Preparation and refractive index characterization of chalcogenide glasses with gradient refractive index

Infrared gradient refractive index (GRIN) lenses have great application value and potential in multispectral imaging systems. This study reports various chalcogenide axial GRIN glasses prepared using the hot-pressing diffusion method. It is worth noting that the S4–S60 GRIN sample has a difference in refractive index (RI) Δn of greater than 0.3 and a diffusion depth of about 5 mm, which is the deepest diffusion depth reported in chalcogenide glass to date. In addition, the linear portion in the profile of the GRIN sample has a RI difference of 0.15 and a thickness of 1.2 mm. The effects of the temperature, concentration difference, and diffusion time on the sample diffusion process are discussed. The dispersion properties of the GRIN samples were further calculated, providing a new option for correcting chromatic aberrations in optical systems. In addition, a method for the indirect nondestructive characterization of sample RI using the Raman intensity ratio is proposed, and the reliability of the method is verified by practical experiments, which is convenient for the subsequent measurement of the GRIN profile.     

Influence of molybdenum oxide on structural,optical and physical properties of oxychloride glasses for nonlinear optical devices

The unconventional Heavy Metal Oxide Glasses (HMOG) are characterized by a low phonon energy, large infrared range transmission, high refractive index and nonlinear optical properties. Ternary glasses have been synthesized and studied in the Sb₂O₃– MoO₃-ZnCl₂ system. Further, the glass formation compositional limits are reported and some glass samples with the formula: (90-x)Sb₂O₃ -xMoO₃–10 ZnCl₂ (10 ≤ x ≤ 50, mole%) were elaborated. Thermal properties have been measured and indicating that the glass transition temperature decreases with increasing proportions of molybdenum oxide. The evolution of density, microhardness and elastic modulus has been studied as functions of parameter x and Raman spectra measurements have been shown the partial conversion of MoO₆ octahedral units into MoO₄ tetrahedral.     

Preparation and elastic moduli of germanate glass containing lead and bismuth

This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO₂)₆₀–(PbO)_40−x–(½Bi₂O₃)_x where x = 0 to 40 mol%. Their densities with respect of Bi₂O₃ concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B₂O₃)₂₀–(PbO)_80−x–(Bi₂O₃)_x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi₂O₃ content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi₂O₃ but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi₂O₃ concentration.     

Crystallization,spectroscopic and dielectric properties of CuO-added magnesium aluminosilicate-based glasses

In this work, CuO-doped MgO-Al₂O₃-SiO₂ based glasses have been synthesized successfully through conventional melt quenching method, and the effect of CuO content on the structure and properties of the glasses was investigated. The results revealed that CuO could act as a glass modifier to depolymerize the silicate network and its effect was superior to that of MgO. In addition, the main crystalline phase was α-cordierite (Mg₂Al₄Si₅O₁₈), indicating that copper ions did not participate in the formation of the crystalline phase, and still existed in the interstitial position. The characteristic absorption band around 750 nm owing to the ²B_1g→²B_2g transition of Cu²⁺ ions appeared on the optical transmittance spectra, which confirmed the existence of Cu²⁺ ions in the tetragonally distorted octahedral sites. The luminescence center was caused by Cu⁺ ions, and the luminescence lifetime decreased with the addition of CuO. The dielectric constant and dielectric loss increased with the increase of CuO content, indicating an increase in the insulation performance. Finally, the obtained chromaticity coordinate parameters indicate that the prepared CuO-doped magnesium aluminosilicate-based glasses can be applied in optical and electrical fields.     

Effect of cobalt-60 γ radiation on the physical and chemical properties of poly(ethylene terephthalate) polymer

The structural, optical, and morphological properties of Co⁶⁰ γ irradiation on poly(ethylene terephthalate) polymer samples were studied with X-ray diffraction (XRD), ultraviolet–visible spectroscopy, scanning electron microscopy (SEM), and Raman spectroscopy. The diffraction pattern of virgin sample showed that the polymer was semicrystalline in nature. However, because of irradiation, the crystallinity decreased up to a dose level of 110 kGy and increased up to 300 kGy. The crystallite size, strain, and dislocation were calculated from the XRD data, and the crystallite size decreased from 291.07 to 346.90 Å. The absorption edge shifted from 315 to 330 nm, and the band gap of the samples decreased from 3.79 to 3.66 eV. The SEM micrographs showed radial bulging along with inhomogeneous liner exfoliation, and also, a rocky shape pattern with different sizes was observed. A significant change was found in the Raman spectra of the γ-irradiated polymer at the highest dose. The results of the structural, optical, and morphological studies show recovery characteristics at the highest dose level of 300 kGy. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structural and photoluminescence properties of Dy-doped nanocrystalline ZrO2 for optoelectronics application

Nanocrystalline Dy³⁺ doped ZrO₂ sample has been synthesized using sol-gel wet chemical method. The sample has been investigated for structural, thermal, and photoluminescence properties employing X-ray Diffraction, Fourier Transform Infrared spectroscopy, Thermogravimetric analysis, Transmission Electron Microscopy, UV–visible spectroscopy, and Photo-Luminescence characterization techniques, respectively. The Rietveld refinement of XRD data reveals cubic phase (lattice constant = 5.138 Å) of doped-ZrO₂ nano-crystals with space group Fm-3m. The average crystallite size and micro-strain are estimated as 46.21 nm and 0.0047, respectively, from Williamson-hall (W–H) plot analysis. FT-IR spectroscopy confirms the existence of Zr–O vibration modes of ZrO₂ phase. The optical band gap of Dy-doped ZrO₂ sample is found as 5.3 eV which is analogous to other reports. Photo-Luminescence result shows that the Dy doped-zirconia contains three significant characteristic peaks at 484, 583 and 678 nm under the excitation of a wavelength of 350 nm. Those peaks attribute to the electronic transition of Dy ions. The obtained CIE chromaticity coordinate of doped ZrO₂ is (0.337, 0.335) representing neutral white light. The findings of this work implies application of doped zirconia in the area of optoelectronic devices.     

Enhancement of luminescence properties and the role of ZnO in Tb3+ ions doped zinc aluminum phosphate glasses

Terbium ion doped zinc aluminum phosphate (ZAP) glasses with composition (90−x)((90−y)P₂O₅–10Al₂O₃–yZnO)–xTb₂O₃ (x=0.5–9 in mol% and y=30, 35, 40 in mol%) have been prepared by melt quenching method, and the effects of the Tb₂O₃ and ZnO content on the luminescence properties have been studied by photoluminescence spectroscopies. It was found that the green emission peaked at 544 nm is significantly enhanced under higher Tb₂O₃ content, meanwhile the sensitization effect of ZnO content is confirmed from the enhanced main emission. The quenching effect attributed to the resonant energy transfer through the cross-relaxation mechanism is observed when Tb₂O₃ concentration is beyond 2.5 mol% due to the fact that more Tb³⁺ ions enhance the 4f→5d and 4f→4f electronic transitions through the dipole–dipole (d–d) interaction. Also, ZnO plays a role of the disperser to prevent non-radiative de-excitation process. A characteristic luminescence image of the (100−x)(60P₂O₅–10Al₂O₃–30ZnO)·xTb₂O₃ series glasses under UV excitation at 366 nm is presented for the first time, and the transition of luminescence suggests that the Tb³⁺-doped ZAP glasses are suitable for green and dual-color blue/green LED applications by modulation of Tb and ZnO composition.     

Effect of Sn doping on the structural,optical, electrical and anticancer properties of WO3 nanoplates

This report is on the synthesis of Sn doped WO₃ nanoplates by a facile co-precipitation method. Various characterization tools have been employed to study the effect of Sn doping on the structural, optical and dielectric properties of WO₃ nanoplates. The successful incorporation of dopant ions in the monoclinic structure of WO₃ has been verified by XRD, EDX, FTIR and Raman spectroscopy. It has been observed that there is a broadening in optical band gap for doped samples due to the band filling effects caused by the crystal defects. Furthermore, the frequency dependent electrical properties of WO₃ nanoplates are found to be significantly tuned by Sn doping. Most importantly, this is one of the initial reports that Sn doped WO₃ nanoplates are an excellent candidate for anticancer applications. The anticancer activity of WO₃ nanoplates against MCF-7 cancer cells is increased with Sn doping which is attributed to several factors such as particle size, defects density and reactive oxygen species (ROS) production.     

Synthesis and properties of tellurite based glasses containing Na2O,BaO, and TiO2: Raman,UV and neutron/charged particle shielding assessments

In this paper, 75TeO₂–5Na₂O–20BaO?xTiO₂ (TNB-Tix with x = 0, 05, 10, and 15) glasses were synthesized by the conventional melt-quench technique using analytic grade tellurium oxide (TeO₂), barium carbonate (BaCO₃), sodium carbonate (Na₂CO₃) and titanium oxide (TiO₂) as starting chemicals. The prepared glasses were studied for their physical features, Raman and UV spectra, and shielding performance against neutrons and charged particles. The optical property was investigated by UV–Vis spectrometry while the structural evolution of the glasses was studied through the Rahman spectra. Charged particles, slow and fast neutrons interaction parameters of the glasses were calculated theoretically and analyzed as well. The prepared glasses were yellowish without any flaws. The mass density of the glasses increased from 5.1 to 5.4 g/cm³ as TiO₂ content declined from 15 to 0 mol%. Also, an improvement in the optical bandgap from 2.89 to 3.2 eV was recorded as BaO content increased concerning TiO₂ while the refractive index declined from 2.43 to 2.35. Generally, the improvement in the TiO₂ content of the glasses produced a rise in the total and scattering cross section of thermal and slow neutrons respectively. In addition, the fast neutron cross section was enhanced from 0.1005 to 0.1015 cm^?1 for TNB-Ti00 – TNB-Ti15 glasses. The charged particle shielding parameters showed a strong dependence on the chemical structure of the glass system. The present glass system displayed good properties that could make them useful in optical and shielding applications.     

Preparation,characterization and photoluminescence properties of SiO2 and SiO2:Eu3+ submicron rods

SiO₂ and Eu³⁺-doped SiO₂ submicron rods were conveniently fabricated via a sol–gel process at room temperature. In this process, citric acid served as a unique structural modifier through hydrolysis of TEOS at alkaline condition to obtain the silica submicron rods. The morphology of the products was sensitive to the conditions, such as stirring, gelation time and the dropping speed of NH₄OH. By sampling the products at different reaction times, we discussed the formation and growing mechanism of SiO₂:Eu³⁺ submicron rods in detail. The weak interactions between ammonium citrate crystals and silica species may be the reasons of the rods formation. The obtained silica submicron rods were 5–6 μm in length and 650–750 nm in width and there was no obvious change after doping. Under UV light excitation, the undoped silica submicron rods exhibited blue emission, which may be associated with defect centers in the structures of the products. The Eu³⁺-doped silica submicron rods exhibited red emission, which was due to the 4f→4f transition of Eu³⁺. The effect of different doping concentrations of Eu³⁺ ions on the luminescence was investigated. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), Thermo-gravimetry Analysis (TGA), Scanning electron microscope (SEM), Transmission electron microscope (TEM), Energy-dispersive spectroscopy (EDS) and Photoluminescence spectrum.     

Luminescence properties of Sm3+ ions doped heavy metal oxide tellurite-tungstate-antimonate glasses

The trivalent Sm³⁺ ion doped tellurium-antimony-tungsten oxides based glasses were prepared by conventional melt quenching and pressing method. Spectroscopic characterizations such as optical absorption, photoluminescence and decay profile measurements were performed on the glasses. Judd-Ofelt theory is used to evaluate the oscillator strengths and the three phenomenological intensity parameters (Ω_λ, λ = 2, 4, 6) of the glasses. The photoluminescence spectra recorded under 479 nm excitation exhibited the emission bands at 562, 598, 645 and 708 nm corresponding to the transitions ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2, 11/2) respectively. Using J-O parameters (Ω_λ) various important radiative parameters viz., transition probabilities, emission cross-sections, branching ratios of various emission bands were evaluated. Decay profiles were recorded to find the lifetime of the ⁴G_5/2 excited level and the obtained life time values are observed to decrease with an increase of Sm³⁺ ion concentration; such decrease is attributed due to clustering of Sm³⁺ ions which may cause luminescence quenching.     

Terbium-doped ZnS quantum dots: Structural,morphological, optical,photoluminescence, and photocatalytic properties

Terbium (0, 2, and 4?at%)-doped ZnS quantum dots (QDs) were synthesized via a solvothermal method. The crystal structures of the synthesized QDs were determined to be zinc blend by X-ray powder diffraction (XRD) and Raman analyses. Transmission electron microscopy (TEM) studies revealed that particles with a mean size of 2–4?nm were formed. An X-ray photo electron spectroscopy (XPS) examination disclosed the existence of terbium with a trivalent state in the ZnS host lattice. The absorption bands of all QDs were located around 325?nm (3.81?eV) and were higher than that of the bulk ZnS band gap (3.67?eV), consistent with the quantum confinement effect. The photoluminescence spectra of the terbium-doped samples displayed five emission peaks at 467?nm (⁵D₄→⁷F₃), 491?nm (⁵D₄ → ⁷F₆), 460?nm (⁵D₄ – ⁷F₅), 484?nm (⁵D₄ – ⁷F₄), and 530?nm (⁵D₄ – ⁷F₃), respectively. The terbium-doped QDs exhibited a higher photocatalytic activity during the degradation of crystal violet dye under UV-light illumination compared to the undoped ZnS QDs. These interesting properties of terbium-doped ZnS QDs are potentially useful for both luminescent and photocatalysis applications.     

Structure and properties of cerium phosphate and silicophosphate glasses

We report on the fabrication, properties, and structure of cerium pyrophosphate glasses and partially substituted cerium silicophosphates. In those glasses, cerium occurs predominantly as Ce(III). A combination of dynamic nuclear magnetic resonance and electrical impedance spectroscopy is used to overcome the problem of assessing cerium speciation. While optical spectroscopy is unable to quantify the ratio of Ce(III)/Ce(IV) due to spectral overlap, proxy observations of the effect of silica-for-cerium substitution on optical extinction and the shape and width of the UV band gap corroborate vibrational spectroscopic data of the structural roles of cerium and silica. While silica bonding to phosphate units appears to stabilize Ce(IV), it also impedes the polaron transport, leading to higher polaron activation energy and lower electronic conductivity. On the other hand, Ce(III) is stabilized by coordinating to P = O.     

Homoepitaxial CVD diamond: Raman and time-resolved PL characterization

In this work, we report on the structural characterization of homoepitaxial Microwave Plasma Enhanced CVD diamond grown onto Ib diamond substrates by varying systematically the methane to hydrogen ratio in the gas mixture (1–7% CH₄). X-ray diffraction, Raman spectroscopy and photoluminescence (PL) have been used to characterize the diamond samples. Raman measurements pointed out the excellent crystalline quality and phase purity of the specimens. PL measurements in the 1.7–2.7 eV energy range have shown completely flat spectra, excluding the presence of nitrogen-related optical centers. Such results show that the homoepitaxial CVD diamond can be grown, at moderate microwave power (720 W), and at growth rates not too low ( 1 μm/h) preserving a good quality. Moreover, the homoepitaxial crystals exhibited a strong free-exciton recombination radiation at room temperature even at the highest methane concentration used (7%). Preliminary measurements of the lifetime of the free exciton at room temperature have been also performed. The excitation was produced by a 5 ns pulsed laser irradiation at energies above the diamond band gap. The results have been compared with the structural properties of the samples and correlated with the growth conditions.     

Synthesis,characterization, and redox and electrochromic behaviors of poly(3-n-octyloxythiophene)

Poly(3-n-octyloxythiophene), a conjugated polymer, which possessed solubility in common organic solvents, was synthesized by electrochemical polymerization in the presence of lithium perchlorate as the supporting electrolyte and sodium dodecyl sulfate as the surfactant in an aqueous medium. Characterizations of the intermediate, monomer, and polymer were performed by NMR spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, and gel permeation chromatography. The process of electrochemical polymerization and the electrochemical redox behaviors were investigated by cyclic voltammetry and the potentiostatic method. A poly(3-n-octyloxythiophene) film that was deposited on a platinum electrode was found to exhibit electrochromic behaviors, and it switched electrochemically between blue–green oxidized and dark red reduced states. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of soluble polyaniline

Polyaniline, which is soluble in common organic solvents, has been synthesized through the oxidative chemical polymerization of aniline in the presence of benzene diazonium chloride salt in an aqueous HCl acid medium. The blue‐black polyaniline thus prepared exists in a lower oxidation state than emeraldine. An X‐ray photoelectron spectroscopy study has shown that the intrinsic oxidation state of the polymer is 0.38. An elemental analysis has shown that the fractional doping level or degree of oxidation of the blue‐black polyaniline is 0.26. The product is believed to consist of a lower number of imine nitrogens in comparison with the polyemeraldine base. This fact is also corroborated by the lower electrical conductivity of the polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization studies of NiO nanorods for enhancing solar cell efficiency using photon upconversion materials

We report the effect of calcination on the structural and optical properties of nanocrystalline NiO nanoparticles were successfully synthesized by virtue of a single source precursor method at mild reaction conditions between nickel nitrate and sodium hydroxide. Composition, structure and morphology of the products were analyzed and characterized by X-ray powder diffraction (XRD). The ultra-violet visible (UV–vis) absorption peaks of NiO exhibited a large blue shift and the luminescent spectra had a strong and broad emission band centered at 328 nm. The intense band gap was also observed, with some spectral tuning, to give a range of absorption energies from 2.60 to 3.41 eV. The various functional groups present in the NiO nanorods were identified by FTIR analysis. High resolution transmission electron microscopy (HRTEM) and the chemical composition of the samples the valence states of elements were determined by X-ray photoelectron spectroscopy (XPS) in detail. The electrochemical response of NiO proved that the nano-nickel has a high level of functionality due to its small size and higher electrochemical activity without any modifications. The above studies demonstrate the potential for the utilization of NiO nanoparticles as a promising material for opto-electronics applications.     

Preparation,characterization and antibacterial properties of cobalt doped titania nanomaterials

Cobalt-doped titania(Co-TiO_2) nanomaterials were synthesized by the sol–gel method at different calcination temperatures. Using Escherichia coli(a), Staphylococcus aureus(b) and Candida albicans(c) as target strains,the antibacterial activity in visible light of the nanomaterials were studied. Co-TiO_2 nanomaterials were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), UV–Vis diffuse reflectance spectroscopy(DRS), Fourier transform infrared spectrum(FT-IR) and X-ray photoelectron spectroscopy(XPS). The Co ions in the Co-TiO_2 nanomaterial exist in the form of CoTiO_3 phase.The antibacterial properties of Co-TiO_2 nanomaterials on E. coli(a), S. aureus(b) and C. albicans(c) were investigated with the oscillating flask method and the inhibition zone method. The nanomaterials calcined at 600 °C exhibit excellent antibacterial activity. The bacteriostatic rates for E. coli, S. aureus and C. albicans reached 99.5%,91.3% and 93.4% respectively. The diameters of the antibacterial rings were up to 36 mm, 37 mm, 30 mm respectively, and the clarity of the ring was clear. The antibacterial properties of Co-TiO_2 nanomaterials were compared with those of traditional silver sol, zinc oxide sol and Zn-doped TiO_2 nanomaterials The mechanism of the influences of Co ions doping on the antibacterial activity of TiO_2 nanomaterials was also discussed. The doping of Co ions inhibits the particle size of the antibacterial agent and extends the photocatalytic response range, thereby improving the photocatalytic performance of the antibacterial agent.     

Effects of In2O3 nanoparticles doping on the photoluminescent properties of Eu2+/Eu3+ ions in silica glasses

Eu²⁺/Eu³⁺ ions doped silica glasses contained In₂O₃ nanoparticles (NPs) have been fabricated by using nanoporous silica glasses. Interestingly, efficient energy transfer from In₂O₃ NPs to Eu²⁺/Eu³⁺ ions enhanced the photoluminescence (PL) emission of Eu²⁺/Eu³⁺ ions, which derives from lattice defects in In₂O₃ NPs. Our work has not only demonstrated a facile way to fabricate NPs and rare earth ions co-doped silica glasses, but also extended the applications of semiconductor oxide NPs such as In₂O₃ NPs.