形貌可控的CdS微米/纳米结构的表征和发光性能(英文)

利用简单的热蒸发CdS粉末方法,可合成出高质量的CdS微米柱。通过调控Si衬底上Au膜的厚度,能够大面积合成出尺寸均一的CdS纳米带和纳米棒。系统地研究了所合成样品的相、微结构和光致发光特性。室温下样品的发光结果表明可在所合成CdS微米柱上观察到位于约512 nm对应于其带隙的强发光峰。与CdS微米柱不同的是,可在所合成的CdS纳米带和纳米棒样品上分别观测到位于约521和543 nm,528和550 nm处对应于带边附近的发射强峰。并且,所合成的CdS纳米带和纳米棒展现出位于约710和712 nm位置处的宽峰,该峰的出现与结构缺陷、离子缺陷或杂质有关。与CdS纳米带的发光性能相比,所合成的CdS纳米棒表现出增强的发光性能。     

K元素对CdS晶体光学及电学性能的影响

采用物理气相输运(PVT)法生长了直径为50 mm的K掺杂CdS晶体,对掺杂和未掺杂的CdS晶片进行显微观察、二次离子质谱(SIMS)成分分析、红外光谱透过率以及霍尔效应测试,研究了K元素掺杂对CdS晶体光学及电学性能的影响.生长时用KCl进行掺杂.显微观察显示,掺杂KCl后CdS晶体的微观形貌没有明显变化;SIMS成分测试表明,晶体中引入的杂质主要是K元素,而Cl元素未掺入晶体中.红外光谱透过率发现掺杂K元素的CdS晶体相比于未掺杂晶体,不仅在波长为2.5～ 10 μm内红外透过率显著下降,而且在波长为10μm以上时红外透过率甚至低于15％.另外,K元素掺杂CdS晶体电学性能也发生变化,晶体迁移率也由未掺杂的318 cm2/ (V·s)下降为146 cm2/ (V·s).     

低温磁控溅射制备CdS薄膜的结构和光学特性

用磁控溅射的方法在透明导电氧化物衬底上制备了CdS薄膜,制备时的衬底温度为30~200℃.X射线衍射测试结果表明在这一条件下制备的CdS薄膜是六角纤锌矿的多晶结构.扫描电子显微镜结果显示薄膜具有较好的晶体质量,这一结论也和拉曼光谱、紫外-可见吸收光谱、光致发光光谱的结果一致.拉曼光谱显示CdS薄膜内部的压应力随着制备温度的提高而增大.     

Z-scan分析CdS纳米晶掺杂玻璃的光学非线性

利用溶胶-凝胶方法合成了CdS纳米晶掺杂Na2O-B2O3-SiO2玻璃.通过透射电镜(TEM)以及附带的扫描模式透射(STEM),X射线能量散射谱(EDX)和高分辨透射电镜(HRTEM)分析CdS颗粒的形貌、微结构以及组成.结果显示,在钠硼硅玻璃先驱体中生成了CdS纳米晶,其晶相结构为六方相结构,颗粒尺寸在10～20 nm.此外,利用Z-scan技术在波长为770 nm研究该玻璃的三阶非线性光学性质.结果表明:该玻璃的三阶光学非线性折射率γ,三阶非线性吸收系数β以及三阶非线性磁化率x(3)分别为-2.16×10-16m2W-1,6.32×10-11mW-1和7.32×10-10esu.优于此前一些关于CdS纳米晶掺杂在不同基体中所得到的三阶非线性光学性质的结果.     

加CdS薄层的有机电致磷光白光器件性能的优化

采用CBP和MCP做主体,分别掺杂磷光铱配合物Ir(piq)2(acac)和FIrpic作为红光发光层和蓝光发光层,研究了红光发光层和蓝光发光层的位置对器件性能的影响,得出结构为ITO/2T/NPB/MCP∶Firpic/CBP/CBP∶Ir(piq)2(acac)/Bphen/CdS/LiF/Al的器件性能较好。当CdS的厚度为0.1nm,电流密度为161mA/cm2时,器件的最大效率比不加CdS的器件的最大效率提高了1.42倍。亮度也有较大提高。在电流密度为225mA/cm2(电压为17.5V)时,最大亮度为20 890cd/m2,比不加CdS的器件的最大亮度16 610cd/m2高出4 280cd/m2。     

基于PPMgLN的中红外光学参量振荡器研究

对一种基于被动调Q周期极化MgO:LiNbO3(PPMgLN)中红外光学参量振荡器(OPO)的进行了研究.利用Nd:YVO4/Cr4+:YAG被动调Q激光器作为泵浦源,输出得到了1.78 W波长为1064 nm的泵浦光,其脉冲宽度和重复频率分别为10 ns和50 kHz,在倍频晶体PPMgLN作用下,输出得到了波长为3.2 μm功率为360 mW闲频光,光光转换效率达到了20％.周期极化MgO:LiNbO3 (PPMgLN)晶体的极化周期范围为29μm到31.5 μm.通过周期调谐和温度调谐的联合作用,光学参量振荡器(OPO)能够在波长范围3.0～4.0 μm内进行调谐.     

在CdS吸收型热光双稳态现象中的空间效应

在CdS单晶片(厚度为1～3μm)上,用Ar~+激光(λ=514.5nm)作光源,实现了室温热光光学双稳态(OB),记录了热光光学双稳态下的横向空间效应和开关波。研究了在热光光学双稳态和热击穿状态下晶体的不同性状,估算出相互独立工作的热光OB元件之间的最小距离为200μm。     

β-Ni(OH)2和NiO单晶纳米结构的水热合成与TEM表征

用水热法合成了β-Ni(OH)2单晶纳米薄片,并用透射电子显微镜观察其显微结构.发现这些纳米薄片呈六边形,横向尺寸45 nm～140 nm,厚度20 nm～50 nm.六边形纳米片的上下表面是(001),六个侧面可确定为(100),((1)10)或(0(1)0),紧邻侧面夹角120°.六角结构的β-Ni(OH)2呈六边形时系统能量最低.β-Ni(OH)2纳米薄片经500 ℃热分解即转化为NiO单晶纳米卷、纳米槽和纳米片.NiO纳米结构的外缘尺寸为25 nm～120 nm,纳米卷内空尺寸10 nm～24 nm,纳米槽凹坑尺寸10 nm～20 nm.β-Ni(OH)2纳米薄片中可能存在缺陷、微孔或结晶较差的区域,这些区域的热分解速率快,有利于形成NiO纳米卷.     

CdTe和CdS量子点的非线性特性对比

应用Top-hat Z-scan技术在波长为532 nm,脉宽为190 fs激光脉冲下研究了CdTe和CdS量子点的光学非线性吸收和非线性折射特性。实验结果表明:在飞秒激光脉冲作用下,CdTe量子点的非线性吸收表现为饱和吸收,CdS量子点表现为反饱和吸收。CdTe量子点的非线性折射表现为自散焦,CdS量子点表现为自聚焦。尺寸分别为2.6、2.4 nm的CdTe量子点和CdS量子点的非线性吸收系数分别为-9.2610-14、0.7810-14 m/W,非线性折射率系数分别为-0.8610-20、1.4610-20 m2/W,三阶非线性极化率分别为2.7210-15、1.3610-15 esu。表明相近尺寸下不同材料的镉类半导体量子点的光学非线性吸收和非线性折射特性不同,并对其机理进行分析。     

CdS薄层对有机电致发光器件性能的影响

将光电材料硫化镉(CdS)薄层插入到结构为ITO/NPB/Rubrene/NPB/DPVBi/Alq3/LiF/Al的白光有机发光器件(OLED)的Alq3和LiF之间,研究了CdS对OLED性能的影响。结果表明,0.1nm厚的CdS插入Alq3和LiF之间的器件性能最好。器件电压从7 V变化到14 V时,色度均在白光的中心区域;当电压为7V时,器件的最大电流效率为9.09cd/A;当电压为14V时,器件的最大亮度为16 370cd/m2。不加CdS时,当电压为8V时,器件的最大效率为5.16cd/A;当电压为14V时,最大亮度为6 669cd/m2。加CdS的器件比不加CdS的器件最大效率提高了1.76倍,最大亮度提高了2.42倍。     

Effects of post-annealing treatment on the structure and photoluminescence properties of CdS/PS nanocomposites prepared by sol-gel method

CdS nanocrystals have been successfully grown on porous silicon (PS) by sol-gel method. The plan-view field emission scanning electron microscopy (FESEM) shows that the pore size of PS is smaller than 5 μm in diameter and the agglomerates of CdS are broadly distributed on the surface of PS substrate. With the increase of annealing time, the CdS nanoparticles grow in both length and diameter along the preferred orientation. The cross-sectional FESEM images of ZnO/PS show that CdS nanocrystals are uniformly penetrated into all PS layers and adhere to them very well. photoluminescence (PL) spectra demonstrate that the intensity of PL peak located at about 425 nm has almost no change after the annealing time increases. The range of emission wavelength of CdS/PS is from 425 nm to 455 nm and the PL intensity is decreasing with the annealing temperature increasing from 100 °C to 200 °C.     

Size Effects of Platinum Nanoparticles in the Photocatalytic Hydrogen Production Over 3D Mesoporous Networks of CdS and Pt Nanojunctions

Catalysts for the photogeneration of hydrogen from water are key for realizing solar energy conversion. Despite tremendous efforts, developing hydrogen evolution catalysts with high activity and long‐term stability remains a daunting challenge. Herein, the design and fabrication of mesoporous Pt‐decorated CdS nanocrystal assemblies (NCAs) are reported, and their excellent performance for the photocatalytic hydrogen production is demonstrated. These materials comprise varying particle size of Pt (ranging from 1.8 to 3.3 nm) and exhibit 3D nanoscale pore structure within the assembled network. Photocatalytic measurements coupled with UV–vis/NIR optical absorption, photoluminescence, and electrochemical impedance spectroscopy studies suggest that the performance enhancement of these catalytic systems arises from the efficient hole transport at the CdS/electrolyte interface and interparticle Pt/CdS electron‐transfer process as a result of the deposition of Pt. It is found that the Pt‐CdS NCAs catalyst at 5 wt% Pt loading content exerts a 1.2 mmol h^?1 H₂‐evolution rate under visible‐light irradiation (λ ≥ 420 nm) with an apparent quantum yield of over 70% at wavelength λ = 420 nm in alkaline solution (5 m NaOH), using ethanol (10% v/v) as sacrificial agent. This activity far exceeds those of the single CdS and binary noble metal/CdS systems, demonstrating the potential for practical photocatalytic hydrogen production.     

Tm:YAP激光晶体光谱参数的计算

采用丘克劳斯基(Czochralski)法生长了Tm:YAP晶体,研究了该晶体在室温下的吸收光谱和荧光光谱.结果表明,Tm:YAP晶体在689.5 nm和795 nm左右有较强的吸收峰,分别对应于3H6→3F3和3H6→3H4的能级跃迁,半峰全宽(FWHM)分别为22.5 nm和30 nm,吸收截面分别为1.89×10-20 cm2和1.35×10-20 cm2.荧光光谱表明Tm:YAP晶体发射波长为1.89μm,相应的荧光寿命为13.90 ms,发射截面为1.58×10-19 cm2.根据乍得-奥菲特(Judd-Ofelt)理论计算了Tm3+在Tm:YAP晶体中的强度参数:Ω2=1.4560×10-20cm2,Ω4=2.0673×10-20 cm2,Ω6=0.3181×10-20 cm2.结果表明,Tm:YAP晶体具有宽的吸收峰、长荧光寿命和较大的积分发射截面的性质,非常适合于激光二极管(LD)抽运,有利于获得低阈值高效率的2μm波段激光输出.     

Ge-As-Se-Te硫系玻璃的飞秒激光损伤特性

Ge-As-Se-Te（GAST）硫族化物玻璃拥有超过20 μm的超宽透射范围,是一种可应用于中红外（MIR）和远红外(FIR)波段的优良光学材料。通过熔融淬火法制备了Ge_xAs_40?xSe₄₀Te₂₀（x = 0、10、20、30、40 mol%）系列硫系玻璃,采用不同波长（800 nm,3 μm和4 μm）、功率和重复频率的飞秒激光辐照硫系玻璃,利用扫描电子显微镜（SEM）和拉曼光谱等手段研究了GAST的激光损伤特性。研究结果发现,Ge_xAs_40-xSe₄₀Te₂₀玻璃的激光诱导损伤阈值（LIDT）随着样品中Ge含量的增加而增加,在800 nm下Ge₃₀As₁₀Se₄₀Te₂₀玻璃的LIDT达到最高40.16 mJ/cm2。随着飞秒激光波长增加,系列玻璃的LIDT也逐步增加,Ge₃₀As₁₀Se₄₀Te₂₀在4 μm激光辐照下LIDT达到81.09 mJ/cm2。此外,研究结果表明样品LIDT随着激光的脉冲辐照数量和重复率的增加将逐渐减小。     

Research on the preparation and growth mechanism of ZnO micro/nano nails

High quality zinc oxide (ZnO) micro/nano nails were prepared through thermal evaporation on the Si (100) substrate. Scanning electron microscopy (SEM) image shows that the bottom of the nanometer nails present hexagonal structure. The tip diameter of the micro/nano nails is about 319.9 nm, and the length is over 20 μm. X-ray crystal diffraction (XRD) pattern shows that the sample has a hexagonal wurtzite structure and preferred orientation in (002) direction obviously. Photoluminescence (PL) spectrum shows a strong ultraviolet (UV) luminescence peak near the wavelength of 346 nm. Finally, the growth mechanism of the ZnO micro/nano nails is analyzed and studied.     

Solvothermal synthesis and photocatalytic properties of CdS nanowires under UV and visible irradiation

CdS nanowires (NWs) were synthesized by the solvothermal method. The synthesis yields NWs with hexagonal phase structure. The phase, vibration modes, morphologies and optical properties of CdS NWs were investigated by X-ray powder diffraction (XRD), Raman spectrophotometry, scanning and transmission electron microscopy (SEM and TEM) and UV–visible spectroscopy, respectively. The results show that the as-synthesized product is hexagonal CdS NWs with the diameter of 20–30 nm and length of up to 5 μm. Photocatalytic degradation of methyl orange (MO) and rhodamine B (RhB) was investigated. It was found that CdS NWs possess excellent catalytic degradation activity owing to their effective absorption over the visible range. The highly photocatalytic activity suggested possible application in the treatment of organic pollutants under visible light irradiation.     

Capillary force assembly of giant vesicles on a microstructured substrate

Convective capillary force assembly has shown to efficiently assemble nm to μm solid colloids onto a surface. We show here that this technique can also efficiently trap liposomes with 10 μm mean size or films of lipid into microstructures. We hypothesize that whether liposomes or lipids are trapped in the template depends on the interfacial interaction of the objects with the surface. After solvent evaporation, ruptured and deflated liposomes are observed onto oxidized (hydrophilic) PDMS while uniform films of lipids are found in untreated (hydrophobic) PDMS microstructures. This assumption is supported by the analysis of the evaporation of a droplet containing a dispersion of liposomes in free environment.     

CdS0.2Se0.8纳米晶掺杂玻璃的超快非线性吸收特性

利用飞秒脉冲通过Z扫描技术和泵浦-探测技术研究了CdS0.2Se0.8纳米晶掺杂的硼酸盐玻璃滤波片RG665的非线性吸收特性。研究结果表明在800 nm波长 130 fs脉冲激光作用下,RG665滤波片表现较强的非线性吸收特性。通过理论分析拟合实验结果证明RG665滤波片在800 nm下的非线性吸收包含双光子吸收及双光子吸收诱导的激发态吸收两部分,得到双光子吸收系数为0.05 cm/GW,激发态吸收截面为e=310-23 m2,以及导带中低能态电子和导带底电子的寿命分别为13 ps和210 ps。研究结果表明CdS0.2Se0.8纳米晶体掺杂的玻璃是一种很好的非线性光学材料。