Synthesis and luminescence properties of Eu2+-activated Ca4Mg5(PO4)6 for blue-emitting phosphor

Ca ₄ Mg ₅ (PO ₄ ) ₆ :Eu²⁺^{\boldsymbol{2+}} blue-emitting phosphor was synthesized by the combustion-assisted synthesis method under reductive atmosphere. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectrum. XRD analysis confirmed the formation of Ca ₄ Mg ₅ (PO ₄ ) ₆ pure phase. Photoluminescence results showed that the phosphor can be excited efficiently by UV light range from 230–400 nm, and then exhibited bright blue light with peak wavelength at 431 nm. It is a very promising candidate as a blue-emitting phosphor for potential applications in display devices.     

Structural and electrical properties of Ta<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript>O<Subscript><Emphasis Type="Bold">5</Emphasis></Subscript> thin films prepared by photo-induced CVD

Tantalum oxide (Ta ₂ O ₅ ) films and Al/Ta ₂ O ₅ /Si MOS capacitors were prepared at various powers by ultraviolet photo-inducing hot filament chemical vapour deposition (HFCVD). Effects of ultraviolet light powers on the structure and electrical properties of Ta ₂ O ₅ thin films were studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). The dielectric constant, leakage current density and breakdown electric field of the samples were studied by the capacitance–voltage (C–V) and current–voltage (I–V) measurements of the Al/Ta ₂ O ₅ /Si MOS capacitors. Results show that the Ta ₂ O ₅ thin films grown without inducement of UV light belong to amorphous phase, whereas the samples grown with inducement of UV-light belong to δ-Ta ₂ O ₅ phase. The dielectric constant and leakage current density of the Ta ₂ O ₅ thin films increase with increasing powers of the UV- lamps. Effects of UV- lamp powers on the structural and electrical properties were discussed.     

Piezomodulation of excitonic reflectance spectra in CuCl

We have investigated the piezoreflectance spectra of the 1s Z₃ and Z₁₂ excitons in single crystals of copper chloride CuCl at 95 K with linearly polarized light. The spectra were studied for the applied low pressure p (p lower than 1 MPa) directed along the [001], [111] and [110] axis with the wave vector k of the incident light parallel to the [110] direction. A strong piezo-optical response is observed for the Z₃ exciton to regard to the one observed for Z₁₂. From the stress-induced shifts and splitting of the excitonic levels, we have been able to deduce the shear excitonic deformation potentials: b = (–0.18 ± 0.02) eV and d = (0.30 ± 0.03) eV.     

Optically Active Absorptive Fabry-Pérot Etalon

Abstract

The influence of absorption on the intensities of reflected light from a Fabry-Pérot etalon (Bi₁₂GeO₂₀ plate) for incident E_p light is investigated. It is shown that the absorption reduces the effect of optical activity. The mathematical modelling shows a drastic change in the interferograms when absorption is taken into account.     

Light Scattering Study of Aqueous Poly(Vinyl)pyrrolidone–Fullerene C70 Solutions

Abstract

It was shown by static and dynamic light scattering that poly(vinyl)pyrrolidone (PVP) molecules form large intermolecular complexes (clusters) with C₇₀ in aqueous solutions. The molecular weights and dimensions of PVP–C₇₀ clusters increase both with the increase of fullerene content and the molecular weight of the matrix PVP. However, two different diffusion coefficients were detected by dynamic light scattering. The slow mode was explained as diffusion of large PVP–C₇₀ clusters. The fast mode represents free PVP molecules in solution. Dimensions of clusters revealed in aqueous PVP–C₇₀ solutions are less than that for PVP–C₆₀ by factor of 2.5–3.     

Raman Spectra of Chlorinated C60 and C70 Fullerenes

Abstract

Raman spectra of chlorinated C₆₀ and C₇₀ fullerenes prepared by photochlorination have been reported and discussed. The Raman lines suggest structural analogies with already fully characterized brominated fullerenes. Intense laser light irradiation cause a decomposition of fullerene chloro-derivatives leading to the formation of C₆₀ polymer.     

Visible light responsive Bi2S3-graphene/TiO2 nanocomposites: one pot-hydrothermal synthesize and improved photocatalytic properties

Abstract

Herein, we obtained chemically bonded Bi₂S₃-Graphene/TiO₂ composites using a facile one pot-hydrothermal method. During the hydrothermal reaction, both of the reduction of graphene oxide to graphene and loading of Bi₂S₃ and TiO₂ particles on graphene nanosheet were achieved. The resulting composites are characterized by X-Ray diffraction (XRD), Raman spectroscopy and Transmission Electron Microscopy (TEM). The optical properties are studied using UV–visible diffuse reflectance spectroscopy (DRS), which confirms that the spectral responses of the composite catalysts are extended to the visible light region. The dramatically enhanced activity of Bi₂S₃-Graphene/TiO₂ composite photocatalysts can be attributed to great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties, simultaneously. This work may provide new insights into the design of novel composite photocatalysts system with efficient visible light activity.     

Normal form for Mueller Matrices in Polarization Optics

Abstract

The normal (canonical) form for Mueller matrices in polarization optics is derived: it is shown that a non-singular real 4 × 4 matrix M qualifies to be the bona fide Mueller matrix of some physical system if and only if it has the canonical form M = L′ ΛL, where L and L′ are elements of the proper orthochronous Lorentz group L ^↑ ₊, and where Λ = diag (λ₀, λ₁, λ₂, λ₃) with λ₀ ≥ ¦λ_j¦ > 0. It is further shown that λ₁ and λ₂ can be taken to be positive so that the signature of λ₃ is the same as that of det M. Several experimentally measured Mueller matrices are analysed in the light of the normal form. The case of singular Mueller matrices is briefly discussed as a limiting case.     

On the Action of γ Radiation on Solid C60 and C70 Fullerenes: A Comparison with Graphite Irradiation

Abstract

C₆₀ and C₇₀ fullerene have been treated in sealed flasks under Ar with γ radiation using radiation dosages ranging from 10 to 1000 kGy. The treated samples studied by electronic and FT-IR spectroscopy have not shown any evidence about fullerenes decomposition or radiopolymerization. However, through Raman spectroscopy it was possible to observe that γ radiation induces C₆₀ dimerization and trimerization. It has additionally been discovered that γ-treated C₆₀ (oligomerized) can be easily photopolymerized in the solid state by post-irradiation with laser light at 514 nm while this phenomenon has not been observed by using laser light at 782 nm and considerably higher laser power. Previously to this study, C₆₀ photopolymerization was known to occur only by using ultraviolet light.

For comparison also graphite was irradiated with 1000 kGy of γ radiation. Irradiated graphite shows considerably changes in its Raman spectrum, showing the formation of glassy carbon domains, perhaps carbon onions. The l_d bandshift to 1310 cm^?1 could be interpreted in terms of formation of hexagonal diamond.     

New intelligent multifunctional SiO2/VO2 composite films with enhanced infrared light regulation performance,solar modulation capability,and superhydrophobicity

Abstract

Highly transparent, energy-saving, and superhydrophobic nanostructured SiO₂/VO₂ composite films have been fabricated using a sol–gel method. These composite films are composed of an underlying infrared (IR)-regulating VO₂ layer and a top protective layer that consists of SiO₂ nanoparticles. Experimental results showed that the composite structure could enhance the IR light regulation performance, solar modulation capability, and hydrophobicity of the pristine VO₂ layer. The transmittance of the composite films in visible region (T_lum) was higher than 60%, which was sufficient to meet the requirements of glass lighting. Compared with pristine VO₂ films and tungsten-doped VO₂ film, the near IR control capability of the composite films was enhanced by 13.9% and 22.1%, respectively, whereas their solar modulation capability was enhanced by 10.9% and 22.9%, respectively. The water contact angles of the SiO₂/VO₂ composite films were over 150°, indicating superhydrophobicity. The transparent superhydrophobic surface exhibited a high stability toward illumination as all the films retained their initial superhydrophobicity even after exposure to 365 nm light with an intensity of 160 mW^.cm^?2 for 10 h. In addition, the films possessed anti-oxidation and anti-acid properties. These characteristics are highly advantageous for intelligent windows or solar cell applications, given that they can provide surfaces with anti-fogging, rainproofing, and self-cleaning effects. Our technique offers a simple and low-cost solution to the development of stable and visible light transparent superhydrophobic surfaces for industrial applications.     

Photo-Induced Cytotoxicity of Water-Soluble Fullerene

Abstract

The reaction of C₆₀ with poly(ethylene glycol) having a terminal primary amino group or a mixture of ethylene diamine and poly(ethylene glycol) having terminal carboxyl groups resulted in formation of water-soluble C₆₀ conjugates. These conjugates showed strong cytotoxicity to L929 cells upon visible light irradiation as a result of superoxide production.     

Synthesis,Spectral Investigations,and Thermal Stability of [60]Fullerene Complexes with TMTSF: 2(C60) · 2(TMTSF) · (C6H6), C60 · TMTSF · 2(CS2), and 2(C60) · 2(TMTSF) · (C6H5Cl)

Abstract

Molecular complexes of [60]fullerene with tetramethyltetraselenafulvalene (TMTSF): C₆₀ · (TMTSF) · 2(CS₂) (1), 2(C₆₀) · (2(TMTSF) · (C₆H₆) (2), and 2(C₆₀) · (2(TMTSF) · (C₆H₅Cl) (3) have been synthesized and their thermal stability and IR spectra vs. light polarization and temperature have been performed.     

[60]Fullerene as a Novel Photoinduced Antibiotic

Abstract

The antibacterial activity of [60]fullerene (C₆₀), dissolved with poly(vinylpyrrolidone) K30 (PVP), was studied. Under photo‐irradiation, C₆₀/PVP aqueous solutions showed antibacterial activity, whereas PVP solution alone or fullerene solutions in the absence of light showed no activity. These results reveal that C₆₀ is a potentially good device as a photoinduced antibacterial agent.     

Second Harmonic Generation in Optical Fibres: Multiphoton Absorption and Translation-inversion Symmetry

Abstract

Multiphoton absorption provides a route to x ₍₂₎ grating formation in optical fibres. It explains the efficacy of ‘seeding’ the fibre with green light to induce fibre second harmonic generation. The process depends on absorption sites with spatially inverted configurations having different multiphoton absorption rates.     

Visible Light Irradiation of [60]Fullerene Causes Killing and Initiation of Transformation in Balb/3T3 Cells

Abstract

Cell transformation in vitro is a model of carcinogenesis in vivo. Two-stage transformation assay increases the sensitivity of cells to chemicals and permits detection of carcinogens acting as initiating agents. [60]Fullerene (C₆₀) was cytotoxic in BALB/3T3 cells when it was irradiated by visible light, but not without light irradiation. Under conditions when C₆₀ was cytotoxic, it acted as an initiating agent for cell transformation, but it did not act as a complete transforming agent. the initiating activity of visible-light-irradiated C₆₀ was statistically significant in a modified two-stage transformation assay including a procedure for replating cells treated by C₆₀ and light, but it was equivocal in the standard two-stage transformation assay.     

Photoinduced superhydrophilicity of TiO2 thin film with hierarchical Cu doping

Abstract

Hydrophilic Cu–TiO₂ thin films with a gradient in the Cu concentration were prepared on glass by layer-by-layer dip-coating from TiO₂ precursors. The effects of the Cu doping on the structure and properties of TiO₂ self-cleaning thin films are discussed. The Cu gradient markedly affects the hydrophilicity of the films, with the water contact angle significantly reduced compared with those of the pure or uniformly doped TiO₂ thin films. This enhanced hydrophilicity is explained by the more efficient absorption of the solar light and by the reduced recombination of photoexcited electrons and holes in the TiO₂ films containing a gradient of Cu dopants.     

Computation of X-ray powder diffractograms of cement components and its application to phase analysis and hydration performance of OPC cement

The importance of computed X-ray diffraction patterns of various polymorphs of alite (M₃, T₁, R{\bf \emph{M}_{3}, \emph{T}_{1}, \emph{R}}), belite (b\boldsymbol{\beta}, g\boldsymbol{\gamma}), aluminate (cubic, orthorhombic), aluminoferrite, gypsum and hemihydrate in the quantitative phase analysis of cement and its early stage hydration performance is highlighted in this work with three OPC samples. The analysis shows that the predominant silicate phases present in all the samples are M₃{\bf \emph{M}_{3}}-alite phase and b\boldsymbol{\beta}-belite phase, respectively. Both cubic and orthorhombic phases of C ₃ A, brownmillerite, gypsum and hemihydrates are present at different levels. Quantitative phase analysis of cement by Rietveld refinement method provides more accurate and comprehensive data of the phase composition compared to Bogue method. The comparative hydration performance of these samples was studied with w/c{\bf \emph{w/c}} ratio, 0·5 and the results are interpreted in the light of difference in phase compositions viz. b\boldsymbol{\beta}-C ₂ S/C ₃ S ratio, fraction of finer cement particles present in the samples and theoretical modeling of C ₃ S hydration.     

Effect of Film Thickness and Interface Roughness Correlation on the Light Scattering from Amorphous and from Columnar Structured Optical Films

Abstract

The dependence of total integrated light scattering on film thickness is investigated for evaporated PbF₂-films and magnetron sputtered Nb₂O₅-films. The experimental results are discussed on the basis of theoretical model assumptions, relating the scattering behaviour to interface roughness cross-correlation effects as well as to the evolution of film morphology with increasing film thickness. Electron microscopy examinations serve to make evident the different film structures responsible for the specific scattering properties observed.     

Investigation on photogenerated radicals of some carboxylates in solution and in aqueous dispersions of AgBr

Abstract

The photogenerated free radicals from formate, oxalate and acetate in aqueous solutions without and with dispered AgBr grains under illuminations of 355 nm laser light, natural light and monochromatic red, green or blue light were detected by electron spin resonance with spin-trap DMPO. The results showed that: (a) ·CO₂^? radicals were produced in the formate solution by all of these illuminations; (b) the signals of ·CO₂^? radicals were greatly intensified when an AgBr dispersion was present in the formate solution; (c) the signals of ·CO₂^? radicals in the oxalate solution were also detected and intensified when an AgBr dispersion was present, but only after illumination by the 355 nm laser; (d) ·CH₃ radicals, instead of ·CO₂^?, were weakly detected in the acetate solution, but only in the presence of AgBr under illumination by the 355 nm laser. The photochemical behaviour of these carboxylates, particularly formate and oxalate, perhaps implies their capability for trapping photogenerated holes and their potential for acting as a hole converter to an effective electron carrier.     

A Photovoltaic C60-Si Heterojunction

Abstract

A heterojunction was prepared by depositing a thin film of C₆₀ on a p-Si substrate. Photovoltaic properties were observed using a UV-filtered solar simulator and natural sun light. Surface Photovoltage Spectroscopy was employed to distinguish between the nature of photoconversion in the C₆₀ and Si layers.