CdSe与CdSe/ZnS量子点合成及稀土掺杂

在LSS(liquid-solid-solution)多相体系中制得了CdSe、CdSe/ZnS量子点和Eu掺杂的量子点。利用TEM、XRD、PL、EDS对产物进行了表征。TEM结果显示所得的量子点形貌规则、尺寸均匀。XRD结果显示CdSe/ZnS量子点呈六方晶系。PL结果对比表明,合适厚度壳层ZnS包覆后的CdSe量子点发光效率明显提高,发光峰的半高宽有大幅度提高,并分析了所得的结果。掺杂稀土元素Eu后,CdSe(Eu)量子点在红光区域产生了新的发光峰;而CdSe(Eu)/ZnS量子点在红光区域内没有出现发光峰,并阐明了这种现象的原因。     

水相制备CdSe量子点及其ZnS核壳结构量子点

因具有较宽的可调控发光范围,CdSe量子点及其ZnS核壳结构量子点受到了研究者们的普遍关注。采用水相回流法合成了CdSe量子点及其ZnS核壳结构量子点,并结合透射电镜(TEM)、X射线衍射(XRD)、紫外-可见光吸收光谱(UV-Vis)和荧光光谱(PL)对样品进行表征。TEM结果表明,合成的量子点粒径分布较宽且结晶度较高;从XRD分析结果可以看出,CdSe量子点为闪锌矿结构,沿着晶面向外生长ZnS壳层后,谱峰向高角度偏移;从UV-Vis和PL分析结果可以看出,CdSe量子点于500 nm处出现吸收肩峰,于644 nm处出现半高宽较宽的缺陷发光峰;随着反应时间的延长,于577 nm处出现本征发光峰。包覆了ZnS壳层后,量子点不仅发光强度明显增大,而且稳定性显著提高。该合成方法节能环保、生产效率高,具有较大的应用空间。     

胶体量子点多色LED的设计、制备和表征

量子点LED采用胶体量子点为LED发光层,通过调节量子点的尺寸可以制作出覆盖可见以及近红外光谱的量子点LED(QD-LED),而且量子点LED器件发出的光谱范围很窄(光谱半高宽可达30 nm).为了研究不同发光颜色的QD-LED器件特性,本文采用具有523 nm和608 nm发光波长的CdSe/ZnS核壳型量子点为发光层、poly-TPD为空穴传输层、ZnO为电子传输层,制备了量子点红光和绿光LED并讨论了器件的相关特性.这些结果对量子点LED在飞机驾驶舱以及医疗器械照明方面的应用提供了参考,但要满足商业化的需求其寿命、亮度以及效率还需要进一步的提高.     

ZnS:Mn沉积温度对薄膜电致发光器件亮度的影响

采用丝网印刷技术,在Al2O3陶瓷基板上印刷、高温烧结内电极及绝缘层,制备出陶瓷厚膜基板,进而制备了新型厚膜电致发光显示器(TDEL).整个器件结构为陶瓷基板/内电极/厚膜绝缘层/发光层/薄膜绝缘层/ITO透明电极.研究不同基板沉积温度对发光层性能的影响,并对器件的亮度-电压、亮度-频率进行测量.结果显示较高的ZnS:Mn沉积温度明显提高了无机发光器件的发光亮度.其原因主要是由于高的沉积温度提高了ZnS:Mn的成膜质量,提高膜层微晶尺寸大小,从而发光亮度提高.但是我们发现温度继续提高的同时,器件发光亮度趋于饱和,分析原因是由于掺杂Mn浓度过高,影响了发光效果.     

Ⅱ-Ⅵ族量子点掺杂玻璃的光学性质及研究进展

由于量子限域效应,尺寸可调的Ⅱ-Ⅵ族量子点掺杂玻璃在光学滤波片、非线性光学器件上的应用已经被广泛研究。玻璃中量子点的光学性质主要由量子点的尺寸、表面状态和周围基质环境决定,通过提高Se/Cd比可以有效地对量子点的表面缺陷进行钝化,实现CdSe量子点的本征发光;进一步调整热处理制度可以促进Zn离子扩散进入CdSe量子点表面,形成CdSe/Cd_(1-x)Zn_xSe核壳结构,使得缺陷发光几乎完全猝灭,从而提高量子点的荧光量子效率;在玻璃中原位合成的CdS/ZnS核壳结构量子点的荧光量子效率可达到53%。随着基础研究中玻璃中Ⅱ-Ⅵ族量子点荧光效率的不断提高,发光二极管(LED)等小型发光器件的制造成为可能。为了满足实际需要,建立核壳结构中量子点表面钝化机理模型,进一步优化量子点荧光效率是下一步需要解决的问题。     

聚合物-CdSe/ZnS量子点复合薄膜的制备及其荧光性能研究

以两性齐聚物(聚马来酸十六醇酯,PMAH)为修饰剂,利用相转移的方法将油溶性的CdSe/ZnS量子点转移至水中,制备出高量子产率、高稳定性的水溶性CdSe/ZnS荧光量子点.随后将PMAH修饰的水溶性量子点分散到聚丙烯酸(PAA)乳液中,采用旋转涂膜的方法制备了透明的聚合物-CdSe/ZnS量子点复合薄膜,在紫外灯的照射下薄膜发出明亮的红色光.利用XPS对复合薄膜的表面结构进行了表征.随后对膜的光致发光性能和薄膜在黑暗的环境中对紫外光的耐受性进行了系统的研究,发现复合薄膜的荧光强度随着薄膜厚度和薄膜中纳米晶浓度的增加而线性增强,薄膜在紫外光照射800h后仍然保持了很高的荧光强度,量子产率仅仅损失了5%。     

C镶嵌SiO2薄膜电致发光谱的数值分析

采用磁控溅射法制备了含纳米碳粒的氧化硅薄膜,在室温下测量了Au/镶嵌纳米碳粒氧化硅膜/p-Si结构的电致发光谱,电致发光谱显示,随着正向偏压的增加,来自该结构的电致发光峰位于650nm处几乎不移动,发光强度增大.利用位形坐标模型对C镶嵌SiO2薄膜的电致发光谱进行了分析,结果表明该结构的电致发光谱存在1.8和2.0eV左右的两个发光中心,分别来自SiO2层的非桥氧空位和纳米C团簇.     

稀土离子注入的硅材料MOS结构高效率电致发光器件

本文介绍了在稀土离子Re(Re=Er、Eu、Tb、Ce和Gd)注入的SiO2金属-氧化物-硅(MOS)结构高效率电致发光器件的研究进展情况。通过将不同的稀土离子注入到SiO2薄膜,相继获得了发射光谱峰值分别位于红外(1.54μm)、可见光(618 nm5、43 nm、440 nm)至紫外(316 nm)光谱范围的MOS结构电致发光器件,并系统研究了SiO2:Re薄膜中稀土离子的电致发光特性。在SiO2:Re有效发光层的厚度为50 nm,掺杂浓度为1-3%的条件下,稀土Er、Tb和Gd离子注入掺杂的硅材料MOS结构电致发光器件在红外、绿光和紫外的量子效率分别达到14%、16%和5%,接近了商品化III-V族半导体发光二极管的水平。     

CuInS_2/ZnS/ZnS量子点的制备与光电性能研究

首先以高温一锅煮法合成了CuInS_2核量子点,再通过连续和长时间的包覆ZnS外壳,制备出了量子产率高达76%的厚壳结构CuInS_2/ZnS/ZnS,将CuInS_2/ZnS/ZnS量子点作为发光层,利用简单的溶液处理法工艺成功制备出CuInS_2基量子点发光二极管(QLEDs)。同时对量子点的结构、形貌和光学性能及CuInS_2基QLEDs的光电性能进行表征和分析,研究结果表明,通过延长高温反应时间在CuInS_2核上包覆ZnS外壳,能够合成具有良好的光致发光性能的CuInS_2/ZnS/ZnS量子点,利用溶液法制备的CuInS_2基QLEDs开启电压值仅为2.5 V,并且其发光亮度能够达到5473 cd/m~2。CuInS_2/ZnS/ZnS的光致发光和电致发光性能都有了很大的提升。     

Au/锗/氧化硅纳米多层膜/p-Si结构的电致发光机制研究

用射频磁控溅射法制备了锗/氧化硅纳米多层膜,在室温下测量了Au/锗/氧化硅纳米多层膜/pSi结构的电致发光.利用位形坐标模型分析了锗/氧化硅纳米多层膜的发光中心,并用量子限制-发光中心模型对该纳米结构的电致发光过程作了研究,研究表明锗/氧化硅纳米多层膜的电致发光主要来自SiO2层的发光中心.     

Organic light-emitting devices fabricated utilizing core/shell CdSe/ZnS quantum dots embedded in a polyvinylcarbazole

Electrical and the optical properties of organic light-emitting devices (OLEDs) fabricated utilizing core/shell CdSe/ZnS quantum dots (QDs) embedded in a polyvinylcarbazole (PVK) layer were investigated. An abrupt increase of the current density above an applied voltage of 12 V for OLEDs consisting of Al/LiF/4,7-diphenyl-1,10-phenanthroline/bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato) aluminium/[CdSe/ZnS QDs embedded in PVK]/poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonate)/ITO/glass substrate was attributed to the existence of the QDs. Photoluminescence spectra showed that the peaks at 390 and 636 nm corresponding to the PVK layer and the CdSe/ZnS QDs were observed. While the electroluminescence (EL) peak of the OLEDs at low voltage range was related to the PVK layer, the EL peak of the OLEDs above 12 V was dominantly attributed to the CdSe/ZnS QDs. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates of the OLEDs at high voltages were (0.581, 0.380) indicative of a red color. When the holes existing in the PVK layer above 12 V were tunneled into the CdSe/ZnS QDs, the holes occupied by the CdSe/ZnS QDs combined with the electrons in the PVK layer to emit a red color related to the CdSe/ZnS QDs.     

Radiative interface state study in CdSe/ZnS quantum dots covered by polymer

The paper presents the transformation of photoluminescence (PL) spectra of nonconjugated and bioconjugated core/shell CdSe/ZnS QDs covered by PEG polymer at the aging in ambient air. Studied QDs are characterized by the sizes: (i) 3.6-4.0 nm and color emission with the maxima at 560-565 nm (2.19-2.25 eV) and (ii) 5.2-5.3 nm and with emission at 605-610 nm (2.02-2.08 eV). The part of 565 nm CdSe/ZnS QDs has been bioconjugated to the mouse anti PSA (Prostate-Specific Antigen) antibodies and the part of 605 nm QDs has been bioconjugated to the antihuman IL10 (Interleukin 10) antibodies using the commercially available 565 nm and 605 nm QD conjugation kits. It is revealed that the aging process in ambient air has the very strong impact on PL spectra of nonconjugated core/shell CdSe/ZnS QDs covered with PEG polymer. The aging process relates to the polymer modification in ambient air that is accompanied by the three effects: (i) polymer transparency increasing for the emission of CdSe cores (2.03 or 2.20 eV), (ii) the intensity stimulation of high energy PL bands (2.37, 2.73 and 3.06 eV) related to the interface states at the ZnS/PEG polymer interface and (iii) the elastic strain modification in QD systems. The concentration of interface states at the ZnS/polymer interface increases at the aging of PEG polymer in ambient air.     

Synergistic effects of SPR and FRET on the photoluminescence of ZnO nanorod heterostructures

Solution-grown ZnO nanorods (NRs) were successfully conjugated with CdSe/ZnS quantum dots (QDs) and Ag nanoparticles (NPs) to suppress intrinsic defect emission and to enhance band-edge emission at the same time. First, high-density and high-crystallinity ZnO NRs of diameter 80–90 nm and length 1.2–1.5 μm were grown on glass substrates using a low-temperature seed-assisted solution method. The as-synthesized ZnO NRs showed sharp photoluminescence (PL) band-edge emission centered at ～377 nm together with broad defect emission in the range of ～450–800 nm. The ZnO NRs were decorated with CdSe/ZnS QDs and Ag NPs, respectively, by sequential drop-coating. The PL of CdSe/ZnS QD||ZnO NR conjugates showed that ZnO band-edge emission decreased by 73.8% due to fluorescence resonance energy transfer (FRET) and charge separation between ZnO and CdSe/ZnS by type II energy band structure formation. On the other hand, Ag NP||CdSe/ZnS QD||ZnO NR conjugates showed increased band-edge emission (by 25.8%) and suppressed defect emission compared to bare ZnO NRs. A possible energy transfer mechanism to explain the improved PL properties of ZnO NRs was proposed based upon the combined effects of FRET and surface plasmon resonance (SPR).     

CdSe(ZnS) nanocomposite luminescent high temperature sensor

High temperature luminescence-based sensing is demonstrated by embedding colloidal CdSe(ZnS) quantum dots into a high temperature SiO(2) dielectric matrix. The nanocomposite was fabricated by a solution process method. As-prepared CdSe(ZnS) quantum dots in the nanocomposite sensor show an absorption band at a wavelength of 600 nm (2.06 eV). Photoluminescence (PL) measurements show a room temperature emission peak at 606 nm (2.04 eV). The temperature-dependent emission spectra study shows for the first time a CdSe(ZnS)-SiO(2) nanocomposite-based high temperature sensor. The temperature-dependent spectral and intensity modes of the nanocomposite thin film photoluminescence were investigated from 295-525 K. The sensor shows a variation of the emission wavelength as a function of temperature with a sensitivity of ～ 0.11 nm °C( - 1). The film morphology and roughness are characterized using AFM.     

Fabrication of white light-emitting diodes based on UV light-emitting diodes with conjugated polymers-(CdSe/ZnS) quantum dots as hybrid phosphors

White light-emitting diodes (LEDs) were fabricated using GaN-based 380-nm UV LEDs precoated with the composite of blue-emitting polymer (poly[(9,9-dihexylfluorenyl-2,7-diyl)-alt-co-(2-methoxy-5-{2-ethylhexyloxy)-1 ,4-phenylene)]), yellow green-emitting polymer (poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)]), and 605-nm red-emitting quantum dots (QDs). CdSe cores were obtained by solvothermal route using CdO, Se precursors and ZnS shells were synthesized by using diethylzinc, and hexamethyldisilathiane precursors. The optical properties of CdSe/ZnS QDs were characterized by UV-visible and photoluminescence (PL) spectra. The structural data and composition of the QDs were transmission electron microscopy (TEM), and EDX technique. The quantum yield and size of the QDs were 58.7% and about 6.7 nm, respectively. Three-band white light was generated by hybridizing blue (430 nm), green (535 nm), and red (605 nm) emission. The color-rendering index (CRI) of the device was extremely improved by introducing the QDs. The CIE-1931 chromaticity coordinate, color temperature, and CRI of a white LED at 20 mA were (0.379, 0.368), 3969 K, and 90, respectively.     

Single active-layer structured dual-function devices using hybrid polymer-quantum dots

We demonstrate hybrid polymer-quantum dot dual-function devices with a single active-layer structure consisting of CdSe/ZnS semiconductor quantum dots dispersed with poly N-vinylcarbazole (PVK) and 1,3,5-tirs-(N-phenylbenzimidazol-2-yl) benzene (TPBi) fabricated on an indium-tin-oxide (ITO)/glass substrate by using a simple spin-coating technique. The dual-function devices are composed of light-emitting diodes (LED) on the top side and nonvolatile organic bistable memory devices (OBD) on the bottom side and can show electroluminescence (EL) along with electrical bistability concurrently. Both the functionality of LEDs and OBDs can be successfully achieved by adding an electron transport layer (ETL) TPBi to the OBD to attain an LED in which the lowest unoccupied molecular orbital (LUMO) level of TPBi is positioned at the energy level between the conduction band of CdSe/ZnS and the LiF/Al electrode. Through transmission electron microscopy (TEM) study, it is revealed that CdSe/ZnS QDs distributed on the interface of the hole transport layer (HTL) and ETL significantly take part in the electroluminescence process rather than those existing at the outer surface of the ETL.     

Aspects of emission variation in CdSeTe/ZnS quantum dots conjugated to antibodies

CdSeTe/ZnS quantum dots (QDs) with the emission peak at 705 nm have been studied comparatively in the non-conjugated state and after bioconjugation to anti-pseudo rabies virus antibodies (ABs) by means of photoluminescence (PL) and Raman scattering methods. It is revealed that PL spectra of QDs vary significantly after conjugating to ABs. In PL spectra of non-conjugated QDs only one PL band of Gaussian shape peaked at 1.76–1.78 eV and related to exciton emission in the CdSeTe core has been detected. The PL spectra of bio-conjugated QDs demonstrate the high energy spectral shift and asymmetric shape of PL bands. The study of Raman scattering spectra permits to estimate the CdSeTe alloy composition and to detect the surface enhanced Raman scattering (SERS) effect for bioconjugated QDs. The last fact testifies on the interaction of excitation light electromagnetic field with the electric dipoles excited in ABs. The optical band gap in CdSeTe core has been calculated numerically versus core radius on the base of the effective mass approximation model. Then the energy band diagrams for non-conjugated and bio-conjugated states of CdSeTe/ZnS QDs have been designed. It is revealed the type II quantum well in CdSeTe core that explains the optical transition at 705 nm in the wide band gap CdSeTe alloy. The analysis has shown that AB dipoles excited in bio-conjugated QDs stimulate changing the profile of QD energy band diagram that manifests itself in the mentioned PL spectrum transformations. Actually, the study of PL spectrum varying in CdSeTe/ZnS QDs conjugated to specific antibodies can be an informative tool in biology and medicine for early medical diagnostics.     

Temperature-controlled synthesis of CdSe nanocrystals with narrow size distribution

CdSe quantum dots (QDs) with narrow size distribution and fine crystallinity were synthesized in paraffin liquid through temperature-control method. TEM, HRTEM, SEAD, XRD, PL and UV-VIS spectra were used to characterize the size, crystal structure and photoluminescence (PL) properties of CdSe nanocrystals. The PL spectra and TEM results revealed that the monodispersed and uniformed CdSe QDs with narrow size distribution were synthesized at a certain reaction temperature. HRTEM images combined with selected area electron diffraction (SAED) and XRD patterns illustrated that CdSe QDs showed near-perfect zinc-blende and wurtzite crystallinity at different temperatures. The Gibbs-Thomson calculation provided a thermodynamic explanation for obtaining the CdSe nanocrystals with narrow size distribution by temperature-control method.     

沉淀法制备ZnS∶Cr纳米晶及其光学性能研究

以十二烷基苯磺酸钠和六偏磷酸钠作为分散剂,采用沉淀法制备了ZnS及不同掺杂浓度的ZnS∶Cr纳米晶。利用XRD和TEM对纳米晶物相和形貌进行了分析。结果表明,ZnS和ZnS∶Cr纳米晶均为立方闪锌矿结构,利用谢乐公式估算ZnS和ZnS∶Cr纳米晶平均粒径分别为2.1和2.2nm。TEM观察到纳米晶近似为球形,平均粒度为3nm左右,具有较好的单分散性且分布均匀。荧光光谱(PL)表明,纳米晶在420、440和495nm处有发射谱带,前两者被认为是S空位深陷阱发光,后者被认为是表面态或中心辐射复合发光。     

Extracellular biosynthesis of biocompatible CdSe quantum dots

An extracellular biosynthesis method has been developed to prepare cadmium selenide (CdSe) quantum dots (QDs) with strong fluorescence emission by incubating cheap Cd and Se inorganic salts with Escherichia coli (E.coli) bacteria. Ultraviolet–visible absorption spectra, photoluminescence (PL) spectra, and high‐resolution transmission electron microscopy analysis showed that the biosynthesised CdSe QDs have an average size of 3.1 nm, the excellent optical properties with fluorescence emission around 494 nm, and the good crystallinity. It was found that addition of 80 mg of mercaptosuccinic acid resulted in the formation of CdSe QDs with highest PL intensity. Furthermore, Fourier‐transform infrared spectra of as‐synthesised CdSe QDs confirmed the presence of a surface protein capping layer. The biosynthesised CdSe QDs were incorporated into the yeast cells as illustrated by laser confocal scanning microscopy images, showing a great potential in bio‐imaging and bio‐labelling application.Inspec keywords: microorganisms, molecular biophysics, fluorescence, visible spectra, nanofabrication, nanobiotechnology, proteins, cellular biophysics, nanostructured materials, wide band gap semiconductors, cadmium compounds, semiconductor quantum dots, II‐VI semiconductors, transmission electron microscopy, photoluminescence, optical microscopy, ultraviolet spectra, Fourier transform infrared spectra, biological techniques, semiconductor growthOther keywords: biocompatible CdSe quantum dots, extracellular biosynthesis method, cadmium selenide quantum dots, high‐resolution transmission electron microscopy analysis, biosynthesised CdSe QDs, Fourier‐transform infrared spectra, Escherichia coli, ultraviolet‐visible absorption spectra, PL intensity, fluorescence emission, photoluminescence spectra, optical properties, surface protein capping layer, laser confocal scanning microscopy images, bioimaging, biolabelling application, yeast cells, f mercaptosuccinic acid, CdSe