纳米晶Y2SiO5：Eu的浓度猝灭研究

报道了分别用溶胶-凝胶法合成的Y₂SiO₅:Eu纳米晶和用高温固相法合成常规尺度的Y₂SiO₅:Eu材料的光致发光光谱和猝灭浓度的实验研究.结果表明:纳米Y_2-xEu_xSiO₅比常规尺度的Y_2-xEu_xSiO₅有更高的猝灭浓度和更高的发光亮度.理论分析认为这是由于在纳米材料中能量共振传递被阻断和猝灭中心在各个纳米晶内分布的涨落造成的.这个结果为高亮度的Y₂SiO₅:Eu纳米材料的实际开发应用展示了广阔前景.     

矿物药炉甘石煅制前后锌、铅元素的赋存形态及分布特征研究

采用X射线衍射(XRD)技术和电子探针微区分析(EPMA)技术针对中药炉甘石煅制前后锌、铅元素的赋存形态及分布特征进行了研究,探明了煅制对炉甘石中锌、铅元素赋存状态及分布的改变,为后续水飞减除铅元素的机理研究提供了理论依据。测试结果显示：21批次炉甘石(生品)中的锌元素以主矿物水锌矿[Zn₅(CO₃)₂(OH)₆]和杂质矿物异极矿[Zn₄(OH)₂(H₂O)(Si₂O₇)]为主要赋存形态,偶见菱锌矿(ZnCO₃);炉甘石(生品)的背散射电子图谱及元素分布数据显示：Zn和Pb元素同时分布的区域为水锌矿,Zn和Si元素同时分布的区域为异极矿,Ca和Mg元素同时分布的区域为白云石,Ca元素单独分布区域为方解石。在炉甘石(生品)中,Pb主要分布于水锌矿中且分布相对均匀,Pb元素的分布与水锌矿中的Zn元素密切相关。大量水锌矿的微区点位的电子探针定量分析结果显示：各不同点位中的ZnO/PbO含量的比值趋于定值,Pb在水锌矿中呈统计式均匀分布,说明Pb在水锌矿中主要以类质同象混入物的形式存在。但是炉甘石(生品)中的异极矿、方解石及白云石等杂质矿物中铅元素含量极低甚至检测不到。炉甘石煅烧后水锌矿晶格中的Zn和Pb分别生成了ZnO和PbO。Zn元素在炉甘石煅制品中主要以氧化锌(ZnO)形式存在,少部分以杂质矿物硅酸锌(Zn₂SiO₄)形式存在,呈较连续状态分布。Pb元素在炉甘石煅制品中主要以氧化铅(PbO)的形式存在,呈星点状分布,与Zn元素的分布未呈现相关性,说明Pb在炉甘石煅制品中是以独立矿物形式存在的。煅烧破坏了水锌矿的晶格结构,在改变锌、铅化合物形态的同时,更改变了锌、铅的分布特征,打破了炉甘石中锌、铅的共生状态,使水飞减除铅元素成为可能。     

新型固态照明用发光材料Ca3SiO4Br2:Eu2+的合成、结构与发光性能

制备了一种Eu2+掺杂的新型Ca3SiO4Br2蓝色发光材料,详细研究了其晶体结构组成.采用助熔剂法生长出Ca3SiO4Br2片状单晶,解析并证实该晶体为Ca3SiO4Br2,其结构基元中存在交替排列的Ca2SiO4和CaBr2层.荧光光谱测试表明:Ca3 SiO4Br2:Eu2+材料可被近紫外光( 300～ 430 ...     

Zn2SiO4(ZnB2O4):Mn2+,Sm3+发光材料的制备与荧光性能

使用高温固相法首次合成了Zn2SiO4(ZnB2O4):Mn2+,Sm3+发光材料,探讨了烧结温度、Sm2+含量对样品荧光性能的影响.利用X射线衍射(XRD)、荧光光谱等分析手段对Zn2SiO4(ZnB2O4):Mn2+,Sm3+粉末的结构、发光性能进行了表征.确定了该荧光材料的最佳合成条件,离子掺杂浓度等.实验结果表...     

过渡金属与F共掺杂ZnO薄膜结构及磁、光特性

采用溶胶-凝胶法在玻璃衬底上制备了过渡金属元素与F共掺杂Zn_0.98-xTM_xF_0.02O (TM_x=Cu_0.02, Ni_0.01, Mn_0.05, Fe_0.02, Co_0.05)薄膜, 进而利用X射线衍射仪、扫描电子显微镜、紫外-可见透过谱、光致发光及振动样品磁强计等研究了薄膜的表面形貌、微结构、禁带宽度及光致发光(PL)和室温磁学特性. 研究表明: 掺杂离子都以替位的方式进入了ZnO晶格, 掺杂不会破坏ZnO的纤锌矿结构. 其中Zn_0.93Co_0.05F_0.02O薄膜样品的颗粒尺寸最大, 薄膜的结晶度最好且c轴择优取向明显; Zn_0.93Mn_0.05F_0.02O薄膜样品的颗粒尺寸最小, 薄膜结晶度最差且无明显的c轴择优取; Cu, Ni, Fe与F共掺杂样品的颗粒尺寸大小几乎相同. TM掺杂样品均表现出很高的透过率, 同时掺杂后的薄膜样品的禁带宽度都有不同程度的红移. PL谱观察到Zn_0.98-xTM_xF_0.02O薄膜的发射峰主要由较强的紫外发射峰和较弱的蓝光发射峰组成. Zn_0.93Mn_0.05F_0.02O薄膜样品的紫外发光峰最弱, 蓝光发射最强, 饱和磁化强度最大; 与之相反的是Zn_0.96Cu_0.02F_0.02O薄膜, 其紫外发光峰最强, 蓝光发射最弱, 饱和磁化强度最小. 结合微结构和光学性质对Zn_0.98-xTM_xF_0.02O薄膜的磁学性质进行了讨论.     

Growth behaviors and emission properties of Co-deposited MAPbI3 ultrathin films on MoS2

Hybrid organic-inorganic perovskite thin films have attracted much attention in optoelectronic and information fields because of their intriguing properties. Due to quantum confinement effects, ultrathin films in nm scale usually show special properties. Here, we report on the growth of methylammonium lead iodide (MAPbI₃) ultrathin films via co-deposition of PbI₂ and CH₃NH₃I (MAI) on chemical-vapor-deposition-grown monolayer MoS₂ as well as the corresponding photoluminescence (PL) properties at different growing stages. Atomic force microscopy and scanning electron microscopy measurements reveal the MoS₂ tuned growth of MAPbI₃ in a Stranski-Krastanov mode. PL and Kelvin probe force microscopy results confirm that MAPbI₃/MoS₂ heterostructures have a type-II energy level alignment at the interface. Temperaturedependent PL measurements on layered MAPbI₃ (at the initial stage) and on MAPbI₃ crystals in averaged size of 500 nm (at the later stage) show rather different temperature dependence as well as the phase transitions from tetragonal to orthorhombic at 120 and 150 K, respectively. Our findings are useful in fabricating MAPbI₃/transition-metal dichalcogenide based innovative devices for wider optoelectronic applications.     

Magneto-optical properties and exciton dynamics in diluted magnetic semiconductor nanostructures

Nanostructures of diluted magnetic semiconductors were fabricated to study novel magneto-optical properties that are derived from quantum confined band electrons interacting with magnetic ions. Quantum dots (QDs) of Cd_0.97Mn_0.03Se were grown by the self-organization on a ZnSe substrate layer. QDs of Zn_0.69Cd_0.23Mn_0.08Se and quantum wires (QWRs) of Cd_0.92Mn_0.08Se and Zn_0.69Cd_0.23Mn_0.08Se were fabricated by the electron beam lithography. A single quantum well (QW) of ZnTe/Zn_0.97Mn_0.03Te and double QWs of Cd_0.95Mn_0.05Te–CdTe were grown by molecular beam epitaxy. Magneto-optical properties and the formation and relaxation dynamics of excitons were investigated by ultrafast time-resolved photoluminescence (PL) spectroscopy. Excitons in these nanostructures were affected by the low-dimensional confinement effects and the interaction with magnetic ion spins. The exciton luminescence of the Cd_0.97Mn_0.03Se QDs shows the confined exciton energy due to the dot size of 4–6 nm and also shows marked increase of the exciton lifetime with increasing the magnetic field. The QDs of Zn_0.69Cd_0.23Mn_0.08Se fabricated by the electron beam lithography display narrow exciton PL spectrum due to the uniform shape of the dots. The exciton luminescence from the QWRs of Cd_0.92Mn_0.08Se and Zn_0.69Cd_0.23Mn_0.08Se shows the influence of the one-dimensional confinement effect for the exciton energy and the luminescence is linearly polarized parallel to the wire direction. The transient PL from the ZnTe/Zn_0.97Mn_0.03Te QWs displays, by the magnetic field, the level crossing of the exciton spin states of the nonmagnetic and magnetic layers and the spatial spin separation for the excitons. Cd_0.95Mn_0.05Te–CdTe double QWs show the injection of the spin polarized excitons from the magnetic well to the nonmagnetic QW.     

Enhanced photoluminescence of monolayer MoS2 on stepped gold structure

Different MoS₂/Au heterostructures can play an important role in tuning the photoluminescence (PL) and optoelectrical properties of monolayer MoS₂. Previous studies of PL of MoS₂/Au heterostructures were mainly limited to the PL enhancement by using different Au nanostructures and PL quenching of monolayer MoS₂ on flat Au surfaces. Here, we demonstrate the enhanced excitonic PL emissions of monolayer MoS₂/Au heterostructures on Si/SiO₂ substrates. By transferring the continuous monolayer MoS₂ onto a stepped Au structure consisting of 60-nm and 100-nm Au films, the MoS₂/Au-60 and MoS₂/Au-100 heterostructures exhibit enhanced PL emissions, each with a blue-shifted PL peak in comparison with the MoS₂/SiO₂. Furthermore, the PL intensity of MoS₂/Au-60 is about twice larger than that of MoS₂/Au-100. The different enhanced excitonic PL emissions in MoS₂/Au heterostructures can be attributed to the different charge transfer effects modified by the stepped Au structure. This work may provide an insight into the excitonic PL and charge transfer effect of MoS₂ on Au film and yield novel phenomena in MoS₂/Au heterostructures for further study of PL tuning and optoelectrical properties.     

新型Ba3SiO5:Eu荧光粉的合成及光谱性质

以BaCO_3、SiO_2、Eu_2O_3为原料在还原气氛下采用高温固相法制备了Ba_3SiO_5∶Eu荧光粉体。实验结果表明,制备Ba_3SiO_5的最佳工艺条件是Ba/Si比为3,1 200℃保温4 h。光谱分析表明,Ba_3SiO_5∶Eu荧光粉在254,365,410 nm激发下发射主峰为566 nm(Eu~(2+)的4f~n~(-1)5d→4f~n)宽带发射,量子效率分别为70%、50%、10%,荧光寿命为百纳秒级;以566 nm为监视波长测得激发谱为主峰在250～450 nm范围内的宽带发射,主峰为360 nm,且在410 nm出现小峰; Eu离子最佳掺杂浓度为5%,由发光强度随掺杂离子浓度变化曲线,可以得出Ba_3SiO_5中Eu离子能量传递是基于电四级-电四级作用。     

Effects of silver and gold catalytic activities on the structural and optical properties of silicon nanowires

The metal-assisted chemical etching of silicon in an aqueous solution of hydrofluoric acid and hydrogen peroxide is established for the fabrication of large area, uniform silicon nanowire (SiNW) arrays. In this study, silver (Ag) and gold (Au) are considered as catalysts and the effect of different catalysts with various thicknesses on the structural and optical properties of the fabricated SiNWs is investigated. The morphology of deposited catalysts on the silicon wafer is characterized by atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). It is shown that the morphology of the fabricated silicon nanostructures remarkably depends upon the catalyst layer thickness, and the catalyst etching time directly affects the structural and optical properties of the synthesized SiNWs. FESEM images show a linear increment of the nanowire length versus time, whereas the etching rate for the Au-etched SiNWs was lower than the Ag-etched ones. Strong light scattering in SiNWs caused the total reflection to decrease in the range of visible light, and this decrement was higher for the Ag-etched SiNW sample, with a longer length than the Au-etched one. A broadband visible photoluminescence (PL) with different peak positions is observed for the Au- and Ag-etched samples. The synthesized optically active SiNWs can be considered as a promising candidate for a new generation of nano-scale opto-electronic devices.     

纳米Sr2SiO4∶Eu3+荧光粉的燃烧法合成及光谱性质

利用快速燃烧合成方法制备了Sr2SiO4∶Eu3+纳米材料.用X射线粉末衍射、扫描电镜、稳态激发与发射光谱、高分辨发射光谱、位置选择激发光谱和发光衰减等测量对材料的结构、形貌和光致发光性质进行了研究.分析结果表明,通过二甲酰肼的快速燃烧,在800℃条件下反应3 min即可制得颗粒尺寸在80～100nm左右的α-Sr2S...     

Fe、Ni共掺杂ZnO基稀磁半导体光学性能与铁磁性研究

采用水热法成功制备了不同掺杂浓度的Zn_1-2xFe_xNi_xO（x=0,0.025,0.05,0.1）稀磁半导体材料,利用X射线衍射（XRD）、透射电子显微镜（TEM）和X射线能量色散分析仪（XEDS）对样品进行表征,并结合拉曼（Raman）光谱、光致发光光谱（PL）和振动样品磁强计（VSM）研究样品的光学性能和磁学性能。结果表明,水热法制备的样品具有结晶性良好的纤锌矿结构,没有杂峰出现,形貌为纳米棒状结构,分散性良好。Fe²⁺、Ni²⁺是以替代的形式进入ZnO晶格中,Fe和Ni的掺杂使得晶体中的缺陷和应力增加,拉曼光谱峰位发生红移,光致发光光谱发生猝灭现象。另外,共掺杂样品在室温条件下存在明显的铁磁性,饱和磁化强度随着掺杂量的增加而增强。     

Synthesis and characterization of binary and ternary III–V quantum dots

Quantum dots of InP, GaP, GaInP₂, and GaAs with diameters ranging from 20–80 Å can be synthesized as well-crystallized nanoparticles with bulk zinc blende structure. The synthesis is achieved by heating appropriate organometallic precursors with stabilizers in high boiling solvents for several days to produce QDs, which can then be dissolved in nonpolar organic solvents to form transparent colloidal QD dispersions. The high sample quality of the InP and Gap QDs results in excitonic features in the absorption spectra; excitonic features could not be observed for GaAs or GaInP₂ QDs. The GaP and GaInP₂ QD colloids exhibit very intense (quantum yields of 15–25%) visible photoluminescence at room temperature. The photoluminescence for InP QDs preparations show two emission bands: one band is in the visible at the band edge of the QD, and a second band appears above 800 nm. The near-IR PL is attributed to deep traps, presumably phosphorus vacancies on the QD surface. This band can be removed after controlled addition of etchant; subsequently, very intense band-edge emission (quantum yield 30%), which is tunable with particle size, is obtained. The QDs were characterized by TEM, SAXS, AFM, powder X-ray diffraction, steady-state optical absorption and photoluminescence spectroscopy, ps to ns transient photoluminescence spectroscopy, and fs to ps pump-probe absorption (i.e., hole-burning) spectroscopy.     

Ba2SiO4:Ce3+,Mn2+荧光粉的制备与光谱性质

用高温固相反应法合成了Ba₂SiO₄:xCe³⁺,yMn²⁺(x=0~0.2, y=0~0.15)荧光粉,研究了荧光粉的晶体结构和发光性质。在紫外光激发下,Ba₂SiO₄:xCe³⁺的发射光谱为位于384 nm附近的宽带。Ba₂SiO₄:Mn²⁺样品的发射光谱位于376 nm的宽带较强,红光发射极弱。在Ce³⁺和Mn²⁺共掺的Ba₂SiO₄:xCe³⁺,yMn²⁺样品中,位于606 nm附近的红光发射较强,来源于Mn²⁺的⁴T₁(⁴G)-⁶A₁(⁶S)跃迁。这说明Ce³⁺离子将部分能量传递给了Mn²⁺离子,有效地敏化了Mn²⁺离子的发光。当Ce³⁺的摩尔分数为0.2、Mn²⁺的摩尔分数为0.075时,Ba₂SiO₄:xCe³⁺,yMn²⁺荧光粉位于606 nm的Mn²⁺的发射峰最强。     

表面等离激元对氮化硅薄膜中Tb3+离子荧光寿命的影响

利用等离子增强化学气相沉积和离子注入方法,制备了铽掺杂的氮化硅薄膜,然后利用磁控溅射和热处理工艺在薄膜上沉积了不同颗粒尺寸的银薄膜来研究表面等离激元共振对铽离子荧光寿命的影响.实验结果表明氮化硅中Tb³⁺离子的光致荧光最强峰在547 nm,而银薄膜的存在会明显降低稀土离子Tb³⁺的荧光寿命,其寿命的改变是由于银薄膜的表面等离激元改变了电磁场的分布,从而影响了系统的局域光模密度(PMD),理论计算的结果也验证了这一点.     

Controllable preparation and disorder-dependent photoluminescence of morphologically different C60 microcrystals

Different C₆₀ crystals were synthesized by precipitation from a mixture of the good solvent m-xylene and the poor solvent isopropyl alcohol. The samples were characterized by scanning electron microscopy (SEM), Raman spectroscopy, thermogravimetric analysis, and high resolution transmission electron microscope (HRTEM). We found that the morphologies and sizes of the samples could be controlled by adjusting the volume ratio between the good and poor solvents. Especially, an unexpected short flower column-like crystal was synthesized at low ratios (from 1:6 to 1:12). Room temperature photoluminescence (PL) and HRTEM studies of the C₆₀ crystal samples reveal that the PL efficiency of the crystals decreases with increasing crystalline order and that the disordered C₆₀ crystals synthesized at the ratio of 1:2 show 10 times higher PL efficiency than that of pristine C₆₀. The mechanism of the growth process of these C₆₀ crystals was also studied by replacing the good solvents m-xylene with toluene and mesitylene.     

Optical properties of nanostructures in layered metal tri-iodide crystals

The optical response of excitons confined in characteristic nanostructures in layered metal tri-iodide crystals introduced by some irregular stackings from the bulk structures is reviewed. In BiI₃ a specific stacking fault takes place during crystal growth constructing macroscopic planar defects. In this space conspicuous localized exciton transitions occur below the intrinsic absorption edge. Another stacking disorder introduced by applying external stress in this crystal brings about a new nanostructure domain of symmetry D_3d different from that of bulk symmetry C²_3i. The optical transitions due to new structures appear in the lower energy region as an absorption and luminescence line series. The similar nanostructures are induced in SbI₃ crystals under the hydrostatic pressure. In these nanostructures, the electronic structure is analyzed by a model based on the confined excitons in a nanoscale disk-like shape space. The magnetic field effect confirms the structure in the wave function-size scale. The nanoscale disk-like structure of BiI₃ in CdI₂ matrices is also obtained by a hot wall technique and mixed crystal annealing, which is realized by observing the size distribution with an electron microscope. In a BiI₃ disk in CdI₂ Stokes shifted photoluminescence bands appear. The Stokes shifts of the luminescence bands are understood by considering the size-dependent exciton-phonon interaction. In these nanostructures large optical nonlinearity under the intense laser field was obtained.     

金属离子修饰的ZnS/PAMAM纳米复合材料的荧光性能研究

用荧光分光光度法研究了Zn2+,Mn2+,Cd2+,Na+,K+,Ag+,Cu2+和Pb2+等金属离子修饰的ZnS/PAMAM树形分子纳米复合材料的荧光发射性能。结果表明：不同金属离子修饰效果不同。Zn2+,Mn2+和Cd2+修饰后,ZnS/PAMAM树形分子纳米复合材料的荧光发射强度有不同程度提高;Ag+,Cu2+和Pb2+的修饰对荧光有不同程度的猝灭作用;而Na+和K+的修饰对荧光发射无明显影响。与修饰前相比,Cd2+离子修饰的ZnS/PAMAM树形分子纳米复合材料标记的潜指纹发射的蓝色荧光更加明亮,与背景反差更加明显。这对提高潜指纹的显现精度和准确率有很好的借鉴价值。     

热退火对SiO2：Er薄膜发光特性的影响

利用离子注入法制备SiO₂:Er样品,并在不同温度下进行退火处理。通过微区拉曼光谱、吸收光谱、X射线光电子能谱等手段对其进行结构表征,并进行了室温和变温的光致发光特性研究,得到了可见区和红外区的光致发光。其中,⁴S_3/2→⁴I_15/2的发光强度随温度的升高,先增强后减弱,呈现出反常的温度淬灭效应,此现象是由Er³⁺与SiO₂的缺陷之间的能量传递造成的。     

Synthesis and characterization of ZnO nanoparticles using polyethylene glycol (PEG)

ZnO nanoparticles and ZnO encapsulated with polyethylene glycol (PEG) was synthesized using zinc acetate as a precursor at low temperature and characterized by different techniques. The influence of the types of solvent, synthesis parameters, and PEG encapsulation on the crystallization, the surface morphology, and the luminescent properties of ZnO nanoparticles prepared by the sol–gel process were investigated. The influence of different addition molar masses of the PEG during the synthesis on the ZnO emission peaks was systematically monitored. The crystallinity, the surface morphology, and the photoluminescence (PL) properties of ZnO depended highly on the synthesis process and PEG encapsulation. X-ray diffraction (XRD) spectra of ZnO nanoparticles show that all the peaks corresponding to the various planes of wurtzite ZnO indicate the formation of a single phase. The absorption edges of these ZnO nanoparticles are shifted by additions of the PEG polymer. The photoluminescence (PL) characterization of the ZnO nanostructures exhibited a broad emission in the visible range with maximum peak at 450 and/or 560 nm.