Electron Microscopy-energy Dispersive Spectroscopy Research Articles

Plant Mediated Approach for the Fabrication of Nano CuO–NiO Mixed Oxides Using Aqueous Extract of Mimusops Elengi Leaf: Green Synthesis, Characterization and Antibacterial Activity Studies

Green synthesis of nano mixed metal oxides is very important due to their applications in various fields. In the present work nano copper oxide-nickel oxide mixed oxides (CuO–NiO MOs) were synthesized using an environmentally friendly aqueous extract of Mimusops elengi leaf. The synthesized mixed metal oxides were characterized by using UV–visible spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS), and Fourier-transform infrared spectroscopy (FTIR). TEM and SEM showed that the mixed metal oxides formed as clusters and the nanoparticles had an average size of 30 nm. UV–Vis spectroscopy and FTIR spectroscopy authorized that the phytochemicals of leaf extract acted as capping agents for the synthesis of the mixed metal oxides. The extract of M. elengi leaf exhibited a significant role in the synthesis of mixed metal oxides and that also served as a reducing agent. Nano CuO–NiO MOs showed good antibacterial activity against Bacillus subtilis and Escherichia coli. Antimicrobial activity studies offered that the nano CuO–NiO MOs can be used in the medical field.

Synthesis of Magnetic Novel Hybrid Nanocomposite (Fe3O4@SiO2/Activated carbon( by a Green method and Evaluation of Its Antibacterial Potential

Inorganic antibacterial nanoagents have more advantages compared to popularly organic agents due to chemical stability, thermal resistance, immunity and long-term activity. In this study, a magnetically hybrid nanocomposite was prepared from the Nigella sativa oil waste as organic matrix in a green approach. The homogeneous distribution of core-shell Fe3O4@SiO2 nanoparticles on the activated carbon surface was carried out with a simple chemical method. Characterization of the synthesized nanocomposite was performed by different analysis techniques such as scanning electron microscopy–energy dispersive spectroscopy (EDX), scanning electron microscopy (SEM), x-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) surface area analysis. The antibacterial activities of the prepared nanoparticles against gram-positive and gram-negative bacteria were investigated and the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) values compared to imipenem as standard antibiotic. The effects of temperature, time and ratio of the activated carbon to Fe3O4@SiO2 on the MIC and MBC values of the prepared nanocomposites were investigated. The obtained results reveal the substantial role of all of these parameters in the gram-positive antibacterial properties, especially for S. agalactiae bacteria. The results show that the new proposed nanocomposite could be an alternative for an effective filter against gram-positive bacteria alongside having magnetic properties.

Analysis of magnetic vortex dissipation in Sn-segregated boundaries in Nb3Sn superconducting RF cavities

We study mechanisms of vortex nucleation in ${\mathrm{Nb}}_{3}\mathrm{Sn}$ superconducting RF (SRF) cavities using a combination of experimental, theoretical, and computational methods. Scanning transmission electron microscopy imaging and energy dispersive spectroscopy of some ${\mathrm{Nb}}_{3}\mathrm{Sn}$ cavities show Sn segregation at grain boundaries in ${\mathrm{Nb}}_{3}\mathrm{Sn}$ with Sn concentration as high as $\ensuremath{\sim}35$ at. % and widths $\ensuremath{\sim}3$ nm in chemical composition. Using ab initio calculations, we estimate the effect excess tin has on the local superconducting properties of the material. We model Sn segregation as a lowering of the local critical temperature. We then use time-dependent Ginzburg-Landau theory to understand the role of segregation on magnetic vortex nucleation. Our simulations indicate that the grain boundaries act as both nucleation sites for vortex penetration and pinning sites for vortices after nucleation. Depending on the magnitude of the applied field, vortices may remain pinned in the grain boundary or penetrate the grain itself. We estimate the superconducting losses due to vortices filling grain boundaries and compare with observed performance degradation with higher magnetic fields. We estimate that the quality factor may decrease by an order of magnitude $({10}^{10} \mathrm{to} {10}^{9})$ at typical operating fields if 0.03% of the grain boundaries actively nucleate vortices. We additionally estimate the volume that would need to be filled with vortices to match experimental observations of cavity heating.

Aluminide Thermal Barrier Coating for High Temperature Performance of MAR 247 Nickel Based Superalloy

In this paper, mechanical properties of the as-received and aluminide layer coated MAR 247 nickel based superalloy were examined through creep and fatigue tests. The aluminide layer of 20 µm was obtained through the chemical vapor deposition (CVD) process in the hydrogen protective atmosphere for 8 h at the temperature of 1040 °C and internal pressure of 150 mbar. A microstructure of the layer was characterized using the scanning electron microscopy (SEM) and X-ray Energy Dispersive Spectroscopy (EDS). It was found that aluminide coating improve the high temperature fatigue performance of MAR247 nickel based superalloy at 900 °C significantly. The coated MAR 247 nickel based superalloy was characterized by the stress amplitude response ranging from 350 MPa to 520 MPa, which is twice as large as that for the uncoated alloy.

Antimicrobial properties of multimetallic of silver compounds immobilized on active carbon and nano carbon tubes

In this paper, some bi- and tri-metallic silver compounds (Ag50Ni50/CNT, Ag90Ni10/CNT, Ag70Ni30/CNT, Pd10Co10Ag80/AC, Pd20Co30Ag50/AC, Pd30Co30Ag40/AC, (AC; active carbon) (CNT; carbon nanotube)) were synthesized with the polyol method. Antibacterial activities against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25952, Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus ATCC 29213, and antifungal activity against Candida albicans ATCC 90028 were investigated. The standard protocols were evaluated in the experimental process. The antibacterial activity assay results were correlated with the morphological characterization of the material (scanning electron microscope energy dispersive X-ray spectroscopy). It was determined that all nanomaterials (NMs) had effective antifungal activity against C. Albican fungi, but Ag70Ni30/CNT had better antifungal effects than the other NMs. Only Ag70Ni30/CNT had antibacterial activity against B. cereus and P. aeruginosa bacteria pathogens. Therefore, the relevant NMs were introduced to the literature with this feature of antifungal and antibacterial activities.

Antimicrobial Properties of Multimetallic of Silver Compounds Immobilized on Active Carbon and Nano Carbon Tubes

In this paper, some bi- and tri-metallic silver compounds (Ag50Ni50/CNT, Ag90Ni10/CNT, Ag70Ni30/CNT, Pd10Co10Ag80/AC, Pd20Co30Ag50/AC, Pd30Co30Ag40/AC, (AC; active carbon) (CNT; carbon nanotube)) were synthesized with the polyol method. Antibacterial activities against Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 25952, Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus ATCC 29213, and antifungal activity against Candida albicans ATCC 90028 were investigated. The standard protocols were evaluated in the experimental process. The antibacterial activity assay results were correlated with the morphological characterization of the material (scanning electron microscope energy dispersive X-ray spectroscopy). It was determined that all nanomaterials (NMs) had effective antifungal activity against C. Albican fungi, but Ag70Ni30/CNT had better antifungal effects than the other NMs. Only Ag70Ni30/CNT had antibacterial activity against B. cereus and P. aeruginosa bacteria pathogens. Therefore, the relevant NMs were introduced to the literature with this feature of antifungal and antibacterial activities.

INFLUENCE OF ANTITUMOR CHEMOTHERAPEUTICS ON THE STRUCTURE AND PHOSPHORUS-CALCIUM METABOLISM OF INJURED LONG TUBULAR SKELETAL BONES

The high frequency of fractures in cancer patients is due to a decrease in bone strength which is associated with bone metabolism disorders such as osteoporosis, metastatic bone disease, and pathological fractures. Anticancer chemotherapy is prescribed for long-term periods and affects bone metabolism, in particular mineralization of bony tissue. To study the structure and macronutrient composition of long tubular bones in rats under the influence of antitumor chemotherapeutics. The study involved 96 white laboratory 7 month-old male rats weighing 230 ± 10 g that were cut by a ball-shaped dental burr to obtain a 2 mm diameter perforation defect to the medullary cavity in the middle third of the femoral shaft. The animals were divided into the control (n = 24) and three experimental groups (Group I, II, and III, n = 72), which were given intraperitoneal antitumor chemotherapeutics after the cut procedure: Group I (n = 24) – doxorubicin (60 mg/m²), Group II (n = 24) – 5-fluorouracil (600 mg/m²), Group III (n = 24) – methotrexate (40 mg/m²). The therapy was repeated every 21 days throughout the experiment. On the 15th, 30th, 45th, and 60th day after the injury, the animals were sacrificed with subsequent removal of the injured long tubular bones. The samples were studied using scanning electron microscopy and X-ray energy dispersive spectroscopy. Statistical analysis of the obtained digital values was performed with the help of MX Excel XP statistical computer program using the Student's t‑test. The difference was considered significant at p ˂ 0.05. Antitumor chemotherapy slows down the formation of bone regenerate in the area of the defect and causes disorders of phosphorus-calcium metabolism in the injured bone. This is manifested by a decrease in the intensity of newly formed organic matrix mineralization in the area of the defect and a decrease in the level of calcium and phosphorus in the native bone and on its border with the regenerate. Doxorubicin and methotrexate provide the most negative impact on mineralization process among antitumor chemotherapeutic agents. The use of antitumor chemotherapeutic agents – doxorubicin, 5-fluorouracil and methotrexate – slows down the processes of reparative regeneration at all stages of recovery after injury and reduces the phosphorus-calcium metabolism of injured long tubular bones.

A Laboratory Investigation on the Way to Remove the Filter Cake Generated by Ilmenite Water-Based Drilling Fluids

The increasing demand for deeper drilling and more complicated wells fastens the way for improved drilling fluid (mud) technologies and promising additives. Several studies have shown numerous improvements in mud characteristics upon using ilmenite compared to the commonly used weighting materials. This study aims at investigating the removal of filter cake deposited by ilmenite water-based drilling fluid under harsh conditions using low-concentration (7.5 wt%) of hydrochloric acid (HCl) and chelating agent (HEDTA) to prevent iron precipitation during reaction. API filter press was used to conduct the filtration tests and generate the filter cake at a pressure ~ 300 psi and temperature ~ 250°F. Different sandstone cores of 2.5-in. diameter and 1-in. thickness were used to simulate the formation during filtration. Filtrate fluids were collected for 30 minutes as per API procedures and computerized tomography (CT) scan was used to characterize the cores with the deposited filter cakes. The filter cakes were soaked with HCl–chelate solution for six hours. Cores with the remaining filter cakes were CT scanned again. Effluent solutions resulting from the aforementioned soaking process were analyzed using inductively coupled plasma (ICP). Scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) was used to analyze the dried filter cakes and remaining residue. CT scan and SEM-EDS showed two layers of the filter cake with different densities but similar elemental composition. Using 7.5 wt% of HCl can partially remove the filter cake generated by ilmenite water-based drilling fluids. Adding the chelate showed minimal impact on the filter cake removal-efficiency; however, it helped nullify the corrosion issues during the treatment. This study provides a step forward on the way to chemically remove ilmenite-based filter cake using low acid concentration and virtually overcome corrosion issues encountered while acidizing.

Efecto del tipo de acero y su acabado superficial sobre la cinética de fosfatizado con manganeso

The objective of this work is to study the process of phosphatizing with manganese by immersion. In the literature there is not enough information on the phosphate process with manganese phosphate, hence the main contribution of the present. The methodology involves an electrochemical study, using open circuit potential techniques in order to follow the kinetics of the process. In the same way, the characterization of the coating formed on the surface of each steel used was carried out using scanning electron microscopy and X-ray energy dispersion spectroscopy. Through this technique, the time was found in which the internal layer of the coating developed on the phosphatized substrates, both on the rough and the rough sides of the steel samples. The results obtained show that the formation of the manganese phosphate coating on the steels depends both on the grain size of the steels at the beginning of the process, as well as on the surface finish to which the steel surface is subjected, resulting in an increase in the size of the crystals, and affecting the rate of disintegration and growth of the same.

The Effect of Slurry Wet Mixing Time, Thermal Treatment, and Method of Electrode Preparation on Membrane Capacitive Deionisation Performance

Capacitive deionisation (CDI) electrodes with identical composition were prepared using three deposition methods: (1) slurry infiltration by calendering (SIC), (2) ink infiltration dropwise (IID), and (3) ink deposition by spray coating (IDSC). The SIC method clearly showed favourable establishment of an electrode with superior desalination capacity. Desalination results showed that electrodes produced from slurries mixed longer than 30 min displayed a significant reduction in the maximum salt adsorption capacity, due to the agglomeration of carbon black. The electrodes were then thermally treated at 130, 250, and 350 °C. Polyvinylidene difluoride (PVDF) decomposition was observed when the electrodes were treated at temperatures higher than 180 °C. The electrodes treated at 350 °C showed contact angles of θ = 0°. The optimised electrodes showed a salt adsorption capacity value of 24.8 mg/g (130 °C). All CDI electrodes were analysed using specific surface area by N2 adsorption, contact angle measurements, conductivity by the four-point probe method and salt adsorption/desorption experiments. Selected reagents and CDI electrodes were characterised using thermogravimetric analysis coupled with mass spectrometry (TGA-MS) and differential scanning calorimetry (DSC), as well as scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS). Electrode structure and the development of the critical balance between ion- and electron- conductive pathways were found to be a function of the electrode slurry mixing procedure, slurry deposition technique and thermal treatment of the electrodes.

Effect of Simulated Annealing Conditions on Scale Formation and Neutral Electrolytic Pickling

Scale formation of AISI 304 stainless steel during annealing at temperatures between 1100 and 1200 °C under a water vapor‐containing atmosphere is studied. Characterization of the oxide scale is performed with field‐emission scanning electron microscopy–energy dispersive spectroscopy (FESEM–EDS) and glow discharge optical emission spectroscopy (GDOES) and removal of oxide scale is done via neutral electrolyte pickling. The pickling conditions are kept constant and the effect of the annealing conditions and scale properties on the pickling result are examined. The effectiveness of pickling is evaluated using analysis FESEM images taken on polished sections of pickled surfaces. Research shows that the thickness, morphology, and composition of the oxide scale are dependent on annealing temperature and time. The thicknesses of the scale formed under the established conditions vary from 0.2 to over 30 μm, and morphologies between the chromium rich oxide layer and layered scale structure formed by breakaway oxidation. The pickling response of oxide scales remains good at all annealing temperatures with the shortest exposure time.

Effect of Polymer Amendment on Hydraulic Conductivity of Bentonite in Calcium Chloride Solutions

Hydraulic conductivity of polyanionic cellulose (PAC)–amended bentonite (PB) in calcium chloride (CaCl2) solutions was investigated to access its chemical compatibility in vertical cutoff walls application. PB was synthesized by mixing conventional bentonite (CB) powder with PAC (2% dry weight). The specific gravity (Gs), liquid limit (wL), pH, swell index (SI), and cation exchange capacity (CEC) of CB and PB were measured, and hydraulic conductivities and microstructures of the PB and CB filter cakes were evaluated by performing modified fluid loss (MFL) tests and scanning electron microscopy–energy dispersive spectroscopy (SEM-EDS) analyses, respectively. The results showed that PB had higher wL, SI, and CEC but lower Gs and pH than CB; in particular, PB possessed higher SI in CaCl2 solution as compared to CB. Increase in the applied overall pressure and decrease in the CaCl2 concentration resulted in a decreased hydraulic conductivity for both PB and CB. However, the hydraulic conductivity of PB was found to be one to two orders of magnitude lower than that of CB when exposed to the same CaCl2 solutions, indicating superior chemical compatibility of PB. SEM-EDS image analyses demonstrated that polymer formed a three-dimensional net structure between bentonite particles, which could clog the intergranular pore space, resulting in a narrow and tortuous flow path for liquid and low hydraulic conductivity.

Characterization of clogging deposits in an irrigation pipeline and effect of post-aeration on clogging potential of tertiary-treated wastewater.

In Agadir, a water-scarce Moroccan region, municipal and industrial wastewater is tertiary-treated to be reused in golf courses. Wastewater reuse has been constrained by severe clogging of emitters, which caused technical and financial problems. This study aimed to perform an in-depth characterization of the treated wastewater (TWW) in relation to its susceptibility to cause clogging, and to assess the capacity of an aeration post-treatment to reduce the clogging potential. The post-treatment consisted of injecting different airflows (0-33 L/(h Lreactor) into the TWW. The structural, morphological and elemental composition of the clogging matter collected in the irrigation pipeline was characterized using scanning electron microscopy, scanning transmission electron microscopy, X-ray diffraction and X-ray energy dispersive spectroscopy. The 15-day aeration post-treatment at 16.5 L/(h Lreactor) presented the best cost-benefit ratio. Organic matter was totally degraded. Calcium was reduced by 9%, bicarbonates by 54%. The analysis of the deposits induced by the aeration post-treatment revealed a relevant decrease of the major constituents of the clogging deposits found in the irrigation pipeline. The results show the effectiveness of post-aeration in biodegrading residual organic matter and precipitating several salts, thus reducing the clogging potential.

Bonding Mechanisms in Cold Spray: Influence of Surface Oxidation During Powder Storage

Cold spray is a solid-state process in which solid particles are subjected to severe plastic deformation to form a coating. The effect of naturally occurring oxides on bonding in the cold spray was investigated in this work. Deposition characteristics of copper powder with different surface oxide thicknesses on steel substrate were examined using a local pull-off test. This enables the investigation of individual particle/substrate interfaces. X-ray photoelectron spectroscopy was used to study thoroughly the powder surface chemistry and the oxide thickness as a function of exposure time. This study revealed that the oxide film thickness grew from 6 nm for the as-received powder to 11.6 nm after 2 months of exposure to atmospheric conditions. Scanning electron microscopy and x-ray energy dispersive spectroscopy were used to characterize the particle/substrate interfacial bonding. Adhesion test results show that the bond strength is highly influenced by the surface oxide thickness. Different bonding behaviors and a drop in coating deposition efficiency were observed as the oxide thickness increased. Finite element simulations supplemented our understanding of the particle adhesion dynamics as the oxide film thickness increases. They were also used to study the surface oxide cleanup and bonding mechanism for particles with different oxide film thicknesses.

Effect of glycine as a complex agent on the surface and corrosion properties of Ni-P and Ni-P/Al2O3 electroless coating

Purpose The ability to produce a uniform composition, high corrosion resistance with a hard coating layer during the electroless coating techniques are mainly based on the plating bath composition. The complexing agent is one of the most important components that control the coating layer properties. This paper aims to investigate the effect of the glycine as a complex agent on the surface and corrosion properties of Ni-P and Ni-P/Al2O3 electroless coating. Design/methodology/approach In this study, the effect of glycine as a complexing agent on the final surface and corrosion properties of the Ni-P and Ni-P/Al2O3 coatings has been investigated. The surface morphology and composition of the coated samples were investigated by scanning electron microscope (SEM) imaging and energy dispersive x-ray spectroscopy (EDS) analysis. Linear polarization scan and electrochemical impedance spectroscopy techniques were used to investigate the corrosion properties of the coating layer. Findings The results clarify that, glycine has a remarkable effect on the porosity content of Ni-P and Ni-P/Al2O3. It was found that increasing of glycine concentration results in higher porosity content in the coating layers. Also, the porosity in the coating layers minimizes the protectability of the coating against corrosion. The results also show that adding nano-alumina (Al2O3) to the coating path has improved the corrosion properties by decreasing the porosity in the coating layer. The scanning electron microscope (SEM) images showed that the concentration of glycine affects the content and distribution of alumina nanoparticles embedded in the coating layer. Also, it was observed that using a high concentration of glycine (0.4 M glycine), the alumina tends to agglomerate and the final alumina content in the coating was decreased. Originality/value The present study reveals that the quality of the final coating plays a major role in the corrosion performance of the steel substrate. The coating quality can by improve remarkably by optimization of the complexing agent used in the plating bath, to minimize the porosity involve in the coating layer.

Photo-mediated optimized synthesis of silver nanoparticles using the extracts of outer shell fibre of Cocos nucifera L. fruit and detection of its antioxidant, cytotoxicity and antibacterial potential.

Presently, photo-mediated optimized synthesis of SNPs (CS-AgNPs) was carried out with the help of aqueous extracts of coconut (Cocos nucifera) outer shell fibre. Green synthesis of CS-AgNPs was undertaken under laboratory light conditions and characterized by several standard techniques such as UV–visible spectrophotometer (UV–Vis), X-ray diffraction pattern (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) images and energy dispersive spectroscopy (EDX). UV–Vis spectra displayed a surface plasmon resonance peak at 468 nm equivalent to CS-AgNPs, and the FT-IR spectra confirmed the association of biological molecules from the extract in the synthesis process. The SEM image data confirmed the round and circular nature of CS-AgNPs. The EDX data presented the elemental configuration with a solid peak at 3 KeV that matched with the Ag. The synthesized CS-AgNPs exhibited substantial cytotoxicity potential against the HepG2 cells with (effective concentration (IC50) value of 15.28 µg/ml along with robust antioxidant potential, with respect to its 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging (IC50 of 96.39 µg/ml) and reducing assay (IC0.5 of 209.96 µg/ml). The CS-AgNPs demonstrated encouraging antimicrobial potential against four different pathogenic bacteria and one Candida sp. with inhibition zone diameter ranged between 8.87 and 13.07 mm. Overall, the existing investigation suggested that CS-AgNPs can be an attractive, cost-effective, and environment-friendly candidate for its possible uses in the food, cosmetics, and therapeutic fields.

Synthesis and Characterization of Sodium Silicate Produced from Corncobs as a Heterogeneous Catalyst in Biodiesel Production

In this study, silica derived from corncobs impregnated with sodium hydroxide to obtain sodium silicate was calcined, prepared, and employed as a solid base catalyst for the conversion of oils to biodiesel. The catalyst was characterized by X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope Energy Dispersive X-Ray Spectroscopy (SEM-EDS), and Brunauer-Emmet-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods. Gas Chromatography-Mass Spectrometry (GC-MS) was used to characterize the biodiesel products. The optimum catalyst conditions were calcination temperature of 400 °C for 2 h, catalyst loading of 2%, and methanol: oil molar ratio of 12:1 at 60 °C for 60 min, that resulted in a yield of 79.49%. The final product conforms to the selected biodiesel fuel properties of European standard (EN14214) specifications. Calcined corncob-derived sodium silicate showed high potential for use as a low-cost, high-performance, simple-to-prepare solid catalyst for biodiesel synthesis.

Mineralogical Setting of Precious Metals at the Assarel Porphyry Copper-Gold Deposit, Bulgaria, as Supporting Information for the Development of New Drill Core 3D XCT-XRF Scanning Technology

A petrographic investigation of ore samples from the Assarel porphyry copper deposit in the Srednogorie metallogenic zone (Bulgaria) constrains the setting and character of precious metals (Au, Ag, PGE) and related minerals within the deposit. This work supports renewed interest in understanding the deportment of precious metals and provides mineralogical knowledge during the testing and validation of novel drill core 3D X-ray computed tomography–X-ray fluorescence (XCT-XRF) scanning technology being developed as part of the X-MINE project. Scanning electron microscopy–energy dispersive spectrometry (SEM-EDS) results indicate precious metals occur in their native state (Au, Ag), as sulfides (Ag), sulfosalts (Au), tellurides (Ag, Pd), and selenides (Ag), and typically form micron-sized inclusions in pyrite and chalcopyrite or are disseminated in the groundmass of the rock. Preservation of early Fe oxide–chalcopyrite ± bornite assemblage as relics in the more dominant pyrite-chalcopyrite mineralization assemblage supports mineral disequilibrium relationships and multi-stage mineralization events. Several rare minerals (e.g., merenskyite, acanthite, sorosite, tetra-auricupride, auricupride, greenokite, bismuthinite, nagyagite, native Ni) are reported for the first time at Assarel and highlight the mineralogical diversity of the ore. The occurrence of precious metals and related minerals at Assarel attest to a complex hydrothermal system that underwent progressive physicochemical changes during the evolution of the mineralizing system (e.g., redox conditions, fluid chemistry).

The altar wall paintings of the catholicon "The Nativity of the Virgin", Rila Monastery, Bulgaria: Identification of the painting materials by means of vibrational spectroscopic techniques complemented by EDX, XRD and TGA analysis.

The purpose of the present study is to deepen our knowledge about the painting materials and technology characteristics of iconography during the Bulgarian National Revival. Our efforts have focused on studying the murals in the catholicon (main church) "The Nativity of the Virgin" of the Rila Monastery, which is one of Bulgarian leading historical monuments. A series of micro samples from the altar mural paintings were analyzed by a combination of attenuated total reflectance Fourier transform infrared (ATR-FTIR), micro-Raman spectroscopy, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Optical microscopy (OM). The data analysis showed that the painter's palette is made up of nine mineral pigments: smalt, chrome yellow, emerald green, vermilion, red lead, green earths, yellow ochre, sienna and calcite. The impression of rich colorful palette was achieved by using various pigment mixtures. The presence of egg binder in many paint samples suggested that the murals were executed by the traditional egg tempera technique, with the only exception of the smalt paint of the background where carbohydrate glue is present as binder.

Enhanced detection of volatile organic compounds (VOCs) by caffeine modified carbon nanotube junctions

Detection of vapor phase analytes and gas molecules is primarily essential for numerous applications including medical diagnostic, environmental monitoring, chemical threat detection, food quality control, and chemical warfare agents. Here, we developed Caffeine functionalized carbon nanotubes (CNTs) random network based vapor quantum resistive sensors (vQRSs) for volatile organic compounds (VOCs) detection. The localized transmission electron microscopy (TEM) image and energy dispersive X-ray spectroscopy (EDS) confirm migration of caffeine to CNT–CNT junction (CNTj). We have recorded more than one order of magnitude higher sensitivity and unique selectivity towards​ selective VOCs (e.g., acetone, toluene, ethanol, methanol, etc.) with short response time (few seconds) for caffeine modified CNT junction (Caf-CNTj) vQRSs. Molecular dynamics (MD) calculations suggest that the sensitivity of the sensor is diffusion limited, with an advective contribution for ethanol. The designed Caf-CNTj sensors can potentially be important candidate to be a part of electronic nose used for various application such as breath analysis and food quality monitoring.