Transmission Electron Microscopy Analysis Research Articles

Sustainable and Reusable Modified Membrane Based on Green Gold Nanoparticles for Efficient Methylene Blue Water Decontamination by a Photocatalytic Process.

Methylene blue (MB) is a dye hazardous pollutant widely used in several industrial processes that represents a relevant source of water pollution. Thus, the research of new systems to avoid their environmental dispersion represents an important goal. In this work, an efficient and sustainable nanocomposite material based on green gold nanoparticles for MB water remediation was developed. Starting from the reducing and stabilizing properties of some compounds naturally present in Lambrusco winery waste (grape marc) extracts, green gold nanoparticles (GM-AuNPs) were synthesized and deposited on a supporting membrane to create an easy and stable system for water MB decontamination. GM-AuNPs, with a specific plasmonic band at 535 nm, and the modified membrane were first characterized by UV-vis spectroscopy, X-ray diffraction (XRD), and electron microscopy. Transmission electron microscopy analysis revealed the presence of two breeds of crystalline shapes, triangular platelets and round-shaped penta-twinned nanoparticles, respectively. The crystalline nature of GM-AuNPs was also confirmed from XRD analysis. The photocatalytic performance of the modified membrane was evaluated under natural sunlight radiation, obtaining a complete disappearance of MB (100%) in 116 min. The photocatalytic process was described from a pseudo-first-order kinetic with a rate constant (k) equal to 0.044 ± 0.010 min-1. The modified membrane demonstrated high stability since it was reused up to 20 cycles, without any treatment for 3 months, maintaining the same performance. The GM-AuNPs-based membrane was also tested with other water pollutants (methyl orange, 4-nitrophenol, and rhodamine B), revealing a high selectivity towards MB. Finally, the photocatalytic performance of GM-AuNPs-based membrane was also evaluated in real samples by using tap and pond water spiked with MB, obtaining a removal % of 99.6 ± 1.2% and 98.8 ± 1.9%, respectively.

Green synthesis of ZnO, Fe3O4, and TiO2 nanoparticles: exploring enhanced bacterial inhibition, catalysis, and photocatalysis for sustainable environmental applications

ABSTRACT This study investigates the physicochemical and biological properties of metal oxide nanoparticles (TiO2, ZnO, and Fe3O4) synthesised via the phytosynthesis method using an extract from Boerhaavia diffusa leaves (BDL). The proteins and phenols present in the BDL extract played essential roles in reducing and stabilising TiO2, ZnO, and Fe3O4 nanoparticles. The study reveals size-dependent morphological, structural, and biological characteristics of the produced nanoparticles. FTIR spectra confirm the involvement of BDL extract in the synthesis process of TiO2, ZnO, and Fe3O4 nanoparticles. Transmission electron microscopy (TEM) analysis of TiO2 nanoparticles identified small, spherical particles (9 nm in diameter). BDL-derived TiO2, ZnO, and Fe3O4 demonstrated significant photocatalytic activity, achieving degradation rates of 98.96%, 96.26%, and 94.42%, respectively, in the decomposition of mono-azo dye after 40 minutes of UV irradiation. The reaction rates for BDL-derived TiO2, ZnO, and Fe3O4 were 0.367/min, 0.186/min, and 0.061/min, respectively, when catalysing the reduction of 4-Nitrophenol (4-NP) to 4-Aminophenol using NaBH4. BDL-derived TiO2 nanoparticles exhibited significant antibacterial effectiveness, showing a 23.6 mm zone of inhibition against Salmonella typhi. The BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles exhibited remarkable cytotoxicity against lung cancer cell lines with IC50 values of 76.36 µg/mL, 90.21 µg/mL, and 94.61 µg/mL, respectively. This study reveals the potential of BDL-derived TiO2, ZnO, and Fe3O4 nanoparticles for applications in antibacterial, anticancer, catalytic, and photocatalytic fields, contributing to sustainable development of multifunctional nanomaterials for various technical and environmental advancements.

Resolving the Role of Configurational Entropy in the Optimization of Mechanical, Thermal, and Microwave Dielectric Properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 Ceramics.

The demand for high-performance microwave dielectric ceramics has surged with the proliferation of fifth-generation (5G) communication networks. In this work, SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 (x = 0-0.20) ceramics were designed by leveraging the unique properties of SrLaAlO4 ceramics and high-entropy engineering. The effects of configurational entropy (Sconf = 1.23R - 1.54R) on the mechanical, thermal, and microwave dielectric properties of SrLa(Al0.50-xGaxZn0.125Mg0.125Ti0.25)O4 ceramics were investigated. X-ray diffractometer and transmission electron microscope analyses confirmed that each composition belonged to the tetragonal structure with a space group of I4/mmm. Significant improvements in Vickers hardness were observed with increasing Sconf, reaching 8.05 GPa at Sconf = 1.54R compared to 5.64 GPa in SrLaAlO4 ceramics. Additionally, the increasing entropy showed great potential in reducing the thermal expansion coefficient (CTE) from 12.32 to 11.49 ppm/°C. The optimal quality factor (Q × f) of 98,000 GHz was achieved at Sconf = 1.37R, attributed to the optimization of intrinsic lattice energy and infrared-damped modes. The temperature coefficient of resonant frequency (τf) was successfully modified toward zero due to entropy-driven CTE and structural modifications. Excellent microwave dielectric properties with εr = 22.5, Q × f = 98,000 GHz, and τf = -2.0 ppm/°C were obtained at Sconf = 1.37R. This work highlights the potential of entropy-engineering in developing high-performance microwave dielectric ceramics, offering a promising pathway for the advancement of 5G communication components.

Enhanced analog switching and neuromorphic performance of ZnO-based memristors with indium tin oxide electrodes for high-accuracy pattern recognition.

This study systematically investigates analog switching and neuromorphic characteristics in a ZnO-based memristor by varying the anodic top electrode (TE) materials [indium tin oxide (ITO), Ti, and Ta]. Compared with the TE materials (Ti and Ta), memristive devices with TEs made of ITO exhibit dual volatile and nonvolatile switching behavior and multistate switching characteristics assessed based on reset-stop voltage and current compliance (ICC) responses. The polycrystalline structure of the ZnO functional layer sandwiched between ITO electrodes was confirmed by high-resolution transmission electron microscopy analysis. The current transport mechanism in the ZnO-based memristor was dominated by Schottky emission, with the Schottky barrier height modulated from 0.26 to 0.4V by varying the reset-stop voltage under different ICC conditions. The long-term potentiation and long-term depression synaptic characteristics were successfully mimicked by modulating the pulse amplitudes. Furthermore, a 90.84% accuracy was achieved using a convolutional neural network architecture for Modified National Institute of Standards and Technology pattern categorization, as demonstrated by the confusion matrix. The results demonstrated that the ITO/ZnO/ITO/Si memristor device holds promise for high-performance electronic applications and effective ITO electrode modeling.

Local structure maturation in high entropy oxide (Mg,Co,Ni,Cu,Zn)1‐x(Cr,Mn)xO thin films

AbstractHigh entropy oxides (HEOs) have garnered much interest due to their available high degree of tunability. Here, we study the local structure of (MgNiCuCoZn)0.167(MnCr)0.083O, a composition based on the parent HEO (MgNiCuCoZn)0.2O. We synthesized a series of thin films via pulsed laser deposition at incremental oxygen partial pressures. X‐ray diffraction shows lattice parameters to decrease with increased pO2 pressures until the onset of phase separation. X‐ray absorption fine structure shows that specific atomic species in the composition dictate the global structure of the material as Cr, Co, and Mn shift to energetically favorable coordination with increasing pressure. Transmission electron microscopy analysis on a lower‐pressure sample exhibits a rock salt structure, but the higher‐pressure sample reveals reflections reminiscent of the spinel structure. In all, these findings give a more complete picture of how (MgNiCuCoZn)0.167(MnCr)0.083O forms with varying initial conditions and advances fundamental knowledge of cation behavior in high entropy oxides.

MnCo2O4 nanospheres entrapped in g-C3N4 network for High-Performance supercapacitor applications

MnCo2O4 nanospheres were embedded in a g-C3N4 network using the solvothermal method with ethylene glycol as the solvent. SEM confirmed the uniformity of the MnCo2O4/g-C3N4 nanospheres, while XRD and XPS were used for structural and elemental analysis, including metal oxidation states. BET analysis revealed the surface area and porosity, while TEM analysis provided information on the interplanar spacing and morphology. Electrochemical evaluations using CV, GCD, and EIS demonstrated that the 2D g-C3N4 nanosheets interwoven with MnCo2O4 nanospheres have excellent specific capacities (654 Fg−1 at 2 Ag−1) and power densities (1521.2 W/kg at 7 Ag−1). The electrode material shows superior cyclic stability with 92.3 % capacitance retention after 5000 cycles.

Collapse of G+/G- bands, modification of Breit–Wigner–Fano signals and structural amorphization in single wall carbon nanotube networks under great excess of sulfur

The identification of superconductivity and ferromagnetic to superconductive transitions in sulfur-modified carbons has recently attracted an important attention. Additional work is however needed to better understand the structural modification of the graphitic interfaces in presence of sulfur. Here we report on an advanced methodology which involves soaking of large amounts (in the order of 500 mg) of sulfur through several annealing cycles into bundles comprising of hollow single-wall/few-wall carbon nanotubes (SWCNTs). TEM, HRTEM, XRD and Raman spectroscopy characterization analyses reveal the presence of structural amorphization of the SWCNTs, with dramatic impact on the intensity of the G+ and a progressive vanishing of the G- signal-contribution. We demonstrate the presence of high sulfur content by employing both point and mapping energy dispersive X-rays (EDX maps) acquisitions, with high local quantities of sulfur in the order of 16 %. Interestingly, a complex variation in the contribution of the Breit-Wigner-Fano (BWF) band, with appearance of extra D, G+ and C-S band-contributions, is revealed by deconvolution-analyses. The appearance of these structural features is a clear indicator of structural amorphization of the CNTs, with consequential formation of C-S hybrid structures, which we analyze systematically with the aid of energy dispersive X-ray spectrum mapping and Raman point/mapping spectroscopy approaches.

Unveiling Nanoscale Ordering in Amorphous Semiconducting Polymers Using Four-Dimensional Scanning Transmission Electron Microscopy.

We present four-dimensional (4D) scanning transmission electron microscopy (STEM) analysis to obtain a high level of detail regarding the nanoscale ordering within largely disordered organic semiconducting polymers. Understanding nanoscale molecular ordering in semiconducting polymers is crucial due to its connection to the materials' important properties. However, acquiring such information in a spatially localized manner has been limited by the lack of a nanoscale experimental probe, weak signal from ordering, and radiation damage to the sample. By collecting nanodiffraction patterns with a high dynamic range pixelated detector, we acquired statistically robust, high signal-to-noise ratio diffraction patterns from semiconducting organic materials, including poly(3-hexylthiophene-2,5-diyl) (P3HT), P3HT/[6,6]-phenyl C61 butyric acid methyl ester, and indacenodithiophene-co-benzothiadiazole (IDTBT), which largely have disordered structures. Real-space images of the ordered domains were reconstructed from the 4D-STEM data set for a variety of scattering vectors and in-plane angles to capture the different molecular stacking distances and their in-plane orientation. These were then analyzed to obtain the average size of the ordered domains within the sample. Such measurements were arranged in a two-dimensional (2D) histogram, which showed a direct relationship between the type and size of molecular ordering. Complementary analyses, such as intensity variance and angular correlation, were applied to obtain ordering and symmetry information. These analyses enabled us to directly characterize the alkyl and π-π stacking of P3HT, as well as the fullerene domains caused by donor segregation in the P3HT sample. Furthermore, the analysis also captured changes in the P3HT domains when the fullerenes are incorporated. Lastly, IDTBT showed a much lesser degree of ordering without much disinclination between the domains within the 2D histogram. The 4D-STEM analysis that we report here unveils new details of molecular ordering that can be used to optimize the properties of this important class of materials.

Ternary ZnS/ZnO/Graphitic Carbon Nitride Heterojunction for Photocatalytic Hydrogen Production.

Ternary ZnS/ZnO/graphitic carbon nitride (gCN) photocatalysts were prepared by coupling gCN sheets with ZnO nanorods under solvothermal conditions followed by sulfurization using Na2S. SEM and TEM analyses show that small-sized ZnS particles (ca. 7.2 nm) deposit homogeneously on the surface of ZnO/gCN nanohybrids. Photoluminescence and electrochemical impedance spectroscopy show that ZnS allows for an enhanced charge separation efficiency as well as prolonged lifetime of photogenerated charge carriers, leading to improved hydrogen photoproduction under UV light irradiation compared to ZnO/gCN. Moreover, the deposition of ZnS nanoparticles improves the photostability of the ZnS/ZnO/gCN catalyst for hydrogen production. A double Z-scheme mechanism is proposed for hydrogen photoproduction using the ZnS/ZnO/gCN heterojunction.

Design and development of large-diameter Mg-Zn-Ca bulk metallic glass for biomedical applications: A mechanical and corrosion perspective

Being amorphous, bulk metallic glasses (BMGs) exhibit superior properties compared to their crystalline alloy counterparts. Amorphous materials are preferred for their excellent mechanical and degradation behavior. Among the various elemental combinations, MgZnCa has shown the most promising results, as evidenced by the literature. However, the maximum achievable size of the metallic glasses remains a bottleneck. The current work aims to address this challenge and achieve it splendidly with a systematic methodology by developing larger diameter MgZnCa BMGs through vacuum induction casting using a specially designed copper mold. The optimal composition was formalized for glass formation of the Mg65Zn31Ca4 system using the CALPHAD technique. As a result, a 6.5 mm diameter glassy alloy was successfully obtained. The XRD and TEM analysis experiments demonstrated a perfect amorphous structure of the developed sample. The anti-corrosion properties of the as-cast glass increased, followed by enhancement in the yield strength and hardness in contrast to the properties of the human bone. Furthermore, the surface wettability analysis showed an adequate surface obtained to promote fibroblast adhesion. In conclusion, the current work represents a notable progress in the fabrication of larger-diameter MgZnCa BMG for biomedical applications, considering that the biggest diameter ever reported in the MgZnCa system was more than a decade ago.

Optimization through response surface modelling, experimental validation on development of nanocellulose for pharmaceutical applications

Nanocellulose, a promising polymer derived from lignocellulosic sources, is utilized in various applications such as paper production, water purification, wound dressing, scaffolds, biosensors, super-disintegrants, cosmetics, and drug delivery systems. The study investigates the production of optimized nanocellulose size using response surface methodology, examining the impact of factors like sulphuric acid concentration and temperature on the acid hydrolysis process. The central composite design was used to screen and adjust the design matrix with two-factor levels. The optimized size of nanocellulose was found to be 364.1 nm, with a zeta potential of −40.6, which shows long-term stability. Hence, process variables like sulphuric acid of 48.29% v/v and temperature of 39.7 °C were optimized to get the desired particle size from commercial cellulose. An Analysis of Variance (ANOVA) was applied to determine the primary parameters that have a significant impact on the particle size of nanocellulose. Thus, the obtained nanocellulose was characterized using FTIR, XRD, DLS and TEM analysis. FTIR confirms that the functional groups of cellulose are similar in nanocellulose. As the XRD illustrates, 67% of the crystallinity index in the developed nanocellulose is semicrystalline. The particle size was found within the nm size by employing the DLS method. Nanocellulose was characterized using TEM for surface morphology. Thus, obtained nanocellulose is widely used in various pharmaceutical applications like tissue engineering, cosmeceuticals, wound healing, scaffolds, aerogels, hydrogels, and controlled release of drugs.

Unravelling the mechanism of arsenic resistance and bioremediation in Stenotrophomonas maltophilia: A molecular approach

The mechanism of arsenic resistance in bacteria is under studied and still lacks a clear understanding despite of wide research work. The advanced technologies can help in analysing the arsenic bioremediating bacteria at a molecular level. With this line of idea, highly efficient arsenic bioremediating S. maltophilia was subjected to extensive analysis to understand the mechanism of arsenic resistance and bioremediation. The cell surface analysis revealed that S. maltophilia induces only slight changes in cell surface in the presence of arsenic. Whereas, TEM analysis has indicated the bioaccumulation of arsenic in S. maltophilia. Also, arsenic was found to generate ROS in a concentration dependant manner, and in response, S. maltophilia activated SOD, catalase, thioredoxin reductase etc. to manage oxidative stress which is very much crucial in managing arsenic toxicity. S. maltophilia was found to possess genes such as arsC, aoxB, aoxC and aioA. These genes are involved in arsenic reduction and oxidation. Transcriptomics and proteomics analysis have shown that S. maltophilia detoxifies arsenic by upregulating ars operon, arsH, BetB etc. which are responsible for arsenic reduction, efflux methylation, oxidation etc. A detailed molecular mechanism of arsenic bioremediation in S. maltophilia was put forth.

Exploring the therapeutic potential of microwave-assisted biosynthesized silver nanoparticles using Erica manipuliflora Salisb.: A comprehensive study on anticancer and antibacterial potentials

Silver nanoparticles (AgNPs) continue to attract interest due to their potential applications in biomedicine, especially in relation to their antibacterial and anticancer properties. In this respect, it is important to develop biosynthesis techniques that are environmentally friendly and include new sources. This is the first report on microwave-assisted green synthesis of silver nanoparticles using Erica manipuliflora Salisb. (E.m AgNPs). In this study, the anti-cancer and antibacterial activity of E.m AgNPs and E. manipuliflora extracts were evaluated. Characterization of E.m AgNPs were performed using UV–Vis spectroscopy FT-IR, XRD, SEM and TEM analyses. The UV–Vis absorption spectrum showed the characteristic peak of E.m AgNPs at λmax = 425 nm. The SEM and TEM results indicated that the nanoparticles were spherical and ranged in size from 2.45 to 9.95 nm. The antibacterial results, it was determined that E.m AgNPs (50 mg mL−1) (8.4–21.1 mm ZOI) caused more effective inhibition on both gram positive (Bacillus subtilis, Staphylococcus aureus, Enterococcus faecalis) and gram negative (Escherichia coli) bacteria compared to all plant extracts (50 mg mL−1) (8.13–17.16 mm ZOI). Among the cancer (MCF-7 and HT-29) and healthy (HaCaT and HEK-293) cell lines, E.m AgNPs exhibited the highest cytotoxicity against MCF-7 cells (IC50: 87.22 μg mL−1). The hexane extract was the most effective inhibitory extract on cell proliferation of all cell lines and showed the highest cell inhibition in MCF-7 cells (IC50: 43.06 μg mL−1). The results revealed that both E.m AgNPs and E. manipuliflora extracts showed promising antibacterial activity against pathogenic bacterial strains and had potential anticancer activity.

Soma-to-germline BMP signal is essential for Drosophila spermiogenesis

In the Drosophila testis, developing germ cells are encapsulated by somatic support cells throughout development. Soma-germline interactions are essential for successful spermiogenesis. However, it is still not fully understood what signaling events take place between the soma and the germline. In this study, we found that a Bone Morphogenetic Protein (BMP) ligand, Glass bottom boat (Gbb), secreted from somatic cyst cells (CCs), signals to differentiating germ cells to maintain proper spermiogenesis. Knockdown of Gbb in CCs or the type I BMP receptor Saxophone (Sax) in germ cells leads to a defect in sperm head bundling and decreased fertility. Our Transmission Electron Microscopy (TEM) analyses revealed that the mutant germ cells have aberrant morphology of mitochondria throughout the stages of spermiogenesis and exhibit a defect in nebenkern formation. Elongating spermatids show uncoupled nuclei and elongating mitochondrial derivatives, suggesting that improper mitochondrial development may cause sperm bundling defects. Taken together, we propose a new role of soma-derived BMP signaling, which is essential for spermiogenesis.

Improved electrochemical performance of the iron-doped NiO nanoparticles at varying calcination temperatures and examination of their supercapacitor applications

The scientific community is interested in increasing oxide electrochemical characteristics for supercapacitor applications. The present research explores the development of supercapacitor electrodes using Fe-doped NiO nanoparticles synthesised via chemical co-precipitation method with varied calcination temperatures (350, 550, and 750 °C). The key innovation of the work lies in the systematic investigation of the effects of calcination temperature on the electrochemical properties and structural characteristics of the Fe-doped NiO nanoparticles. X-ray diffraction (XRD) analysis revealed a trend of increasing crystallite size with rising temperatures, and optical studies indicated a decreasing trend in the energy band gap from 3.67 eV to 3.23 eV. Fourier transform infrared (FTIR) spectroscopy confirmed the metal-oxygen bond in the molecules. Scanning electron microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) analysis showed the mesoporous spherical morphology of the nanoparticles. Energy-dispersive X-ray spectroscopy (EDX) ensured the samples' elemental composition purity. Brunauer–Emmett–Teller (BET) shows a specific surface area of around 180.8 m2/g was obtained for Fe-doped NiO nanoparticles at 350 °C. Electrochemical tests demonstrated that the Fe-doped NiO electrodes, especially calcined at 350 °C, exhibit superior specific capacitance values (635 F/g) and impressive cycle stability with 93.29 % capacitance retention after 5000 cycles. The present demonstrates the potential of optimizing calcination temperatures to enhance the electrochemical performance and stability of Fe-doped NiO supercapacitor electrodes, marking a significant advancement in supercapacitor technology.

Enhanced ethanol gas sensing performance of Ag/SnO2 composites

A simple hydrothermal method was adopted to synthesize rectangular block-shaped SnO2 nanomaterials loaded with different amounts of Ag. The structural composition, morphology and chemical state of the nanomaterials were systematically investigated using XRD, SEM, TEM and XPS analysis. The gas sensing performance to ethanol was comprehensively evaluated by testing key parameters including gas response, optimal operating temperature, response-recovery time, and selectivity. The result demonstrates that the Ag/SnO2 composite, compared to pure SnO2, exhibits enhanced efficiency in detecting ethanol. The gas sensor fabricated by the sample Ag/SnO2-2 had a response of up to 80 for 200 ppm ethanol at 300℃. Moreover, the response time (reduced from 52 s to 29 s) and the selectivity were significantly improved. The superior gas sensing performance of Ag/SnO2 is attributed to the generation of highly active sites from Ag ion loading, accelerated electron transfer processes, and modulation of Schottky heterojunctions. In summary, this work demonstrates an effective strategy to improve the gas sensing performance of SnO2-based sensors by Ag loading.

Hydroxyapatite layer evolution on silica-based (45S10P) bioactive glass-ceramic nanoparticles doped with Zn2+ ions: Augmentation of in vitro bioactivity, antibacterial activity and textural modification for bone regeneration

Zinc-incorporated bioactive glasses (BG) and bioactive glass-ceramic (BGC) nanoparticles (BGC-NPs) represent highly adaptable, biodegradable, and bioactive materials in tissue engineering and regenerative medicine. This study delves into the synthesis, characterization and biomedical implications of Zn2+ ions-doped 45S10P spherical BGC-NPs, employing analytical techniques and in vitro assays. The resulting (Zn2++ 45S10P) BGC-NPs, prepared using a modified Strober's method, exhibited spherical morphology with excellent dispersion, as verified by TEM, FE-SEM, and DLS analyses. XRD, FTIR, and FESEM analysis revealed an augmented hydroxyapatite (HAp) layer formation with increasing zinc content. Zeta potential analysis showcased a shift from negative to positive values after immersion in simulated body fluid (SBF), indicating the bioactive potential of the developed BGC-NPs. Hemocompatibility assays indicated the biocompatibility of all BGC-NPs, demonstrating minimal hemolytic effects with incorporating Zn2+ ions below a standard threshold (<5 % lysis). Further, the migration assay revealed the potentiality of the BGC-NPs to stimulate the migration of HeLa cells. Cell viability assays employing MG-63 osteoblast-like cells highlighted enhanced cell viability over time, underscoring their non-toxic nature and potential for tissue regeneration. Antibacterial assays displayed significant inhibitory effects against Gram-negative compared to Gram-positive bacteria, underscoring their potential for anti-infection applications. Overall, the results affirm the promising prospects of Zinc incorporation into 45S10P BGC-NPs for bone tissue regeneration applications.

Elucidating capabilities of the ZIF-8-Zn metal organic framework as an adsorbent for COD removal of gas refinery wastewater under mild operating conditions

The chemical oxygen demand (COD) of gas refinery wastewater containing discharged ethanolamines and an extent of hydrocarbons was highly reduced utilizing ZIF-8-Zn metal organic framework adsorbent. The mesoporous adsorbent was initially synthesized through hydrothermal method and characterized via FT-IR, XRD, SEM, TEM, EDX, Zeta potential and BET analysis methods. The COD reduction of the wastewater was then followed with effects of pH (5.5–11.5), adsorbent concentration (0.2–2.5 g/L) and contact time (15–110 min). The response surface methodology (RSM) was employed for design of experiments, modelling and optimization of the process. Amazingly, 98.6 % COD reduction was achieved under mild operating conditions of pH 8.3, adsorbent concentration of 1.5 g/L and temperature of 293.2 K after 63 min contact time. A quadratic equation satisfactorily correlated the COD variations versus involved parameters. The data were also precisely correlated with the extended Langmuir isotherm and the mixed 1, 2-order kinetic model implying mono-layer adsorption of the multicomponent adsorbates through physisorption mechanism because of dominant electrostatic interactions. The results of thermodynamic analysis were also consistent with findings. The maximum adsorption capacity of 972.20 mg/g as well as nice reusability in five sequential cycles proved the promising capability of the adsorbent for decontaminating of the gas refinery wastewater.

Understanding preferential intergranular oxidation in alloy X-750 in 480 °C CO-CO2 environments at the nanoscale

Alloy X-750 was exposed to a 480 °C CO-CO2 reducing gas mixture at an oxygen partial pressure below the NiO dissociation pressure. Post-exposure analytical transmission electron microscopy (ATEM) analysis confirmed the occurrence of preferential intergranular oxidation (PIO) and internal oxidation which resulted in the formation of Ni nodules. Thus, reducing CO-CO2 mixtures can promote PIO in Alloy X-750, similar to Alloy 600 exposed to similar oxygen partial pressure but in H2-steam environment. In Alloy X-750, intergranular oxidation of Ti and Al were observed to occur prior to Cr oxidation, while the presence of intergranular Cr carbides hinders PIO penetration depth.

Mn doping and ZnS nanoparticles modification on Bi2MoO6 to achieve an highly-efficient photocatalyst for TC degradation

Environmental pollution presents significant challenges to both human production and daily life. Photocatalytic technology offers a promising solution for environmental remediation, and Bi2MoO6 is widely recognized as an excellent visible light photocatalyst for the degradation of organic pollutants. Nevertheless, the high recombination rate of photogenerated charge carriers in Bi2MoO6 limits the number of charge carriers available for photocatalytic reactions, resulting in reduced photocatalytic efficiency. To overcome this limitation, we designed and synthesized a composite photocatalyst (30% ZnS/Mn0.08-Bi2MoO6). Mn-doped Bi2MoO6 nanosheets (Mn-Bi2MoO6) were prepared through a simple coprecipitation method, and ZnS nanoparticles were introduced to modify the surface, forming a ZnS/Mn-Bi2MoO6 composite photocatalyst. Experimental results demonstrated that the photocatalytic degradation rate of tetracycline using the 30% ZnS/Mn0.08-Bi2MoO6 composite increased 11.1 times and 3.7 times compared with pure Bi2MoO6 and ZnS, respectively. The formation of ZnS/Mn-Bi2MoO6 heterojunction was confirmed through XRD, XPS, SEM, and TEM analyses. Furthermore, photoelectrochemical measurements, including photocurrent, EIS, and PL, indicated that Mn doping and the ZnS nanoparticle modification significantly improved the separation and transfer efficiency of photogenerated charge carriers. DFT calculations and experimental results revealed the photocatalytic mechanism of the 30% ZnS/Mn0.08-Bi2MoO6 composite. This study provides valuable theoretical and technical insights into photocatalyst modification.