Effect of hydrothermal temperature treatment on the variance of fluorescence in Ca2SiO4:Tb3þ

Investigations of structural defects and their associated impact on the optical properties of optical materials are essential expediencies because different methods are involved in the preparation of those materials for display applications. Lanthanide ion doping is a simple structural probing strategy that facilitates the challenges of identifying the structural defects. Pure and terbium (Tb3+) doped Ca2SiO4 (C2S) particles were prepared using Pechini (C2SP) and hydrothermal methods (C2SH). From SEM images, it is observed that the Tb3+ doped C2SP particles were highly agglomerated, more than the C2SH particles. The TEM study confirmed that the particle size decreased for C2SH prepared at the high hydrothermal temperatures of 180 and 200 °C (C2S:180H and C2S:200H). Fluorescence emission quenching occurred for Tb3+ doped C2S:180H and C2S:200H. The emission intensity was high for Tb3+ doped C2SH prepared at 140 °C compared to Tb3+ doped C2SP, C2S:180H and C2S:200H. The changes in the O2p orbitals, associated with the upper-level valence band spectra of the tetrahedral silicate of pure C2SP and C2S:180H, were experimentally evaluated in the X-ray photoelectron spectroscopy (XPS)-valence band spectra. The symmetry lowering owing to the distortion in the silicate unit quenched the emission, which was confirmed by XPS-valence band spectra and Tb3+ emission lines. This study suggests that the Pechini method is more suitable to prepare the Tb3+ doped C2S phosphors compared to the hydrothermal method, particularly at high temperature for solid state display and scintillator applications

Process monitoring of cobalt carbonate precipitation by reactions between cobalt sulfate and sodium carbonate solutions to control product morphology and purity

| openaire: EC/H2020/842140/EU//OMECRY Funding Information: Zhang Jianxin wishes to acknowledge the funding from CSC (China Scholarship Council, No. 201806370220). The authors would like to thank Chemobrionics COST Action CA17120. This project has also received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 842140. The work was supported by the Academy of Finland's RawMaTERS Finland Infrastructure (RAMI) and the Bioeconomy Facilities at Aalto University, Espoo, Finland. Publisher Copyright: © 2023 The Author(s)Recovering critical elements from EV batteries is challenging as the separation is a complex process which involves different processing parameters. Cobalt (Co) is one of the metals which ensures the life of EV batteries and here we have successfully precipitated cobalt carbonate (CoCO3) by semi-batch precipitation using cobalt sulfate and sodium carbonate as reactant solutions. The precipitation of cobalt carbonate was investigated by offline Raman spectroscopy, Powder X-ray diffraction analysis, inline Focused Beam Reflectance Measurement (FBRM), and pH measurements. In addition, the effects of various factors including pH, aging time, reactant addition time, mixing speed, and temperature on cobalt carbonate precipitation and the properties of the precipitated solids were investigated. In the process of precipitation, the carbonate ions in the initial electrolyte solution were converted to bicarbonate ions during the addition of acidic cobalt sulfate solution, which consequently decreased the pH in the suspension. When the pH was lower than 8, the carbon mainly existed as bicarbonate and the cobalt carbonate started to precipitate at a high efficiency. Cobalt initially precipitated as cobalt carbonate hydroxide (Co2CO3(OH)2) at a higher pH (9–11) and converted to cobalt carbonate at a lower pH (6.5–8). The crystallite size of cobalt carbonate calculated for the different reaction conditions shows that the growth response is high at longer reactant addition time and high temperature. The morphology of the final cobalt carbonate precipitate was small single spherical crystals and their aggregates. The purity of precipitates could be increased by reducing the aggregation tendency during the precipitation.Peer reviewe

Hierarchical Ultrathin Layered GO-ZnO@CeO2 Nanohybrids for Highly Efficient Methylene Blue Dye Degradation

Highly efficient interfacial contact between components in nanohybrids is a key to achieving great photocatalytic activity in photocatalysts and degradation of organic model pollutants under visible light irradiation. Herein, we report the synthesis of nano-assembly of graphene oxide, zinc oxide and cerium oxide (GO-ZnO@CeO2) nanohybrids constructed by the hydrothermal method and subsequently annealed at 300 °C for 4 h. The unique graphene oxide sheets, which are anchored with semiconducting materials (ZnO and CeO2 nanoparticles), act with a significant role in realizing sufficient interfacial contact in the new GO-ZnO@CeO2 nanohybrids. Consequently, the nano-assembled structure of GO-ZnO@CeO2 exhibits a greater level (96.66%) of MB dye degradation activity than GO-ZnO nanostructures and CeO2 nanoparticles on their own. This is due to the thin layers of GO-ZnO@CeO2 nanohybrids with interfacial contact, suitable band-gap matching and high surface area, preferred for the improvement of photocatalytic performance. Furthermore, this work offers a facile building and cost-effective construction strategy to synthesize the GO-ZnO@CeO2 nanocatalyst for photocatalytic degradation of organic pollutants with long-term stability and higher efficiency

Nonclassical Crystallization and Core-Shell Structure Formation of Ibuprofen from Binary Solvent Solutions

| openaire: EC/H2020/842140/EU//OMECRY Funding Information: R.M. thanks the European Union for financial support for this work under the H2020-Marie Skłodowska-Curie Individual Fellowship (grant agreement No [842140]). He also thanks the Bioeconomy and RawMatters Research Infrastructures and OtaNano Nanomicroscopy Center, Aalto University, Finland, for the research facilities. Publisher Copyright: © 2022 The Authors. Published by American Chemical Society.Liquid-liquidphase separation (LLPS) or dense liquid intermediates during the crystallization of pharmaceutical molecules is common; however, their role in alternative nucleation mechanisms is less understood. Herein, we report the formation of a dense liquid intermediate followed by a core-shell structure of ibuprofen crystals via nonclassical crystallization. The Raman and SAXS results of the dense phase uncover the molecular structural ordering and its role in nucleation. In addition to the dimer formation of ibuprofen, which is commonly observed in the solution phase, methyl group vibrations in the Raman spectra show intermolecular interactions similar to those in the solid phase. The SAXS data validate the cluster size differences in the supersaturated solution and dense phase. The focused-ion beam cut image shows the attachment of nanoparticles, and we proposed a possible mechanism for the transformation from the dense phase into a core-shell structure. The unstable phase or polycrystalline core and itssubsequent dissolution from inside to outside or recrystallization by reversed crystal growth produces the core-shell structure. The LLPS intermediate followed by the core-shell structure and its dissolution enhancement unfold a new perspective of ibuprofen crystallization.Peer reviewe

Synthesis, structural, vibrational, molecular docking and nonlinear optical studies of (E)-N′-(2,3-dimethoxybenzylidene)-4-fluorobenzohydrazide

Funding Information: The authors are thankful to Indian Institute of Technology Hyderabad, India, and Periyar University, Salem, India for providing X-ray diffraction and spectral measurements. The authors are also thankful to the Deanship of Scientific Research at King Khalid University for the funding support through the Research Group Project under Grant number R.G.P.2/22/42. Funding Information: The authors are thankful to Indian Institute of Technology Hyderabad, India, and Periyar University, Salem, India for providing X-ray diffraction and spectral measurements. The authors are also thankful to the Deanship of Scientific Research at King Khalid University for the funding support through the Research Group Project under Grant number R.G.P.2/22/42. Publisher Copyright: © 2022 Elsevier B.V.Organic nonlinear optical single crystals of (E)-N′-(2,3-dimethoxybenzylidene)-4-fluorobenzohydrazide (DMB-FBH) were synthesized and grown using slow evaporation crystallization from ethanol solution. The single crystal X-ray diffraction scattering revealed that the DMB-FBH crystallised in the tetragonal crystal system with a centro symmetric space group of I 41/a. The crystallographic bond lengths and bond angles were compared with the values generated from optimized molecular geometry based on quantum chemical calculations. The functional group vibrations were identified theoretically by density functional theory with B3LYP 6–311 G (d,p) basis set using Gaussian 09 software package and their vibrations were compared with the experimental FT-IR spectra. The UV-visible and the fluorescence emission spectra of the DMB-FBH in aqueous solutions were recorded. The HOMO-LUMO energy level pictogram addressed the intramolecular charge transfer (ICT) interaction between donor and acceptor moieties and their impact onthe energy gap was determined. Different interactions such as O···H, N···H, C···C and C···H in DMB-FBH were quantified via fingerprint plots and these results were compared with that of similar structure. The detailed molecular docking simulation was carried out with M. tuberculosis protein [PDB ID:2 × 22]. The third order nonlinear optical susceptibility (χ3) of DMB-FBH was confirmed experimentally by Z-scan method and their conversion efficiency was higher than the other hydrazones derivatives. In short, this work discusses the crystal structure, identification and quantification of the molecular interactions, thermal, antimycobacterial and optical properties of new hydrazone derivative.Peer reviewe

Role of Synthesis Method on Luminescence Properties of Europium(II, III) Ions in β‑Ca₂SiO₄: Probing Local Site and Structure

The europium ion probes the symmetry disorder in the crystal structure, although the distortion due to charge compensation in the case of aliovalent dopant remains interesting, especially preparation involves low and high temperatures. This work studies the preparation of the β-Ca₂SiO₄ (from here on C₂S) particle from Pechini (C₂SP) and hydrothermal (C₂SH) methods, and its luminescence variance upon doping with Eu²⁺ and Eu³⁺ ions. The blue shift of the charge-transfer band (CTB) in the excitation spectra indicates a larger Eu³⁺–O^2– distance in Eu³⁺ doped C₂SH. The changes in vibrational frequencies due to stretching and bending vibrations in the FTIR and the Raman spectra and binding energy shift in the XPS analysis confirmed the distorted SiO₄^4– tetrahedra in C₂SH. The high hydrothermal temperature and pressure produce distortion, which leads to symmetry lowering although doping of aliovalent ion may slightly change the position of the Ca atoms. The increasing asymmetry ratio value from C₂SP to C₂SH clearly indicates that the europium ion stabilized in a more distorted geometry. It is also supported by Judd–Ofelt analysis. The concentration quenching and site-occupancy of Eu³⁺ ions in two nonequivalent sites of C₂S were discussed. The charge state and concentration of europium ions in C₂SP and C₂SH were determined using X-ray photoelectron spectroscopy measurements. The C₂S particles were studied by X-ray powder diffraction, FTIR, Raman, BET surface area, TGA/DTA, electron microscopy, XPS, and luminescence spectroscopy. The impact of citrate ion on the morphology and particle size of C₂SH has been hypothesized on the basis of the microscopy images. This study provides insights that are needed for further understanding the structure of C₂S and thereby improves the applications in optical and biomedical areas and cement hydration

Fluorescence Properties Reinforced by Proton Transfer in the Salt 2,6-Diaminopyridinium Dihydrogen Phosphate

Luminescent materials have many interesting applications, but it remains difficult to control the luminescence of organic materials and in particular to retain the same luminescence in solution and in the solid state, a property of interest for various imaging applications. In the present work, the fluorescent properties of the salt of 2,6-diaminopyridinium with dihydrogen phosphate have been explored. As a result of proton transfer from phosphoric acid to the pyridine nitrogen and the stabilizing effect of the two primary amines at the positions ortho to the pyridine nitrogen, the band gap between the HOMO and the LUMO is considerably diminished in comparison with that in 2,6-diaminopyridine. This is confirmed by a red shift in its absorption spectrum. Because protonation is retained in aqueous solution, the dissolved 2,6-diaminopyridinium dihydrogen phosphate salt retains a similar fluorescent spectrum as in the solid state. The crystals have been studied by single-crystal X-ray diffraction; FTIR, Raman, UV–vis–NIR, and luminescence spectroscopy; HOMO–LUMO calculations using DFT; and thermal analysis. The compound provides an example of a supramolecular motif that controls the crystal structure and the luminescence properties. In addition, the crystal exhibits negligible thermal expansion over a temperature interval of 150 °C. In short, 2,6-diaminopyridinium dihydrogen phosphate is an interesting compound for the design of luminescent devices