Physicochemical and photocatalytic activities of self-assembling TiO2 nanoparticles on nanocarbons surface

TiO₂ nanoparticles were self-assembled on three different dimensional nanocarbon (SWCNT, C₆₀ and graphene) surfaces by a uniform thermal reaction. The effective anchoring of TiO₂ nanoparticles on the nanocarbon surfaces was characterized by FT-IR, XRD, XPS, TEM, Raman spectroscopy, PL and UV-Vis. By investigating the effect of different carbon nanostructures on TiO₂ photocatalyst system, we found that the enhancing photocatalytic activities of nanocarbon/TiO₂ (NT) nanocomposites have still related to great adsorbability and effective charge transfer by nanocarbon introduced, however, no more insights can be provided for peculiar properties on different nanostructures, although graphene by itself has an excellent structure and morphology.     

Naphthalene-based fluorophores: Synthesis characterization, and photophysical properties

U-type, 1,8-diarylnaphthalenes and 1,8-diarylethynylnaphthalenes were synthesized and their structures were characterized by spectroscopic methods. Emission performance of these compounds with donor and acceptor was largely depended upon the solvent polarity and environmental acidity, which implied that they might be used as solvent polarity sensors or pH sensors as well. Moreover, some 1,8-diarylnaphthalenes exhibited aggregation-induced emission enhancement (AIEE) based on their photophysical investigation and might be used as light emitting materials for optoelectronic applications.     

Preparation, optical properties, magnetic properties and thermal stability of core-shell structure cobalt/zinc oxide nanocomposites

Cobalt nanoparticles coated with zinc oxide can form composite spheres with core-shell structure. This coating process was based on the use of silane coupling with agent 3-mercaptopropyltrimethoxysilane (HS-(CH₂)₃Si(OCH₃)₃, MPTS) as a primer to render the cobalt surface vitreophilic, thus it renders cobalt surface compatible with ZnO. X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. The morphological structure, chemical composition, optical properties and magnetic properties of the product were investigated by using transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscope and vibrating sample magnetometer (VSM). It was found that the Co/ZnO core-shell structure nanocomposites exhibited both of favorable magnetism and photoluminescence properties. Results of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that the thermal stability of cobalt/zinc oxide was better than that of pure cobalt nanoparticles.     

钨磷(硅)酸磺胺盐电荷转移配合物的合成、光谱学与抗菌活性

以钨磷(硅)酸和磺胺为原料在水相中合成了2个Keggin结构杂多酸电荷转移配合物(C6H9N2O2S)3PW12O40.6H2O(SPW12)和(C6H9N2O2S)4SiW12O40.5H2O(SSiW12)。经元素分析、红外光谱、核磁共振氢谱、热重表征,确定了标题配合物的结构组成。X射线粉末衍射表明,标题配合物具有新的物相结构,为未见文献报道的杂多化合物;紫外光谱说明,配合物中磺胺阳离子与杂多阴离子之间存在电荷转移作用;热重-差示扫描量热分析结果显示2个标题配合物失重均分4步进行,分别在272.8℃和330.4℃开始分解。抗菌实验表明,标题配合物均具有优良的抗菌活性,其中SPW12对大肠杆菌、金黄色葡萄球菌的抑菌率分别达73.28%和99.36%。     

Improved electrical and thermal properties of nickel silicides by using a NiCo interlayer

We have investigated the effects of a NiCo interlayer on the electrical and thermal properties of nickel silicide as a function of the annealing temperature. For the interlayered samples, 3 nm-thick NiCo(10 at.% Co) films are electron-beam evaporated on Si substrates, on which 27 nm-thick Ni films are deposited without breaking the vacuum. It is shown that all the samples exhibit a distinctive increase in the sheet resistance at temperatures above 900 ^°C. However, the NiCo interlayer sample produces the lowest sheet resistance at 900 ^\circC. X-ray diffraction results show that the Ni only and NiCo interlayer samples produce NiSi and NiSi₂ phases, while NiCo full samples give NiSi and Ni_1−xCo_xSi₂ phases. Scanning electron microscopy results exhibit that for all the samples, the surfaces become degraded with numerous arbitrarily-shaped spots, corresponding to areas uncovered by the silicides. The areal fractions of the silicides for the Ni only, NiCo full, and NiCo interlayer samples are about 57%, 72%, and 81%, respectively. The temperature dependence of the electrical properties of the silicide samples is explained in terms of the formation of resistive phases and the agglomeration of the silicide.     

Novel green-emitting copper(I) complexes with electron donors incorporated ligands: Synthesis, photophysical properties, and electroluminescence performances

In this paper, we explore a diimine ligand of 2-thiazol-4-yl-1H-benzoimidazole (TB) with strong electron donors in its molecule. In addition, an excess electron-donor moiety of carbazole is incorporated through an inert alkyl chain to form another diimine ligand of 1-(4-carbazolylbutyl)-2-thiazol-4-yl-1H-benzoimidazole (CTB). Their corresponding Cu(I) complexes are synthesized as well. Experimental data confirm that both the Cu(I) complexes are high-energy-emitting ones. What is more, it is found that the emitter’s photoluminescent and thermal performances can be greatly improved when active hydrogen is eliminated. Using the CTB-based Cu(I) complex as a dopant, we realize green-emitting devices with a maximum brightness of 1500 cd/m² peaking at 525 nm, and the device efficiency roll-off in these devices is largely depressed due to the shield provided by carbazole moiety.     

Synthesis and electrochemical properties of different sizes of the CuO particles

Well-dispersed cupric oxide (CuO) nanoparticles with the size from 10 to 100 nm were successfully synthesized by thermal decomposition of CuC₂O₄ precursor at 400 °C. The prepared CuO nanoparticles of different sizes used as anode materials for Li ion battery all exhibit high electrochemical capacity at the first discharge. However, with the particles size changing, an interesting phenomenon appears. That is, the larger size of the particles is, the discharge capacity of the first time smaller is, while that of the second time is larger. At the same time, the mechanism of the above phenomenon is discussed in this paper. Surprisingly, we have synthesized the copper nanoparticles with different sizes by the CuO of different sizes as the electrodes.     

Synthesis and optical properties of flower-like ZnO nanorods by thermal evaporation method

Flower-like ZnO nanorods have been synthesized by heating a mixture of ZnO/graphite powders using the thermal evaporation and vapor transport on Si (1 0 0) substrates without any catalyst. The structures, morphologies and optical properties of the products were characterized in detail by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) and Raman spectroscopy. The synthesized products consisted of large quantities of flower-like ZnO nanostructures in the form of uniform nanorods. The flower-like ZnO nanorods had high purity and well crystallized wurtzite structure, whose high crystalline quality was proved by Raman spectroscopy. The as-synthesized flower-like ZnO nanorods showed a strong ultraviolet emission at 386 nm and a weak and broad yellow-green emission in visible spectrum in its room temperature photoluminescence (PL) spectrum. In addition, the growth mechanism of the flower-like ZnO nanorods was discussed based on the reaction conditions.     

Structural phase stability,elastic parameters and thermal properties of YN from first-principles calculation

The structural phase stability, elastic parameters and thermodynamic properties of YN at normal and under high pressure are reported. The calculations are mainly performed using the full-potential linearized augmented plane wave method within the density functional theory. Both local density approximation (LDA) and generalized gradient approximation (GGA) are used to model the correlation-exchange potential. The calculated equilibrium lattice parameter and the bulk modulus show good accordance with the experimental and previous theoretical reports. The phase transition from the NaCl (B1) structure to the CsCl (B2) structure is found to occur at 131?GPa within GGA and 115?GPa within LDA. The linear pressure coefficients of the different elastic moduli being addressed here are also determined along with the mechanical and dynamical stability criteria which are shown to be satisfied for YN with B1 phase under normal conditions. Besides, the heat capacity and other thermodynamic parameters are examined and discussed versus temperature.     

Optical and electrical properties of undoped and (Mn, Co) co-doped ZnO nanoparticles synthesized by DC thermal plasma method

The undoped and (Mn, Co) co-doped ZnO nanopowders were synthesized through DC thermal plasma method. The pellets of this powder were annealed at 450, 550 and 650 °C for 1 h. Structural, chemical and optical properties of the samples were studied by XRD, SEM, EDX, UV–Vis and PL analysis. XRD spectra showed that all the samples were hexagonal wurtzite structure and as the annealing temperature increases the material becomes purer and more crystalline. It is seen that the optical band gap decreases when the ZnO is doped with manganese and cobalt. Photoluminescence intensity varies with doping because of the increment of oxygen vacancies. DC conductivity studies of the pellets were carried out at different temperatures (25–100 °C) and it was found that the activation energy for the electrical transport is high for (Mn, Co) co-doped ZnO than undoped ZnO.     

Novel polymeric potassium complex: Its synthesis,structural characterization,photoluminescence and electrochemical properties

In this paper, we obtained a novel poly(vanillinato potassium) complex (PVP) as a single crystal and characterized by analytical and spectroscopic methods. A single crystal of the PVP was obtained from the acetone solution. X-ray structural data show that crystals contain polymeric K⁺ complex of vanillin. Each potassium ion in the polymeric structure is identical and seven-coordinate, bonded to two methoxy, two phenoxy and three aldehyde oxygen atoms from four vaniline molecules. Two aldehyde oxygen atoms are bridging between potassium ions. It crystallizes in the monoclinic system, space group P2₁/c, with lattice parameters a=9.6215(10) Å, b=17.4139(19) Å, c=9.6119(10) Å, β=100.457(2)° and Z=4. Thermal properties of the PVP were investigated by TGA, DTA and DSC methods. The electrochemical properties of the complex were studied in different solvents and at various scan rates. The luminescence properties of the complex in different solvents and at different pH values have been investigated. The results show that the complex exhibits more efficient luminescence property in CH₃CN and n-butanol.     

Synthesis and characterization of new LnxSb2−xSe3 (Ln: Yb, Er) nanoflowers and their physical properties

New Ln_xSb_2−xSe₃ (Ln: Yb³⁺, Er³) based nanomaterials were synthesized by a co-reduction method. Powder XRD patterns indicate that the Ln_xSb_2−xSe₃crystals (Ln=Yb³⁺, Er³⁺, x=0.00-0.12) are isostructural with Sb₂Se₃. The cell parameters b and c decrease for Ln=Er³⁺ and Yb³⁺ upon increasing the dopant content (x), while a increases. SEM images show that doping of the lanthanide ions in the lattice of Sb₂Se₃ generally results in nanoflowers. UV-vis absorption and emission spectroscopy reveals mainly electronic transitions of the Ln³⁺ ions in case of Yb³⁺ doped nanomaterials. Emission spectra of doped materials, in addition to the characteristic red emission peaks of Sb₂Se₃, show additional emission bands centered at 955 nm, originating from the ²F_7/2→²F_5/2 transition (f-f transitions) of the Yb³⁺ ions. DSC curves indicate that Sb₂Se₃ has the highest thermal stability. The temperature dependence of the electrical resistivity of doped-Sb₂Se₃ with Yb³⁺ and Er³⁺ was studied.     

A novel deep-red-emitting iridium complex with single-peaked narrow emission band: Synthesis, photophysical properties, and electroluminescence performances

In this paper, we report a novel ligand equipped with both electron-pushing moieties and enlarged conjugation planes, 1-benzo[b]thiophen-2-yl-naphthalene-2-ol (BYNO). Using BYNO as the ancillary ligand, its corresponding Ir(III) complex of Ir(ppy)₂(BYNO) (ppy=2-phenyl pyridine) is also synthesized. An efficient deep-red emission peaking at 620 nm with a narrow emission band (full-width-at-half-maximum=65 nm) was finally observed from Ir(ppy)₂(BYNO). We discuss the photophysical properties, thermal properties, geometric and electronic structures of Ir(ppy)₂(BYNO) in detail. In addition, its electroluminescence performances are investigated and a maximum luminance of 3840 cd/m² peaking at 618 nm is achieved. All obtained data suggest that Ir(ppy)₂(BYNO) is a promising candidate for red-emitting dopants in organic light emitting diodes.     

Synthesis, characterization and electrochemical properties of poly(methyl methacrylate)-grafted-poly(vinylidene fluoride-hexafluoropropylene) gel electrolytes

A new comb-like copolymer, poly(vinylidene fluoride-co-hexafluoropropylene)-g-poly(methyl methacrylate), or [P(VDF-HFP)-g-PMMA], was successfully synthesized through grafting in situ formed PMMA to the P(VDF-HFP) backbone. The composition of the P(VDF-HFP)-g-PMMA copolymer was characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA) and elemental analysis. X-Ray diffractometry (XRD) and differential scanning calorimetry (DSC) were used to examine the reduction in crystallinity of P(VDF-HFP) due to the anchoring of PMMA segments on it. Gel electrolyte membranes based on the resulting copolymer were prepared by the Bellcore process. The ionic conductivity of Li⁺ across the membranes and the related transference number were measured. A study of the interfacial stability between Li electrode and the P(VDF-HFP)-g-PMMA gel electrolyte was also conducted to evaluate the suitability of the P(VDF-HFP)-g-PMMA copolymer in rechargeable lithium and lithium-ion battery applications.     

Charge transfer transitions in the transition metal oxides ABO4:Ln and APO4:ln (A=La, Gd, Y, Lu, Sc; B=V, Nb, Ta; Ln=lanthanide)

We have compiled and analyzed optical and structural properties of lanthanide doped non-metal oxides of the form APO₄:Ln³⁺ with A a rare earth and of transition metal oxides with formula ABO₄:Ln³⁺ with B a transition metal. The main objective is to understand better the interrelationships between the band gap energy, the O²⁻→Ln³⁺ charge transfer energy, and the Ln³⁺→B⁵⁺ inter-valence charge transfer energy. Various models exist for each of these three types of electron transitions in inorganic compounds that appear highly related to each other. When properly interpreted, these optically excited transitions provide the locations of the lanthanide electron donating and electron accepting states relative to the conduction band and the valence band of the hosting compound. These locations in turn determine the luminescent properties and charge carrier trapping properties of that host. Hence, understanding the relationship between the different types of charge transfer processes and its implication for lanthanide level location in the band gap is of technological interest.     

A study of thermal, dielectric and magnetic properties of strontium malonate crystals

Crystals of strontium malonate (SrC₃H₂O₄) were grown in silica gel by the single diffusion technique. The thermo gravimetric (TG), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) studies were carried out to investigate the thermal stability of the crystal. The dielectric behavior of the title compound crystal was investigated by measuring the dielectric parameters - dielectric constant, dielectric loss and AC conductivity as a function of four frequencies −1 kHz, 10 kHz, 100 kHz and 1 MHz at temperatures ranging from 50 to 170 °C. Results indicate that the title compound is thermally stable up to about 409 °C and is a promising low ε_r-value dielectric material. The magnetic behavior of the crystal was also explored using a vibrating sample magnetometer.     

High performance Europium(III) based emitters for electroluminescence: Synthesis,crystal structures,photophysical and electroluminescent properties

In this paper, we synthesize two 1,10-phenanline derived ligands, along with their corresponding Eu(III) complexes. Their crystal structures, photophysical characteristics, including UV–vis absorption, photoluminescence (PL), quantum yields, excited state lifetimes, and thermal stability, are discussed in detail. In addition, we also investigate their potential application in electroluminescence (EL) devices. Experimental data suggest that the two Eu(III) complexes are promising emitters for EL application: pure red emissions with a maximum EL brightness of 850 cd/m² and a maximum current efficiency of 3.67 cd/A are achieved. It is found that the elimination of active hydrogen in ligand favors most PL and EL factors, including PL quantum efficiency, thermal stability, and current efficiency, but not for maximum EL brightness. An emitter with shorter excited state lifetime leads to a higher EL brightness, regardless of its relatively lower device efficiency.     

Synthesis,spectral, thermal,optical and dielectric studies on 4-dimethylaminopyridinium picrate crystals

Single crystal of 4-dimethylaminopyridinium picrate was grown by slow evaporation solution growth method. The optical properties of the crystal were studied by using UV–vis absorption and transmittance studies. The emission spectrum indicates that the crystal shows green and red fluorescence emissions. The band gap energy of the crystal was calculated and it is found to be 2.05 eV. The thermal stability of the crystal was studied using thermogravimetry-differential thermal (TG-DTA) analyses. The thermal anomalies observed in the differential scanning calorimetry (DSC) heating and cooling cycles indicate the occurrence of a first order phase transition. FTIR spectrum was used to confirm the presence of various functional groups in the crystal. The synthesized crystal shows SHG efficiency 32 times greater than that of potassium dihydrogen phosphate (KDP). The dielectric constant and dielectric loss of the crystal decreases with increases in frequency.     

Structural,mechanical and thermal properties of some Holmium Pnictides under pressure: A theoretical approach

The high pressure structural, elastic and thermal properties of holmium pnictides HoX (X=N, P, As and Bi) were investigated theoretically by using an inter-ionic potential theory with modified ionic charge parameter. We have predicted a structural phase transition from NaCl (B₁) to CsCl (B₂)-type structure at pressure of 139 GPa for HoN, 52 GPa for HoP, 44 GPa for HoAs and 26 GPa for HoBi. Other properties, such as lattice constant, bulk modulus, cohesive energy, second and third-order elastic constants were calculated and compared with the available experimental and theoretical data. In order to gain further information the brittle behaviour of these compounds was observed. Some other properties like Shear modulus (G), Young's modulus (E), Poisson's ratio (ν), anisotropy factor (A), sound velocities, Debye temperature (θ_D) were calculated. The variation of elastic constants (C₁₁ and C₄₄) and Debye temperature (θ_D) with pressure was also presented.     

Synthesis,growth and properties of a novel organic nonlinear optical material: Benzimidazolium perchlorate

Benzimidazolium perchlorate (BDP) a novel organic nonlinear optical material has been grown by slow evaporation technique. Growth parameters such as metastable zone width and induction period were determined. The relative second harmonic generation (SHG) efficiency of the material was investigated for the first time in the literature and was found to be 1.2 times higher than that of KDP. The grown crystals were subjected to X-ray diffraction, absorption spectrum, Fourier transform infrared (FT-IR) spectroscopy, thermal behavior, CHN analysis, and micro hardness studies.