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To the best of our knowledge, we report for the first time the growth of brownmillerite Ca2Fe2O5 (CFO) single crystals under Argon (Ar) only ambience by optical floating zone (OFZ) technique and compare its structural and spectroscopic properties with CFO single crystals grown by OFZ method under air and oxygen (O2) atmospheres. Single-crystal X-ray diffraction confirms growth of Ca2Fe2O5 single crystals in all the atmospheres. Crystals grown in air and oxygen (O2) atmospheres show both metallic Fe0 and Fe3+states, whereas in Ar-grown crystals only Fe3+ oxidation state is observed. An enhancement in oxygen vacancies is also observed in Ar-grown crystals. Growth ambience is found to have a strong influence on cationic environment and binding energy of constituent elements, as is evident from the X-ray photoelectron spectroscopy of the Ca2Fe2O5 crystals. [ABSTRACT FROM AUTHOR]

Ideal sillenite type Bi12FeO20 (BFO) micron sized single crystals have been successfully grown via inexpensive hydrothermal method. The refined single crystal X-ray diffraction data reveals cubic Bi12FeO20 structure with single crystal parameters. Occurrence of rare Fe4+ state is identified via X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The lattice parameter (a) and corresponding molar volume (Vm) of Bi12FeO20 have been measured in the temperature range of 30–700 °C by the X-ray diffraction method. The thermal expansion coefficient (α) 3.93 × 10–5 K−1 was calculated from the measured values of the parameters. Electronic structure and density of states are investigated by first principle calculations. Photoelectrochemical measurements on single crystals with bandgap of 2 eV reveal significant photo response. The photoactivity of as grown crystals were further investigated by degrading organic effluents such as Methylene blue (MB) and Congo red (CR) under natural sunlight. BFO showed photodegradation efficiency about 74.23% and 32.10% for degrading MB and CR respectively. Interesting morphology and microstructure of pointed spearhead like BFO crystals provide a new insight in designing and synthesizing multifunctional single crystals. [ABSTRACT FROM AUTHOR]

We utilize the high temperature flux growth technique to grow oriented brownmillerite CaFeO2.5 single-crystals. We have performed a series of growths and analyses to obtain quality single-crystals. Qualitative structural and spectroscopic characterizations have been carried out to study as-grown single-crystals. Morphological studies show clear two-dimensional step-like surface with uniform elemental distribution. As-grown single-crystals have also been characterized by thermogravimetric analysis (TGA), Raman and Fourier transform infrared spectroscopy (FTIR) and the results are presented. To the best of our knowledge, the growth of oriented CaFeO2.5 single-crystals by isothermal evaporation technique of flux growth and its spectroscopic studies have not been reported yet. [ABSTRACT FROM AUTHOR]

An amendment to this paper has been published and can be accessed via a link at the top of the paper. [ABSTRACT FROM AUTHOR]

• Enhanced degradation of persistent aqueous pollutants such as Bisphenol A (84%). • Photodegradation of Norfloxocin (82%) by visible light active BGO. • Regular pyramidal like growth of BGO micro crystal via hydrothermal synthesis. • Band gap variation achieved by adapting different synthesis routes. Among the numerous photocatalytic materials studied for potential application in degradation of organic effluents and antibiotic wastes, sillenite materials emerge as important candidates. In the present work, Ga based sillenite has been used to degrade aqueous persistent organic pollutants such as bisphenol (BPA) and Norfloxacin (NF) in presence of natural solar irradiation. Sillenite based oxides have exhibited various physico chemical applications due to their photocatalytic nature. Here, gallium based sillenite, Bi 24 Ga 2 O 39 , has been successfully synthesized through two different techniques, hydrothermal route (HY) and solid state reaction (SS) method. X-Ray Diffraction patterns and Rietveld refinement of same revealed the occurrence of sillenite single phase. Morphological investigation by Scanning Electron Microscopy revealed regular tetrahedral morphology of HY sample. X-ray photoelectron and Raman spectroscopy were performed to analyze the chemical composition and its environment. UV–Visible spectroscopy on sillenites was used to analyze and calculate the effective optical band gap energy ~2.55 eV (HY) and ~2.76 eV (SS) respectively. Photoelectrochemical measurements performed on the samples showed appreciable photocurrent response (~1.9 μA/cm2 for HY sample). The photoactivity of samples have been utilized for degradation of aqueous persistent organic pollutants, such as methylene blue, norfloxacin and bisphenol A in presence of visible light degrading upto 92%, 82% and 84% (HY) respectively. [ABSTRACT FROM AUTHOR]