBCO） and PBCO. For this reason these compounds are better materials to be used as the I-layer for YBCO SIS junctions. Results of structural and transport studies on 2000 A thick PrBa2[Cu0.80G0.2]3O7 （PBCGO） and YBCO/PBCGO multilayers are presented in this paper.     

Spreading kinetics of a Sn-30Bi-0.5Cu alloy on a Cu substrate

The reactive wetting kinetics of a Sn-30Bi-0.5Cu Pb-free solder alloy on a Cu substrate was investigated by the sessile drop method from 493 to 623 K.The triple line frontier,characterized by the drop base radius R was recorded dynamically with a high resolution CCD using different spreading processes in an Ar-H 2 flow.We found a good agreement with the De Gennes model for the relationship between ln(dR/dt) and lnR for the spreading processes at 493 and 523 K.However,a significant deviation from the De Gennes model was found for the spreading processes at 548 and 623 K.Our experimental results show a complicated temperature effect on the spreading kinetics.Intermetallics at the Sn-30Bi-0.5Cu/Cu interface were identified as Cu 6 Sn 5 adjacent to the solder and Cu 3 Sn adjacent to the Cu substrate.The intermetallic compounds effectively enhanced the triple line mobility because of reaction product formation at the diffusion frontier.     

Synthesis and structure of Cu5(BTA)6(TTA)4 · 5DMF, a copper-nitrogen cluster containing η Π3-benzotriazolate

The title cluster compound—Cu₅(BTA)₆(TTA)₄·5DMF was prepared using thenyltrifluoroacetone and benzotriazolate ligands. The crystal structure indicates that a tetrahedral array of Cu(1), Cu(2), Cu(3) and Cu(4) ions surrounding a central Cu(5) ion are held together by bridging tridentate BTA^- and terminated by TTA^- bond cap. The three nitrogen atoms of a BTA^- bond three different copper ions to form a η³-benzotriazolate. The central Cu ion has a distorted octahedral structure and the surrounding Cu ions are 5 coordinated forming distorted tetragonal structures. The distances between the surrounding Cu(Ⅱ) ions and the central Cu(Ⅱ) ion are in the range of 0.3561—0.3755 nm and those between the surrounding Cu(Ⅱ) ions are in the range of 0.5785—0.6301 nm.     

滹沱河地下水超采区人工回灌的水岩相互作用模拟

人工回灌条件下回灌水与地下水混合带的水岩相互作用是决定地下水水质演化和含水层发生化学堵塞的关键过程。为研究人工回灌对滹沱河地下水超采区水质演化的影响,以石家庄市人工回灌场地为例,利用石津灌渠水作为回灌水源,通过室内实验结合反向水文地球化学模拟揭示回灌层位地表水与地下水混合带的水-岩相互作用机理。结果显示：混合带水的TDS（total dissolved solids）变化特征表现为先增大后缓慢降低,且地表水占比越大、含水介质粒径越细,则其变幅越大;混合带水中主要离子质量浓度变化特征受混合、碳酸平衡、溶解-沉淀、阳离子交换及硝化作用控制,其中K⁺、Ca²⁺、SO₄^2-质量浓度主要受溶解-沉淀作用控制,Na⁺、Cl^-、HCO₃^-、NO₃^-质量浓度主要受混合NO₃^-作用控制,Mg²⁺质量浓度主要受阳离子交换作用...     

Internal energy transfer phenomenon and light-emission properties of γ-LiAlO2 phosphor doped with Mn2+

γ-LiAlO₂:Mn²⁺ phosphor was synthesized using the cellulose-citric acid sol-gel method, and its light emission and energy transfer properties were investigated. Excitation and emission spectrum analysis revealed a decrease in intensity of the spectrum as the amount of Mn²⁺ doping increased. Blasse’s equation determined the maximum distance for energy transfer between Mn²⁺ ions as 4.3142 nm. Dexter’s theory verifies that the mechanism of energy transfer between Mn²⁺ ions conforms to an electric dipole and electric quadrupole interaction.     

Effects of Ce, Y, and Sm doping on the thermoelectric properties of Bi2Te3 alloy

Nanopowders of elements doped Bi2Te3thermoelectric alloy R0.2Bi1.8Te3(R Ce,Y and Sm)were synthesized by the hydrothermal method.The nanopowders were hot-pressed into pellets and their thermoelectric properties were investigated.The results show that Ce,Y,and Sm doping has signifcant effects on the morphologies of the synthesized nanopowders and thermoelectric properties.Among the doping elements,Ce doping is a superiority dopant.Although the electrical conductivity and Seebeck coeffcient are not improved much by Ce doping,the thermal conductivity is supressed greatly.As a result the fgure of merit(ZT) of Ce0.2Bi1.8Te3is improved and reaches 1.29 at 398 K,which is higher than the Bi2Te3ingots made by the traditional zone-melting method     

铜掺杂纳米氧化锌薄膜的制备及光学特性

氧化锌（ZnO）是一种新型稀磁半导体材料,有优良的磁学及光学性质,透明度高,常温发光性能优异.根据半导体掺杂原理,以氧化锌为原料,过渡金属元素铜为掺杂元素,采用化学气相沉积法（CVD）,制备了铜掺杂纳米氧化锌薄膜.利用晶向显微镜观察ZnO：Cu在衬底硅片上的表面形貌和生长情况,利用光致发光谱和分光光度计分析了样品的光发射和光吸收特性,研究了薄膜的伏安特性.发现铜掺杂对氧化锌薄膜的光吸收和光发射以及表面伏安特性都有很大的影响.随铜掺杂含量的增加,光吸收强度明显增大,光发射峰更加丰富.适当掺杂量的情况下,电流明显增大,但掺杂量太大,会引入缺陷和晶界,反而会使漏电流增大.10％-20％掺杂量为比较理想的掺杂量.     

用壳聚糖脱除废水中的铜离子

研究了利用脱乙酰基壳聚糖絮凝剂絮凝除铜的方法.考察了氢氧化物、pH值、铜离子质量浓度、絮凝时间以及絮凝温度对去除率的影响.当pH=8时,用壳聚糖吸附铜离子,水样铜离子质量浓度低于100 mg.L-1时,除铜率在99%以上;即使铜离子原始质量浓度在400 mg.L-1,残液铜离子质量浓度仍符合国家废水排放标准.用NaOH絮凝沉淀,pH=11时,除铜率达100%,耗碱量大,不符合废水排放的酸度要求.     

中温SOFC阴极材料La0.7Sr0.3Co1-xCuxO3-δ的制备及性能

采用固相反应法制备了La_0.7Sr_0.3Co_1-xCu_xO_3-δ系列中温固体氧化物燃料电池（SOFC）阴极材料粉体.对其进行晶体结构表征,高温电导率和热膨胀曲线测试,并选取其中性能较好的样品进行了单电池实验.结果表明,Cu的掺杂降低了（La,Sr）CoO La₃体系阴极材料的热膨胀系数,在x=0.05时电导率略高于未掺Cu的样品.以La_0.7Sr_0.3Co_0.95Cu _0.05O _3-δ为阴极、Ce_0.8Sm_0.2O_1.9为电解质组成的SOFC单电池,在850℃最大短路电流密度达511mA/cm²,最大输出功率密度约为0.106W/cm².     

Preparation of spherical ultrafine copper powder via hydrogen reduction-densification of Mg(OH)2-coated Cu2O powder

A novel process was developed to produce spherical copper powder for multilayer ceramic capacitors (MLCC). Spherical ultrafine cuprous oxide (Cu₂O) powder was prepared by glucose reduction of Cu(OH)₂. The Cu₂O particles were coated by Mg(OH)₂ and reduced to metallic copper particles. At last, the copper particles were densified by high-temperature heat treatment. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), tap density, and thermogravimetry (TG). It is found that the shape and size distribution of the copper powder are determined by the Cu₂O powder and the copper particles do not agglomerate during high-temperature heat treatment because of the existence of Mg(OH)₂ coating. After densification at high temperature, the particle tap density increases from 3.30 to 4.18 g/cm³ and the initial oxidation temperature rises from 125 to 150°C.     

Electronic structure of doped trans-polyacetylene

The behavior of electronic structures of doped trans-polyacetylene is revealed by a simple method. (C₂₄H₂₆)⁺ⁿ is used to simulate p-type doped trans-polyacetylene at various doping concentrations. The electronic structure is calculated, by CNDO/2 method. These calculations show that at low doping level, the decrease of electronic energy compensates the increase of elastic energy, thus the bond alternation exists, and the charge carriers are solitons. When doping level is high, the increase of elastic energy is larger than the decrease, of electronic energy, the bond alternation disappears, solitons no longer exist, and polyacetylene is in a metalic state. Foundation item: Supported by the National Natural Science Foundation of China (No. 19834070) Biography: Ren Da-zhi (1948-), male, Associate professor, research direction: solid state physics.