Synthesis and characterization of inorganic‐organic ZnS(aminopropane)n composite materials

The main goal of our work was the synthesis and characterization of ZnS(aminopropane)_n hybrid inorganic‐organic layered materials. The basic material of our investigation was ZnS(1,3‐dap)_1/2, (where dap denotes diaminopropane). Its crystal structure has been solved by X‐ray powder diffraction methods. This layered compound was prepared using 1,3‐diaminepropane, zinc sulphate (ZnSO₄) and tioacetamide (CH₃CSNH₂). We have also tried to obtain and characterize other materials: ZnS(1‐ap) and ZnS(1,2‐dap), where ap denotes aminopropane. But in these last two cases diffraction patterns were of much poorer quality, which prevented a full structural survey; thus we cannot directly prove that hybrid lamellar materials were obtained. All compounds were studied using X‐ray diffraction, chemical analysis, UV‐vis spectroscopy and scanning electron microscopy. Additionally, using X‐ray diffraction as a function of temperature, we obtained information about structural changes of obtained composite materials under temperature treatment. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of doped lithium aluminate nanocrystalline particles by sol‐gel method

Nanocrystalline particles of Co²⁺doped lithium aluminate (Co²⁺:LAO) and Ni²⁺‐doped lithium aluminate (Ni²⁺:LAO) were synthesized by sol–gel method. The crystalline nature and particle size of the samples were characterized by X‐ray diffraction analysis (XRD). The morphology and the presence Co²⁺ and Ni²⁺ in the synthesized samples were analyzed by scanning electron microscope (SEM) and energy dispersive X‐ray analysis (EDAX). The presences of functional groups in the samples were analyzed using FT‐IR analysis. The optical absorbance of the synthesized samples were observed using UV absorption spectral analysis. The frequency dependent dielectric behaviour of the synthesized nano materials was analyzed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetic properties and X‐ray photoelectron spectroscopy of nanocrystalline Ho3Al5O12

Nanocrystalline holmium aluminium garnet (Ho₃Al₅O₁₂) has been prepared for the first time by modified Pechini's reaction after sintering the precursor gel at 1223 K. The nanomaterial has been characterized by X‐ray diffraction (XRD), selected area electron diffraction (SAED) and high resolution transmission electron microscopy (HRTEM). The XRD pattern confirms the formation of single‐phase Ho₃Al₅O₁₂; the average size of the nanoparticles has also been determined. X‐ray photoelectron spectroscopy (XPS) has been used to study the chemical composition and bonding in the as‐prepared samples. The binding energies of core‐level electrons in Ho, Al and O in the title material have been found slightly shifted compared to the values of the respective elements. DC magnetic susceptibility has been measured in the temperature range 2 – 260 K. Low effective magnetic moment of Ho³⁺, μ_eff = 1.35 µ_B and Weiss constant have been derived from the inverse magnetic susceptibility–temperature linear plot. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of spindle‐shaped silver nanoparticles in SDS solutions

Spindle‐shaped silver nanoparticles were successfully prepared in high yield by a simple wet chemical approach using citric acid (CA) as reducant in the presence of sodium dodecyl sulfate (SDS) at room temperature. Transmission electron microscopy (TEM), UV‐vis absorption spectroscopy and X‐ray diffraction (XRD) have been used to characterize the obtained products. It is found that the spindle‐shaped architecture of siver nanoparticles is drastically influenced by the mass ratio of SDS to CA and the concentration of silver nitrate (AgNO₃). It is revealed that SDS is not as a template but as a capping agent. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and morphological studies on Mn substituted ZnO nanometer‐sized crystals

Mn substituted ZnO nanocrystals synthesized by a co‐precipitation method. X‐ray diffraction (XRD) studies confirms the presence of wurtzite (hexagonal) crystal structure similar to un doped ZnO, suggesting that doped Mn ions go at the regular Zn sites. The lattice parameters a and c are increasing with increasing Mn content. The unit cell volume increases with increasing Mn concentration, indicating the homogeneous substitution of Mn²⁺ for the Zn²⁺. The lattice distortion parameter (ε_v) is evaluated from XRD data and found that it enhances as Mn content increases. Transmission electron microscopy photographs show that the size of the ZnO crystals is in the range of 20‐50 nm. The SAED pattern confirms the hexagonal and crystalline nature of the samples which are in agreement with X‐ray analysis. The chemical groups of the samples have been identified by FTIR studies (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural Characteristics of Er Doped LiNbO3 Thin Films Grown by the Liquid Phase Epitaxy Method

Erbium (Er³⁺) doped LiNbO₃ single crystal thin films have been grown LiNbO₃ (001) substrate by the liquid phase epitaxy method. The crystallinity was determined by high‐resolution X‐ray diffraction. The lattice mismatch between Er³⁺ doped LiNbO₃ films and LiNbO₃ (001) substrate was investigated by X‐ray rocking curve analysis. Also we studied the structural characteristics of Er³⁺ doped LiNbO₃ films and surface morphology dependent on the film thickness.     

Effect of Cr doping on the structural and optical properties of ZnS nanoparticles

Zn_1−xCr_x S nanoparticles with x = 0.00, 0.005, 0.01, 0.02 and 0.03 were synthesized by chemical co‐precipitation method at room temperature for the first time. Ethylene diamine tetraacetic acid was used as stabilizer. Energy dispersive analysis of X‐rays confirmed the presence of Cr in the samples. The samples were characterized by scanning electron microscopy, X‐ray diffraction (XRD), transmission electron microscopy and optical absorption studies. XRD and selected area electron diffraction results showed that the samples of all compositions crystallized in cubic structure and the lattice parameters decreased linearly with increase in Cr content following Vegard's law indicating that the Cr ions have substituted for Zn in the ZnS lattice. The particle size estimated from XRD was in the range 6–10 nm.The optical absorption studies on the doped samples indicated that the absorption edge blue shifted with respect to those of bulk and nanocrystalline ZnS. The bandgap increased with increasing Cr concentration in a narrow range 3.81–4.03 eV. Photolumonesence studies showed blue emission with appreciable luminescence quenching with increasing Cr concentration. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

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)     

Equilibrium coefficients of co‐crystallization of M2+ ions with MgSeO4·6H2O and their dependences on various physicochemical factors

Equilibrium co‐crystallization coefficients of low amounts of M²⁺ions (M²⁺ = {Ni²⁺, Cu²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺}) with MgSeO₄·6H₂O at 25 °C have been determined. Their values are comprised in the range: 0.058 (for Cd) < k_eq < 1.57 (for Co) and depend on some physicochemical and crystal chemical properties of both: co‐crystallizing salts (MSeO₄·nH₂O) and co‐crystallizing ions (M²⁺). These dependences are sometimes such strong, that they make it possible to derive simple formulae permitting estimation of k_eq coefficients at average error not exceeding 17%. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and mechanical properties of KН2PО4 single crystals with embedded nanoparticles and organic molecules

Single crystals of KDP crystals with embedded Urea molecules and TiO₂ nanoparticles have been grown from aqueous solution by the temperature lowering method. The effect of the organic molecules and nanoparticles on the structural and mechanical properties has been studied. It has been observed that addition of Urea molecules improves laser induced damage threshold and mechanical strength of the crystal, while TiO₂ nanoparticles have the opposite effect. The structure and composition of KDP:Urea crystal are studied by three‐crystal X‐ray diffraction analysis, which reveals the existence of a correlation between the increase of the microhardness value and the change of the crystal lattice parameter. The surface features of KDP:TiO₂ crystals are analyzed by scanning electron microscopy that reveals the presence of quasi‐equidistant growth bands caused by capture of the nanoparticles. It is shown that the rise of TiO₂ nanoparticles concentration up to 10⁻⁴ wt.% and higher resulted in 3‐fold reduction of the laser damage threshold of KDP:TiO₂ relative to pure KDP in [001] and [100] crystallographic directions. It is found that microhardness and fracture toughness decrease at the nanoparticles concentration of 10⁻³ wt.% due to crack formation at crystal lattice discontinuities. The grown crystals also have been subjected to dielectric studies.     

The influence of Yb3+ concentration on Yb:YAl3(BO3)4

The Yb:YAl₃(BO₃) ₄ crystals with different Yb³⁺ doping concentration have been grown by the flux method. The lattice parameters and decomposition of the Yb:YAl₃(BO₃)₄ crystal with different Yb³⁺ doping concentration were measured by X‐ray and DTA method. The transmission and fluorescence spectra of Yb³⁺:YAl₃(BO₃)₄ crystal have been measured. The growth defects of Yb_xY_1‐xAl₃(BO₃)₄ crystals were also detected by using the chemical etching method. The results show that the ytterbium concentration influences these properties of Yb:YAl₃(BO₃)₄. As the Yb³⁺ concentration increased, the crystal lattice parameter was decreased. At high doping level, the absorption peak concerned at about 980 nm shift to short wavelength. It is also found that the perfection of Yb:YAl₃(BO₃) ₄ crystal with low Yb³⁺ doping concentration is better than that with high Yb³⁺ concentration. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Morphology control of CuO micro‐particles using Zn2+ ion and ultrasonic treatment

Novel tomato‐shaped copper oxide crystals has been prepared by a simple hydrothermal method with the presence of Zn²⁺ ion. The ultrasonic pretreatment has proved to be the key factor during the synthesis process. Scanning electron microscope, energy dispersive X‐ray spectrometry and powder X‐ray diffraction were used to characterize the microstructure and morphology of the as‐prepared products. The obtained tomato‐shaped CuO particles were constructed by nanorods with the diameter of about 20 nm. The possible growth mechanism was proposed based on the experimental results. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the Morphological Changes and Twinning of ZnS (Sphalerite) Crystallites under Hydrothermal Conditions

Morphological characteristics and twinning mechanism of ZnS crystals under hydrothermal conditions have been investigated in this paper. It was shown that under hydrothermal conditions the morphology of ZnS crystallites changes along the four‐fold axis directions, and the crystals are observed in a positive or negative tetrahedron, or in a combination of positive and negative tetrahedra depending on the growth conditions. The positive tetrahedral areas on the crystallites get larger with increase of the concentrations of OH^‐ and S^2‐ in solutions, whereas the twinned crystallites of ZnS taking an elliptic shape with (111) as composition plane are easily formed in weak basic solutions. It can be found that the morphologies of ZnS crystals are in accordance with the crystallization orientations of positive or negative coordination tetrahedra ([S‐Zn₄]⁶⁺, [Zn‐S₄]^6‐) in the crystal although, in some cases, the practical morphology could be greatly affected by growth conditions, and the twinning mechansim can be suggested based on the linkage of growth units of positive and negative coordination tetrahedra, which were formed in the solution. The present investigations further indicated that the crystal chemistry approach based on the linkage/incorporation of growth units previously proposed by us can be sucessfully applied to interpret the growth mechanisms of the crystals and to control a desirable morphology.     

Growth and characterization of large La1‐xPbxMnO3+δ (x=0.32–0.35) crystals

Large crystals of La_0.63Pb_0.37Mn O_3+δ with small La(Pb)‐ deficiency of about 0.005‐0.01 at.% were grown by high temperature solution growth method. The structure of the grown crystals was determined as rhombohedral with R‐3 space group by single‐crystal X‐ray diffractometry. The surface morphology of the crystals and the exact chemical composition was examined by scanning electron microscopy and energy dispersive X‐ray analysis methods, respectively. The IR‐transmission spectrum reveals the presence of Mn³⁺O₆‐ and Mn⁴⁺O₆‐ octahedra in the lattice of La_0.63Pb_0.37Mn O_3+δ crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical and dielectric studies on pure and Ni2+, Co2+ doped single crystals of bis thiourea cadmium chloride

Good quality single crystals of Ni²⁺, Co²⁺ ions doped Bisthiourea Cadmium Chloride (BTCC) are some of the excellent and efficient non‐linear optical materials grown from aqueous solution by slow evaporation method. The lattice parameters of the grown crystals are determined by single crystal X‐ray analysis. UV spectral analyses on these samples reveal the improved transparency of the doped crystals ascertaining the inclusion of metal ion in the lattice. FTIR spectral analysis carried out on the materials confirm the presence of functional groups. Dielectric measurements reveal that the dielectric constant of pure and doped crystals decreases with increase of frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Microscopic studies on imperfections in selected YAB single crystals

The as‐grown surface and inner structures of undoped and Nd³⁺‐, Cr³⁺‐, V³⁺‐, Ce³⁺‐, Er³⁺ and Yb³⁺ – and (Er³⁺ + Yb³⁺) – doped yttrium aluminum borate (YAB) single crystals grown from (K₂Mo₃O₁₀ + B₂O₃) flux by spontaneous crystallization or top seeded solution growth (TSSG) technique, were investigated using optical and scanning electron microscopic and analytic chemical methods. Fine and rough growth hillocks of dislocational origin, growth layers, traces of inner planar defects and foreign phase crystalline debris were found and analyzed on the as‐grown faces of crystals. Irregular grains and regular block structures and foreign phase inclusions were observed and studied in the interior of the crystals. The chemical compositions measured by energy dispersive X‐ray spectrometry on perfect and imperfect micro regions are compared with those obtained by flame atomic absorption spectrometry on bulk crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The double phosphates MIMIIPO4 (MI – Na,K; MII – Mg,Mn, Co,Ni, Zn) – synthesis from chloride melts and characterization

The particularities of the chemical interaction in systems M^IPO₃‐M^IIO(or Mn₂O₃)‐M^ICl (M^I – Na, K; M^II – Mg, Co, Ni, Zn) have been investigated at the temperature 1073 K and molar ratios P/M^x = 1 or 2 and M^ICl/(M^IPO₃ + M^IIO(or Mn₂O₃)) = 30. The conditions of formation of complex phosphates M^ІM^IIPO₄ and Na₄Ni₃(PO₄)₂P₂O₇ have been found. Influences of the nature of alkali and bivalent metals on the products composition were discussed. The advantages of chloride melts using (synthesis time reduction and temperature reducing) for preparing of complex phosphates were shown. The synthesized compounds have been characterized using the powder X‐ray diffraction, Fourier transform infrared and diffuse reflectance spectroscopies.     

Synthesis and characterization of semiconductor metal sulfide nanocrystals using microemulsion technique

The semiconductor nanocrystals ZnS, PbS, CdS and CuS were synthesized via microemulsion technique involving metal acetate, reducing agent (Na₂S) and Triton X‐100 as surfactant. Nanocrystals were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of ZnS, PbS, CdS and CuS nanocrystals were found to be 5.6 nm, 13.3 nm, 11.4 nm and 6.2 nm, respectively. Different parameters like surfactant (Triton X‐100) concentration, water‐to‐surfactant ratio (ω), precursor concentration [zinc acetate, (Zn(AC)₂], reducing agent concentration [sodium sulphide, (Na₂S)] were optimized to synthesize ZnS quantum dots.     

Synthesis of mercuric iodide and bismuth tri‐iodide nanoparticles for heavy metal iodide films nucleation

We synthesized mercuric iodide and bismuth tri‐iodide nanoparticles by suspension in octadecene, from Hg(NO₃)₂.H₂O and I₂, and from Bi(NO₃)₃.5H₂O and I₂, respectively. The best synthesis conditions were 2 h at 70‐80 °C, followed by 10 min at 110 °C for mercuric iodide nanoparticles, and 4 h at 80‐110 °C, followed by 10 min at 180‐210 °C for bismuth tri‐iodide ones. Nanoparticles were then washed and centrifuged with ether repeatedly. Compounds identity was confirmed by X‐ray diffraction (XRD) and energy dispersive spectrometry (EDS). We found shifts of the X‐ray diffraction maxima for nanoparticles of both compounds. We characterized the nanoparticles by transmission (TEM) and scanning (SEM) electron microscopy. We obtained disk‐like and squared mercuric iodide nanostructures, 80‐140 nm and 100‐125 nm in size respectively. We also obtained rounded and rod‐like bismuth tri‐iodide nanoparticles, 30‐500 nm in size. Acetonitrile and isopropanol suspensions of mercuric iodide nanoparticles, and acetonitrile suspension of bismuth tri‐iodide nanoparticles exhibited peak maxima shifts in their UV‐Vis spectra. We synthesized for the first time mercuric iodide and bismuth tri‐iodide nanoparticles by the suspension method, although we have not yet obtained uniform shape and size distributions. They offer interesting perspectives for crystalline film nucleation and for improving current applications of these materials, as well as for opening new ones. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of simonkolleite nanodisks and their conversion into ZnO nanostructures

Simonkolleite (Zn₅(OH)₈Cl₂·2H₂O) nanodisks with a width of 40 nm have been successfully synthesized via a hydrothermal method using zinc chloride and ammonia as the starting materials. The conversion mechanisms from simonkolleite nanodisks to ZnO spindles under hydrothermal condition and to ZnO nanotablets under solid phase transformation were discussed respectively. The simonkolleite nanodisks obviously occur in hydrothermal system with the combination of a lower alkalinity, lower temperature (<363 K), a higher NH₄⁺ ions concentration and in existence of Cl^‐ anion. The morphologies, crystal phases and photoluminescence properties of as‐synthesized samples were investigated by field emission scanning electron microscopy, powder X‐ray diffractometer and fluorescence spectrophotometer. The photocatalytic activities of these as‐synthesized samples in the degradation of methyl orange have been demonstrated. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)