ZnO-Salen NPs Employed as Chemosensor for Detection of Al3+ and K+ in Aqueous Medium, Developing Human Cell Images.

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 ß2(Al3+) = 6.61 × 103 and ß2(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.

Simultaneous recognition of cysteine and cytosine using thiophene-based organic nanoparticles decorated with Au NPs and bio-imaging of cells.

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.

Insight mechanism of magnetic activated catalyst derived from recycled steel residue for black liquor degradation.

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.

Reductive Oligomerization of Nitroaniline Catalyzed by Fe3O4 Spheres Decorated with Group 11 Metal Nanoparticles.

The present work demonstrates a simple and sustainable method for forming azo oligomers from low-value compounds such as nitroaniline. The reductive oligomerization of 4-nitroaniline was achieved via azo bonding using nanometric Fe3O4 spheres doped with metallic nanoparticles (Cu NPs, Ag NPs, and Au NPs), which were characterized by different analytical methods. The magnetic saturation (M s) of the samples showed that they are magnetically recoverable from aqueous environments. The effective reduction of nitroaniline followed pseudo-first-order kinetics, reaching a maximum conversion of about 97%. Fe3O4-Au is the best catalyst, its a reaction rate (k Fe3O4-Au = 0.416 mM L-1 min-1) is about 20 times higher than that of bare Fe3O4 (k Fe3O4 = 0.018 mM L-1 min-1). The formation of the two main products was determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS), evidencing the effective oligomerization of NA through N = N azo linkage. It is consistent with the total carbon balance and the structural analysis by density functional theory (DFT)-based total energy. The first product, a six-unit azo oligomer, was formed at the beginning of the reaction through a shorter, two-unit molecule. The nitroaniline reduction is controllable and thermodynamically viable, as shown in the computational studies.

Enhancement of the CO2 Sensing/Capture through High Cationic Charge in M-ZrO2 (Li+, Mg2+, or Co3+): Experimental and Theoretical Studies.

The capture and storage of CO2 are of growing interest in atmospheric science since greenhouse gas emission has to be reduced considerably in the near future. The present paper deals with the doping of cations on ZrO2, i.e., M-ZrO2 (M = Li+, Mg2+, or Co3+), defecting the crystalline planes for the adsorption of carbon dioxide. The samples were prepared by the sol-gel method and characterized completely by different analytical methods. The deposition of metal ions on ZrO2 (whose crystalline phases: monoclinic and tetragonal are transformed into a single-phase such as tetragonal for LiZrO2 and cubic for MgZrO2 or CoZrO2) shows a complete disappearance of the XRD monoclinic signal, and it is consistent with HRTEM lattice fringes: 2.957 nm for ZrO2 (101, tetragonal/monoclinic), 3.018 nm for tetragonal LiZrO2, 2.940 nm for cubic MgZrO2, and 1.526 nm for cubic CoZrO2. The samples are thermally stable, resulting an average size of ∼5.0-15 nm. The surface of LiZrO2 creates the oxygen deficiency, while for Mg2+ (0.089 nm), since the size of the atom is relatively greater than that of Zr4+ (0.084 nm), the replacement of Zr4+ by Mg2+ in sublattice is difficult; thus, a decrease of the lattice constant was noticed. Since the high band gap energy (ΔE > 5.0 eV) is suitable for CO2 adsorption, the samples were employed for the selective detection/capture of CO2 by using electrochemical impedance spectroscopy (EIS) and direct current resistance (DCR), showing that CoZrO2 is capable of CO2 capture about 75%. If M+ ions are deposited within the ZrO2 matrix, then the charge imbalance allows CO2 to interact with the oxygen species to form CO32- which produces a high resistance (21.04 × 106 (Ω, Ohm)). The adsorption of CO2 with the samples was also theoretically studied showing that the interaction of CO2 with MgZrO2 and CoZrO2 is more feasible than with LiZrO2, subscribing to the experimental data. The temperature effect (273 to 573 K) for the interaction of CO2 with CoZrO2 was also studied by the docking method and observed the cubic structure is more stable at high temperatures as compared to the monoclinic geometry. Thus, CO2 would preferably interact with ZrO2c (ERS = -19.29 kJ/mol) than for ZrO2m (22.4 J/mmol (ZrO2c = cubic; ZrO2m = monoclinic).

Influence of PFDA on the nutrient removal from wastewater by hydrogels containing microalgae-bacteria.

PFAS have demonstrated to affect some aerobic microorganisms applied for wastewater treatment. This study evaluated the nutrient removal of three types of hydrogels containing a consortium of microalgae-bacteria (HB), activated carbon (HC), or both (HBC) in presence of perfluorodecanoic acid (PFDA). The nutrients evaluated were ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), phosphate (PO4), and chemical oxygen demand (COD). Fluorine (F-) concentration and the integrity of HB exposed to PFDA were also determined at the end of experiments to understand the potential sorption and effects of PFDA on hydrogel. The results indicated that the presence of PFDA did affect the nitrification process, 13% and 36% to HB and HBC, respectively. Mass balance confirmed negative impact of PFDA on nitrogen consumption in HB (-31.37%). However, NH4-N was removed by all types of hydrogels in a range of 61-79%, while PO4 was mainly removed by hydrogels containing activated carbon (AC), 37.5% and 29.2% for HC and HBC, respectively. The removal of both NH4 and PO4, was mainly attributed to sorption processes in hydrogels, which was enhanced by the presence of AC. PFDA was also adsorbed in hydrogels, decreasing its concentration between 18% and 28% from wastewater, and up to 39% using HC. Regarding COD concentration, this increased overtime but was not related to hydrogel structure, since Transmission Electron Microscopy imaging revealed that their structure was preserved in presence of PFDA. COD increasement could be attributed to soluble algal products as well as to PVA leaching from hydrogels. In general, the presence of AC in hydrogels can contribute to mitigate the toxic effect of PFDA over microorganisms involved in biological nutrient removal, and hydrogels can be a technique to partially remove this contaminant from aqueous matrices.

Crystal Plane Impact of ZnFe2O4-Ag Nanoparticles Influencing Photocatalytical and Antibacterial Properties: Experimental and Theoretical Studies.

This paper describes the crystal interphase impact of ZnFe2O4-Ag in the photodegradation of Rhodamine B. Prepared ZnFe2O4 nanoparticles (NPs) were deposited with Ag NPs to offer ZnFe2O4-Ag (0-2.5%). An X-ray diffraction peak corresponding to the Ag NPs was detected if the particle content reached about 2.0%, observing multiple crystalline interphases in HR-TEM. Magnetic saturation (Ms) was increased ∼160% times for ZnFe2O4-Ag (7.25 to 18.71 emu/g) and ZnFe2O4 (9.62 to 25.09 emu/g) if the temperature is lowered from 298 to 5.0 K; while for Fe3O4 (91.09 to 96.19 emu/g), the Ms increment was just about 5.6%. After analyzing the DFT-Density of State, a decrease of bandgap energy for ZnFe2O4-Ag6 from the influence of the size of Ag cluster was seen. Quantum yield (Φ) was 0.60 for ZnFe2O4, 0.25 for ZnFe2O4-Ag (1.0%), 0.70 for ZnFe2O4-Ag (1.5%), 0.66 for ZnFe2O4-Ag (2.0%), and 0.66 for ZnFe2O4-Ag (2.5%), showing that the disposition of Ag NPs (1.5-2.5%) increases the Φ to >0.60. The samples were used to photo-oxidize RhB under visible light assisted by photopowered Langmuir adsorption. The degradation follows first-order kinetics (k = 5.5 × 10-3 min-1), resulting in a greater k = 2.0 × 10-3 min-1 for ZnFe2O4-Ag than for ZnFe2O4 (or Fe3O4, k = 1.1 × 10-3 min-1). DFT-total energy was used to analyze the intermediates formed from the RhB oxidation. Finally, the ZnFe2O4-Ag exhibits good antibacterial behavior because of the presence of Zn and the Ag components.

Effect of the structural integrity on the size and porosity of gold-implanted mixed-metal oxide nanocomposites: their influence on the photocatalytic degradation of thioanisole.

Since the interfacial binding strength and structural integrity have a strong influence on the active sites of nanocomposites, this study focused on exploring the structural and electronic properties at the interface between the implanted metal ion and host support. For this, nanocomposites of gold embedded in CeO2-ZrO2 and CeO2-Al2O3 matrices were fabricated, and their structural and morphological properties were investigated using ICP-OES, UV-vis, XRD, Raman, HRTEM, and high-resolution XPS studies and compared. From the results, it was found that the deposition of gold is highly favored over CeO2-ZrO2 (3.99 atomic %) than CeO2-Al2O3 (1.21 atomic %); however, the same amount of gold was used for the synthesis of both nanocomposites, as befits it. The HRTEM images of Au/CeO2-ZrO2 displayed well-organized yarn textured particles with less than 5 nm size, which lacks in Au/CeO2-Al2O3. The reason for this less systematized and less Au embedding in the presence of alumina in CeO2-Al2O3 was verified with the high-resolution XPS studies of both nanocomposites and an elevated binding energy due to the mobility of Au particles over CeO2-Al2O3 was observed, while for Au/CeO2-ZrO2, a very small binding energy shift of gold states (Au 4f5/2 0.39; Au 4f7/2 0.17 eV) and the CeO2-ZrO2 matrix that favored an increased intermolecular force between gold and the supporting host was observed. This agrees well with UV-vis electronic spectrum analysis, which revealed that the incorporation of gold nanoparticles narrowed the band gap more significantly in Au/CeO2-ZrO2 (4.2 eV) than Au/CeO2-Al2O3 (4.94 eV) suggesting the elevated electron transfer from the conduction band of CeO2-ZrO2 to Au interfaces. In addition, XRD and Raman studies of Au/CeO2-ZrO2 showed a pronounced phase transformation of Ce4+ to Ce3+ in the presence of homovalent Zr4+ ions with an increased structural disorder in CeO2 promoting the localized surface plasmon resonance (LSPR) in the lattice of CeO2-ZrO2, which was less detected in Au/CeO2-Al2O3 due to the interference of less-desired γ-Al2O3 phases. These characteristics of Au/CeO2-ZrO2 ensured its performance as a promised photocatalyst for thioanisole degradation without using any harmful oxidants, and its stability towards different irradiation conditions, such as visible, ultraviolet, and solar light.

Effect of relative humidity on hydrogen peroxide production in water droplets.

Mist is generated by ultrasonic cavitation of water (Fisher Biograde, pH 5.5-6.5) at room temperature (20-25 °C) in open air with nearly constant temperature (22-25 °C) but varying relative humidity (RH; 24-52%) over the course of many months. Water droplets in the mist are initially about 7 µm in diameter at about 50% RH. They are collected, and the concentration of hydrogen peroxide (H2O2) is measured using commercial peroxide test strips and by bromothymol blue oxidation. The quantification method is based on the Fenton chemistry of dye degradation to determine the oxidation capacity of water samples that have been treated by ultrasonication. It is found that the hydrogen peroxide concentration varies nearly linearly with RH over the range studied, reaching a low of 2 parts per million (ppm) at 24% RH and a high of 6 ppm at 52% RH. Some possible public health implications concerning the transmission of respiratory viral infections are suggested for this threefold change in H2O2 concentration with RH.

Erratum: Effect of Relative Humidity on Hydrogen Peroxide Production in Water Droplets - CORRIGENDUM.

[This corrects the article DOI: 10.1017/qrd.2021.6.].

Visible light driven photo-degradation of Congo red by TiO2ZnO/Ag: DFT approach on synergetic effect on band gap energy.

In this paper, we report the combination of two metal oxides (TiO2ZnO) that allows mixed density of states to reduce band gap energy, facilitating the photo-oxidation of Congo red dye under visible light. For the oxidation, a possible mechanism is proposed after analyzing the intermediates by GC-MS, and it is consistent with Density Functional Theory (DFT). The nanohybrids were characterized comprehensibly by several analytical techniques such as X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS). For the addition of ZnO to TiO2, a dominance of anatase phase was found rather than other phases (rutile or brookite). A broad band (∼550 nm) is observed in UV-Visible spectra for TiO2ZnO/Ag NPs nm because of Surface Plasmon properties of Ag NPs. The band gap energy was calculated for TiO2ZnO/Ag system, and then it has been further studied by DFT in order to show why the convergence of two semiconductors allows a mixed density of states, facilitating the reduction of the energy gap between occupied and unoccupied bands; ultimately, it improves the performance of catalysts under visible light. Significantly, the interaction of crystal planes (0 0 I) of TiO2 anatase and (0 0 1) of ZnO crucially plays as an important role for the reduction of energy band-gap. Additionally, TiO2ZnOAg NPs were used recognize Saccharomyces cerevisiae cells by con-focal fluorescence microscope, showing that it develops bright bio-images for the cells; while for TiO2 or ZnO or TiO2ZnO NPs, no fluorescent response was seen within the cells.

Nanomolar Detection of Iodide in Aqueous Medium Using Organic-Inorganic Hybrid Nanoparticles: Application in Urine Analysis.

Imine-linked pyridine-coupled (ILPC) receptors have been synthesised and characterised. The absorption and fluorescence properties of these receptors have been explored through a combination of experimental and theoretical studies. The ILPC receptors are processed into organic nanoparticles (ONPs) and then decorated with gold nanoparticles (AuNPs) for the selective recognition of iodide. The selective recognition behaviour is authenticated with the changes in fluorescence spectra, low detection limit (1.4 nM) and no interference in aqueous systems. The present investigation represents the first example of nanomolar detection of iodide in aqueous medium using organic-inorganic hybrid nanoparticles (ONPs-AuNPs). The probe has been utilised successfully for the detection of iodide content in urine samples.