Formation and Structure Characterization of Flower-like ZnS Microspheres

ZnS nanophases were synthesized through a low-temperature route using a mixed solvent, diethylenetriamine （DETA） and deionized water （DIW）, as the reaction medium. The assynthesized products were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high-resolution transmission electron microscopy （HRTEM）. The experimental results indicate that ZnS nanophase is formed through a phase evolution of ZnS·（DETA）1/2→ ZnS.DETA→ZnS. The ZnS flower-like microspheres sized around 2μm consist of many nanobelts whose structure could be regarded as an alternative admixture of hexagonal wurtzite （WZ） and cubic zinc blende （ZB）. The optical absorption measurements demonstrate that the spectral feature of the sample changes with the evolution of the phase structure.     

MnS hierarchical hollow spheres with novel shell structure

High yields of MnS microspheres with novel hierarchical structure were prepared through a simple solution method. Field emission scanning electron microscopy and transmission electron microscopy analyses reveal that the microsphere has a core-shell structure: the interior hollow sphere is covered by a shell consisting of nanorod arrays. Interestingly, the nanorod is a wurtzite (WZ)/zinc blende (ZB) phase admixture with a large amount of stacking faults/twins. The alternation of WZ and ZB along the growth direction of the nanorod enables it to exhibit the features of a quantum well. Furthermore, the WZ/ZB admixture structure could also be regarded as a type II homomaterial heterostructure. All these features imply that the novel core-shell structure has great potential for applications, among them the quantum well photoelectrical and heterostructure photoconduction fields.     

Charge Separation in Wurtzite/Zinc‐Blende Heterojunction GaN Nanowires

The electronic properties of wurtzite/zinc‐blende (WZ/ZB) heterojunction GaN are investigated using first‐principles methods. A small component of ZB stacking formed along the growth direction in the WZ GaN nanowires does not show a significant effect on the electronic property, whereas a charge separation of electrons and holes occurs along the directions perpendicular to the growth direction in the ZB stacking. The later case provides an efficient way to separate the charge through controlling crystal structure. These results have significant implications for most state of the art excitonic solar cells and the tuning region in tunable laser diodes.     

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.     

Synthesis and characterization of high-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) luminescent nanocrystals

High-quality ZnS, ZnS:Mn2+, and ZnS:Mn2+/ZnS (core/shell) nanocrystals (NCs) were synthesized via a high-boiling solvent process and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectra. The monodisperse ZnS NCs (size = 8 nm), which self-assembled into several micrometer-sized domains, were achieved by adopting poly(ethylene glycol) (PEG) in the reaction process (without using a size-selection process). The obtained ZnS:Mn2+ and ZnS:Mn2+/ZnS core/shell NCs are highly crystalline and quasimonodisperse with an average particle size of 6.1 and 8.4 nm, respectively. All of the as-formed NCs can be well dispersed in hexane to form stable and clear colloidal solutions, which show strong visible emission (blue for ZnS and red-orange for ZnS:Mn2+ and ZnS:Mn2+/ZnS) under UV excitation. The growth of a ZnS shell on ZnS:Mn2+ NCs, that is, the formation of ZnS:Mn2+/ZnS core/shell NCs, resulted in a 30% enhancement in the PL intensity with respect to that of bare ZnS:Mn2+ NCs due to the elimination of the surface defects.     

Der Chemische Transport von Mischkristallen im System FeS/MnS/ZnS

Chemical Vapor Transport of Solid Solutions. 7. Chemical Vapor Transport of FeS/MnS/ZnS Mixed Crystals By means of chemical vapor transport using iodine as transport agent (900 → 800 °C) it is possible to prepare in the quasiternary system FeS/MnS/ZnS the mixed crystals (Fe,Mn,Zn)S (sphalerite and wurtzite type), (Fe,Mn)S(ZnS) (NaCl type) and FeS(MnS,ZnS) (NiAs type) in form of single crystals. Based on the composition of these phases the phase diagram for the system FeS/MnS/ZnS at 800 °C was drawn up. The incongruent transport process leads to the accumulation of ZnS in the crystallization zone.     

Regional variation of sediment load of Asian rivers flowing into the ocean

CdS, CdS:Mn, ZnS, ZnS:Mn and ZnS:Tb nanoparticles were prepared by using carboxylic-containing copolymer, polystyrene-maleic anhydride (PSM), as template. Average particle size, 2.5 nm for CdS nanoparticles, is deduced from UV-vis absorption spectra and consistent with the observation of TEM. Characteristic emissions of the doping ions can be observed and the energy transfer from the host to the doping ions is verified. Fourier transform infrared (FTIR) spectra were studied to confirm the bonding effect of the copolymer and the metal ions. PSM hydrolyzed and chelated metal ions by its carboxylic group, and then performed as a protection layer after the formation of nanoparticles.     

Der Chemische Transport von Mischkristallen in den Systemen MnS/ZnS,FeS/ZnS und FeS/MnS

Chemical Vapor Transport of Solid Solutions. 5 Chemical Transport of MnS/ZnS, FeS/ZnS, and FeS/MnS Mixed Crystals By means of chemical vapor transport it is possible to prepare in the quasibinary systems MnS/ZnS, FeS/ZnS, and FeS/MnS the mixed crystals (Mn,Zn)S (sphalerite- and wurtzite-type), (Fe,Zn)S (sphalerite- and wurtzite-type), (Fe,Mn)S (NaCl-type), MnS(ZnS) (NaCl-type), FeS(ZnS) and FeS(MnS) (both NiAs-type) in form of single crystals. The experiments harmonize with the phase diagrams. Lattice parameters have been determined.     

Facile synthesis of highly luminescent Mn-doped ZnS nanocrystals

Manganese-doped zinc sulfide quantum dots (Mn:ZnS d-dots) with high optical quality, pure dopant emission of 55-65% photoluminescence quantum yield, were synthesized in octadecene media with generic starting materials, namely, zinc (manganese) carboxylic acid salts, S powder, and dodecanethiol (DDT) based on a "nucleation doping" strategy. The optical properties and structure of the obtained Mn:ZnS d-dots have been characterized by UV-vis, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The resulting nearly monodisperse d-dots were found to be of spherical shape with a zinc-blende crystal structure. The influences of various experimental variables, including the reaction temperature for the MnS core nanocluster and ZnS host material, the amount of octadecene (ODE)-S, DDT, as well as Zn/Mn ratio have been systematically investigated. The use of DDT as capping ligand ensured the reproducible access to a stable small-sized MnS core. This paves the way for reproducibly obtaining highly luminescent d-dots. Programmed overcoating temperature for growth of ZnS shell was employed to realize balanced diffusion of the Mn ions in the d-dots.     

Photophysics and charge dynamics of Q-PbS based mixed ZnS/PbS and PbS/ZnS semiconductor nanoparticles

The surface of ZnS and PbS has been modified by interfacing PbS on ZnS and ZnS on PbS nanoparticles. This produced core-shell nanocomposites ZnS/PbS and PbS/ZnS with tunable electronic properties. In both structures PbS particles are present in cubic form with an average diameter of about 6 nm. The addition of Pb2+ (3 x 10(-4) mol dm(-3)) to Q-ZnS (1.5 x 10(-4) mol dm(-3)) in the basic pH range produces size-quantized fluorescent PbS particles coated by metal hydroxides. In these particles the relaxation kinetics of charge carriers has been followed using a picosecond single-photon counting technique. At 1.5 x 10(-4) mol dm(-3) Pb2+ an interfacial relaxation of charge from ZnS to PbS phase could be observed in subnanosecond time domain. An increase in [Pb2+] from 2 x 10(-4) to 1 x 10(-3) mol dm(-3) enhanced the average emission lifetime from 9.4 to 19.4 ns. Composite PbS/ZnS particles are produced at high [ZnS] only. These particles had emission lifetime in mus time range. The extent of charge separation and the dynamics of charge carriers could be manipulated by the surface modification of these nanostructures.     

New observations on the luminescence decay lifetime of Mn2+ in Zns: Mn2+ nanoparticles

A fast decay emission peaking at 645 nm with a decay lifetime within the experimental resolution of 0.14 micros is observed in ZnS:Mn2+ nanoparticles. This short-lived signal is also observed in pure ZnS and MgS: Eu3+ nanoparticles, which has nothing to do with Mn(2+)-doped ions but is from the deep trap states of the host materials. The short-lived component decreases in intensity relative to the Mn2+ emission at higher excitation powers, while it increases in intensity at low temperatures and shifts to longer wavelengths at longer time delays. Our observations demonstrated further that the emission of Mn2+ in ZnS: Mn2+ nanoparticles behaves basically the same as in bulk ZnS: Mn2+; the fast decay component is actually from the intrinsic and defect-related emission in sulfide compounds.     

Room temperature ferromagnetism in Mn-doped ZnS nanocrystalline thin films grown by sol–gel dip coating process

Nanocrystalline Zn_1?xMn_xS (x = 0.00, 0.01, 0.02, 0.03, 0.05, and 0.1) thin films having different Mn content were grown by the sol–gel dip coating process. The effect of Mn content on the structural, optical and magnetic properties of Zn_1?xMn_xS nanocrystalline thin films were investigated. X-ray diffraction results showed the presence of single hexagonal phase corresponding to ZnS with a preferred orientation along the ZnS (002) hexagonal plane direction without any detectable secondary phase, suggesting the incorporation of Mn ions into the ZnS lattice. Scanning electron microscope revealed the surface of the nanocrystalline films to be homogeneous and dense and the grains of the film surface were randomly scattered. In ultraviolet–visible measurements, the band gap energy corresponding to the absorption edge estimated were found to be 3.59–3.23 eV depending on the Mn doping ratio. Magnetic measurements showed that a paramagnetic behavior at 5 K and ferromagnetic behavior at 300 K.     

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.     

High-quality manganese-doped zinc sulfide quantum rods with tunable dual-color and multiphoton emissions

We report a simple, fast and green phosphine-free colloidal chemistry to synthesize high-quality wurtzite-type Mn-doped ZnS quantum rods (QRs) with tunable diameters (1.6-5.6 nm), high aspect ratios (up to 50), variable Mn doping levels (0.18-1.60%), and high quantum yields (up to 45%). The electron paramagnetic resonance spectra with modeling reveal the successful doping of paramagnetic Mn(2+) ions in the host ZnS QRs. The Mn-doped ZnS QRs demonstrate tunable dual-color (orange and blue) emissions by tuning the doping levels and UV excitation wavelengths. The orange emission with long decay lifetime (3.3 ms) originates from the doped Mn(2+) states, while the blue emission with fast decay lifetime (0.31 ns) is attributed to the QR surface states. The bright two- and three-photon excitation upconversion luminescence from the Mn-doped ZnS QRs have been observed using tunable near-infrared femtosecond laser. Our strategy provides a versatile route to programmably control the optical properties of anisotropic semiconductor nanomaterials, which may create new opportunities for photonic devices and bioimaging applications.     

Hierarchical saw-like ZnO nanobelt/ZnS nanowire heterostructures induced by polar surfaces

Saw-like nanostructures composed of single-crystalline ZnO nanobelts and single-crystalline ZnS nanowires have been successfully synthesized by a vapor-solid process. Several techniques, including scanning electron microscope, transmission electron microscopy, and photoluminescence spectroscopy, were used to investigate the structures, morphology, and photoluminescence properties of the products. Due to the similar crystal habits of wurtzite ZnO and ZnS with chemically active Zn-terminated (0001) and chemically inactive O-terminated (or S-terminated) (000) polar surfaces, hierarchical saw-like nanostructures were considered to be formed by the initiation of a chemically active Zn-terminated ZnO (0001) polar surface. Photoluminescence properties of the heterostructures, different from pure ZnO nanobelts or ZnS nanowires, were also studied at room temperature.     

Thermal conductivity of wurtzite and zinc blende cubic phases of BeO from ab initio calculations

The structural, mechanical, thermal and thermodynamic properties of Beryllium oxide (BeO) in the zinc blende (ZB) and wurtzite (WZ) form have been calculated using the density functional theory (DFT) in the general gradient approximation (GGA). The ground state structural and elastic properties of wurtzite BeO (w-BeO) is calculated using the new GGA ultrasoft pseudopotentials for solids (pbesol); the simulated results have shown excellent agreement with the experiments. The thermodynamic properties are studied using quasi-harmonic approximation (QHA), and the predicted properties agree well for the WZ phase for which the experimental data are available, while for ZB phase it remains to be validated with future experiments. Both Boltzmann transport equation (BTE) and Slack model were used to calculate the lattice thermal conductivity of wurtzite BeO (w-BeO). Furthermore, the thermal conductivity along the crystallographic ‘a’ and ‘c’ axis of wurtzite BeO is investigated using BTE. Our calculation of w-BeO agrees well with the available experimental measurements. Apart from these studies on w-BeO, we have also compared the mechanical, structural and phonon dispersions of z-BeO with previously reported theoretical studies. Additionally we report the volume thermal expansion and the heat capacity at constant pressure of z-BeO for the first time and the bulk thermal conductivity of zinc blende BeO (z-BeO) using BTE.     

Investigation of the charge compensation mechanism on the electrochemically Li-ion deintercalated Li1-xCo1/3Ni1/3Mn1/3O2 electrode system by combination of soft and hard X-ray absorption spectroscopy

In situ hard X-ray absorption spectroscopy (XAS) at metal K-edges and soft XAS at O K-edge and metal L-edges have been carried out during the first charging process for the layered Li1-xCo1/3Ni1/3Mn1/3O2 cathode material. The metal K-edge XANES results show that the major charge compensation at the metal site during Li-ion deintercalation is achieved by the oxidation of Ni2+ ions, while the manganese ions and the cobalt ions remain mostly unchanged in the Mn4+ and Co3+ state. These conclusions are in good agreement with the results of the metal K-edge EXAFS data. Metal L-edge XAS results at different charge states in both the FY and PEY modes show that, unlike Mn and Co ions, Ni ions at the surface are oxidized to Ni3+ during charge, whereas Ni ions in the bulk are further oxidized to Ni4+ during charge. From the observation of O K-edge XAS results, we can conclude that a large portion of the charge compensation during Li-ion deintercalation is achieved in the oxygen site. By comparison to our earlier results on the Li1-xNi0.5Mn0.5O2 system, we attribute the active participation of oxygen in the redox process in Li1-xCo1/3Ni1/3Mn1/3O2 to be related to the presence of Co in this system.     

Water-soluble silica-overcoated CdS:Mn/ZnS semiconductor quantum dots

Highly luminescent and photostable CdS:Mn/ZnS core/shell quantum dots are not water soluble because of their hydrophobicity. To create water-soluble quantum dots by an appropriate surface functionalization, CdS:Mn/ZnS quantum dots synthesized in a water-in-oil (W/O) microemulsion system (reverse micelles) were consecutively overcoated with a very thin silica layer ( approximately 2.5 nm thick) within the same reverse micellar system. The water droplet serves as a nanosized reactor for the controlled hydrolysis and condensation of a silica precursor, tetraethyl orthosilicate (TEOS), using an ammonium hydroxide (NH4OH) catalyst. Structural characterizations with transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS) indicate that the silica-quantum dot nanocomposites consist of a layered structure. Owing to the amorphous, porous nature of a silica layer, the optical and photophysical properties of silica-overcoated CdS:Mn/ZnS quantum dots are found to remain close to those of uncoated counterparts.     

基于Mn掺杂ZnS量子点室温磷光法检测盐酸巴马汀

本文以3-巯基丙酸(3-Mercaptopropionic Acid,MPA)为稳定剂,采用水相合成法制备了Mn掺杂ZnS量子点(Mn∶ZnS QDs),基于Mn∶ZnS QDs的室温磷光性质,盐酸巴马汀(Palmatine Hydrochloride,PaH)可与Mn∶ZnS QDs发生静电作用,使得Mn∶ZnS QDs发生室温磷光猝灭效应,从而发展了一种高效、快速检测人体体液中痕量PaH的新方法。实验结果表明,当PaH的浓度在0.75~30μmol/L范围时,其浓度与室温磷光猝灭强度(ΔIRTP)呈良好的线性关系,相关系数为0.996,检出限为0.35μmol/L,加标回收率为94.0%~103.3%。     

水溶液中Mn2+对硫化锌纳米粒子形貌的调控作用

利用硫代乙酰胺在水溶液中缓慢释放的S2-与Zn2+反应制备了ZnS纳米颗粒,ZnS纳米颗粒沉积吸附在3-磺酸基丙基三甲氧基硅烷自组装单层膜上。 实验发现,溶液中添加少量Mn2+,可以显著影响ZnS纳米颗粒的形貌,对ZnS纳米晶的生长方向也有重要影响。 EDS和XRD谱证实Mn2+并没有掺杂到纳米颗粒中去。 这为纳米粒子形貌的调控提供了新途径。 并对ZnS的形成过程进行了探讨,并提出了可能的影响纳米材料形貌的机制。