Li 2 SiO 3 nanopowders were synthesized via a non-stoichiometric 2:3 (S 1 ), 1:3 (S 2 ), 1:4 (S 3 ) and 1:5 (S 4 ) Li/Si molar ratios via hydrothermal reaction for 72 h at 180°C in an aqua solution using Li 2 CO 3 and H 2 SiO 3 as raw materials. The synthesized materials were characterized by powder X-ray diffraction (PXRD) technique and Fourier transform infrared spectroscopy. PXRD data showed that the crystal structure of the obtained materials is orthorhombic with the space group of Cmc2 1 . Also, to investigate the effect of the Li/Si molar ratio on the morphology of the obtained materials, the morphologies of the synthesized materials were studied by field emission scanning electron microscopy. The technique showed that with changing the Li/Si molar ratio from S 1 to S 4 , the morphology of as-prepared samples changed from flower structures to microrod-microsphere and then to a nonhomogenous layer-like structure. Ultraviolet-visible spectra showed that the nanostructure lithium silicate powders had good light absorption properties in the ultraviolet light region. It showed that with changing the Li/Si molar ratio from S 1 to S 4 , the calculated band gap was decreased. Also, cell parameter refinement showed that with changing the Li/Si molar ratio from S 1 to S 4 the cell parameters decreased. Photoluminescence analysis of the obtained materials was studied at the excitation wavelength of 247 nm. It showed that the emission spectra of the obtained materials had a blue shift from S 1 to S 4 .
UV-vis and photoluminescence spectra of the hydrothermally synthesized crystalline lithium metasilicate (Li 2 SiO 3 ) and lithium disilicate (Li 2 Si 2 O 5 ) nanomaterials are studied. The intensity of the bands in the emission spectra increases with increasing reaction time in both compounds. The electronic band structure along with density of states calculated by the density functional theory (DFT) method indicates that Li 2 SiO 3 and Li 2 Si 2 O 5 have an indirect energy band gap of 4.575 and 4.776 eV respectively. The optical properties, including the dielectric, absorption, reflectivity, and energy loss spectra of the compounds, are calculated by DFT method and analyzed based on the electronic structures.
Using LiNO 3 and SiO 2 as raw materials, Li 2 SiO 3 nano-powders were synthesized via a nonstoichiometric 2:3 Li:Si molar ratio hydrothermal reaction at 180°C for 48, 72, and 96 h in a NaOH aqueous solution system. The synthesized materials were characterized by powder X-ray diffraction technique and Fourier transform infrared spectroscopy. To investigate the effect of the reaction time on the morphology of the obtained materials, the morphologies of the synthesized materials were studied by field emission scanning electron microscopy technique. The technique showed that on increasing the reaction time, the morphology of the as-prepared samples changed from belt structures to flower structures. Ultraviolet-Visible spectra analyses showed that the nanostructured lithium silicate powders had good light absorption properties in the ultraviolet light region. Also, photo luminescence spectra and cell parameter refinement of the obtained materials were studied.
The hydrothermal synthesis and optical properties of undoped and Sb 3+ -doped lithium metasilicate and lithium disilicate nanomaterials were investigated. The microstructures and morphologies of the synthesized Li 2−2x Sb 2x SiO 3 and Li 2−2x Sb 2x Si 2 O 5 nanoparticles were studied with powder X-ray diffraction and scanning electron microscopy techniques, respectively. The synthesized undoped and doped lithium metasilicate and lithium disilicate nanomaterials, respectively, are isostructural with the standard bulk Li 2 SiO 3 (space group Cmc2 1 ) and Li 2 Si 2 O 5 (space group Ccc2) materials. The electronic absorption and photoluminescence spectra of the synthesized materials are studied. The measured optical properties show dependence on the dopant amounts in the structure.
The present work introduces a one-step and facile hydrothermal procedure as a green process for the first time to synthesize nickel(II) oxide (NiO) nanoparticles. The as-prepared nanomaterials were used as high efficient, low toxic and cost catalyst for the synthesis of some organic compounds. Ni(NO3)2 and some natural extract were used as a surfactant for the first time to synthesis NiO nanomaterials. A high synthesis yield (91%) was obtained for S2. Rietveld analysis affirmed the cubic crystal system of the obtained NiO nanocatalyst. The morphology studies were carried out with the FESEM method and the images revealed a change from non-homogenous to homogenous spherical particles when the Barberryas was used instead of orange blossom surfactant. Besides, the images revealed that the particle size distribution was in the range of 20 to 60 nm. The synthesized catalysts were used for the first time in Biginelli multicomponent reactions (MCRs) for the preparation of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) under the present facile reaction conditions. High yield (97%) of the final product was achieved at the optimum condensation reaction conditions (Catalyst: 60 mg; temperature: 90 °C and time: 90 min) when ethyl acetoacetate/methyl acetoacetate (1 mmol), benzaldehyde (1 mmol) and urea (1.2 mmol) were used. A kinetic study affirmed pseudo-first-order model for Biginelli reactions followed the pseudo-first-order model.
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