Composite semiconductor quantum dots CdSe/CdS Co-sensitized TiO2 nanorod array solar cells

CdSe/CdS semiconductor quantum dots co-sensitized TiO2 nanorod array was fabricated on the transparent conductive fluorine-doped tin oxide (FTO) substrate using the hydrothermal and successive ionic layer adsorption and reaction (SILAR) process. The structural and morphological properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results indicate that CdSe/CdS QDs are uniformly coated on the surface of the TiO2 nanorods. The shift of light absorption edge was monitored by taking UV-visible absorption spectra. Compared with the absorption spectra of the TiO2 nanorod array, deposition of CdSe/CdS QDs shifts the absorption edge to the higher wavelength. The enhanced light absorption in the visible-light region of CdSe/CdS/TiO2 nanorod array indicates that CdSe/CdS layers can act as co-sensitizers in quantum dots sensitized solar cells (QDSSCs). By optimizing the CdSe layer deposition cycles, a photocurrent of 5.78 mA/cm2, an open circuit photovoltage of 0.469 V and a conversion efficiency of 1.34 % were obtained under an illumination of 100 mw/cm2.     

Optical Characteristics of InAs Quantum Dots on GaAs Matrix by Using Various InGaAs Structures

The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots（ QDs ） grown by molecular-beam epitaxy （MBE） were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGaAs / GaAs quantum well. The temperature-dependent and time-resolved photoluminescence （ TDPL and TRPL ） were used to study the dynomic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL inteasity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.     

N-油酰基吗啡啉体系中CdZnS三元量子点的合成——光谱性质及生长机理

以N-油酰基吗啡啉为溶剂,硬脂酸镉、硬脂酸锌和S粉为原料,采用高温热注射法合成了高质量的CdZnS量子点,用紫外-可见吸收光谱（UV-vis）,荧光发射光谱（PL）,高分辨透射电镜（HRTEM）和X射线粉末衍射仪（XRD）对量子点光谱性质、形貌、单分散性及物相结构进行了分析．结果表明,合成的CdZnS量子点为内富Cd外富Zn的组分梯度结构,改变原料中n（Zn）：n（Cd）或n（Zn＋Cd）：n（S）比可在较大波长范围内调节其吸收光谱,往反应体系中添加不同长链基团可实现更宽范围的光谱调节．     

CdS quantum dots-sensitized TiO2 nanotube arrays for solar cells

CdS quantum dots(QDs) sensitized TiO2 nanotube arrays photoelectrodes were investigated for their photovoltaic performance of quantum dots-sensitized solar cells. The highly ordered TiO2 nanotube arrays(TNAs) were synthesized on Ti foils by anodic oxidation method. Then CdS quantum dots were deposited onto the TiO2 nanotube arrays by successive ionic layer absorption and reaction(SILAR) method to serve as the sensitizers. Cd(NO3)2 and Na2S were used as the precursor materials of Cd+ and S2- ions, respectively. It is found that the CdS QDs sensitizer may significantly increase the light response of TiO2 nanotube arrays. With increasing CdS QDs deposition cycles, the visible light response increases. Maximum photocurrent was obtained for the QDs that have an absorption peak at about 500 nm. Under AM 1.5 G illuminations(100 mW cm-2), a 4.85 mA/cm2 short circuit current density was achieved, and the maximium energy conversion efficiency of the as-prepared CdS QDs-sensitized TNAs solar cells was obtained as high as 0.81 % at five SILAR cycles.     

Mn掺杂CdS量子点的微波水相合成

利用微波辐射促进离子扩散的方法,大大降低Mn2+扩散所需温度,在水相中成功制备出CdS Mn量子点.该量子点具有立方闪锌矿结构,荧光发射峰波长可以在530～660 nm之间连续调节,荧光量子产率高达50%,并且具有良好的光稳定性.这种方法可以为其他掺杂量子点的水相合成提供参考.     

Direct synthesis of Zn1−x Cd x S (0⩽x⩽1) quantum dots in aqueous solution and application in biology

A simple procedure was presented to directly synthesize Zn1-xCdxS (0≤x≤1) quantum dots (QDs) in aqueous solution. QDs’ structures and properties were characterized by TEM (transmission electron microscopy), XRD (X-ray diffraction) and fluorescence microscopy. For those as-synthesized Zn1-xCdxS QDs, when the molar ratio between Zn and Cd changed from 1 to 0, its photoluminescence (PL) emission peak shifted from 430 nm to 675 nm. PL emission quantum efficiency was up to 15%. The experiment results demonstrated that those alloyed QDs showed a good biocompatibility and could be used as labelling materials in cell biology.     

水热法合成水溶性CdTe量子点及其光谱表征

用半胱胺作为稳定剂,采用水热法快速合成了水溶性的CdTe量子点。荧光光谱表明所合成的量子点具有优异的发光性质,所得到的量子点尺寸分布均匀、半峰宽较窄。透射电子显微镜(TEM)表征了量子点的结构和粒径分布。通过荧光发射光谱研究了前驱体溶液中铬离子的浓度和配体浓度对量子点晶体生长速度的影响,前驱体溶液中铬离子浓度增加或稳定剂半胱胺的浓度减小,纳米晶体的生长速度加快。通过荧光发射光谱的研究,确定了合成前驱体溶液的最佳pH值为5.6。实验中还研究了不同pH值的磷酸盐缓冲溶液对CdTe量子点荧光强度的影响。     

脂质体包裹的CdTe复合量子点的合成

应用脂质体包裹技术合成了具有生物相容性的CdTe复合荧光量子点，通过透射电子显微镜和荧光谱图证实脂质体包裹复合量子点是成功的．用荧光分光光度计表征了脂质体包裹后的复合量子点，基本上保持了量子点的荧光特性；同时检测到随着脂质体包裹的量子点浓度的由低到高变化，荧光强度先升高后降低。     

Synthesis and luminescence properties of red phosphor CaO: Eu3+

Ca(NO₃)₂·4H₂O, Eu(NO₃)₃ and H₂C₂O₄·2H₂O were adopted to synthesize CaO: Eu³⁺ with the chemical co-precipitation method, and the effects of the calcination temperature and Eu³⁺ doping concentration on the phosphor structure and its luminescent properties were investigated by TG-SDTA, XRD, and PL-PLE. The results confirm that the Eu³⁺ ions as luminescent centers substitutes Ca²⁺ sites without changing the crystal structure of cubic CaO. The optimum calcination temperature and the optimum concentration of Eu³⁺ are 1 100 ° and 1 mol%, respectively, under which the best crystallinity and highest PL intensity appeared. The maximum emission wavelength is 592 nm (⁵D₀→⁷F₁) which is excited by xenon lamp with the wavelength of 200–280 nm, indicating that the Eu³⁺ ion mainly locates in the symmetric position (O_h) in the crystal lattice of CaO. Funded by the Science and Technology Bureau of Sichun Province(No. 2006J13-059) and Education Bureau of Sichun Province (No. 2006A094)     

聚丙烯薄膜的光致发光

用紫外-可见分光光度计和光致发光测量装置测量了聚丙烯薄膜在氙灯辐照下的光致发光强度、发光光谱和吸收光谱,研究了聚丙烯薄膜的光致发光性能.结果表明:聚丙烯薄膜的光致发光强度随测量时间呈指数衰减,发光光谱在323.8 nm、395.6 nm、514.2 nm、561.8 nm、609.4 nm、680.7 nm和752.2 nm附近存在峰带,其中752.2 nm附近的峰带相对较强.辐照时间增加,发光峰强减弱,发光强度衰减变快,发光峰带向长波方向移动.吸收度随辐照时间的增长呈增色效应,吸收带的最大吸收波长发生红移,由吸收边算得其光能隙约为4.21 eV.     

Preparation of diphenylcarbazide-directed CdSe quantum dots and selective determination for Cr(VI)

CdSe quantum dots (QDs) were synthesized using diphenylcarbazide (DL) to sequester QDs precursors (Cd²⁺) in situ. Fluorescence (FL) analysis showed the successive synthesis of QDs could be realized by capping with DL and the binding between DL and Cd²⁺. The average QDs particle size was about 5-20 nm by high-resolution transmission electron microscopy (HRTEM). Fourier transform infrared (FT-IR) spectra showed that CdSe QDs could be chemically bonded with DL. The formation of QDs-DL-Cr(VI) could lower the fluorescence intensity of QDs. In a certain concentration range, the fluorescence intensity and Cr(VI) concentration presented a linear relationship. As a result, this phenomenon could be used to determine the Cr(VI) concentration in the range of 0-24 ×10^?6 mol· L^?1.     

聚酰亚胺薄膜的光致发光研究

用光致发光测量装置和紫外—可见分光光度计测量了聚酰亚胺薄膜的发光强度、发光光谱和吸收光谱,研究了聚酰亚胺的光致发光性能.结果表明：聚酰亚胺的光致发光强度随测量时间呈指数衰减规律,发光光谱由荧光区、磷光区和红光及红外三个区域组成,其中700 nm附近的峰带相对较强.辐照时间增加,发光强度衰减减慢,发光峰带向长波方向移动.吸收带的最大吸收波长发生红移,由吸收边算得其光能隙约为2.76 eV.     

基于TDLAS-WMS的高灵敏度电子鼻传感器设计

为了对痕量有害气体(甲烷为例)进行非接触式检测,本文基于可调谐二极管激光吸收光谱(TDLAS)与波长调制光谱(WMS)相结合的检测技术,采用中心波长为7.5μm的量子级联激光器(QCL),设计并研制出高灵敏度电子鼻传感器系统.在室温条件下,通过调节QCL注入电流,使其发光光谱扫过甲烷(CH4)气体吸收谱线.同时采用紧凑型herriott气室(长度为40 cm,容积为800 m L),使得系统总光程达到16 m.利用该传感器系统,对不同浓度的CH4进行测量,结果显示,测量相对误差小于7%,检测下限为1×10~(-9).同时,研究人员可以通过更换其他激射波长的QCL,实现对其它有害气体的检测.     

CdS:Co掺杂量子点的合成与表征

通过微波辐射技术,过度金属钴离子可以成功地掺杂到CdS量子点内部.由于钴离子占据了量子点的中心位置,随着辐射时间的增加,钴离子逐渐向外渗透扩散,伴随此过程,掺杂后的量子点的紫外吸收峰和荧光发射峰都相应地发生了红移.通过X射线衍射和高分辨投射电镜表征发现,掺杂后的晶体依然为立体闪锌矿结构,并且具有量子点的晶体特征;经过紫外吸收和荧光光谱表征发现,与CdS量子点相比,除了荧光光谱的发射峰范围扩宽了50 nm,荧光稳定性和化学稳定性得到了很大的提高.     

通讯波段低密度InAs量子点的研究

1.3和1.5μm波长低密度自组织双层量子点被期望首先用在在单个光子光纤传输中,这种结构是基于由一薄层GaAs隔离的双层InAs量子点实现的,由于应变场的存在,第一层量子点为第二层量子点提供了一个成核区,低温生长的双层InAs量子点发光主要来自于顶层量子点,顶层量子点发光波长会向长波长移动。在本论文中,利用低密度InAs量子点作为获得长波长双层InAs的种子层,实验制备的双层InAs量子点,波长约为1.4μm。     

Citrate-stabilized CdSe/CdS quantum dots as fluorescence probe for protein determination

A rapid, ultrasensitive and convenient fluorescence measurement technology based on the enhancement of the fluorescence intensity resulting from the interaction of functionalized CdSe/CdS quantum dots (QDs) with bovine serum albumin (BSA) was proposed. The citrate-stabilized CdSe/CdS (QDs) were synthesized by using Se powder and Na₂S as precursors instead of any pyrophoric organometallic precursors. The modified CdSe/CdS QDs are brighter and more stable against photobleaching in comparison with organic fluorophores. At pH 7.0, the fluorescence signal of CdSe/CdS is enhanced by increasing the concentration of BSA in the range of 0.1–10 μg/mL, and the low detection limit is 0.06 μg/mL. A linear relationship between the enhanced fluorescence peak intensity (ΔF) and BSA concentration (c) is established using equation ΔF=50.7c+16.4 (R=0.996 36). Results of determination for BSA in three synthetic samples are identical with the true values, and the recovery (98.9%–102.4%) and relative standard deviation (RSD, 1.8%–2.5%) are satisfactory.     

Cu掺杂对ZnO量子点光致发光的影响

通过溶液法合成了Cu掺杂ZnO量子点。X射线衍射(XRD)和高分辨电子透射电镜(HRTEM)图像显示Cu掺杂ZnO量子点具有六角纤锌矿结构,晶粒大小为4～5nm。Cu掺杂抑制了ZnO量子点颗粒长大。室温光致发光(PL)谱观察到紫外带边和可见区两个发射峰。随着Cu掺杂浓度的增大,紫外荧光峰位发生缓慢红移,由366nm移到370nm;可见区发射峰位发生蓝移,由525nm移到495nm;同时,两个发射峰强度降低。光谱结果表明:Cu的掺入,一方面抑制表面与O空位有关的缺陷,在495nm出现了与Cu1+有关的发射峰;另一方面,Cu离子掺入ZnO量子点引入一些非辐射中心,降低了自由激子发射。     

一种烯基封端的稠环噻吩合成及光电性质研究

稠环噻吩是有机光电功能小分子中非常重要的结构单元,以十七烷基侧链取代的稠环噻吩为中心结构,通过过渡金属催化的Stille交叉偶联反应引入苯乙烯封端基团,简单高效地合成了一种新的带有烯基封端基团的侧链十七烷基取代的四并噻吩分子.利用核磁共振氢谱对产物结构进行表征,同时采用热重分析、紫外-可见光吸收光谱、荧光发射光谱及电化...     

Lower temperature synthesis of cerium-doped polycrystalline lutetium pyrosilicate powders by a novel sol-gel processing

A novel sol-gel processing was developed to synthesize polycrystalline cerium-doped lutetium pyrosilicate(Lu2Si2O7:Ce,LPS:Ce)powders under low temperature.It was found that the addition of propylene oxide(PPO)could promote the formation of Lu-O-Si bonds in precursor,which was beneficial to the formation of LPS phase.X-ray diffraction(XRD)patterns indicated that the single-phased LPS powder was well crystallized at 1050°C.Microstructure observation demonstrated that the synthetic LPS powder was composed of ellipsoidal grains with the mean size of 40 nm.The luminescent properties were characterized by photoluminescence(PL),X-ray excited luminescence(XEL)and vacuum ultraviolet(VUV)spectroscopy at room temperature.The synthetic LPS:Ce powder emitted a broad emission spectrum centered at about 380 nm,which should be ascribed to the 5d→4f transition of Ce3+.Decay time of the synthetic LPS:Ce powder was measured to be only 32 ns.     

Plasma-enhanced Chemical Vapordeposition SiO2 Film after Ion Implantation Induces Quantum Well Intermixing

A method of QWI ( quantum well intermixing) realizing through plasma-enhanced chemical vapordepositiom (PECVD) SiO2 film following ion implantation was investigated. PECVD 200 nm SiO2 film after 160 keV phosphorus(P) ion implantation was performed to induce InP-based multiple-quantum-well (MQW) laser structural intermixing, annealing process was carried out at 780 ℃ for 30 seconds under N2 flue, the blue shift ofphotoluminescence (PL) peak related to implanted dose: 1 × 1011 , 1 × 1012, 1 × 1013 ,3 × 1013 , 7 × 1013 ion/ cm2 is 22 nm, 65 nm, 104 nm, 109 nm, 101 nm, respectively. Under the same conditions, by comparing the blue shift of PL peak with P ion implantation only, slight differentiation between the two methods was observed, and results reveal that the defects in the implanting layers generated by ion implantation are much more than those in SiO2 film. So, the blue shift results mainly from ion implantation. However , SiO2 film also may promote the quantum well intermixing.