纳米CdS／聚（苯胺-邻氨基苯甲酸）复合薄膜的制备及表征

以苯胺和邻氨基苯甲酸为单体共聚而成的聚（苯胺-邻氨基苯甲酸）（PAOAA）为基体，制备了纳米CdS／PAOAA复合薄膜。纳米CdS粒子大小均匀，粒径分布窄，较稳定地存在于基体中，且随着硫化时间的延长粒径尺寸有所增加。荧光光谱表明纳米CdS／PAOAA复合薄膜的发光由CdS纳米粒子和PAOAA共同作用产生，在430nm和520nm附近出现了两大发光峰；CdS粒径的增加导致电子-空穴对在CdS内复合增大，表现为纳米CdS的荧光特征峰增强而PAOAA的荧光特征峰减弱。     

ZnS/PVA纳米复合薄膜的制备与表征

采用提拉真空干燥的方法制备出以石英玻璃为基板的ZnS/PVA纳米复合薄膜.ZnS/PVA纳米复合溶胶是通过直接混合法将ZnS纳米粒子与聚乙烯醇(PVA)高分子材料水溶液直接混合制备得到.ZnS纳米粒子由微乳液法制备得到.利用透射电子显微镜(TEM)和X射线衍射(XRD)分析表征了ZnS纳米粒子的微观形貌和晶型,TEM结果表明C12H25SH与Zn2 的比例越大,ZnS粒子的粒径越小且在PVA中的分散越好,当C12H25SH/Zn2 的比例为8∶1时,ZnS纳米粒子的粒径为50 nm,呈球状;XRD分析表明,PVA中ZnS纳米粒子具有类似于立方β-ZnS晶相.用紫外-可见(UV-VIS)吸收光谱和荧光光谱(PL)对其光学性能进行了表征,结果表明随着C12H25SH/Zn2 的摩尔比从4:1增长到8:1,ZnS/PVA纳米复合薄膜的吸收峰的强度逐渐增强,峰位也逐渐向短波长方向偏移.在280 nm下激发,PL中出现了峰位位于365 nm处的荧光发射峰;并且发现随着C12H25SH/Zn2 摩尔比从2:1增大到8:1,在C12H25SH/Zn2 摩尔比为4:1时,荧光发射峰的强度相对较大, 其余的荧光发射峰蓝移并且强度增大,表现出较为明显的量子尺寸效应;当C12H25SH/Zn2 摩尔比较大时,出现了低能发光(450 nm～467 nm)的现象.     

复合结构纳米晶CdS：Cu/CdS的制备及光学特性

在非配位溶剂中合成了高质量的CdS纳米晶核,并利用Cu2+离子对其进行掺杂,制备了CdS:Cu纳米晶.通过进一步采用连续离子层吸附反应的方法对CdS:Cu纳米晶进行表面修饰,得到CdS:Cu/CdS复合结构纳米晶.利用X射线衍射(XRD),透射电镜(TEM),紫外可见吸收光谱(UV-Vis)和荧光光谱(PL)对其结构、形貌以及光学性质进行了表征和分析,结果表明:所制备的复合结构CdS:Cu/CdS纳米晶为立方闪锌矿结构;与CdS纳米晶核相比,掺杂Cu2+可以使其表面态发光发生红移;在CdS:Cu纳米晶中,通过改变掺杂Cu2+的浓度,可以实现表面态发光在570和620nm之间的连续调节.与未经包覆的CdS:Cu纳米晶相比,包覆层CdS增强了纳米晶CdS:Cu的稳定性.     

核壳结构CdS/ZnS荧光量子点的制备与荧光性能研究

以氧化镉为镉源、硫单质为硫源、油酸为配体、在十八烯体系中合成单分散的CdS纳米颗粒,研究了配体浓度对纳米微粒的生长动力学、颗粒尺寸分布的影响.采用乙基黄原酸锌作为Zn、S源的反应前体,采用逐滴滴加的方法制备了具有核壳结构的CdS/ZnS量子点,吸收光谱和荧光光谱表明CdS/ZnS纳米粒子比单一的CdS纳米粒子具有更优异的发光特性.透射电子显微镜、X射线粉末衍射、X射线光电子能谱、选区电子衍射证明ZnS在CdS表面进行了有效包覆.所制备核壳结构纳米粒子具有较好的尺寸分布,荧光发射峰半高峰宽为18～20nm,荧光量子产率达40%.     

ZnO/CdS复合纳米粒子的热分解合成及发光性能

设计了简单的化学反应路线,在表面活性剂PEG400存在下通过简单的前驱体热分解反应合成了ZnO/CdS复合纳米粒子,其直径在4~10nm之间。前驱体则通过室温固相反应获得。用X射线衍射仪(XRD)和透射电子显微镜(TEM))对产物的结构和形貌进行了表征。同时,对产物的光致发光性能(PL)作了测试。结果表明:ZnO/CdS复合纳米粒子在380 nm处有一个较弱的归因于近带隙发射的发光峰,550 nm处较强的发射峰来自于由氧空位形成的深浅表面态所捕获的电子-空穴对的复合。另外,对它们的形成机理进行了简单的探讨。     

CdS及其稀土掺杂纳米带的制备与发光性质的研究

采用热蒸发法制备CdS及其稀土掺杂的纳米带(CdS∶Ce3+、CdS∶Er3+)。利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和荧光光谱仪(PL)对纳米带的形貌、晶体结构和发光性质进行了表征和分析。结果表明,所制备的纳米带的外形规则,表面光滑、平整,纳米带的厚度大约在20～60nm范围内;纳米带具有六方结构,晶格常数a=0.414nm、c=0.671nm;CdS纳米带的光致发光谱的谱峰位于405nm左右;CdS∶Ce3+纳米带的光致发光谱的谱峰位于523和535nm处;CdS∶Er3+纳米带的光致发光谱中观察到3个强的发光峰,分别位于525、556和582nm处。     

SBS-OH模板制备CdS纳米粒子及表征

以SBS为基本原料,通过大分子化学反应制备得到羟基化SBS(SBS-OH).以N,N-二甲基甲酰胺为溶剂,SBS-OH为模板,乙酸镉及硫化钠为前驱物,在常温条件下"原位反应"制备得到CdS纳米粒子.通过UV-Vis、PL系统考察了SBS-OH浓度、前驱物浓度及配比等因素对CdS纳米粒子光学性质的影响.通过TEM对CdS纳米粒子的尺寸及形貌进行了表征.研究表明,利用SBS-OH的两亲性质,可以在极性溶剂DMF中得到具有冠状复合结构的CdS纳米粒子.随着前驱物浓度的增加,CdS纳米粒子的吸收强度增加,吸收带边红移,表现出较明显的量子尺寸效应.PL光谱表明CdS纳米粒子可以产生表面缺陷态的荧光发光特性,通过对实验结果的总结分析,探讨了复合结构CdS纳米粒子可能的形成机制.     

双修饰Fe3O4/CdSe/CdS荧光磁性复合物的制备及其表征

采用共沉淀法制得Fe3O4溶胶,用γ-缩水甘油醚氧丙基三甲氧基硅烷(KH-560)对其表面进行改性,制得有机硅改性的纳米Fe3O4磁性粒子;用L-半胱氨酸盐酸盐(L-Cys)将油相的CdSe/CdS转成水相并带上氨基的CdSe/CdS纳米晶;将其复合制备了Fe3O4/CdSe/CdS荧光磁性双功能纳米复合物颗粒。该Fe3O4/CdSe/CdS复合物颗粒平均尺寸约为40nm,饱和磁化强度为21.287A.m2/kg,该纳米粒子既具有优异的荧光特性,也具有较强的超顺磁性。     

复合结构纳米晶CdS∶Cu/CdS的制备及光学特性

在非配位溶剂中合成了高质量的CdS纳米晶核,并利用Cu²⁺离子对其进行掺杂,制备了CdS∶Cu纳米晶.通过进一步采用连续离子层吸附反应的方法对CdS∶Cu纳米晶进行表面修饰,得到CdS∶Cu/CdS复合结构纳米晶.利用X射线衍射(XRD),透射电镜(TEM),紫外可见吸收光谱(UV-Vis)和荧光光谱(PL)对其结构、形貌以及光学性质进行了表征和分析,结果表明:所制备的复合结构CdS∶Cu/CdS纳米晶为立方闪锌矿结构;与CdS纳米晶核相比,掺杂Cu²⁺可以使其表面态发光发生红移;在CdS∶Cu纳米晶中,通过改变掺杂Cu²⁺的浓度,可以实现表面态发光在570和620nm之间的连续调节.与未经包覆的CdS∶Cu纳米晶相比,包覆层CdS增强了纳米晶CdS∶Cu的稳定性.     

壳聚糖-CdS复合纳米粒子对甲基橙的光催化降解作用

用反相微乳液法制备了壳聚糖-CdS复合纳米粒子,并考察了复合纳米粒子用量、光照条件和溶液pH值等因素对光催化降解甲基橙的影响.结果表明:在100 mL质量浓度为20 mg/L的甲基橙溶液中加入0.30 g复合纳米粒子,可以达到较好的光催化降解效果;甲基橙在光催化降解过程中最大吸收波长464 nm处的吸收峰迅速减弱,并最终消失,且在258 nm和455 nm处出现了新的吸收峰,说明甲基橙发生了降解;溶液pH值对光催化降解甲基橙有一定的影响,在弱酸性条件下降解效率较高;复合纳米粒子比普通CdS降解效率高,2 min时高出50%,400 min时高出21.3%.初步提出了复合纳米粒子光催化降解机理,复合纳米粒子的吸附作用是光催化降解作用的前置步骤.     

Preparation and characterization of water-soluble CdS nanocrystals by surface modification of ethylene diamine

The water-soluble CdS nanoparticles were obtained by hydrogen bond between the cadmium-thiolate complex on the surface of CdS nanoparticles and ethylene diamine (anhydrous). The modified CdS nanoparticles enhanced its solubility in H₂O and alcohol. The ethylene diamine-capped CdS nanoparticles were characterized by Fourier Transform Infrared Spectroscopy (FTIR), photoluminescence (PL) and Ultraviolet–Visible absorption spectrum (UV–Vis spectrum). The absorption peak at 262 nm was observed, which belonged to ethylene diamine-modificated Cd-thiolate complex at the surface of as-grown CdS nanoparticles. The results of the PL spectra indicated that the modification of CdS nanoparticles reduced effectively the local surface-trap states. Based on the above results, a possible mechanism for the formation of the water-soluble CdS nanoparticles was discussed.     

Studies on optical absorption and photoluminescence of thioglycerol-stabilized ZnS nanoparticles

ZnS quantum dots of size 3 nm are prepared at 303 K using ZnSO₄ and Na₂S₂O₃ precursors with thioglycerol as stabilizing agent. Cd²⁺ doped ZnS were prepared by varying doping concentration from 1 to 8 wt.%. ZnS quantum dots were mixed with CdS quantum dots of size 4 nm in the 3:1, 2:1, 1:1, 1:2, 1:3 and 1:4 M ratio. The nanoparticles were characterized by UV–vis, photoluminescence (PL), XRD and high-resolution TEM measurements. The XRD pattern, high-resolution TEM image and SAED pattern reveal that the nanoparticles are in well-crystallized cubic phase. The band gap of ZnS has increased from the bulk value 3.7 to 4.11 eV showing quantum size effect. Excitonic transition is observed at 274 nm in UV absorption and PL emission at 411 nm. Doping with Cd²⁺ red-shifts both UV and PL spectral bands and enhances the PL band of ZnS nanoparticles. Mixing CdS and ZnS quantum dots in different molar ratios shows red-shift of the band edge in the CdS/ZnS hybrid system. In the 1:1 hybrid system of CdS/ZnS nanoparticles, PL band is red-shifted and the intensity is almost doubled with respect to that of CdS nanoparticles.     

Effect of heat-treatment on CdS and CdS/ZnS nanoparticles

Mono-dispersed and spherical cadmium sulfide (CdS) nanoparticles and cadmium sulfide/zinc sulfide (CdS/ZnS) nanoparticles, 4–5 nm in diameter, were synthesized in a heptane-AOT-water microemulsion system. The heat treatment of CdS and CdS/ZnS nanoparticles was annealed at 570 °C under the air atmosphere. The heat-treated nanoparticles were of variable large sizes and had enhanced crystallinity. UV–Vis spectra of heat-treated CdS and CdS/ZnS nanoparticles revealed a flat shape similar to that of bulk CdS compounds. The difference between the PL emission bands of organic-coated nanoparticles and heat-treated nanoparticles was small. The PL emission energy of heat-treated nanoparticles was improved by about 2–3 times compared with that of organic-coated nanoparticles.     

Ag-SiO2复合纳米颗粒薄膜的制备及其光学特性研究

利用溶胶一凝胶法在玻璃基底上成功制备了Ag—SiO2复合纳米颗粒薄膜,SEM、TEM和XRD的表征分析表明Ag是以单晶纳米颗粒的形态均匀分散在SiO2基质中,形成了多孔状Ag—SiO2复合纳米颗粒薄膜。从Ag—SiO2复合纳米颗粒薄膜的光吸收谱发现,该复合薄膜中鲰纳米颗粒具有较强的等离子共振吸收峰,峰位在430nm附近,随着复合薄膜中Ag、Si摩尔比的逐渐增大,等离子共振吸收峰不断增强且发生蓝移,蓝移量可达30nm;研究Ag—SiO2复合纳米颗粒薄膜的光敛发光特性发现,当激发波长为220nm时,复合薄膜分别在330nm和375nm处出现了两个发光带,随着复合薄膜中Ag、Si摩尔比增大到0．11,两发光带均逐渐增强,继续增加Ag、Si摩尔比,两发光带又逐渐减弱,且375nm处的发光带变化尤为显著。     

CdSe/Cd(x)Zn1-xS core/shell nanocrystals: core morphology and luminescent property

CdSe cores with rod (an aspect ratio of 1.8, d-5 nm) and spherical (an aspect ratio of 1, d-5 nm) morphologies were fabricated by two kinds of organic approaches through adjusting growth processes. Because of large difference of size and morphology, two kinds of cores revealed different absorption spectra. However, these cores exhibited almost same photoluminescence (PL) spectra with a red-emitting PL peak of around 625 nm. This is ascribed that they have a similar size in diameter. A graded Cd(x)Zn1-xS shell of larger band gap was grown around CdSe rods and spheres using oleic acid as a capping agent. Based on the growth kinetics of CdS and ZnS, interfacial segregation was created to preferentially deposit CdS near the core, providing relaxation of the strain at the core/shell interface. For spherical CdSe cores, the homogeneous deposition of the Cd(x)Zn1-xS shell created spherical core/shell nanocrystals (NCs) with a size of 7.1 nm in diameter. In the case of using CdSe cores with rod morphology, the anisotropic aggregation behaviors of CdS monomers on CdSe rods led to the size (approximately 10 nm in diameter) of spherical CdSe/Cd(x)Zn1-xS core/shell NCs with a small difference to the length of the CdSe rod (approximately 8.9 nm). The resulting spherical core/shell NCs created by the rod and spherical cores exhibited almost same PL peak wavelength (652 and 653 nm for using rod and spherical cores, respectively), high PL efficiency up to 50%, and narrow PL spectra (36 and 28 nm of full with at half maximum of PL spectra for the core/shell NCs with CdSe spheres and rods, respectively). These core/shell NCs provide an opportunity for the study of the evolution of PL properties as the shape of semiconductor NCs.     

CdS nanoparticles grown in a polymer matrix by chemical bath deposition

Nanocrystallites of CdS have been grown by chemical bath deposition within the pores of poly(vinyl alcohol) (PVA) on glass and Si substrates. The CdS-PVA composite films are transparent in the visible region. XRD and TEM diffraction patterns confirmed the nanocrystalline CdS phase formation. TEM study of the film revealed the manifestation of nano CdS phase formation and the average particles size was varied in the range 5-12 nm. UV-vis spectrophotometric measurement showed high transparency (nearly 80% in the wavelength range 550-900 nm) of the films with a direct allowed band gap lying in the range 2.64-3.25 eV. Particle sizes have also been calculated from the shift of band gap with respect to that of bulk value and were found to be in the range 3.3-6.44 nm. The high dielectric constant (lies in the range 120-250 at high frequency) of PVA/CdS nanocomposite compared to that of pure PVA (-28) has been observed. The dielectric constant decreases with increase of dispersibility of the CdS nanoparticles within PVA. The nanocrystalline PVA/CdS thin films have also showed field emission properties with a turn-on field of approximately 6.6 V/microm, whereas only PVA thin film and bulk CdS on PVA have shown no field emission.     

Surface-plasmon-enhanced photoluminescence of CdS nanoparticles with Au/SiO2 nanocomposites

To examine the effect of metal nanostructures on the photoluminescence of CdS nanoparticles, Au/SiO₂ nanocomposites were prepared with back-reflection geometry. The contribution from the prolonged optical-path lengths was excluded, and the luminescence enhancement was attributed only to surface-plasmon resonance. The optimum nanostructures for the PL enhancement were examined, and correlated with the wavelength of the surface-plasmon peak of the Au/SiO₂ nanocomposites and the PL emission peak of CdS nanoparticles.