Solid Diffuse Reflectance Spectra Research Articles

Photocatalytic Performance of the BaSn-based Nanoscale Materials for the Organic Pollutants Enhanced by Sm (Er) Doping

Background: Sm (Er) doping is an effective strategy for enhancing the photocatalytic activity of the semiconductor photocatalysts for the degradation of organic pollutants. BaSnbased nanorods possess wide band gap energy, which limits the photocatalytic application. It is important to research the feasibility of the improved photocatalytic performance of the BaSnbased nanorods by doping with Sm (Er). Objective: The aim is to synthesize Sm (Er)-doped BaSn-based nanoscale materials through a simple hydrothermal process and research the photocatalytic performance of the Sm (Er)-doped BaSn-based nanoscale materials for the gentian violet degradation. Methods: Sm (Er)-doped BaSn-based nanoscale materials with a polycrystalline structure were synthesized through a simple hydrothermal process. The Sm (Er)-doped composites were analyzed by X-ray diffraction, electron microscopy, solid diffuse reflectance spectrum, X-ray photoelectron spectroscopy, photoluminescence, and electrochemical impedance spectroscopy. Results: Sm (Er) doping induces the morphological evolution of the BaSn-based nanoscale materials from the nanorods to irregular nanoscale particles. Sm (Er) in the doped BaSn-based nanoscale materials exists in the form of the cubic Sm2Sn2O7 and orthorhombic ErF3 phases. The band gap value is decreased with increasing the Sm (Er) dopant contents. Sm (Er)-doped BnSnbased nanoscale materials with the Sm (Er) content of 8wt.% have the lowest band gap and show the strongest light absorption ability. Compared with the un-doped BaSn-based nanoscale materials, the Sm (Er)-doped BnSn-based nanoscale materials exhibit higher photocatalytic activity for the gentian violet degradation. 8wt.% Sm-doped BnSn-based nanoscale materials show the highest photocatalytic activity for the degradation of the gentian violet. 20 mL gentian violet solution (concentration of 10 mg·L-1) can be totally degraded using 20 mg 8wt.% Sm-doped BnSnbased nanoscale materials under UV light illumination for 150 min. Conclusion: The enhanced photocatalytic activity of the Sm (Er)-doped BnSn-based nanoscale materials can be attributed to the decreased band gap, enhanced light absorption ability, and decreased recombination of the photo-generated electron-hole pairs.

In-situ Photo-deposition of Nd-modified Hexahydroxy Strontium Stannate Nanorods with Enhanced Photocatalytic Performance

Background:: Metal surface modification of the photocatalysts is effective for enhancing the photocatalytic properties of the semiconductor photocatalysts. Nd can be used as the modified metal for the enhancement of catalytic performance of the strontium tin hydroxide (SrSn(OH)6) nanorods due to expanding the light absorption range and reducing the recombination of the photo-generated electrons and holes. Objective:: The aim of the research is to synthesize Nd-modified SrSn(OH)6 nanorods and investigate the enhanced photocatalytic performance for crystal violet degradation. Methods:: Nd modified SrSn(OH)6 nanorods were prepared via a facile one-step in-situ photodeposition route. The obtained nanorods were analyzed by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, solid diffuse reflectance spectra, photoluminescence spectroscopy, and electrochemical impedance spectroscopy. Results:: Nd attached to the surface of nanorods. The band gap of the Nd-modified SrSn(OH)6 nanorods was reduced due to Nd modification at the surface of nanorods. The Nd-modified SrSn(OH)6 nanorods showed enhanced photocatalytic properties for crystal violet (CV) degradation under ultraviolet (UV) light irradiation than the SrSn(OH)6 nanorods. Nd modified SrSn(OH)6 nanorods have lower charge transfer resistance and more efficient charge separation ability, thus hindering the recombination of the electrons and holes (e−/h+) pairs. Scavenger experiments reported that the holes, superoxide, and hydroxyl radicals are the main reactive species during the photocatalytic reaction. The Ndmodified SrSn(OH)6 nanorods were found to be recoverable and reusable for CV degradation. Conclusion:: The Nd modified SrSn(OH)6 nanorods showed enhanced photocatalytic performance towards crystal violet than un-modified nanorods.

Preparation of La2O3-modified BaSn Composite Nanorods and Photocatalytic Properties toward Crystal Violet

Background: The separation efficiency of the electron and hole pairs of the BaSn composite nanorods is limited due to a wide band gap energy restricting the photocatalytic treatment ability of the composite nanorods. It is an efficient route to improve the photocatalytic properties of the semiconductor photocatalysts by La2O3 modification. Objective: This study aims to synthesize La2O3-modified BaSn composite nanorods through a simple method and research the photocatalytic performance of the La2O3-modified BaSn composite nanorods for crystal violet degradation. Methods: La2O3 modified BaSn composite nanorods were synthesized by a facile method using lanthanum acetate as the lanthanum raw material and evaluated by electron microscopy, solid diffuse reflectance spectra, X-ray diffraction, photoluminescence and photocatalytic measurement for crystal violet degradation under ultraviolet light irradiation. Results: BaSn composite nanorods consist of orthorhombic SnO2, monoclinic BaSn(OH)6, and monoclinic Ba(OH)2. La2O3 suppresses the growth of the monoclinic BaSn(OH)6, and orthorhombic SnO2. The La2O3-modified BaSn composite nanorods possess coarse surface covered with the La2O3 nanoscale particles with an average size of about 50 nm. The absorption edge red-shifts to 373 nm and the band gap energy reaches 3.32 eV of the La2O3 modified BaSn composite nanorods compared with the BaSn composite nanorods. 20 mL 10 mg·L-1 crystal violet solution can be entirely removed by 20 mg composite nanorods with 15wt.% La2O3 content under ultraviolet light irradiated for 120 min. The reaction rate constant is 2.4 times higher than that of the non-modified composite nanorods. Hydroxyl radicals and holes are the reaction active substances for crystal violet degradation in the composite nanorod reaction system. Conclusion: La2O3 modification decreases the band gap energy, enhances the light absorption ability, and suppresses the recombination of the electron and hole pairs of the composite nanorods.

Rare metal doping of the hexahydroxy strontium stannate with enhanced photocatalytic performance for organic pollutants

Rare metal (La or Nd) doped hexahydroxy strontium stannate with different dopant contents was synthesized via a facile hydrothermal route. The rare metal doped samples were investigated by X-ray diffraction (XRD), electron microscopy, solid diffuse reflectance spectrum, X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) spectroscopy. The morphology of the doped samples is closely relative to the rare metal dopant content transferring from the nanorods to nanoflakes and nanoscale particles for La and Nd doping, respectively. 2wt.% rare metal doped hexahydroxy strontium stannate possesses the smallest band gap value with 3.26 eV (La doping) and 3.25 eV (Nd doping) which enhances the charge carriers transfer efficiency. The rare metal doped hexahydroxy strontium stannate shows enhanced photocatalytic performance for the crystal violet degradation under ultra-violet (UV) light irradiation. 2wt.% rare metal doped hexahydroxy strontium stannate has the best photocatalytic activity for the removal of crystal violet under UV light irradiation for 120 min. The rare metal doped hexahydroxy strontium stannate possesses high stability, and is reusable for the crystal violet degradation.

Synthesis, structure, and spectral and electrochemical properties of chromium(III) tris-(8-hydroxyquinolinate).

The kinetically inert chromium(III) tris-(8-hydroxyquinolinate), Crq3, has been synthesized, crystallized from 90% methanol-water, and characterized by MALDI-TOF mass spectrometry, thermogravimetry, FTIR, NMR spectroscopy, and X-ray powder diffraction. It is formed as a methanol solvate, but the solvent can be removed by heating. Large paramagnetic shifts and spectral broadening in (1)H NMR spectra indicate electron delocalization between the metal and the ligand. DFT calculations show it is present as the meridional isomer, with the HOMO largely based on one of the metal 3d orbitals and the LUMO essentially localized on the ligands. Cyclic voltammetry (CV) in acetonitrile solutions shows four oxidation peaks and two, less intense reduction waves on the first scan. The HOMO energy determined from the first oxidation peak is fairly close to that obtained by DFT, in agreement with this being mainly metal based. Although the number of peaks decreases on subsequent CV scans, the complex shows markedly enhanced electrochemical stability compared with aluminium(III) tris-(8-hydroxyquinolinate). Solution UV/visible absorption and solid diffuse reflectance spectra have a weak, long wavelength band, assigned to the metal based d-d transition, in addition to the normal, ligand based bands seen in metal quinolates. The energy of the lowest energy band is identical to the HOMO-LUMO separation obtained by cyclic voltammetry, in agreement with the above description. The compound is only weakly luminescent, in contrast to many other metal quinolates, due to the lowest energy transition being metal rather than ligand based. The potential of this compound as an electron transporting/hole blocking layer in optoelectronic devices is indicated.

Two inorganic–organic hybrid materials based on polyoxometalate anions and methylene blue: Preparations, crystal structures and properties

Two novel inorganic–organic hybrid materials based on an organic dye cation methylene blue (MB) and Lindqvist-type POM polyanions, [C 22H 18N 3S] 2Mo 6O 19 2DMF (1) and [C 22H 18N 3S] 2W 6O 19 2DMF (2) were synthesized under ambient conditions and characterized by CV, IR spectroscopy, solid diffuse reflectance spectrum, UV–vis spectra in DMF solution, luminescent spectrum and single crystal X-ray diffraction. Crystallographic data reveal that compounds 1 and 2 are isostructural and both crystallize in the triclinic space group P1¯. Their crystal structures present that the layers of organic molecules and inorganic anions array alternatively, and there exist strong π···π stacking interactions between dimeric MB cations and near distance interactions among organic dye cations, Lindqvist-type POM polyanions and DMF molecules. The solid diffuse reflectance spectra and UV–vis spectra in DMF solution appear new absorption bands ascribed to the charge-transfer transition between the cationic MB donor and the POM acceptors. Studies of the photoluminescent properties show that the formation of 1 and 2 lead to the fluorescence quenching of starting materials.

Synthesis and characterization of two charge-transfer salts based on Keggin-type polyoxometalates and morpholinebiguanide

Two new inorganic-organic salts, formulated as (C6H13N5OH)2 [HPMo12O40] · 5H2O and (C6H13N5OH)3[PW12O40], were synthesized and characterized by elemental analysis, IR, ESR, diffuse reflectance spectra, thermogravimetry, and X-ray photoelectron spectroscopy. Solid diffuse reflectance spectra showed charge-transfer interactions between the inorganic and organic moieties in the solid state. Salt I had strong photosensitivity for UV light or X-ray irradiation, and its photochromic reaction under UV light was found to exhibit first-order kinetics.

Synthesis and characterization of two new photochromic inorganic-organic hybrid materials based on Keggin-type polyoxometalates

Two new photochromic inorganic-organic hybrid materials formed from Keggin-type polyoxometalates(POMs) and metronidazole (C6H9N3O3, MNZ), formulated as H3PMo12O40·3MNZ·3H2O(1) and H3PW12O40·3MNZ·3H2O(2), were synthesized and characterized by elemental analysis, IR spectra, electronic spectra, electron spin resonance (ESR) spectra and thermogravi-metry-differential thermal analysis (TG-DTA). Reflectance spectra show the presence of weak intermolecular charge transfer between the organic and inorganic moieties in the solid state. The photochromic properties were studied by solid diffuse reflectance spectra and ESR spectra, and the photochromic reactions were found to exhibit first-order kinetics. TG-DTA showed that two hybrid materials have similar thermal behavior.

Synthesis and molecular structure of a plutonium(IV) coordination complex: [Pu(NO3)2(2,6-[(C6H5)2P(O)CH2]2C5H3NO)2](NO3)2x1.5H2Ox0.5MeOH.

The trifunctional ligand 2,6-[(C6H5)2P(O)CH2]2 C5H3NO (1), in a mixed EtOH/MeOH solvent system, when combined with an aqueous nitric acid solution of Pu(IV), produces a 2:1 coordination complex, [Pu(1)2(NO3)2](NO3)2. A single crystal of [Pu(NO3)2(2,6-[(C6H5)2P(O)CH2]2C5H3NO)2](NO3)2x1.5H2Ox0.5MeOH was characterized by X-ray diffraction analysis. The crystal is monoclinic, space group P2(1)/n, with a = 19.1011(9) A, b = 18.2873(9) A, c = 21.507(1) A, alpha = gamma = 90 degrees, beta = 108.64(1) degrees, and Z = 4. Two neutral ligands (1) are bonded to the Pu(IV) ion in a tridentate fashion. Two nitrate ions also occupy inner sphere coordination positions, while two additional NO3- ions reside in the outer sphere. Comparison of the solution optical absorbance and solid diffuse reflectance spectra shows the same Pu(IV) chromophore exists in both solid and solution states.

Preparation and properties of metal complexes with 6-methyl-2-aminomethylpyridine—II: Four-, five-, and six-co-ordinated cobalt(II) complexes[1

The preparation and properties of eight new complexes Co(mepic) 2 X 2. nH 2O (mepic = 6-methyl-2-aminomethylpyridine; X = Cl, Br, NCS, NO 3, and ClO 4; n = 0–2·5 and Co(mepic) 2 XClO 4 ( X = Cl, Br, and I) are reported. Magnetic susceptibility measurement hows that all of them have high-spin configuration corresponding to three unpaired electrons. The solid diffuse reflectance spectra and the i.r. spectra reveal that in the solid state Co(mepic) 2(ClO 4) 2 is a four-co-ordinated tetrahedral complex, whereas Co(mepic) 2 XClO 4 are five-co-ordinated complexes which have pseudotrigonal-bipyramidal configuration. On the other hand, four complexes Co(mepic) 2 X 2. nH 2O ( X = Cl, Br, NCS, and NO 3) are six-co-ordinate; the surroundings of the cobalt ions are discussed. In the aqueous solutions, all of them exhibit the same electronic spectra, showing that the solvolysis and the stereochemical changes leading to the same product occur. The main species thus formed in the aqueous solutions seems to be a six-co-ordinated complex [Co(mepic) 2(H 2O) 2] 2+. In the nitromethane solutions, however, the situation is quite different here; the absorption spectra of Co(mepic) 2(NO 3) 2 and Co(mepic) 2(ClO 4) 2 are nearly identical with those of the solid reflectance spectra; the former is octahedral and the latter is tetrahedral in this solvent. It is shown that the complexes [Co(mepic) 2 X]ClO 4 seem to disproportionate in part in nitromethane solution into tetrahedral [Co mepic X 2] and octahedral [Co(mepic) 3] 2+. The stereochemistry of all the complexes is discussed.