CdS量子点敏化ZnO薄膜的制备及其性能研究

本文以Zn(CH3COO)2·2H2O、CdCl2和硫脲的水溶液分别为前驱体,采用超声喷雾热解法在ITO导电玻璃上成功的制备了CdS量子点敏化ZnO薄膜(ZnO∶ CdS).通过扫描电镜(SEM),X射线衍射(XRD),光致发光(PL)谱和吸收光谱对CdS量子点敏化ZnO薄膜形貌,结构和光学性能进行了研究.SEM图表明CdS量子点已成功沉积到ZnO薄膜上,量子点呈颗粒状,直径约71 nm.XRD结果显示,除观察到原有的ZnO特征峰外,在2θ=30.3°处有一明显的特征峰,对应着CdS的(111)晶面.PL谱图表明在325 nm的光激发下,CdS量子点敏化ZnO薄膜在400 nm处有一较强的紫外发射峰,在500～700 nm处有一个较宽的黄绿发射带.吸收光谱表明,CdS量子点敏化后ZnO薄膜在可见光区的吸收边为586 nm.     

长径比可控的CdS纳米棒制备及光催化性能研究

采用溶剂热法制备了长径比可控的纤锌矿CdS纳米棒;以3CdSO4·8H2O、CH4 N2S为原料在180℃、24 h溶剂热反应条件下,通过改变Cd/S物质的量比和保温时间等因素来调节CdS纳米棒的长径比.利用扫描电镜(SEM)、X射线衍射(XRD)、紫外可见吸收光谱(UV-Vis)、光催化分别对其形貌、结构和光催化性能进行了表征和分析.结果表明:Cd/S摩尔比对CdS棒的生长起到关键作用,随着镉硫比的减小,CdS纳米棒的长径比逐渐增大.当Cd/S摩尔比为1∶6时,制备的CdS为长径比较大且表面光滑的纳米棒,纳米棒的尺寸大约为长800 nm、直径70nm.通过降解亚甲基蓝溶液测试了CdS纳米材料的可见光照射下的光催化性能,结果表明具有大长径比的CdS纳米棒表现出优异的光催化活性.     

CdS纳米晶颗粒薄膜的制备及其光学特性研究

采用化学浴沉积法,以CdCl2·H2O、CS(NH2)2、NH4Cl、NH3·H2O和去离子水作为反应前驱物,在不同的氨水浓度下制备CdS纳米晶颗粒薄膜.通过扫描电镜、X射线衍射、X射线能量色散谱、紫外-可见光透射光谱、椭圆偏振光谱等方法,研究了反应前驱物中氨水浓度对CdS纳米晶颗粒薄膜的表面形貌、晶体结构、S/Cd原子比、光透过率、光学带隙、折射率、消光系数和光学吸收边等物理性能的影响.结果表明:反应前驱物中氨水浓度在0.4～1.0mol/L范围内,可以在衬底上形成均匀致密的CdS纳米晶颗粒薄膜.随着氨水浓度的增加,CdS纳米晶的平均晶粒尺寸逐渐减少,S/Cd原子比逐渐增加,由富Cd型转变为富S型,禁带宽度逐渐增加.在500～1000 nm波段内,折射率的平均值为1.75;消光系数k小于0.07.     

CdS纳米棒的水热法制备及形成机理研究

采用水热法以Na2S· 9H2O为硫源,Cd3O12S3·8H2O为镉源,PVP为表面活性剂,成功制备了CdS纳米棒.并利用X射线衍射(XRD)、透射电子显微镜(TEM)和相应选区电子衍射(SAED)、高分辨透射电子显微镜(HRTEM)、X射线能量色散分析谱仪(XEDS)和紫外可见(UV-vis)分光光度计等测试手段对样品的晶体结构、形貌、微观结构和光学特性等特征进行了表征分析,实验结果表明本方法所制备的CdS纳米棒为纤锌矿结构,沿[001]方向择优生长,平均直径大约为50 nm,棒宽均匀、分散性好,带隙为2.43 eV.同时也对CdS纳米棒的形成机理进行了初步探讨,提出了CdS纳米棒的生长模型,其形貌从三角形到阶梯形棒晶,最后再到完整的棒状晶体的一个定向团聚的自组装过程.     

钒酸铜空心纳米结构的制备及电化学性能

以CuSO4·5H2O和NH4VO3为原料,聚苯乙烯(PS)微球为模板,采用模板法制备了具有空心结构Cu3V2O7(OH)2·2H2O材料.采用X射线衍射(XRD)和场发射扫描电子显微镜(FE-SEM)对不同结构的Cu3V2O7(OH)2·2H2O的组成和形貌进行了表征.实验发现通过控制反应温度及反应体系的pH值可实现对Cu3V2O7(OH)2·2 H2O材料微观结构及形貌的良好控制.电化学性能测试表明:不同结构的Cu3V2O7 (OH)2·2H2O材料其放电性能存在着明显的差异,具有蜂窝状结构的Cu3V2O7 (OH)2·2H2O展现出较高的放电比容量,25℃条件下其首次放电容量可达到489 mAh/g.     

CdTe量子点生长速率的参数研究

以NaTeO3为碲源,还原型谷胱甘肽(GSH)为稳定剂,一步合成CdTe量子点.研究了参与反应回流的镉与碲摩尔比和Cd2+浓度对CdTe量子点生长速率的影响,并用荧光光谱、X射线衍射光谱及透射电子显微镜对其性能进行表征.结果表明:GSH稳定的CdTe量子点具有闪锌矿结构、球形形貌;在pH =8.5,n(Cd2+)∶ n(GSH)=1∶1.2,C(Cd2)=0.67 mmol/L,n(Cd)∶ n(Te)=6∶1时,CdTe量子点荧光量子效率最高可达51.53;,并且量子点生长的速率在初期的1h内达到最高点,并随着时间的延长呈下降趋势.     

微波水热法制备六方片状CdS团簇

采用微波水热法,以氯化镉(CdCl2·H2O)和硫代乙酰胺(CH3CSNH2)为镉源和硫源,制备了具有六方片状结构的CdS微晶。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、EDS、透射电子显微镜(TEM)和高分辨透射电子显微镜(HRTEM)等对样品的物相、形貌和元素组分进行了分析,并采用紫外吸收光谱表征其光学性能。结果表明:以CH3CSNH2为硫源合成的CdS微晶具有六方片状团簇的特殊形貌,通过与相同条件下以Na2S2O3·5H2O为硫源合成CdS晶的FE-SEM照片对比发现,CH3CSNH2在此特殊形貌的制备过程中起到了重要作用。通过紫外吸收光谱得出,样品的禁带宽度为3.82 eV,蓝移量达到了1.37 eV。     

PbS/CdS纳米晶共敏化ZnO纳米线太阳能电池的性能研究

以Zn (Ac)2·2H2O为原料在强碱性条件下合成一维结构的ZnO纳米线,SEM结果表明合成的纳米线尺寸、形貌、长径比均一;并以油胺为单一溶剂采用热注射法制备了形貌、尺寸均匀的PbS纳米晶;构建PbS纳米晶敏化ZnO纳米线基太阳能电池,同时为了改善电池的光电转换效率并构建了PbS/CdS纳米晶共敏化电池,并测试了电池的光电流密度-光电压(J-v)曲线以及Nyquist曲线图,结果表明PbS/CdS纳米晶共敏化电池性能明显优于单纯的PbS纳米晶敏化ZnO纳米线太阳能电池.     

双金属磷化物NiCoP的次磷酸盐还原法制备及其表征

以六水合氯化镍(NiCl2·6H2O)、六水合氯化钴(CoCl2·6H2O)和次亚磷酸钠(NaH2PO2·H2O)为原料,采用次磷酸盐还原法合成双金属磷化物NiCoP.通过X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)及氮气吸附-脱附分析对所制备样品的物相、结构进行了表征.结果表明:所制备产物双金属磷化物NiCoP纳晶为六方晶相无特定形貌的颗粒,颗粒尺寸约为10～50 nm.对所得样品吸附性能测试发现,本法制备的双金属磷化物NiCoP对有机染料具有较好的吸附脱除性能.     

一维梯状配位聚合物[Cd(nic)(bdc)0.5(H2O)2]n· 2nH2O的合成及表征

此文介绍一个一维梯状镉配位聚合物[Cd(nic)(bdc)0.5(H2O)2]n·2nH2O(1)(Hnic=烟酸,H2bdc=1,4-苯二甲酸),并通过X-射线单晶衍射、元素分析、红外光谱、热重分析对其结构进行表征.梯形梯框为[Cd(nic)(H2O)2]+链,梯级为bdc2-配体.梯状长链通过氢键相互作用连接形成三维超分子网状结构,在室温下,聚合物1显示蓝色荧光性能.     

Controllable surface‐state emission from colloidal CdS quantum dots under different growth conditions

High‐quality colloidal photoluminescent CdS quantum dots (QDs) were synthesized in non‐coordinating solvent octadecene (ODE) using oleic acid (OA) as capping molecule, and characterized by powered x‐ray diffraction (XRD), transmission electron microscope (TEM), UV‐Vis absorption spectra, photoluminescence (PL) emission spectroscopy and time‐resolved emission spectroscopy. The effects of the growth time, the molar ratio of OA/Cd and Cd/S on the PL intensity from surface‐state have been investigated. We found that the surface‐state emission could be easily controlled by tuning the growth time and the molar ratio of Cd/S.     

Photoinduced Modulation of the Emission from СdSe/ZnS Quantum Dots by Photochromic Transformations of Diarylethenes

Crystallography Reports - A spectral study of the interaction between the molecules of photochromic compounds of the diarylethene class and CdSe/ZnS quantum dots (QDs), in dependence of the...     

PbS量子点/MoO3纳米带复合材料的低温气敏性能研究

采用液相法制备PbS量子点修饰MoO3纳米带复合材料.利用XRD、FESEM、TEM、EDS等表征手段分析样品组成、结构与形貌,分别将MoO3纳米带、PbS量子点、PbS量子点/MoO3纳米带组装成陶瓷管气敏元件并测试其对NH3的气敏性能.结果表明,在低温(20~100 ℃)下PbS量子点/MoO3纳米带复合材料对NH3具有良好检测能力,最低测试限为10 ppm.由于PbS量子点均匀分布在MoO3纳米带表面可形成异质结界面,这可有助于电子、空穴的分离,从而显著改善电子传输性能和气敏特性.     

不同形貌TiO2薄膜的可控制备及其光电化学性能研究

采用水热法在FTO(fluorine-doped tin oxide)基底上制备不同形貌的锐钛矿结构TiO₂薄膜。通过不断增大反应前驱物中盐酸浓度,TiO₂薄膜由球状颗粒薄膜逐渐演变生长成大面积高能(001)面裸露的TiO₂纳米片阵列薄膜。通过对形貌演化规律及X射线衍射图谱变化规律进行分析,提出了不同形貌TiO₂薄膜的生长演化机制,并对盐酸在其中的作用进行了说明。为了进一步改善TiO₂薄膜的性能,采用连续离子层吸附反应法对不同形貌的TiO₂薄膜进行CdS量子点敏化。采用紫外可见吸收光谱分析法和三电极体系对复合薄膜的光吸收性能和光电化学(PEC)性能进行了研究,实验数据显示CdS/TiO₂复合薄膜的光电化学性能皆明显优于单纯TiO₂薄膜,而且纳米片阵列薄膜的性能明显优于其他形貌薄膜,说明了大面积高能(001)面裸露的TiO₂纳米片阵列薄膜的性能优越性。     

Optical properties of PbSe quantum dots doped in borosilicate glass

PbSe quantum dots (QDs) were synthesized in borosilicate glass and their optical properties were investigated. The typical quantum confinement effects were clearly observed from the absorption when the average radii of the QDs changed from 1.7 to 3.1 nm. Photoluminescence from PbSe QDs was achieved in 1.1–2.2 μm wavelength region that covers the entire fiber-optic telecommunication window. Borosilicate glasses containing controlled size of PbSe QDs provide potentials for the fiber-optic amplifiers.     

Self-assembled InAs quantum dots with two different matrix materials

The effects of matrix materials on the structural and optical properties of self-assembled InAs quantum dots (QDs) grown by a molecular beam epitaxy were investigated by atomic force microscopy, cross-sectional transmission electron microscopy (TEM), and photoluminescence (PL) spectroscopy. Cross-sectional TEM image indicated that the average lateral size and height of InAs QDs in a GaAs matrix on a GaAs substrate were 20.5 and 5.0 nm, respectively, which showed the PL peak position of 1.19 μm at room temperature. The average lateral size and height of InAs QDs buried in an InAlGaAs matrix on InP were 26.5 and 3.0 nm, respectively. The PL peak position for InP-based InAs QDs was around 1.55 μm at room temperature. If we only consider the size quantization effects, the difference in PL peak position between two QD systems with different matrices may be too large. The large difference in peak position can be mainly related to the QD size as well as the strain between the QDs and the matrix materials. The intermixing between the QDs and the matrix materials can partially change the In composition of QDs, resulting in the modification of the optical properties.     

Properties of self-assembled InAs quantum dots grown by various growth techniques

The properties of self-assembled InAs quantum dots (QDs) grown by molecular beam epitaxy on GaAs substrates were investigated. The surface properties of samples were monitored by reflection high-energy electron diffraction to determine growth. Photoluminescence (PL) and transmission electron microscope (TEM) were then used to observe optical properties and the shapes of the InAs-QDs. Attempts were made to grow InAs-QDs using a variety of growth techniques, including insertion of the InGaAs strained-reducing layer (SRL) and the interruption of In flux during QD growth. The emission wavelength of InAs-QDs embedded in a pure GaAs matrix without interruption of In flux was about 1.21 μm and the aspect ratio was about 0.21. By the insertion InGaAs SRL and interruption of In flux, the emission wavelength of InAs-QDs was red shifted to 1.37 μm and the aspect ratio was 0.37. From the PL and TEM analysis, the properties of QDs were improved, particularly when interruption techniques were used.     

Self-alignment of self-assembled InAs quantum dots

The lateral self-alignment properties of self-assembled InAs quantum dots (QDs) on a conventional GaAs (1 0 0) substrate by molecular beam epitaxy were investigated. The shape and optical properties of QDs were investigated by atomic force microscopy, transmission electron microscope, and photoluminescence (PL). Attempts were made to grow InAs-QDs using the In-interruption growth technique, in which the In flux was periodically interrupted. QDs grown without using the In-interruption growth technique were grown randomly on all regions. On the other hand, in the case of QDs grown using the In-interruption growth technique, QDs were self-aligned at the boundary between bright and dark regions, the PL intensity was increased and the PL peak position of QDs were red-shifted to 1300 nm. This represent a new technique for growing self-aligned QDs because no extra processing such as electron-beam lithography, V-grooves and surface modification by scanning tunneling microscopy is needed, and aligned QDs can be grown in situ on conventional GaAs substrates.     

Step annealing effects on the structural and optical properties of InAs quantum dots grown on GaAs

The effects of multi-step rapid thermal annealing (RTA) for the self-assembled InAs quantum dots (QDs), which were grown by a molecular beam epitaxy (MBE), were investigated through photoluminescence (PL) and transmission electron microscopy (TEM). Postgrowth multi-step RTA was used to modify the structural and optical properties of the self-assembled InAs QDs. Postgrowth multi-step RTAs are as follows: one step (20 s at 750 °C); two step (20 s at 650 °C, 20 s at 750 °C); three step (30 s at 450 °C, 20 s at 650 °C, 20 s at 750 °C). It is found that significant narrowing of the luminescence linewidth (from 132 to 31 meV) from the InAs QDs occurs together with about 150 meV blueshift by two-step annealing, compared to as-grown InAs QDs. Observation of transmission electron microscopy (TEM) shows the existence of the dots under one- and two-step annealing but the disappearance of the dots by three-step annealing. Comparing with the samples under only one-step annealing, we demonstrate a significant enhancement of the interdiffusion in the dot layer under multi-step annealing.     

Photoluminescence of PbS quantum dots embedded in glasses

Optical properties and photoluminescence of PbS quantum dots (QDs) embedded in glasses were investigated. Formation and radius of PbS QDs were carefully controlled though heat-treatment and modification of host glass composition. Heat-treatment conditions for precipitation of 3–10 nm radius QDs for the tunable photoluminescence in the 1–2 μm wavelength range were identified. Glasses doped with PbS QDs provide potential as robust materials for broadband fiber-optic amplifiers.