基于表面等离子体共振效应的荧光太阳集光器制备及其性能

金属纳米颗粒的表面等离子体共振效应能够对特定波长入射光的吸收或者散射增强,正因为其独特的光学性质,金属纳米颗粒被尝试应用于荧光太阳集光器.本文利用全无机钙钛矿CsPbBr3量子点、Au纳米颗粒和硫醇-烯聚合物制备荧光太阳集光器.研究发现,掺杂适量Au纳米颗粒可以通过表面等离子体共振效应提高全无机钙钛矿CsPbBr3量子...     

高Al组分AlGaN多量子阱结构材料发光机制探讨

紫外LED的发光功率和效率还远不能令人们满意,波长短于300 nm的深紫外LED的发光效率普遍较低。厘清高Al组分Al Ga N多量子阱结构的发光机制将有利于探索改善深紫外LED的发光效率的新途径、新方法。为此,本文通过金属有机气相外延技术外延生长了表面平整、界面清晰可辨且陡峭的高Al组分AlGa N多量子阱结构材料,并对其进行变温光致发光谱测试,结合数值计算,深入探讨了Al Ga N量子阱的发光机制。研究表明,量子阱中具有很强的局域化效应,其发光和局域激子的跳跃息息相关,而发光的猝灭则与局域激子的解局域以及位错引起的非辐射复合有关。     

Al纳米颗粒表面等离激元对ZnO光致发光增强的研究

基于聚苯乙烯球自组装法,在P型氮化镓(P-GaN)衬底上制备了有序致密的掩模板;采用热蒸发法在该模板上沉积金属Al薄膜,通过甲苯溶液去除聚苯乙烯球,得到了金属Al纳米颗粒阵列;采用原子层沉积法,在Al纳米颗粒阵列表面依次沉积氧化铝(Al_2O_3)和氧化锌(ZnO).通过测试Al纳米颗粒阵列的消光谱以及ZnO薄膜的光致发光谱,研究了Al纳米颗粒表面等离激元与ZnO薄膜激子之间的耦合效应.实验结果表明:引入Al纳米颗粒后,在约380 nm位置附近的ZnO近带边发光峰积分强度增强了1.91倍.对Al纳米颗粒表面等离激元增强ZnO光致发光的机理进行探讨.     

用MEVVA低能离子注入制备表层SiC/Si异质结构及其室温的光致发光特性

利用金属蒸汽真空弧离子源（MEVVA）进行离子束合成,制备了过剂量C^＋离子注入到单晶硅衬底的样品。然后利用热退火,在表层制备了连续8-SiC层,形成表层SiC／Si的异质结构。利用傅里叶变换红外光谱（FTIR）对其成键特征和微结构进行了分析,通过光电子能谱分析（XPS）和原子力显微镜（AFM）分析了样品的成分分布及其表面形貌。最后对其室温下的光致发光特性随热退火的时间和温度的变化进行了研究。结果表明：光致发光谱（PL）表现出430,560nm两个发光峰,分别对应于纳米碳化硅和块状立方碳化硅发光的特征峰。我们认为小颗粒的晶化碳化硅的尺寸及其相对比例对PL发光峰位和强度有较大的影响,用纳米晶粒量子效应（NSUQC）理论和表面态理论对发光现象及其变化规律进行了初步的解释。     

3C-SiC纳米颗粒量子限制效应的实验证据

报道了关于3C—SiC纳米颗粒量子限制效应的实验证据．将电化学腐蚀3C—SiC多晶靶材得到的多孔材料在水溶液中进行超声处理，制备出发光的3C—SiC纳米颗粒溶液．透射电镜实验表明，所得颗粒直径分布在1-6nm范围，光致发光谱实验给出了存在量子限制效应的实验证据．发光范围在440-460nm．SiC纳米颗粒量子限制效应的发现，为该材料在光电子发光器件中的应用提供了重要的实验基础．     

硅量子点的形状及其弯曲表面效应

硅量子点的弯曲表面引起系统的对称性破缺, 致使某些表面键合在能带的带隙中形成局域电子态.计算结果表明:硅量子点的表面曲率不同形成的表面键合结合能和电子态分布明显不同. 例如, Si–O–Si桥键在曲率较大的表面键合能够在带隙中形成局域能级, 而在硅量子点曲率较小的近平台表面上键合不会形成任何局域态, 但此时的键合结合能较低. 用弯曲表面效应(CS)可以解释较小硅量子点的光致荧光光谱的红移现象. CS效应揭示了纳米物理中又一奇妙的特性. 实验证实, CS效应在带隙中形成的局域能级可以激活硅量子点发光. 关键词： 硅量子点 弯曲表面效应 表面键合 局域能级     

紫外发光增强的石墨烯-氧化锌纳米复合物

采用溶剂热法在相同条件下分别制备了纯ZnO和石墨烯-氧化锌纳米复合物,通过SEM、TEM、拉曼和红外光谱等手段,对纳米复合物样品进行了形貌和结构表征。实验结果显示ZnO纳米颗粒成功地分散在少层石墨烯上。通过对比纯ZnO与复合物的形貌和光致发光谱,发现在没有石墨烯时,ZnO能够择优取向生长成六方棱柱,紫外发光峰弱且宽;在有石墨烯时,ZnO聚集成表面不规则的球形颗粒,紫外发光峰强且窄。上述结果表明ZnO形貌的变化和石墨烯的等离子体效应共同影响了ZnO的紫外发光,但石墨烯的表面等离子体效应起主导作用。     

纳米ZnO镶嵌SiO2薄膜的磁控溅射制备和发光性质的研究

采用射频磁控反应溅射方法在SiO衬底上制备了纳米ZnO镶嵌SiO2薄膜.在室温下利用吸收光谱和光致发光光谱研究了样品的光学性质.发现吸收光谱随纳米ZnO尺寸的减小发生了明显的蓝移,表明随着ZnO尺寸的减小,量子尺寸效应增强,导致带隙展宽,吸收峰蓝移.光致发光光谱在387和441 nm附近出现了两个发光带,分析认为紫外发光来源于自由激子的辐射复合,而蓝色发光带来自于氧空位的电子到价带的跃迁,并用时间分辨光谱和发光衰减证实了上述观点.     

金/银纳米颗粒对Eu掺杂薄膜发光特性影响的研究

本文将三种金属纳米颗粒(球形银纳米颗粒、三角形银纳米薄片和三角形金纳米薄片)分别置于Eu(TTFA)3掺杂的Su8薄膜上研究了它们对铕配合物薄膜发光的影响.结果显示,金属纳米颗粒的局域等离子体共振(LSPR)谱对薄膜发光有很好的调控作用.对于LSPR谱分别与铕配合物激发谱和辐射谱重叠较好的球形和三角形两种银颗粒,相比于未放置颗粒时薄膜的发光,放置有颗粒的发光有明显的增强,其中球形银颗粒的样品的发光增强效果更为明显.而对于LSPR谱与铕配合物激发谱和辐射谱都不重叠的三角形片状金颗粒,该颗粒对样品的发光则起到了猝灭作用.     

不同厚度CdSe阱层的表面上自组织CdSe量子点的发光性质

利用变温和变激发功率分别研究了不同厚度CdSe阱层的自组织CdSe量子点的发光。稳态变温光谱表明:低温下CdSe量子阱有很强的发光,高温猝灭,而其表面上的量子点发光可持续到室温,原因归结于量子点的三维量子尺寸限制效应;变激发功率光谱表明:量子点激子发光是典型的自由激子发光,且在功率增加时。宽阱层表面上的CdSe量子点有明显的带填充效应。通过比较不同CdSe阱层厚度的样品的发光,发现其表面上量子点的发光差异较大,这可以归结为阱层厚度不同导致应变弛豫的程度不同,直接决定了所形成量子点的大小与空间分布^[1]。     

Anti-Reflection Characteristics of Si Nanowires for Enhanced Photoluminescence from CdTe/CdS Quantum Dots

CdTe/CdS quantum dots(QDs) are fabricated on Si nanowires(NWs) substrates with and without Au nanoparticles(NPs). The formation of Au NPs on Si NWs can be certified as shown in scanning electron microscopy images. The optical properties of samples are also investigated. It is interesting to find that the photoluminescence(PL) intensity of Cd Te/Cd S QD films on Si nanowire substrates with Au NPs is significantly increased,which can reach 8-fold higher than that of samples on planar Si without Au NPs. The results of finite-difference time-domain simulation indicate that Au NPs induce stronger localization of electric field and then boost the PL intensity of QDs nearby. Furthermore, the time-resolved luminescence decay curve shows the PL lifetime, which is about 5.5 ns at the emission peaks of QD films on planar, increasing from 1.8 ns of QD films on Si NWs to4.7 ns after introducing Au NPs into Si NWs.     

水溶性CdTe/CdS纳米晶表面SiO2壳层的反相胶束法包覆

"提出了一种水相中制备CdTe/CdS核壳结构纳米粒子的方法.用Te粉作为碲源,用Na2S作为硫源,在50 ℃下制备了CdTe/CdS核壳结构纳米粒子. 用紫外可见吸收光谱和荧光光谱分析了CdS壳层对CdTe核的影响. 随CdS壳层厚度的增加,紫外可见吸收光谱和荧光光谱均发生了红移. CdS壳层厚度较薄时,CdTe/CdS纳米晶的荧光强度较CdTe纳米粒子有显著提高;而CdS壳层厚度较厚时,CdTe/CdS纳米晶的荧光强度会逐渐降低. 用反相胶束法在CdTe/CdS核壳结构纳米粒子的表面包被一层SiO2,     

The Synthesis of Magnetic and Fluorescent Bi-functional Silica Composite Nanoparticles via Reverse Microemulsion Method

In this paper, a simple synthesis method of small-size( about 50 nm in diameter), high magnetic and fluorescent bi-functional silica composite nanoparticles were developed, in which water-soluble Fe₃O₄ magnetic nanoparticlels (MNs) and CdTe quantum dots (QDs) were directly incorporated into a silica shell by reverse microemulsion method. The high luminescent QDs can be used as luminescent marker, while the high magnetic MNs allow the manipulation of the bi-functional silica composite nanoparticles by external magnetic field. Poly (dimethyldiallyl ammonium chloride) was used to balance the electrostatic repulsion between CdTe QDs and silica intermediates to enhance the fluorescence intensity of MNs-QDs/SiO₂ composite nanoparticles. The optical property, magnetic property, size characterization of the bi-functional composite nanoparticles were studied by UV-Vis and PL emission spectra, VSM, TEM, SEM. The stabilities toward time, pH and ionic strength and the effect of MNs on the fluorescence properties of bi-functional silica composite nanoparticles were also studied in detail. By modifying the surface of MNs-QDs/SiO₂ composite nanoparticles with amino and methylphosphonate groups, biologically functionalized and monodisperse MNs-QDs/SiO₂composite nanoparticles can be obtained. In this work, bi-functional composite nanoparticles were conjugated with FITC labeled goat anti-rabbit IgG, to generate novel fluorescent-magnetic-biotargeting tri-functional composite nanoparticles, which can be used in a number of biomedical application.     

Gold and Silver Nanomaterial‐Based Optical Sensing Systems

Gold and silver nanomaterials (NMs) such as nanoparticles (NPs) and nanoclusters (NCs) possessing interesting optical properties have become popular sensing materials. With strong surface plasmon resonance (SPR) absorption, extraordinary stability, ease in preparation, conjugation, and biocompatibility, Au NPs are employed to develop sensitive and selective sensing systems for a variety of analytes. However, small sizes of Au and Ag NCs with interesting photoluminescence (PL) properties are used in many PL‐based sensing systems for the detection of important analytes. In addition, many bimetallic AuM NMs possessing strong catalytic activity are used to develop highly sensitive fluorescent sensors. This review article is categorized in four sections based on the NMs used in the sensing systems, including Au NPs, bimetallic AuM NMs, Au NCs, and DNA–Ag NCs. In each section, synthetic strategies and optical properties of the NMs are provided briefly, followed by emphasis on their analytical applications in the detection of small molecules, metal ions, DNA, proteins, and cells. Current challenges and future prospects of these NMs‐based sensing systems will be addressed.     

Electrostatic assembles and optical properties of Au–CdTe QDs and Ag/Au–CdTe QDs

Au–CdTe and Ag/Au–CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.     

Experimental investigation of energy transfer between CdSe/ZnS quantum dots and different-sized gold nanoparticles

Hybrid nanostructures of quantum dots(QDs) and metallic nanostructure are attractive for future use in a variety of optoelectronic devices. For photodetection applications, it is important that the photoluminescence (PL) of QDs is quenched by the metallic nanostructures. Here, the quenching efficiency of CdSe/ZnS core-shell quantum dots (QDs) with different sized gold nanoparticles (NPs) films through energy transfer is investigated by measuring the PL intensity of the hybrid nanostructures. In our research, the gold NPs films are formed by the post-annealing of the deposited Au films on the quartz substrate. We find that the energy transfer from the QDs to the Au NPs strongly depends on the sizes of the Au NPs. For CdSe/ZnS QDs direct contact with the Au NPs films, the largest energy transfer efficiency are detected when the resonance absorption peak of the Au NPs is nearest to the emission peak of the CdSe/ZnS QDs. However, when there is a PMMA spacer between the QDs layer and the Au NPs films, firstly, we find that the energy transfer efficiency is weakened, and the largest energy transfer efficiency is obtained when the resonant absorption peak of the Au NPs is farthest to the emission peak wavelength of CdSe/ZnS QDs. These results will be useful for the potential design of the high efficiency QDs optoelectronic devices.     

硒化镉发光量子点的制备及其在有机发光器件中的应用

硒化镉量子点具有随粒径尺寸改变,而产生发光波长调变的特性,目前已被广泛研究。本研究是由化学溶胶法合成不同粒径尺寸的核壳型CdSe／ZnS硒化镉量子点,其表面包覆十六烷基胺,避免分子团聚现象。在由硒化镉成核温度的控制,成功地制备一系列具有各种尺寸粒径的核壳型硒化镉量子点(2—6nm)。本研究也合成了含有纳米金粒子于核壳型硒化镉量子点,实验结果发现：硒化镉发光效率明显的提高。在有机发光器件的应用方面,将发光波长为505nm核壳型CdSe／ZnS量子点掺入溶有发光波长为570nm铱化合物的氯仿溶液时,其溶液的光致发光光谱表明,原量子点的发光特性消失,只有铱化合物的发光依然存在,且其发光强度呈现明显增强趋势,我们推测此现象源自于量子点到铱化合物能量转移的机制。我们也以含有核壳型硒化镉量子点的铱化合物与PVK混合材料为发光层,成功的制作发光二极管器件,器件的发光效率因核壳型硒化镉的掺杂,明显提高2倍多。     

1-Hexadecylamine as both reducing agent and stabilizer to synthesize Au and Ag nanoparticles and their SERS application

1-Hexadecylamine (HDA)-capped Au and Ag nanoparticles (NPs) have been successfully prepared by a one-pot solution growth method. The HDA is used as both reducing agent and stabilizer in the synthetic process is favorable for investigating the capping mechanism of Au and Ag NPs’ surface. The growth process and characterization of Au and Ag NPs are determined by Ultraviolet–visible (UV–vis) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Experimental results demonstrate that the HDA-capped Au and Ag NPs are highly crystalline and have good optical properties. Furthermore, surface-enhanced Raman scattering (SERS) spectra of 2-thionaphthol are obtained on the Au and Ag NPs modified glass surface, respectively, indicating that the as-synthesized noble metal NPs have potentially high sensitive optical detection application.     

Laser-assisted generation of gold nanoparticles and nanostructures in liquid and their plasmonic luminescence

Nanoparticles (NPs) and surface nanostructures (NS) are produced via laser ablation of a bulk gold target in liquid using second harmonics of 10 ps Nd:YAG laser (532 nm) with repetition rate of 50 kHz. The morphology and plasmon photoluminescence (PL) properties of obtained nanoscale objects are described. Transmission electron microscopy and field emission scanning electron microscopy are used for morphology characterization of NPs and NS, respectively. Plasmon PL of both gold NPs and NS is experimentally studied using the third harmonics of the Nd:YAG picosecond laser (355 nm) as a pump. The wavelength of intensity maximum of PL of Au NPs colloidal solution virtually coincides with the position of Au NPs plasmon absorption peak. Real-time excitation of both plasmon PL and Raman scattering of surrounding liquid by picosecond laser pulses in aqueous colloidal solution is also investigated. The efficient cross section of plasmon PL of Au NPs colloid is evaluated using Raman scattering of water as a comparative parameter. The results are in good agreement with values obtained in previous works. Plasmon PL from self-organized NS on the Au surface produced via laser ablation is observed for the first time. Its spectrum is compared to PL spectra of both aqueous colloidal solutions of NPs and of NPs deposited on a Si wafer. The obtained experimental data are discussed with reference to the band structure of bulk Au.     

Size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots

We investigate size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots (QDs) grown using molecular beam epitaxy and atomic layer epitaxy. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy with increasing ZnTe buffer thicknesses. This shift of the PL peak can be attributed to size variation of the CdTe QDs. In particular, carrier dynamics in CdTe QDs grown on various ZnTe buffer layer thicknesses is studied using time-resolved PL measurements. As a result, the decay time of CdTe QDs is shown to increase with increasing ZnTe buffer layer thicknesses due to the reduction of the exciton oscillator strength in the larger QDs.