Rapid synthesis of copper nanoparticles by sodium hypophosphite reduction in ethylene glycol under microwave irradiation

This paper presents a rapid method for preparation of copper metal nanoparticles by reducing CuSO₄·5H₂O with NaH₂PO₂·H₂O in ethylene glycol under microwave irradiation. The influences of the reaction parameters, such as the concentrations of reducing agent and protective polymer time of microwave irradiation, on the size and agglomeration of copper nanoparticles were investigated by X-ray powder diffraction and transmission electron microscope. Well-dispersed copper nanoparticles with diameter of about 10 nm were obtained. The use of microwave irradiation accelerated the reaction rate and benefited the dispersion and the particle size distribution of the nanoparticles.     

Preparation and optical properties of silicate glasses containing Pd nanoparticles

We report the space selective precipitation of Pd nanoparticles in Pd²⁺-doped silicate glass by ultrashort laser pulses irradiation and further annealing. Absorption spectra, transmission electron microscopy, refractive index measurement and Z-scan technique demonstrated that metallic Pd nanoparticles were precipitated in the glass sample after irradiation by an 800-nm femtosecond laser and subsequent annealing at 600 °C. We discuss a refractive index change and nonlinear absorption that combines the precipitation of Pd nanoparticles.     

Growth and optical properties of self-frequency-doubling laser crystal Yb:LuAl3(BO3)4

Single crystal of Yb:LuAl₃(BO₃)₄(Yb:LuAB) was grown by the flux method for the first time. The cell parameters of the grown crystal were estimated by X-ray diffraction analysis. The result indicates the symmetry of trigonal space group R32, with lattice parameters a=b=9.26372 Å, c=7.21405 Å, V=536.14 Å³, and Z=4. The absorption and emission spectra of Yb:LuAB crystal at room temperature has also been studied. The fluorescence lifetime for Yb:LuAB crystal is about 1.48 ms. The heat capacity was measured from 25 to 500 °C. Its second harmonic generation efficiency in LuAl₃(BO₃)₄ crystal is 3–4 times that of KDP crystal. These results show that Yb:LuAB crystal would be a potential self-frequency-doubling laser crystal.     

Synthesis, growth, thermal, optical, dielectric and mechanical properties of semi-organic NLO crystal: Potassium hydrogen malate monohydrate

Potassium hydrogen malate monohydrate (PHMM), a semi-organic nonlinear optical material, has been synthesized and single crystals were grown from aqueous solution. Single crystals of PHMM have been grown by slow evaporation of solvent at room temperature up to dimensions of 22 mm×16 mm×14 mm. Single-crystal X-ray diffraction study on grown crystals shows that they belong to monoclinic system and non-centrosymmetry spacegroup Cc. The structural perfection of the grown crystals has been analyzed by high-resolution X-ray diffraction (HRXRD) rocking curve measurements. Fourier transform infrared (FTIR) spectroscopic study was performed for the identification of different modes of functional groups present in the compound. The UV–Vis transmission spectrum has been recorded in the range 200–1100 nm. The thermal stability of the compound has been determined by TG-DTA curves. The dielectric studies were performed. From the microhardness measurements, Vicker's hardness number (H_v), Stiffness constant (C₁₁), fracture toughness (k_c), Brittle index (B_i) and yield strength (σ_y) have been calculated. The Young's modulus was calculated using the Knoop hardness measurement. The SHG relative efficiency of PHMM crystal was found to be 1.2 times higher than that of KDP.     

Hydrogen bonded nonlinear optical γ-glycine: Crystal growth and characterization

Single crystals of γ-glycine(GG) were grown by solvent evaporation technique from a mixture of aqueous solutions of glycine and ammonium nitrate at ambient temperature. X-ray diffraction, thermogravimetric/differential thermal analysis, Fourier transform infrared spectral techniques were employed to characterize the crystal. The lattice parameters were calculated and they agree well with the reported values. GG exists as dipolar ions in which the carboxyl group is present as a carboxylate ion and the amino group as an ammonium ion. Due to this dipolar nature, glycine has a high decomposition temperature. The UV cutoff of GG is below 300 nm and has a wide transparency window, which is suitable for second harmonic generation of laser in the blue region. Nonlinear optical characteristics of GG were studied using Q switched Nd:YAG laser (). The second harmonic generation conversion efficiency of GG is 1.5 times that of potassium dihydrogen phosphate . The X-ray diffraction and Fourier transform infrared spectral studies show the presence of strong hydrogen bonds which create and stabilize the crystal structure in GG. The main contributions to the nonlinear optical properties in GG results from the presence of the hydrogen bond and from the vibrational part due to very intense infrared bands of the hydrogen bond vibrations. GG is thermally stable up to 441 K.     

Oriented growth of benzophenone crystals from undercooled melts

The tin sulfides compounds SnS and SnS₂ nanoflakes were prepared by the microwave-assisted polyol synthetic method. The as-prepared nanoscale flakes were characterized by X-ray powder diffraction, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy and Raman spectra. The influences of solvents and microwave irradiation on the formation of products have been studied.     

Preparation,crystal structure,spectrographic characterization,thermal and third order nonlinear optical properties of benzyltriethylamine bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickel(III)

The preparation and crystal structure of a novel nonlinear optical organometallic crystal, benzyltriethylamine bis(2-thioxo-1,3-dithiole-4,5-dithiolato)nickel(III) (BTEANDT), are described. The crystal was characterized by elemental analyses, infrared and X-ray powder diffraction spectroscopy, thermal analysis and optical absorption. The third order nonlinear optical properties of crystal were investigated by using the Z-scan technique at 1064 nm with 20 ps. A self-focusing effect and a saturable absorption were observed. The nonlinear refraction coefficient (n₂) and the nonlinear absorption coefficient (β) have been found to be 7.311×10⁻¹⁸ m²/W and −6.064×10⁻¹¹ m/W when the on-axis irradiance at focus (I₀) is 3.025 GW/cm². The relationship between β and I₀ was studied, which has revealed that the former is proportional to the latter. The result has been explained with the theory of absorption cross-section.     

Growth and characterization of the nonlinear optical single crystal: l-lysine acetate

Single crystals of l-lysine acetate, an organic nonlinear optical (NLO) material, were grown by the controlled evaporation of its aqueous solutions. Its solubility in aqueous solution was determined gravimetrically. The grown crystals were characterized by the single-crystal diffraction, X-ray powder diffraction, Fourier transform infrared and Raman spectra. The structure analysis reveals that it belongs to the monoclinic crystallographic system, space group P2₁, with cell parameters: a=5.420(2) Å, b=7.542(4) Å, c=12.653(1) Å, β=91.73(1)°, Z=2 and V=516.8 Å³. Experiments of thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to study its thermal properties. The optical behaviours, including transmission spectrum and second harmonic generation (SHG), were investigated to study its linear and NLO properties.     

Solvothermal synthesis of K2V3O8 nanorods

A solvothermal route has been developed to synthesize K₂V₃O₈ nanorods via the reduction of V₂O₅ using ethanol as the reducing agent as well as the solvent at 200°C. X-ray diffraction and selected area electron diffraction analysis revealed that the as-synthesized products are of tetragonal structure K₂V₃O₈. Transmission electron spectroscopy image showed that the obtained K₂V₃O₈ comprises rod-like nanocrystallites. The formation mechanism of K₂V₃O₈ was studied.     

Synthesis, growth of organic nonlinear optical crystal: Semicarbazone of 2-amino-5-chloro-benzophenone (S2A5CB) and its characterisation

A new organic crystal of semicarbazone of 2–amino–5–chloro–benzophenone has been grown as a single crystal by slow evaporation solution growth technique for the first time in the literature. The grown crystal has been characterised by proton nuclear magnetic resonance spectral analysis and single crystal and powder X-ray diffraction studies. Functional groups of the crystallised molecules were confirmed by FT-IR and FT-Raman analyses. Mechanical strength of the crystals was studied by microhardness test. Optical transparency of the grown crystals has been studied by UV-Visible spectra. The second harmonic generation property of the compound was analysed.     

Microwave-assisted self-assembled ZnS nanoballs

Self-assembled zinc sulfide nanoballs were prepared in saturated aqueous solutions via a microwave-assisted route. Zinc acetate and thioacetamide were selected as zinc source and sulfur source, respectively. Powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectra, Fourier transform infrared and Thermogravimetric analysis were used to characterize the as-prepared products and the optical properties was studied by diffuse reflection spectra and photoluminescence spectra. Zinc sulfate and zinc nitrite can also used to prepare ZnS nanoparticles instead of nanoballs. The mechanism for the assembly of ZnS nanoballs was also discussed.     

Thermal and laser properties of Yb:YAl3(BO3)4 crystal

Large optical-quality Yb:YAl₃(BO₃)₄(Yb:YAB) crystals have been grown by the flux method. The thermal properties of Yb:YAB crystal were measured for the first time. The thermal properties of Yb:YAB crystal with different Yb³⁺ ion concentrations are also reported. The results show that the ytterbium concentration influences the properties of Yb:YAB crystal. The specific heat decreases with the increase of Yb³⁺ ion concentrations in the experiment range. Apparently, the thermal expansion coefficient increases along the c-direction with the increase of Yb³⁺ ion concentrations, while it changes slightly along the a-direction. The output laser in 1120–1140 nm ranges has been demonstrated pumped by InGaAs laser. The slope efficiency is 3.8%. The self-frequency-doubling output power of 1 mW is achieved.     

Synthesis and characterization of a micro scale zinc oxide–PVA composite by ultrasound irradiation and the effect of composite on the crystal growth of zinc oxide

Micro scale zinc oxide-polyvinyl alcohol (ZnO–PVA) composite has been synthesized by ultrasound irradiation. The properties of the as-prepared ZnO–PVA composite material are characterized by X-ray diffraction (XRD), thermo gravimetric analysis (TGA), transmission electron microscopy (TEM), and diffuse reflection spectroscopy (DRS). A band gap of 3.25 eV is estimated from DRS measurements. The controlled crystal growth of zinc oxide has been studied by using the as-prepared micro scale ZnO–PVA composite as seeds for the crystal growth of ZnO.     

Unidirectional growth of l-asparagine monohydrate single crystal: First time observation of NLO nature and other studies of crystalline perfection,optical, mechanical and dielectric properties

L-asparagine monohydrate (LAM), a new amino acid single crystal, was grown by slow evaporation solution technique (SEST) as well as by recently invented Sankaranarayanan–Ramasamy (SR) method in aqueous medium. Using SR method, LAM single crystal of diameter ∼18 mm and length ∼52 mm was grown for the first time. The growth conditions were optimized and the maximum growth rate of 1.0 mm per day was observed for the SR crystal. The crystal structure was confirmed by powder XRD. The crystalline perfection was assessed by high resolution XRD and etching studies and found that the quality of the SR crystal is better than the SEST crystal. The UV–vis–NIR spectroscopic study revealed that the SR crystal has good optical transparency than that of SEST crystal. The relative second harmonic generation efficiency was measured and found to be ∼0.35 times to that of KDP. The laser damage threshold (LDT) was measured and found that the SR crystal has higher LDT value (5.76 GW cm⁻²) than SEST crystal (4.75 GW cm⁻²). The Vickers’s microhardness and dielectric studies were also carried out and discussed.     

Homogeneous SiGe crystals grown by using the traveling liquidus-zone method

It is indispensable to estimate a diffusion coefficient in a solution zone in order to grow a homogeneous crystal by using the traveling liquidus-zone (TLZ) method. To estimate the diffusion coefficient of Ge in the SiGe solution zone, result of a two-dimensional numerical simulation is compared with an experimental result. From the comparison, the diffusion coefficient is estimated to be 9.5×10⁻⁵ cm²/s. By using this coefficient, a sample translation rate for obtaining a homogeneous SiGe crystal is determined. By translating samples with appropriate rates, homogeneous Si_0.5Ge_0.5 crystals are successfully grown. The typical Ge composition is 0.496±0.006 for more than 13 mm long. The experimental result shows the homogeneity of ±1.2% in the mole fraction. This deviation corresponds to the variation of less than ±0.03% in the lattice constant. Since this variation is negligibly small, the homogeneity is excellent. Thus it is found that the TLZ method is the universal growth technique, which is applicable to the crystal growth of not only the III–V compounds but also the IV–IV compounds.     

Synthesis of monodispersed cubic magnetite particles through the addition of small amount of Fe into Fe(OH)2 suspension

Magnetite particles were synthesized through a process including dissolution of Fe(OH)₂ and precipitation of an oxidized phase in aqueous solution. The Fe³⁺ ion was added at the beginning of the synthesis to accelerate the formation of magnetite, control the particle size and improve the monodispersibility. It was found that the addition of Fe³⁺ ion affected the nucleation and the formation of magnetite particles significantly. Magnetite nanoparticles with small particle size and narrow size distribution were obtained. Furthermore, high magnetic properties were obtained in small particle size. The particle size and magnetic properties increased through the increase of Fe²⁺/Fe³⁺ ratio.     

Synthesis,growth and characterization of organic nonlinear optical bis-glycine maleate (BGM) single crystals

A new organic compound of bis-glycine maleate was synthesized in the alkaline medium of 10% ammonium hydroxide solution. The bulk single crystals of Bis-Glycine Maleate (BGM) have been grown by slow cooling method. The grown crystals were characterized by employing single crystal and powder X-ray diffraction, Fourier transform infrared, optical absorption spectral studies and thermo gravimetric analysis. The microhardness studies confirmed that the BGM has a fairly high Vicker’s hardness number value (41 kg mm⁻²) in comparison to other organic NLO crystals. Second harmonic generation efficiency of the crystal measured by Kurtz–Perry powder method using Nd:YAG laser is found to be comparable to that of potassium dihydrogen phosphate (KDP). Frequency dependent dielectric studies were carried out along the major growth axis.     

Synthesis, properties, and applications of magnetic iron oxide nanoparticles

Magnetic nanoparticles exhibit many interesting properties that can be exploited in a variety of applications such as catalysis and in biomedicine. This review discusses the properties, applications, and syntheses of three magnetic iron oxides – hematite, magnetite, and maghemite – and outlines methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles. Some challenges to further development of these materials and methods are also presented.     

Synthesis and optical properties of Ce-doped ZnO hexagonal nanoplatelets

Single crystalline Ce-doped ZnO hexagonal nanoplatelets are successfully synthesized. Zinc acetate, cerium nitrate, potassium hydroxide and poly vinyl alcohol were mixed together and transferred to a 100 mL Teflon-lined stainless steel autoclave kept at 150 °C for 24 h. The obtained precipitant is calcined at 600 °C. The morphology and microstructure were determined by field emission scanning electron microscopy (FE-SEM), X-ray diffraction transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX) and photoluminescence (PL) spectroscopy. The investigation confirmed that the products were of the wurtzite structure of ZnO. The doped hexagonal nanoplatelets have edge length 25 nm and thickness 11 nm. EDX result showed that the amount of Ce in the product is about 15%. Photoluminescence of these doped hexagonal nanoplatelets exhibits a blue shift and weak ultraviolet (UV) emission peak, compared with pure ZnO, which may be induced by Ce-doping. The growth mechanism of the doped hexagonal nanoplatelets was also discussed.