PbS microcrystals with a magic‐square‐like structure prepared by a simple hydrothermal method

PbS microcrystals with a magic‐square‐shaped structure were successfully fabricated via a simple hydrothermal route, employing (CH₃COO)₂Pb and Na₂S₂O₃ as the lead and sulfur source without the assistance of any surfactant or template. S₂O₃^2‐ ions acted not only a supplier of S^2‐ ions but also a coordinating reagent. The formation of the above morphology was the direct result of the coordination between thiosulfate ions and lead ions. Researches indicated that the different synthetic approach could influence the morphology of the final product. A possible formation mechanism was suggested. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Controllable fabrication and growth mechanism of hematite cubes

Monodispersed and single‐crystalline hematite (α‐Fe₂O₃) cubes have been successfully prepared by a template‐free hydrothermal synthetic route with FeCl₃ and CH₃COONH₄. The influences of the reactant concentration, reaction temperature, and reaction time on the crystal growth were systematically investigated. The results show that the monodisperse hematite cubes with high crystalline and narrow size distribution could be fabricated at the hydrothermal temperature of 160 °C for 24 h while the concentrations of FeCl₃ and CH₃COONH₄ were in the range of 0.03‐0.5 M and 0.05‐0.1 M, respectively. In addition, the formation mechanism of hematite cube is also proposed, where the CH₃COONH₄ plays a role of shape controller in the formation of cube hematite structure. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

In situ measurement of growth kinetics of {100} KDP crystal faces in the presence of polyphosphate impurities

The face growth rate and critical supersaturation of {100} face were in situ measured using the laser‐polarization‐interference technique in the presence of potassium pyrophosphate, trimetric sodium phosphate and sodium hexametaphosphate impurities. The polyphosphate impurities inhibit the growth rate of prismatic faces. The face growth rate as a function of supersaturation at different impurity concentrations, as well as critical supersaturation as a function of impurity concentrations, was found in good agreement with a two‐dimensional nucleation model in the pure system and Kubota and Mullin's model in the presence of impurities. The average distance L between active sites available for impurity adsorption as well as the edge free energy was calculated. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation and characterization of monodispersed PbSe nanocubes

Monodispersed PbSe nanocubes were synthesized through a simple hydrothermal method by using Pb²⁺‐EDTA complex and Na₂SeSO₃. Composition and morphology of the samples were characterized by means of XRD, TEM and SEM. The gradually releasing of Pb²⁺ from Pb²⁺‐EDTA complex, and the adopting of PVP can adjust the growth rate in <100> and <111> directions of PbSe. Both Pb²⁺‐EDTA complex and PVP played important roles in the crystal growth of the monodispersed PbSe nanocubes. In addition, UV‐vis and photoluminescence properties were characterized. E_g of the PbSe nanocubes is 1.5 eV approximately, which is much larger than that of bulk PbSe. Under PL excitation at 406 nm, a red emission peak at 696 nm is observed, showing that the synthesized PbSe is luminescent nanomaterials. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth of mixed‐valence ammonium vanadates

A new method has been developed for the synthesis of mixed‐valence ammonium vanadate crystals. Single crystals of (NH₄)₂V₃O₈ were synthesized on a large scale by hydrothermal reduction of NH₄VO₃ in ethanol‐H₂O solutions in the presence of triblock copolymer Pluronic P123. The crystals are shining thin plates with (001) cleavage planes. Calcination of the (NH₄)₂V₃O₈ crystals at 300°C or above resulted in pure phases of V₂O₅. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Capsule‐like α‐Fe2O3 nanoparticles: Synthesis,characterization, and growth mechanism

Uniform capsule‐like α‐Fe₂O₃ particles were synthesized via a simple hydrothermal method, employing FeCl₃ and CH₃COONa as the precursors and sodium dodecyl sulfate (SDS) as soft template. X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and high‐resolution transmission electron microscopy were used to characterize the structure of synthesized products. Some factors influencing the formation of capsule‐like α‐Fe₂O₃ particles were systematically investigated, including different kinds of surfactants, the concentration of SDS, and reaction times. The investigation on the evolution formation reveals that SDS was critical to control the morphology of final products, and a possible five‐step growth mechanism was presented by tracking the structures of the products at different reaction stages.     

Ferrous Tartrate recognition of sodium chloride {111} and its effect on crystal growth

The surface morphology and growth pattern of some molecules could be altered by the recognition of ferrous tartrate (FeC₄H₄O₆, FeTA). We have explored this phenomenon in the aspect of growth rate and morphology alteration of sodium chloride crystals where few researches have been done. In this paper, the crystallization behavior of NaCl with added FeTA was studied by supersaturation test, conductivity, scanning electron microscopy (SEM), and X‐ray diffraction (XRD). The results showed that the supersaturation of NaCl solution could be increased to about 5.5 % in presence of FeTA prior to the onset of crystallization. Furthermore, SEM images and XRD results indicated that the addition of FeTA could change the morphology of NaCl crystal from cubic to octahedron by impeding the growth of {111} and {110} faces. Besides, the interaction between NaCl {111} face and FeTA was discussed and the possible spatial structure of FeTA was speculated through the lattice parameters of NaCl.     

Shape controllable growth of PbS polyhedral crystals

In this study, a series of PbS polyhedra were synthesized through hydrothermal decomposition of the as‐formed lead diethyldithiocarbamate (Pb‐DDTC) single‐source precursor in its precursor solution. Through extensive experiments, it was concluded that the amount of poly‐(vinylpyrrolidone) (PVP), DDTC and the reaction time had major effects on the shapes of the as‐synthesized PbS crystals. Sub‐micro sized cuboctahedrons and cubes were selectively obtained by manipulating the concentration of PVP and the reaction time. Possible growth mechanism for the shape controlled synthesis of PbS crystals was briefly discussed.     

A simple glucose reduction route for the synthesis of sheet‐like copper dendrites

In the current paper we designed a simple glucose reduction route for synthesis of sheet‐like Cu dendrites on a high yield, using CuSO₄ as the starting material. The reaction was carried out at 180 °C for 18 h in the absence of any structure‐directing agent. The product was characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron diffraction (ED). Some factors influencing the shapes of Cu microcrystals, including the reaction temperature, time, and the concentration of the starting CuSO₄, were investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preparation of PbS nano‐microcrystals with different morphologies and their optical properties

PbS nano‐microcrystals were prepared from Pb(OAc)₂·3H₂O and sulfur in a solution without any surfactant using the solvothermal process. Different morphologies, mainly including polyhedron microcrystals and sphere‐like assemblies, were characterized using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). PbS nano‐microcrystals with cubic crystal structure were detected using X‐ray diffraction (XRD), electron diffraction (ED) and high resolution transmission electron micrograph (HRTEM) techniques. The optical properties were investigated by ultraviolet‐visible (UV‐vis) spectroscopy, and photoluminescence spectroscopy (PL). The UV‐vis absorption peaks of PbS exhibited a large blue‐shift and the PL spectra had a strong and broad emission bands centered at 408 nm. The crystal growth mechanism of PbS was also discussed.     

The effect of pH on the growth of the {100} faces of ammonium dihydrogen phosphate crystals

The velocity and shape of growth layers on the {100} faces of ammonium dihydrogen phosphate (ADP) crystals growing in aqueous solution at pH = 5.0 are compared with those previously reported for growth at pH = 3.8. The results are interpreted in terms of the adsorption of hydrated hydroxonium ions on the crystal surface.     

Exposure of high index facets in KDP crystals

A series of KDP crystals doped with WO₄^2‐ additive was grown by using rapid growth method. WO₄^2‐ additive inhibited the growth of (100) faces and made (100) faces tapering. With high additive concentration, two adjacent (100) faces twisted towards their intersecting crystal edge and (100) faces became twisting. Moreover, high index facets of (512) were exposed when the additive concentration was 500 ppm. The element analysis suggested that WO₄^2‐ was prone to being incorporated with (100) face. The growth kinetics of (100) face testified that WO₄^2‐ played an inhibited role. The AFM investigation on (100) face indicated WO₄^2‐ could impede step bunching. High concentration of WO₄^2‐ could kink the terrace of the macro‐steps and create another series of macro‐steps. The motion direction of the new creative steps was vertical to that of the original steps. When the motions of the vertical steps were both inhibited by WO₄^2‐, the steps would become tapering and (100) face would twist, which ultimately led to the exposure of (512) facets. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth morphology of {100} faces of L‐Arginine phosphate monohydrate single crystals investigated by atomic force microscopy

Morphology of the {100} faces of L‐arginine phosphate monohydrate (LAP) single crystal grown at 25 °C at a supersaturation of 0.32 has been discussed. The rectangular dislocation growth hillocks elongate along the b direction, which manifests the fast growth due to the strong Period Bond Chain (PBC) bonds along this direction. Apart from that, the growth hillocks are consistent with the macro‐morphology of the crystal grown at the pH value of about 4.2. The lopsided shapes of the hillocks result from step bunching. Triangular pits are assumed to form during the process of the steps getting across the impurities. The hollow cavities existing on the growth hillocks also elongate along the b direction and they can lead to the formation of other defects such as dislocations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth and spectral analysis of Dy3+ and Er3+ doped KPb2Cl5 as a mid‐infrared laser crystal

This paper reports crystal growth and optical characteristics of dysprosium (Dy³⁺) and erbium (Er³⁺) doped mid‐infrared laser crystal ternary‐potassium‐lead‐chloride (KPb₂Cl₅). Two transparent crystals with good optical quality have been grown successfully by using the Bridgman technique,the largest crystal size reaches up to ∅︁10×60mm². Measurements of X‐ray diffraction(XRD) and absorption spectra were carried out. Based on Judd‐Ofelt theory, the intensity parameters Ω_t(t=2,4,6), the experimental and theoretical oscillator strengths have been obtained.The intensity parameters Ω_t(t=2,4,6) of Er³⁺:KPb₂Cl₅ were calculated to be Ω₂=5.10×10^‐20 cm², Ω₄=1.25×10^‐20 cm², Ω₆=0.83×10^‐20 cm², and the values for Dy³⁺:KPb₂Cl₅ were calculated to be Ω₂=6.26×10^‐20 cm², Ω₄=2.45×10^‐20 cm², Ω₆=0.04×10^‐20 cm² respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Catanionic surfactants assisted synthesis of dilead pentaoxochromate nanorods

Single‐crystalline dilead pentaoxochromate (Pb₂CrO₅) with nanorod‐shape has been synthesized by adjusting the pH value of the catanionic reverse micelles formed by a cationic surfactant CTAB (hexadecyltrimethylammonium bromide) and an anionic surfactant SDS (sodium dodecyl sulfonate), followed by a hydrothermal process. The results show that reaction parameters play important roles in the formation of the single‐crystalline Pb₂CrO₅. The reaction parameters include the kinds of the surfactants, the molar ratio (r) between the mixed cationic and anionic surfactants, reaction time and temperature. The as‐synthesized products are characterized by transmission electron microscopy (TEM), high‐resolution transmission electron microscopy (HRTEM) and powder X‐ray diffraction (XRD). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effects of anions on rapid growth and growth habit of KDP crystals

The synthesis of KDP from its raw material has been found exist in the growth solution. In the crystal growth experiment, significant extension of specific faces was observed at low dopant concentration. At high doping concentration, the growth rate of the whole crystal decreased with no significant habit modification. The inhibiting effects of phosphite and other H-bonding anionic ions on the growth of pyramidal faces are discussed. Rapid growth rate experiments have been carried out with purified material and an averaged growth rate of 18.6mm/day was obtained.     

Hydrothermal synthesis of nano‐crystalline BaMoO4 under mild conditions using simple additive

Large‐scale high‐quality BaMoO₄ nanocrystals have been synthesized in aqueous solutions under mild conditions with citrate as a simple additive. The crystals have bone‐like, spindle‐like and wheatear‐like morphologies assembled from nanoparticles, nanofibers and have been characterized by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. The results showed that experimental parameters had great influences on the shape evolution of products. The adjustment of these parameters such as room temperature stirring time, reaction temperature and reaction time of hydrothermal reaction, can lead to obvious morphology changes of products, and the growth mechanism has been proposed. Room‐temperature photoluminescence indicated that the as‐prepared BaMoO₄ nanocrystals had a strong blue emission peak at 481.5 nm. This facile route could be employed to synthesize more promising nanomaterials with interesting self‐assembly structures. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Direct Growth of Aggregates on {110} Faces of Cadmium Mercury Thiocyanate Crystals

New growth phenomena ‐ direct incorporation of aggregates have been observed on the {110} faces of cadmium mercury thiocyanate CdHg(SCN)₄ crystals by atomic force microscopy. These aggregates grow in two forms: some directly cover up the steps and forms new growth layers; while others are just incorporated at the step edges. These aggregates, which are mostly oriented along [111] direction, are formed by small columnar structural units. The aggregates have the similar structure of CdHg(SCN)₄ crystals and greatly vary in nature with the variation of solution supersaturation σ and growth time t. With the increase of σ the aggregates become larger, consistent with the variation of growth units dimension with the supersaturation; and with the increase of growth time the aggregates become more structurally substantial. These observations have led to a new understanding about the crystal growth.     

The influence of the lattice misfit on the growth of CuGaSe2 Epitaxial Films on {100}-oriented GaAs and GaP Substrates

CuGaSe₂ epitaxial layers were prepared on GaAs and GaP {100}-oriented substrates by flash evaporation technique and characterized by RHEED. Different epitaxial relationships have been found for growth on the different types of substrate material. The orientation is determined by the minimum misfit.     

Growth of ultra‐high purity PbI2 single crystal: (1) Preparation of high purity PbI2

In order to prepare high purity lead iodide (PbI₂) single crystals, the starting material‐iodine (I) has been purified by the sublimation method, and the PbI₂ polycrystalline by the normal freezing method. The purification effect of these methods has been confirmed by evaluating the impurity concentration in ingot by glow discharge mass spectrometry (GDMS) analysis. By comparing the purity of three different starting materials, non‐purified iodine+6N‐Pb, purified iodine+6N‐Pb and commercial 6N‐PbI₂, PbI₂ synthesized by purified iodine in the present experiment has the highest purity. This indicates that these purification methods are suitable. The present research results are expected to prepare high‐resistivity PbI₂ used in radiation detector. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)