ZnSe/5B2O3-95SiO2纳米复合材料的制备及性能表征

采用溶胶凝胶工艺在室温合成合有Zn、Se成分和玻璃相成分的均匀透明凝胶，并通过CO还原气氛热处理，在凝胶玻璃中原位生长出ZnSe纳米晶体．利用BET比表面积、透射电镜、吸收光谱、荧光光谱等分析手段对ZnSe纳米复合材料的组成结构及量子尺寸效应影响下的光学性能进行了表征，结果表明：5B2O3—95SiO2凝胶玻璃的多孔结构可有效地分散ZnSe纳米晶粒；纳米复合材料中ZnSe纳米晶粒呈球形，粒径约为3．5nm；吸收光谱中，ZnSe纳米复合材料的吸收边相对于ZnSe体材料发生蓝移，随着ZnSe在凝胶玻璃中摩尔分数的增大，蓝移量减小，相应ZnSe纳米晶粒尺寸增大；在荧光光谱中，500nm附近的发光带是凝胶玻璃中的ZnSe纳米晶体表面态复合和缺陷发光，当ZnSe的摩尔分数达到0．07时，观测到了浓度的荧光淬灭现象．     

ZnS：Tb／SiO2核壳结构纳米晶的光学性质

用微乳液法合成了ZnS：Tb／SiO2核壳结构纳米晶,并通过X射线粉末衍射（XRD）、透射电子显微镜（TEM）、荧光光谱等手段对产物的结构、尺寸、形貌、荧光特性进行了表征。结果表明,ZnS：Tb纳米晶的粒径为3nm,ZnS：Tb／SiO2核壳结构纳米晶的粒径为5nm左右,这样就得出壳的厚度约为1nm。在ZnS：Tb／SiO2核壳结构纳米晶的发射光谱上可以观察到有5个发射峰为460、489、544、584和620nm,分别对应ZnS基质的发光和Tb^3＋离子的^5D4→^7F6、^5D4→^7F5、^5D4→^7F4、^5D4→^7F3跃迁。     

<Emphasis Type="Italic">In-situ</Emphasis> growth and spectrum characterization of ZnSe nanocrystals in silica gel-glasses

ZnSe nanocrystals were in-situ grown in silica gel-glasses by using sol-gel process and the reductive thermal treatment. The transparent, homogeneous ZnSe/SiO2 nanocomposites with the yellow color were first obtained. We used X-ray diffraction pattern (XRD), UV-VIS optical absorption and Raman scattering to characterize the spectrum properties of ZnSe nanocrystals. The broadening of XRD peaks, the blueshift of interband optical absorption edge and the change of Raman spectrum were observed. From these experimental results, we theoretically calculated the size of ZnSe nanocrystals. The results of XRD, optical absorption and Raman spectra were approximately consistent, with the mean diameter of about 4.6 nm. The discrepancies from different methods were discussed.     

ZnSe/SiO2复合材料光学吸收特性的研究

采用溶胶-凝胶原位析晶法和高温还原热处理工艺制备了ZnSe/SiO2纳米复合材料.通过吸收光谱和Z-Scan技术对材料的光学吸收特性进行了表征.在吸收光谱中,不同ZnSe摩尔分数的样品的吸收边相对于ZnSe体材料发生了不同程度的蓝移,蓝移量与复合材料中ZnSe纳米晶粒的尺寸有关,根据量子尺寸效应估算了复合材料中ZnSe纳米晶粒的平均尺寸大约为3~4 nm.利用Z-Scan技术测定了ZnSe摩尔分数为0.01和0.03的ZnSe/SiO2纳米复合材料的双光子吸收系数.ZnSe/SiO2纳米复合材料在不同强度的入射光的激发下其出射光强度与入射光强度之间的关系呈现光学限幅特征,ZnSe摩尔分数为0.01的样品的限幅阈值为5 962 GW/m2,嵌位输出值约为4 800 GW/m2,限幅的破坏阈值为12 400 GW/m2.     

微乳液法制备CdSe/CdS核壳纳米粒子及表征

研究了SDS/异戊醇/环己烷/水所组成的四元微乳体系,并将该体系用于CdSe及CdSe/CdS(核壳结构)纳米粒子的制备.在反应过程中以紫外可见吸收光谱考察了不同反应条件下粒子的成核与生长情况.实验得到的CdSe微乳液非常稳定,室温下放置数月仍未见有沉淀生成.使用荧光分光光度计和高分辨透射电镜对粒子进行表征,所得CdSe/CdS纳米粒子粒径为5 nm左右,粒径均一且具有较高的荧光强度.     

硫代水杨酸修饰的CdSe/ZnS纳米晶的合成及应用研究

以硫代水杨酸作为修饰剂,合成了水溶性的CdSe/ZnS纳米晶.合成最佳条件为:CdSe与包覆层ZnS摩尔比为1∶8,pH值为11.00、回流时间为45 min、回流温度为80℃.从透射电子显微镜看到该纳米晶外观是独特的树枝形;紫外吸收光谱和荧光光谱表明CdSe/ZnS纳米晶比单一的CdSe纳米晶具有更好的发光特性;荧光强度在3个月内变化不大.在最佳实验条件下,将合成的CdSe/ZnS与牛血清白蛋白(BSA)作用,测得体系相对荧光强度与BSA质量浓度呈线性关系,线性响应范围为2.56～15.0 mg/L,线性方程为ΔF=101.17C-11.29(C为BSA质量浓度,单位是mg/L),R=0.996 2,检出限为0.64 mg/L.     

Cd类核壳型纳米粒子的制备及表征

以巯基乙酸为稳定剂,在水溶液中合成CdSe和CdTe及CdSexTe1-x核纳米粒子,用ZnS纳米粒子包覆核纳米粒子,制备出水溶性CdSe/ZnS和CdTe/ZnS及CdSexTe1-x/ZnS核壳型纳米粒子.用荧光光谱、高倍透射电镜等技术对核纳米粒子及核壳纳米粒子进行表征,以荧光光谱研究了时间、稳定剂用量等因素对核壳型纳米粒子光谱特性的影响.     

Doping semiconductor nanocrystals

Doping--the intentional introduction of impurities into a material--is fundamental to controlling the properties of bulk semiconductors. This has stimulated similar efforts to dope semiconductor nanocrystals. Despite some successes, many of these efforts have failed, for reasons that remain unclear. For example, Mn can be incorporated into nanocrystals of CdS and ZnSe (refs 7-9), but not into CdSe (ref. 12)--despite comparable bulk solubilities of near 50 per cent. These difficulties, which have hindered development of new nanocrystalline materials, are often attributed to 'self-purification', an allegedly intrinsic mechanism whereby impurities are expelled. Here we show instead that the underlying mechanism that controls doping is the initial adsorption of impurities on the nanocrystal surface during growth. We find that adsorption--and therefore doping efficiency--is determined by three main factors: surface morphology, nanocrystal shape, and surfactants in the growth solution. Calculated Mn adsorption energies and equilibrium shapes for several nanocrystals lead to specific doping predictions. These are confirmed by measuring how the Mn concentration in ZnSe varies with nanocrystal size and shape. Finally, we use our predictions to incorporate Mn into previously undopable CdSe nanocrystals. This success establishes that earlier difficulties with doping are not intrinsic, and suggests that a variety of doped nanocrystals--for applications from solar cells to spintronics--can be anticipated.     

CaGd3F11:Eu3+超小纳米晶的制备及其发光性质研究

以无水氯化钙、稀土硝酸盐、正辛醇为原料,以正辛胺和油酸为表面活性剂,通过控制不同的反应条件,采用溶剂热法制备出形貌均匀的CaGd_3F_(11):Eu~(3+)纳米发光材料.用X射线衍射(XRD)、透射电子显微镜(TEM)和荧光分光光度计对合成的纳米晶的粒径、形貌和光学性质进行了表征.结果表明CaGd3F11纳米晶的结晶度良好且尺寸均匀(约5nm),其作为基质材料,掺杂Eu3+表现出很强的荧光发射.     

Synthesis of Water-Dispersed Thioglycolic Acid-Capped ZnSe Quantum Dots in Aqueous Media

Water-dispersible ZnSe quantum dots (ZnSe QDs) were prepared in aqueous media and characterized by ultraviolet-visible absorption, fluorescence emission spectroscopy, X-ray powder diffraction, transmission electron microscopy, energydispersive spectroscopy, and inductively coupled plasma atomic emission spectroscopy. The influences of various experimental variables on the photoluminescence properties of ZnSe QDs were investigated. The results showed that the average diameter of these nanocrystals was 4 nm with narrow size distribution. The optimized conditions were as follows: pH value of 9.5, Zn/NaHSe molar ratio of 10:1, Zn/TGA molar ratio of 1:3, heating time of 1 h, and irradiation time of 19 h. Under optimized conditions, the photoluminescence quantum yield of ZnSe QDs in aqueous solution reached 20%.     

水相合成ZnSe量子点光诱导荧光增敏的pH效应

在水相中以巯基乙酸(TGA)为稳定剂,通过Zn2 离子和NaHSe反应合成了ZnSe量子点(ZnSe QDs).新合成的ZnSe QDs几乎无荧光,经紫外光照处理后呈现强的带边发射,量子产率显著提高.由于紫外光照可以诱导键合在ZnSeQDs表面的TGA发生光解产生S2-离子,因而与溶液中过量的Zn2 离子及TGA共同作用,在ZnSe QDs表面上形成ZnS壳层,电镜实验结果直接揭示了紫外光照处理后ZnSe QDs粒径的显著增加.研究发现,pH值的变化直接影响ZnSeQDs表面TGA的光催化光解,导致了ZnSe QDs的光诱导增敏作用对溶液pH值的依赖关系.在碱性条件下(pH 8~12),光诱导增敏效率随着溶液pH值的提高而增强,同时ZnSe QDs对光的稳定性也随之增强.     

Bi2O3/Cu-O-Cr核壳结构纳米复合物的合成

采用沉淀法制得球形单分散Bi2O3纳米粒子；通过共沉淀法制备球形单分散Bi2O3／Cu-O-Cr核壳结构复合纳米材料,通过X射线衍射、透射电镜、能谱分析和红外光谱等技术表征所合成材料的成分组成、晶体结构、微现形貌以及颗粒尺寸，并对Bi2Oa／Cu-O-Cr核壳结构的复合纳米粒子的形成机理进行研究。研究结果表明：在包覆前先对Bi2O3粒子进行表面铵离子（NH4^＋）功能化是形成均匀核壳纳米结构的关键；铜铬包覆层以氨配合物的形式包在Bi2O3粒子表面，形成棱壳结构的复合粒子，复合粒子的平均粒度为78nm．核厚为60nm．     

不同溶剂中制备单分散量子点

选用比较缓和反应条件,用无毒、价廉、稳定性好的无机化合物作为反应前驱体制备半导体量子点材料．通过选择不同的反应溶剂,可以得到粒径大小不同从而发光波长可“调谐”的一系列CdSe量子点材料．用紫外吸收光谱（UV—Vis）,荧光发射光谱（PL）跟踪了反应的过程,用X射线衍射（XRD）和透射电镜（TEM）对得到的量子点材料的结构进行了表征．对量子点材料在有机溶剂和水溶液中的转相进行了研究,为量子点与生物分子的连接,进而在生物标记方面的应用提供材料基础．该方法是对传统高温条件下有机金属化合物前驱体分解制备方法的补充,是一种环境友好的半导体量子点材料的制备方法．     

碲化锌修饰掺铜硒化锌量子点的合成

以巯基丙酸（mercaptopropionic acid,MPA）作为稳定剂,在水相中合成Cu离子掺杂的ZnSe量子点（quantum dots,QDs）,并以ZnTe修饰其表面（ZnSe:Cu/ZnTe QDs）.采用X射线衍射（X-ray diffraction,XRD）、高分辨透视电子显微镜（high resolution transmission electronic microscopy,HRTEM）、紫外可见吸收光谱（ultraviolent-visible spectroscopy,UV-VIS）和光致发光(photoluminescence,PL)荧光光度计对其结构、相貌和光学特性进行表征.结果表明,合成所得荧光量子点的大小为4～6 nm;当激发波长325 nm时,荧光发射峰约为510 nm;经160 ℃热处理后,荧光发射峰会红移至540 nm左右,初步说明ZnTe的修饰会改变ZnSe:Cu量子点荧光发射峰的位置.     

金/二氧化硅中空核壳纳米球的制备与表征

采用水热反应法和正硅酸乙酯水解法制备出核壳结构的Au/C纳米球颗粒以及夹层结构的Au/C/SiO<,2>纳米球颗粒,在空气中锻烧将Au/C/SiO<,2>夹层结构中的碳层除去,得到内部带有可移动纳米金核、壳层厚度约为20 nM的中空Au/SiO<,2>纳米球颗粒.用透射电子显微镜对所制得的纳米微球的形貌进行表征,并用红...     

核壳结构Bi/WO_x复合粉体材料的可控合成

以α-Bi2O3和WO3为原料,采用高能球磨法制备核壳结构Bi/WOx复合粉体材料.当添加0.1 mL无水乙醇,球磨15h时,得到的产物纯度较高,粒径分布为50¹20nm.通过XRD分析可知,所得Bi/WOx复合粉体材料为非晶态氧化钨包裹六方相晶态Bi的核壳结构,其中Bi晶核尺寸约为20120nm.通过XRD分析可知,所得Bi/WOx复合粉体材料为非晶态氧化钨包裹六方相晶态Bi的核壳结构,其中Bi晶核尺寸约为20⁹0nm,壳层厚度约为30nm.     

Te掺杂ZnSe/[(CdSe)_l(ZnSe)_3]_m超晶格荧光光谱

对垒区Ｔｅ掺杂浓度不同的ＺｎＳｅ／［（ＣｄＳｅ）１（ＺｎＳｅ）３］ｍ短周期超晶格量子阱的稳态和瞬态荧光进行了实验研究，通过不同激发强度下逐级饱和过程测得ＺｎＳｅ垒区自由激子寿命为３５ｐｓ，［（ＣｄＳｅ）１（ＺｎＳｅ）３］７阱区自由激子寿命为１７７ｐｓ，束缚在不同ｎ值的Ｔｅｎ束缚激子的复合寿命为０．５～１０ｎｓ．揭示了Ｔｅ掺杂浓度对能量传递、荧光波长和荧光寿命的灵敏的影响及其规律．     

基于BaLuF5 颐Yb3+ ,Er3+ 纳米晶掺杂的聚合物光波导放大器

为提高聚合物光波导放大器的增益性能, 利用高温法合成了BaLuF5 颐Yb3+ ,Er3+纳米晶, 并分别对纳米晶的形貌、晶体结构和近红外发射特性进行了表征。测试结果表明, 纳米晶平均粒径为13 nm, 并在1 530 nm 处具有较强的发射, 荧光半高宽为50 nm。将合成的纳米晶掺杂入SU-8 聚合物作为光波导放大器的芯层材料, 使
用光刻显影等工艺, 在表面长有二氧化硅的硅衬底上制备出了聚合物光波导放大器。当980 nm 波长泵浦光功率为280 mW、信号光波长为1 530 nm 且功率为0. 1 mW 时, 在长度为1. 1 cm 的光波导放大器中, 获得了3. 95 dB的相对增益。     

Single-exciton optical gain in semiconductor nanocrystals

Nanocrystal quantum dots have favourable light-emitting properties. They show photoluminescence with high quantum yields, and their emission colours depend on the nanocrystal size--owing to the quantum-confinement effect--and are therefore tunable. However, nanocrystals are difficult to use in optical amplification and lasing. Because of an almost exact balance between absorption and stimulated emission in nanoparticles excited with single electron-hole pairs (excitons), optical gain can only occur in nanocrystals that contain at least two excitons. A complication associated with this multiexcitonic nature of light amplification is fast optical-gain decay induced by non-radiative Auger recombination, a process in which one exciton recombines by transferring its energy to another. Here we demonstrate a practical approach for obtaining optical gain in the single-exciton regime that eliminates the problem of Auger decay. Specifically, we develop core/shell hetero-nanocrystals engineered in such a way as to spatially separate electrons and holes between the core and the shell (type-II heterostructures). The resulting imbalance between negative and positive charges produces a strong local electric field, which induces a giant ( approximately 100 meV or greater) transient Stark shift of the absorption spectrum with respect to the luminescence line of singly excited nanocrystals. This effect breaks the exact balance between absorption and stimulated emission, and allows us to demonstrate optical amplification due to single excitons.     

CdSe/SiO2核壳荧光纳米颗粒的制备与表征

以巯基丁二酸为稳定剂,二氧化硒为硒源,合成高质量水溶性CdSe量子点.采用反相微乳液技术,制备以CdSe量子点为核的SiO₂荧光纳米颗粒.在pH值为11.0的碱性条件下,当n_Cd∶n_Se∶n_MSA=1∶0.2∶1.4时,在540 min时间内,可获得荧光发射峰在531~554 nm范围内连续可调CdSe量子点,最高荧光量子产率值可达14.7%.分别用紫外-可见光谱、荧光光谱、X射线粉末衍射和透射电镜等对CdSe量子点进行表征,用荧光光谱、透射电镜、红外光谱等对CdSe/SiO₂荧光纳米颗粒的性能进行表征.