Field Scanning Electron Microscopy Research Articles

On the synthesis and sintering behavior of a novel Mg-Ca alloy, Part II: Spark plasma sintering

With the growing interest in lightweight materials, magnesium and its alloys have received substantial attention for replacing existing alloys. After investigating the mechanical alloying process of Mg-Ca alloys and determining the optimum parameters for milling in part I of this study, the current research aims to examine the second step: the sintering process. This study proposes the powder metallurgy method to process Mg-Ca alloy through the spark plasma sintering technique at 420 °C under an applied pressure of 38 MPa. Samples with different additives (starch or paraffin) were sintered for various dwell times (7 and 10 min) to determine the optimal mechanical and physical properties. To study the microstructure and phase composition of the sintered alloys, X-ray diffractometer (XRD), field scanning electron microscopy (FESEM), and X-ray energy dispersive spectroscopy (EDS) were utilized. Density measurement, compression test, and micro-hardness evaluation were also conducted for the physical and mechanical feathers analysis. The results indicated that samples with a dwell time of 10 min exhibited superior mechanical properties. Additionally, the starch-containing sample outperformed the paraffin-containing sample in both physical and mechanical properties.

Vibration fatigue assessment and crack propagation mechanism of directionally solidified superalloy with film cooling holes

Film cooling represents a critical protective measure for turbine blades, yet the presence of film cooling holes (FCHs) under vibrational loads can significantly impact structural strength and integrity. This study conducts random fatigue tests on DZ125L directionally solidified superalloy specimens with FCHs. It investigates how various FCH types and vibration signal intensities influence the vibration fatigue behavior of DZ125L alloy. Characterization of vibration fatigue fracture and surface cracks of FCH specimens utilizes ultra depth of field microscopy and scanning electron microscopy. Additionally, the crack propagation mechanism for FCH specimens under random processes is proposed based on finite element stress distribution and fracture morphology. Results reveal the generation of two types of cracks, namely hole cracks and edge cracks, under vibration load in FCH specimens. The crack propagation process produces water wave-like fatigue striations. Notably, a low stress zone exists between the two dangerous holes in the multi-hole specimen, mitigating the expansion trend of hole cracks between the FCHs compared to cracks expanding towards the edges. Furthermore, two novel models, New1 and New2, are introduced to enhance the applicability of the frequency domain method for predicting the fatigue life of FCH specimens under random processes. Accuracy and error analyses of the models suggest that New2, incorporating the FCH stress concentration coefficient KT and intensity function f(ξ), exhibits superior accuracy and stability.

Led-induced deposition of Pt and Au NPs on carbon fibers: Developing a novel strategy for facile fabrication of electrocatalysts for enhanced methanol electrooxidation

In addressing the imperative of aligning materials science with sustainable development, our study introduces an innovative method for the simultaneous deposition of Pt and Au nanoparticles onto a carbon support. This research represents the pioneering application of the photodeposition process for synthesizing bimetallic nanoparticles on a carbon matrix. The comprehensive characterization of the resulting nanostructures involves various techniques, including field X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy (AFM), energy-dispersive X-ray analysis (EDX), inductively coupled plasma atomic emission spectroscopy (ICP-OES), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetric techniques. Our findings reveal that the photodeposition method produces a homogeneous AuPt nanostructure, demonstrating superior electrocatalytic activity in methanol oxidation compared to the monometallic carbon fiber_Pt (CF_Pt) catalyst. These results emphasize the effectiveness of our novel approach in fabricating electrocatalysts with exceptional performance in methanol oxidation reactions.

Effects of removing superficial layer of cartilage on the surface morphology and mechanical behavior of cartilage

Superficial cartilage defect is an important factor that causes osteoarthritis. Therefore, it is very important to investigate the influence of superficial cartilage defects on its surface morphology and mechanical properties. In this study, the knee joint cartilage samples of adult pig were prepared, which were treated by enzymolysis with chymotrypsin and physical removal with electric friction pen, respectively. Normal cartilage and surface treated cartilage were divided into five groups: control group (normal cartilage group), chymotrypsin immersion group, chymotrypsin wiping group, removal 10% group with electric friction pen, and removal 20% group with electric friction pen. The surface morphology and structure of five groups of samples were characterized by laser spectrum confocal microscopy and environmental field scanning electron microscopy, and the mechanical properties of each group of samples were evaluated by tensile tests. The results show that the surface arithmetic mean height and fracture strength of the control group were the smallest, and the fracture strain was the largest. The surface arithmetic mean height and fracture strength of the removal 20% group with electric friction pen were the largest, and the fracture strain was the smallest. The surface arithmetic mean height, fracture strength and fracture strain values of the other three groups were all between the above two groups, but the surface arithmetic mean height and fracture strength of the removal 10% group with electric friction pen, the chymotrypsin wiping group and the chymotrypsin soaking group decreased successively, and the fracture strain increased successively. In addition, we carried out a study on the elastic modulus of different groups, and the results showed that the elastic modulus of the control group was the smallest, and the elastic modulus of the removal 20% group with electric friction pen was the largest. The above study revealed that the defect of the superficial area of cartilage changed its surface morphology and structure, and reduced its mechanical properties. The research results are of great significance for the prevention and repair of cartilage injury.

PbS QDs and rGO-decorated PbS QDs induced optical properties variations on P3HT:PC61BM composite thin films

PbS QDs and PbS QDs decorated with reduced graphene (rGO) are prepared by hot-injection method using PbO and hexamethyldisilathiane (HMDS) as Pb and S sources, respectively. PbS QDs and PbS QDs:rGO are used as an addition to poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) composite. The effect of their addition on the morphological, topographical and optical properties of spin-coated P3HT:PC61BM thin films are investigated. These additions tune the films to be more homogenous and more flatness as investigated in terms of field scanning electron microscope. The topographical properties of the films are explored by atomic force microscope. The results show decreasing in the grain size and the surface roughness in P3HT:PbSQDs:PC61BM film compared to other composites films. The optical properties of the films are studied over the spectral range 200–2500 nm. On one hand, the absorption coefficient of different films is computed and the optical band gap of the films is found to decrease after addition of PbS QDs and PbS QDs:rGO. On the other hand, the refractive index of the films is explained according to the single-oscillator model to get the dispersion parameters. In addition, the lattice dielectric constant and the ratio of the free-carriers concertation to their effective mass are evaluated.

Photocatalytic degradation of acid yellow 36 with calcined titania-hydroxyapatite-CuO xerogels

Advanced oxidation processes (AOP), using semiconductor (SC) and hydroxyapatite (HA) composites, are promising due to the synergy of photocatalytic and adsorption properties. Still, dye removal efficiency of composites based on HA-SC remains low, because most of the research reported consider single SC materials. In this work, nanocrystalline xerogels of titanium oxide (TiO2) with copper oxide (CuO) and HA were synthesized by the sol-gel process. HA was obtained by the precipitation method without heat treatment and calcined in the range of 200–1000 °C. TiO2 and copper precursors were added to a sol containing HA in a 12:1 mol ratio, obtaining HA-TiO2 and HA-CuO-TiO2 nanomaterials. The xerogels were characterized by X-ray diffraction, scanning electron microscopy, emission field scanning electron microscopy and photoresponse. Their performance in the photocatalytic discoloration of an aqueous solution acid yellow dye 36 (AY36) was evaluated, using visible and UV light. The best discoloration was achieved with HA-CuO-TiO2 xerogels with HA calcined at 600 °C, showing a degradation kinetic constant of 0.24 min−1. In contrast, HA-TiO2 materials showed little or no photocatalytic activity, but strong dye adsorption/desorption. The thermal treatment of HA determines the filament-like morphology and degree of compaction of the nanomaterials, which are relevant in the crystallite size and sensitization of the SC matrix. Further studies must address the surface chemistry and rectifying properties of the best SC composite to have a more complete understanding of the mechanisms involved.

A brand new green coating technology for realizing the regulation of spherical propellant energy release process

To achieve the controllable release of energy of nitrocellulose-based propellants, this paper combines the cellulose-based nanocomposites aqueous coating (Surelease®-NC) with fluidized bed coating equipment to successfully prepare the coated spherical propellant for the first time. The effects of fluidized bed coating temperature, air velocity, flow speed and atomization pressure on the adhesion rate, coating integrity and coating uniformity of the coated spherical propellant were investigated, and the preparation of coated spherical propellant with homogeneous size and structural integrity was achieved for the first time. The microscopic morphology, chemical structure, water vapor adsorption behavior, combustion performance, and ageing resistance property of the coated spherical propellant were systematically investigated by, Fourier transforms infrared spectroscopy (FTIR), Micro confocal raman spectrometer, field scanning electron microscopy (SEM), dynamic vapor adsorption techniques, and closed bomb test, confirming the surface core-shell structure and the tightly bonded interfacial structure of coated spherical propellant. Meanwhile, the coated spherical propellant has good hygroscopic, excellent progressive burning and long storage stability.

Crystal structure, Hirshfeld surface analysis, optical properties and stability of organic-inorganic compound (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11

A novel bismuth-based zero-dimensional organic-inorganic hybrid material (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11 was synthesized by a hydrothermal method. The crystal structure, intermolecular interactions, chemical groups, chemical bond characterization, optical and thermal stability of the sample were systematically investigated by single crystal X-ray diffraction, powder X-ray diffraction, Hirshfeld surface analysis, field scanning electron microscopy, Fourier transform infrared spectrometer, Raman spectra, thermogravimetric analysis, and Ultraviolet–visible diffuse reflectance spectra. The results indicated that the (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11 crystal displayed a triclinic crystal system with a P-1 space group at room temperature with a = 8.5290(4) Å, b = 14.2484(10) Å, c = 18.9386(10) Å, α = 94.418(5) °, β = 102.260(4) °, γ = 106.595(5) °, V = 2131.9(2) Å3, Z = 2, R1 = 0.0936, wR2 = 0.1536. The compound displayed typical zero-dimensional consisting of two benzylamine organic [C6H5CH2NH3]+ cations, three dimethylamine organic [CH3CH3NH2]+ cations and a corner-sharing dimer unit [Bi2Br11]5–. Infrared and Raman vibrational study indicates the presence of [CH3CH3NH2]+. The 2D fingerprint plot of Hirshfeld surface analysis shows that H⋯Br/Br⋯H (56.8 %) and H⋯H (31.4 %) are major contributions to the intermolecular contact of (C6H5CH2NH3)2(CH3CH3NH2)3Bi2Br11. The sample presented relatively perfect thermal stability up to 240 °C and a wide band gap of about 2.75 eV. It provides some reference value for exploring organic-inorganic hybrid materials with low toxicity and high thermal stability.

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

Molten salt is usually used as the energy storage medium for solar energy heat storage pipes, and 40wt% K2SO4 + 60wt% MgSO4 is very suitable for use as a heat storage material for solar thermal power generation in tower and butterfly parabolic systems. The demand for high-temperature thermal energy storage systems has prompted research on low-cost alloys for use in high-temperature and corrosion-resistant environments. The 44% Ni-24% Cr-0.18N nitrogen-containing low-nickel flux-cored welding wire designed in this article has a corrosion resistance of up to 900 °C after welding repair, which is better than the repair ability of Inconel 625 flux-cored welding wire. Using the high-temperature static immersion corrosion method, the corrosion behavior of two deposited metals immersed in molten salt for 60 h at 900 °C was assessed. The corrosion product phase composition, corrosion morphology, and elemental distribution of the two deposited metals were systematically studied using X-ray diffraction (XRD) and a Gemini SEM 300 (Zeiss thermal field scanning electron microscope). The results showed that the corrosion weight loss of the deposited metals showed the same trend at 900 °C, with corrosion occurring slowly from 0 h to 10 h and increasing after 10 h to 60 h. It was found that 10 h was the boundary point for corrosion behavior, and the corrosion resistance of the low-nickel nitrogen-containing deposited metal is better than that of the Inconel 625 deposited metal. This was because the addition of N energy elements allowed the formation of a stable composite nitride layer to suppress corrosion.

Effect of the Cross-Section Morphology in the Antimicrobial Properties of α-Ag2WO4 Rods: An Experimental and Theoretical Study

In this work, α-Ag2WO4 particles with different cross-sections were obtained using the co-precipitation method at different synthesis temperatures. The samples were characterized by X-ray diffraction (XRD), field-scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The antimicrobial activity was analyzed using the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) methods against the Escherichia coli and Salmonella spp. gram-negative bacteria. The antimicrobial tests against Escherichia coli and Salmonella spp. indicated that concentrations of 2.5–5 mg/mL and 5 mg/mL completely inhibit its growth, respectively. The antimicrobial activity was analyzed employing band-edge positions for ROS generations and the superficial distribution of Ag+ species that contribute to antimicrobial activity. Quantum-chemical calculations were used at the DFT level to investigate the surface-dependent reactivity of α-Ag2WO4, and we demonstrated how the antimicrobial properties could be tailored by the geometry and electronic structure of the exposed surfaces, providing guidelines for the morphology design.

Pumpkin Seed Oil ‐Loaded Chitosan/Polyvinyl Alcohol Electrospun Nanofiber Scaffold for Dermal and Oral Wound Dressing

AbstractPumpkin seed oil was combined with polyvinyl alcohol (PVA) and chitosan (CS) to develop novel electrospun nanofibers that can serve as wound scaffolds. The main objective of this work is to evaluate the safety, drug release, and performance of these scaffolds for dermal and oral wound healing. The scaffolds were characterized using a field scanning electron microscope (FSEM), and Fourier transform infrared spectroscopy (FTIR). A series of tests were conducted, including the degree of swelling and degradation, in vitro drug release, antibacterial activity, and cytotoxicity in human dermal fibroblasts adult (HDFa). Wound healing activity in an excisional dermal and incisional oral wound's rat model was evaluated after 10 days. Antibacterial tests of the Pumpkin loaded CS/PVA nanofibers showed significant antibacterial activity against S. aureus and E. coli compared to negative controls. In vivo dermal wound healing showed that all treatment groups enhanced wound healing, as demonstrated by the increased wound closure percentages compared to negative control groups on 3, 5, and 10 days. Compared to other treatment groups, pumpkin‐loaded CS/PVA nanofibers significantly enhanced healing on 7 and 10 days, however, healing was delayed afterward. In oral wound healing, the qualitative Hematoxylin and Eosin (H−E) histological examination of the oral wounds treated with pumpkin‐loaded scaffolds showed an enhanced healing rate with healthy architecture compared to the wounds treated with unloaded scaffolds or untreated wounds. These results indicate that Pumpkin loaded nanofibers are promising for both dermal and oral wound healing. They offer a new safe and cheap alternative to the commercial treatments that are used for wound healing. The results also highlight the combination of using natural botanical compounds and emerging nanoscience for biomedical applications, primarily wound healing.

Ultrasonic-assisted chemical modification of a natural clinoptilolite zeolite: Enhanced ammonium adsorption rate and resistance to disturbing ions

A natural clinoptilolite zeolite was modified by ultrasonic-assisted chemicals (NaOH, FeCl3 and HCl) to improve their performance in ammonium removal from (waste) water. The obtained modified zeolites were characterized by Field Scanning Electron Microscope (FESEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD) and gas sorption techniques to understand the relation between physiochemical factors of the modified zeolites and ammonium adsorption. The highest elimination efficiency of ammonium by the natural zeolite modified by ultrasonic-assisted HCl treatment, HZU2, was ≥ 99%. However, ammonium removal by the raw natural zeolite was only 51.66%. The efficiencies of ammonium removal in the presence of various disturbing anions and cations by the HZU2 and raw zeolite were in the range of 79–93% and 15–30%, respectively. The HZU2 was reused five times presenting stable adsorption removal of ammonium. The theoretical calculations were performed to identify the key kinetics and thermodynamics parameters controlling the adsorption rate. The maximum adsorption capacity (qmax) of HZU2 obtained by the Langmuir model was about 142.85 (mg-ammonium/g-adsorbent) suggesting that the adsorption capacity of a monolayer and the relative content of alkali metal cations are suitable for the improvement of ammonium ion adsorption. The obtained thermodynamics parameters showed that the ammonium adsorption is a spontaneous and exothermic physisorption process. Consequently, we showed that ultrasonic-assisted chemical modification is a promising approach to control both textural properties and chemical composition of natural zeolites to enhance the ammonium removal from wastewater.

Fabrication and performance of phase change microcapsules with fatty acid monoglyceride based waterborne polyurethane as the shell

AbstractPolyurethane phase change microcapsules (PU‐PCMs) with high encapsulation efficiency are fabricated with ethyl palmitate as the phase change material and fatty acid monoglyceride based waterborne polyurethane as the shell. The compositions and morphologies of microcapsules are characterized by Fourier transform infrared spectrometer (FT‐IR), field scanning electron microscope (FSEM) and laser particle size analyzer. The encapsulation efficiency and phase change performances of microcapsules are investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results show that PU‐PCMs have smooth surface and spherical shape and the size of about 300 nm. TGA and DSC results show that the encapsulation efficiency of ethyl palmitate in PU‐PCMs prepared with fatty acid monoglyceride is up to 92.3%, which is much higher than that of PU‐PCMs prepared with other diols. The fatty acid monoglyceride based polyurethane prepolymer has better affinity with ethyl palmite than polyurethane prepolymer prepared with other diols, which causes the high encapsulation efficiency of phase change materials. The result of DSC show that the melting enthalpy of fatty acid monoglyceride based PU‐PCMs is 81.6 J g−1and the phase change temperature is 26.75°C. After 200 heating/cooling cycle test, the phase change temperatures and shapes of microcapsules remain unchanged, which show that the microcapsules have good phase change stability. The temperature‐regulating performance and application of the PU‐PCMs in fabricating semi‐transparent temperature‐regulating glass are conducted and investigated. Results of these investigations indicate that PU‐PCMs fabricated from fatty acid monoglyceride show promising applications in heat‐energy storage and temperature‐regulation fields.

Adsorption Characteristics of Cetirizine on Graphene Oxide

Water pollution caused by emerging contaminants such as pharmaceutical compounds is a growing problem worldwide. In this reported work, graphene oxide (GO) was directly used to remove an antihistamine drug, cetirizine. GO was prepared from graphite using a modified Hummer’s method and was characterized by UV–vis spectroscopy, Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analyzer (TGA), field scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), etc. GO was demonstrated to be a highly efficient adsorbent for removing cetirizine from an aqueous solution. The adsorption of cetirizine on GO at various pH levels showed that in acidic pH with the adsorption shows faster kinetics and complete removal of cetirizine within 10 min, followed by neutral pH, which showed relatively slower kinetics but complete removal of cetirizine. However, at basic pH, GO could not completely remove cetirizine after 24 h. At a neutral pH, GO showed maximum adsorption of 81.30 mg g−1 of cetirizine. The adsorption isotherm results showed good agreement with the Langmuir isotherm. The BET surface area analysis showed the presence of mesoporosity in GO. In addition, the BET analysis further revealed a type IV isotherm curve being followed. A plausible mechanism is also discussed in the paper. The recyclability experiment demonstrates an adsorption efficiency of 85% after four cycles. The thermodynamic study reveals that adsorption is thermodynamically less favorable at higher temperatures. Hence, the current study successfully demonstrates the use of GO as an efficient adsorbent in removing cetirizine. It also studies the various factors and interactions affecting adsorption. Thus, this study sheds light on the adsorption characteristics of cetirizine on graphene oxide.

Visual tracking of label-free microplastics in wheat seedlings and their effects on crop growth and physiology

The effects of microplastics on crop plants have attracted growing attention. However, little is known about the effects of microplastics and their extracts on the growth and physiology of wheat seedlings. In this study, hyperspectral-enhanced dark field microscopy and scanning electron microscopy were used to accurately track the accumulation of 200 nm label-free polystyrene microplastics (PS) in wheat seedlings. The PS accumulated along the root xylem cell wall and in the xylem vessel member and then moved toward to the shoots. In addition, lower concentration (≤ 5 mg·L−1) of microplastics increased root hydraulic conductivity by 80.6 %− 117.0 %. While higher PS treatment (200 mg·L−1) considerably decreased plant pigments content (chlorophyll a, b, and total chlorophyll) by 14.8 %, 19.9 %, and 17.2 %, respectively, and decreased root hydraulic conductivity by 50.7 %. Similarly, catalase activity was reduced by 17.7 % in root and 36.8 % in shoot. However, extracts from the PS solution showed no physiological effect on wheat. The result confirmed that it was the plastic particle, rather than the chemical reagents added in the microplastics, contributed to the physiological variation. These data will benefit to better understanding on the behavior of microplastics in soil plants, and to providing of convincing evidence for the effects of terrestrial microplastics.

Absorption of oenothein B nanoparticles constructed using casein phosphopeptide and chitosan

The Oenothein B (OEB) rich in eucalyptus is a kind of extremely development of prospects of antioxidant activity, but low oral bioavailability limits its application. The novel polyelectrolyte nanoparticle was designed for OEB delivery through the self-assembly of casein phosphopeptides (CPP) and natural active polysaccharides-chitosan (CS). The OEB nanoparticle with small particle size and high embedding rate were constructed to solve the problem of low oral bioavailability of OEB, and its stability as well as in vivo absorption were investigated. The storage stability analysis, digital inverted fluorescence microscopy and emission field scanning electron microscopy showed that the particle size and total amount of OEB nanoparticles did not vary significantly after 96 h of continuous storage at room temperature, and the particle size distribution was uniform, and the particles kept their integrity pH 1.2. The maximum release rate of OEB nanoparticles was only 0.72% in artificial gastric fluid and 21.77% in artificial intestinal fluid. It greatly reduces the risk of its decomposition and plays a better protective role. The results of in vivo absorption showed that OEB nanoparticle gavage mice did not detect OEB in blood and its metabolites except for OEB in gastric juice, indicating that OEB changes in vivo after release. Therefore, although OEB nanoparticles can effectively protect their decomposition in gastrointestinal fluid, it is best to achieve sustained release at the target location in order to improve the absorption and utilization effect.

Preparation of PO43--Intercalated Calcium-Aluminum Hydrotalcites via Coprecipitation Method and Its Flame-Retardant Effect on Bamboo Scrimber.

To improve the flame retardancy of bamboo scrimber, flame-retardant CaAl-PO4-LDHs were synthesized via the coprecipitation method using PO43- as the anion of an intercalated calcium-aluminum hydrotalcite in this work. The fine CaAl-PO4-LDHs were characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), cold field scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and thermogravimetry (TG). Different concentrations (1% and 2%) of CaAl-PO4-LDHs were used as flame retardants for the bamboo scrimber, and the flame retardancy of the bamboo scrimber was characterized via cone calorimetry. The results showed that CaAl-PO4-LDHs with excellent structures were successfully synthesized via the coprecipitation method in 6 h and at 120 °C. Compared with the bamboo scrimber without the flame retardant treatment, the peak heat release rate (HRR) of the bamboo scrimber treated with 1% and 2% concentrations of flame-retardant CaAl-PO4-LDHs decreased by 16.62% and 34.46%, the time taken to reach the exothermic peak was delayed by 103 s and 204 s and the Time to Ignition (TTI) was increased by 30% and 40%, respectively. Furthermore, the residual carbon of the bamboo scrimber did not change significantly, increasing by 0.8% and 2.08%, respectively. CO production decreased by 18.87% and 26.42%, respectively, and CO2 production decreased by 11.11% and 14.46%, respectively. The combined results show that the CaAl-PO4-LDHs synthesized in this work significantly improved the flame retardancy of bamboo scrimber. This work exhibited the great potential of the CaAl-PO4-LDHs, which were successfully synthesized via the coprecipitation method and applied as a flame retardant to improve the fire safety of bamboo scrimber.

Rapid synthesis of BaMoO4 :Eu3+ red phosphors using microwave irradiation.

This study synthesized BaMoO4:Eu3+ red phosphors using the microwave method. In addition, the phase composition, morphology, and luminescence properties of the red phosphors were characterized using X-ray diffraction, field-scanning electron microscopy, and photoluminescence spectroscopy. The results revealed that doping red phosphors with different concentrations of Eu3+ does not change the crystal structure of the matrix material. The BaMoO4 :Eu3+ phosphors exhibited micron-scale irregular polyhedra, which could be excited by ultraviolet light with a wavelength of 395 nm to induce red-light emission. The optimal dosage of Eu3+ was 0.08, and the chromaticity coordinates of BaMoO4 :0.08Eu3+ phosphors were (0.5869, 0.3099). White light-emitting diode (w-LED) devices manufactured by using a combination of BaMoO4 :0.08Eu3+ phosphor and commercially available phosphors exhibited good white-light emission under the excitation of an ultraviolet chip. The BaMoO4 :0.08Eu3+ red phosphors that rapidly synthesized under the microwave field are expected to be used in w-LED devices.

Inorganic polyphosphate accumulation protects a marine, filamentous cyanobacterium, Anabaena torulosa against uranium toxicity

The intricate dynamics of inorganic polyphosphate (polyP) in response to phosphorus (P) limitation and metal exposure typical of contaminated aquatic environments is poorly understood. Cyanobacteria are important primary producers in aquatic environments that are exposed to P stringency as well as metal contamination. There is a growing concern regarding migration of uranium, generated as a result of anthropogenic activities, into the aquatic environments owing to high mobility and solubility of stable aqueous complexes of uranyl ions. The polyP metabolism in cyanobacteria in context of uranium (U) exposure under P limitation has hardly been explored. In this study, we analyzed the polyP dynamics in a marine, filamentous cyanobacterium Anabaena torulosa under combination of variable phosphate concentrations (overplus and deficient) and uranyl exposure conditions typical of marine environments. Polyphosphate accumulation (polyP+) or deficient (polyP−) conditions were physiologically synthesized in the A. torulosa cultures and were ascertained by (a) toulidine blue staining followed by their visualization using bright field microscopy and (b) scanning electron microscopy in combination with energy dispersive X-ray spectroscopy (SEM/EDX). On exposure to 100 μM of uranyl carbonate at pH 7.8, it was observed that the growth of polyP+ cells under phosphate limitation was hardly affected and these cells exhibited larger amounts of uranium binding as compared to polyP− cells of A. torulosa. In contrast, the polyP− cells displayed extensive lysis when exposed to similar U exposure. Our findings suggest that polyP accumulation played an important role in conferring uranium tolerance in the marine cyanobacterium, A. torulosa. The polyP-mediated uranium tolerance and binding could serve as a suitable strategy for remediation of uranium contamination in aquatic environments.

The role of sulphur in the early production of copper red stained glass

Little is known about the production of ruby red copper stained glasses from the Medieval and Renaissance periods apart from the fact that the colour is due to the presence of small metallic copper nanoparticles and that tin, the most common reducing agent used in copper red glass production since the 19th century, is not present. In fact, very few workshops in Europe were able to make red glass in historical times, and they kept it secret, so very little is known about how it was obtained. These workshops exported the red glass throughout Europe. Recently, the presence of copper sulphide particles and the data obtained in the replication red glass following historical recipes suggested that sulphur might be the key ingredient in this process.Here, a collection of historical red glasses from these periods has been analysed using a combination of microanalytical techniques; Electron Microprobe (EM) and Field Emission and Scanning Electron Microscopy (FESEM) to verify the chemical composition and nanostructure of the glasses, Synchrotron radiation micro-X-Ray Diffraction (micro-XRD) to establish the nature of the nanocrystalline precipitates, and S, Cu and Fe K-edge micro-X-Ray Absorption Spectroscopy (micro-XAS) to determine the speciation. The data obtained show that the oxidation of S2− into S6+ in the glass is responsible for the precipitation of copper nanoparticles. The development of a sulphide-silicate partition and the presence of Fe3+ in the melt give rise to the precipitation of the high-pressure tetragonal polymorph of chalcocite (Cu2S). Differences between the Medieval and Renaissance red glass are determined.