Volume 39, Issue 6, December 2023, Page 539-556
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Heavy metals in soil of three agroforestry systems: a preliminary study for source identification and ecological risk
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Fabrication and application of novel magnetic polyethylene oxide/ polyacrylamide /graphitic carbon nitride nanocomposite by gamma irradiation for metal ion removal from waste water
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A Calcination‐Free Sol‐Gel Method to Prepare TiO2‐Based Hybrid Semiconductors for Enhanced Visible Light‐Driven Hydrogen Production
The extensive π system in the naphthalene structure and the carboxylic acid group of 1,4-naphthalene dicarboxylic acid (NA) render it an exceptional organic semiconductor for doping TiO2 using a calcination-free sol-gel method. The resulting catalyst exhibited a significantly improved hydrogen production rate by photolyzing water molecules under visible light, outperforming the efficiency of the calcined material.
Abstract
In recent years, the sol-gel method has been extensively utilized to develop efficient and stable organic semiconductor composite titanium dioxide (TiO2) photocatalysts. However, the high-temperature calcination requirements of this method consume energy during preparation and degrade encapsulated organic semiconductor molecules, resulting in decreased photocatalytic hydrogen production efficiency. In this study, we found that by selecting an appropriate organic semiconductor molecule, 1,4-naphthalene dicarboxylic acid (NA), high-temperature calcination can be avoided in the sol-gel process, yielding an organic-inorganic hybrid material with stable and effective photocatalytic properties. The uncalcined material displayed a hydrogen production rate of 2920±15 μmol g−1 h−1, which was approximately twice the maximum production rate observed in the calcined material. Likewise, the specific surface area of the uncalcined material, at 252.84 m2 g−1, was significantly larger compared to the calcined material. Comprehensive analyses confirmed successful NA and TiO2 doping, while UV-vis and Mott-Schottky tests revealed a reduced energy bandgap (2.1 eV) and expanded light absorption range. Furthermore, the material maintained robust photocatalytic activity after a 40-hour cycle test. Our findings demonstrate that by using NA doping without calcination, excellent hydrogen production performance can be achieved, offering a novel approach for environmentally friendly and energy-saving production of organic semiconductor composite TiO2 materials.
On energetics of proton and electron transfer of selected phenol derivatives: Theoretical investigation of radical and oxonium cations
Theoretical study of phenols in forms of cation radicals and oxonium cations. The proton-coupled electron transfer and redox properties are studied. The pKa values scaled on the experimental data are obtained. Pourbaix diagrams for water are constructed.
Abstract
In this paper, the systematic theoretical study of phenol and 36 compounds representing various ortho, meta and para-substituted (R-PhOH) phenols is presented. The hydroxyl group acidity is a characteristic feature of phenol which can be modified using substitution of phenyl ring. The proton-coupled electron transfer was investigated for parent neutral phenols, R-PhOH, their cation radicals, R-PhOH+•, and oxonium cations, R-PhOH2 +. Density functional theory calculations were combined with solvent continuum model for water and dimethyl sulfoxide environment. For aqueous solution, the Pourbaix diagrams (electrochemical potential vs. pH) were constructed from the theoretically predicted acidity constants and electrochemical standard potentials. From the thermodynamic point of view, the obtained theoretical results allow the estimation of the thermodynamically preferred process and alternative reaction pathways of phenolic derivatives in very acidic media.
Recent Progress in Screening of Mycotoxins in Foods and Other Commodities Using MXenes-Based Nanomaterials
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Inorganic and Organometallic Polymers as Energy Storage Materials and Enhancing Their Efficiency
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Chromatographic Methods for Detection and Quantification of Pyrrolizidine Alkaloids in Flora, Herbal Medicines, and Food: An Overview
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Investigation of Carbonate Substitution in Hydroxyapatite by Combining Solid‐state NMR and DFT Calculations
A systematic study of all substitutions in biological apatite has been investigated and discussed using NMR and DFT calculations. The lowest energy is found for system containing grouped associations of four carbonate groups, substituting four consecutive phosphates, organized in zigzag fashion which confirms the tendency to carbonate clustering. The multiple-B substitutions, mono B-substitutions and A type substitution were also compared. With this set of models, 1 H, 13 C and 31 P chemical shifts observed experimentally in the synthetic CHAp sample were fairly well reproduced.
Abstract
Biological apatites (main constituent of natural bones) correspond to non-stoichiometric hydroxyapatite HAp, presenting a large variety of ions as substituents (CO3 2−, F−, SiO4 4−, Mg2+, Na+…). The precise location and configuration of ionic substitutes in the HAp matrix are generally difficult to identify and characterize. This contribution details the structural characterization based on NMR data of a particular case of hydroxyapatite substitution by carbonates. For this purpose, all substitution mechanisms proposed to our knowledge in the literature are modeled by DFT and the corresponding calculated NMR parameters allowed to propose or confirm some interpretations of a certain number of experimental observations to rationalize the dependencies of the 13C chemical shift and energy on these structural parameters. The presented results open the way for a fast interpretation of 13C NMR experiments on defective HAp materials and will allow to predict the most stable arrangement of CO3 2− for a given family of defects.
Design, Characterization and Evaluation of a Lab‐made Photoreactor: A First Step Towards Standardized Procedures in Photocatalysis
A lab-made 3D printed photochemistry reactor is presented. Positions hosting reaction vials were characterized by means of chemical actinometry and it is shown that a proper designing of the reactor allows several experiments to run simultaneously as they receive the same amount of light. The reactor was tested against two procedures described in the literature and has revealed efficient for the multiple reproduction of reactions.
Abstract
For the last fifteen years, photochemistry has known a renewal with the emergence of new photoredox approaches, along with the development of new powerful artificial sources of light. However, the described procedures often lack information about the characteristics of the setups (wavelength, actual received light power, distance from the source) even when commercial apparatuses are used. This lacunar information hampers the development of standardized procedures which would guarantee the reproducibility of the reactions. With the objective of furnishing a standardized setup, a lab-made reactor was designed. The use of 3D-printing technology makes it easily accessible to most laboratories. Its characterization showed the critical effect of the environmental conditions upon the light power received and how crucial they are for reproducibility of photochemical reactions. At last, the setup was evaluated against experiments taken from recent literature.