Ag3PO4/rectorite nanocomposites: Ultrasound-assisted preparation,characterization and enhancement of stability and visible-light photocatalytic activity

To overcome the drawback of low stable brought by the transformation of Ag⁺ into Ag, a highly efficient and stable photocatalyst Ag₃PO₄/rectorite composite was successfully synthesized by ultrasound-assisted precipitation method. The as-prepared samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, N₂ adsorption-desorption, room-temperature photoluminescence spectra, Fourier transform infrared spectrum measurements and UV–vis diffuse reflectance spectra. The absorption edges of the Ag₃PO₄/rectorite display a noticeable shift to the visible light region as compared to that of the Ag₃PO₄. Compared with bare Ag₃PO₄, the Ag₃PO₄/rectorite composite by ultrasound-assisted precipitation process exhibits significantly enhanced photocatalytic activity and stable for methyl orange (MO) degradation under visible light irradiation. The improved activity of the Ag₃PO₄/rectorite photocatalyst could be attributed to the expanded visible light absorption, the enhanced interfacial charge transfer and the inhibited recombination of electron-hole pairs. Therefore, the facile ultrasound-assisted preparation process provides some insight into the application of Ag₃PO₄/rectorite nanocomposites in photocatalytic degradation of organic pollutants.     

19F NMR and Structure of Pt (IV) Hexafluorocomplexes

The present work cites the investigation results of ¹⁹F NMR spectra in polyerystalline compounds of the Me _n[PtF₆]_m type, where Me - Li⁺, Na⁺, K⁺, Ca²⁺, Sr²⁺, Ba²⁺, La³⁺ and Ag⁺. The use of a NMR spectrometer with high field stress (～24 kOe) made possible the observation of different chemical shifts in solids of NMR signals from two nonequivalent fluorine types in octahedric complexes of [PtF₆]^2-.¹⁹ NMR and Structure of Pt (IV) Hexafluorocomplexes     

Vibrational study of H3OUO2PO4 · 3 H2O (HUP) and related compounds. phase transitions and conductivity mechanisms: part I,KUO2PO4 · 3 H2O (KUP)

Infrared and Raman spectra of polycrystalline KUO₂PO₄ · 3 H₂O (KUP) and its isotopic derivatives KUO₂P¹⁸O₄ · 3 H₂O and KUO₂PO₄ · 3 D₂O have been investigated in the 4000-10-cm^?1 range at different temperatures. An assignment of the bands in terms of UO₂, PO₄ and H₂O vibrations has been proposed. Combined differential scanning calorimetry and spectroscopic data show two diffuse phase transitions near 130 and 230 K. Comparison of the vibrational spectra of phase I at 300 K and phase IV at 100 K indicates that ordering of the water molecules with subsequent ordering of PO₄ tetrahedra on a site with lower symmetry appears to be the main mechanism responsible for the phase transformation. All the six O-H distances of water molecules in phase IV are found to be crystallographically nonequivalent. Conducting ion frequencies and the corresponding force constants have been determined for the analogous compounds MUP with M = K⁺, Na⁺, Ag⁺, NH⁺₄, Tl⁺ and H₃O⁺ and compared with other properties of these ionic conductors. Conductivity mechanisms in these materials are discussed.     

Raman spectroscopic study of the phosphate mineral churchite‐(Y) YPO4·2H2O

Raman spectroscopy has been used to study the rare‐earth mineral churchite‐(Y) of formula (Y,REE)(PO₄) ·2H₂O, where rare‐earth element (REE) is a rare‐earth element. The mineral contains yttrium and, depending on the locality, a range of rare‐earth metals. The Raman spectra of two churchite‐(Y) mineral samples from Jáchymov and Medvědín in the Czech Republic were compared with the Raman spectra of churchite‐(Y) downloaded from the RRUFF data base. The Raman spectra of churchite‐(Y) are characterized by an intense sharp band at 975 cm⁻¹ assigned to the ν₁ (PO₄³⁻) symmetric stretching mode. A lower intensity band observed at around 1065 cm⁻¹ is attributed to the ν₃ (PO₄³⁻) antisymmetric stretching mode. The (PO₄³⁻) bending modes are observed at 497 cm⁻¹ (ν₂) and 563 cm⁻¹ (ν₄). Some small differences in the band positions between the four churchite‐(Y) samples from four different localities were found. These differences may be ascribed to the different compositions of the churchite‐(Y) minerals. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman microscopy of the mixite mineral BiCu6(AsO4)3(OH)6·3H2O from the Czech Republic

Raman microscopy of the mixite mineral BiCu₆(AsO₄)₃(OH)₆·3H₂O from Jáchymov and from Smrkovec (both Czech Republic) has been used to study their molecular structure. The presence of (AsO₄)³⁻, (AsO₃OH)²⁻, (PO₄)³⁻ and (PO₃OH)²⁻ units, as well as molecular water and hydroxyl ions, was inferred. O H···O hydrogen bond lengths were calculated from the Raman and infrared spectra using Libowitzky's empirical relation. Small differences in the Raman spectra between both samples were observed and attributed to compositional and hydrogen‐bonding network differences. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman and infrared structural investigation of (PbO)x(ZnO)(0.6−x)(P2O5)0.4 glasses

The structure of ternary (PbO)_x(ZnO)_(0.6−x)(P₂O₅)_0.4glasses was investigated using Raman scattering and infrared spectroscopy over the compositional range x = 0–0.6. No significant change of the average chain length composed by PO₄ tetrahedral units with the substitution of zinc for the lead cation was observed. The linewidth and wavenumber variations of the Raman high‐wavenumber bands reflect the Zn/Pb substitution in these glasses and are correlated with the metal–oxygen force constant and local disorder. The infrared reflectivity spectra have been fitted with the four‐parameter dielectric function model. The variation in the 1000–1200 cm⁻¹wavenumber range has been attributed to an increase of the oscillator damping Γ_LO(PO₃)₂₋ as with PbO content vibrations rather than a variation of the chain length. Copyright © 2008 John Wiley & Sons, Ltd.     

Dy3+ emission in M5(PO4)3F (M = Ca, Ba) phosphor

Ultrafine M₅(PO₄)₃F:Dy³⁺ (M = Ca, Ba) phosphors were prepared via combustion process using metal nitrates as precursors. The formation of crystalline phosphate was confirmed by X-ray diffraction pattern. The PL excitation spectra show the excitation peaks observed at 250 to 400 nm due to f → f transition of Dy³⁺ ion, which are useful for solid-state lighting purpose (mercury free excitation). The PL emission of Dy³⁺ ion by 348 nm excitation gave an emission at 489 nm (blue), 582 nm (yellow) and 675 nm (red). All the characteristics of BYR emissions like BGR indicate that Dy doped Ca₅(PO₄)₃F and Ba₅(PO₄)₃F phosphors are good candidates that can be applied in solid-state lighting phosphor (mercury free excited lamp phosphor) and white light LED.      

Spectroscopic investigation of CaFeSn(PO4)3

Infrared and Raman spectra of CaFeSn(PO₄)₃ have been recorded and discussed with the aid of a site-symmetry analysis. The Mössbauer (⁵⁷₁₁₉Fe and ¹¹⁹Sn) spectra of this compound as well as the Sn-spectra of KSn₂(PO₄)₃ and TlSn₂(PO₄)₃ were also reported. The obtained spectroscopic information allows a deeper insight into the structural and electronic properties of this type of solids.     

31P AND 2H NMR Spectra of A Lyomesophase Containing Phosphoric Acid Monodecylester and H3PO4

This is a report on ³¹P nmr spectra of phosphoric acid monodecylester, PDE, and ²H quadrupolar splitting of D₂O in a lyomesophase developed from n-decylammonium chloride, PDE/H₃PO₄ and D₂O.Polarizing microcopic and ²H nmr studies showed that the mesophase was of lamellar-like structure but alignes as the temperature is increased. As the mesophase contained a minute amount of free H₃PO₄, the ³¹P nmr spectra gave a sharp peak and a hump. The latter was interpreted to arise from a slow tumbling process of PDE between different agglomerates in this system.     

Comparison of adsorption mechanism on colloidal silver surface of alafosfalin and its analogs

This study reports the Raman (FT‐RS) and absorption infrared (FT‐IR) spectra, based on calculated wavenumbers and normal modes of vibrations, of the following compounds: L ‐Ala‐L ‐NH‐CH(Me)‐PO₃H₂ (alafosfalin, A1), L ‐Ala‐D ‐NH‐CH(Me)‐PO₃H₂ (A2), L ‐Ala‐L ‐NH‐CH(Et)‐PO₃H₂ (A3), D ,L ‐Ala‐D,L ‐NH‐CH(Et)‐PO₃H₂ (A4), L ‐Ala‐D ‐NH‐CH(iPr)‐PO₃H₂ (A5), L ‐Ala‐D,L ‐NH‐CH(iPr)‐PO₃H₂ (A6), L ‐Ala‐D,L ‐NH‐CH(tBu)‐PO₃H₂ (A7), L ‐Ala‐D,L ‐NH‐CH(iBu)‐PO₃H₂ (A8), L ‐Ala‐D,L ‐NH‐CH(cBu)‐PO₃H₂ (A9), L ‐Ala‐D,L ‐NH‐CH(nPA)‐PO₃H₂ (A10), β‐Ala‐D ‐NH‐CH(Me)‐PO₃H₂ (A11), and D,L ‐Ala‐NH‐C(Me,Me)‐PO₃H₂ (A12). The equilibrium geometries and vibrational wavenumbers are calculated using density functional theory (DFT) at the B3LYP; 6–31 + + G** level of theory using Gaussian'03, GaussSum 0.8, and GAR2PED software. We briefly compare and analyze the experimental and calculated vibrational wavenumbers in the range of 3600–400 cm⁻¹. In addition, Raman wavenumbers are compared to those from surface‐enhanced Raman scattering (SERS) for the phosphonodipeptides of alanine (Ala) adsorbed on a colloidal silver surface. The geometry of these molecules etched on the silver surface is deduce from the observed changes in both the intensity and breadth of Raman bands in the spectra of the bound vs free species. For example, A7, A8, A1, A3, and A4 appear to adsorb onto the colloidal silver particles mainly through the phosphonate terminus, and for A3 and A4, through the  C‐NH₂ and  CONH fragments. The most dominant SERS bands of A5, A6, A9, A10, and A11 are due to the amide bond vibrations, as well as to the vibrations of the  C‐NH₂ group (A9 and A10) and the C C group (A6 and A11). The differences recorded for the A5, A6, A9, A10, and A11 and those of A2 and A12 are due to interactions between the amine and methyl groups with the silver surface, and they reflect vibrational characteristic of these groups. Copyright © 2008 John Wiley & Sons, Ltd.     

光电子成像研究AgOCH3-和Ag-(CH3OH)x (x=1, 2)

用光电子成像技术和从头算法研究Ag^-(CH₃OH)_x (x=1, 2)和AgOCH₃^-. 从AgOCH₃^-振动分辨的光电子谱得 到AgOCH₃^-的绝热和垂直电离能分别为1.29(2)和1.34(2) eV. Ag^-(CH₃OH)_{1,2相似文献}   

FT‐Raman spectroscopic spectra on 3‐phenylpropylamine inclusion compounds

Some new Hofmann‐3‐phenylpropylamine‐type clathrates with chemical formulae of M(3‐phenylpropylamine)₂ Ni(CN)₄. 2G (MNi or Co, G = 1,2‐dichlorobenzene or 1,3‐dichlorobenzene) have been prepared and their Fourier transform infrared(FT‐IR; 4000–400 cm⁻¹), far‐infrared (600–100 cm⁻¹) and FT‐Raman (4000–60 cm⁻¹) spectra are reported. The ligand molecule, guest molecules, polymeric sheet and metal‐ligand bands of the clathrates are assigned in detail. The compounds are also characterized by thermal gravimetric analysis (TGA), differential thermal analysis (DTA), elemental analysis and magnetic susceptibility measurements. From the results, the monodentate 3‐phenylpropylamine ligand molecule bonds to the metal atom of |M‐Ni(CN)₄ | _∞ polymeric layers in the trans‐gauche‐gauche (TGG) form, and 1,2‐dichlorobenzene or 1,3‐dichlorobenzene molecules are guested by this structure revealing the inclusion ability of the host complexes. Copyright © 2010 John Wiley & Sons, Ltd.     

Conformational equilibria in dihaloheptasilanes X2Si[SiMe(SiMe3)2]2 with X = F,Cl, Br,I: A Raman spectroscopic and quantum chemical DFT study

Equilibrium geometries, stabilities and vibrational wavenumbers for conformers of the dihaloheptasilanes X₂Si[SiMe(SiMe₃)₂]₂ with X = F, Cl, Br and I were calculated at the density functional B3LYP level employing 6‐311G(d) basis sets and SDD pseudopotentials for Br and I. Two spectroscopically distinct low‐energy conformers were located for all four heptasilanes with energy differences of 5.5, 4.7, 1.9 and 1.2 kJ mol⁻¹ for X = F, Cl, Br and I, respectively. Five more conformers were found for difluoroheptasilane and four for X = Cl, Br and I. They all have relative energies larger than 7.5 and up to 17 kJ mol⁻¹ and are negligibly populated at room temperature. Variable temperature solution Raman spectra (−70 to + 100 °C) in a wavenumber range typical for Si Si stretching vibrations (280‐350 cm⁻¹) confirm these results. For X = Br and I, no temperature effects at all could be observed as a very rapid inter‐conversion between the two low‐energy conformers, which is fast even on the time scale of Raman spectroscopy, occurs. For X = Cl, rapid inter‐conversion also occurs, and a third conformer could be detected at higher temperatures (50–100 °C). For X = F, intensity changes with temperature are consistent with the presence of two low‐energy conformers. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation of Ag3PO4/CoWO4 S-scheme heterojunction and study on sonocatalytic degradation of tetracycline

In this study, 0.6Ag₃PO₄/CoWO₄ composites were synthesized by hydrothermal method. The prepared materials were systematically characterized by techniques of scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), N₂ adsorption/desorption, and UV–vis diffuse reflectance spectrum (DRS). Furthermore, the sonocatalytic degradation performance of 0.6Ag₃PO₄/CoWO₄ composites towards tetracycline (TC) was investigated under ultrasonic radiation. The results showed that, combined with potassium persulfate (K₂S₂O₈), the 0.6Ag₃PO₄/CoWO₄ composites achieved a high sonocatalytic degradation efficiency of 97.89 % within 10 min, which was much better than bare Ag₃PO₄ or CoWO₄. By measuring the electrochemical properties, it was proposed that the degradation mechanism of 0.6Ag₃PO₄/CoWO₄ is the formation of S-scheme heterojunction, which increases the separation efficiency of electron-hole pairs (e^--h⁺) and generates more electrons and holes, thereby enhancing the degradation activity. The scavenger experiments confirmed that hole (h⁺) was the primary active substance in degrading TC, and free radicals (OH) and superoxide anion radical (O₂^–) were auxiliary active substances. The results indicated that 0.6Ag₃PO₄/CoWO₄ nanocomposites could be used as an efficient and reliable sonocatalyst for wastewater treatment.     

Vibrational characterization of L‐valine phosphonate dipeptides: FT‐IR,FT‐RS,and SERS spectroscopy studies and DFT calculations

Four L ‐valine (L ‐Val) phosphonate dipeptides that are potent inhibitors of zinc metalloproteases, namely, L ‐Val‐C(Me)₂‐PO₃H₂ (V1), L ‐Val‐CH(iP)‐PO₃H₂ (V2), L ‐Val‐CH(iB)‐PO₃H₂ (V3), and L ‐Val‐C(Me)(iP)‐PO₃H₂ (V4), are studied by Fourier‐transform infrared (FT‐IR) spectroscopy, Fourier‐transform Raman spectroscopy (FT‐RS), and surface‐enhanced Raman scattering (SERS). The band assignment (wavenumbers and intensities) is made based on (B3LYP/6‐311 + + G**) calculations. Comparison of theoretical FT‐IR and FT‐RS spectra with those of SERS allows to obtain information on the orientation of these dipeptides as well as specific‐competitive interactions of their functionalities with the silver substrate. More specifically, V1 and V4 appear to interact with the silver substrate mainly via a  C_sgCH₃ moiety localized at the  N_amideC_sg(CH₃)P molecular fragment. In addition, the  POH and isopropyl units of V4 assist in the adsorption process of this molecule. In contrast, the  C_αNH₂ and  PO₃H⁻ groups of V2 and V3 interact with the silver nanoparticles, whereas their isopropyl and isobutyl fragments seem to be repelled by the silver substrate (except for the  CH₂  of V3), similar to the  C_β(CH₃)₂ fragment of L ‐Val for all L ‐Val phosphonate dipeptides investigated in this work. The adsorption mechanism of these molecules onto the colloidal silver surface is also affected by amide bond behavior. Copyright © 2010 John Wiley & Sons, Ltd.     

Coordination and solvation of noble metal ions: Infrared spectroscopy of Ag+(H2O)n

Vibrational spectra of mass-selected Ag⁺(H₂O)_n ions are measured by infrared photodissociation spectroscopy and analyzed with the aid of density functional theory calculations. Hydrogen bonding between H₂O molecules is found to be absent for cold Ag⁺(H₂O)₃, but detected for Ag⁺(H₂O)₄ through characteristic changes in the position and intensity of OH-stretching transitions. The third H₂O coordinates directly to Ag⁺, but the fourth H₂O prefers solvation through hydrogen bonding. The preference of the tri-coordinated form is attributed to the inefficient 5s–4d hybridization in Ag⁺, in contrast to the efficient 4s–3d hybridization in Cu⁺. For Ag⁺(H₂O)₄, however, di-coordinated isomers are identified in addition to the tri-coordinated one.     

Proof‐of‐Concept Studies Directed toward the Formation of Metallic Ag Nanostructures from Ag3PO4 Induced by Electron Beam and Femtosecond Laser

In this work, for the first time, the instantaneous nucleation and growth processes of Ag nanoparticles on Ag₃PO₄ mediated by femtosecond laser pulses are reported and analyzed. The investigated samples are pure Ag₃PO₄ sample, electron‐irradiated Ag₃PO₄ sample, and laser‐irradiated sample. Complete characterization of the samples is performed using X‐ray diffraction (XRD), Rietveld refinements, field emission scanning electron microscopy, and energy dispersive spectroscopy (EDS). XRD confirms that the irradiated surface layer remains crystalline, and according to EDS analysis, the surface particles are composed primarily of Ag nanoparticles. This method not only offers a one‐step route to synthesize Ag nanoparticles using laser‐assisted irradiation with particle size control, but also reports a complex process involving the formation and subsequent growth of Ag nanoparticles through an unexpected additive‐free in situ fabrication process.     

Vibrational spectroscopic study of lithium intercalation into LiTi2(PO4)3

Ex situ vibrational spectra are recorded during the first discharge of LiTi₂(PO₄)₃. Spectral changes are consistent with a two-phase model for the electrochemical insertion of Li⁺ ions. Differences in the frequencies and relative intensities of the LiTi₂(PO₄)₃ and Li₃Ti₂(PO₄)₃ bands are due to changes in the effective force constants, dipole moment derivatives, and polarizability derivatives as Li⁺ is inserted into LiTi₂(PO₄)₃. The intramolecular PO₄³⁻ bending modes (ν₂ and ν₄) are found to be more sensitive to Li⁺ insertion than the intramolecular PO₄³⁻ stretching modes (ν₁ and ν₃). This is because ν₂ and ν₄ are less localized than ν₁ or ν₃ and are more susceptible to small structural changes in the unit cell. Furthermore, a band at 487 cm^− 1 appears in the infrared spectrum of Li₃Ti₂(PO₄)₃. This band is assigned as a Li⁺ ion cage mode and is due to Li⁺ ions that occupy the M(3) and M′(3) sites in the Li₃Ti₂(PO₄)₃ structure. A small degree of band broadening is also detected in the vibrational spectra when Li⁺ ions are inserted, which might indicate some disordering in the cathode material.     

Light scattering spectra of polarization fluctuations and models of the phase transition in KDP type ferroelectrics

Abstract

Recent light scattering studies in KH₂PO₄ type hydrogen-bonded crystals are reviewed. Dynamical properties of these crystals have been discussed in terms of the coupled tunneling proton-optical phonon model up to date. Light scattering spectra in several GHz and cm^?1 regions with various scattering geometries observed in KH₂PO₄, KD₂PO₄ and their mixed crystals, however, revealed that all these spectra are well analysed in terms of a coupled polarization relaxation mode-acoustic phonon system. Since most of the spontaneous polarization is due to shifts of K, P and O ions, relaxation motions of H₂PO₄ dipoles arc concluded to be the origin of these low-frequency spectra. Models of the phase transition mechanism are discussed on the basis of these results and other recent experimental studies including the explanation of large isotope effects in these crystals.     

Control of photoluminescence in Ca3–3x /7Y2x /7(PO4)2:Eu2+ phosphors by migration of the dopant

A series of Ca_{3–3x /7}Y_{2x /7}(PO₄)₂:Eu²⁺ phosphors were synthesized by conventional solid‐state reaction. The photoluminescence spectra elucidate that the evolution of emission hue from violet–blue to blue–greenish could be realized by incorporating Y³⁺ ions. The aliovalent substitution of Y³⁺ for Ca²⁺ forms cationic vacancies (h denotes a vacancy) at Ca(4) site according to the formula 3Ca²⁺ = 2Y³⁺ + h, and then facilitates the migration of dopant Eu²⁺ from Ca(4) site to other sites in host lattice. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)