Concentration Dependence Research Articles

Variants of Surface Charges and Capacitances in Electrocatalysis: Insights from Density-Potential Functional Theory Embedded with an Implicit Chemisorption Model

Prevalent electrolyte effects across a wide range of electrocatalytic reactions underscore the general importance of the local reaction conditions in the electrical double layer (EDL). Compared to traditional EDLs, the electrocatalytic siblings feature partially charged chemisorbates that could blur our long-held views of surface charge densities and differential capacitances—two interrelated quantities shaping the crucial local reaction conditions. Herein, five variants of surface charge density and three variants of differential capacitance in the presence of chemisorbates are defined and compared. A semiclassical model of electrocatalytic EDLs is developed for a quantitative analysis of the differences and interrelationships between these variants of surface charge densities and differential capacitances. It is revealed that the potential- and concentration-dependent net charge on these chemisorbates dramatically changes the surface charge densities and differential capacitances. Specifically, the free surface charge density could decrease as the electrode potential becomes more positive, implying that the . The relationship between the free and total surface charge densities is analyzed with aid of the concept of electrosorption valency. By linking the electrosorption valency with the differential capacitance in the absence of chemisorbates, we explain the potential and concentration dependence of the former. The conceptual analysis presented in this work has important implications for experimental characterization and first-principles-based atomistic simulations of electrocatalysis and EDL effects. Particularly, we disclose a hidden yet potentially crucial disadvantage of widely employed atomistic simulation models that fix the coverage of chemisorbates. Proposing the self-consistent implicit model as an expedient remedy for this disadvantage, this work contributes to more realistic modeling of electrocatalytic EDLs. Published by the American Physical Society 2024

Between the cracks: Blind spots in regulating media concentration and platform dependence in the EU

Alongside the recent regulations addressing platforms and digital markets – the Digital Services Act (DSA) and the Digital Markets Act (DMA) – the European Union’s (EU) European Media Freedom Act (EMFA) aims to safeguard media freedom and pluralism, two essential pillars of democracy. The EMFA introduces several provisions, including rules specifically focused on assessing media concentration in "the online environment". While these initiatives are commendable, there are noticeable blind spots in how EU regulations tackle the issues of dependence on, and the power of, platforms amidst the rising trend of media concentration. An essential aspect that needs attention is the technological power of these platforms, underpinned by their economic and political power. We find that neither the infrastructural power of platforms – transforming them from “gatekeepers” to “digital infrastructure and AI providers” – nor their relational power – creating imbalances and dependencies while posing sustainability challenges for (local) journalism – are effectively addressed in the current EU regulatory frameworks, despite both forms of power driving digital media concentration. The article then concludes with recommendations for a way forward capable of preserving values such as media pluralism and editorial independence.

Composition of the Low Molecular Weight Metabolome of Potamogeton perfoliatus (Potamogetonaceae) as an Indicator of the Transformation of the Ecological State of the Littoral Zone

The composition and nature of changes in the low-molecular-weight metabolome (NM) of Potamogeton perfoliatus L., growing in 6 biotopes of Lake Ladoga with different types of the anthropogenic load has been analyzed. According to the research results, it was found that the total number of low molecular weight organic compounds (LMWOCs) in the P. perfoliatus NM composition is directly dependent on anthropogenic load, which is well marked by the development of cyanobacteria. The greater the intensity of pollution or eutrophication of waters, or the higher the number of cyanobacteria, the lower the total number of LMWOCs and their concentration. A strongly pronounced dependence of the total concentrations of groups of NM compounds on the anthropogenic disturbance of the biotope and the concentration of cyanobacteria was revealed. A decrease in the number, relative amount, total concentration of carboxylic acids, number and content of unsaturated fatty acids, and, at the same time, an increase in the composition and content of phenols and the total content of aldehydes and ketones depends on an increase in anthropogenic pressure. The specific composition of NM of pierced pondweed depends on its response to biotic and abiotic factors of the aquatic environment, including anthropogenic ones. The revealed features of the change in the composition of P. perfoliatus NM make it possible to use it as an integral indicator of the anthropogenic impact on the littoral biotopes of water bodies and the deterioration of their ecological state.

High-Pressure Monosulfide Solid Solution FexNi1−xS Phases: X-Ray Diffraction Analysis and Raman Spectroscopy

High-pressure high-temperature (HPHT) crystalline monosulfide solid solution (Mss) phases (FexNi1−xS, x = 0.90, 0.75, 0.50, 0.25), troilite (FeS I), and α-NiS of the Fe-Ni-S system were synthesized at 7 GPa and 900–1550 °C. The structural parameters of the obtained phases were refined by XRD using the Rietveld method. Factor group analysis revealed the number of active Raman modes for FeS I and α-NiS. Raman spectra of troilite, α-NiS, and Mss phases were obtained. It was shown that the Raman spectra of Mss phases and α-NiS have a similar topology. The Raman spectra of the experimental phases in the Fe-Ni-S system were analyzed with non-negative matrix factorization, which provided a meaningful concentration dependence of the spectral patterns. The spectral components were assigned to the FeS I and α-NiS structures. The structural and spectroscopic studies show linear dependencies of unit cell parameters and spectral components on composition and confirm the existence of a series of monosulfide solid solution FexNi1−xS.

Transfer learning for accurate description of atomic transport in Al-Cu melts.

Machine learning interatomic potentials (MLIPs) provide an optimal balance between accuracy and computational efficiency and allow studying problems that are hardly solvable by traditional methods. For metallic alloys, MLIPs are typically developed based on density functional theory with generalized gradient approximation (GGA) for the exchange-correlation functional. However, recent studies have shown that this standard protocol can be inaccurate for calculating the transport properties or phase diagrams of some metallic alloys. Thus, optimization of the choice of exchange-correlation functional and specific calculation parameters is needed. In this study, we address this issue for Al-Cu alloys, in which standard Perdew-Burke-Ernzerhof (PBE)-based MLIPs cannot accurately calculate the viscosity and melting temperatures at Cu-rich compositions. We have built MLIPs based on different exchange-correlation functionals, including meta-GGA, using a transfer learning strategy, which allows us to reduce the amount of training data by an order of magnitude compared to a standard approach. We show that r2SCAN- and PBEsol-based MLIPs provide much better accuracy in describing thermodynamic and transport properties of Al-Cu alloys. In particular, r2SCAN-based deep machine learning potential allows us to quantitatively reproduce the concentration dependence of dynamic viscosity. Our findings contribute to the development of MLIPs that provide quantum chemical accuracy, which is one of the most challenging problems in modern computational materials science.

Energetics of Point Defects in D0a Ag3Sn: First‐Principles Calculations

The Ag3Sn intermetallic compound is commonly found and acts as a strengthening factor in the key lead‐free solders based on Sn‐Ag‐Cu. The Ag3Sn phase exhibits also an asymmetric off‐stoichiometry, which necessitates the existence of constitutional point defects. The presence of point defects can, in general, sensitively affect the plastic deformation of materials and the strengthening role of Ag3Sn in particular. To understand the nature of the point defects and the compositional stability of Ag3Sn, the relaxed structures and the energies of single point defects (vacancies and antisite defects) in all three sublattices of Ag3Sn are calculated at 0 K using ab initio density functional theory (DFT) and the supercell method. The first‐principles‐based calculations predict that the AgSn antisite defect (Ag substitution for Sn) has the smallest enthalpy of formation, thus indicating that the AgSn antisite defect is the dominant point defect in Ag3Sn. The point defect concentrations as a function of Sn content are estimated using the DFT defect energies and the Wagner–Schottky model. The compositional dependence of the point defect concentrations gives new insights on the atomistic mechanisms of formation of nonstoichiometric Ag3Sn.

Additive effect of Li on electrical property of ZnO passivation layer to control dendritic growth of Zn during recharge processes

This study investigates the effect of Li+ on the dendritic growth of Zn anodes in the presence of a ZnO passivation layer formed after discharge, with particular attention to the initial recharge process. 0.1 mol dm−3 Li+ effectively suppresses dendrites, while 2 mol dm−3 Li+ addition facilitates the same. The difference in Zn dendrite formation behavior is also indicated by the attenuation tendency of the potential oscillation accompanied by hydrogen evolution reaction during recharge. This is attributed to Li+ concentration dependence of the properties of the ZnO passivation layer formed during Zn anode discharge. Li+ modulates the carrier density of ZnO by altering its crystalline defect characteristics; the carrier density of ZnO with 0.1 mol dm−3 Li+ addition becomes approximately three times as high as that without additive owing to the oxygen vacancies and interstitial zinc that form additional donor level. By contrast, 2 mol dm−3 Li+ reduces the carrier density of ZnO by inducing zinc vacancies to form acceptor levels. The highly conductive ZnO produced by adding 0.1 mol dm−3 Li+ improves the reaction uniformity during recharge, which suppresses dendrite formation. This study provides valuable insight into the mechanisms and control strategies of Zn dendrite growth during the charge-discharge cycling of alkaline Zn rechargeable batteries.

Evidence of conformational changes and self-aggregation of 1,2-Bis(4-pyridyl)ethylene in solutions with ethanol

In this work, we report on a concentration and temperature dependent study of the 1,2-Bis(4-pyridyl)ethylene (BPE) – ethanol solutions by means of ultrasonic relaxation spectroscopy. The results revealed two distinct relaxation processes that follow Debye-type frequency dependence. Despite the presence of both processes in the full concentration range studied, the low-frequency relaxation process, related to conformational change between the trans- and gauche-BPE conformers, dominates the acoustic spectra in the low-concentration range, while diminishes at higher concentrations with a parallel enhancement of the high-frequency relaxation process, which is attributed to the self-association of BPE molecules. Quantum mechanical calculations were performed to investigate the energetics of the trans- and gauche-conformers. The trans-species was found more thermodynamically stable than the gauche-conformer. By applying the Synchronous Transit-Guided Quasi-Newton (STQN) methodology, we confirmed the presence of a single transition structure. From the temperature dependence of the acoustic properties, we estimated the activation enthalpy and the enthalpy difference between the two conformers. Density Functional Theory (DFT) calculations have been applied to attain the corresponding enthalpies that were found close to the experimental values. Molecular docking calculations established the self-aggregation mechanism between BPE monomers forming three types of dimeric units, namely the trans-trans, the gauche-gauche and the trans-gauche dimer species with the latter found to be the most thermodynamically favorable. The concentration dependence of the sound velocity, mass density and shear viscosity evidenced the formation of BPE aggregates. From the temperature dependence of the acoustic spectra, the thermodynamic properties of the self-aggregation mechanism of BPE were also determined. Based on the vibrational spectroscopic data, the population of the gauche conformers was found to increase with concentration at the expense of the population of the trans conformers. From the study of the vibrational properties of the system in the short-rage order, we cannot exclude the presence of a specific dimer type in the overall structure. Nevertheless, regarding to the binding score of the trans-gauche dimer (-1.25 kcal/mol), this species is the most thermodynamically stable and most likely its population is higher in dense solutions relative to the other two dimer species.

Dy3+ ions in fluorophosphate glasses for luminescent white light applications

Abstract In this study, a series of fluorophosphate (FP) glasses, activated with Dy3+ ions and displaying concentration dependence, have been prepared and analysed for their suitability in luminescent white light applications. The melt quenching method was utilized to fabricate a set of FP glasses, doped with Dy3+ ions and possessing the composition of (60 − x) P2O5 + 10MgO + 10ZnO + 10BiF3 + 10KF + xDy2O3, where x ranges from 0.1 to 2.0 mol%. The structural properties of the samples were analysed using x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), and Raman spectroscopy while the optical properties of the samples were studied using absorption and emission spectra. The amorphous nature of the FP glasses was confirmed through SEM analysis and XRD profiles. Moreover, the presence of elements in their composition was verified using EDX. The FTIR spectra of the FP glasses exhibited vibration bands consistent with the characteristic phosphate groups, which was further supported by Raman analysis. The absorption spectra were used to calculate oscillator strengths (f exp & f cal) and Judd–Ofelt (JO) parameters Ω λ (λ = 2, 4, 6). The values of Ω λ (λ = 2, 4, 6) followed this order: Ω6 > Ω2 > Ω4. The emission spectra displayed three prominent transitions in the UV–visible region: (4F9/2 → 6H15/2) blue, (4F9/2 → 6H13/2) yellow, and (4F9/2 → 6H11/2) red. The peak at 553 nm (4F9/2 → 6H13/2) was the most intense and dominant. Radiative characteristics were evaluated from the emission spectra through the employment of JO intensity parameters and refractive indices. The Y/B intensity ratio values were greater than 1, indicating the high covalency of Dy3+ ions. The colour coordinates (x, y) and correlated colour temperature values of CIE 1931 were situated in the cool white region. The comprehensive analysis suggests that these glasses have the potential to become highly favourable candidates as luminescent components for solid-state white light emitting instruments.

Enhanced the quantum efficiency of Tm3+ ∼2 μm laser in crystal through an energy transfer process of 3H5 level

The concentration dependence of the fluorescence and lifetime evolutions of states relevant to three near-infrared emission bands were measured and analyzed for Tm:SrF2 crystals. The fast quenching of ∼1.2 μm fluorescence (3H5) was observed as the Tm concentration increased. The cross-relaxation and multi-phonon relaxation processes between Tm3+ ions cannot explain this phenomenon. Through spectral and rate-equation analysis, two possible energy transfer mechanisms, cross-relaxation from the 3H5 level and cooperative energy transfer within Tm3+ clusters, are proposed. And based on the new modified model, the quantum efficiency of the Tm ∼2 μm lasers could surpass the traditional 200% limit. This new energy transfer has the potential for exceptionally high efficiency excitation of Tm-doped laser materials.

Activity coefficients of 3-amino-1-propanol and 2-amino-1-propanol in aqueous solutions from surface tension data

Surface tension of 3-amino-1-propanol and (RS)-2-Amino-1-propanol in aqueous solution were measured in the temperature range from 293.15 to 308.15 K at intervals of 5 K over the whole concentration range. The concentration dependence of surface tension for both amino alcohols aqueous solution shows a similar behavior to that observed for other polar solutes in water. The surface tension data of 3-amino-1-propanol and 2-amino-1-propanol at the selected temperatures were accurately described using the integral Gibbs adsorption equation, the virial equation, and the Langmuir-Gibbs equation of state. The activity coefficients γ for both solutes were determined using the virial equation and found to be unitary within the experimental uncertainty, which was confirmed by the accurate representation of the experimental data by the Langmuir Gibbs Equation of State (LGSEOS). The standard adsorption energy calculated for both solutes from the fitting parameters of LGSEOS to the experimental data indicates that (RS)-2-amino-1-propanol has a higher hydrophobic character and a greater tendency to migrate to the surface than 3-amino-1-propanol as shown by the more negative ΔGads0 values for this solute than for 3-amino-1-propanol.

Dependence of nanowire length, diameter, and concentration on the electrochromic properties of hybrid silver nanowire network/PEDOT:PSS-based devices

Mixing silver nanowires is a relevant tool to increase the overall conductivity of hybrid electrochromic systems. Herein, the addition of silver nanowires with an average diameter of 30 nm, length of 88 um, and concentration of 3.0 mg/ml lowered the sheet resistance of PEDOT:PSS films from 280 Ω/sq to 34 Ω/sq. Further characterized for their electrochromic behavior, mixing silver nanowires with PEDOT:PSS films allowed lowering the turn-on voltage from -1.5 V to -1.1 V and reducing the switching time from 7 to 3.6 seconds. Furthermore, with the addition of silver nanowires into PEDOT:PSS, an expensive ITO transparent and environmentally impactful electrode material is no longer required. Electrochromic devices based on hybrid AgNW/PEDOT:PSS films showed higher colouration efficiency, lower sheet resistance, lower turn on voltage, and faster switching times as compared to electrochromic devices made with PEDOT:PSS films only.

The role of cuproptosis in gastric cancer.

As a biologically essential transition metal, copper is widely involved in various enzymatic reactions and crucial biological processes in the body. It plays an increasingly important role in maintaining normal cellular metabolism and supporting the growth and development of the human body. As a trace element, copper maintains the dynamic balance of its concentration in body fluids through active homeostatic mechanisms. Both excess and deficiency of copper ions can impair cell function, ultimately leading to cell damage and death. Cuproptosis is a novel form of cell death where copper ions cause cell death by directly binding to the lipoylated components of the citric acid cycle (CAC) in mitochondrial respiration and interfering with the levels of iron-sulfur cluster (Fe-S cluster) proteins, ultimately causing protein toxic stress. Its primary characteristics are Cu2+ concentration dependence and high expression in mitochondrial respiratory cells. Recent research has revealed that, compared to other forms of programmed cell death such as apoptosis, necrosis, and autophagy, cuproptosis has unique morphological and biochemical features. Cuproptosis is associated with the occurrence and development of various diseases, including cancer, neurodegenerative diseases, and cardiovascular diseases. This article focuses on a review of the relevance of cuproptosis in gastric cancer (GC).

Color tunability, concentration dependence, and temperature responsive afterglow of SrZn2(PO4)2: Eu2+, Mn2+ phosphors.

Long persistent luminescence (LPL) materials with color adjustable afterglow have a wide application prospect in display and information encryption, yet there are few reports on such materials. In this paper, SrZn2(PO4)2 phosphors with tunable and thermal stimuli-responsive afterglow emissions were synthesized by a solid-state method. After ultraviolet (UV) excitation, the prepared samples exhibited emission at 419 nm, 533 nm, and 633 nm due to Eu2+: 4f65d1 → 4f7 transitions, Mn2+: 4T2(4G) →6A1(6S) transitions, and Mn2+: 4T1(4G) → 6A1(6S) transitions, respectively. The Commission Internationale de I' Eclairage (CIE) coordinates of samples can be changed among blue, white, and yellow by varying the Mn2+ concentration. Additionally, due to the differing thermal stability of Eu2+ and Mn2+, the phosphor exhibited a temperature-responsive afterglow, and its colors can be adjusted between white and yellow over a temperature range from 293 K to 383 K. Given its distinctive temperature-responsive afterglow, the prepared phosphor is suitable for use as a temperature sensor. Moreover, the tunable afterglow colors of the phosphors are advantageous for application in anti-counterfeiting.

Synthesis, Structure, and Optical Property of Tris(biaryldiyl)metal Complexes Consisting of Group 9 Elements.

We report the synthesis and characterization of tris(biphenyl-2,2'-diyl)metal complexes of trivalent group 9 elements (1M, M = Co, Rh, Ir) and their nonplanarly π-extended analogs, tris(1,1'-binaphthyl-2,2'-diyl)metal complexes (2M, M = Rh, Ir). Single crystal X-ray crystallography reveals the distorted octahedral geometry with an approximate C3 symmetry of trianionic complexes 1M (M = Co, Rh, Ir) and 2M (M = Rh, Ir), which are contacted by three Li+ ions in the crystal. Complex 1Ir exhibits yellow luminescence in THF with a photoluminescence quantum yield (ΦPL) of up to 0.73, along with a distinctive photophysical property, namely, a concentration dependence of the emission wavelength from 530 to 580 nm. This is a characteristic property of 1Ir and has not been observed in its isoelectronic analog, tris(2-phenylpyridinato)iridium(III) (Ir(ppy)3). The concentration-dependent optical properties originate from the dissociation equilibria of Li+ ions from the anionic chromophore. Complex 2Ir also exhibits luminescence at 715 nm in THF, with a notable bathochromic shift from 1Ir through the π-extension. The findings offer insights into the photophysical properties of homoleptic organo-transition metal complexes, providing the foundation for the design of related transition metal complexes.

Concentration-Dependent Nonradiative Decay Mechanisms in Fluorescence Self-Quenching: Insights from Azulene and 1,3-Dichloroazulene

A series of steady-state and time-resolved spectroscopies were performed on azulene (Az) and its 1,3-dihalogenated analogue, 1,3-dichloroazulene (DCAz). Understanding the intra/inter-molecular interactions in these types of systems is the key to unlocking the potential of these molecules and enabling their application in a range of future devices. Therefore, the concentration dependence of their self-quenched fluorescence intensities and of the reduced lifetimes of their second-excited singlet states were examined. A Stern-Volmer analysis was implemented based on these experiments, which resulted in DCAz exhibiting a higher bimolecular quenching constant, compared to Az, due to its shorter excited-state lifetime. The highly efficient self-quenching at room temperature was a result of a short-range energy transfer mechanism.

Non-Stoichiometric Effects on Viscoelasticity in DGEBA-EDA Systems: Insights from Brillouin Light Scattering.

The initial and final stages of the isothermal curing reaction between diglycidyl ether of bisphenol A and ethylenediamine were investigated by using Brillouin light scattering spectroscopy. High-frequency acoustic parameters were measured for these stages as a function of the diamine molar fraction, ranging from the pure prepolymer to the pure cross-linker. Significant differences in the concentration dependencies of the mechanical parameters are interpreted in relation to changes in the system's viscoelastic properties. At the final stage of the reaction, the concentration dependencies exhibit notable changes at two characteristic nonstoichiometric compositions─one corresponding to amine excess and the other to epoxy excess. While these concentrations align well with Flory's critical gel points, experimental evidence suggests they should instead be interpreted as vitrification points.

Effect of Cr on nano-indentation Young's modulus and hardness of the β-Ti phase in equilibrium with α2-Ti3Al and γ-TiAl phases in Ti-Al-Cr alloys

Young's modulus and hardness of the constituent phases of β-Ti (bcc or B2), in equilibrium with α2-Ti3Al (D019) and γ-TiAl (L10) phases in Ti-Al-Cr ternary alloys were quantitatively evaluated in terms of the chemical composition analysis and nano-indentation method, in order to identify the Cr concentration dependence on the mechanical properties of the β phase. An alloy with a nominal composition of Ti-43Al-3Cr (at.%) decomposes into the three phases of β, α2, and γ by equilibrium heat treatment at 1373 K, with chemical composition of Ti-37.2Al-5.2Cr, Ti-38.9Al-2.2Cr, and Ti-47.4Al-1.4Cr, respectively. The β phase shows a Young's modulus of 141 ± 5 GPa, smaller and less orientation dependent than the other two phases of α2 (174 ± 9 GPa) and γ phases (164 ± 15 GPa). In contrast, the β phase has a hardness of 5.9 ± 0.3 GPa, slightly softer than the α2 phase (6.4 ± 0.8 GPa) but much harder than the γ phase (3.7 ± 0.6 GPa). The alloys Ti-44Al-4Cr and Ti-45Al-6Cr consist of two phases of β and γ phases, and the chemical composition of the β phase in these two alloys is Ti-36.5 Al-8.5 Cr and Ti-36.3 Al-13.9 Cr, respectively, with nearly the same Al concentration. The Young's modulus and hardness of the β phase with the latter composition become 158 GPa and 6.7 GPa, respectively, with increasing Cr content. These results found that the effect of solid solution Cr on the Young's modulus for β phase is relatively weak, and that on the hardness is strong, in comparison with that for the other two phases.

α-MnO2 with a cryptomelane structure for the non-enzymatic glucose electrooxidation in a neutral medium

A high demand for non-enzymatic glucose sensors and continuous glucose monitoring systems encourages the development of stable and active catalysts for the enzymeless anodic oxidation of glucose in the neutral medium. In regard to this reaction, we analyze the prospects of alpha manganese dioxide with a cryptomelane structure synthesized via an aqueous chemical route. To provide various specific surface area, the hydrated α-MnO2 oxide is annealed in a wide temperature range from 60 to 700 °C. Furthermore, we investigate the influence of the oxide annealing temperature on the amount of crystal water, chemical composition, morphology, electrochemical recharging behavior, electrocatalytic activity and stability in the glucose oxidation carried out in an isotonic NaCl-based phosphate-buffered saline (pH 7.40). To solidly determine potentials of the irreversible cathodic dissolution of α-MnO2 as well as O2/Cl2 evolution on α-MnO2, a rotating ring-disk electrode is applied. For the most active α-MnO2 sample with the 100 μg cm−2geo loading the glucose oxidation current of ca. 40 μA cm−2geo after 1 h at +0.8 V (SCE) for 7 mM of glucose is achieved. The linear concentration dependence in a physiological glucose range (1–30 mM) with the sensitivity of ca. 17.8 μA mM−0.5 cm−2geo at 25 °C is observed. Finally, glucose selectivity of α-MnO2 in relation to fructose, galactose, xylose, ribose, urea, lactic acid, acetone, ascorbic acid and paracetamol is revealed.

Unraveling Oxygen Vacancies Effect on Chemical Composition, Electronic Structure and Optical Properties of Eu Doped SnO2.

The influence of Eu doping (0.5, 1 and 2 mol.%) and annealing in an oxygen-deficient atmosphere on the structure and optical properties of SnO2 nanoparticles were investigated in relation to electronic structure. The X-ray diffraction (XRD) patterns revealed single-phase tetragonal rutile structure for both synthesized and annealed Eu-doped SnO2 samples, except for the annealed sample with 2 mol.% Eu. The results of X-ray photoelectron spectroscopy (XPS) emphasized that europium incorporated into the SnO2 host lattice with an oxidation state of 3+, which was accompanied by the formation of oxygen vacancies under cation substitution of tetravalent Sn. Moreover, XPS spectra showed the O/Sn ratio, which has been reduced under annealing for creating additional oxygen vacancies. The pulse cathodoluminescence (PCL) demonstrated the concentration dependence of Eu site symmetry. Combination of XRD, XPS and PCL revealed that Eu doping and following annealing induce strongly disordering of the SnO2 crystal lattice. Our findings provide new insight into the interaction of rare-earth metals (Eu) with host SnO2 matrix and new evidence for the importance of oxygen vacancies for optical and electronic structure formation.