Shape-selected synthesis, characterization and optical properties of KMnF3 micropolyhedra, microspheres and hollow microspheres

Micropolyhedra, microspheres and hollow microspheres of the cubic KMnF₃ were selectively prepared by controllable, hydrothermal method at 120 °C. Manganese acetate and potassium fluoride were employed as the starting materials in the reaction, and variety of polyethylene glycol and dosage of citric acid were demonstrated to be responsible for the shape evolution. The samples were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra, UV-vis absorption spectroscopy and photoluminescence spectra. A possible mechanism for the growth of KMnF₃ microcrystal was proposed.     

Bulk size crystal growth,spectral, optical,luminescence, thermal,mechanical, and dielectric properties of organic single crystal

Single crystal of 2-[2-(4-methoxy-phenyl)-vinyl]-1-methylstilbazolium iodide (4MESI) was grown by the slow evaporation method. Single-crystal X-ray diffraction analysis reveals the formation of the title crystal. The density of the grown crystals was measured, and it was compared with theoretically calculated value. The FTIR and powder XRD of 4MESI were performed at room temperature. The different types of proton present in the crystal structure have been confirmed by NMR spectroscopic study. UV–Vis–NIR spectral studies reveal that 4MESI crystals are good optical transparency in the entire visible region. The photoluminescence spectrum of 4MESI shows violet and blue emission. Thermal stability and behavior of the grown crystal have been investigated by TG and DTG analysis. It shows that the grown crystal has melting point at 243 °C. Mechanical hardness of the grown crystals was estimated by Vickers microhardness tester. The grown crystals were also characterized by chemical etching and dielectric studies, and the results are discussed in detail.     

Effect of current density on morphological,structural and optical properties of porous silicon

The morphology of porous silicon (PS) layers produced by electrochemical etching of n-type (100) silicon (Si) at different low current densities was studied using SEM, image J analysis and WSxM software. From FTIR spectroscopy analysis, the Si dangling bonds of the as-prepared PS layer have large amount of Hydrogen to form weak Si–H bonds. From Raman analysis, a full width half maximum (FWHM) of the Raman peak was gradually increased with increased current density, shifted towards lower energies due to reduce of crystallite size, the crystallite size in the PS varied from 63 nm to 20 nm depending on the current density. The optical response of the PS layer has been performed by the absorbance and Photoluminescence was studied experimentally in the visible range. The optical absorption and photo luminescence in PS is due to excitonic recombination between the defect states as well as on the surface of nanocrystals, and this was attributed to the presence of silicon hydride species which are confirmed by FTIR spectra. The red shift was observed in absorbance and Photoluminescence due to decrease in the size of Si crystallites and growth of Si=O bonds. The contact angle varied from 76° to 120.1°. From the wettability studies, the surface nature of the PS was converted from hydrophilic to hydrophobic when the current density increased.     

Synthesis, growth, optical, mechanical, dielectric and thermal properties of 4-chloro-4'-chlorobenzylidene aniline single crystal

The organic material 4-chloro-4′-chlorobenzylidene aniline (CCBA) was synthesized and confirmed by NMR and FTIR spectral analyses. CCBA crystal was grown from chloroform by slow evaporation at room temperature and the single crystal cell parameters were determined by single crystal X-ray diffraction method. The perfection of the grown crystal was analyzed by high resolution X-ray diffraction rocking curve analysis. Fluorescence spectrum indicated violet emission at 428 nm. The range of optical absorbance was ascertained by recording UV–vis–NIR spectrum. Load dependant microhardness measurements on this crystal revealed the mechanical behavior of the material. Stiffness constant, Meyer index and yield strength of CCBA crystal were calculated. Dielectric studies were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 100 Hz to 100 kHz. The thermal behavior of CCBA was investigated using differential scanning calorimetry (DSC) and no phase transition was identified in the temperature region 30–100 °C. Further, the CCBA crystal was subjected to open aperture Z-scan studies in order to investigate the third order nonlinear optical (NLO) properties of CCBA crystal.     

Synthesis,crystal structure,photoluminescence properties of organic-inorganic hybrid materials based on ethylenediamine bromide

In this work, a new orthorhombic organic-inorganic hybrid single crystal (C₂H₁₀N₂)₂MnBr₄.2Br with-Zero-dimensional structure was synthesized by slow evaporation method at 75 °C. The crystal structure and intermolecular interactions were performed by single crystal X-ray diffraction and Hirshfeld surface. Optical properties of (C₂H₁₀N₂)₂MnBr₄.2Br were systematically studied by Raman, infrared spectrum, UV–vis, photoexcitation spectra, and photoluminescence spectra. The optical band gap (E_g = 2.61 eV) were calculated from the absorption spectra of (C₂H₁₀N₂)₂MnBr₄.2Br. This hybrid materials also had shown good thermal stability (decomposition temperature: 288–660 °C). Finally, photoluminescence measurements showed a strong excitation line at 362 nm and a strong fluorescence at 537 nm which makes it a promising material in luminescence field.     

Additive assisted hydrothermal synthesis,characterization and optical properties of one dimensional DyPO4:Ce3+ nanostructures

One dimensional nanostructures of cerium doped dysprosium phosphate (DyPO₄:Ce³⁺) were synthesized via hydrothermal route in the presence of different surfactants [sodium dodecyl sulfate (SDS), dodecyl sulfosuccinate (DSS), polyvinyl pyrollidone (PVP)] and solvent [ethylene glycol and water]. The prepared nanostructures were characterized by Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FE-SEM), Transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), UV-VIS-NIR absorption spectrophotometer and photoluminescence (PL) studies. The PXRD and FTIR results indicate purity, good crystallinity and effective doping of Ce³⁺ in nanostructures. SEM and TEM micrographs display nanorods, nanowires and nanobundles like morphology of DyPO₄:Ce³⁺. Energy-dispersive X-ray spectra (EDS) of DyPO₄:Ce³⁺nanostructures confirm the presence of dopant. UV-VIS-NIR absorption spectra of prepared compounds are used to calculate band gap and explore their optical properties. Luminescent properties of DyPO₄:Ce³⁺ was studied by using PL emission spectra. The effect of additives and solvents on the uniformity, morphology and optical properties of the nanostructures were studied in detail.     

Structural,thermal, dielectric and optical behaviour investigations of water-free ZnO/lyotropic liquid crystal nanocolloids

ABSTRACT

Zinc oxide (ZnO) nanoparticles of spherical symmetry (average size of ≈ 20 nm) have been synthesised via a non-aqueous lyotropic liquid crystalline (LLC) templating process. Lyotropic liquid crystalline nanocolloids are prepared via dispersing 0.05, 0.1 and 0.5 wt.% ZnO nanoparticles in non-aqueous lyotropic phase. No structural phase change has been seen with the doping of nanoparticles as stable lamellar phases are observed in all the cases. Stability of the lamellar structure and orientation of the ZnO nanoparticles in the liquid crystalline matrix may be attributed to the interfacial surface charge interactions. A significant increase and pronounced dispersion in dielectric permittivity of the ZnO/LLC nanocolloids could be the result of parallel coupling among guest/host, higher dipole- moment of the ZnO nanoparticles and Maxwell-Wagner polarisation. The variation of relaxation parameters has also been discussed and correlated with the dielectric and structural parameters. ZnO/lyotropic nanocolloids devices exhibit dc conductivity of the order of 10^?5S/m owing to the increase in the number of ions (of the order of 10¹⁹m^?3) in the doped systems. Nanocolloids exhibits, the refractive index of range 1.40 to 1.45 and the wide bandgap of the range 4.1–4.5 eV.     

Recent advances of lead-free metal halide perovskite single crystals and nanocrystals: synthesis,crystal structure,optical properties,and their diverse applications

Lead halide hybrid perovskites have received massive research attention because of their unique inherent photophysical properties that driven them for potential application in the fields of photovoltaics, light-emitting devices, lasing, X-ray detector, and so on. Perovskite single crystals and nanocrystals are generally synthesized via various low-cost solution-processed techniques. The emergence of simple growth approaches of perovskite structures enable to fabricate low-cost and highly efficient devices. However, toxicity of Pb atoms and instability of perovskite structures obstruct further commercialization of these technologies. Recent efforts have been shifted to discover novel, eco-friendly, and stable lead-free metal halide perovskite (LFHP) materials and exploring their different growth processes for various device applications. This review aims to provide an up-to-date analysis of recent progress report on LFHPs and will mainly focus on their growth processes in the single crystalline and nanocrystalline forms. This review also tries to understand how the perovskite crystal structure impacts on their fundamental properties. In addition, we discuss the current progress in various field of applications and their future aspects.     

Impact of silica nanoparticles dispersion on the dielectric and electro-optical properties and absorption spectra of host ferroelectric liquid crystal

The present work concerns with the investigation of the effect of dispersion of Silica (SiO₂) nanoparticles (NPs) in host ferroelectric liquid crystal (FLC) KCFLC10S on the dielectric and electro-optical properties and ultraviolet-visible (UV-VIS) absorption spectra of the pristine and dispersed systems. We have found that the dispersion of SiO₂ NPs in the host FLC strongly influences the various properties of dispersed systems. No evidence of aggregates and clumps in the dispersed system has been observed. Due to SiO₂ NPs dispersion, a rapid decrease in dielectric permittivity ε’, increase in conductivity σ with frequency, increase in spontaneous polarisation P_s and decrease in switching time with bias voltage have been observed. Based on the absorption spectra, we have also made an attempt to link the electro-optical and dielectric response with the mechanism of FLC–NPs interactions.     

Studies on the growth, optical, electrical and spectral properties of potassium pentaborate (KB5) single crystals

The bulk single crystals of nonlinear optical material potassium pentaborate (KB5) have been grown by slow evaporation solution growth technique using water as solvent. The grown crystal was confirmed by single crystal X-ray diffraction studies. The structural perfection of the grown crystals has been analyzed by high resolution X-ray diffraction (HRXRD) studies by recording rocking curve. The photoluminescence (PL), UV-vis spectral studies were performed and the optical bandgap of the material was calculated. FTIR and FT-Raman measurements enumerate the functional groups present in the compound. The factor group analysis on KB5 reveals that there are 117 vibrational optical modes. The dielectric behavior of KB5 was investigated with different frequencies and temperatures.     

Characterization,optical and thermal properties of new azomethines based on heptadecafluoroundecyloxy benzaldehyde

New thermotropic liquid crystals containing a long alkoxysemiperfluorinated chain (-O-(CH₂)₃-(CF₂)₇-CF₃), one linking unit in mesogenic cores (HC=N-) and different functional end-groups such as 4-hexadecyl-, 4-n-hexadecyloxy- chain, or biphenyl-4-carbonitrile, 4-diazenyl-N,N-dimethylbenzene or pyren were synthesized via a one-step route. The methods of nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), ultraviolet–visual (UV-vis) and photoluminescence (PL) spectroscopy as well as differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) were used. The absorption (UV-vis) and PL features of all compounds are documented. The amine had an effect on the mesomorphic properties of the azomethines. An enantiotropic smectic phase was observed for all of the systems studied. As a result of DSC and POM investigations, it is shown that liquid crystalline properties of the azomethines exhibit a strong dependence of the end-groups. The mesomorphic behaviour of the compounds was investigated also by FTIR(T) and UV-vis(T) spectroscopy. Current–voltage measurements were performed on an ITO/compound/Alq₃/Al device.     

Synthesis,spectroscopic, thermal,crystal structure properties and characterization of new Hofmann-type-like clathrates with 4-aminopyridine and water

In this study, synthesis of two new heteronuclear tetracyanonickelate(II) clathrates based on 4-aminopyridine (4AP) and guest water (H₂O) molecule and investigation of their structural properties were reported. These clathrates were characterized by using vibration spectroscopy, elemental, thermal analysis and single crystal X-ray diffraction (SC-XRD) techniques. Examining the elemental and spectral data of these clathrates, it was observed that the formulas [Zn(II)(4AP)₂Ni(µ-CN)₂(CN)₂]·6H₂O and [Cu(II)(4AP)₄Ni(µ-CN)₂(CN)₂]·H₂O were defined their structures. General information about the structural properties of these clathrates in single crystal form has been obtained by considering the changes in the characteristic peaks of the cyanide group and the 4AP that formed them. The thermal behaviors of these clathrates were obtained by examining the temperature-dependent changes of their masses. The magnetic susceptibilities of these clathrates in single crystal form were measured with a Gouy balance. According to the data obtained using SC-XRD technique, the heterometallic [Zn(II)(4AP)₂Ni(µ-CN)₂(CN)₂]·6H₂O compound has Cmcm and the heterometallic [Cu(II)(4AP)₄Ni(µ-CN)₂(CN)₂]·H₂O compound has crystal structures in the C2 / c space group.     

Phase and state transition effects on dielectric, mechanical, and thermal properties of polyols

The present study investigated the glass transition, crystallisation and melting behaviour of erythritol, xylitol, and glucitol (sorbitol) using dielectric analysis (DEA), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). Sorbitol and xylitol were plasticised by water and their glass transition temperatures decreased when water content was increased. Erythritol crystallised rapidly, and its water plasticisation behaviour could not be determined. Melting of the crystalline polyols occurred at their specific melting temperatures. Melts of erythritol and xylitol crystallised on recooling and no glass transition was apparent on reheating. Quench cooled sorbitol melt remained amorphous and showed a glass transition on reheating. Glass transition and crystallisation were apparent in the DSC thermogram and the dielectric and the dynamic mechanical spectra of mixtures of amorphous and crystalline xylitol.     

Effect of dispersed phase composition on morphological and mechanical properties of PET/EVA/PP ternary blends

Immiscible ternary blends of PET/EVA/PP (PET as the matrix and (PP/EVA) composition ratio = 1/1) were prepared by melt mixing. Scanning electron microscope results showed core‐shell type morphology for this ternary blend. Binary blends of PET/PP and PET/EVA were also prepared as control samples. Two grades of EVA with various viscosities, one higher and the other one lower than that of PP, were used to investigate the effect of components' viscosity on the droplet size of disperse phase. The effect of interfacial tension, elasticity, and viscosity on the disperse phase size of both binary and ternary blends was investigated. Variation of tensile modulus of both binary and ternary blends with dispersed phase content was also studied. Experimental results obtained for modulus of PET/EVA binary blends, showed no significant deviations from Takayanagi model, where considerable deviations were observed for PET/PP binary blends. Here, this model that has been originally proposed for binary blends was improved to become applicable for the prediction of the tensile modulus of ternary blends. The new modified model showed good agreement with the experimental data obtained in this study. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 251–259, 2010     

Effect of styrene-4-vinyl pyridine diblock copolymer on morphological,thermal, and mechanical properties of poly(2,6-dimethyl-1,4-phenylene ether)/polyethylene ionomer blends

The compatibilizing effects of a styrene-4-vinyl pyridine diblock copolymer on the properties of immiscible poly(2,6-dimethyl-1,4-phenylene ether) (PPE)/polyethylene ionomer (Surlyn) blends are investigated by examining the phase morphology and the thermal and mechanical properties. The block copolymer is synthesized by sequential anionic polymerization at ?78°C and melt-mixed with PPE and Surlyn at 290°C. When a small amount of block copolymer is present, the domain size of the dispersed phase becomes smaller. The tensile strength and elongation at break increase with addition of the block copolymer for PPE-rich matrix blends, whereas the tensile strength increases but the elongation at break decreases for Surlyn-rich matrix blends. These effects are interpreted in terms of the interfacial activity and the reinforcing effect of the block copolymer. From the experimental results, it is concluded that the block copolymer plays a role as an effective compatibilizer for PPE/Surlyn blends. © 1994 John Wiley & Sons, Inc.     

Influences of template concentration and epoxy functionality on porous epoxy systems: Characteristics of thermal stability, optical, dielectric, and mechanical properties

Two different multi-porous epoxy thermosets (MPETs), bi-functionality of DGEBA and tri-functionality of TGTPM, were prepared foremost for the interaction of template concentration and epoxy functionality under several physical properties. By performing an automated mercury porosimeter test, we found out template concentration was critical to the amount of voids/pores. Meanwhile, epoxy functionality decided the formation of porous structure through SEM. Comparing with TGTPM MPETs system, the DGEBA MPETs system with 20 wt% template displayed appreciable T_g and tan δ properties while the phenomenon exhibited higher thermal stability property. Additionally, thermal conductivity patterns show the DGEBA MPETs system is a remarkable material of thermal resistance. However, it reduces optical clarity, dielectric permittivity and mechanical strength according to the UV-visible spectroscopy, LCR meter, and DMA, normally. Therefore, we can understand that template concentration and epoxy functionality are key factors of physical degradation and stability in porous epoxy materials.     

Effect of electron beam irradiation on dynamic mechanical,thermal and morphological properties of LLDPE and PDMS rubber blends

The effect of electron beam irradiation on the blends of linear low-density polyethylene (LLDPE) and poly dimethyl siloxane rubber (PDMS) prepared over a wide range of compositions starting from 70:30 to 30:70 (LLDPE: PDMS) by varying the radiation doses from 50 to 300 kGy has been studied. The dynamic modulii and dielectric strength of the blends increase on irradiation at 100 kGy as compared to that for the unirradiated blends. Degree of crystallinity and melting behaviour remain unchanged upon irradiation upto a dose of 100 kGy, beyond which it decreases. Thermal stability increases with increase in the proportion of PDMS rubber in the blend as well as on irradiation at 100 kGy. The phase morphology of the blends examined under the SEM exhibit two phase morphology before electron beam irradiation, whereas single phase morphology is observed after electron beam irradiation due to intra- as well as inter-molecular crosslinking leading to a miscible system.     

Synthesis, crystal and band structures, and optical properties of a new lanthanide-alkaline earth tellurium(IV) oxide: La2Ba(Te3O8)(TeO3)2

A new quaternary lanthanide alkaline-earth tellurium(IV) oxide, La₂Ba(Te₃O₈)(TeO₃)₂, has been prepared by the solid-state reaction and structurally characterized. The compound crystallizes in monoclinic space group C2/c with a=19.119(3), b=5.9923(5), c=13.2970(19) Å, β=107.646(8)°, V=1451.7(3) Å³ and Z=4. La₂Ba(Te₃O₈)(TeO₃)₂ features a 3D network structure in which the cationic [La₂Ba(TeO₃)₂]⁴⁺ layers are cross-linked by Te₃O₈⁴⁻ anions. Both band structure calculation by the DFT method and optical diffuse reflectance spectrum measurements indicate that La₂Ba(Te₃O₈)(TeO₃)₂ is a wide band-gap semiconductor.     

Effect of nano-filler dispersion on the thermal, mechanical and water sorption properties of green environmental polymer

Partially exfoliated nanocomposite（2） has been synthesized by intercalation of poly（propylene carbonate）（PPC） into commercial clay,Cloisite 20B（PPC/C-20B）.Nanocomposite 2 was characterized phiso-chemically and exhibited high thermal,mechanical and anti-water sorption properties as compared to PPC and intercalated nanocomposite（1） of PPC/C-20B having same amount of clay.TGA results revealed that the thermal decomposition temperature(T_d,50%) of 2 increased significantly,being 40 K and 17 K higher than that of pure PPC and 1,respectively,while DSC measurements indicated that the nano-filler dispersion of 2 increased the glass transition temperature from 21℃to 31℃.Accordingly,2 showed high elastic modulus,hardness and anti-water absorption capacity.These thermal,mechanical and anti-water absorption improvements are of great importance for the application of PPC as packaging and biomaterials.