Energy Dispersive X-ray Reflectivity Research Articles

Photocatalytic degradation of metronidazole and oxytetracycline by novel l-Arginine (C, N codoped)-TiO2/g-C3N4: RSM optimization, photodegradation mechanism, biodegradability evaluation

Removal of Metronidazole (MNZ) and Oxytetracycline (OTC) from wastewater by the prepared (C, N codoped)-TiO2/g-C3N4 (Graphitic carbon nitride) was examined. l-Arginine (C, N codoped)-TiO2 and l-Arginine (C, N codoped)-TiO2/g-C3N4 photocatalysts were successfully synthesized through the sol-gel method, and optimal ratio of l-arginine:TiO2, as well as l-arginine/TiO2:g-C3N4, was determined by a kinetic study of photodegradation process. The maximum photocatalytic removal rate (0.062 min−1 for MNZ removal) was observed using 1% l-Arginine-TiO2/g-C3N4 (1:1) under visible light illumination, 2.2 and 12.4 times greater than those of 1% l-Arginine-TiO2 and pure TiO2, respectively. l-Arginine (1%)-TiO2/g-C3N4 (1:1) (co-doped-TCN) was investigated using X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), Photo-luminescence (PL), and Differential Reflectance Spectroscopy (DRS) as the best-performing photocatalyst. Response surface methodology (RSM) was used to study the effect of co-doped-TCN dosage (0.5–1.0 g/L), pH of simulated wastewater (4–10), initial concentration of MNZ and OTC (50–100 mg/L), and irradiation time (30–90 min for MNZ and 20–40 min for OTC) on removal efficiency of the antibiotics. Also, their optimum values were determined by RSM. The treated pharmaceutical wastewater showed high biodegradability features with 5-day biological oxygen demand/chemical oxygen demand (BOD5/COD) of 0.51 and 0.46 after 40 and 100 min reaction for OTC and MNZ, respectively. The order of reactive species responsible for the photodegradation of pollutants was •O2─> •OH > h+>1O2. The effect of inorganic anions showed that all anions decreased the removal efficiency of both antibiotics in order of NO3─> Cl─ >SO42─>HPO42─ >HCO3─ for MNZ and NO3─> SO42─ > Cl─ >HPO42─ >HCO3─ for OTC. Also, introducing different oxidants improved the photocatalytic removal efficiency with the order of H2O2>K2S2O8> KBrO3.

Multi-Technique Approach for Work Function Exploration of Sc2O3 Thin Films.

Thin films based on scandium oxide (Sc2O3) were deposited on silicon substrates to investigate the thickness effect on the reduction of work function. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), energy dispersive X-ray reflectivity (EDXR), atomic force microscopy (AFM), and ultraviolet photoelectron spectroscopy (UPS) measurements were performed on the films deposited by electron-beam evaporation with different nominal thicknesses (in the range of 2-50 nm) and in multi-layered mixed structures with barium fluoride (BaF2) films. The obtained results indicate that non-continuous films are required to minimize the work function (down to 2.7 eV at room temperature), thanks to the formation of surface dipole effects between crystalline islands and substrates, even if the stoichiometry is far from the ideal one (Sc/O = 0.38). Finally, the presence of BaF2 in multi-layered films is not beneficial for a further reduction in the work function.

Nanomechanical property evaluation of tungsten thin film via frequency-domain photoacoustic microscopy

This study investigates the reduction in nanomechanical properties of a tungsten (W) thin film measured using a laser ultrasonic technique. A 96 nm thick W film was prepared via direct-current magnetron sputtering and inspected using scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray diffraction, and X-ray reflectivity techniques. Moreover, frequency-domain photoacoustic microscopy was employed to evaluate the Young's modulus (EW) of W. The velocity dispersion of a surface acoustic wave excited by an intensity-modulated laser was measured and curve-fitted using a computational finite element model to estimate EW. In addition, a high-frequency microcantilever resonance test was performed to verify the results. The results show that EW of the film is 45.3% lower than that of the macroscopic property because of the predominant β-W phase. The Young's moduli obtained from the two different techniques agree well with each other, with a relative error of 13.3%. The hardness-to-EW ratio obtained using a nanoindenter was calculated to be 0.025±0.004.

Passivation properties of HfO2-SiO2 mixed metal oxide thin films with low reflectivity on silicon substrates for semiconductor devices

HfO2-SiO2 mixed oxide-based thin films were introduced in this work, and their passivation and anti-reflection properties were examined by using carrier lifetime, x-ray diffraction, scanning electron microscope, energy dispersive x-ray analysis, reflectance, and Fourier transform infrared measurements. The HfO2-SiO2 mixed oxide solutions were prepared with different composition ratios, and the thin films were formed on p-type CZ-Si substrates using the spin-coating technique. Annealing of the samples was carried out in ambient air at different temperatures after optimizing the solution ratio. When annealed at 600 and 700°C, the average reflectance of the samples was observed to be around 15% in the spectral range of 300-1000 nm, with a minimum reflectance point lying in the visible range. The effective carrier lifetimes increased up to 32 μs after annealing at 600°C compared to the initial lifetime of around 2 μs. Annealing at higher temperatures significantly decreased the carrier lifetimes (4.5 and 0.6 μs for 700 and 800°C, respectively). The results of this study revealed that the HfO2-SiO2 mixed oxide films can provide a good passivation effect in addition to an effective anti-reflection property depending on the annealing temperature.

In-Situ Energy Dispersive X-ray Reflectivity Applied to Polyoxometalate Films: An Approach to Morphology and Interface Stability Issues in Organic Photovoltaics

Organic solar cells, characterized by a symmetrical regular layered structure, are very promising systems for developing green, low cost, and flexible solar energy conversion devices. Despite the efficiencies being appealing (over 17%), the technological transfer is still limited by the low durability. Several processes, in bulk and at interface, are responsible. The quick downgrading of the performance is due to a combination of physical and chemical degradations. These phenomena induce instability and a drop of performance in working conditions. Close monitoring of these processes is mandatory to understand the degradation pathways upon device operation. Here, an unconventional approach based on Energy Dispersive X-ray Reflectivity (ED-XRR) performed in-situ is used to address the role of Wells–Dawson polyoxometalate (K6-P2W18O62, hereafter K6-P2W18) as hole transporting layer in organic photovoltaics. The results demonstrate that K6-P2W18 thin films, showing ideal bulk and interface properties and superior optical/morphological stability upon prolonged illumination, are attractive candidates for the interface of durable OPV devices.

Association between the incidence of acute respiratory diseases in children and ambient concentrations of SO2, PM10 and chemical elements in fine particles

The aim of this study consists of investigating the effects of the SO2, PM10, inorganic chemical elements and black carbon (BC) present in fine particulates on the acute outcomes of respiratory diseases in children up to 12 years of age living in Brazilian urban area in the southern hemisphere during the winter (2013) and summer (2013–2014) months. SO2 and PM10 concentration data were obtained from six air quality monitoring stations spatially distributed in the area. PM2.5 samples were collected at the same locations with a MiniVol sampler over a 24-h period on alternating days. The PM2.5 components were analysed using the energy dispersive X-ray fluorescence and reflectance techniques. Hospital care and admission events due to acute respiratory diseases (n = 8,987) of the coded groups JJ00-JJ99 of the International Code of Diseases (ICD-10) were obtained from three hospitals (one public and two private hospitals). To quantify the association of acute respiratory disease events with pollutant concentrations, a generalized additive model (GAM) with a Poisson distribution was applied. The results showed a greater risk of acute respiratory events due to exposure to SO2 with a relative risk of 1.28 (95% CI: 1.22–1.34) and to PM10 with a risk of 1.14 (95% CI: 1.09–1.20) on the day of exposure (lag 0). The chemical constituents present in the fine particles with the highest risk for acute respiratory diseases were Si with a risk of 1.22 (95% CI: 1.15–1.29), S with a risk of 1.09 (95% CI: 1.06–1.12), Ti with a risk of 1.09 (95% CI: 1.01–1.17), BC with a risk of 1.07 (95% CI: 1.03–1.11), Se with a risk of 1.03 (95% CI: 0.96–1.10) and Ni with a risk of 1.03 (95% CI: 0.96–1.10).

High photocatalytic performance of 3D porous-structured TiO2@natural rubber hybrid sheet on the removal of indigo carmine dye in water

Due to the high efficiency of photocatalytic process for the environmental treatments, titanium dioxide (TiO2) is a popular used as photocatalyst material. However, the practical uses of TiO2 in powder form have some drawbacks as well as the difficult reusability. In this work, 3D porous-structured TiO2@natural rubber (TNR) hybrid sheets with high photocatalytic performance were presented. TNR hybrid sheets prepared by a facile and low-cost method, which is based on the mixing of natural rubber (NR) latex (60% high ammonia) and ammoniacal TiO2 (P25) suspension, followed by vacuum filtration through a sintered glass template to make a 3D porous network structure on the surface of the sheets. The obtained TNR sheet samples were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD) and reflection Fourier transformed infrared spectroscopy (FT-IR) techniques. The results showed that the surface morphologies of TNR hybrid sheets appeared as porous-structured which had high roughness and with various tiny pores on the surface. The photocatalytic properties of the prepared TNR hybrid sheets were tested using indigo carmine (IC) dye under UV light irradiation. It was found that the highest photodegradation efficiency was achieved with the TNR_5 wt% hybrid sheet sample. Compared with the sheets reported in previous works, the TNR sheet shows higher efficiencies than those sheets due to its higher amount of TiO2 particles at the surface, more porous structure with high rough surface, and abundance of tiny pores on the TNR sheet surface. Moreover, the recyclability and stability of TNR sheet indicated that upon using 10 cycles (remains 98% efficiency), in which the stability of the sheet surface well-confirmed by SEM and XRD techniques, as well. From above the study, this 3D porous-structured TNR hybrid sheet could be a new alternative strategy for the water or wastewater treatment in industry concerning with the easy use, recovery, reusability and stability of the photocatalysts.

Conductivity via Thermally Induced Gap States in a Polyoxometalate Thin Layer

We report a study of alpha-[P2W18O62]6-, Wells-Dawson polyoxometalate layers deposited on ITO coated glass substrates. A variety of techniques has been used including atomic force microscopy for surface topography characterization, current mapping and current-voltage characteristics, X-ray photoemission spectroscopy for chemical analysis, UV-visible photoemission spectroscopy for determination of band line-ups and energy dispersive X-ray reflectivity for determination of layer thicknesses and scattering length densities. The conditions of film deposition and subsequent thermal annealing strongly affect the film characteristics. In particular, we show that nanostriped films a few tens of nm thick can be obtained in a reproducible manner and that such structuring is accompanied by the appearance of gap-states and by a switch from an insulating to a conductive state. Current-voltage characteristics demonstrate that highly ordered films of K 6 [P 2 W 18 O 62 ] allow electron flow only from ITO to [P2W18O62]6-, thus showing a rectifying effect. Finally, we integrate the POM layer 2 into an organic photovoltaic device and show the conduction through it thanks to favorable band alignment between ITO, the gap states and the active photovoltaic layers.

Bioinspired Synthesis of Carbon Dots/g-C3N4 Nanocomposites for Photocatalytic Application

This study reports a fast and green preparative strategy to synthesize water soluble and fluorescent carbon quantum dots (CQDs) through hydrothermal method by using low cost organic waste of human fingernails as the carbon precursor for the first time. The coupling of CQD with pure carbon nitride (g-C3N4) was further explored to enhance the latter’s performance in photocatalysis of 2,4-dicholorophenol (2,4-DCP), a toxic and recalcitrant compound mostly released from industrial effluent. Such coupling overcame the weakness of pure g-C3N4 in photocatalysis process by broadening its visible light absorption and promoting the charge separation. As a result, the removal rate of CQD/ g-C3N4(10) was up to 71.53%, which was approximately 1.5 times higher than that of pure g-C3N4 under sunlight irradiation. The morphological structure, optical properties and chemical compositions of CQDs/g-C3N4 composites were characterized using various spectroscopic techniques including field emission scanning electron microscopy (FESEM), Energy Dispersive X-Ray (EDX) and Ultraviolet-visible diffuse reflectance spectra (UV-DRS).

Plasma cleaning of ITER edge Thomson scattering mock-up mirror in the EAST tokamak

First mirrors are the key element of all optical and laser diagnostics in ITER. Facing the plasma directly, the surface of the first mirrors could be sputtered by energetic particles or deposited with contaminants eroded from the first wall (tungsten and beryllium), which would result in the degradation of the reflectivity. The impurity deposits emphasize the necessity of the first mirror in situ cleaning for ITER. The mock-up first mirror system for ITER edge Thomson scattering diagnostics has been cleaned in EAST for the first time in a tokamak using radio frequency capacitively coupled plasma. The cleaning properties, namely the removal of contaminants and homogeneity of cleaning were investigated with molybdenum mirror insets (25 mm diameter) located at five positions over the mock-up plate (center to edge) on which 10 nm of aluminum oxide, used as beryllium proxy, were deposited. The cleaning efficiency was evaluated using energy dispersive x-ray spectroscopy, reflectivity measurements and x-ray photoelectron spectroscopy. Using argon or neon plasma without magnetic field in the laboratory and with a 1.7 T magnetic field in the EAST tokamak, the aluminum oxide films were homogeneously removed. The full recovery of the mirrors’ reflectivity was attained after cleaning in EAST with the magnetic field, and the cleaning efficiency was about 40 times higher than that without the magnetic field. All these results are promising for the plasma cleaning baseline scenario of ITER.

Microstructure of periodic metallic magnetic multilayer systems

The results of a complex microstructural analysis of periodic metallic magnetic multilayer systems (MLS) by Scanning/Transmission Electron Microscopy, Energy Dispersive X-ray microanalysis and Resonant X-ray Reflectivity (RXRR) are presented. The crystal structure of MLS based on Cr-Gd-Cr-Fe layers with different Cr layer thicknesses was revealed. The use of RXRR at the Cr and Fe absorption edges significantly improves the optical contrast between correspondent layers. A significant Cr diffusion was detected in adjacent layers. After that diffusion, Fe and Gd layers transform to the solid solution of Cr in Fe and in Gd respectively, without changing their crystal structure. Such Cr behavior may affect both the exchange coupling between Fe and Gd magnetic moments and the structural parameters of Gd layers, thus influencing drastically the magnetic moment.

Sonophotocatalytic degradation of trypan blue and vesuvine dyes in the presence of blue light active photocatalyst of Ag3PO4/Bi2S3-HKUST-1-MOF: Central composite optimization and synergistic effect study

An efficient simultaneous sonophotocatalytic degradation of trypan blue (TB) and vesuvine (VS) using Ag3PO4/Bi2S3-HKUST-1-MOF as a novel visible light active photocatalyst was carried out successfully in a continuous flow-loop reactor equipped to blue LED light. Ag3PO4/Bi2S3-HKUST-1-MOF with activation ability under blue light illumination was synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), photoluminescence (PL) and diffuse reflectance spectra (DRS). The effect of operational parameters such as the initial TB and VS concentration (5–45mg/L), flow rate (30–110mL/min), irradiation and sonication time (10–30min), pH (3–11) and photocatalyst dosage (0.15–0.35g/L) has been investigated and optimized using central composite design (CCD) combined with desirability function (DF). Maximum sonophotodegradation percentage (98.44% and 99.36% for TB and VS, respectively) was found at optimum condition set as: 25mg/L of each dye, 70mL/min of solution flow rate, 25min of irradiation and sonication time, pH 6 and 0.25g/L of photocatalyst dosage. At optimum conditions, synergistic index value was obtained 2.53 that indicated the hybrid systems including ultrasound irradiation and photocatalysis have higher efficiency compared with sum of the individual processes.

Controlled fluoridation of amorphous carbon films deposited at reactive plasma conditions

Abstract A study of the correlations between plasma parameters, gas ratios, and deposited amorphous carbon film properties is presented. The injection of a C4F8/Ar/N2 mixture of gases was successfully used in an inductively coupled plasma system for the preparation of amorphous carbon films with different fluoride doping at room-temperature, using silicon as a substrate. This coating was formed at low-pressure and low-energy using an inductively coupled plasma process. A strong dependence between the ratios of gases during deposition and the composition of the substrate compounds was shown. The values of ratios between Ar (or Ar+N2) and C4F8 - 1:1 and between N2 and Ar - 1:2 in the N2/Ar/C4F8 mixture were found as the best for low fluoridated coatings. In addition, an example of improving the etch-passivation in the Bosch procedure was described. Scanning electron microscopy with energy dispersive spectroscopy options, X-ray diffraction, and X-ray reflectivity were used for quantitative analysis of the deposited films.

Adsorption induced phase transition in Ti(Pc)2 gas sensing films: A joint AFM-EDXR study

The morphological properties of thin metal phthalocyanine films, used as active material in gas sensing devices, are studied. Morphological changes, such as bulk or surface phase transitions, are key phenomena, having a determinant influence on the final properties and stability of the materials and devices. In this work, we successfully prove that joint in-situ atomic force microscopy and Energy Dispersive X-ray Reflectivity can be used, not only to monitor the sensing activity of bi[phthalocyaninato(2-)]titanium(IV) films, but also as a powerful tool to disclose the physical-chemical process beneath the sensing activity. Indeed it is shown that NOx adsorption activates a phase transition in the TiPc2 film, characterized by an oscillating behavior between two metastable states. Such phenomena endure as long as the gas molecules are present, finally evolving into the thermodynamically most stable phase. Fourier transform infrared spectroscopy analysis supports the above conclusions.

Citric acid/ZrO2 nanocomposite inducing thermal barrier and self-cleaning properties on protein fibers

The present research carried out to stabilize nano-ZrO2 on the wool fabric using citric acid (CA) as a crosslinking agent and sodium hypophosphite (SHP) as a catalyst under UV irradiation. The influence of the amount of nano-ZrO2 on the performance of wool fiber was investigated by the use of Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray spectroscope (EDX) and reflectance spectrophotometer (RS). The possible interactions between nano-ZrO2 particles, cross-linking agent and wool free radicals were elucidated by the FTIR spectroscopy. Results indicated that the stabilized nano-ZrO2 enhances the thermal stability of wool. Photo-catalytic activities of the coated wool were evaluated through degradation of methylene blue (MB) under UV irradiation.

Hydrangeas-Like Bi2WO6: Facile Synthesis, Visible-Light Driven Photocatalysis and Theoretical Analysis

Hydrangeas-like Bi2WO6 powders were synthesized successfully by salt-ultrasonic assisted hydrothermal process, which were characterized by scanning electron microscopy (SEM), Energy dispersive X-ray (EDS), X-ray diffraction (XRD), and UV-visible diffuse reflectance spectra (UV-Vis DRS), respectively. Bi, W and O elements were contained in the product, which could be tested by EDS. The crystal structure of the catalyst was orthorhombic phase (JCPDS card no.73-1126). And the band gap was estimated to be 2.56 eV from the onset of UV-Vis absorption spectra of the catalyst. In addition, the photocatalytic activities of the products were investigated on the degradation of Rhodamine B (RhB). It demonstrated that photocatalysts exhibited excellent visible-light driven photocatalytic performance. And the target residue was less than 1% in 20 min under Xenon lamp irradiation. First-principles calculations based on density functional theory (DFT) were used to explore the electronic and optical properties of Bi2WO6. And the theoretical calculations could illustrate the photocatalytic performance of Bi2WO6 powders under visible light irradiation.

Chain-length dependent growth dynamics of n-alkanes on silica investigated by energy-dispersive x-ray reflectivity in situ and in real-time

We compare the growth dynamics of the three n-alkanes C(36)H(74), C(40)H(82), and C(44)H(90) on SiO(2) using real-time and in situ energy-dispersive x-ray reflectivity. All molecules investigated align in an upright-standing orientation on the substrate and exhibit a transition from layer-by-layer growth to island growth after about 4 monolayers under the conditions employed. Simultaneous fits of the reflected intensity at five distinct points in reciprocal space show that films formed by longer n-alkanes roughen faster during growth. This behavior can be explained by a chain-length dependent height of the Ehrlich-Schwoebel barrier. Further x-ray diffraction measurements after growth indicate that films consisting of longer n-alkanes also incorporate more lying-down molecules in the top region. While the results reveal behavior typical for chain-like molecules, the findings can also be useful for the optimization of organic field effect transistors where smooth interlayers of n-alkanes without coexistence of two or more molecular orientations are required.

Time-resolved morphological study of ‘PEDOT:PSS’ hole transporting layer for polymer solar cells

The reliability of the polymeric hole transport layer poly(3,4-ethylenedioxythiophene):poly(styrenesulphonate) (PEDOT:PSS), used in organic photovoltaic and single carrier diodes was addressed. The morphological properties of the blend were monitored during thermal treatments and under controlled humidity condition. The approach adopted, relying on joint use of in situ energy dispersive X-ray reflectivity (EDXR) and atomic force microscopy (AFM) techniques, allowed to observe, in real time, the occurrence of degradation phenomena related to both bulk and interface effects. Additionally, Fourier transform infrared (FTIR) spectroscopy experiments provided information on the chemical properties correlated to the blend morphological modifications. The overall approach allowed to identify aging process that may compromise the chemical–physical characteristics of the PEDOT:PSS hole conducting layer and, in turn, may have a relevant impact on the performances of the organic devices.

Energy dispersive X-ray reflectivity applied to the study of thermal stability of self-assembled organic multilayers: Results on phosphonic acids

The temperature evolution of self-assembled phosphonic acid multilayers was investigated by energy dispersive X-ray reflectivity and angular-resolved reflectivity. Energy dispersive measurements were performed in an experimental setup specially designed for the X-ray fluorescence beamline of the Brazilian Synchrotron Light Laboratory. It allows the precise monitoring of phase transitions observed in organic thin film and multilayer systems. The studied multilayers – obtained from dip coating of a solution of octadecylphosphonic acid – present different bilayer periodicities of 50Å (straight bilayer) and 34Å (tilted bilayer). Energy dispersive and angular-resolved data evidence re-organization of the lamellar ordering of octadecylphosphonic acid multilayers as a function of temperature. The energy dispersive technique presents many advantages over conventional methods such as short acquisition time, possibility to vary external parameters and high flux, making it suitable for light scatterers as polymers and other organic molecules.

Discriminating bulk, surface and interface aging effects in polymer-based active materials for efficient photovoltaic devices

The present study, reporting time-resolved investigations of polymer-based films for plastic photovoltaics, particularly focuses on aging related to the devices interface properties. The unconventional approach used is based on an in situ cross-monitoring of the films structural/morphological properties. For this propose, Energy Dispersive X-ray Reflectivity and Diffraction techniques were used in synergy with atomic force microscopy analysis. In this way, the meso-scale modifications of the organic film bulk, surface and buried interface with the electrode, were observed directly. As a result of such non-destructive characterization, access to the concomitant chemical–physical processes, occurring to the cell active component during illumination and related to degradation and reliability issues, is gained.