During the last few decades, non-thermal plasma surface functionalization of polymeric materials has increasingly earned a high-flying position in a wide range of application fields. Nonetheless, ...given the diversity of chemical reactions occurring between the surface and the multitude of active species present in plasma, a chaotic insertion of non-specific surface functional groups might befall. Therefore, achieving controlled surface chemistries can be a challenging approach demanding excessive optimization of the working parameters. In fact, correlations between the used working parameters, the generated plasma active species and the induced surface chemistry should be carefully analyzed for a deeper fundamental understanding of the plasma-surface interactions. To do so, researchers have been employing a broad range of surface analytical techniques with X-ray photoelectron spectroscopy (XPS) being the most widely used since it accurately determines the surface chemical composition at a depth approximately equaling the region depth affected by the plasma activation (a few nanometers). This review paper is therefore dedicated to provide an extensive overview on the different XPS measurement capabilities applied to chemically characterize plasma-activated polymeric surfaces. Beside the typical measurements determining the surface elemental composition, more advanced XPS analyses will be discussed such as peak fitting, XPS mapping, angle resolved XPS, derivatization reactions combined with XPS analyses and SEM-like imaging capabilities of XPS used for 3D scaffolds. Moreover, clear distinctions between post-plasma and exclusive in-plasma surface interactions are also made via a literature overview involving XPS analyses undertaken in situ. Finally, the well-known ageing effect of plasma-activated surfaces is deeply tackled through XPS measurements performed after relatively prolonged storage times. The limitations associated with some of the reported XPS analyses are also comprehensively discussed. An extended knowledge on plasma surface interactions could be as such gained. Overall, this review constitutes a perfect-picture reference for all future studies involving a plasma activation of polymers in particular and XPS analyses in general.
Display omitted .
Oxygen vacancies play a crucial role in shaping the properties of metal oxides for diverse applications such as catalysis, ferroelectricity, magnetism, and superconductivity. Although X-ray ...photoelectron spectroscopy (XPS) is a robust tool, accurate quantification of oxygen vacancies remains a challenge. A common mistake in XPS analysis is associating the 531–532 eV feature in O 1s spectra with oxygen vacancies. This is incorrect because a vacant oxygen site does not emit photoelectrons and therefore does not generate a direct XPS spectral feature. To address this issue, we propose three alternative approaches for oxygen vacancy analysis with XPS through indirect features: (1) quantifying cation valence state variations, (2) assessing oxygen nonstoichiometry via normalized oxygen spectral intensity, and (3) evaluating Fermi energy changes from electrostatic shifts in the binding energy. The recommended strategies will facilitate precise XPS analysis of oxygen vacancies, promoting future studies in understanding and manipulating oxygen vacancies for advanced material development.
•The Zn0.98Fe0.02O compound was synthesized at different pH values (3 and 9).•XPS detected oxygen vacancies.•Two valence states were found for the Fe cations (Fe3+ and Fe2+).•The photocatalyst ...degraded 98 % of the CIP drug at pH 3 and 95.3 % at pH 9.•Superoxide radicals play a crucial role in CIP drug degradation.
In this work, the Zn0.98Fe0.02O compound was synthesized at different pH values (3 and 9) and the Fe cations valence state, oxygen vacancies, and ciprofloxacin photocatalytic degradation were investigated. The X-ray photoelectron spectroscopy (XPS) reveals the oxygen defects or vacancies presence and confirms the coexistence of Fe3+ and Fe2+oxidation states in the samples. The morphological analysis showed the semispherical particle cluster formation. For the Zn0.98Fe0.02O system, the photocatalytic degradation of the ciprofloxacin drug was highly efficient, with degradation rates reaching 98 % and 95.3 % at pH values of 3 and 9, respectively. In addition, superoxide radicals were identified as the primary species involved in the ciprofloxacin (CIP) degradation mechanism, as indicated by scavenger tests. This study underscores the effectiveness of the Zn0.98Fe0.02O photocatalyst synthesized at different pH levels for ciprofloxacin removal, a drug widely used by humans.
White light emission has long been a focal point of research in the LED field for white lighting. The rare earth element Eu is commonly used as an efficient emission center with various wavelengths ...in different matrices. In this study, white light emission is achieved by simply adjusting the ratio of Eu3+/Eu2+ in Sr2MgSi2O7 phosphor, a phenomenon not observed in previous literature due to the difficulty to realize the photoluminescence of Eu2+ and Eu3+ in a same matrix simultaneously. The targeted Sr2MgSi2O7:9 %Eu fluorescent powder was synthesized under reducing atmosphere conditions, followed by oxidation in an air atmosphere for different durations. The phosphor samples exhibited characteristic Eu3+ and Eu2+ spectra in the XPS results, corresponding to the coexistence of Eu3+ and Eu2+ with varying ratios. The presence of Eu2+ and Eu3+ in the Sr2MgSi2O7 matrix leads to white light emission at an optimal Eu2+/Eu3+ ratio. Specifically, the broad emission peak of Eu2+ is located at 460 nm, which is resulted from the transformation from 4 f6 5d1 to 4 f7 for Eu2+ ions and causes a blue light emission. Meanwhile, typical peaks for Eu3+ are detected at 590 nm, 615 nm, 650 nm and 703 nm, corresponding to transitions from the 5D0 to 7F1, 5D0 to 7F2, 5D0 to 7F3 and 5D0 to 7F4 energy levels in Eu3+ ions, emitting orange-red light. Overall, the Eu3+ and Eu2+ co-doped Sr2MgSi2O7 phosphor prepared in our study emits white light under near-ultraviolet excitation, with CIE coordinates of (0.3058, 0.2274), falling within the white region in the CIE color diagram. These results suggest the potential application of the phosphor in the white LED field.
•Sr2MgSi2O7:Eu2+, Eu3+ white emitting phosphors were successfully prepared.•Both Eu2+ and Eu3+ show photoluminescence in the silicate matrix.•Eu2+ offers a blue emission peaking at 460 nm due to 4 f6 5d1 to 4 f7 transition.•Eu3+ reveals orange-red emission attributed from 5D0 to 7FJ transition.•White emission was achieved with 9 %Eu: Sr2MgSi2O7 by adjusting Eu2+ / Eu3+ ratio.
Samples of the iron oxides Fe0.94O, Fe3O4, Fe2O3, and Fe2SiO4 were prepared by high temperature equilibration in controlled gas atmospheres. The samples were fractured in vacuum and high resolution ...XPS spectra of the fractured surfaces were measured. The peak positions and peak shape parameters of Fe 3p for Fe2+ and Fe3+ were derived from the Fe 3p XPS spectra of the standard samples of 2FeO*SiO2 and Fe2O3, respectively. Using these parameters, the Fe 3p peaks of Fe3O4 and Fe1-yO are analysed. The results indicate that high resolution XPS techniques can be used to determine the Fe2+/Fe3+ ratios in metal oxides. The technique has the potential for application to other transition metal oxide systems.
In this current investigation, a straightforward method is presented for synthesis of Yb-doped SnO2 (Yb = 0%, 0.5%, 1.5%, 3% and 5%) NPs using a sol-gel approach. Various techniques were used to ...analyze the surface morphology, crystalline structure, chemical composition, and optical properties of the prepared samples. XRD, FTIR, and HRTEM confirmed nanoparticle formation. Raman, XPS, and PL spectroscopy were employed to examine electronic, optical properties, and lattice defects. Introducing Yb dopant into Yb-SnO2 NPs enhanced their optical features, as indicated by a significant red shift. These particles exhibited impressive catalytic efficiency, degrading 98% of a 10 ppm RB dye solution within a 60-min period under UV light irradiation. Furthermore, the recyclability analysis demonstrated that the 5% Yb catalyst can be recycled multiple times. Scavenger tests were performed for the 5% Yb sample to explore primary active species involved in the degradation process. The magnetic features of the synthesized samples were investigated using VSM analysis, revealing an increase in Mmax from 3.98 × 10−3 to 10.40 × 10−3 emu/g. This enhancement was associated with the activation of the FCE, induced by the presence of oxygen vacancies. These findings are instrumental in propelling the advancement of sophisticated materials for both sustainable wastewater treatment and applications in spintronics.
This study details the effective solution combustion synthesis of novel Na1−xZr2Dyx(PO4)3(x=0.05−0.5) (hereby abbreviated as NaZrPO:Dy3+) phosphor. The structural investigation of synthesized ...phosphor employing X-ray diffraction and FTIR spectroscopy reveals the formation of single-phase phosphor and the presence of (PO4)3- group. The lattice parameters turned out to be a=b=8.798Å,c=22.794Å. The morphological and chemical analysis is characterized by FE-SEM and X-ray photoelectron spectroscopy, respectively. According to PL spectrum, three traditional emission bands of Dy3+ ions (482 nm, 574 nm, and 663 nm) are observed, and the concentration quenching of the Dy3+ ions in the phosphor occurred at 3 mol. % as a result of the dipole-dipole interaction. Photometric results reveal the emission of the synthesized phosphor in the yellow-whitish region with a color purity of ∼80%. The optical parameters obtained from diffuse-reflectance spectroscopy, such as refractive index, metallization criterion, and bandgap, for the optimal molar concentration (3 mol. %) are 2.109, 0.46, and 4.3 eV, respectively. According to these results, when stimulated by a source of n-UV (348 nm), the synthesized phosphor is a promising candidate for solid-state lighting applications and might be used to produce WLEDs.
Display omitted
•An epoxy system with self-healing/barrier anti-corrosion functions were fabricated.•GO-PPy-Zn was fabricated via one-pot polymerization of pyrrole monomers on GO.•The GO-PPy-Zn ...significantly improved the epoxy coating anti-corrosion performance.
Designing a novel epoxy composite system with dual self-healing/barrier anti-corrosion functions using graphene oxide (GO) nano-platforms decorated by polypyrrole (PPy) nanoparticles doped with zinc metal ions is the major objective of this research attempt. GO-PPy-Zn nanoplatform was fabricated via one-pot polymerization of pyrrole monomers on GO and two direct/indirect methods of zinc doping. In order to verify the PPy nanoparticles synthesis on GO sheets several analyses such as UV–visible, XPS, HR-TEM and FE-SEM were performed. The epoxy nanocomposite coatings containing GO-PPy and GO-PPy-Zn nanoplatforms were fabricated and applied on carbon steel. The nanocomposite coatings anti-corrosion capability was examined by electrochemical impedance spectroscopy (EIS), salt spray and pull-off adhesion test methods. The results of XPS analysis and HR-TEM and FE-SEM images demonstrated the zinc doped PPy nanoparticles formation on the GO nanoplatform. The great potency of GO-PPy-Zn on the epoxy coating anti-corrosion performance promotion, self-healing-barrier properties enhancement and cathodic delamination resistance improvement were obtained on carbon steel.
Display omitted
•Established method to prepare Cu/Au/ceria model catalysts for analysis by MEIS/XPS.•Discrete Cu and Au nanoparticles are thermally stable on ceria surface.•MEIS detects oxygen ...induced surface segregation of copper in Cu/Au nanoparticles.
Bimetallic catalysts are often more active and/or selective than their monometallic counterparts. The behaviour of such catalysts is frequently strongly dependent on the molar ratio of the two elements as well as nanoparticle size and the interaction with the support material. X-ray photoelectron spectroscopy (XPS) is an excellent surface analytical technique for probing the electronic properties of catalytic systems. When a mixture of pure and alloyed particles is present, it is more difficult to extract information from XPS given that it is a spatial averaging technique. Recently, the technique of medium energy ion scattering (MEIS) has been exploited to investigate the depth-dependent composition of nanoparticles on planar surfaces. Herein, we combine the two techniques to investigate the nature of Cu and Au nanoparticles deposited onto ultrathin CeO2 films on Si(111) examining their morphology and chemical composition as a function of annealing temperature for samples that have been maintained in an ultrahigh vacuum environment and exposed to air. The Cu/Au/CeO2/Si(111) is chosen as a model system in order to provide insight into how the catalytic properties of Cu/Au/CeO2 depend on the presence of discrete Cu and Au particles versus fully intermixed Cu/Au systems.
