Field Emission-scanning Microscopy Research Articles

Cu (II) Complex Stabilized on Fe3O4@SiO2 Nanoparticles: An Effective and Recoverable Catalyst for the Preparation of Chromene Derivatives

In the present research, we introduce a simple and efficient method for the synthesis of a new heterogeneous nanocatalyst including [Fe3O4@SiO2-L-Cu(II)] via immobilizing Cu (II) on the surfaces of Fe3O4@SiO2 nanoparticles (NPs). The prepared nanocatalyst was characterized by vibration sample magnetometer (VSM), EDS, X-ray diffraction (XRD), TGA, and Field emission scanning microscopy (FE-SEM) spectroscopic methods. The obtained magnetic nanocomposite showed excellent catalytic activity for the preparation of some chromene derivatives via a three-component reaction of aldehydes, 4‐hydroxycoumarin, and 2‐hydroxynaphthalene‐1,4‐dione. This synthetic procedure provides various benefits, including cost-saving, excellent yields in short reaction times (88–98%), low catalyst loading, and catalyst reusability.

Surface characteristics of AC PEO coatings fabricated on commercial Al alloys

The effect of alloying elements on coating characteristics was explored in the current work, which involved the fabrication of ceramic oxide coatings on commercial aluminium alloys (AA2024, AA6061, and AA7075) using the plasma electrolytic oxidation (PEO) process. The PEO coatings were fabricated by an AC power source with an exchange current density of about 300 mA/cm2. Field emission scanning microscopy (FESEM) was used to examine the surface, cross-sectional morphology, and alloying elements distribution. X-ray diffraction was used to investigate the phase composition. All PEO coatings were primarily composed of γ-Al2O3 and α-Al2O3 phases. As compared to PEO treated AA6061, PEO treated AA7075, and PEO treated AA2024 suppress the formation of α-Al2O3, resulting in a relatively higher fraction of γ-Al2O3, attributed to the alloying elements residing in the coatings. Because of its dense inner layer and high thickness (51 ± 1 μm), as well as its higher contact angle (114 ± 2°). PEO coated AA6061 sample exhibited superior corrosion resistance with lower icorr = 8.91(±0.24) E-6 mA/cm2 and impedance (Ω-cm2) to the order of 107 in 3.5 wt% aqueous NaCl corrosive medium. The PEO-coated AA6061 sample evinced greater hardness, scratch and wear resistance than the other samples, ascribed to its relatively higher α-Al2O3 phase, lower residual alloying elements, and thick and dense inner layer.

Hierarchically Synthesis of Nanoflakes of Molybdenum Disulfide on Electrochemically Anodized Pencil Lead for Determination Trace Amounts of Phenolic Compounds in Water Samples

Preparation coating materials is the main point in solid-phase microextraction (SPME) fiber fabrications. So, fabricating MoS2 nanoflakes on graphenized HB (hard black) pencil lead was developed. The MoS2 nanoflakes were directionally arranged on graphenized HB pencil lead and used as a fiber coating for selectively headspace microextraction of phenolic compounds. The MoS2/graphenized pencil fibers were characterized by X-ray diffraction (XRD), field emission scanning microscopy (FESEM), thermal gravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX).MoS2/graphenized pencil lead fibers indicated considerable potential due to extracting simultaneously trace amounts of some phenolic compounds in different water samples. The repeatabilities and detection limits for one fiber were between 5.5 and 7.2% and between 0.002 and 0.32 µgL−1, respectability. The purpose method was a simple, quick, stable and cheap approach.

The concentration effect of Ce3+ ions on the photoluminescence properties of the host sensitized NaMPO4-Ce3+ (M = Mg and Ca) phosphors via solid-state reaction method

A series of Ce3+ doped NaMPO4 (M = Mg and Ca) nanophosphors were prepared using the solid-state reaction route, annealed at 900 °C for 4 h (except for NaMgPO4 which was annealed at 780 °C for 4 h). In this study, the concentration effects of Ce3+ ions for x = 0.0, 0.1, 0.5, 1.0, 1.5 and 2.0 mol% were investigated for its structural and photoluminescence (PL) properties. The structural and PL properties of the NaMPO4:xCe3+ compounds were analyzed using different characterization techniques, such as X-Ray diffraction (XRD), Field Emission Scanning Microscopy (FE-SEM), UV–vis diffuse reflection spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR), PL and International Commission on Illumination (CIE) colour coordinates. XRD results confirm the prepared phosphors were crystallized into monoclinic (NaMgPO4) and orthorhombic (NaCaPO4) structures. SEM results confirm that all prepared samples were formed in the micrometer dimension range, with different sizes and shapes. Energy dispersive X-ray spectroscopy (EDS) spectra confirm the presence of chemical elements in the prepared nanophosphors. The presence of all phosphate (PO43−) and other structural groups were confirmed through FTIR measurements. UV–vis DRS measurements were used to calculate the optical band gap energy values via the Kubelka-Munk function theory. The PLE spectra of the NaMPO4:xCe3+ phosphors were measured in the 200–300 nm range by monitoring their peak at the 385 nm emission wavelength. Using 281 nm excitation wavelength, the PL spectra were measured and a high intensity emission band was found at the 385 nm wavelength (violet colour region). Using PL data of all NaMPO4:xCe3+ ion nanophosphors, the CIE colour coordinates were calculated and were found to lie in the violet colour region of the CIE colour diagram. From all the PL results, it is noticed that enhanced violet colour emissions were observed for all NaMPO4:xCe3+ compounds with increasing Ce3+ ion concentrations, implying that NaMPO4:xCe3+ phosphors are potential candidates for violet colour emitting technologies in display systems.

Novel adsorbent g‐C3N4/ZnV2O4 for efficient removal of crystal violet dye: Removal process optimization, adsorption isotherms, and kinetic modeling

Adsorption process is an effective and promising procedure for the removal of contaminations from wastewater. Nanocomposites have attracted extensive attention in the adsorption field owning to large surface/volumes ratio and large number of active sites. We aim at fabricating a novel binary g‐C3N4/ZnV2O4 nanocomposite, which can be used for removal of crystal violet dye from aqueous solution via the adsorption process. The as‐synthesized nanocomposite was well characterized by X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), field emission scanning microscope (FESEM), energy‐dispersive X‐ray (EDX), and mapping analyses. The effects of four key experimental parameters on the adsorption process, including adsorbent dosage, initial concentration of crystal violet dye, adsorption time, and solution pH, were investigated by using central composite design‐based response surface methodology. The high adsorption efficiency of 99.67% was obtained at the adsorbent dosage of 19.776 mg, initial crystal violet concentration of 20.048 ppm, contact time of 59.20 min, and pH of 8. The correlation coefficients values (R2 of 0.9969, predicted‐R2 of 0.9910, and adjusted‐R2 of 0.9948), model p value = 0.0001, and model F value = 489.78 confirm the adequacy and predictability of the proposed model. The results of adsorption kinetics demonstrate that the adsorption of crystal violet by g‐C3N4/ZnV2O4 was performed by chemical adsorption. Also, the Langmuir model was fitted effectively with the adsorption data. Furthermore, the mechanism of adsorption was explained via π–π stacking interaction, n–π stacking interaction, electrostatic attraction, coordination bonding, and hydrogen bonding.

Effects of different carriers for zinc oxide (ZnO) particles on microstructure of ZnO/layered silicate composite and aging resistance of composite modified asphalt

• ZnO/layered silicate composite with three different carriers is synthesized. • Adding EVMT can significantly weaken agglomeration effects of ZnO particles. • Introducing ZnO particles can enhance UV absorption ability of layered silicates. • Exfoliated phase structure is formed in ZnO/MMT or ZnO/EVMT modified asphalt. • EVMT and REC are preferable to form composite and improve asphalt aging resistance. With the use of nanocomposite synthesis operations, the produced zinc oxide/expanded vermiculite (ZnO/EVMT) composite, a combination of ZnO particles and EVMT, has ZnO particles of the weakened agglomeration effects and can comprehensively improve the resistance of asphalt to thermo-oxidative and ultraviolet (UV) aging. However, the effects of different carriers for ZnO particles on the microstructure of ZnO/layered silicate composite and aging resistance of the composite modified asphalt are still unknown. In this research, three ZnO carriers, montmorillonite (MMT), expanded vermiculite (EVMT) and rectorite (REC), were employed to support ZnO particles (named ZnO/MMT, ZnO/EVMT and ZnO/REC, respectively). Then, the microstructure of different ZnO/layered silicate composites was investigated by field emission scanning microscope (FESEM), X-ray diffractometer (XRD) and UV–visible spectrometer (UV–vis) tests. Finally, the effects of different carriers on the morphology, phase structure, storage stability, physical properties and aging resistance of ZnO/layered silicate composite modified asphalt were discussed. Results showed that with the unique layered structure and its integrity, the three carriers are feasible to synthesize ZnO/layered silicate composite, and ZnO particles are supported or embedded on the surface of layered silicate sheets and have weaker agglomeration effects. Except for ZnO/MMT composite, the other two composites have sufficient composition connection strength. The exfoliated phase structure is formed in the ZnO/MMT or ZnO/EVMT composite modified asphalt systems. Additionally, the three ZnO/layered silicate composites have good asphalt compatibility and storage stability in asphalt, especially for ZnO/REC composite. The addition of ZnO/layered silicate composites into asphalt slightly influences physical properties of asphalt. Incorporating ZnO/layered silicate composites, regardless of the types, into asphalt could comprehensively enhance the resistance of asphalt to thermo-oxidative and UV aging. Comparatively, EVMT and REC are preferable to support ZnO particles and generate ZnO/layered silicate composite and comprehensively improve the aging resistance of asphalt.

SYNTHESIS OF AG0NANOPARTICLES FROM EXTRACT AND ETHANOLIC AND AQUEOUS FRACTIONS OF LEAVES AND PETALS OF HIBISCUS ROSA-SINENSIS L.

The synthesis of nanoparticles from plant extracts has become an interesting line of research in recent years. The purpose of the study was the synthesis of silver nanoparticles (AgNPs) from silver nitrate, aqueous and ethanol 80% extracts obtained by ultrasound-assisted extraction, as well as fractions of chloroform, ethyl acetate and water, of flower petals and leaves of Hibiscus rosa-sinensis L. The ethanolic extract of petals of H. rosa-sinensis L. was analyzed by UHPLC-ESI-Q-Orbitrap- MS/MS identifying pelargonidin, petunidin, kaempferol, and orientin. Characterization of AgNPs by UV-Visible spectrophotometry gave a λmax at 400,631 nm and 389,411 nm for AgNPs obtained with ethanolic extract of flower petals and leaves, λmax at 402,270 nm and 391,057 nm for AgNPs of aqueous extracts of flower petals and leaves respectively. FTIR confirmed the reduction of Ag+ ions to Ag0 ions in AgNPS. Dynamic light dispersion (DLS) showed an effective diameter of the AgNPS from extracts, less than 80 nm and for AgNPs from fractions was less at 53 nm and near-zero polydispersity indices. Electron field emission scanning microscopy (FE-SEM) showed a particle size between 17 - 32 nm for AgNPs from extracts, and 15 - 26 nm for AgNPs from fractions, which showed a spherical structure. X-ray Diffraction (XRD) and Energy Dispersive Spectroscopy (EDS) analysis confirmed the elemental composition of AgNPs showing mostly silver (60.44%), oxygen (32.48%) and potassium (4.97%). This study revealed that the compounds from the extracts of Hibiscus rosa-sinensis L. are good reducing and stabilizing agents for the synthesis of silver nanoparticles, being pH 9 optimal for synthesis.

Surface Wettability of ZnO Thin Films

In this study, zinc oxide (ZnO) structured films were grown on glass substrates using a simple chemical bath deposition (CBD) method with different salt precursors. The variation of salt precursors towards the surface morphology of thin films and its wettability properties were investigated. Four types of zinc (Zn) salt used as precursors are zinc chloride (ZnCl2), zinc acetate (ZnAc2), zinc nitrate (Zn(NO3)2) and zinc sulfate (ZnSO4). The crystallinity of ZnO thin films was evaluated using X-ray diffraction (XRD), and the surface morphology was observed using field emission scanning microscopy (FESEM). Finally, the wettability was determined by contact angle (CA) measurement. It was found that ZnCl2 has the lowest CA (127.1°), while ZnSO4 exhibits the highest CA (142.3°). The Zn salts used significantly influenced the thin film surface morphology, resulting in varied wetting behaviour depending on the surface roughness.

VOC Sensors Based on Nanoparticles and Nanorods of Nickel Ferrite

Nanostructures with different morphologies have been widely used as the sensing material for the detection of volatile organic compounds (VOCs). This research investigated the response of fabricated sensors based on nickel ferrite nanorods and nanoparticles in various conditions. Both nanostructures were prepared through the hydrothermal technique. Nanorods were synthesized in the absence of any surfactant agents by annealing the as prepared precursor at 550 °C. The prepared nanostructures were characterized by field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) analysis, and UV-vis spectroscopy. By investigating the response of sensors to different VOCs, it was shown that the response to acetone is highest for each sensor. Therefore, the sensing performance of the proposed low-cost (based on glass substrate) sensors was evaluated at different temperatures and acetone concentrations (25 to 500 ppm). The measurements show that both sensors have p-type gas sensing behavior. The response value of nickel ferrite nanoparticle based sensor to 100 ppm acetone at the optimum temperature of 190 °C was 120%, while the maximum response value of 70% was obtained for the nanorod sensor at 310 °C. Due to the high response value, our sensors can also be utilized for the detection of methanol or ethanol. The higher response of the nanoparticle-based sensor is due to the lower bandgap, which increases the chemical reactivity. Long term chemical stability, repeatability, and easy recovery as well as the cheap and easy fabrication process are other advantages of the present sensors. Furthermore, the nanoparticle-based sensor can selectively detect acetone in the presence of dichloromethane, toluene, or xylene.

Magnetic and dielectric response of M-type barium hexaferrite

Barium hexaferrite (BaFe12O19) is a promising candidate for ceramics, microwave devices and numerous applications. Barium hexaferrite was synthesised via the sol-gel auto-combustion technique using glycine fuel. The X-ray diffraction technique confirmed the hexagonal structure of the particles with space group P63/mmc. The morphological analysis was performed using the field-emission scanning microscope, and the images displayed the plate-like particle formation. Transmission electron microscopy was employed to determine the average particle size of the sample, which was estimated to be 155.93 nm. The magnetic studies were taken through the vibrating sample magnetometer (VSM) at 300 K, with which the saturation magnetization (Ms), coercivity (Hc), squareness ratio (Mr/Ms), and energy product (BHmax) was calculated, and the particles were validated to be in single domain arrangement. The dielectric properties were investigated through the LCR meter. Koop and Maxwell-Wagner's model was used to interpret charge conduction and the occurrence of relaxations in the system.

Electronic Processes at the Carbon-Covered (100) Collector Tungsten Surface.

We have performed density functional VASP calculations of a pure and of a carbon-covered (100) tungsten surface under the presence of an electric field E directed away from the surface. Our aim is to answer the question of an increased penetrability of electrons at the collector side of a nanometric tunnel diode when covered by carbon atoms, a purely quantum mechanical effect related to the value of the workfunction Φ. To obtain Φ at a non-zero electric field we have extrapolated back to the electrical surface the straight line representing the linear increase in the potential energy with distance outside the metal-vacuum interface. We have found that under the presence of E the workfunction Φ = Evac − EF of the (100) pure tungsten surface has a minor dependence on E. However, the carbon-covered tungsten (100) surface workfunction Φ(C − W) has a stronger E dependence. Φ(C − W) decreases continuously with the electric field. This decrease is ΔΦ = 0.08 eV when E = 1 V/nm. This ΔΦ is explained by our calculated changes with electric field of the electronic density of both pure and carbon-covered tungsten. The observed phenomena may be relevant to other surfaces of carbon-covered tungsten and may explain the reported collector dependence of current in Scanning Field Emission Microscopy.

Exploring microstructural, optical, electrical, and DFT/TD-DFT studies of boron subphthalocyanine chloride for renewable energy applications

Microstructural, optical and electrical properties of boron subphthalocyanine chloride (B- SubPc-Cl) were investigated in order to use it in energy applications. Field emission scanning microscopy (FE-SEM) was used to investigat the surface morphology and the structural nature of B- SubPc-Cl evaporated thin films. The diffuse reflectance spectra of the as-deposited and annealed B-subPc-Cl thin films were investigated based on Kubelka-Munk (K-M) function. The optical characteristics (specular transmission and reflection) were determined from the analysis the spectrophotometric measurements. Organic/inorganic B- SubPc-Cl / n-Si heterojunction diode was successfully fabricated by means of the conventional thermal evaporation technique of B- SubPc-Cl thin film onto n-Si substrates of (110) preferred orientation. The current density–voltage (J–V) of Au/ B- SubPc-Cl / n-Si/Al heterojunction device was measured at selected temperatures. The essential electrical parameters of the device such as the series resistance, ideality factor, and barrier height were estimated from the analysis of current-voltage characteristics of heterojunction diode according to the Cheung-Cheung and Norde methods. The Complex dielectric functions such as the real and imaginary dielectric parts, dielectric modulus, and electrical conductivity of Au/ B- SubPc-Cl / n-Si/Al heterojunction device were carried out with the applied frequency in the range 20 Hz to 1 MHz and selected temperatures from 298 K to 473 K. DFT/TD-DFT calculations with B3LYP/6–31 G level of theory were used to study the optimized geometry and some important parameters of B-SubPc-Cl.

Investigation on microstructure and aging resistance of bitumen modified by zinc oxide/expanded vermiculite composite synthesized with different methods

By synthesizing zinc oxide/expanded vermiculite (ZnO/EVMT) with a modified hydrolytic precipitation method, the composite could remarkably strengthen the resistance of bitumen to thermo-oxidative and ultraviolet (UV) aging. Nonetheless, the microstructure of the composite synthesized using different methods and their effects on microstructure and aging resistance of bitumen have been insufficiently researched. Thus, a modified sol–gel (SG) method and the hydrolytic precipitation (HP) method were used to produce ZnO/EVMT composite (remarked as SG-ZnO/EVMT and HP-ZnO/EVMT respectively) in this study. Then, the effects of two synthesis methods on the microstructure of ZnO/EVMT composite and its corresponding modified bitumen were characterized with a series of experiments, including X-ray diffractometer (XRD), field emission scanning microscopy (FESEM), Fourier transform infrared spectrometer (FTIR) and ultraviolet–visible spectrometer (UV–Vis) tests. Finally, the resistance of the two ZnO/EVMT composite modified bitumen to short-term aging, long-term UV aging and long-term thermo-oxidative aging was evaluated with softening point increment and viscosity aging index. Results indicated that the two methods are feasible to synthesize ZnO/EVMT composite, and ZnO particles in HP-ZnO/EVMT have higher crystallinity and purity with the HP method. Furthermore, HP-ZnO/EVMT has a more homogeneous distribution of ZnO particles, higher UV absorption capacity and better bituminous compatibility than SG-ZnO/EVMT. With the addition of the SG-ZnO/EVMT or HP-ZnO/EVMT into bitumen, intercalated phase structures are formed in the corresponding modified bitumen. Additionally, the ZnO particle composition completely separated with EVMT composition in the SG-ZnO/EVMT modified bitumen, but HP-ZnO/EVMT composite in its corresponding modified bitumen still maintained the original characteristics. Based on the above, bitumen modified by HP-ZnO/EVMT has stronger aging resistance than that of SG-ZnO/EVMT regardless of the aging conditions. Therefore, the HP method is recommended to synthesize ZnO/EVMT composite for bitumen modification.

Synthesis of nano‐coral tungsten carbide/carbon fibers as efficient catalysts for hydrogen evolution reaction

Tungsten-carbides (WxC) are cermet materials that exhibit different unique characteristics, such as supper strength, good thermal conductivity, and electrical conductivity as well as good catalytic activity. In this study, we report a facile and scalable process using the electrospinning technique to grow a unique structure which is nano-coral tungsten carbine (W2C) on carbon fibers. The crystallinity, structure, morphology, and chemical bonding of W2C are characterized by using different techniques, including X-ray diffraction (XRD), Raman spectra, field-emission scanning microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The results confirm that the nano-coral structure of W2C is successfully prepared. Specifically, the diameter and length of nano-coral W2C are about 70 ~ 100 nm and 1 ~ 2 μm, respectively. Nano-coral W2C could be employed for electrocatalytic application including hydrogen evolution reaction (HER). Notably, nano-coral W2C shows the efficiency of electrocatalytic activity toward HER, with low Tafel slope of 79 mV.dec−1, high double-layer capacitance of 3.2 mF.cm−2, and exceptional stability under working conditions for 1000 cycles test. Therefore, this study presents an approach for the preparation of nano-coral W2C and demonstrates their potential as scalable and stable catalysts for the HER.

The effect of work function during electron spectroscopy measurements in Scanning Field-Emission Microscopy

Electron spectroscopy proves to be a handy tool in material science. Combination of electron spectroscopy and scanning probe microscopy is possible through Scanning Field Emission Microscopy (SFEM), where a metallic probe positioned close to the surface is used as an electron source. However, using this not too much technologically demanding technique, it looks like the compromise between the lateral resolution and spectroscopic clarity must be considered. Here, we demonstrate, using experimental and simulation data, that the spectroscopic information can be understood without the need to grossly deteriorate the potential spatial resolution of the microscope. We prepared a three-section sample with clean W(110), sub-monolayer Cs on W(110) and monolayer of Cs on W(110) on which electron energy loss spectra are obtained via Scanning Probe Energy Loss Spectroscopy (SPELS) measurements. To explain the detected spectra a new model describing SPELS measurements in a SFEM is developed which aids to uncover the origin of spectral features typically detected during experiments. Experimental and simulation data are in a mutual agreement and observed spectral features on different surfaces could be explained. This novel understanding of SPELS can solve the main issue previously related to this technique, and good spatial resolution can be accompanied by the understanding of the measured spectra.

Fabrication of Fe2O3 nanostructure on CNT for oxygen evolution reaction

The carbon-based composite materials prepared through green synthetic approach are attracting greater interest in electrochemical applications due to their sustainable nature. Herein, we developed Fe2O3 and Fe2O3@CNT composite materials via a green mechanochemical one-pot method. The as prepared composite materials were characterized by X-ray diffraction (XRD), energy dispersive X-Ray spectroscopy (EDS), field emission scanning microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), and X-ray photoelectron spectroscopy (XPS), respectively. Incorporating Fe2O3 nanoparticles on CNT surface tunes its electronic structure as well increases active sites and thus enhance the oxygen evolution reaction (OER) performance. As a result, the fabricated Fe2O3@CNT is a highly effective and balanced electrocatalyst that delivers superior current density (j = 10 mA cm−2) at low overpotential (η = 270 mV) for OER compared with pristine Fe2O3 (η = 290 mV) in 1 M KOH. Further, Fe2O3@CNT electrocatalyst shows high long-term durability in 1 M KOH for 100 h, fulfilling all the advantageous viable standards for OER.

Enhancement in the luminescence of green-emission from emissive surface defects of Dy3+doped ZnO nanoluminophores: A simple, mass-scale productive approach for optoelectronic devices

In the present work, dysprosium doped ZnO (DZO). nanoluminophores with different Dy concentrations are prepared by simple, one-step and mass-scale productive solid state reaction method. The structural, morphological and optical properties of synthesized Dy doped ZnO nanoluminophores have been characterized using X-ray diffraction (XRD) patterns, field emission scanning microscopy (FE-SEM), Fourier transfer infrared spectroscopy (FT-IR) and photoluminescence (PL) spectroscopy respectively. The XRD patterns of Dy-doped ZnO samples show hexagonal wurtzite structure having broadening in peaks indicates the formation of nano-sized structures. The estimated particle sizes of prepared samples are found to be in the range of ∼17–85 nm. The SEM micrographs indicate that the synthesized samples are spherical in natures and observed a change in their morphologies with Dy concentrations. FTIR results exhibit several absorption bands of ZnO:Dy nanoluminophores at room temperature. Photoluminescence spectra illustrate enhanced PL emission intensity of peaks at ∼391–397 nm in UV region and defects related green emissions ranging from ∼505–510 nm in visible region. The obtained results reveal the suitability of synthesized rare-earth (RE) doped ZnO nanoluminophores for optoelectronic devices.

A new strategy to design label-free electrochemical biosensor for ultrasensitive diagnosis of CYFRA 21–1 as a biomarker for detection of non-small cell lung cancer

Lung cancer is one of the most dangerous cancers with high mortality rate among other cancers therefore, early detection of this cancer is very important. Many studies have been reported in ways of diagnostic lung cancer early. According to reports, one of the most important biomarkers to detect lung cancer is Cytokeratin 19 fragment 21–1 (CYFRA21-1), which is significantly related to non-small cell lung cancer, in particular, squamous cell carcinoma. Thus, finding a new method for the early diagnosis of CYFRA 21–1 (DNA target probe) is essential. In the present report, we design a novel label-free electrochemical DNA-biosensor related to the signal of guanine oxidation. The proposed DNA biosensor is fabricated by a modified glassy carbon electrode (GCE) with reduced-graphene oxide (rGO), poly pyrrole (PPy), silver nanoparticles (AgNPs) and single-strand DNA (ssDNA as capture probe) GCE/rGO/PPy/AgNPs/ssDNA. The differential pulse voltammetry (DPV) and cyclic voltammetry (CV) techniques are used to verify the hybridization process between capture and target probes. Electrochemical impedance spectroscopy (EIS), energy diffraction X-ray (EDX) and field-emission scanning microscopy (FE-SEM) techniques are applied to the characterization of different modified GCE surfaces as well as X-ray diffraction (XRD) for graphene oxide synthesis. The XRD pattern of the synthesized GO that its diffraction peak appears at 10.2. The applied CV and DPV for the guanine oxidation are determined under optimal conditions. The label-free DNA biosensor showed a great result for the determination of CYFRA21-1 with a wide linear range from two consecutive linear relationships of peak current and CYFRA21-1 concentration were found (1.0 × 10−14 - 1.0 × 10−10 M, R2 = 0.9936 and 1.0 × 10−9 - 1.0 × 10−6 M, R2 = 0.9955). Proposed electrochemical biosensor displayed low detection limit (2.4 fM).

Antimicrobial activities of a combination of chlorine dioxide gas and heat against Xanthomonas campestris and Salmonella enterica on cabbage, chili pepper, and radish seeds

We developed a short-time treatment to inactivate Xanthomonas campestris and Salmonella enterica on cabbage, chili pepper, and radish seeds by a combination of chlorine dioxide (ClO2) gas and heat. ClO2 gas was evaporated from a mixed solution which contained hydrochloric acid (1 N) and sodium chlorite (100,000 ppm) (ClO2 solution). To produce ClO2 gas (3,000 ppm) in an 1.8 L airtight container, a standard curve indicating the amount of ClO2 solution and time needed to produce desired concentrations was constructed (y = 5758.3x; R2 = 0.9981). The influence of simultaneous treatment with ClO2 gas (3,000 ppm) and heat (70 °C at 85% relative humidity [RH]) on seed germination rates was determined. It was found that the germination rates of cabbage, chili pepper, and radish seeds were not significantly (P > 0.05) changed after 30, 20, and 60 min of treatment, respectively. The antimicrobial effects of the combined treatment against X. campestris and S. enterica on cabbage, chili pepper, and radish seeds were determined. When 3,000 ppm of ClO2 gas were applied at 70 °C and 85% RH for 10 min, the populations of X. campestris (initial populations: 6.2–6.4 log CFU/g) on seeds were reduced by > 4.4 log CFU/g regardless of seed type. The initial populations of S. enterica (6.3–6.5 log CFU/g) on cabbage and chili pepper seeds treated for 10 min was reduced by > 5.3 log CFU/g. However, populations on radish seeds decreased only by 2.5 log CFU/g. The lower lethality against S. enterica on radish seeds, revealed by field-emission scanning microscopy to have a rougher surface than do cabbage and chili pepper seeds, is attributed in part to inhibited access of ClO2 gas to cells in protected areas. Our findings provide useful information when developing more efficacious methods to decontaminate vegetable seeds using a combination of ClO2 gas and heat.

Synthesis of Sn doped-Bi2WO6 nanoslices for enhanced isopropanol sensing properties

Bi2WO6 has sparked a lot of attention as a gas sensor in recent years. However, in most cases, the working temperature is quite high. The Sn doped- Bi2WO6 slice-shaped nanostructure material was generated using a cost-effective one-step hydrothermal process in this study. The material was evaluated using X-ray diffraction (XRD), field emission scanning microscope (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and an energy-dispersive X-ray detector (EDX). The results show that the 5 wt% Sn doped- Bi2WO6 sensor has outstanding isopropanol gas sensitivity. The sensor's optimal operating temperature is 260 °C, and it responds to low isopropanol concentrations. The unique interfacial interaction between 2D slice-shaped nanostructures and Sn doping, which provides additional catalytic active sites on the Bi2WO6 surface and improves electrical responsiveness and gas sensitivity, is responsible for the improved gas sensitivity.