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This study investigated the removal of methylene blue (MB) by different UV, UV-catalyzed H2O2 (UV/H2O2) and UV-and-iron-catalyzed H2O2 (UV/H2O2/Fe2+)-based advanced oxidation processes. At pH 6.0, the removal of MB (15 mg/L) was found to be 6.31% at 60 min for UV only. However, the combination of H2O2 (5 mM) with UV greatly enhanced the removal efficiency as 96.44% degradation of MB was found in the UV/H2O2 process at 60 min. Furthermore, the UV/H2O2/Fe2+ process was observed to be even more efficient than UV/H2O2, achieving 99.11% MB degradation at 30 min of treatment under the experimental conditions of [MB]0 = 15 mg/L, [H2O2]0 = 2 mM, [Fe2+]0 = 0.5 mg/L, and pH0 = 3.0. Furthermore, the removal of TOC was found to be 59 and 71% for UV/H2O2 and UV/H2O2/Fe2+, respectively. The pH did not change the efficiency of the UV/H2O2 process significantly; however, it greatly affected the efficiency of the UV/H2O2/Fe2+ system. The results demonstrate that both UV/H2O2 and UV/H2O2/Fe2+ could be used for the effective degradation and mineralization of MB. [ABSTRACT FROM AUTHOR]

This work investigated the photochemical degradation of malachite green (MG), a cationic triphenylmethane dye used as a coloring agent, fungicide, and antiseptic. UV photolysis was ineffective in the removal of MG as only 12.35% degradation of MG (10 mg/L) was achieved after 60 min of irradiation. In contrast, 100.00% degradation of MG (10 mg/L) was observed after 60 min of irradiation in the presence of 10 mM H2O2 by UV/H2O2 at pH 6.0. Similarly, complete removal (100.00%) of MG was observed at 30 min of the reaction time by UV/H2O2/Fe2+ employing [MG]0 = 10 mg/L, [H2O2]0 = 10 mM, [Fe2+]0 = 2.5 mg/L, and [pH]0 = 3.0. For the UV/H2O2 process, the degradation efficiency was higher at pH 6.0 than at pH 3.0 as the k obs values were 0.0873 and 0.0690 min−1, respectively. However, UV/H2O2/Fe2+ showed higher reactivity at pH 3.0 than at pH 6.0. Chloride and nitrate ions slightly inhibited the removal efficiency of MG by both UV/H2O2 and UV/H2O2/Fe2+ processes. Moreover, three degradation products (DPs) of MG, (i) 4-dimethylamino-benzophenone (DABP), (ii) 4-amino-benzophenone (ABP), and (iii) 4-dimethylamino-phenol (DAP), were identified by GC-MS during the UV/H2O2 treatment. These DPs were found to demonstrate higher aquatic toxicity than the parent MG, suggesting that researchers should focus on the removal of target pollutants as well as their DPs. Nevertheless, the results of this study indicate that both UV/H2O2 and UV/H2O2/Fe2+ processes could be implemented to alleviate the harmful environmental impacts of dye and textile industries. [ABSTRACT FROM AUTHOR]

The pyrolysis process of coconut residue and the activated carbon was investigated using thermogravimetric analysis in the range of 25 to 900 °C, with three altered heating rates: 3, 5, and 10 °C/min. The results of the thermal decomposition showed that it occurred in three distinct phases: dehydration, active pyrolysis, and passive pyrolysis. The derivative thermogravimetric analysis indicated that increasing the heating rate led to a shift in the maximum weight loss rate towards higher temperatures. To better understand the kinetics constraints, the Coats–Redfern method was applied to determine the activation energy (Ea) and the frequency factor (A). The activation energies for the pyrolysis process varied between 159.57 and 177.45 kJ/mol for RCR and from 132.62 to 147.1 kJ/mol for ACCR at different heating rates. Additionally, the physical properties of the samples were investigated using techniques like scanning electron microscopy and the Brunauer–Emmett–Teller surface analysis. The findings of the study demonstrated that the activation energies of the activated carbon were lower than those of the original biomass. Furthermore, the activation energy values achieved from the D1–D4 models were considered reliable, indicating that the D model was more suitable compared to other models for describing the pyrolysis process and predicting its kinetics. [ABSTRACT FROM AUTHOR]

In this study, carbon quantum dots (C-QDs), prepared via hydrothermal-microwave procedures, were successfully combined with nanostructured titania (TiO2). The photocatalytic oxidation/reduction activity of the C-QDs/TiO2 composite films was evaluated in the decomposition of organic-inorganic contaminants from aqueous solutions under UV illumination. Physicochemical characterizations were applied to investigate the crystal structure of the carbon quantum dots and the composites. It was found that the prepared C-QDs/TiO2 composites had great contribution to the photocatalytic reduction of hexavalent chromium (Cr+6) species and 4-Nitrophenol (PNP) as well as to the photocatalytic oxidation of methylene blue (MB) and Rhodamine B (RhB) dyes. The mechanism of the photocatalytic reaction was studied with trapping experiments, revealing that the electron (e−) radical species were powerfully supported for the photocatalytic reduction of Cr+6 and PNP and the holes (h+) are the main active species for the photocatalytic oxidation reactions. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzofurans (PCDFs) are persistent toxic compounds that are ubiquitous in the environment. Nanocomposites of titanium(IV) oxide-vanadium(III) oxide ( Ti 3 V 2 O 7 ) and titanium(IV) oxide-silicon dioxide ( Ti 2 Si 7 O 30 ) were prepared and spectroscopically analyzed as potential decontaminants for dioxin-like materials. The analysis confirmed a homogeneous morphology with nanoscale particle size. The Ti-Si sample was found to have a high surface area compared to the Ti-V composite. Vanadium(III) oxide (V2O5) and silicon dioxide (SiO2) were chosen as materials for the formation of heterogeneous compounds with titanium(IV) oxide (TiO2) because they possess a suitable band alignment with TiO2, thus forming effective photocatalysts. This study evaluated the photodegradation of 2,3,7,8-tetrachlorodibenzo-furan (TCDF) in the presence of Ti-Si and Ti-V oxide composites, which was tested using high- (254 nm) and midenergy (302 nm) UV irradiation sources. While Ti-Si showed success in the photodegradation of 2,3,7,8-TCDF dissolved in a (1:1) methanol–tetrahydrofuran (MeOH-THF) solution, the Ti-V composite proved to be a powerful material in adsorbing TCDF with a high capacity immediately upon mixing. Ti-Si oxide was found to decompose TCDF under the two irradiation sources with 98–99% degradation occurring after 70 min. The use of 254 nm as an irradiation source in the presence of Ti-Si was 4.3 times faster than the analogue reaction irradiated without a catalyst. Byproducts of the degradation were evaluated using gas chromatography–mass spectrometry (GC–MS), resulting in a lower chlorinated congener and less toxicity, as the main degradation product. [ABSTRACT FROM AUTHOR]

This study focuses on investigating and comparing the influence of the surface functional groups and chemical matrices of macroporous resin on the Cr(III) exchange mechanism. The results discussed herein indicate that sulfonic resin removed Cr(III) ions with faster kinetics than carboxylic resin. Equilibrium was established within 15 and 7 min for the carboxylic and sulfonic resins, respectively, with a 99.5% removal efficiency at 333 K. The Langmuir exchange capacity was observed to be higher for the sulfonic resin (1.5 mmol∙g−1) than the carboxylic resin (0.80 mmol∙g−1) at 333 K. The adsorption isotherms obtained for the carboxylic and sulfonic resins were H and S types, respectively, representing a higher affinity of the carboxylic resin for Cr(III) removal at a low metal ion concentration. Additionally, it was noted that the carboxylic resin preferentially co-sorbed H+ and Cr(OH)2+ ions below Cr(III) concentrations of 6–8 mmol.L−1. The H+ ions co-sorption was almost negligible, whereas the Cr(III) exchange was 87 and 34.5% for the carboxylic acid resin and sulfonic acid resins, respectively. The data of the concentration studies were evaluated using non-linear forms of Freundlich, Langmuir, and Dubinin–Radushkevich adsorption isotherm models, and the kinetic data were analyzed using pseudo-Ist- and pseudo-IIst-order kinetic models. The activation energy Ea for Amberlite IRC-50 (Na+) was greater (22.4 kJ∙mol−1) than that of Amberlyst-15 (Na+) 17 kJ∙mol−1, indicating a higher energy barrier for the ion exchange reaction on carboxylic resin. As per the findings of a statistical error analysis (RMSE and SSE) and absolute average relative distribution (AARD) statistical model, a close agreement between the experimental and theoretical values suggested that the Langmuir isotherm was well-fitted to the current adsorptive investigations. The interaction of the COO− and SO3− functional sites of the resins for the exchange of Cr(III) ions was validated through an FT-IR analysis. The macroporous resins used in the current study for Cr(III) exchange showed promising performances compared to other resins. The current investigations revealed valuable insights for choosing macroporous resins as adsorbents in water filtration systems. [ABSTRACT FROM AUTHOR]

In the current study, magnetic oxide nanoparticle-impregnated tea waste (TW-Fe3O4) is employed as an adsorbent to remove phosphate ions (PO43−) from an aqueous solution. By utilizing a variety of analytical methods, the TW-Fe3O4 nano-adsorbent was characterized by FE-SEM, TEM, EDX, BET, FTIR and XRD. The FE-SEM of TW-Fe3O4 demonstrated the adsorbent's granular morphology with a variety of magnetic nanoparticle sizes and shapes. The XRD of TW-Fe3O4 showed two diffraction peaks at 2θ values 30.9° and 35.4°, which are in correspondence with the diffraction pattern of magnetite. The synthesis of a TW-Fe3O4 adsorbent with a greater surface area and porosity was demonstrated by BET analysis. Numerous adsorption factors like initial concentration of PO43− ion, pH of the medium, contact time, temperature and adsorbent dose were optimized for phosphate removal. The maximum removal of 92% was achieved by using the adsorbent dose of 1.2 g at 323 K (pH 5). Pseudo-second-order and intra-particle diffusion models were fitted to the sorption kinetic, whereas adsorption isotherm data were found well fitted to Freundlich and Dubinin–Radushkevich (D-R) models. The highest adsorption capacity of TW-Fe3O4 towards phosphate ions was 226.8 mg/g, which is significantly higher than other reported bio-adsorbents. According to thermodynamic data, phosphate adsorption at the solid–liquid interface was of an endothermic and spontaneous nature and characterized by enhanced inevitability. [ABSTRACT FROM AUTHOR]

The article discusses the use of carbon-based nanomaterials for the detection and remediation of hazardous pollutants. Carbon materials, such as fullerenes, graphene, and carbon nanotubes, have been found to be highly effective at removing pollutants from the environment. The special issue of Environmental Science and Pollution Research focuses on the synthesis, characterization, and application of carbon-based materials in pollutant sequestration and water treatment. Various studies are highlighted, including the use of carbon nanotubes as adsorption materials, the development of biosensors for pollutant detection, and the synthesis of composite materials for photocatalytic degradation of pollutants. The article concludes by acknowledging the contributions of the authors and reviewers and emphasizes the importance of carbon-based materials in catalysis, energy generation, and environmental research. [Extracted from the article]

Diclofenac sodium was extensively used for treating arthritis, osteoarthritis and skeletal muscular injuries, which ultimately caused troubles for aquatic organisms as well as human beings. In this study, homogeneous catalytic advanced oxidation processes, including Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, were used for the degradation of diclofenac sodium in water, without using UV-C light. About 89, 82 and 54% DCF sodium was decomposed by Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, respectively, in 60 min. The degradation of diclofenac sodium followed the pseudo first-order kinetics, in all cases. The degradation efficiency of diclofenac sodium was significantly affected in the presence of various anions, such as NO3−, HCO3− and SO42−. The mineralization studies revealed 62, 45 and 32% total carbon removal by Fe2+/persulfate, Fe2+/peroxymonosulfate and Fe2+/H2O2, respectively, in 60 min. In addition, the degradation byproducts of diclofenac sodium were determined by FTIR analysis. The results revealed that the Fe2+/oxidant system, particularly Fe2+/persulfate, was a promising technology for the elimination of toxic pharmaceuticals, such as diclofenac sodium, from the water environment. [ABSTRACT FROM AUTHOR]

A subtle change in the geometry of nanoparticles affects the local electromagnetic field distribution and intensity of the analytes under optical excitation, which leads to distinguished enhancement effects on Raman signals. We report covalently modified gold–aryl nanocubes (AuNCs) for surface-enhanced Raman scattering (SERS). We performed transmission electron microscopy studies to investigate the morphology of AuNCs and UV–visible and Raman spectroscopy studies to understand their optical properties. Dynamic light scattering measurements, ζ-potential analyses, and contact angle measurements were performed to understand particle size distribution, surface charge, and wettability of the substrate. We obtained a high SERS enhancement (108) for AuNCs using 10−6 M rhodamine 6G (R6G, organic dye pollutant) as an analyte. AuNCs interact with the incoming electromagnetic wave, and due to the presence of multiple sharp corners ("hot spots"), there is a large enhancement of the electromagnetic field allowing the detection of 10−11 M R6G. The relative standard deviations were obtained within 5.8% for 10−6 M R6G, indicating excellent uniformity. Moreover, a wide linear range of 10−3–10−6 M was obtained for the detection of 4-nitrophenol (4-NPh, a high-priority toxic pollutant). These results indicate that highly SERS-active AuNCs could be successfully used for monitoring environmental contamination. [ABSTRACT FROM AUTHOR]

A nanocomposite (NC) of titanium (IV) oxide (TiO2) and molybdenum (VI) oxide (MoO3) was synthesized using a hydrothermal route. Detailed analyses using transmission electron microscopy, X-ray diffraction, X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) isotherms, X-ray photoelectron spectroscopy, Raman, and diffuse reflectance infrared Fourier transform spectroscopy were carried out and confirmed the successful formation of pure TiO2-MoO3 (Ti-Mo) NC. The Ti-Mo NC possesses sizes in the range of 150–500 nm. XPS, Raman, and DRIFT shift measurements confirmed the formation of mixed oxide linkage in the form of Ti-O-Mo. Sorption of nitrogen isotherms revealed a significant increase in the number and pore widths of mesopores in the NC. Water sorption isotherms revealed enhanced affinity of the nanocomposites for water relative to the pure metal oxides. The BET surface area for Ti-Mo NC from the nitrogen adsorption isotherm was 129.3 m2/g which is much higher than the pure metal oxides (i.e., 37.56 m2/g for TiO2 and 2.21 m2/g for MoO3). The Ti-Mo NC provided suitable adsorption sites that captured the studied carbamates from the solution and promoted their photodegradation process. The photocatalytic degradation of MB in the presence of the catalyst was enhanced by 2.9 and 5.5 folds upon irradiation with white LED and 302 nm UV light sources, respectively. [ABSTRACT FROM AUTHOR]

The removal of water pollutants by photocatalysis is a promising technique, mainly due to its environmentally friendly and sustainable nature. In this study, the degradation of a recalcitrant organic pollutant, malachite green (MG), was investigated in water by a microstructured silver oxide photocatalyst. The silver oxide (Ag2O) microparticles (MPs) were synthesized by a low-cost, green method, mediated by green tea leaves extract. The surface, morphological and optical properties of the synthesized Ag2O MPs were determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-visible) spectrophotometry. The synthesized Ag2O MPs showed good photoactivity, represented by 83% degradation of malachite green (MG) ([C]0 = 0.4 mM, Ag2O loading = 0.1 g L−1) at neutral pH, in 3 h. Persulfate ions (PS) showed a strong synergistic effect on the efficiency of solar/Ag2O photocatalysis, represented by complete MG removal in 15 min, in the presence of 1.6 mM PS. The results revealed that solar/Ag2O, particularly solar/Ag2O/PS photocatalysis is a promising method for the elimination of toxic organic pollutants, such as malachite green, from the water environment. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) was decorated with gold–aryl (Au–C) nanoparticles of AuNPs–COOH by sodium borohydride reduction of aryldiazonium tetrachloroaurate(III) salt at room temperature in aqueous solutions. Morphology of AuNPs–COOH/GO nanocomposite (NC) was probed using atomic force microscopy (AFM) and transmission electron microscopy (TEM), showing NC surface roughness and wrinkling. X-ray photoelectron spectroscopy (XPS) results suggest the clear reductive reaction of tetrachloroaurate anion into metallic gold in AuNPs–COOH/GO along with detailed interpretations of the nature of the functional groups. Brunauer–Emmett–Teller measurements supported GO anchoring by AuNPs modified with COOH; surface area dropped significantly. Molecular dynamics calculations endowed support of favorable wrinkling at the edges and carboxyl intercalation to GO surface of types π–π, hydrogen bonding, and hydrophobic interactions. Solvent accessible surface area calculations of GO showed a decrease in total surface area. [ABSTRACT FROM AUTHOR]

Galvanic replacement reaction was used in the synthesis of bimetallic gold–silver alloy nanoparticles (Au–Ag NPs), where pre-synthesized Ag nanoparticles-polyvinylpyrrolidone (AgNPs-PVP) were used to reduce the aryldiazonium tetrachloroaurate(III) salt in water. TEM images and EDS elemental analysis showed the formation of spherical Au–Ag NPs with sizes of 12.8 ± 4.9 nm and 25.6 ± 14.4 nm for corresponding Au–Ag ratios and termed as Au0.91Ag0.09 and Au0.79Ag0.21, respectively, with different concentrations of the gold precursor. The hydrodynamic sizes measured using dynamic light scattering are 46.4 nm and 74.8 nm with corresponding zeta potentials of − 44.56 and − 25.09 mV in water, for Au0.91Ag0.09 and Au0.79Ag0.21 respectively. Oxidative leachability of Ag ion studies from the starting AgNPs-PVP in 1 M NaCl showed a significant decrease in the plasmon peak after 8 h, indicating the complete dissolution of Ag ions, however, there is enhanced oxidation resistivity of Ag from Au–Ag NPs even after 24 h. Electrochemical studies on glassy carbon electrodes displayed a low oxidation peak in aqueous solutions of 20 mM KCl at 0.16 V and KNO3 at 0.33 V vs. saturated calomel electrode (SCE). We studied the antibacterial activity of Au–Ag alloy nanoparticles against gram-positive Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, and gram-negative Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa. Our findings demonstrated superior antibacterial activity of Au–Ag NPs compared with AgNPs-PVP. Moreover, the nanoparticles inhibited the S. epidermidis biofilm formation. [ABSTRACT FROM AUTHOR]

Compounds with antimicrobial activity have gained much attention in research due to the outbreak of coronavirus disease 2019 (COVID-19). Quaternary ammonium salts (QASs) are an emerging group of antibacterial agents that are used as disinfectants. Many studies have been carried out involving the applications of QASs as antifouling agents for the inhibition of biofilm growth on medical implants and antibacterials on surfaces and in an aquatic environment. In investigating the antibacterial activity of QASs, we addressed the structure-activity relationship and the physicochemical factors. This review is focused on the fine-tuning of the chemical structures of QASs for their applications as wide antibacterial agents. [ABSTRACT FROM AUTHOR]

Fluorescence labeling of gold-aryl nanoparticles, AuNPs-COOH, was achieved by the covalent derivatization with dansyl chloride (DNS-Cl) reagent (5-naphthalene-1-sulfonyl chloride) for potential ssDNA recognition. The fluorescent gold nanoparticles of AuNPs-C6H4-4-COO-dansyl (AuNPs-DNS) of spherical shape and a size of 19.3 ± 8.3 nm were synthesized in a carbonate-bicarbonate buffer (pH = 10.6) at 37 °C. The fluorescence emission at 475 nm was acquired using fluorescence spectroscopy and investigated using time-resolved photoluminescence. The conjugation of ssDNA to AuNPs-DNS using the freeze-thaw and salt-aging methods was confirmed by fluorescence emission quenching, gel electrophoresis separation, and lifetime decrease. Conjugated ssDNA to AuNPs-DNS using the freeze-thaw method was more efficient than the salt-aging method. The purity of ssDNA upon conjugation was measured with optical density, and the obtained A260/A280 ratio was in the range of 1.7–2.0. This research can be applied to other nucleotide recognition and theranostics. [ABSTRACT FROM AUTHOR]

Photocatalysis is a promising process for decomposing harmful organic pollutants in water. In this study, solar/photocatalytic degradation of two model azo dyes, i.e., methylene blue (MB) and methyl red (MR), in water usinga nanostructured chitosan-modified nickel magnetite (CS-NM) bio-composite was investigated. The CS-NM bio-composite was synthesized through a co-precipitation method and characterized by Fourier transform infrared (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), thermogravimetry (TGA), and UV-Vis spectroscopy. FTIR analysis showed the uniform incorporation and conjugation of nickel magnetite (NM) into the chitosan (CS) polymer matrix. SEM showed that the average particle size was 0.5 μm. The TGA results revealed the good thermal stability of the prepared bio-composite at 300 °C. The point of zero charge was calculated as 7.5. The effect of water quality and process parameters, such as concentration of dyes, catalyst dose, solution pH, and temperatures, was investigated, for application purposes. The solar/CS-NM photocatalysis resulted in 99 and 96% degradation of individual MB and MR (C0 = 50 ppm), respectively, in 90 min. The degradation of MB and MR by solar/CS-NM photocatalysis followed pseudo-first-order kinetics, with observed rate constants (k) of 0.077 and 0.072 min−1, respectively. The CS-NM photocatalyst showed high recyclability, represented by only a 4–6% loss in the photocatalytic efficiency, after four cycles. The results showed that solar/CS-NM photocatalysis is an efficient technique for degrading recalcitrant organic pollutants, such as azo dyes, in water environments. [ABSTRACT FROM AUTHOR]

Electrocatalytic hydrogen evolution reactions (HER) offer an enduring strategy for hydrogen fuel production and are vital for sustainable energy conversion and storage. To explore efficient and durable HER electrocatalysts, we fabricated gold-aryl nanoparticles (AuNPs-COOH) anchored on graphitic carbon nitride (g-C3N4) sheets by reducing aryldiazonium tetrachloroaurate(III) salt with sodium borohydride at room temperature in water. Two different nanocomposites, AuNPs-COOH-g-C3N4 (H) (higher amount of g-C3N4) and AuNPs-COOH-g-C3N4 (L) (lower amount of g-C3N4) were prepared. Contact angle measurements revealed that the increased surface wettability of the nanocomposites on glass and silicon wafer surfaces compared to pristine g-C3N4. Cyclic voltammetry, electrochemical impedance spectroscopy, double-layer capacitance, linear sweep voltammetry, and chronoamperometry measurements revealed that AuNPs-COOH-g-C3N4 (L) displayed the best HER performance in 0.1 M H2SO4 electrolyte. Overall, nanocomposites exhibited higher electrocatalytic activity compared to bare AuNPs-COOH and pristine g-C3N4 in current density and onset potential values. The AuNPs-COOH-g-C3N4 (L) nanocomposite offered an excellent electrocatalytic activity and displayed a current density of 53.4 mA/cm2 at 0.72 V vs RHE, which is nearly twice compared to bare AuNPs-COOH of 33.1 mA/cm2. In addition, the nanocomposite showed the lowest onset potential of 0.14 V vs RHE compared to 0.26 V and 0.31 V for AuNPs-COOH-g-C3N4 (H) and AuNPs-COOH, respectively. [ABSTRACT FROM AUTHOR]

Investigating transition metal oxidants is a fundamental scientific interest for the synthesis of polymer nanocomposites. In this study, we attempted for the first time to use aryldiazonium cation stabilized with tetrachloroaurate(III) anion [AuCl4]− in the polymerization of aniline monomer. The reaction was achieved using high mole ratios of oxidant/aniline which resulted in the formation of polyaniline nanocomposites (PANI NCs) of gold-aryl NPs. The facile polymerization can be ascribed to the correlation of the redox potentials of both aniline monomer and diazonium salt (oxidant). Emeraldine-coated gold-aryl NPs were efficiently synthesized at high oxidant/aniline mole ratios of 3:1 and 4:1. UV–visible displayed a broad peak centered at 900 nm assigned to HCl doped emeraldine. However, low oxidant/aniline mole ratios of 1:4 and 1:1 were not successful in aniline polymerization. The thermal gravimetric analysis concluded the stability of PANI NCs with gold percentage residues of 17–20 wt%. High oxidant/aniline mole ratios of 3:1 and 4:1 showed particle sizes in the range of 20–25 nm in transmission electron microscopy images. The emerging oxidant based on diazonium gold salt could be used for the synthesis of other metal and metalloid nanocomposites for energy and environmental applications. This work is critical in establishing our knowledge on diazonium salts stabilized with gold-based anions as friendly oxidants toward aniline and possibly other reducible monomers such as phenol, thiophene, and pyrrole. [ABSTRACT FROM AUTHOR]

Due to exponential industrialization and rapid population growth, the global energy crisis and environmental pollution have become two of the greatest humanitarian challenges of the 21st century [[1]]. Interestingly, the modification of photocatalysts' surface with metals has been shown in all these studies, confirming their crucial functions for various reactions, being co-catalysts, dopants, and sensitizers. The first-generation Z-scheme photocatalysts need a redox mediator dissolved in a liquid phase (traditional Z-scheme), then a solid mediator has been used (all-solid-state/second generation Z-scheme), and, finally, the direct Z-scheme photocatalysts without redox mediator have been developed [[10]]. The ternary photocatalyst, composed of titania, copper, and graphene (TiO SB 2 sb /Cu/G), was obtained by Lewandowski et al. in a fluidized bed reactor [[16]]. [Extracted from the article]

Antibiotics are the most common pharmaceutical compounds, and they have been extensively used for the prevention and treatment of bacterial diseases for more than 50 years. However, merely a small fraction of antibiotics is metabolized in the body, while the rest is discharged into the environment through excretion, which can cause potential ecological problems and human health risks. In this study, the elimination of seventeen antibiotics from real livestock wastewater effluents was investigated by UV/TiO2 advanced oxidation process. The effect of process parameters, such as TiO2 loadings, solution pHs, and antibiotic concentrations, on the efficiency of the UV/TiO2 process was assessed. The degradation efficiency was affected by the solution pH, and higher removal efficiency was observed at pH 5.8 and 9.9, while the catalyst loading had no significant effect on the degradation efficiency at these experimental conditions. UV photolysis showed a good removal efficiency of the antibiotics. However, the highest removal efficiency was shown by the UV/photocatalyst system due to their synergistic effects. The results showed that more than 90% of antibiotics were removed by UV/TiO2 system during the 60 min illumination, while the corresponding TOC and COD removal was only 10 and 13%, respectively. The results of the current study indicated that UV/TiO2 advanced oxidation process is a promising method for the elimination of various types of antibiotics from real livestock wastewater effluents. [ABSTRACT FROM AUTHOR]

Biomimetic synthesis of gold nanoparticles (GNPs) is critical in biomedical applications. Gold bioconjugates were fabricated by capping the water-dispersible gold-carbon nanoparticles with tyrosine, tryptophan and cysteine amino acids. Incubation of the water-soluble and easily reducible aryldiazonium gold(III) salt [HOOC-4-C6H4N≡N]AuCl4 with amino acids at room temperature formed a purple color over a few minutes with tryptophan and tyrosine and over two hours with cysteine. Rarely that cysteine is capable of reducing gold(III) precursors; however, a cysteine capped gold bioconjugate was synthesized and characterized in this study. Capping GNPs with amino acids was confirmed by high resolution transmission electron microscopy (TEM) and agarose gel electrophoresis. Depending on the amino acid, synthesized particles size was 27.2 ± 5.4 nm, 14.6 ± 7.7 nm and 8.6 ± 2.6 nm for tyrosine, tryptophan and cysteine, respectively. The amino acids capped GNPs showed negligible cytotoxicity to human dermal normal fibroblast cell lines. The highly water dispersible bioconjugates were studied for in vitro cellular uptake by HeLa cancer cells using confocal laser scan microscopy (CLSM) after being labelled with FITC (GNPs-COOH-FITC) and the nuclei were counter stained with DAPI fluorescent dyes. The biomimetic route for the synthesis of the amino acids reduced gold-carbon nanoparticles will benefit the applications in biomedical devices and biosensors. [ABSTRACT FROM AUTHOR]

In this study, a simple and low-cost method to synthesize iron(III) oxide nanopowders in large quantity was successfully developed for the photocatalytic degradation of microcystin-LR (MC-LR). Two visible light-active iron(III) oxide samples (MG-9 calcined at 200 °C for 5 h and MG-11 calcined at 180 °C for 16 h) with a particle size of 5-20 nm were prepared via thermal decomposition of ferrous oxalate dihydrate in air without any other modifications such as doping. The synthesized samples were characterized by X-ray powder diffraction, Fe Mössbauer spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller (BET) specific surface area analysis, and UV-visible diffuse reflectance spectroscopy. The samples exhibited similar phase composition (a mixture of α-FeO and γ-FeO), particle size distribution (5-20 nm), particle morphology, and degree of agglomeration, but different specific surface areas (234 m g for MG-9 and 207 m g for MG-11). The results confirmed higher photocatalytic activity of the catalyst with higher specific surface area. The highest photocatalytic activity of the sample to decompose MC-LR was observed at solution pH of 3.0 and catalyst loading of 0.5 g L due to large amount of MC-LR adsorption, but a little iron dissolution of 0.0065 wt% was observed. However, no iron leaching was observed at pH 5.8 even though the overall MC-LR removal was slightly lower than at pH 3.0. Thus, the pH 5.8 could be an appropriate operating condition for the catalyst to avoid problems of iron contamination by the catalyst. Moreover, magnetic behavior of γ-FeO gives a possibility for an easy separation of the catalyst particles after their use. [ABSTRACT FROM AUTHOR]

Direct oxidative esterification of alcohol via photocatalytic C–H activation has been developed using VO@g-C3N4 catalyst; an expeditious esterification of alcohols occurs under neutral conditions using visible light as the source of energy. [ABSTRACT FROM AUTHOR]

Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning a graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for the expeditious C–H activation and cyanation of amines. [ABSTRACT FROM AUTHOR]

Bimetallic alloy nanoparticles (NPs) of two coinage metals, Au and Ag, were successfully synthesized by a co-precipitation method. These NPs were prepared by a chemical method involving the reduction of HAuCl and AgNO in an aqueous solution of 2 % hydrazine as a reducing agent, iso-octane as a co-precipitator, cetyl trimethyl ammonium bromide as a capping agent, and deionized water as a solvent. The newly synthesized bimetallic alloy NPs were characterized by electronic absorption spectroscopy. The NPs were further characterized by scanning electron microscopy, transmission electron microscopy (TEM), and energy-dispersive spectroscopy. TEM evidenced the formation of NPs with a diameter ranging from 25 to 35 nm. For the development of electrochemical sensor, glassy carbon electrode (GCE) was modified with potentiodynamic polymerization of pyrrole, called polypyrrole (PPy). PPy was over-oxidized in order to increase its sensitivity toward polyaromatic hydrocarbons. The electrode was further modified with Au-Ag bimetallic alloy NPs. The fabricated GCE was successfully applied to detect an environmental toxin, pyrene. The electrochemical behavior of pyrene at the composite electrode (PPyox/Au-Ag NPs/GCE) was optimized by changing the atomic ratio of Au and Ag in Au-Ag bimetallic alloy NPs. At the Au and Ag ratio of 1:3, pyrene was detected with a detection limit of 0.1 µM. [ABSTRACT FROM AUTHOR]

Noble metal Ag-decorated, monodisperse TiO aggregates were successfully synthesized by an ionic strength-assisted, simple sol-gel method and were used for the photocatalytic degradation of the antibiotic oxytetracycline (OTC) under both UV and visible light (UV-visible light) irradiation. The synthesized samples were characterized by X-ray diffraction analysis (XRD); UV-vis diffuse reflectance spectroscopy; environmental scanning electron microscopy (ESEM); transmission electron microscopy (TEM); high-resolution TEM (HR-TEM); micro-Raman, energy-dispersive X-ray spectroscopy (EDS); and inductively coupled plasma optical emission spectrometry (ICP-OES). The results showed that the uniformity of TiO aggregates was finely tuned by the sol-gel method, and Ag was well decorated on the monodisperse TiO aggregates. The absorption of the samples in the visible light region increased with increasing Ag loading that was proportional to the amount of Ag precursor added in the solution over the tested concentration range. The Brunauer, Emmett, and Teller (The BET) surface area slightly decreased with increasing Ag loading on the TiO aggregates. Ag-decorated TiO samples demonstrated enhanced photocatalytic activity for the degradation of OTC under UV-visible light illumination compared to that of pure TiO. The sample containing 1.9 wt% Ag showed the highest photocatalytic activity for the degradation of OTC under both UV-visible light and visible light illumination. During the experiments, the detected Ag leaching for the best TiO-Ag photocatalyst was much lower than the National Secondary Drinking Water Regulation for Ag limit (0.1 mg L) issued by the US Environmental Protection Agency. [ABSTRACT FROM AUTHOR]

Conventional titanium dioxide (TiO2) materials can be activated only by ultraviolet (UV) light, which is only 4-5% of the whole solar spectrum. As a result, visible light (vis)-active TiO2-based photocatalysts have recently received significant attention in the field of TiO2 photocatalytic treatment and purification of water and air. This study reports the preparation of UV-visible light-active phosphorous (P)-doped, fluorine (F)-doped, and PF-co-doped anatase TiO2 nanoparticles via an innovative sol-gel method. Prepared nanoparticles were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and porosimetry analysis. Synthesized materials exhibited improved structural properties, including high surface area, small crystallite size, reduced band gap energy, mesoporous structure, and high porosity. Due to doping with P and F, light absorption of TiO2 in the visible light region was efficiently enhanced with effective band gap energy of 2.70 eV. Brunauer-Emmett-Teller (BET) surface area for PF-co-doped, P-doped, F-doped, and reference TiO2 nanoparticles was 212.0, 175.0, 88.8, and 79.7 m2/g, respectively. PF-co-doped TiO2 showed the highest photocatalytic degradation of atrazine, which could be attributed to the beneficial effects including small crystallite size, high BET surface area, and light absorption in UV-visible region, induced by co-doping of TiO2 with P and F. Finally, reaction intermediates were determined, which confirms the photocatalytic degradation of atrazine using the synthesized catalysts under UV-visible light illumination. [ABSTRACT FROM AUTHOR]

A multiwalled carbon nanotube (MWCNT)-based electrochemical biosensor is developed for monitoring microcystin-LR (MC-LR), a toxic cyanobacterial toxin, in sources of drinking water supplies. The biosensor electrodes are fabricated using vertically well-aligned, dense, millimeter-long MWCNT arrays with a narrow size distribution, grown on patterned Si substrates by water-assisted chemical vapor deposition. High temperature thermal treatment (2500 °C) in an Ar atmosphere is used to enhance the crystallinity of the pristine materials, followed by electrochemical functionalization in alkaline solution to produce oxygen-containing functional groups on the MWCNT surface, thus providing the anchoring sites for linking molecules that allow the immobilization of MC-LR onto the MWCNT array electrodes. Addition of the monoclonal antibodies specific to MC-LR in the incubation solutions offers the required sensor specificity for toxin detection. The performance of the MWCNT array biosensor is evaluated using micro-Raman spectroscopy, including polarized Raman measurements, X-ray photoelectron spectroscopy, cyclic voltammetry, optical microscopy, and Faradaic electrochemical impedance spectroscopy. A linear dependence of the electron-transfer resistance on the MC-LR concentration is observed in the range of 0.05 to 20 μg L−1, which enables cyanotoxin monitoring well below the World Health Organization (WHO) provisional concentration limit of 1 μg L−1 for MC-LR in drinking water. [ABSTRACT FROM AUTHOR]

Towers of aligned multiwalled carbon nanotubes (MWCNTs) were electrochemically oxidized in aqueous 1 M NaOH. An oxidation current that decayed with time was monitored using amperometry at a fixed potential. Cyclic voltammetry showed that the background current and electrode capacitance increased after oxidation without significantly affecting the faradaic current from the reduction of ferricyanide. Oxidation in NaOH caused morphological changes and increased hydrophilicity of the MWCNT tower electrodes. XPS spectra indicated increased oxygen on the surface after oxidation, while Raman spectra indicated that a large amount of amorphous carbon was present before and after oxidation. [ABSTRACT FROM AUTHOR]

Organochlorine compounds (OCs) are very toxic, highly persistent, and ubiquitous contaminants in the environment. Degradation of lindane, a selected OC, by simulated solar light-activated TiO2 (SSLA-TiO2) photocatalysis was investigated. The film types of the TiO2 photocatalyst were prepared using a dip-coating method. The physical properties of the films were investigated using X-ray diffraction, transmission electron microscopy, and environmental scanning electron microscopy. The SSLA-TiO2 photocatalysis led to a lindane removal of 23% in 6 h, with 0.042 h−1 of an observed pseudo first-order rate constant (kobs). The SSLA-TiO2 photocatalysis efficiency was greatly enhanced by adding hydrogen peroxide (H2O2), persulfate (S2O82−), or both combined, corresponding to a 64%, 89%, and 99% lindane removal in the presence of 200 µM of H2O2, S2O82−, or equimolar H2O2-S2O82−, respectively. The hydroxyl and sulfate radicals mainly participated in lindane degradation, proven by the results of a radical scavenger study. The degradation kinetics were hindered in the presence of the water constituents, indicated by a 61%, 35%, 50%, 70%, 88%, and 91% degradation of lindane in 6 h, using a SSLA-TiO2/S2O82−/H2O2 photocatalysis system containing 1.0 mg L−1 humic acid (HA), or 1 mM of CO32−, HCO3−, NO3−, SO42−, and Cl−, respectively. The TiO2 film demonstrated high reusability during four runs of lindane decomposition experiments. The SSLA-TiO2/S2O82−/H2O2 photocatalysis is very effective for the elimination of a persistent OC, lindane, from a water environment. [ABSTRACT FROM AUTHOR]

The cover image is based on the Full Paper Gold‐Aryl nanoparticles coated with polyelectrolytes for adsorption and protection of DNA against nuclease degradation by Seema Panicker et al., https://doi.org/10.1002/aoc.4803. Design Credit: Abdallah Mouselly, Architecture Department, University of Sharjah. [ABSTRACT FROM AUTHOR]

Binding DNA on nanoparticles was pursued to form nanoplatform for formation of non‐viral gene system. Carboxyl derivatized gold‐aryl nanoparticles can bind with biodegradable cationic polyelectrolytes such as polydiallyldimethylammonium chloride (PDADMAC). In our study, we used gold‐aryl nanoparticles (AuNPs) treated with PDADMAC to form conjugates with non‐thiol or non‐disulfide modified oligonucleotide DNA. Both AuNPs‐DNA and PDADMAC‐AuNPs‐DNA biomaterials were characterized using UV–Vis, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and agarose gel electrophoresis. UV–Vis showed a red shift in the plasmon peak as compared with unconjugated AuNPs. DLS measurements also showed difference in the size of AuNPs‐DNA and PDADMAC‐AuNPs‐DNA. AFM and TEM results showed proper conjugation of DNA with AuNPs. Gel electrophoresis proved the presence of interaction between PDADMAC‐AuNPs and negatively charged DNA. The binding of DNA in the described bioconjugate enhanced its protection against nuclease degradation and prolonged its presence in the digestive environment of DNase‐I. From the results we expect that these biomaterials can be used in nanomedicine with emphasis on non‐viral gene system. A simple method was developed to protect DNA from enzymatic degradation by conjugation with gold‐aryl nanoparticles. [ABSTRACT FROM AUTHOR]

Various compositions of barium carbonate (BaCO3) loaded polycaprolactone (PCL) composites were prepared, including 2.5/97.5, 10/90, 30/70, 50/50 and 90/10 (PCL/BaCO3), via re-precipitation technique. Small-scale column tests were conducted to study the efficiency of sulfate removal using the PCL/BaCO3 composites. The composites before and after their use to remove sulfate were extensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), high-resolution TEM (HR-TEM), and thermogravimetric analysis (TGA). As PCL is a biodegradable polymer, these composites are environmentally friendly and have several advantages over barium sulfate precipitation in overcoming clogging issues in filters or resins due to collection of natural organic matter (NOM). The media used in this study exhibited high capacity and was able to remove more than 90% sulfate from synthetic sulfate containing waters and NOM samples collected from the Ohio River. [ABSTRACT FROM AUTHOR]

To investigate the effect of Al0.82In0.18N electron blocking layer (EBL) on the efficiency droop, (0001) oriented InGaN light emitting diodes (LEDs) were grown with two different types of EBLs-single Al0.82In0.18N:Mg layer and Al0.82In0.18N:Mg (2 nm)/GaN:Mg (2 nm) superlattice (SL) structure with 7 periods. It was found that the output power and operating voltage of single Al0.82In0.18N EBL LED were sensitive to EBL thickness due to the difficulty in growing high quality Mg doped Al0.82In0.18N. On the other hand, LED with SL EBL showed no deterioration of optical power and operating voltage while its efficiency droop (17% at 300 A/cm2) reduced by more than a half compared to a conventional Al0.2Ga0.8N (20 nm) EBL LED (36% at 300 A/cm2). [ABSTRACT FROM AUTHOR]

We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO2 (C–TiO2) nanoparticles, synthesized by a modified sol–gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C–TiO2 nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO2. Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti–C and C–O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C–TiO2, whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C–TiO2 nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO2, behavior that is attributed to the incorporation of carbon into the titania lattice. [ABSTRACT FROM AUTHOR]