单源前体合成水溶性的CdS和ZnS纳米晶

0引言量子点(QuantumDots)一般指半径小于或接近玻尔激子半径的半导体纳米晶颗粒。和有机染料分子相比,无机半导体纳米晶的带隙宽度可通过简单     

聚合物-二氧化硅复合基材中CdS纳米晶的合成

本文报道在Sol-gel基材中制备由聚合物稳定的CdS纳米晶的新方法， 即通过甲基丙烯酸镉与甲基丙烯酸羟乙酯共聚合合成了含有Cd 2+的聚合物微凝胶, 在聚合物微凝胶网络中原位聚合正硅酸乙酯形成聚合物互穿的Sol-gel复合基材. 再向该聚合物/二氧化硅复合基材中通入H2S气体得到CdS纳米晶. 在聚合物网络中原位聚合正硅酸乙酯可以降低纯二氧化硅材料的脆性; 另一方面, 二氧化硅可以作为增强剂增加聚合物材料的强度. 因此, 在我们合成的聚合物/二氧化硅复合基材中制备的CdS纳米晶将具有很好的应用前景.     

介观结构SiO2/CdO纳米复合物为前驱体原位水热合成半导体CdSe和CdS纳米晶

以高度有序的介观结构SiO₂/CdO纳米复合物为前驱体,在硒源或硫源存在的还原性条件下,利用原位水热反应,合成了介观结构SiO₂/CdSe及SiO₂/CdS纳米复合物,除去SiO₂后,得到半导体CdSe及CdS纳米晶.通过X射线衍射(XRD),高分辨率透射电镜(HRTEM),X射线能散射谱(EDX)及选区电子衍射(SAED)等手段对产物进行了组成和结构表征.结果表明,介观结构SiO₂主体材料在合成过程中起到了一定的形貌和尺寸限制作用,得到的CdSe和CdS均为直径在8 nm左右的类球形六方相纳米晶.     

Photoelectrochemical performance of dye and semiconductor sensitization on 1-D hollow hexagonal ZnO rods: A comparative study

One-dimensional hollow hexagonal ZnO rods (1-D HHZRs) were grown onto the SnO₂: F (FTO) coated glass substrates by using two-step deposition techniques. Initially, the ZnO seed layer was coated onto the FTO which was followed by hydrothermal route in order to grow 1-D HHZRs. These 1-D HHZRs were decorated with Eosin-Y dye and CdS semiconductor nanoparticles (NPs) by using a chemical routes like dip coating and successive ionic layer absorption reaction (SILAR) technique, respectively to improve its photoelectrochemical (PEC) performance. The structural, morphological, optical and electrochemical characterizations of the thin films were analyzed by various sophisticated instruments. X-ray diffraction (XRD) pattern corroborated the phase formation of ZnO and CdS with the hexagonal and cubic crystal structure, respectively. 1-D HHZRs films were obtained by scanning electron microscopy (SEM) with rod diameter of about 1.47 μm. Furthermore, SEM image clearly showed the CdS NPs covered 1-D HHZRs. The direct optical bandgap energy of the samples were estimated to be 3.28, 3.24 and 3.03 eV. CdS NPs-sensitized 1-D HHZRs samples showed hydrophilic nature for water contact angle, which is advantageous for the better improvement in the PEC performance as compared with pristine and dye-sensitized 1-D HHZRs.     

Growth and optical properties of wurtzite-type CdS nanocrystals

This paper reports wurtzite-type CdS nanostructures synthesized via a hydrothermal reaction route using dithiol glycol as the sulfur source. The reaction time was found to play an important role in the shape of the CdS nanocrystals: from dots to wires via an oriented attachment mechanism. This work has enabled us to generate nanostructures with controllable geometric shapes and structures and thus optical properties. The CdS nanostructures show a hexagonal wurtzite phase confirmed by X-ray diffraction and show no evidence for a mixed phase of cubic symmetry. The Raman peak position of the characteristic first-order longitudinal optical phonon mode does not change greatly, and the corresponding full width at half-maximum is found to decrease with the CdS shape, changing from nanoparticles to nanowires because of crystalline quality improvement. The photoluminescence measurements indicate tunable optical properties just through a change in the shape of the CdS nanocrystals; i.e., CdS nanoparticles show a band-edge emission at approximately 426 nm in wavelength, while the CdS nanowires show a band-edge emission at approximately 426 nm as well as a weaker trap-state green emission at approximately 530 nm in wavelength. These samples provide an opportunity for the study of the evolution of crystal growth and optical properties, with the shape of the nanocrystals varying from nearly spherical particles to wires.     

有机硫源溶剂热法合成CdS纳米晶体

以二硫化四甲基秋兰姆((TMTD)作为有机硫源,分别在苯、水-苯溶剂中于不同温度、不同时间溶剂热法合成了CdS纳米晶体。采用FE-SEM、XRD和FTIR对晶体的结构和成形机理进行了研究。结果表明,溶剂热温度比反应时间对晶体形貌的形成影响更大。CdS纳米晶体是立方与六角的混合晶型。此外,溶剂的种类也是影响CdS纳米晶体结构和成形的重要因素,并且对花形CdS纳米晶体进行了阴极发光(CL)光谱的研究。     

水热合成CdS纳米晶体的形貌控制研究

研究了水热合成CdS纳米晶体形貌的化学控制，选择不同的络合试剂为模板,研究其对水热合成CdS纳米晶体形貌的影响.实验发现若以络合试剂乙二胺、甲胺为模板时，产品CdS晶体的形貌分别为（20～30） nm×（200～600） nm和（40～50） nm×（200～600） nm尺寸的纳米棒;而以络合试剂吡啶、 氨为模板时，产品CdS晶体的形貌分别为平均尺寸约30 nm和20 nm的纳米颗粒.用XRD、TEM、XPS、PL和Raman光谱等技术对所得CdS纳米棒进行了表征.同时对水热合成CdS纳米晶体形貌的模板控制机制进行了探讨，提出了一种水热合成CdS纳米棒的络合物结构诱导生长机理.     

The influence of oxygen on the fluorescence enhancement of fatty-acid-capped CdS nanocrystals

CdS nanocrystals were synthesized in 1-octadecene (ODE) solution with oleic acid (OA) as a capping agent. Freshly prepared CdS nanocrystals showed a weak orangelike fluorescence due to defects on the particle surface. After several weeks' storage, the bulk fluorescence of CdS nanocrystals was dramatically enhanced, which gave the nanocrystals a blue or violet appearance. UV and photoluminescence (PL) measurements were employed to investigate this process. It has been found that the oxygen in the air played the most important role. The oxygen atoms could absorb on the surface of particles and a layer of oxide was gradually formed, which effectively passivated the surface of CdS nanocrystals. Interestingly, this oxidative process had no relation to UV illumination.     

CdS纳米晶与多肽分子相互作用研究

研究了半导体CdS纳米晶的表面功能化及荧光光谱特性, 并利用静电/配位自组装方法实现了多肽和CdS纳米晶的生物无机偶联, 研究了纳米晶多肽偶联体系的荧光光谱以及多肽与CdS纳米晶之间的相互作用. 结果表明: 含巯基多肽对CdS纳米晶表面形成完善包覆, 消除CdS纳米晶表面缺陷, 使CdS纳米晶荧光增强; 含端氨基多肽使CdS纳米晶荧光出现先升后降趋势; 其余不含巯基和氨基的多肽均猝灭CdS纳米晶荧光, 猝灭机制属于形成化合物所引起的静态猝灭, 它们的结合常数约为2×10⁴, 结合位点数约为0.87～1.00.     

Synthesis and controlling the morphology of CdS nanocrystals via hydrothermal microemulsions

Wurtzite CdS nanocrystals were synthesized via a hydrothermal microemulsion method. With the preaddition of increasing amounts of dodecanethiol, the resulting crystals changed from nanorods to pyramidal particles with decreasing sizes. The control effect of dodecanethiol was attributed to the competition process during the crystal growth and the relevant change in the film flexibility of inverse micelles. The effects of water content, ion concentration, and hydrothermal temperature on the crystal morphologies and size distributions were also investigated.     

Highly luminescent, stable, and water-soluble CdSe/CdS core-shell dendron nanocrystals with carboxylate anchoring groups

A dendron ligand with two carboxylate anchoring groups at its focal point and eight hydroxyl groups as its terminal groups was found to efficiently convert as-synthesized CdSe/CdS core-shell nanocrystals in toluene to water-soluble dendron-ligand stabilized nanocrystals (dendron nanocrystals). The resulting dendron nanocrystals retained 60% of the photoluminescence value of the original CdSe/CdS core-shell nanocrystals in toluene and were significantly brighter than the similar dendron nanocrystals with thiolate (deprotonated thiol group) as the anchoring group which retained just 10% of the photoluminescence value of the original CdSe/CdS core-shell nanocrystals in toluene. The carboxylate-based dendron nanocrystals survived UV irradiation in air for at least 13 days, about 9 times better than the thiolate-based dendron nanocrystals (35 h) and similar to that of the thiolate-based dendron-box stabilized CdSe/CdS core-shell nanocrystals (box nanocrystals). Upon UV irradiation, the dendron nanocrystals became even 2 times brighter than the original CdSe/CdS core-shell nanocrystals in toluene, and the UV-brightened PL can retain the brightness for at least several months. These stable and bright dendron nanocrystals were soluble in various aqueous media, including all common biological buffer solutions tested, for at least 1.5 years. In addition to their superior performance, the synthetic chemistry of carboxylate dendron ligands and the corresponding dendron nanocrystals is relatively simple and with high yield.     

Catalyst-assisted solution-liquid-solid synthesis of CdS/CdSe nanorod heterostructures

We report the synthesis and characterization of axial nanorod heterostructures composed of cadmium selenide (CdSe) and cadmium sulfide (CdS). The synthesis employs a solution-liquid-solid (SLS) mechanism with the assistance of bismuth nanocrystals adhered to a substrate (silicon or a III-V semiconductor). Transmission electron microscopy (TEM) and diffraction studies show that CdSe and CdS segments exhibit the wurtzite (hexagonal) crystal structure with <5% stacking faults. Both of these segments grow along the [002] direction with an epitaxial interface between them. Energy-dispersive X-ray (EDX) spectrometry using a high-resolution TEM operating in scanning mode confirms the alloy-free composition modulation in the nanorod heterostructures, showing that Se and S are localized in the CdSe and CdS portions of the nanorod heterostructures, respectively. This study demonstrates that SLS synthesis provides an alternate route to prepare axial nanorod heterostructures that have been difficult to generate using either vapor-liquid-solid growth or catalyst-free solution-phase synthesis.     

Synthesis of highly ordered mesoporous crystalline WS(2) and MoS(2) via a high-temperature reductive sulfuration route

A high-temperature reductive sulfuration method is demonstrated to synthesize highly ordered mesoporous metal sulfide crystallites by using mesoporous silica as hard templates. H2S gas is utilized as a sulfuration agent to in situ convert phosphotungstic acid H3PW12O40.6H2O to hexagonal WS2 crystallites in the silica nanochannels at 600 degrees C. Upon etching silica, mesoporous, layered WS2 nanocrystal arrays are produced with a yield as high as 96 wt %. XRD, nitrogen sorption, SEM, and TEM results reveal that the WS2 products replicated from the mesoporous silica SBA-15 hard template possess highly ordered hexagonal mesostructure (space group, p6mm) and rodlike morphology, analogous to the mother template. The S-W-S trilayers of the WS2 nanocrystals are partially oriented, parallel to the mesochannels of the SBA-15 template. This orientation is related with the reduction of the high-energy layer edges in layered metal dichalcogenides and the confinement in anisotropic nanochannels. The mesostructure can be 3-D cubic bicontinuous if KIT-6 (Iad) is used as a hard template. Mesoporous WS2 replicas have large surface areas (105-120 m2/g), pore volumes ( approximately 0.20 cm3/g), and narrow pore size distributions ( approximately 4.8 nm). By one-step nanocasting with the H3PMo12O40.6H2O (PMA) precursor into the mesochannels of SBA-15 or KIT-6 hard template, highly ordered mesoporous MoS2 layered crystallites with the 2-D hexagonal (p6mm) and 3-D bicontinuous cubic (Iad) structures can also be prepared via this high-temperature reductive sulfuration route. When the loading amount of PMA precursor is low, multiwalled MoS2 nanotubes with 5-7 nm in diameter can be obtained. The high-temperature reductive sulfuration method is a general strategy and can be extended to synthesize mesoporous CdS crystals and other metal sulfides.     

Synthesis and Characterization of CdSe Nanocrystals Capped by CdS

CdSe semiconductor nanocrystals capped by CdS were synthesized in the aqueous solution with 2-mercaptoethanol as the stabilizer. The CdS capping with a higher band-gap than that of the core crystallite has successfully eliminated the surface traps. Optical absorption and fluorescence emission spectra were used to probe the effect of CdS passivation on the electronic structure of the nanocrystals. The composite CdSe/CdS nanocrystals exhibit strong, narrow(FWHM≤40 nm) and stable band-edge photoluminescence. X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the composite nanocrystals and determine their average size, size distribution, shape, internal structure and elemental composition.     

Synthesis of nanocrystalline CdS from cadmium(II) complex of S-benzyl dithiocarbazate as a precursor

The single X-ray crystal structure of the cadmium(II)–S-benzyl dithiocarbazate (SBDTC) complex, [Cd(SBDTC)Cl₂]₂, is reported. The compound has been found to be an effective single-source precursor for the preparation of CdS nanocrystals (NCs) via solvothermal method. CdS NCs including spheres and rods were prepared at a relatively low temperature by thermolysis of the precursor using chelating solvent like ethylene glycol (EG), ethylenediamine (EN), hydrazine hydrate (HH) or in a mixture of EG and EN. The influence of solvent, temperature and reaction time was investigated on the size and morphology of the NCs. Use of EG afforded spherical CdS NCs while EN uniquely yielded rod-shaped NCs, and mixture of spheres and rods are obtained from the mixture of EN and EG with a ratio 0.2 (v/v: EN/EG). UV–visible spectroscopy established pronounced quantum confinement with enhanced band gap and XRD analyses revealed hexagonal crystal phase for so obtained CdS NCs. The NCs were also characterized by transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), energy-dispersive X-ray spectroscopy (EDS) and FTIR. The possible formation mechanism for the anisotropic growth of NCs was also discussed.     

Preparation and application of L-cysteine-modified CdSe/CdS core/shell nanocrystals as a novel fluorescence probe for detection of nucleic acid

The water-soluble L-cysteine-modified CdSe/CdS core/shell nanocrystals (expressed as CdSe/CdS/Cys nanocrystals) have been synthesized in aqueous by using L-cysteine as stabilizer. The size, shape, component and spectral property of CdSe/CdS/Cys nanocrystals were characterized by high-resolution transmission electron microscope (HRTEM), energy dispersive X-ray fluorescence (EDX), infrared spectrum (IR) and photoluminescence (PL). The results showed that the spherical CdSe/CdS/Cys nanocrystals with an average diameter of 2.3 nm have favorable fluorescent property, theirs photostability and fluorescence intensity are enhanced greatly after overcoating with CdS. The cysteine modified on the surface of core/shell CdSe/CdS nanocrystals renders the nanocrystals water-soluble and biocompatible. Based on the fluorescence quenching of the nanocrystals in the presence of calf thymus deoxyribonucleic acid (ct-DNA), a fluorescence quenching method has been developed for the determination of ct-DNA by using the nanocrystals as a novel fluorescence probe. The pH value of the system was selected at pH 7.4, with excitation and emission wavelength at 380 and 522 nm, respectively. Under the optimal conditions, the fluorescence quenching intensity of the system is linear with the concentration of ct-DNA in the range of 0.1-3.5 microg/mL (r=0.9987). The detection limit is 0.06 microg/mL. And two synthetic samples were analyzed satisfactorily.     

Polyacrylic acid coating of highly luminescent CdS nanocrystals for biological labeling applications

Surface coating of highly luminescent CdS nanocrystals by polyacrylic acid was demonstrated. The method proceeded in 2 steps, (i) modification of the CdS surface by alkyl molecules and (ii) polyacrylic acid coating of the surface modified CdS. Attachment of alkyl ammonium on the CdS surface induced a phase transfer reaction from an aqueous to a non-polar phase with a yield of approximately 100%. Investigating alkyl molecules with various functional groups revealed that the alkyl molecules, possessing the cation moiety, such as amine or ammonium salt, can electrostatically interact with the CdS surface. The PL of the uncoated nanocrystals was almost entirely quenched in the pH range of approximately 7, while the polyacrylic acid coated nanocrystals exhibited moderate PL intensity. This PL intensity was preserved for at least several days, facilitating biological labeling application under a neutral condition.     

Cadmium sulfide nanocrystals via two-step hydrothermal process in microemulsions: synthesis and characterization

CdS nanocrystals with an average diameter of 16 nm were synthesized in the CTAB/n-C(5)H(11)OH/n-C(6)H(14)/water quaternary microemulsions by a two-step hydrothermal process at 90 and 130 degrees C. The reaction of carbamide and carbon disulfide was employed as the sulfur source for the preparation of CdS nanocrystals. The resulting crystals were characterized with powder X-ray diffraction, transmission electron microscopy, UV-vis absorption spectroscopy, and photoluminescence spectroscopy. A unique core/shell structure of CdS nanocrystals was suggested for the explanation of the interesting phenomenon.     

CdS/石墨烯纳米复合物的可见光催化效率和抗光腐蚀行为

制备了一系列CdS纳米晶/石墨烯(CdS/GR)复合物,并在可见光照条件下评价了其光催化降解亚甲基蓝的光催化效率和抗光腐蚀行为. 研究表明,石墨烯的引入加速了CdS纳米晶(NCs)光生电子的迁移速率,抑制了其光生电子-空穴的复合,有效改善了其光催化降解有机污染物的性能. CdS/GR复合物中的石墨烯含量显著影响其光催化效率,其中石墨烯含量为4.6%的光催化剂效率最高,其光电流是CdS NCs的2.3倍. 利用光电化学和X射线衍射技术进一步证实,石墨烯的引入抑制了CdS NCs光腐蚀的发生,提高了CdS/GR复合物的光催化稳定性.     

Synthesis of beltlike CdS nanocrystals via solvothermal route

CdS nanocrystals with a beltlike morphology were prepared via a low-temperature solvothermal route in ethylenediamine. The obtained nanocrystals were characterized by X-ray powder diffraction, transmission electron microscopic, ultraviolet-visible and fluorescence spectroscopy. In the mixed solvents of ethylenediamine and distilled water, CdS nanocrystals with various morphologies were obtained with the change of the volume ratio of the two constituents.