Variable Pressure Field Emission Scanning Research Articles

Synthesis of Ti<sub>3</sub>C<sub>2</sub> Mxene through <i>In Situ</i> HF and Direct HF Etching Procedures as Electrolyte Fillers in Dye-Sensitized Solar Cell

MXene is the new family of two-dimensional (2D) transition metal carbides, carbonitrides and nitrides discovered in 2011. The unique properties of 2D MXene such as excellent mechanical properties, hydrophilic surfaces and metallic conductivity made it interesting for application in electrodes of rechargeable batteries, supercapacitors, photocatalysts, catalysts, transparent conducting films, and flexible high-strength composites. The MXene can be synthesized through a selective etching process by using either in-situ HF (hydrofluoric acid) or direct HF methods. This study reports on the effect of the in-situ HF and direct HF etching procedures on the morphology of the synthesis Ti2C3 MXene using titanium aluminum carbide (Ti2AlC3) as precursor. The morphology and elements presence were evaluated by using variable pressure field emission scanning electron microscope (FESEM) and energy dispersion X-ray (EDX) spectroscopy analyses, respectively. The analysis shows that the MXene synthesized through the direct HF method was successfully delaminated compared to the in-situ HF procedures.

Surface modification and characterization of carbonaceous adsorbents for the efficient removal of oil pollutants.

In this study, the impact of different oxidizing agents on the structural integrity of activated carbon (AC) and multiwalled carbon nanotubes (MWCNTs) was studied for the removal of BTX from aqueous solution. Seven different combinations of green oxidizing agents (mild organic acids) in conjugation with NaOCl (basic oxidizing agent) were used. The modified adsorbents were analyzed by Brunauer, Emmett, and Teller (BET) surface area analyzer, Fourier transform infrared spectroscopy (FTIR), Boehm titration, Raman spectroscopy, thermal gravimetric analysis (TGA), x-ray diffraction (XRD), zeta potential, and variable pressure field emission scanning electron microscope (VPFESEM). The results suggested that the carbonaceous sorbents modified with combination of citric acid tartaric acid, malic acid and salicylic acid (CTMS-I) showed increased surface area (O-AC: 871.67 m2/g, O-MWCNTs: 336.37 m2/g) and total pore volume (O-AC: 0.59 cm3/g, O-MWCNTs: 0.04 cm3/g), with the significantly improved thermal stability. Preliminary batch adsorption experiments conducted using the present prepared O-AC and O-MWCNTs, showed an improved performance towards the adsorption of BTX, compared with other available reported adsorbents in the literature.

Investigation of green functionalization of multiwall carbon nanotubes and its application in adsorption of benzene, toluene & p-xylene from aqueous solution

The presence of benzene, toluene, and p-xylene (BTX) in an aqueous media imparts harmful effects on the ecosystem. To abate these hydrophobic contaminants, adsorption with the efficient sorbent, multiwall carbon nanotubes (MWCNTs) was selected for the present research. Since the strong oxidizing agents cause the highest degree of degradation (shortening of tubes), severely affect the structural integrity of nanotubes and ultimately result in reduced sorption capacity. Therefore, the surface of MWCNTs was modified with a new combination of green dispersants (citric acid, tartaric acid, malic acid, and salicylic acid) and characterized by surface area analyzer, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), Raman spectroscopy, x-ray diffraction (XRD), and variable pressure field emission scanning electron microscope (VPFESEM). The incorporation of oxygen-bearing complexes over the surface of nanotubes, enhanced the surface wettability of MWCNTs that offers more active sites for the sorption process. The impact of governing factors (BTX concentration, contact time, dosage of MWCNTs, temperature, and pH) was systematically studied and optimized using RSM technique. The maximum removal efficiency of oxidized MWCNTs (O-MWCNTs) was up to 99.99% for BTX. The experimental data were best fitted to the pseudo second-order model and Langmuir isotherm models. The thermodynamic study depicted that the sorption process was spontaneous and endothermic. The sorption mechanism was quantitatively evaluated by FTIR-ATR. The successful desorption and regeneration of present surface modified MWCNTs proved the recycling capacity of the modified sorbent. Conclusively, surface modified MWCNTs presented a fast and efficient removal of BTX with the highest adsorption capacity as compared to that reported in existing literature.

Impact of surface modification on adsorptive removal of BTX onto activated carbon

The wastewater from chemical industries encapsulates a variety of different volatile organic compounds. Among these hydrophobic pollutants, benzene, toluene and xylene (BTX) are the most harmful organic compounds. The abatement of these deleterious compounds is mandatory. The efficacy of surface modified activated carbon for the uptake of these carcinogenic moieties was analyzed. The commercial activated carbon was functionalized with green oxidizing agents. The structural properties of pristine AC (P-AC) and oxidized AC (O-AC) were analyzed by BET surface area analyzer, Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), and variable pressure field emission scanning electron microscope (VPFESEM). The effect of all the variables namely contact time, temperature, pH and dose was substantially analyzed and optimized. The sorption equilibrium was quickly established within 30 min. The present sorption process conforms to pseudo 2nd order kinetic model and is controlled by intra-particle diffusion. The maximum sorption capacity was computed to be 260.78 mg/g, 263.16 mg/g, 269.55 mg/g for benzene, toluene, and p-xylene respectively, outlining that Langmuir isotherm model fits the data reasonably well as compared to that of Freundlich and D-R model. Furthermore, electrostatic interaction is the plausible mechanism for sorption of BTX onto O-AC. Thus, this mode of functionalization is regarded as the contemporary protocol with high adsorption capacity towards the uptake of BTX as compared to that of previous studies reported in literature.

Optimizing use of the structural chemical analyser (variable pressure FESEM-EDX Raman spectroscopy) on micro-size complex historical paintings characterization.

The novel Structural Chemical Analyser (hyphenated Raman spectroscopy and scanning electron microscopy equipped with an X-ray detector) is gaining popularity since it allows 3-D morphological studies and elemental, molecular, structural and electronic analyses of a single complex micro-sized sample without transfer between instruments. However, its full potential remains unexploited in painting heritage where simultaneous identification of inorganic and organic materials in paintings is critically yet unresolved. Despite benefits and drawbacks shown in literature, new challenges have to be faced analysing multifaceted paint specimens. SEM-Structural Chemical Analyser systems differ since they are fabricated ad hoc by request. As configuration influences the procedure to optimize analyses, likewise analytical protocols have to be designed ad hoc. This paper deals with the optimization of the analytical procedure of a Variable Pressure Field Emission scanning electron microscopy equipped with an X-ray detector Raman spectroscopy system to analyse historical paint samples. We address essential parameters, technical challenges and limitations raised from analysing paint stratigraphies, archaeological samples and loose pigments. We show that accurate data interpretation requires comprehensive knowledge of factors affecting Raman spectra. We tackled: (i) the in-FESEM-Raman spectroscopy analytical sequence, (ii) correlations between FESEM and Structural Chemical Analyser/laser analytical position, (iii) Raman signal intensity under different VP-FESEM vacuum modes, (iv) carbon deposition on samples under FESEM low-vacuum mode, (v) crystal nature and morphology, (vi) depth of focus and (vii) surface-enhanced Raman scattering effect. We recommend careful planning of analysis strategies prior to research which, although time consuming, guarantees reliable results. The ultimate goal of this paper is to help to guide future users of a FESEM-Structural Chemical Analyser system in order to increase applications.

Investigation of Nanostructure and Magnetic Properties of Nanocrystalline NiZnCu Ferrites Synthesized by Sol-Gel Method

Nanocrystalline material of ferrites with composition Ni0.5Zn0.35Cu0.15Fe2O4was successfully synthesized by sol-gel method. This paper investigates nanostructure and magnetic properties of nanocrystaline material Ni0.5Zn0.35Cu0.15Fe2O4.Crystallite size, intensity,d-spacing and lattice parameters of material were investigated by using X-Ray diffractometer (XRD). While nanostructure, size, shape, surface morphology and topography of Ni0.5Zn0.35Cu0.15Fe2O4were examined by variable pressure field emission scanning electron microscope (VP-FESEM) SUPRA 55VP. Magnetic properties was investigated using vibrating sample magnetometer (VSM). According to thermo gravimetric analysis (TGA) result, it was found that after temperature 600oC there is no more weight loss detected and it was considered as minimum calcination temperature. XRD result shows that the samples is in single-phase cubic spinel structure. Crystallite size of the material is in range of 42.3-163.7nm. Highest intensity was 88.89 arb.units at highest calcination temperature 900oC. The value of d-spacing and FWHM decrease with increasing calcination temperature. Lattice paramenters decrease in the range of 8.4040-8.2458oA. VP-FESEM analysis shows that grain size increase by increasing calcination temperature. Grain size of the material is in the range of 47.6-506.9nm with cubic structure of the Ni0.5Zn0.35Cu0.15Fe2O4.VSM result shows that the highest value of magnetic saturation was at 152.8emu/g. The best value of coercive force (Hc) was in 31.8Oe and magnetic remanence (Mr) was in 2.6emu/g.

Electrochemical Degradation of Polycyclic Aromatic Hydrocarbons in Synthetic Solution and Produced Water Using a Ti/SnO2-Sb2O5-RuO2 Anode

AbstractElectrochemical-oxidation experiments was conducted for degradation of 16 priority polycyclic aromatic hydrocarbons (PAHs) using a dimensionally stable anode (DSA)-type Ti/SnO2-Sb2O5-RuO2 electrode. In the research reported in this paper, for electrooxidation, anode was coated with metal oxides SnO2, Sb2O5, and RuO2 in laboratory using titanium as substrate dip coating thermal decomposition method. Laboratory-scale batch reactor was used for degradation studies at pH 3, 6, and 9. Surface morphology and composition of the anode coatings were characterized by variable pressure field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Coating microstructure was analyzed by X-ray diffraction. Stability of coating was analyzed by Raman spectroscopy. Gas chromatography–mass spectrometry results revealed that almost 80, 73, and 82% PAHs removal was found without using electrolyte at pH 3, 6, and 9, respectively. While using electrolyte removal efficiency gone to ...

A comparative mechanical and biocompatibility study of poly(ε-caprolactone), hybrid poly(ε-caprolactone)–silk, and silk nanofibers by colloidal electrospinning technique for tissue engineering

Poly(ε-caprolactone) is an established polymer used in the fabrication of scaffolds for tissue engineering applications. Poly(ε-caprolactone)’s intrinsic hydrophobicity and toxicity, however, is greater than other natural polymers which limits its applicability. In this study, these problems were addressed by the modification of poly(ε-caprolactone) nanofibers with nanoparticles made from natural polymers, such as silk fibroin. Silk fibroin nanoparticles were prepared by desolvation and blended with poly(ε-caprolactone) to form a colloidal solution capable of forming nanofibers by electrospinning. Fabricated silk fibroin nanoparticles and three different nanofibers were characterized by transmission electron microscopy, variable pressure field emission scanning electron microscope, contact angle, Fourier transform infrared spectroscopy, thermogravimetric analysis, as well as an evaluation of their mechanical properties. The hybrid nanofibers incorporated with silk nanoparticles improved water absorbability compared to pure poly(ε-caprolactone) nanofibers and had much better mechanical properties than the silk fibroin nanofibers. The cytotoxicity and cell attachment tests were carried by culturing NIH 3T3 fibroblasts with the nanofibers. The hybrid nanofibers exhibited better cell viability and cell attachment than the pure poly(ε-caprolactone) nanofibers. Furthermore, the silk fibroin nanoparticles improved the water contact angle and enhanced cell interaction compared to the unmodified poly(ε-caprolactone). Based on these results, the modification of poly(ε-caprolactone) nanofibers with silk nanoparticles is a promising strategy for the improvement of poly(ε-caprolactone)-based nanofibers for future tissue engineering applications.

Facile and highly efficient approach for the fabrication of multifunctional silk nanofibers containing hydroxyapatite and silver nanoparticles

In this study, a good combination consisting of electrospun silk fibroin nanofibers incorporated with high-purity hydroxyapatite (HAp) nanoparticles (NPs) and silver NPs is introduced as antimicrobial for tissue engineering applications. The variable pressure field emission scanning electron microscope results confirmed randomly placed nanofibers are produced with highly dispersed HAp and silver NPs in nanofibers after electrospinning. The X-ray diffraction results demonstrated crystalline features of each of the three components used for electrospinning. Moreover, the TEM-EDS analysis confirmed the presence and chemical nature of each component over individual silk nanofiber. The FT-IR analyses was used confirm the different vibration modes caused due to functional groups present in silk fibroin, Hap, and silver NPs. The obtained nanofibers were checked for antimicrobial activity by using two model organisms Escherichia coli and Staphylococcus aureus. Subsequently, the antimicrobial tests have indicated that prepared nanofibers do possess good bactericidal activity. The ability of N,N-dimethylformamide and silk fibroin used to reduce silver nitrate into silver metal was evaluated using MTT assay. The nanofibers were grown in presence of NIH 3T3 fibroblasts, which revealed toxic behavior to fibroblasts at higher concentrations of silver nitrate used in this study. Furthermore, cell attachment studies on nanofibers for 3 and 12 days of incubation time were minutely observed and correlated with the results of MTT assay. The reported results confirmed the high amounts of silver nitrate can lead to toxic effects on viability of fibroblasts and had bad effect in cell attachment.

Ambient Variable Pressure Field Emission Scanning Electron Microscopy for Trichome Profiling of Plectranthus tomentosa by Secondary Electron Imaging

Glandular and nonglandular trichomes on the leaf surface of Plectranthus tomentosa were investigated by variable pressure field emission scanning electron microscopy (VP-FESEM). The segments of the plant's leaves were directly mounted without any specimen preparation, and examined at ambient temperature using a variable pressure secondary electron (SE) detector under ca. 15 Pa. Foliar trichomes maintained their shapes and structures without severe surface collapse or charging. The adaxial leaf surface was abundantly covered with different types of trichome. Nonglandular trichomes consisted of a basal cell and a long (up to ca. <TEX>$300{\mu}m$</TEX>) stalk. Meanwhile, capitate glandular trichomes had a secretory head and a short or long stalk. Peltate glandular trichomes with globose secretory heads were observed in close contact with the leaf epidermis. Spherical projections on the secretory head showed the secretion process of glandular trichomes. In addition to the trichomes, oval stomata were distributed on the abaxial leaf surface. These results suggest that ambient VP-FESEM can be used to classify the dehydration-sensitive foliar trichomes of succulent plants by SE imaging. At the FESEM resolution, this approach facilitates the rapid and detailed morphological analysis of a variety of trichomes in diverse plant taxa with reduced labor and preparation.

Local delivery of alendronate eluting chitosan scaffold can effectively increase osteoblast functions and inhibit osteoclast differentiation

The aim of this study was to investigate the effect of alendronate released from chitosan scaffolds on enhancement of osteoblast functions and inhibition of osteoclast differentiation in vitro. The surface and cell morphologies of chitosan scaffolds and alendronate-loaded chitosan scaffolds were characterized by variable pressure field emission scanning electron microscope (VP-FE-SEM). Alendronate was released in a sustained manner. For evaluating osteoblast functions in MG-63 cells, we investigated cell proliferation, alkaline phosphatase (ALP) activity, and calcium deposition. Furthermore, for evaluating inhibition of osteoclast differentiation in RAW 264.7 cells, we investigated tartrate-resistant acid phosphatase (TRAP) activity, TRAP staining, and gene expressions. The in vitro studies revealed that osteoblasts grown on alendronate-loaded chitosan scaffold showed a significant increment in cell proliferation, ALP activity, and calcium deposition as compared to those grown on chitosan scaffolds. In addition, the in vitro study showed that osteoclast differentiation in RAW 264.7 cells cultured on alendronate-loaded chitosan scaffolds was greatly inhibited as compared to those cultured on chitosan scaffolds by the results of TRAP activity, TRAP staining, and gene expressions. Taken together, alendronate-loaded chitosan scaffolds could achieve the dual functions of improvement in osteoblast functions and inhibition of osteoclast differentiation. Thus, alendronate-eluting chitosan substrates are promising materials for enhancing osteoblast functions and inhibiting osteoclast differentiation in orthopedic and dental fields.

Synthesis and characterization of silica–titania nanocomposite via a combination of sol–gel and mechanochemical process

Abstract SiO2–TiO2 nanocomposite has been produced by a combination of sol–gel and mechanochemical process. The structural and chemical properties of the nanocomposite, produced by different milling time (1, 3, 10, and 20 h at a constant speed of 200 or 350 rpm), have been investigated and compared with its calcined counterpart (950 °C for 2 h). Variable pressure field-emission scanning electron microscope and transmission electron microscope were used to investigate surface morphology of the samples. The phases and chemical bonding of samples were, respectively, characterized by X-ray diffraction and Fourier transform infrared spectroscope. Brunauer–Emmett–Teller analysis was employed to estimate the particle size of the samples. Sample prepared by the longest milling time has shown the smallest particle size (∼40 nm) with SiO2 amorphous structure mixed with crystalline anatase structure. Additional Si–O–Ti bond has been detected in the sample and the observation has been explained.