A facile "dispersion-decomposition" route to metal sulfide nanocrystals

In this paper, we demonstrate a simple and general "dispersion-decomposition" approach to the synthesis of metal sulfide nanocrystals with the assistance of alkylthiol. This is a direct heating process without precursor injection. By using inorganic metal salts and alkylthiol as the raw materials, high-quality Ag(2)S, Cu(2)S, PbS, Ni(3)S(4), CdS, and ZnS nanocrystals were successfully synthesized. The mechanism study shows that the reaction undergoes two steps. A key intermediate compound, metal thiolate, is generated first. It melts and disperses into the solvent at a relatively low temperature, and then it decomposes into metal sulfide as a single precursor upon heating. This method avoids using toxic phosphine agent and injection during the reaction process. The size and shape of the nanocrystal can be also controlled by the concentration of the reactant and ligands. Furthermore, the optical properties and assembly of the nanocrystals have also been studied. This report provides a facile, direct-heating "dispersion-decomposition" approach to synthesize metal sulfides nanocrystals that has potential for future large-scale synthesis.     

Nickel sulfide and copper sulfide nanocrystal synthesis and polymorphism

Nickel sulfide and copper sulfide nanocrystals were synthesized by adding elemental sulfur to either dichlorobenzene-solvated (copper sulfide) or oleylamine-solvated metal(II) precursors (nickel sulfide) at relatively high temperature to produce the metal sulfide. Nickel sulfide nanocrystals are cubic Ni(3)S(4) (polydymite) with irregular prismatic shapes, forming by a two-step reduction-sulfidation mechanism where Ni(II) reduces to Ni metal before sulfidation to Ni(3)S(4). Despite extensive efforts to optimize the Ni(3)S(4) nanocrystal size and shape distributions, polydisperse nanocrystals are produced. In contrast, copper sulfide nanocrystals can be obtained with narrow size and shape distributions. The copper sulfide stoichiometry depended on the Cu:S mole ratio used in the reaction: Cu:S mole ratios of 1:2 and 2:1 gave CuS (covellite) and Cu(1.8)S (digenite), respectively. CuS nanocrystals formed as hexagonal disks that assemble into stacked ribbons when cast from solution onto a substrate. CuS, Cu(1.8)S, and Ni(3)S(4) differ from the Cu(2)S and NiS nanocrystals obtained by solventless decomposition of metal thiolate single source precursors, in terms of stoichiometry for copper sulfide, and both stoichiometry and morphology for nickel sulfide [Ghezelbash, A.; Sigman, M. B., Jr.; Korgel, B. A. Nano Lett. 2004, 4, 537-542. Sigman, M. B. Ghezelbash, A.; Hanrath, T.; Saunders, A. E.; Lee, F.; Korgel, B. A. J. Am. Chem. Soc. 2003, 125, 16050-16057].     

热解单源前驱体方法可控制备纳米金属硫化物

本文简要综述了本研究组近年来在利用热解单源前驱体合成方法制备纳米金属硫化物方面的相关工作．通过采用不同的反应前驱体,改变反应时间、反应温度,选择不同的表面配体分子及反应溶剂等手段实现了对纳米金属硫化物形貌、尺寸、组成和晶相的精确调控．除了对合成方法和过程进行介绍外,本文还简要讨论了具有特定形貌的金属硫化物的形成机理,并对几类典型硫化物的应用研究进行了总结．     

Shape-controlled synthesis of zinc oxide: a simple method for the preparation of metal oxide nanocrystals in non-aqueous medium

A general and facile approach has been developed to prepare various metal oxide nanocrystals from commercially available metal acetate precursors using an amine-mediated reaction. The influence of temperature and capping agents on the yield and final morphology of the metal oxides nanocrystals was investigated. The approach was applied in the synthesis of shape-controlled ZnO nanocrystals. ZnO nanowires, nanorods, bullets and triangular nanocrystals were successfully prepared by tuning the molar ratio between amine to zinc acetate precursor. On the basis of FTIR and NMR spectroscopic studies, we propose that the amine could mediate the breakdown of the metal acetates through a nucleophilic attack mechanism. The results suggest that amine can play dual role as both the attacking agent and capping agent in this new methodology.     

Using a precursor in lamellar structure for the synthesis of uniform ZnS nanocrystals

Uniform ZnS nanocrystals of about 15?nm were prepared through a low temperature hydrothermal approach by treating Zn-PhPO nanosheets with Na₂S aqueous solution. Both the precursor and the final product were studied by the means of X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photo-luminescent spectrum of the synthesized ZnS nanocrystals showed their good crystalline nature. Based on this study, the precursor structure-controlling effect was discussed, and in addition, the relevant factors possibly affecting the particle formation and the growth possessed were applied in the discussion to interpret the transformation mechanism. Further research showed that both the structure characters of the precursors and the mass transportation which occurred during the synthesis greatly affected the morphology and organization state of the final products. This research may provide some facts on the structure-controlling approaches along with a general method for the preparation of uniform sulfide nanocrystals.     

Synthesis and characterization of sulfide and selenide colloidal semiconductor nanocrystals

In this paper, we demonstrate the synthesis of sulfide and selenide nanocrystals in a water-ethanol mixed solution system. This synthetic way was based on the direct reactions between metal ions and S(2-)/Se. Linoleic acid was adopted to protect the nanocrystals from agglomeration. Without involving extreme experimental conditions, this less toxic synthetic route can be expected to bring more opportunities to nanocrystal-related research and application fields.     

Synthesis, Characterization, and Reactivity of Group 12 Metal Thiocarboxylates, M(SOCR)(2)Lut(2) [M = Cd, Zn; R = CH(3), C(CH(3))(3); Lut = 3,5-Dimethylpyridine (Lutidine)

A series of group 12 metal thiocarboxylate species, M(SOCR)(2)Lut(2) [M = Cd, Zn; R = CH(3), C(CH(3))(3); Lut = 3,5-dimethylpyridine (lutidine)], were synthesized to investigate their potential to act as precursors for the formation of metal sulfide materials. These species were expected to undergo thiocarboxylic anhydride elimination to give stoichiometric metal sulfides and remove the organic supporting ligands cleanly. These species were characterized by (1)H, (13)C, and (where appropriate) (113)Cd NMR spectroscopies, TGA, elemental analysis, and single-crystal X-ray diffraction. The spectroscopic and analytical data were consistent with the formulas identified above, and in the solid state the compounds are monomeric with approximate tetrahedral metal coordination environments and monodentate S-bond thiocarboxylate ligands. Crystal data for Cd(SOCCH(3))(2)Lut(2): crystallized in the triclinic space group P&onemacr;, with a = 8.267(1) ?, b = 9.467(1) ?, c = 14.087(1) ?, alpha = 94.04(1) degrees, beta = 91.49(1) degrees, gamma = 104.03(1) degrees, and Z = 2. Thermal decomposition of these compounds in the solid state or in solution resulted in formation of the corresponding metal sulfide at low temperatures, as seen by powder X-ray diffraction. Evidence for thiocarboxylic anhydride elimination was documented by NMR in solution phase reactions. The effects on thiocarboxylic anhydride elimination, resulting from varying M, R, or solvent media, were examined by heating NMR tube solutions of M(SOCR)(2)Lut(2) in pyridine or toluene. Heating toluene or pyridine solutions of Cd(SOCCH(3))(2)Lut(2) resulted in formation of nanocrystalline, sphalerite CdS, as determined by X-ray diffraction and TEM. These preliminary reactivity studies have revealed the great potential of this highly tailorable chemical system as precursors to group 12 metal sulfido species.     

5-(S)-烷氧基-3，4-二卤-2(5H)-呋喃酮在二甲基甲酰胺中的Michael加成-消除反应

5-羟基 - 2 (5H) -呋喃酮是一些具有生理活性天然产物的重要结构组份 [1] ,γ-内酯类的结构片段在一些抗病毒药物或前体结构中也常出现 ,由于内酯环的立体构型与药物的生物活性密切相关 ,因此它的合成具有十分重要的价值[2 ] .近年来利用天然手性助剂薄菏醇和冰片等的手性 5-烷氧基 - 2 (5H) -呋喃酮合成天然产物已引起人们的广泛关注 [1,3～ 13] .我们在研究手性 5-烷氧基 - 3,4-二卤 - 2 (5H) -呋喃酮 (4a_ 4 d)与 Wittig- Horner试剂 (O,O-二乙氧基丙酮基膦酸二乙酯 ) (5)的反应时 ,当以 DMF为溶剂 ,金属钠为催化剂时 ,并未得到目标…     

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.     

Thiolate‐Mediated Photoinduced Synthesis of Ultrafine Ag2S Quantum Dots from Silver Nanoparticles

Photoinduced syntheses offer significant advantages over conventional thermal strategies, including improved control over reaction kinetics and low synthesis temperatures, affording nanoparticles with nontrivial and thermodynamically unstable structures. However, the photoinduced syntheses of non‐metallic nanocrystalline products (such as metal sulfides) have not yet been reported. Herein, we demonstrate the first photoinduced synthesis of ultrafine (sub‐2 nm) Ag₂S quantum dots (QDs) from Ag nanoparticles at 10 °C. By thorough investigation of the mechanism for the transformation, a fundamental link was established between the intrinsic structures of the molecular intermediates and the final Ag₂S products. Our results confirm the viability of low‐temperature photochemical approaches in metal sulfide synthesis, and demonstrate a new rule which could be followed in it.     

Sulfidation of rock-salt-type transition metal oxide nanoparticles as an example of a solid state reaction in colloidal nanoparticles

The sulfidation of colloidal rock-salt-type MO (M = Fe, Mn and Co) nanocrystals was performed in organic solvents using dissolved elemental sulfur at moderate temperatures. The vacancy defects in these rock-salt-type structures clearly promote complete oxide-sulfide conversion. The conversion products were hollow metal sulfide (pyrrhotite (Fe(1-x)S), Co(1-x)S and α-MnS) nanoparticles. These conversions by sulfidation proceed rapidly, making difficult the isolation of intermediates. The sulfidation intermediates, when the supply of sulfur was insufficient, had interesting structures, in which the metal oxide cores were surrounded by metal sulfide shells or had surfaces that were decorated with metal sulfide islands. Based on the above results, a mechanism of surface nucleation, shell formation, and void formation by diffusion processes is proposed.     

一种新型纺锤状α-Fe_2O_3纳米晶的合成、表征及其表面性能(英文)

合成了一种新型的具有单晶结构的α-Fe2O3纳米晶(NFO-1).在我们的合成方法中,样品的形貌和结构在低反应浓度体系中运用无机盐和有机模板进行双重调控,同时用溶剂挥发诱导自组装(EISA)来加速反应和在不改变形貌结构的前提下获得高产率样品.所得α-Fe2O3纳米晶的形貌和结构对其表面修饰功能有明显的影响,NFO-1因其特殊的纺锤状形貌而与表面功能试剂(多巴胺)之间的化学作用有明显的增强.并且,本文所描述的合成方法同样适用于其他过渡金属氧化物纳米单晶的合成.我们预期,这种方法可为新型纳米材料的合成提供新的途径.     

异三核过渡金属配合物〔Fe_2~Ⅲ M~ⅡO(OOCC_2H_5)_6L_3〕(M=Co,Ni,Mn;L=C_5 H_5N,H_2O)溶液行为的NMR和UV谱表征

在合成和表征了一系列新的异核异价三核过渡金属羧酸配合物〔Fe2 Ⅲ MⅡ O (OOCC2 H5 ) 6 L3〕 (M =Co ,Ni,Mn ;L =C5 H5 N ,H2 O)的基础上 ,利用多种NMR技术并结合UV谱研究了这些配合物在不同溶剂介质和温度下的谱学特征和动力学性质。利用谱峰积分比例、线宽、相同骨架分子的配体取代和纵向弛豫时间对1 HNMR谱进行了归属。实验结果表明 :这类配合物的金属离子间通过中心氧桥存在一定的反铁磁相互作用 ,从而在整体上削弱了顺磁性的影响 ,仍能观察到NMR谱。实验还发现这些配合物在CD3CN和DMSO溶剂中的结构与晶体结构一致 ,而在水中则分解为金属离子、羧酸盐和吡啶。这些结果有助于指导类似配合物的合成     

Arsenic(II) sulfide quantum dots prepared by a wet process from its bulk

Arsenic(II) sulfide nanocrystals were fabricated by a wet process from its bulk through cluster-mediate transformation. The bulk arsenic(II) sulfide can be easily dissolved in ethylenediamine to form a solution-like cluster (As4S4-NH2C2H4NH2)). The cluster can be transformed to nanocrystals assisted by consumption of ethylenediamine in protic polar solvents with mild thermal treatment. The nanocrystals show size-dependent fluorescence ranging from UV to the blue, two photon fluorescence as well as cytotoxic effects on cancer cells.     

Nanoparticles and nanocrystals of a new bidentate nickel(II) complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide: synthesis,characterization, and crystal structures

The nickel(II) complex of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide has been synthesized and characterized by Fourier transform-infrared spectroscopy, elemental analysis, nuclear magnetic resonance spectroscopy, and mass spectrometry (atmospheric pressure chemical ionization mass spectrometry). The single-crystal X-ray structures of N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide (1) and bis[N-[ethyl(propan-2-yl)carbamothioyl]-4-nitrobenzamide]nickel(II) (2) have been determined from single-crystal X-ray diffraction data. Loss of the N–H proton resonance and the N–H stretching vibration and the shift of the ν_C=O and ν_C=S stretching vibrations confirm formation of the metal complex. These studies show that the metal complex is neutral in cis-configuration. The complex has been used as a single-source precursor for the deposition of nickel sulfide nanocrystals by thermolysis. The nickel sulfide nanocrystals were characterized by X-ray powder diffraction and transmission electron microscopy.     

A Mechanistic Study of the Multiple Roles of Oleic Acid in the Oil-Phase Synthesis of Pt Nanocrystals

Oleic acid (OAc) is commonly used as a surfactant and/or solvent for the oil-phase synthesis of metal nanocrystals but its explicit roles are yet to be resolved. Here, we report a systematic study of this problem by focusing on a synthesis that simply involves heating of Pt(acac)₂ in OAc for the generation of Pt nanocrystals. When heated at 80 °C, the ligand exchange between Pt(acac)₂ and OAc leads to the formation of a Pt^II–oleate complex that serves as the actual precursor to Pt atoms. Upon increasing the temperature to 120 °C, the decarbonylation of OAc produces CO, which can act as a reducing agent for the generation of Pt atoms and thus formation of nuclei. Afterwards, several catalytic reactions can take place on the surface of the Pt nuclei to produce more CO, which also serves as a capping agent for the formation of Pt nanocrystals enclosed by {100} facets. The emergence of Pt nanocrystals further promotes the autocatalytic surface reduction of Pt^II precursor to enable the continuation of growth. This work not only elucidates the critical roles of OAc at different stages in a synthesis of Pt nanocrystals, but also represents a pivotal step forward toward the rational synthesis of metal nanocrystals.     

Single-Source Molecular Precursor for Synthesis of Copper Sulfide Nanostructures

As a new precursor, [bis(thiosemicarbazide)copper(II)]chloride; ([Cu(TSC)₂]Cl₂), complex was used in thermal decomposition process for the synthesis of Cu₂S nanocrystals. The steric hindrance of the precursor raises the need of using co-surfactant, therefore oleylamine (C₁₈H₃₇N) and triphenylphosphine (C₁₈H₁₅P) were applied as solvent and surfactant of the reaction. CuS nanocrystals were synthesized via hydrothermal decomposition of [bis(thiosemicarbazide) copper(II)] without any surfactant. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. Synthesized copper sulfide nanostructures have average size of 20–50?nm. Finally, optical properties of the products were examined and investigated by PL spectra.     

Infrared spectroscopy of solid hydrogen sulfide and deuterium sulfide

The infrared spectra of solid hydrogen sulfide (H2S) and deuterium sulfide (D2S) were collected at very low temperatures. Vapor deposition of thin films at the lowest temperature of 10 K produced amorphous solids while deposition at 70 K yielded the crystalline phase III. Infrared interference fringe patterns produced by the films during deposition were used to determine the film thickness. Careful measurement of the integrated absorbance peaks, along with the film thickness, allowed determination of the integrated band intensities. This report represents the first complete presentation of the infrared spectra of the amorphous solids. Observations of peaks near 3.915 and 1.982 microm (ca. 2554 and 5045 cm(-1), respectively) may be helpful in the conclusive identification of solid hydrogen sulfide on the surface of Io, a moon of Jupiter.     

Delayed ignition of autocatalytic combustion precursors: low-temperature nanomaterial binder approach to electronically functional oxide films

Delayed ignition of combustion synthesis precursors can significantly lower metal oxide film formation temperatures. From bulk In(2)O(3) precursor analysis, it is shown here that ignition temperatures can be lowered by as much as 150 °C. Thus, heat generation from ~60 nm thick In(2)O(3) films is sufficient to form crystalline In(2)O(3) films at 150 °C. Furthermore, we show that the low processing temperatures of sufficiently thick combustion precursor films can be applied to the synthesis of metal oxide nanocomposite films from nanomaterials overcoated/impregnated with the appropriate combustion precursor. The resulting, electrically well-connected nanocomposites exhibit significant enhancements in charge-transport properties vs conventionally processed oxide films while maintaining desirable intrinsic electronic properties. For example, while ZnO nanorod-based thin-film transistors exhibit an electron mobility of 10(-3)-10(-2) cm(2) V(-1) s(-1), encasing these nanorods within a ZnO combustion precursor-derived matrix enhances the electron mobility to 0.2 cm(2) V(-1) s(-1). Using commercially available ITO nanoparticles, the intrinsically high carrier concentration is preserved during nanocomposite film synthesis, and an ITO nanocomposite film processed at 150 °C exhibits a conductivity of ~10 S cm(-1) without post-reductive processing.     

Surfactant-assisted fabrication PbS nanorods, nanobelts, nanovelvet-flowers and dendritic nanostructures at lower temperature in aqueous solution

PbS nanostructures with different morphologies, such as rod-like, belt-like, downy-velvet-flower-like and dendrite-like, were fabricated successfully under varied reaction conditions in aqueous solution at lower temperature by the assistance of surfactant CTAB. Especially, among all the synthesis methods for PbS nanocrystals, this is the first report using basic acetate of lead, which was formed at initial reaction stage, as a precursor to control the crystal nucleation rate. This synthesis method is a promising one to metal sulfide for its easy control, low-cost and large-scale production. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field-emission scanning electron microscopy (FE-SEM) and UV-visible spectrophotometer (UV-vis) were used to characterize the products. A rational mechanism is proposed and three control factors to the crystal directional growth are also concluded.