Organic–inorganic hybrid materials crystallized in noncentrosymmetric (NCS) structures have been receiving considerable attention due to their fascinating physical properties and promising applications. Herein, bulk single crystals of an NCS organometallic compound, MnHg(SCN)4 (MMTC), are grown via a temperature lowering method. The grown crystals present negative uniaxial characteristics with large birefringence, good optical homogeneity and high thermal conductivities. In addition, their Raman scattering properties are measured using spontaneous Raman spectroscopy, which show that the MMTC crystal exhibits a large Raman shift (2148.1 cm−1), narrow line-width (4.468 cm−1) and high Raman gain coefficient (1.753 times higher than that of crystalline YVO4). Moreover, the direct current conductivity, dielectric, and piezoelectric constants of MMTC are also measured, which display that the crystal also possesses a strong piezoelectric response of d15 = 22.7 pC N−1. Furthermore, structure property relationships are discussed on the basis of the structure of the crystal. As a multi-functional crystal, MMTC is a particularly promising candidate for stimulated Raman scattering in the visible and near-infrared regions and piezoelectric applications at room temperature.

MgO nanofiber with good morphology was difficult to obtain through high temperature heat-treatment due to the widely existed pulverization phenomenon, which restricted its applications in the high-temperature field. In this work, MgO nanofibers were prepared by electrospinning through mixed precursors: magnesium acetate (MA) and magnesium citrate (MC). The fiber with MC mass content in the range of 30–50% exhibited good high-temperature stability and the original feature was preserved after heat-treated at 1000 °С. A plausible formation mechanism of the polycrystalline MgO nanofibers was provided in the present paper. Suitable confection of MA and MC brought a milder decomposition process and led to a more compact structure of MgO nanofiber, which contributed to the excellent high-temperature stability. The considerable effects of microstructure on thermal conductivity of the fiber were discussed. The method in this paper has greatly expanded the solution scope for preparing electrospun fibers with expectation of structure modification and strength enhancement.

•The prepared mesoporous zirconia fibers with continuous fibers morphology, large surface area and ordered pore structure.•We discovered that the water steam can promote the crystallization of zirconia and prevent the pore structure collapse.•Through modifying the solution pH value, we were able to effectively enhance the surface area of mesoporous fibers.•Our findings in this study will provide a new guidance for the design and fabrication of mesoporous zirconia fibers.•The prepared mesoporous zirconia fibers showed an excellent adsorption capacity for Congo red.Highly crystalline mesoporous zirconia fibers with high surface area have been prepared by the use of electrospinning combined with precursors method. The obtained precursor fibers were treated in water steam and directly in air at different temperature respectively. Compared with the direct calcination in air, the water steam cannot only promote the crystallization of ZrO2 but also effectively remove off the organics and prevent the pore structure collapse. Moreover, through adding hydrochloric acid to modify the solution pH value, the obtained t-ZrO2 fibers treated in water steam at 300 °C have high surface area and large pore volume of 232.70 m2 g−1 and 0.36 cm3 g−1. The formation mechanism of the mesostucture was studied and the schematic was represented. Compared with the previous reports of mesoporous ZrO2 fibers, the as-synthesized materials exhibited the high crystallinity, large surface area and the long-range order mesostructure.The adsorption of Congo red indicates that the samples have a high adsorption capacity of 103.46 mg g−1 and long-periodic repeated availability.Download high-res image (94KB)Download full-size image

The present study fully reports the decomposition of polyacetylacetonatozirconium (PAZ) in air with thermogravimetry–differential scanning calorimetry and Fourier transform infrared spectroscopy. The influence of water vapor on the decomposition of PAZ was characterized with the Fourier transform infrared spectroscopy. Crystallization and phase transformation of PAZ were studied by X-ray diffraction and Raman spectroscopy. The experimental results show that water vapor promotes the decomposition of PAZ and crystallization of zirconia compared with air. Furthermore, the effect of different amount of stabilizer Y(NO3)3·6H2O on the pyrolysis and phase stabilization of PAZ shows that NO3− was beneficial to the oxidation of organic components and the formation of Y2O3 could stabilize tetragonal zirconia and hinder grain growth.

•Growth habits of ZCTC been investigated photographically by means of micro-crystallization method, and bulk crystals with dimensions of 51 × 15 × 12 and 28 × 13 × 12 mm3 were obtained by the solvent-evaporation method.•The two-dimensional nucleation growth mechanism and crystal twinning defect of ZCTC crystal were discovered for the first time.•The relative dielectric constants and elastic compliance constants were determined. Meanwhile first-principles calculation was used to calculate elastic constants.•The thermal diffusivities and thermal conductivities were obtained.Bulk single crystals of zinc cadmium thiocyanate, ZnCd(SCN)4 (ZCTC) with dimensions of 51 × 15 × 12 and 28 × 13 × 12 mm3 have been obtained. Growth habits were investigated, two-dimensional nucleation growth mechanism and crystal twinning defect were observed from the as-grown crystals. The thermal diffusivities were measured, and then thermal conductivities were calculated with values decreasing from 1.3683 to 0.8739 W⋅m−1⋅K−1 and 0.8496 to 0.5356 W⋅m−1⋅K−1 as the temperature increasing from 303 to 423 K, along the a- and c-directions, respectively. The relative dielectric constants and elastic compliance constants at room temperature were determined. Meanwhile, first-principles calculation was used to calculate elastic constants.Download high-res image (73KB)Download full-size image

•Two novel precursor fibers were prepared, which were continuous.•The crystalline phase of TiO2 fibers is anatase.•The diameters of TiO2–PAT and TiO2–PET fibers are 2–5 and 10–20 μm, respectively.•The grains of TiO2 fibers tend to pack closely together.•The TiO2 fibers exhibit fine photocatalytic degradation activities.Two novel precursor fibers named polyacetylacetonatotitanium (PAT) and polyacetictitanium (PET) were prepared by a sol–gel method combined with dry-spinning technique. Polycrystalline TiO2 fibers were successfully obtained from the two precursor fibers after sintering at 500 °C with steam treatment. Both PAT and PET fibers were easily collected. PAT fiber is light yellow and transparent. PET fiber is yellowish white and translucent. The crystalline phase of TiO2 fibers is anatase and the diameters are 2–5 μm (TiO2–PAT) and 10–20 μm (TiO2–PET). Meanwhile, the grains of the fibers tend to pack closely together and the diameter of the pores in the fibers is several nanometers. The TiO2 fibers exhibit better photocatalytic degradation activities compared with P25.

Bulk single crystals of CdHg(SCN)4(C2H6SO)2 (CMTD) have been grown by the temperature-lowering method. Refractive index measurements reveal that the refractive index nx along the c axis is much smaller than the ny and nz indices in the ab-plane. The detailed powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate that the crystal is a phase matchable nonlinear optical material which exhibits a strong SHG effect, 1.2 times that of KTiOPO4. The complete set of dielectric, elastic and piezoelectric constants of CMTD have been measured and the results show that the crystal possesses excellent piezoelectric properties of d36 = 20.40 and d14 = 17.80 pC N−1 (much larger than those of α-SiO2). The crystal exhibits a neutral layered structure consisting of the asymmetric HgS4 tetrahedron and CdN4O2 octahedron which are connected by π-conjugated –SCN– ligands. The physical properties have been interpreted on the basis of the crystal structure combined with theoretical calculations. The strong piezoelectric response and high optical SHG efficiency make CMTD a promising candidate for both piezoelectric and nonlinear optical applications.

Bulk single crystals of diguanidinium phosphate monohydrate (G2HP) with dimensions up to 55 × 28 × 27 mm3 have been grown by solution growth methods. Thermal properties including specific heat, thermal conductivity and thermal expansion were investigated as a function of temperature. The specific heat was measured to be 1.339 to 1.614 J g−1 K−1 over the temperature range of 293 to 347 K. The thermal conductivities are descending as the temperature increases. The average linear thermal expansion coefficients along a and c axes from 298 to 338 K are α11 = 1.878 × 10−5 K−1 and α33 = 1.930 × 10−5 K−1, respectively. The laser-induced damage threshold measurements show that the G2HP crystal possesses an excellent resistance to laser radiation with a high threshold up to 5.29 GW cm−2. The optical behaviors, including the transmission spectrum and reflective indexes, were investigated to study its linear and nonlinear optical properties. The results reveal that the crystal is a phase matchable nonlinear optical material in the visible and UV regions. A complete set of dielectric, elastic and piezoelectric constants of G2HP have also been measured, and the results display that the crystal also possesses fine piezoelectric properties with d14 = 10.00. Furthermore, the structure–property relationships are discussed on the basis of the crystal structure combined with theoretical calculations. As a multi-functional crystal, G2HP is a particularly promising candidate for a variety of potential applications in many fields.

•Two magnetic polymers based on Ni(dmit)2 have been prepared, with structures determined.•Strong antiferromagnetic exchange interaction is observed for ETPP[Ni(dmit)2].•Analysis indicate the formation of nonlinear tetramers in PTPP[Ni(dmit)2].•The first Ni(dmit)2 tetramer obtained by regular metathetical reactions.The preparation, crystal structures and physicochemical characterization of two magnetic polymers, ethyl-triphenylphosphate (ETPP) [Ni(dmit)2] (compound 1) and propyl-triphenylphosphate (PTPP) [Ni(dmit)2] (compound 2) (dmit = 2-thioxo-1,3-dithiol-4,5-dithiolate), have been described. The magnetic susceptibilities (χm) have been measured between 10 and 300 K. The χm values of 1 can be well reproduced by the sum of the contributions from a standard Curie system and a dimer with negative exchange interaction of J/k = −320.59 K, which is extremely strong among dmit complexes. The dimer formation in Ni(dmit)2 anions have been ascertained by the crystal structure analysis. In 2, every two Ni(dmit)2 dimer molecules are connected by the short side-by-side distance between sulfur atoms, indicating the formation of a nonlinear tetramer. The magnetic susceptibility data have been fitted to a four-spin model using the g value obtained in EPR spectroscopy, and ended up with a plane-to-plane interaction of J1/k = −200.89 K and a sideways interaction J2/k = −33.69 K.Two magnetic polymers based on Ni(dmit)2 have been prepared, with structures determined. A nonlinear four-spin model is successfully applied to PTPP[Ni(dmit)2], which provides the first Ni(dmit)2 tetramer obtained by regular metathetical reactions.

The preparation and crystal structure of a novel nonlinear optical organometallic crystal, benzyltriethylammonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) (BTEAADT), are described. The crystal was characterized by elemental analyses, infrared and X-ray powder diffraction spectroscopy, thermal analysis and optical absorption. A typical highly optical quality single crystal with dimensions of about 30 × 3 × 3 mm3 has been grown from an acetone solution by the solvent evaporation method. The specific heat of the crystal was measured to be 692.0 J mol−1 K−1 at 300 K. The thin film of BTEAADT doped into poly(methyl methacrylate) (PMMA) with a concentration of 1 wt% was prepared using spin-coating method. The linear properties of the thin film were investigated by a prism coupler. The third-order nonlinear optical properties of BTEAADT doped PMMA film was investigated by using the laser Z-scan technique with 20 ps pulses at 1064 nm. A large negative nonlinear refraction and no nonlinear absorption have been observed. The refractive index and the thickness of the film are 1.4682 and 1.15 μm, respectively. The nonlinear refractive index is calculated to be −3.978 × 10−15m2/W for the film. At the same time, the nonlinear absorption coefficient is 0. Two figures of merit, W and T of the film, were calculated to be |W| = 1.07 > 1, |T| = 0 << 1. All results show that BTEAADT crystal has very potential applications on all-optical switching.

Two novel single crystals, poly[bis(N,N-dimethylformamide)tetra(thiocyanato)metal(II)mercury(II)] (metal = cadmium and manganese, abbreviated as DTCM and DTMM, respectively) were prepared. The characterizations of DTCM and DTMM were performed by elemental analyses, infrared, X-ray single crystal diffraction. The two title complexes crystallized in the same monoclinic crystallographic system and P21/n space group with unit cell parameters: a = 9.2515(2) Å, b = 14.1670(3) Å, c = 16.5898(3) Å, β = 93.0320(10)°, z = 4, Dx = 2.115 g/cm3 for DTCM, and a = 9.24580(10) Å, b = 14.1110(2) Å, c = 16.4937(2) Å, β = 92.9120(10)°, z = 4, Dx = 1.960 g/cm3 for DTMM, respectively. The two structures are isostructural. The thermal decomposition processes of the two crystals were investigated by means of thermogravimetric analysis and differential thermal analysis measurements in air.

Magnesium oxide (MgO) fibers were prepared through centrifugal spinning combined with a citrate precursor method. The strategy is quite efficient that the fibers could be obtained in large scale. The morphology, microstructure and crystal phase of the obtained MgO fibers were characterized by digital camera, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The results showed that the fibers present continuous morphology with an average diameter of 8 µm. Cubic MgO grains with the size of ca. 50 nm were closely packed in the body of the fibers. MgO fiber-board and fiber-cylinder were fabricated through injection molding of fiber slurry and exhibited promised mechanical performance investigated by compressive strength measurement.

High optical quality single crystals of a nonlinear optical material, manganese mercury thiocyanate, MnHg(SCN)4 (MMTC), with dimensions up to 21×14×13 mm3 have been grown by the solvent evaporation method. The growth habit of MMTC crystal crystallized under different conditions was investigated by means of micro-crystallization method. Two typical growth morphologies of the crystal were indexed and compared with the morphology deduced from the single crystal structure data. The results show that two novel {1 0 0} and {1 1 2} facets appear during the crystal growth. Powder second harmonic generation and spectral transmittance measurements were also performed. The results indicate that MMTC is phase-matchable and the UV transparency cutoff occurs at 373 nm. Various defects were found in MMTC crystal. Their formation mechanisms and the methods to eliminate these defects are discussed.

A novel organometallic third-order nonlinear optical crystal: ethyltriphenylphosphonium bis(2-thioxo-1,3-dithiole-4,5-dithiolato)aurate(III) (ETPPADT) has been prepared, and large optical-quality single crystals have been grown by the solvent evaporation method. Its structural, optical and physicochemical properties are characterized by elemental analyses, UV–Vis–NIR transmission, infrared spectroscopy and thermal analysis. The thin films of ETPPADT doped into poly(methyl methacrylate) (PMMA) with a concentration of 1 wt% have been prepared using spin-coating method. The linear refractive index and the thickness of the thin films were measured by a prism coupler. The third-order nonlinear optical properties of the films have been investigated using Z-scan technique at the wavelength of 1064 nm with laser duration of 20 ps, which reveal that the composited films exhibit large negative nonlinear refractive indices about 4×10−10 esu and no nonlinear absorption. The influence of thickness of the film and the incident laser intensity on the third-order optical nonlinearities have been investigated. Two figures of merit, W and T, have been calculated to be |W|≅120⪢1 and |T|=0⪡1, respectively. All the results show that ETPPADT crystal has potential application on all-optical switching.

Magnesium oxide (MgO) fibers were prepared by sol-gel method with magnesium propionate as precursor. Pure micrometer-sized MgO fibers were obtained after pretreated in two different atmospheres (water steam and air). The structure diagram of magnesium propionate precursor was achieved by analyses of the precursor fibers. The MgO fibers pretreated in different atmospheres were characterized by the use of XRD, FT-IR, TG-DSC and SEM analytical techniques, and the heat-conducting property of fibers was characterized by thermal conductivity test. The results show that Mg(OH)2 crystalline phase appeared at the temperature range from 300 °C to 400 °C during the heat-treating process in water steam. They also show that the water steam is beneficial for the removal of organics, the crystallization of the fibers and the formation of dense, smooth and crack free fibers, but leads to the increase of the heat-conducting property of MgO fibers.

Organic–inorganic hybrid materials crystallized in noncentrosymmetric (NCS) structures have been receiving considerable attention due to their fascinating physical properties and promising applications. Herein, bulk single crystals of an NCS organometallic compound, MnHg(SCN)4 (MMTC), are grown via a temperature lowering method. The grown crystals present negative uniaxial characteristics with large birefringence, good optical homogeneity and high thermal conductivities. In addition, their Raman scattering properties are measured using spontaneous Raman spectroscopy, which show that the MMTC crystal exhibits a large Raman shift (2148.1 cm−1), narrow line-width (4.468 cm−1) and high Raman gain coefficient (1.753 times higher than that of crystalline YVO4). Moreover, the direct current conductivity, dielectric, and piezoelectric constants of MMTC are also measured, which display that the crystal also possesses a strong piezoelectric response of d15 = 22.7 pC N−1. Furthermore, structure property relationships are discussed on the basis of the structure of the crystal. As a multi-functional crystal, MMTC is a particularly promising candidate for stimulated Raman scattering in the visible and near-infrared regions and piezoelectric applications at room temperature.

Bulk single crystals of CdHg(SCN)4(C2H6SO)2 (CMTD) have been grown by the temperature-lowering method. Refractive index measurements reveal that the refractive index nx along the c axis is much smaller than the ny and nz indices in the ab-plane. The detailed powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate that the crystal is a phase matchable nonlinear optical material which exhibits a strong SHG effect, 1.2 times that of KTiOPO4. The complete set of dielectric, elastic and piezoelectric constants of CMTD have been measured and the results show that the crystal possesses excellent piezoelectric properties of d36 = 20.40 and d14 = 17.80 pC N−1 (much larger than those of α-SiO2). The crystal exhibits a neutral layered structure consisting of the asymmetric HgS4 tetrahedron and CdN4O2 octahedron which are connected by π-conjugated –SCN– ligands. The physical properties have been interpreted on the basis of the crystal structure combined with theoretical calculations. The strong piezoelectric response and high optical SHG efficiency make CMTD a promising candidate for both piezoelectric and nonlinear optical applications.