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The electronic and catalytic properties of two-dimensional MoS2, WS2, and NbS2 quantum dots are investigated using density functional theory investigations. The stability of the considered structures is confirmed by the positive binding energies and the real vibrational frequencies in the infrared spectra. The ab initio molecular dynamics simulations show that these nanodots are thermally stable at 300 K with negligible changes in the potential energy and metal–S bonds. The pristine nanodots are semiconductors with energy gaps ranging from 2.6 to 3 eV. Edge sulfuration significantly decreases the energy gap of MoS2 and WS2 to 1.85 and 0.75 eV, respectively. The decrease is a result of the evolution of low-energy molecular orbitals by the passivating S-atoms. The energy gap of NbS2 is not affected, which could be due to the spin doublet state. Molecular electrostatic potentials reveal that the edge sulfur/transition metal atoms are electrophilic/nucleophilic sites, while the surface atoms are almost neutral sites. MoS2 quantum dots show an interestingly low change in the hydrogen adsorption free energy ~0.007 eV, which makes them competitive for hydrogen evolution catalysts.

Novel cyano-benzylidene xanthene derivatives were synthesized using one-pot and condensation reactions. A diprotic Brønsted acid (i.e., oxalic acid) was used as an effective catalyst for the promotion of the synthesis process of the new starting xanthene–aldehyde compound. Different xanthene concentrations (ca. 0.1–2.0 mM) were applied as corrosion inhibitors to control the alkaline uniform corrosion of aluminum. Measurements were conducted in 1.0 M NaOH solution using Tafel extrapolation and linear polarization resistance (LPR) methods. The investigated xanthenes acted as mixed-type inhibitors that primarily affect the anodic process. Their inhibition efficiency values were enhanced with inhibitor concentration, and varied according to their chemical structures. At a concentration of 2.0 mM, the best-performing studied xanthene derivative recorded maximum inhibition efficiency values of 98.9% (calculated via the Tafel extrapolation method) and 98.4% (estimated via the LPR method). Scanning electron microscopy (SEM) was used to examine the morphology of the corroded and inhibited aluminum surfaces, revealing strong inhibitory action of each studied compound. High-resolution X-ray photoelectron spectroscopy (XPS) profiles validated the inhibitor compounds’ adsorption on the Al surface. Density functional theory (DFT) and Monte Carlo simulations were applied to investigate the distinction of the anticorrosive behavior among the studied xanthenes toward the Al (111) surface. The non-planarity of xanthenes and the presence of the nitrile group were the key players in the adsorption process. A match between the experimental and theoretical findings was evidenced.

Air particulate matter with a diameter of 2.5 µm (PM2.5) were assembled for a whole year from the historical Jeddah district. Additional PM2.5 aerosols were collected during the autumn and winter seasons from another newly constructed district in Jeddah city (Alnaeem). The annual concentration of the total mass of the PM2.5 aerosols from the historical Jeddah site was found to be 43 ± 6 µg/m3. In addition, the average of the total mass concentration at the Alnaeem site was 61 ± 14 µg/m3. These values were greater than the annual mass concentration of the air quality standards of the European Commission (25 µg/m3) and the World Health Organization (10 µg/m3). The elemental analysis of the collected fine atmospheric aerosols was achieved by energy dispersive X-ray fluorescence (EDXRF) with three secondary targets (CaF2, Ge, and Mo). Quantitative elemental analyses of twenty-two (22) elements were achieved starting from the low atomic number element (Na) up to the high atomic number element (Pb). Although the historical Jeddah site is not well organized, the elemental concentrations and total mass concentrations were lower than those of the other site. The statistical analyses including enrichment factors, correlation analysis, and the principal component analysis revealed more information about the source identification of the PM2.5 aerosols collected from both locations. It was recognized that the elements Al, Si, K, Ca, Ti, Mn, Fe, Rb, and Sr originated from a natural source. On the other hand, the elements Ta, Br, Pb, Sc, Ni, Cu, Zn, and S originated from anthropogenic sources. Finally, the elements Na, Cl, and Br came mainly from the sea spray source.

Solid solutions from ( 1 - x ) ZnMn 2 O 4 / ( x ) MgFe 2 O 4 ( x  = 0.0, 0.1, 0.5, 0.9, 1.0) were obtained by a simple sol–gel procedure. A single-phase tetragonal spinel zinc manganite was identified by X-ray phase analysis for the samples x  = 0.0 and 0.1, whereas a single-phase cubic spinel magnesium ferrite was identified for x  = 0.5, 0.9, and 1.0. The formation of these phases was confirmed by the analysis of FTIR absorption spectra measured for the obtained samples. A scanning electron microscope was used to identify the different elements in the formed solid solution. Transmission electron microscope together with Rietveld profile method emphasized the nano-nature of the obtained samples. The influence of the composition parameter ( x ) on the optical properties of the solid solutions was explored utilizing UV–Vis diffuse reflectance spectroscopy measurements. The magnetic measurements revealed the conversion of the paramagnetic nature of ZnMn 2 O 4 samples into ferromagnetic nature as it couples with MgFe 2 O 4 sample in ( 1 - x ) ZnMn 2 O 4 / ( x ) MgFe 2 O 4 solid solution. The supercapacitor performance of all samples was examined by cyclic voltammetry and galvanostatic charge–discharge studies.

Chitosan is embedded by different ratios of Au/Ag NPs. Au/Ag NPs have been synthesised by laser ablation. The electrical conductivity and antibacterial behaviour of the synthesized films were obtained. In x-ray diffraction (XRD), a new pattern appeared at 2θ = 38.3° and 44.0° which correspond to face-centered cubic Ag, and a new pattern appeared at 38.5°, 45.0°, and 66.1° which corresponds to face-centered cubic Au. Fourier transform infrared (FTIR) data confirmed the interaction and miscibility between chitosan chains and Ag/Au NPs. Chitosan embedded with a 2/3 ratio of Au/Ag NPs reacted properly. Ultraviolet-visible (UV-Vis) spectroscopy results show a peak at 410 nm, corresponding to Ag NPs, and a very weak peak at 528 nm, corresponding to Au NPs, which shows evidence of the complexation between chitosan and Au/Ag NPs. The values of the ε' and loss ε̎ were increased after being embedded by pure Ag NPs until they reached a high value for sample S3 (2/3) (Au/Ag), then began to decrease by increasing the content of Au NPs and decreasing the ratio of Ag NPs. By decreasing the concentration of Ag NPs from S1 (0/5) to S6 (5/0) in the ration of Au/Ag NPs, there are decreases in the inhibition zone for both of the gram-negative bacterial strains tested, and the two gram-positive strains, using the zone of inhibition. The obtained results suggest that chitosan embedded with 2/3 Au/Ag possesses possible antibacterial action against the given bacteria. The given results suggest that the 2/3 Au/Ag-doped chitosan is the proper ratio used for both electrical and biomedical applications.

In this study, the role of iron sulfide (FeS) content on the structural and optical properties of graphene/polyvinyl alcohol (Gr/PVA) blend has been examined for environmental-friendly applications. Gr/PVA blend filled with FeS (0 to 10 wt%) were equipped using the casting technique. The prepared samples were studied via a scanning electron microscope, X-ray diffractometer, FT-IR and UV–visible-NIR spectrophotometers. XRD analysis shows that the crystallinity increases with increasing FeS concentration in the host Gr/PVA blend. UV–visible-NIR analysis shows that the direct optical bandgap of composite blends shrinks from 5.37 to 4.68 eV as FeS content is increased to 10 wt%. Also, it confirms that the refractive index and optical conductivity of Gr/PVA blend could be significantly enhanced via FeS filling. FeS filled Gr/PVA blends are recommended eco-friendly applications.

The laser ablation process has been utilized to manufacture the selenium nanoparticles (Se NPs). PEO/Cs (70% PEO/30% Cs) scattered by Se NPs at various ablation time. XRD analysis reveals reducing in crystallinity fabricated films. The size of the fabricated selenium nanoparticles is 34 nm. The physical properties (optical and electrical) of the produced films have been performed via various methods. The UV–Vis spectra are used to examine the optical properties of the polymer nanocomposites (PEO/Cs/Se NPs). The value of direct transition energy gap reduced from 5.35 to 4.96 by raising the content of selenium nanoparticles in the blend. In addition, the value of indirect energy gap reduced from 4.81 to 3.92 eV by raising the content of selenium nanoparticles in the blend. Electrical conductivity results revealed that raising the selenium nanoparticles concentration in PEO/Cs improved the dielectric performance of the PEO/Cs/Se NPs films. In the presence of a dielectric, the electrical relaxation dynamics were examined.

Air pollution causes environmental and health problems around the world. In this study, ambient particulate matter with an aerodynamic diameter equal to or less than 10 microns (PM10) has been collected at three different locations in Jeddah city, Saudi Arabia. The locations are characterized by differences in terms of traffic, residential intensity, industrial, and non-road mobile machinery activities. The monthly and annual mass concentration of the PM10 exceeds the recommended annual limit of the World Health Organization (15 µg/m3) and the European air quality standard (40 µg/m3) at the three locations. The collected PM10 samples as well as a certified reference material of atmospheric particulates (NIST 1678a) were digested in aqua regia using microwave digestion. The quantitative elemental analysis was carried out using inductively coupled plasma mass spectrometry. The variations of the elemental concentration in terms of workdays, weekends, seasons, and annual were determined at the three locations. The spatial and temporal elemental variations were found to be different between the three sites, pointing to local influences that should be further evaluated. The concentration of Cd was found to be high and may cause health problems.

Very little is known about the elemental composition and possible sources of fine aerosol particles from Mediterranean megacities. Fine aerosol particles were collected at a residential-industrial area in Greater Cairo, Egypt, during the period from October 2010 to May 2011. The elemental compositions of the collected samples were quantified by using a homemade energy dispersive x-ray fluorescence spectrometer, whereas black carbon was quantified by a black smoke detector. Fifteen elements have been quantified. Of these constituents, Ca, C, Cl, S, and Fe had the highest concentrations: greater than 1 µg m−3. The overall mean mass concentration of the collected samples equals 70 µg m−3; this value exceeds the European Union annual Air Quality Standard levels. The individual elemental concentrations of the fine particles were found to be dominated by elements linked to mineral dust. Most of the monthly variations of elemental concentrations can be attributed to seasonal meteorological conditions. Other possible sources were vehicle-exhaust and industrial activities. The results pinpoint the problem of identifying different sources when one source, in this case, the nearby deserts, is dominant. The results from this study contribute to the growing knowledge of concentrations, composition, and possible sources of ambient fine particulate matter.

Platinum group elements (PGE) including Ru, Rh, Pt and Pd have been quantified in air particulate matter with an aerodynamic diameter equal or less than 10 microns (PM10) using inductively coupled plasma mass spectrometry (ICP-MS). PM10 aerosols have been collected from three sites representing various activities in Jeddah city, Saudi Arabia. These locations are residential site with heavy traffic, industrial site and heavy traffic and a light traffic site outside the city. To obtain reasonable data of the PGE concentrations, a group from 10 to 15 PM10 samples were collected every month. The annual and seasonal variation of the mass concentration of the PGE were demonstrated. In all locations, Pt and Pd were relatively higher than Ru and Rh possibly because their main use is in automobile catalytic converters. Concentrations of observed PGE in PM10 could be arranged in ascending order as: Rh < Ru < Pd < Pt. In case of Ru and Pt, there are clear similarities in terms of the overall mean concentrations at the sampling locations. Due to the high concentration of Ru, Rh and Pd at low traffic site, there are certainly other sources of these elements rather than vehicle catalytic converters. However, at the industrial/heavy traffic location, high concentrations of Ru were detected during February 2015. In addition, high Pt concentrations were also detected at the light traffic site during May 2015. Results indicate that Pt source in PM10 is mainly the automobile catalytic converters.