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The present work deals with developing a method for revalorizing steel residues to create sunlight-active photocatalysts based on iron oxides. Commercial-grade steel leftovers are oxidized under different combinations of pH and temperature (50–90 °C and 3 ≥ pH ≤ 5) in a low energy-intensive setup. The material with the highest production efficiency (yield > 12%) and magnetic susceptibility (χm = 387 × 10−6 m3/kg) was further explored and modified by diffusion of M2+ (Zn and Co) ions within the structure of the oxide using a hydrothermal method to create ZnFe2O4, CoFe2O4 and combined Co–Zn ferrite. (Co–Zn)Fe2O4 displayed a bandgap of 2.02 eV and can be activated under sunlight irradiation. Electron microscopy studies show that (Co–Zn)Fe2O4 consists of particles with diameters between 400 and 700 nm, homogeneous size, even distribution, and good dispersibility. Application of the developed materials in the sunlight catalysis of black liquors from cellulose extraction resulted in a reduction of the Chemical Oxygen Demand (− 15% on average) and an enhancement in biodegradability (> 0.57 BOD/COD) after 180 min of reaction. Since the presented process employs direct solar light, it opens the possibility to large-scale water treatment and chemical upgrading applications. [ABSTRACT FROM AUTHOR]

The present work highlights the sustainable approach for the transformation of plastic waste into fluorescent carbon dots (CDs) through carbonization and then they were functionalized with L-cysteine and o-phenylenediamine. CDs which were characterized by different analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), and transmission electron microscopy (TEM) are employed to recognize Cu2+, Fe2+, and Hg2+ ions. The results show that the fluorescence emission was considerably quenched, and it is consistent with the interference and Jobs plots. The detection limit was found to be 0.35µM for Cu(II), 1.38 µM for Hg(II), and 0.51µM Fe(III). The interaction of CDs with metal ions enhances the fluorescence intensity detecting histamine successfully. It shows that plastic waste-based CDs can be applied clinically to detect toxic metals and biomolecules. Moreover, the system was employed to develop the cellular images using Saccharomyces cerevisiae cells with the support of a confocal microscope. Furthermore, theoretical studies were performed for the naphthalene layer (AR) as a model for C-dots, then optimized its structure and analyzed by using the molecular orbital. The obtained TD-DFT spectra coincided with experimental spectra for CDs/M2+/histamine systems. [ABSTRACT FROM AUTHOR]

Discovery of new photocatalytic materials that can efficiently degrade organic contaminants is of great interest. In the present work, TiO2 was spatially dispersed over two siliceous mesoporous supports, SBA-15, representing an example of a material with periodic and ordered array of pores and SiO2-aerogel-10, as an example of an aperiodic material with random network of hierarchical pores. The resulting materials, TiO2-SBA-15-10 and TiO2-SiO2-aerogel-10, were characterized comprehensively by several analytical methods and their photocatalytic performance was evaluated by examining the oxidation of rhodamine B dye under visible light irradiation. The adsorption of rhodamine B was enhanced in TiO2-SBA-15-10 in comparison to TiO2-SiO2-aerogel-10. In diffuse reflection spectra (DRS), the presence of Ti4+ in tetrahedral geometry was observed to be higher for TiO2-SBA-15-10 sample. Thus, in the photocatalytic degradation study, a significant enhancement in the oxidation of rhodamine B dye was observed for TiO2-SBA-15-10 in comparison to TiO2-SiO2-aerogel-10. The formation of oxidation intermediates was analyzed by electrospray ionization-mass spectrometry (ESI-MS) indicating degradation of rhodamine B. This study illustrates the importance of the coordination of the Ti4+ in enhancing photocatalytic degradation of model dye pollutants such as rhodamine B. [ABSTRACT FROM AUTHOR]

Biomolecules like cysteine and cytosine play a significant role in many physiological processes, and their unusual level in biological systems can lead to many diseases including cancer. Indeed, the need for selective detection of these moieties by a fluorescence probe is imperative. Thus, thiophene based Schiff N,N′-bis(thiophene-2-ylmethylene)thiophenemethane (BMTM) was synthesized and then characterized using several analytical techniques before converting it into organic nanoparticles (ONPs). Then, fluorescent organic inorganic nanohybrids (FONs) were obtained after decorating ONPs with AuNPs to yield BMTM-Au-ONPs (FONPs). The morphology of the particles, analyzed using a Transmission Electron Microscope (TEM), shows that AuNPs were embedded with low density organic matter (ONPs). FONPs were employed to recognize cysteine and cytosine simultaneously. No interference was observed from other moieties such as guanine, uracyl, NADH, NAD, ATP, and adenine during the detection. It means that the intensity of the fluorescence signal was significantly changed (enhanced for cytosine and quenched for cysteine). So, FONPs were used to detect cysteine and cytosine in real samples, like Saccharomyces cerevisiae cells. As expected, no considerable fluorescence signal for cysteine was observed, while for cytosine, strong fluorescence signals were detected in the cells. DFT was used to explain the interaction of FONPs with cysteine or cytosine. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of a series of 25 phosphonate derivatives were analyzed applying density functional theory, with the exchange-correlation functional PBEPBE in combination with the 6-311++G** basis set for all atoms. The chemical reactivity of these derivatives has been interpreted using quantum descriptors such as frontier molecular orbitals (HOMO, LUMO), Hirshfeld charges, molecular electrostatic potential, and the dual descriptor [Δf(r)]. These descriptors are directly related to experimental median lethal dose (LD50), expressed as its decimal logarithm [Aobs=log10(LD50)] through a multiple linear regression equation. The proposed model predicts the toxicity of phosphonates in function of the volume (V), the load of the most electronegative atom of the molecule (q), and the eigenvalue of the molecular orbital HOMO (EHOMO). The obtained values in the internal validation of the model are: R2=82.71%, RADJ2=80.24%, F=33.5, δK=0.169, δQ=0.011, RP=0.423, RN=-0.025(-0.311), and Qboot2=75.45%. The toxicity of nine phosphonate derivatives used as test molecules was adequately predicted by the model. The theoretical results indicate that the oxygen atom of the O=P group plays an important role in the interaction mechanism between the phosphonate and the acetylcholinesterase enzyme, inhibiting the removal of the proton of the ser-200 residue by the his-440 residue. [ABSTRACT FROM AUTHOR]

New CdS NPs decorated with 2-thiobenzimidazole (TB) were synthesized as chemo-sensors for selective recognition of potassium ions. The results show that CdS-TB NPs are sensitive and selectively detect K ions, finding that there is no interference from other metal ions (Mn, Mg, Cu, Co, Cr, Fe, Ni, Zn, Sr, Ag, Sm, Al, Cd, Ba, Na), and the detection limit was as low as 0.008 mM. In antibacterial studies, CdS-TB NPs exhibit non-toxicity towards bacterial systems, suggesting that the decoration of TB molecules reduces the toxicity of CdS NPs. In order to understand the binding nature of TB molecules with CdS, the structural and electronic properties of different CdS clusters [(CdS), n = 1-16] were analyzed by Density Functional Theory (DFT) before and after their interaction with TB, and the molecular orbitals and density of states were used to describe the nature of the bonding between metal oxide clusters and TB molecules. Graphical Abstract: [ABSTRACT FROM AUTHOR]

ZnO nanoparticles (NPs) were prepared and characterized by different analytical methods and then they were used to decorate with N, N´-bis(salicylidene)ethylenediamine (salen) in order to perform as receptor for the metal ions in an aqueous medium. The results show that ZnO-salen selectively detects Al3+ ions in aqueous medium since the intensity of fluorescence has been enhanced significantly. However, the presence of K+ in the medium further intensified the fluorescence emission for the [ZnO-salen-Al3+] system. The above system has been applied to recognize Al3+ and K+ in cells by developing the cell images, for which, the fluorescence image is brightened if a human glioblastoma U251 cell contains [ZnO-salen-Al3+] + K+ ions, consisting of the fluorescence titration. The binding global constant for Al3+ and the subsequent recognition of K+ by ZnO-salen resulted in β2(Al3+) = 6.61 × 103 and β2(K+) = 3.71 × 103 with a detection limit of 36.51 µM for Al3+ and 17.39 µM for K+. In the cell toxicity analysis, the cell viability was over 85% for the ZnO-salen even in the concentration as high as 100 mM. [ABSTRACT FROM AUTHOR]