Field-emission Electron Microscopy Research Articles

Synthesis of High Surface Area Boron Nitride Nanosheets for the Removal of Methylene Blue and Rhodamine B Dyes from Contaminated Water.

In this study, we report the synthesis and characterization of boron nitride nanosheets (BNNSs), and their application as an adsorbent to remove the cationic dyes methylene blue (MB) and rhodamine B (RhB) from contaminated water. The synthesized adsorbent was characterized by high-resolution transmission electron microscopy (HR-TEM), field emission electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR) and nitrogen adsorption-desorption isotherm. Detailed experiments and analysis were performed on various molar ratios of boron and nitrogen precursors (1:5 to 1:48) to achieve maximize specific surface area of BNNSs. Among all, the samples synthesized with boric acid and urea (1:30) dissolved in water and methanol produced maximum specific surface area (1801.9 m² g-1). Further, the adsorption study was performed in batches by investigating various adsorption parameters such as effect of pH, contact time, adsorbent dose and adsorption isotherm. The pH study revealed that optimum value was found to be at pH 8. It was found through the kinetic study that pseudo-second-order (PSO) kinetic model was followed by the adsorbent during the adsorption of both the dyes. Further, the adsorption isotherm data well fitted with Langmuir isotherm model. The maximum adsorption capacities of MB and RhB were found to be 333.33 and 312.5 mg g-1, respectively. This demonstrates the potential of BNNSs as novel adsorbent for treatment of dye-contaminated water.

Comparison of characteristics of Bi2Te3 and Bi2Te2.7Se0.3 thermoelectric materials synthesized by hydrothermal process

In this research, a simple approach based on hydrothermal method was developed for the synthesis of high purity Bi2Te2.7Se0.3 polyhedral nanoflakes and Bi2Te3 spherical nanoparticles. The synthesized Bi2Te3 and Bi2Te2.7Se0.3 nanopowders were characterized by X-ray diffraction, Fourier transform infrared spectrometry, field emission electron microscopy, photoluminescence (PL) and ultraviolet–visible near-infrared spectroscopy. The results showed that the produced powders (Bi2Te3 and Bi2Te2.7Se0.3) exhibit no chemical impurity formed during hydrothermal synthesis process. Besides, the ternary Bi2Te2.7Se0.3 alloy showed less oxide bond versus the Bi2Te3 alloy. The results showed that Bi2Te2.7Se0.3 powders possess a uniform nano-flake shape with an average size of 48 nm along with bandgap energy of 0.6 eV. Moreover, Bi2Te3 powders were characterized with a uniform spherical shape and an average size of 43 nm along with bandgap energy of 0.9 eV. The Bi2Te2.7Se0.3 nanoplate powders exhibited a favorable bandgap and lower PL intensity due to the larger particle size compared with the spherical Bi2Te3 nanopowders. In conclusion, the obvious specifications of Bi2Te3-based materials were improved by the incorporation of selenium using a hydrothermal procedure. It is strongly believed that this synthesis approach and characterization methods will be important for the development of thermoelectric performance and applications of these groups of materials, such as sensors, laser diode, cooling system, fiber-optic systems.

Graphene derivative based high dielectric constant polymer composite electrodes for supercapacitors

Abstract Graphene oxide (GO) and reduced graphene oxide (rGO) based polyvinylidene fluoride (PVDF) flexible composites were prepared using GO and rGO fillers in PVDF matrix by solution casting method. These composites were characterized with X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, Impedance analyzer (dielectric constant) and Field emission electron microscopy (FE-SEM). The dielectric constants at 1 MHz frequency for PVDF, 5%GO/PVDF and 5% rGO/PVDF composites were obtained 3.68, 12.20 & 30.32 respectively, ascribed to Maxwell-Wagner-Sillars (MWS) polarization mechanism and the exchange coupling at the surface and interface. According to MWS polarization charges could be accumulated at the interface when an external field was acted on composites due to heterogeneous response of GO, rGO and PVDF attributed alternate of electrode materials for superacapacitors.

Effect of surface acidity of SiO2 nanoparticles on thermal stability of polymer solutions for application in EOR processes

This study has a primary objective the evaluation of the effect of surface acidity of silica nanoparticles for mitigation of time-dependent thermal degradation of polymer solutions of partially hydrolyzed polyacrylamide (HPAM), for employment in chemical enhanced oil recovery (EOR) processes. For this, silica (SiO2) nanoparticles were modified on the surface with NaOH (SiO2B) and HCl (SiO2A). The obtained nanoparticles were characterized through field emission electron microscopy, surface area, total acidity by NH3-Temperature programmed desorption, dynamic light scattering (DLS), and electrophoretic light scattering (ELS) for zeta potential. The nanoparticle-polymer interaction was analyzed by adsorption isotherms. Also, the rheological behavior of HPAM solutions at 500 mg L−1 with and without 3000 mg L−1 of raw and functionalized nanoparticles was evaluated at a temperature of 70 °C through steady-state rheometry and dynamic oscillatory measurements at the day zero and after 15 days of aging. Also, coreflooding tests were carried out at conditions of pressure and temperature of a reservoir of interest using the aged polymer solutions with and without nanoparticles. The results show that the polymer adsorption decreases in the order SiO2B > SiO2>SiO2A, indicating that polymer uptake is higher as the surface acidity of nanoparticles decreases. SiO2B nanoparticles showed greater interactions between the functional groups on the surface and the HPAM in solution, forming a polymer network more resistant to degradation. A lower viscosity reduction with the addition of the unmodified SiO2 nanoparticles and SiO2B up to 49.6% and 22.9% was observed, respectively, and is closely related to the adsorption affinity and nanoparticles’ surface acidity. Coreflooding tests also indicated that, there is lower polymer retention in the porous medium when nanoparticles are included. In addition, the aged polymer solution with nanoparticles promotes an additional oil recovery of about 30% regarding polymer without nanoparticles.

Taxonomy and toxicity of a bloom-forming Ostreopsis species (Dinophyceae, Gonyaulacales) in Tahiti island (South Pacific Ocean): one step further towards resolving the identity of O. siamensis.

Among dinoflagellates responsible for benthic harmful algal blooms, the genus Ostreopsis primarily described from tropical areas has been increasingly reported from subtropical and temperate areas worldwide. Several species of this toxigenic genus produce analogs of palytoxin, thus representing a major threat to human and environmental health. The taxonomy of several species needs to be clarified as it was based mostly on morphological descriptions leading in some cases to ambiguous interpretations and misidentifications. The present study aims at reporting a benthic bloom that occurred in April 2019 in Tahiti island, French Polynesia. A complete taxonomic investigation of the blooming Ostreopsis species was realized using light, epifluorescence and field emission electron microscopy and phylogenetic analyses inferred from LSU rDNA and ITS–5.8S rDNA regions. Toxicity of a natural sample and strains isolated from the bloom was assessed using both neuroblastoma cell-based assay and LC-MS/MS analyses. Morphological observations showed that cells were round to oval, large, 58.0–82.5 µm deep (dorso-ventral length) and 45.7–61.2 µm wide. The cingulum was conspicuously undulated, forming a ‘V’ in ventral view. Thecal plates possessed large pores in depressions, with a collar rim. Detailed observation also revealed the presence of small thecal pores invisible in LM. Phylogenetic analyses were congruent and all sequences clustered within the genotype Ostreopsis sp. 6, in a subclade closely related to sequences from the Gulf of Thailand and Malaysia. No toxicity was found on the field sample but all the strains isolated from the bloom were found to be cytotoxic and produced ostreocin D, a lower amount of ostreocins A and B and putatively other compounds. Phylogenetic data demonstrate the presence of this species in the Gulf of Thailand, at the type locality of O. siamensis, and morphological data are congruent with the original description and support this identification.

An experimental investigation on the sulfur and nitrogen co-doping and oxidation of prepared graphene by electrochemical exfoliation of pencil graphite rods

In this research, the electrochemical exfoliation of pencil rods was carried out for the synthesis of graphene sheets in different mixtures of H2SO4 and HNO3 solution. Influence of different volume ratios of H2SO4: HNO3 at a low concentration (0.6 M) on the morphology and structure of prepared graphene sheets was investigated by field emission electron microscopy (FESEM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Raman spectroscopy and atomic force microscopy (AFM) analyses. Results indicated that the mixtures of few-layered graphene, multi-layered graphene, and graphene oxide were achieved by applying an anodic voltage of +10 V. However, the number of layers, degree of oxidation and defect density of the synthesized powders were different. By increasing the volume ratio of HNO3 in electrolytes, the degree of exfoliation of graphite decreased. On the other hand, the highest degree of oxidation was achieved for the prepared graphene by electrochemical method in the mixture of H2SO4: HNO3 with 1:1 ratio. EDS results of the prepared powders demonstrated the occurrence of nitrogen and sulfur co-doping of graphene sheets.

Effect of surface patterning using femtosecond laser on micromechanical and structural properties of micromechanical sensors

A femtosecond laser can be used to fabricate microstructures on a silicon microcantilever surface with high precession and minimal sidewall defects. The aim of this study is to investigate the effect of the creation of microgrooves and sub-microgrooves on the resonance frequency, quality factor, and spring constant of a silicon microcantilever. A single pass of a femtosecond laser with a wavelength of 1026 nm was used to fabricate microgrooves on the microcantilever surface. Different numbers of microgrooves were fabricated on each microcantilever using the femtosecond laser micromachining technique. The separation distance between the center of the two microgrooves was 7 μm. The microstructure of the fabricated microgrooves was investigated through field emission electron microscopy. The resonance frequency increased with the number of microgrooves, but the quality factor of the patterned microcantilever was higher than that of the unpatterned microcantilever. The spring constant increased with the number of microgrooves, increasing from 18.96 to 38.04 mN/m for microcantilevers with 1 and 7 microgrooves, respectively.

Microwave absorption characteristics of carbon foam decorated with BaFe12O19 and Ni0.5Co0.5Fe2O4 magnetic composite in X-band frequency

BaFe12O19/Ni0.5Co0.5Fe2O4 (H/S) as magnetic composite powder and subsequently carbon foam decorated with BaFe12O19/Ni0.5Co0.5Fe2O4 (H/S@CF) nanocomposites were prepared using one-step sol–gel and dip coating methods, respectively. Phase structures, morphology, magnetic and electromagnetic properties were evaluated using X-ray diffraction (XRD), Field emission electron microscopy (FESEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) respectively. According to the results, through XRD analysis, presence of pure barium hexaferrite, spinel ferrite and carbon are revealed. Rietveld refinement was also done to evaluate the phases in the prepared nanocomposites. FESEM analysis depicted the honey comb like structure of H/S@CF sample. Based on electromagnetic measurements, smooth and continuous behavior for permittivity and permeability of H/S@CF composite revealed strong interfacial polarization and migration of charges in the direction of field. The minimum reflection loss of H/S@CF nanocomposite was − 45 dB at a matching frequency of 12.4 GHz, and the effective bandwidth under − 10 dB was 4 GHz with a thickness of 2 mm. The excellent microwave absorption performances of H/S@CF nanocomposite may be ascribed because of the less dielectric, magnetic losses and high dielectric properties. H/S@CF nanocomposite is expected to be a suitable candidate for aeronautic and aerospace fields because of low cost, lightweight and better microwave absorbing material.

Synergetic photocatalytic effect of high purity ZnO pod shaped nanostructures with H2O2 on methylene blue dye degradation

Zinc oxide (ZnO) nanostructures were successfully synthesized by thermal oxidation of Zn from different sources in the air atmosphere. We aimed to explore the influence of oxidation temperatures and the type of the Zn sources (powder and sheet) on the morphology and physical-chemical properties of the synthesized ZnO nanostructures. X-ray diffraction pattern and elemental analysis results proved that the applied one-step vapor phase transport synthesis method resulted in the synthesis of high purity ZnO nanostructures. Morphological observations using field emission electron microscopy demonstrated two kinds of morphologies, mostly including tetrapods and a trace amount of multi-pod shaped ZnO nanostructures, synthesized from powder and sheet Zn sources, respectively. Attained ZnO nanostructures were investigated for photocatalytic degradation of the methylene blue dye in aqueous solution under UV-light irradiation. Results showed that the multi-pod shaped (∼93%) sample had slightly better photodegradation efficiency than the tetrapod shaped (∼91%) ZnO nanostructures at 150 min of irradiation time. By adding 20 μl of H2O2 as an electron scavenger agent, the photodegradation process was accelerated and the reaction constant rate showed 218% and 173% improvement for multi-pod and tetrapod shaped nanostructured ZnO particles, respectively. Almost the same photocatalytic efficiency results were attained after 30 min of irradiation with the addition of H2O2 for multi-pod (∼92%) and tetrapod (∼90%) shaped ZnO nanostructures. Photocatalytic reusability of multi-pod shaped ZnO nanostructures was evaluated in the presence of H2O2 and efficiency was only 4% lower than in the first cycle. Finally, the presented results showed the synergetic effect of H2O2 as an electron scavenger agent on the photocatalytic activity of pod shaped ZnO nanostructures due to suppressing the recombination process of electron-hole pairs.

Comparison of smear layer removal by MTAD, TetraClean, QMix, NaOCL, coconut water, and saline as irrigating solutions in primary teeth: An in vitro study

Background: The purpose of the endodontic treatment is to achieve thorough debridement of the root canal irregularities in the canal systems, narrow isthmi, and apical deltas prevent complete debridement by mechanical instrumentation alone. Thus, a variety of irrigants along with the mechanical instrumentation are required to clean and shape the root canals before obturation. Aims and Objectives: The aim and objective of the study was to compare and evaluate the smear layer removal efficacy of different final irrigants from the coronal, middle, and apical third of the root canals of primary teeth using field-emission scanning electron microscopy. Materials and Methods: Sixty therapeutically extracted human single-rooted primary teeth were prepared by step-back technique. Prepared teeth were randomly divided into six groups (n = 10): MTAD (Group I), TetraClean (Group II), QMix (Group III), 0.9% normal saline (Group IV), coconut water (Group V), and 5.25% NaOCl (GroupVI). After irrigation with final irrigants, the teeth were evaluated and assessed for the amount smear layer present under a field-emission scanning electron microscope using a score system criteria by Rome et al. Data obtained were analyzed using the Pearson's Chi-square test and McNemar–Bowker test. Results and Conclusions: Among the six irrigants QMix 2 in 1 showed the best smear layer removal efficacy, followed by 5.25% NaOCl, TetraClean, MTAD, coconut water, and the least efficacy was for normal saline.

Super-hydrophobic Fe3O4@SiO2@MPS nanoparticles for oil remediation: The influence of pH and concentration on clustering phenomenon and oil sorption

This study was focused on the optimization of synthesis conditions of iron oxide nanoparticles coated by silica and 3- (trimethoxysilyl) propyl methacrylate, Fe3O4@SiO2@MPS, as an oil absorbent with magnetic properties. The change in the structure and its effect on the oil absorption capacity of these core-shell magnetic nanoparticles (MNP) were investigated upon pH and reactant concentration variations. An excellent oil sorption capacity of about 48.5 times of MNPs weight was reached and this work clearly demonstrated the relationship between the absorption capacity and hydrodynamic diameter of magnetic clusters formed in two different crude oils. The particles were fully characterized by field emission electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), vibrating sample magnetometer (VSM), energy dispersive X-ray spectroscopy(EDS), Brunauer Emmett Teller (BET) analysis and water contact angle in order to compare the morphology, magnetic, structural properties and specific surface area of the nanoparticles.

Evolution of ZnO flowerets from dealloying of Cu-Zn alloy powder

The synthesis of flower-like morphology of ZnO nanorods labelled as 'ZnO flowerets' via a novel approach comprising of dealloying of mechanically alloyed powder particles of Cu-Zn of mean size 2.9 ± 0.6 μm is reported in the present work. The mechanical alloying of the powder blend was performed in a planetary ball mill. Subsequently, the dealloying was performed in a basic solution of NaOH. The optimization of type of basic solution, pH of the solution, dose of alloy powder and time of dealloying was performed to find the best possible process parameters for dealloying. The ZnO flowerets were characterized by X-ray diffraction (XRD) and field emission electron microscope (FE-SEM) attached with energy dispersive spectrophotometer (EDS). The aspect ratio of ZnO nanorods and the EDS atomic ratio of Zn/Cu in the ZnO flowerets were measured to be ∼ 11 (length = ∼520 nm and width = 48 nm) and ∼ 1.2, respectively. The results of inductively coupled plasma mass spectroscopy (ICP-MS) showed the concentration of Cu and Zn ions to be 25 and 1200 ppm, respectively, in NaOH solution after experimentation for 24 h. It also indicated the predominant dissolution of Zn relative to Cu from the alloyed powder.

Highly sensitive and selective determination of p-nitrophenol at an interpenetrating networks structure of self-assembled rod-like lanthanum hydroxide-oxidized multi-walled carbon nanotubes nanocomposite.

In this study, a novel electrochemical sensor based on self-assembled rod-like lanthanum hydroxide-oxidized multi-walled carbon nanotubes (La(OH)3-OxMWCNTs) nanocomposite was developed for sensitive determination of p-nitrophenol (p-NP). The La(OH)3-OxMWCNTs nanocomposite with an interpenetrating networks structure was characterized by field emission electron microscope (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, Raman spectra and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were performed to study the electrochemical behaviors of La(OH)3-OxMWCNTs modified glassy carbon electrode (La(OH)3-OxMWCNTs/GCE). The La(OH)3-OxMWCNTs/GCE was used for sensitive determination of p-NP by CV and linear sweep voltammetry (LSV). Under the optimum conditions, the peak currents of LSV versus the concentrations of p-NP in the range 1.0-30.0μmolL-1 showed a good linear relationship (R2=0.9971), and the limit of detection (LOD) was calculated to be 0.27μmolL-1 (signal-to-noise ratio of 3, S/N=3). The recoveries of p-NP in real samples of industrial wastewater and Xiangjiang water at La(OH)3-OxMWCNTs/GCE were in the range of 95.62-110.75% with relative standard deviation (RSD) in the range of 1.65-3.85%. The intra-day and inter-day precisions were estimated to be less than 2.76% (n= 5), indicating that La(OH)3-OxMWCNTs/GCE possessed highly stability. In addition, La(OH)3-OxMWCNTs/GCE sensor showed good anti-interference ability for determination of p-NP in aqueous mixtures containing high concentrations of inorganic and organic interferents, and a decrease of oxidation peak currents by less than 3.57% relative to the initial levels indicated it possessed excellent selectivity. Therefore, La(OH)3-OxMWCNTs/GCE could be used as a fast, selective and sensitive electrochemical sensor platform for the selective determination and quantification of aqueous p-NP.

Compatibilization and Characterization of Polylactide and Biopolyethylene Binary Blends by Non-Reactive and Reactive Compatibilization Approaches.

In this study, different compatibilizing agents were used to analyze their influence on immiscible blends of polylactide (PLA) and biobased high-density polyethylene (bioPE) 80/20 (wt/wt). The compatibilizing agents used were polyethylene vinyl acetate (EVA) with a content of 33% of vinyl acetate, polyvinyl alcohol (PVA), and dicumyl peroxide (DPC). The influence of each compatibilizing agent on the mechanical, thermal, and microstructural properties of the PLA-bioPE blend was studied using different microscopic techniques (i.e., field emission electron microscopy (FESEM), transmission electron microscopy (TEM), and atomic force microscopy with PeakForce quantitative nanomechanical mapping (AFM-QNM)). Compatibilized PLA-bioPE blends showed an improvement in the ductile properties, with EVA being the compatibilizer that provided the highest elongation at break and the highest impact-absorbed energy (Charpy test). In addition, it was observed by means of the different microscopic techniques that the typical droplet-like structure is maintained, but the use of compatibilizers decreases the dimensions of the dispersed droplets, leading to improved interfacial adhesion, being more pronounced in the case of the EVA compatibilizer. Furthermore, the incorporation of the compatibilizers caused a very marked decrease in the crystallinity of the immiscible PLA-bioPE blend.

Highly efficient photocatalytic performance of dye-sensitized K-doped ZnO nanotapers synthesized by a facile one-step electrochemical method for quantitative hydrogen generation

The different morphologies of K-doped ZnO nanostructures were successfully synthesized by a facile one-step electrochemical method using control of the current density. Field emission electron microscope images showed various morphologies and aspect ratios due to change in the value of applied current densities. Photoluminescence and UV-visible spectrometers showed that change in current densities leads in different level of defects and band gap shifting. The photocurrent responses reveal that the photocurrent intensity increases as K-doped ZnO surface morphology tends to taper on the application of 0.5 mA cm−2 current density. The maximum degradation rate of methylene blue was attained to be 99.3% within the 60 min using K-doped ZnO nanotapers which was much higher than the values found in previous studies. The highest photocatalytic H2 evolution activities were obtained in the applied current density of 0.5 mA cm−2 in comparison to other samples. These results indicate that doping and controllable morphology are effective and facile methods to improve the photocatalytic features of ZnO by boosting the absorption of light.

Enhancement of the Electrochemical Properties of an Open-Pore Graphite Foam with Electrochemically Reduced Graphene Oxide and Alternating Current Dispersed Platinum Particles

This paper aimed to improve the electrochemical activity of a pitch-derived open-pore graphite foam (GF) by an electrochemical coating of reduced graphene oxide (RGO) and platinum particles without significantly affecting its 3D-structure. RGO was synthesized using cyclic voltammetry (CV) from a 3 g L−1 GO and 0.1 M LiClO4 solution. For the electrodeposition of Pt particles, an alternating current method based on electrochemical impedance spectroscopy (EIS) was used. A sinusoidal voltage from a fixed potential Ei was varied following a selected amplitude (ΔEac = ± 0.35 V) in a frequency range of 8 Hz ≤ fi ≤ 10Hz, where i = 500. This method proved its efficiency when compared to the traditional CV by obtaining more highly electroactive coatings in less synthesis time. For samples’ characterization, physical measures included permeability, pressure drop, and nitrogen adsorption isotherms. The electrochemical characterization was performed by CV. The surface morphology and chemical composition were examined using field emission electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX), respectively. RGO improved the electron transfer rate constant of GF, and a more homogeneous coating distribution of reduced size Pt particles was obtained.

Effect of Temperature on Morphology, Phase Transformations and Thermal Expansions of Coal Fly Ash Cenospheres

Cenospheres are small, hard-shelled hollow spheres with high silica and alumina content. These micron-sized aluminosilicate hollow spheres constitute only a small percentage of the coal fly ash (CFA) obtained from the coal combustion processes. In this study, cenospheres were separated from CFA obtained from a coal-fired power plant located in Kapar, Malaysia. The cenospheres were heated at 1000, 1200 and 1400 °C to study the changes in morphologies, compositions, phase formation and thermal expansion. The sintering temperatures were selected based on the differential scanning calorimetry (DSC) curve results. X-ray diffractometry (XRD), field emission electron microscopy (FESEM), energy dispersive spectroscopy (EDS) as well as thermogravimetry and differential scanning calorimetry analysis (TG–DSC) were used for the characterization study. The study found that the cenospheres have excellent weight stability but are thermally unstable as a result of crystallization and melting. The phase ordering process and devitrification of the amorphous aluminosilicate glass phase at high temperatures lead to the increment and enrichment of the mullite phase in cenospheres. It is suggested that a preheating treatment at 1100 °C could be used to enhance the mechanical properties and thermally stabilize the cenospheres, which make it more suitable for use as a pore-forming agent in ceramics.

Electrochemical synthesis of fluorinated graphene nanoplatelets in electrolytes containing hydrofluoric acid and TiO2 nanoparticles

In this study, the simultaneous fluorination and exfoliation of graphite by the electrochemical method was studied. The anodic exfoliation of graphite rods in two electrolytes of 10 wt% hydrofluoric acid (HF) and 10 wt% HF + 2.5 g/l TiO2 was carried out by applying various voltages (2.5, 5 and 10 V). The morphological and structural analysis of prepared powders were studied using field emission electron microscopy (FESEM) images, energy dispersive spectroscopy (EDS), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. Results indicated that by applying higher voltages, the graphene sheets with a lower number of layers were formed. FTIR spectroscopy and EDS analysis showed the successful fluorination of the graphene with the electrochemical process in both electrolytes. The Raman spectroscopy findings showed that the defect density as well as the degree of fluorination of graphene were decreased by increasing the applied voltages. The related mechanisms for fluorination and exfoliation of graphite were presented in this research.

Polysulfone-iron acetate/polyamide nanocomposite membrane for oil-water separation

Polysulfone (PSF) membranes are widely used for water filtration, however, their hydrophobic nature limits their application in oil-water separation. Herein, we report on the preparation of hydrophilic, high-flux and mechanically-stable PSF-based nanofiber membrane. The membrane was fabricated via electrospinning of a PSF solution containing iron acetate powder followed by deposition of a polyamide (PA) layer using interfacial polymerization on both sides of the membrane. This treatment resulted in switching membrane from being hydrophobic (contact angle = 100 ± 7°) to be highly hydrophilic (contact angle = 37 ± 5°) and the membrane porosity reached up to 83 ± 7 % after the deposition of the PA layer. Results from field emission electron microscopy with energy dispersive spectroscopy (FESEM-EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) showed the unique nanofiber characteristics with uniform iron distributions. The new membranes have also improved mechanical properties as indicated by Young's modulus and mechanical strength. In addition, the membranes efficiently separated water from oil-water mixtures and the water flux of the modified membrane was three times higher than the unmodified PSF membrane in this study and also higher than previously reported membranes.

Red-emitting improvement of CaAlSiN3:Eu2+ phosphor-in-glass: Insight into the effect of atmospheric pressure preparation on photoluminescence properties and thermal degradation

The red-emitting phosphor-in-glass (PiG)s have been successfully prepared by a facile one-step co-sintering method on the basis of ultra-low melting Sn-P-F-O glass and CaAlSiN3: Eu2+ red phosphors synthesized under atmospheric-pressure (denoted as CASN-AP) and high-pressure (denoted as CASN-HP), respectively. The crystal structure, particle morphology, photoluminescence (PL) properties and surface states of the phosphors were investigated detail by X-ray powder diffraction (XRD), field emission electron microscopy (FESEM), fluorescence spectroscopy and X-ray photoelectron spectroscopy (XPS). Under excitation of blue light (460 nm), CASN-AP phosphor with red emission at 659 nm shows a higher luminescent intensity by 23 % than that of CASN-HP phosphor. Moreover, a shorter photoluminescence lifetime and red shift of 9 nm for emission peak can be also found for the CASN-APphosphor, which is ascribed to the increased Si-N bonds and surface Si/N ratio (1.86) demonstrated by the XPS analysis. Besides, the quantum yield and thermal degradation of both phosphors have been investigated. CASN-AP phosphor exhibits higher emission intensity because of its more emitting photons, but a lower quantum yields than CASN-HP phosphor due to its more absorbed photons. Based on the above, the low-temperature melting process for Sn-P-F-O glass does not damage the phosphor and the enhanced (≥35%) red-emitting CASN-AP PiG will be a promising candidate for essential red component in high quality white LEDs.