Synthesis of ZnS hollow nanospheres with holes using different amine templates

ZnS hollow nanospheres with holes were prepared by reacting ZnSO₄ with H₂S, the sulfide source formed in the reaction of CS₂ with ethylenediamine, 1,3-propylenediamine, butylamine or 2-(2-aminoethylamino) ethanol, which also acted as a template agent, at 50°C under agitation. The shape, particle size of about 100–850 nm and hole size of about 150–600 nm of ZnS hollow nanospheres with holes were shown by SEM and TEM images. These ZnS nanospheres with β cubic ZnS phase and composed of 2–5 nm nanocrystals were characterized by XRD and HRTEM. The blue shift of maximum absorption in UV-vis displayed the effect of quantum size. The two amino groups of amine templates reacted favorably with Zn²⁺ to form uniform and relatively smooth ZnS nanospheres with holes, while hydroxyethyl played a disadvantageous role. A reasonable mechanism of hole formation by H₂S rushing out is suggested. __________ Translated from Journal of Jinan University (Natural Science), 2007, 28(1): 92–95 [译自: 暨南大学学报(自然科学版)]     

The influence of solvent and ligands on characters of ZnS clusters

According to zinc blende and wurtzite structures of ZnS nanocrystals, four clusters (Zn₃S₃, Zn₄S₄, (Zn₃S₃)₂, and (Zn₃S₃)₃), were investigated at B3LYP/Lanl2dz theoretical level. In simultaneous consideration of the influence of solvent and ligands, we calculated their Raman and absorption peaks, which are agreement with experimentally reported results. The calculated Raman spectra of Zn₃S₃, Zn₄S₄, (Zn₃S₃)₂, and (Zn₃S₃)₃ are in the range of 260–310 cm⁻¹. During the calculation of absorption spectra, time-dependent density-functional theory (TDDFT) is employed. We have found an obvious blue-shift in the calculated wavelengths of the absorption peaks after consideration of the solvent. In solvent environment, the wavelength of absorption peak shifts to red with the increase of the atomic numbers from Zn₃S₃, to (Zn₃S₃)₂ and (Zn₃S₃)₃ clusters, which is induced by the quantum size effect. Since the sizes of the current calculated clusters are much smaller than the experimentally reported nano-sized ZnS nanocrystals, the calculated wavelengths of absorption peak of the four clusters are shorter than the nano-sized ZnS nanocrystals. Through the analysis of S–Zn–ligand structures, we speculate that the main influence of ligands comes from thiol of ligand because all S–Zn–ligand structures have similar Wiberg Bond Index (WBI) values, absorption spectra, and bond length in theory.     

Controllable synthesis of ZnS/PMMA nanocomposite hybrids generated from functionalized ZnS quantum dots nanocrystals

We reported controllable synthesis of ZnS nanocrystal-polymer transparent hybrids by using polymethylmethacrylate (PMMA) as a polymer matrix. In a typical run, the appropriate amounts of zinc chloride (ZnCl₂) and sodium sulfide (Na₂S) in the presence of 2-mercaptoethanol (ME) as the organic ligand were well dispersed in H₂O/dimethylformamide solution without any aggregation. In addition, the Mn-doped ZnS nanocrystals (NCs) were synthesized with similar method. Then, ZnS-PMMA hybrids were obtained via free radical polymerization in situ by using ZnS NCs functionalized with methacryloxypropyltrimethoxysilane (MPS). FT-IR characterization indicates the formation of robust bonding between ZnS NCs and the organic ligand. The TEM images show that ZnS NCs are well dispersed in PMMA matrix, and particle size of as-prepared ZnS NCs is about 2.6 nm, in agreement with the computing results of Brus’s model and Debye–Scherrer formula. The photoluminescence measurements present that ZnS NCs, Mn-doped ZnS NCs, and ZnS/PMMA hybrid show good optical properties.     

A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe

In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO₂-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO₂ composite nanoparticles with a SiO₂ surface coating. Our results showed that CdSe/ZnS/SiO₂ composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that the method had higher sensitivity and could count bacteria in 3 × 10² CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence peak intensity (Y) and the total bacterial count (X) was established in the range of 3 × 10²–10⁷ CFU/mL using the equation Y = 374.82X − 938.27 (R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the conventional plate count method, and the standard deviation was satisfactory.     

Calorimetric investigation of the formation of ZnS nanoparticles in w/o microemulsions

The enthalpies of precipitation of ZnS nanoparticles within water containing reversed micelles of sodium bis(2-ethylhexyl) solfosuccinate, L-α phosphatidylcholine, tetraethyleneglycol-mono-n-dodecyl ether and didodecyldimethylammonium bromide as a function of the molar concentration ratioR (R=[water]/[surfactant]) were measured by calorimetric technique. The results indicate that the energetic state of ZnS nanoparticles confined in the aqueous core of the reversed micelles is different from that in bulk water. Effects due to nanoparticle size, adsorption of HS⁻ ions on the nanoparticle surface and interactions between nanoparticles and water/surfactant interfaces are discussed. This work has been supported by MURST.     

Poly(MAA-Mn) for Triple-Layer Structure Synthesis of ZnS/ZnS:Mn/SiO2 Phosphors

Methacrylic acid (MAA) was used as a manganese carrier to prepare ZnS/MAA-Mn particles, and ZnS/ZnS:Mn phosphors were formed from ZnS/MAA-Mn by ion substitution through heat treatment. After silica coating on surface by chemical precipitation method with tetraethyl orthosilicate (TEOS), ZnS/ZnS:Mn/SiO₂ phosphors were prepared successfully as a new core/shell structure compound. The thickness of layers was controlled by adjusting concentrations of manganese (II) acetate (Mn(CH₃COO)₂) and TEOS. Structure, morphology, and composition of prepared phosphors were investigated by X-ray diffraction (XRD), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Photoluminescence (PL) properties of ZnS with different Mn²⁺ content were analyzed by PL spectrometer. PL emission intensity and PL stability were analyzed for evaluating effects of silica coating and Mn²⁺ activator doping. As a result, the structure of two layers could be observed, and optimum composition of ZnS/ZnS:Mn/SiO₂ structure was also obtained.     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

氧化石墨烯浓度对还原氧化石墨烯/ZnS电化学性能的影响

以氧化石墨烯(GO)、乙酸锌(Zn(CH₃COO)₂)和硫脲为原料,采用水热法成功制备了还原氧化石墨烯/ZnS(rGO/ZnS)复合材料,并将该材料用作锂离子电池负极。高导电性的 rGO可以为锂离子和电子的传输提供有效的路径,ZnS可以提供较高的理论比容量。rGO/ZnS复合材料在rGO与纳米级高度分散的类球形ZnS颗粒协同作用下展现了较好的嵌锂容量和循环性能。当GO质量浓度为2 mg·mL^-1时制备的rGO/ZnS复合材料的倍率性能最好,循环稳定性最佳。     

ZnS and ZnSe Nanoparticles via Solid-State and Solution Thermolysis of Zinc Silylchalcogenolate Complexes

The thermolysis of the zinc trimethylsilylchalcogenolate complexes (N,N′-tmeda)Zn(ESiMe₃)₂ (E = S, 1; E = Se, 2) and (3,5-Me₂-C₅H₃N)₂Zn(ESiMe₃)₂ (E = S, 3; E = Se, 4) has been investigated. Solid-state thermal decomposition of complexes 1–4 above 250°C results in the formation of hexagonal ZnS and cubic ZnSe, respectively, via the liberation of TMEDA (1–2) or 3,5-lutidine (3–4) and E(SiMe₃)₂. Solid-state or solution thermolysis of these complexes up to 200°C produces nanocrystalline ZnS and ZnSe materials whose surface is protected by either coordinated TMEDA or 3,5-lutidine ligands. The progress of the step-wise solid-state decomposition of these complexes was monitored by thermogravimetric and single differential thermal analysis and volatile decomposition products in both solution and solid-state experiments were identified by GC/MS.Dedicated to Professor Brian F. G. Johnson on the occasion of his retirement.     

Photocatalytic Reduction of Zn(II) with Participation of ZnS Nanoparticles

We have studied the photochemical processes occurring in colloidal ZnS solutions containing zinc chloride and sodium sulfite as additives. Irradiation of such systems leads to reduction of Zn(II), the rate of which increases as the size of the ZnS nanoparticles decreases. Based on analysis of the kinetic curves for the reaction, we hypothesize that photoreduction of Zn(II) is a two-electron process. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 4, pp. 231–235, July–August, 2005.     

ZnS纳米粒子的固相合成及其光学性能

将不同的添加剂引入到低温固相反应中，快速合成了不同尺寸的ZnS纳米粒子。利用TEM表征了产物形貌，利用XRD研究了不同的添加剂、同一添加剂下不同的反应温度、不同反应时间对纳米粒子尺寸的影响。结果表明，不同的添加剂对粒子的尺寸影响较大，其中，十二烷基胺以其特殊的反应方式在较高温度下获得了较小的纳米粒子。另外，在PEG400存在条件下，反应温度和反应时间对粒子尺寸均有一定的影响。同时，对不同条件下所得产物的紫外-可见光吸收性能也进行了测试。     

CdSe/ZnS量子点敏化太阳能电池电子注入与光伏性能表征

合成了CdSe/ZnS核壳结构量子点(QDs), 将其作为光敏剂吸附在TiO2纳米晶薄膜上, 组装成量子点敏化太阳能电池(QDSSCs), 从电子注入速率和电池性能两方面对QDSSCs进行了表征. 为了定量研究ZnS层包覆对电子注入的影响, 运用飞秒瞬态光谱技术, 测试了包覆ZnS前后, CdSe-TiO₂体系的电子注入速率. 实验测得ZnS包覆前后电子注入速率分别为7.14×10¹¹s^-1和2.38×10^-11s^-1, 可以看出包覆后电子注入速率明显降低, 仅为包覆前的1/3. 电池器件J-V性能测试表明, ZnS作为绝缘层包覆在CdSe的表面有效提高了QDSSCs的填充因子和稳定性, 但同时也导致了效率的降低. 上述结果说明了电子注入速率的降低是导致电池电流和效率下降的重要原因, 为今后优化核壳结构QDSSCs的电流和效率提供了依据.     

Synthesis of ZnS nanoparticles from pyridine adducts of zinc(II) dithiocarbamates

Zn(thqdtc)₂, Zn(thqdtc)₂(py) and Zn(thiqdtc)₂(py) (where thqdtc = 1,2,3,4-tetrahydroquinolinecarbodithioate, thiqdtc = 1,2,3,4-tetrahydroisoquinolinecarbodithioate and py = pyridine) have been used as single source precursors for the synthesis of ZnS nanoparticles. The formation of ZnS nanoparticles was achieved by thermal decomposition of the complex under heating in presence of triethylenetetraamine. Transmission electron microscopy, energy dispersive X-ray analysis (EDAX) and powder X-ray diffraction studies were carried out to study the structure and morphology of the nanoparticles. The optical properties of the ZnS nanoparticles were studied by UV–visible and fluorescence emission spectral studies. UV–visible absorption spectral studies indicate a blue shift in the absorption maxima due to the quantum size effect. A single crystal X-ray analysis was carried out for a precursor [Zn(thqdtc)₂].     

Effects of electron tunneling and nonresonance quenching of photoluminescence in semiconducting CdSe/ZnS AND CdSe nanocrystals by porphyrin molecules in joint complexes

The quenching of photoluminescence (PL) in semiconducting CdSe/ZnS and CdSe nanocrystals (NC) of various sizes during surface passivation by molecules of tetrapyridylporphyrins (P) in toluene at 295 K was investigated. It was shown that resonance transfer of energy NC → P plays a minor role in PL quenching (<10%), while photoinduced electron transfer NC → P is absent. On the basis of experimental data and quantum-mechanical calculations it was established that with identical molar ratio x = C_P/C_NC the probability of quenching k _q decreases with increase in the size of the NC while the PL quenching process itself under conditions of quantum confinement is due to electron tunneling of the excited electron–hole pair on the surface of the NC followed by localization of the organic ligand (P) on anchor groups. The obtained results are of interest for investigating the mechanisms of the blinking of PL in single semiconductor nanocrystals. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 45, No. 1, pp. 17–26, January–February, 2009.     

Theoretical study of the low-lying electronic states of ZnO and ZnS

Theoretical spectroscopic constants (r_e, D_e) and dipole moments (μ, ∂μ/∂r) are determined for the ¹σ⁺, ^1,3Π and ³σ⁺ states of ZnO and ZnS, using extended Gaussian basis sets and incorporating correlation using both configuration- interaction and coupled pair (CPF) methods. Relativistic corrections (Darwin plus mass velocity), included using first-order perturbation theory, are relatively small. At the CPF level, both ZnO and ZnS have ¹Σ⁺ ground states, with the ³Π state lying 209 and 2075 cm⁻¹ higher, respectively. The ³σ⁺ state lies about 1.5 eV higher in ZnO and 2.1 eV higher in ZnS. The ^1,3Π states are relatively close together since the exchange splitting is small with the σ electron localized on Zn and the π electron on oxygen (or sulfur).     

单分散ZnS纳米球与纳米梭之间的形貌转换及光学性能研究

利用平平加作为表面活性剂, 正戊醇作为助表面活性剂, 环己烷作为油相, 以硫化钠(Na₂S)和醋酸锌(Zn(Ac)₂)作为反应物, 通过控制反应条件在反相胶束体系中合成出单分散的ZnS纳米球与纳米梭. 采用XRD和TEM对产物的结构和形貌进行表征, 结果表明产物均为六方相ZnS, 晶胞参数为a＝0.3823 nm, c＝56.2 nm, 纳米球直径约为50 nm, 纳米梭直径约为60 nm, 长度约为110 nm. 采用UV-Vis(紫外可见吸收光谱)和PL(荧光光谱)研究了产物的光学性能. 纳米球的紫外可见光谱的吸收峰出现在288 nm处, 而纳米梭在305 nm处有强吸收峰, 与块体材料相比, 分别有约60和50 nm的蓝移. 当激发波长为270 nm时, 纳米球和纳米梭产物分别能够发出波长为408和303 nm的紫外光.     

Nanostructured ZnS with random close-packed structure: Synthesis,formation rate,and crystal structure study

The chemical precipitation of nanocrystalline ZnS from aqueous alkaline solutions containing zinc ethylenediamine complex salt Zn(En)²⁺ and thiocarbonic acid diamide N₂H₄CS was studied in the course of time in terms of formal chemical kinetics. The ZnS formation rate was found to depend on the concentration of precipitation agent (N₂H₄CS) and to decrease with increasing the ligand (ethylenediamine) concentration, whereas the pH dependence is less pronounced. The size of resulting ZnS nanoparticles does not exceed 5 nm, and their crystal structure was identified as a random close packed structure.     

Effect of formation conditions on the structure, morphology and magnetic properties of nanosized MIIFe 2III O4 ferrites (M = Mn, Co, Ni) and Fe2O3

A study was carried out on the conditions of formation of highly crystalline, superparamagnetic, nanosized oxides, M^II Fe ₂ ^III O₄ and γ-Fe₂O₃ (4.9–11.7 nm) by the thermal decomposition of complexes [MFe₂O(CH₃CO₂)₆(H₂O)₃] (M = Mn, Fe, Co, Ni) in tetraethylene glycol. The presence of surfactants leads to a decrease in the size and size distribution of the nanoparticles formed, while the use of microwave radiation significantly reduces the time for formation of the nanocrystalline oxides. The magnetic measurements showed ferrimagnetic ordering in the nanoparticles studied and their superparamagnetic behavior. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 5, pp. 323–329, September–October, 2007.     

Synthesis of Multifunctional Mn‐Doped CdTe/ZnS Core/Shell Quantum Dots

The synthesis of a novel water‐soluble Mn‐doped CdTe/ZnS core‐shell quantum dots using a proposed ultrasonic assistant method and 3‐mercaptopropionic acid (MPA) as stabilizer is descried. To obtain a high luminescent intensity, post‐preparative treatments, including the pH value, reaction temperature, reflux time and atmosphere, have been investigated. For an excellent fluorescence of Mn‐doped CdTe/ZnS, the optimal conditions were pH 11, reflux temperature 100°C and reflux time 3 h under N₂ atmosphere. While for phosphorescent Mn‐doped CdTe/ZnS QDs, the synthesis at pH 11, reflux temperature 100°C and reflux time 3 h under air atmosphere gave the best strong phosphorescence. The characterizations of Mn‐doped CdTe/ZnS QDs were also identified using AFM, IR, powder XRD and thermogravimetric analysis. The data indicated that the photochemical stability and the photoluminescence of CdTe QDs are greatly enhanced by the outer inorganic ZnS shell, and the doping Mn²⁺ ions in the as‐prepared quantum dots contribute to strong luminescence. The strong luminescence of Mn‐doped CdTe/ZnS QDs reflected that Mn ions act as recombination centers for the excited electron‐hole pairs, attributing to the transition from the triplet state (⁴T₁) to the ground state (⁶A₁) of the Mn²⁺ ions. All the experiments demonstrated that the surface states played important roles in the optical properties of Mn‐doped CdTe/ZnS core‐shell quantum dots.     

片状Co9S8/ZnS/C复合材料的制备及电催化产氧性能

以六水合硝酸钴[Co(NO_3)_2·6H_2O]为钴源、六水合硝酸锌[Zn(NO_3)_2·6H_2O]为锌源、2,2′-硫代二乙酸(C4H6O4S)为硫源,采用溶剂热法制备出了片状的Co_9S_8/ZnS/C复合材料。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和N_2吸附/脱附测试等手段对于片状Co_9S_8/ZnS/C复合材料结构和形貌等进行表征,同时对片状Co_9S_8/ZnS/C复合材料进行了电催化产氧性能测试。结果表明:片状Co_9S_8/ZnS/C复合材料的起始过电位为390 mV,塔菲尔斜率为144 mV·dec~(-1),具有高的电催化产氧性能。