XANES Research Articles

Biodegradation of vulcanized rubber by a gut bacterium from plastic-eating mealworms

The disposal of vulcanized rubber waste is difficult due to the presence of three-dimensional crosslinking network structure. Here, we report that a bacterium Acinetobacter sp. BIT-H3, isolated from the gut of plastic-eating mealworm, can grow on and degrade vulcanized poly(cis-1,4-isoprene) rubber (vPR). Scanning electronic microscopy (SEM) shows that strain BIT-H3 can penetrate into the vPR and produce craters and cracks. The tensile strength and the crosslink density of vPR decreased by 53.2% and 29.3% after ten weeks’ incubation, respectively. The results of Horikx analysis, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy reveal that strain BIT-H3 can break down both sulfide bridges and double bonds of polymeric backbone within vPR. Sulfate and oligo(cis-1,4 isoprene) with terminal aldehyde and keto groups were identified as metabolic products released during vPR degradation. Through genomic and transcriptional analyses, five enzymes of dszA, dszC1, dszC2, Laccase2147, and Peroxidase1232 were found to be responsible for vPR degradation. Based on the chemical structure characterizations and molecular analyses, a vPR biodegradation pathway was proposed for strain BIT-H3. These findings pave a way for exploiting vulcanized rubber-degrading microorganisms from insect gut and contribute to establish a biodegradation method for vulcanized rubber waste disposal.

Luminescence characteristics of Ce3+ doped multicomponent lithium fluorophosphate glasses

We have used the melt quenching technique to fabricate glass samples with the composition 20Li2O–10AlF3-2.5R-(57-x)P2O5-10Gd2O3-0.5CeF3 (R = 0, NaF, KF). These glasses were synthesized and their density, molar volume, refractive index, FTIR (Fourier-transform infrared spectroscopy) spectra, transmittance spectra, decay time analysis, and photo and radioluminescence properties were reported. Surface-sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge spectroscopy (XANES) were investigated. As a result, the FTIR spectra of these glasses break the Q2 tetrahedral sites of the phosphate structure when adding alkali fluoride. UV emission at ∼337 nm was observed at ∼302 nm excitation. In XPS spectra, phosphorus oxidation states (P2p) were detected. The investigation of X-ray Absorption Near-Edge Structure (XANES) of Ce LIII-edge was shown at ∼5.726 keV and confirmed the presence of Ce3+ and Ce4+ was shown at ∼5.731 keV and ∼5.738 keV. The comparison of the Ce3+ and Ce4+ ratios by fitting the energy range in the XANES spectrum may confirm the luminescence characteristic of the glass. A full energy peak was observed in the pulse height spectra of a 241Am α-ray irradiation in the PLGdAfKfCe0.5 glass, and the calculated light yields of PLGdAfKfCe0.5 was 49 Ph/MeV under α-ray. From the results can be concluded that the PLGdAfKfCe0.5 glass showed promising properties as a scintillator material.

Probing the Local Environment of Al-Substitution into Ferrihydrite Using DFT + U Calculations

Ferrihydrite (Fh) is a poorly crystalline oxyhydroxide that has attracted attention due to its importance in geochemistry, ion mobility, adsorption, and as a precursor for the formation of more crystalline phases such as goethite and hematite. A chemical model for the isomorphic substitution of the Fe sites by Al is proposed. DFT/plane wave calculations have been performed to provide information about the local environment of Al-substitution into Fh. The structural and electronic properties have been investigated in detail. Al prefers to replace the octahedral Fe sites, which has been evidenced by the comparison of the calculated Al K-edge X-ray absorption near-edge structure spectra with the available experimental data. The effect of the increasing ionicity of the system upon Al-substitution to the quadrupolar coupling constant of 27Al NMR and the Mössbauer quadrupole splitting and isomer shift parameters have been investigated. The results indicate that these parameters are affected by the concentration of Fe-substituted sites. Al-substitution increases the band gap dispersion with the formation of Al electronic states in the conduction band. The standard Helmholtz free energy of Al-substitution has been estimated and discussed in detail.

Gas-mediated trace element incorporation into rhyolite-hosted topaz: A synchrotron microbeam XAS study

Abstract Magmatic gas exsolving during late-stage cooling of shallow magmas has been considered an important facilitator of low-pressure alteration and metal transport. However, the chemical properties of such gas, particularly its metal transport mechanisms and capacity, remain elusive. Trace elements in minerals produced by gas-mediated surface reaction or precipitation from gas capture details of gas composition and reaction pathways. However, interpretation of mineral trace element contents is dependent on understanding crystallographic controls on gas/mineral partitioning. This work investigates the structural accommodation of As, Mn, Ga, Ge, Fe, and Ti in vapor-deposited topaz of vesicular topaz rhyolite from the Thomas Range, Utah, through single-crystal synchrotron microbeam X-ray techniques on picogram quantities of those trace elements. X-ray absorption near edge structure (XANES) data indicates that these elements are incorporated into topaz as As5+, Fe3+, Mn3+, Ti4+, Ga3+, and Ge4+. Extended X-ray absorption fine structure (EXAFS) analysis for these trace elements, compared to EXAFS of structural Al and Si, reveals that As5+ and Ge4+ are incorporated directly into the tetrahedral site of the topaz structure, with the octahedral site accommodating Mn3+, Fe3+, Ga3+, and Ti4+. For As5+ and Fe3+, the structural impact of substitution extends to at least second neighbors (other elements were only resolvable to first neighbors). Further interpretation of the EXAFS results suggests that the substitution of Ti4+ results in increased distortion of the octahedral site, while the other trace elements induce more uniform expansion correlating in magnitude to their ionic radius. Comparison of quantified X-ray fluorescence (XRF) data for two topaz crystals from this rhyolite reveals variable trace element concentrations for As5+, Fe3+, Ga3+, and Ti4+, reflective of a source gas undersaturated in these trace elements changing in concentration over the period of topaz deposition. The identical Ge4+ content of the two topaz crystals suggests that Ge4+ in the gas was buffered by the growth of another Ge4+-bearing phase, such as quartz. The very low Mn3+ content in the topaz crystals does not reflect the abundance of Mn3+ in the gas (saturation of Mn is evidenced by coexisting bixbyite). Instead, it suggests a strong Jahn-Teller inhibitory effect to the substitution of Mn3+ for Al3+ in the distorted octahedral site of topaz. It is proposed that exsolution of an HF-enriched gas from cooling rhyolitic magma led to local scouring of Al, Si, and trace metals from the magma. Once topaz crystals nucleated, self-catalyzed reactions that recycle HF led to continued growth of topaz.

A metallic nickel site in a complex multimetallic design for controlled CO2 reduction and symmetric supercapacitor device

Single metallic sites are promising for high power density with promising capacitive performance, and for low-energy chemical reduction of CO2 to formate. Here, we present a novel strategy for accessing C-ZIF-700 with metallic nickel (Ni) sites encapsulated by multiwalled nanotube shells from trimetallic imidazolate frameworks (M-ZIF). A X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopic analysis confirmed the zero-valance state of Ni, with no significant positive valance state. C-ZIF-700 showed no sign of leaching of Ni nanoparticles under aqua regia treatment for long, as evidenced from -XANES-EXAFSanalysis. It is demonstrated that the coexistence of Ni and Co in C-ZIF-700 renders more active electrochemical energy storage by regulating charge distribution to improve electronic transportation capability. C-ZIF-700 with predominantly metallic Ni-sites demonstrated superior capacitive performance, presenting a remarkable capacitance value of 262 F/g at a scan rate of 5 mV/s. In an assembled symmetric supercapacitor device , C-ZIF-700 exhibited a very high specific energy value of 21.2 Wh/kg at a current density of 0.05 A/g, which retained up to 9.7 Wh/kg at 10 A/g, and a corresponding specific power value of 25 kW/kg. C-ZIF-700 has offered facile N-formylation of the primary amine group of aniline, with the assistance of alkyl silane as a hydride source under moderate CO2 pressure (15–20 bar) and temperature (maximum 100 °C). Electronic structural evidence of metal sites in C-ZIF-700, by using XANES-EXAFS, electron microscopy, and CO2 adsorption–desorption profile supports that Ni-site is responsible for CO2 activation-reduction. The evidence also supports a possible synergistic effect of Co nanoparticles in capacitance enhancement and CO2 reduction. This strategy,thus, proves the outstanding role of encapsulated Ni sites for enhanced capacitive performance and chemical fixation of CO2.

Stepwise photoassisted decomposition of carbohydrates to H2

Stepwise photoassisted decomposition of carbohydrates to H2

Fraction of Free-Base Nicotine in Simulated Vaping Aerosol Particles Determined by X-ray Spectroscopies.

A new generation of electronic cigarettes is exacerbating the youth vaping epidemic by incorporating additives that increase the acidity of generated aerosols, which facilitate uptake of high nicotine levels. We need to better understand the chemical speciation of vaping aerosols to assess the impact of acidification. Here we used X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to probe the acid-base equilibria of nicotine in hydrated vaping aerosols. We show that, unlike the behavior observed in bulk water, nicotine in the core of aqueous particles was partially protonated when the pH of the nebulized solution was 10.4, with a fraction of free-base nicotine (αFB) of 0.34. Nicotine was further protonated by acidification with equimolar addition of benzoic acid (αFB = 0.17 at pH 6.2). By contrast, the degree of nicotine protonation at the particle surface was significantly lower, with 0.72 < αFB < 0.80 in the same pH range. The presence of propylene glycol and glycerol completely eliminated protonation of nicotine at the surface (αFB = 1) while not affecting significantly its acid-base equilibrium in the particle core. These results provide a better understanding of the role of acidifying additives in vaping aerosols, supporting public health policy interventions.

Effects of Codoping on Site-Dependent Eu3+ Luminescence in Perovskite-Type Calcium Zirconate and Hafnate

The single doping of Eu3+ and codoping with Ga3+ or La3+ into perovskite (ABO3)-type CaZrO3 and CaHfO3 were carried out to investigate the effect of codoping on the photoluminescence (PL) features of Eu3+, attempting the site-selective Eu3+ doping at either A or B sites. To comprehend the Eu3+ PL features, the accurate locations of Eu3+ were examined by X-ray absorption near edge structure (XANES) and the proportions of Eu3+ located at A or B sites (Eu3+(A) or Eu3+(B); EuCa• or EuZr'/EuHf') were analyzed. No considerable differences in the XANES spectra and in the proportions of Eu3+(A) and Eu3+(B) were observed in the single-doped samples. On the other hand, the shape of the XANES spectra and the Eu3+ proportion markedly differed in the codoped samples. Ga3+ codoping (GaZr'/GaHf') achieved Eu3+(A) proportions of more than 90%, and La3+ codoping (LaCa•) resulted in the largest Eu3+(B) proportions of approximately 40%. In both PL and PL excitation spectra, the site-dependent spectral features were changed depending on the proportion of Eu3+(A) and Eu3+(B), especially the PL peaks at 595 nm were intensified most in the La3+ codoped samples. Consequently, the site-dependent Eu3+ PL features in CZO and CHO were found to become more conspicuous by the effect of Ga3+ or La3+ codoping. The results also revealed that the codoped ions work not only to compensate for the charge of aliovalent Eu3+ but also to drive Eu3+ to the intentional doping sites.

Comprehensive kinetic study for Fischer–Tropsch reaction over KMoFe/CNTs nano‐structured catalyst

AbstractThe kinetics of the Fischer–Tropsch (FT) reaction was evaluated through detailed experimentation with a KMo bimetallic promoted Fe catalyst supported on carbon nanotubes (CNTs). The kinetic tests were conducted in a fixed‐bed reactor under operating conditions of P = 6.9–41.3 bar, T = 543–563 K, H2/CO = 1, gas hourly specific velocity (GHSV) = 2000 h−1. This study aimed to investigate the mechanism prevailing in CO activation and the rate equation for CO consumption during FT reactions over a 0.5K5Mo10Fe/CNTs catalyst. To evaluate the synergistic effects of Fe, Mo, and K phases on the catalyst activity, both fresh and spent catalysts were thoroughly characterized using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy‐dispersive spectroscopy (SEM‐EDS), X‐ray absorption near edge structure (XANES), and extended X‐ray absorption fine structure (EXAFS) to ascertain the different phases (active sites) present and relevant interactions. Based on the adsorption of carbon monoxide and hydrogen, 22 possible mechanisms for monomer formation were proposed for FT synthesis in accordance with the Langmuir–Hinshelwood–Hougen–Watson (LHHW) and Eley–Rideal (ER) adsorption theories. The best fit kinetic model was identified through a multi‐variable non‐linear regression analysis. The selected mechanistic model was based on carbide formation approach, where H2‐assisted adsorption of CO was considered for the derivation. Kinetic parameters such as activation energy, adsorption enthalpies of H2, and CO were estimated to be 65.0, −13.0, and −54.0 kJ/mol, respectively. Considering the developed kinetic model, the effects of reaction temperature and pressure were assessed on Fischer–Tropsch synthesis (FTS) product distribution. Additionally, the kinetic model was compared with the typical Anderson–Schulz–Flory model, suggesting the effects of water‐gas‐shift and the existence of additional formation pathway such as secondary re‐adsorption of olefins for heavier hydrocarbons.

Consequence of microwave synthesis of Li3.6Si0.6V0.4O4 for electrode application using LiNO3, V2O3, and silica obtained from rice husk ash

Lithium silicon vanadium oxide (Li3.6Si0.6V0.4O4) was synthesized by microwave-assisted solid-state reaction with grinding times of 1, 2, 4, and 6 h and applied as electrode material using silica from rice husk ash and crushed V2O3 and LiNO3 at 600 watts. This research found that the influence of microwave heating affects the generation Li3.6Si0.6V0.4O4 and the microwave wattage can remove excess nitrate in the system. As a result of different wattages, different products are produced, with 600 watts providing good crystallinity. Fourier transform infrared (FTIR) and Raman spectroscopy were used to measure bond vibrations within the molecules to confirm the presence of (Si − O), (Li − O), (Si − O−Si), and (V–O), while X-ray diffraction was conducted to confirm the phase of Li3.6Si0.6V0.4O4 as an orthorhombic lattice. X-ray absorption near edge structure (XANES) identified oxidation states of vanadium in the product as V4+ and V5+ while scanning electron microscopy (SEM) images showed the morphology to be highly porous with compact crystallinity. The product has high specific capacitance with a grinding time of 6 h and heated at 600 W at 289–461 F.g−1 using a scanning rate of 5 mV.s−1.

As [formula omitted]-edge absorption at high pressures in AFeAs (A=Na/Li): First principles results

As K-edge X-ray absorption near edge structure (XANES) for NaFeAs and LiFeAs has been examined at very high pressures up to 240 GPa through first principles studies. At higher pressures as well as at higher photon energies both the compounds exhibit larger number of prominent spectral features in absorption spectra. Electronic origin of non-identical spectroscopic features corresponding to different local structural environment is described thoroughly using the unoccupied atom projected partial density of states. Overall we find that the near edge features are dominated by 1s→p type electronic transitions. Using Bader charge integration algorithm interrelation between the absorption edge energy with the interlayer charge transfer has been established, where we find that larger inter-layer charge transfer shifts the absorption edge to lower photon energies. In case of NaFeAs, the interlayer charge transfer (∼0.78e) is maximum at ambient pressure, while the corresponding absorption edge is minimum. For LiFeAs, the interlayer charge transfer (∼0.49e) is minimum at 60 GPa pressure (where it becomes a semiconductor), while the absorption edge is maximum. In absence of high pressure experimental data, we have also shown that at ambient pressure our theoretical XANES spectra agree well with the available experimental data. Core-hole effect is found to have substantial effects on the absorption spectra at higher pressures.

Structural and luminescence investigations of Gd3+ - Er3+ doped in lithium aluminum borate glasses using XANES and EXAFS techniques

The typical melt quenching technique was utilized to produce a possibly unique series of Gd3+ and Er3+ dual doped borate glasses with a composition of 25Li2O–5Al2O3-XGd2O3-(69.0-X)B2O3-1.0Er2O3. The amorphous nature and information on chemical bindings of the materials were validated by using fundamental characterization techniques such as X-ray diffraction, Fourier transform infrared, X-ray absorption near-edge structure, and optical screening to identify their features (absorption, excitation, and emission). The refractive index of the glasses improves from 1.5487 to 1.628 as the concentration of Gd2O3 increases. The optical absorption spectra of Er3+ doped glasses were measured from the ultraviolet (UV) through the visible (Vis) and near infrared (NIR) ranges with varying Gd2O3 concentrations in order to determine their optical properties. This luminescence was found to be predominant in photoluminescence spectra, which were obtained at an optimum doping Gd2O3 concentration of 7.5 mol%. The impact of Er3+ doping was assessed through photoluminescence, which exhibited a broad, intense NIR band at 1537 nm ascribed to the 4I13/2 → 4I15/2 transition of Er3+ ions at λEx = 486, 526, 651, and 978 nm excitation, which exhibits outstanding increased intensity with the Er3+ concentration until it reaches 1.0 mol %. A look at visible and near-infrared optical, it is observed that LAGd7.5BEr1.0 glass is a more potential candidate for photonic devices.

Saturation magnetisation as an indicator of the disintegration of barium hexaferrite nanoplatelets during the surface functionalisation

Barium hexaferrite nanoplatelets (BHF NPLs) are permanent nanomagnets with the magnetic easy axis aligned perpendicular to their basal plane. By combining this specific property with optimised surface chemistry, novel functional materials were developed, e.g., ferromagnetic ferrofluids and porous nanomagnets. We compared the interaction of chemically different phosphonic acids, hydrophobic and hydrophilic with 1–4 phosphonic groups, with BHF NPLs. A decrease in the saturation magnetisation after functionalising the BHF NPLs was correlated with the mass fraction of the nonmagnetic coating, whereas the saturation magnetisation of the NPLs coated with a tetraphosphonic acid at 80 °C was significantly lower than expected. We showed that such a substantial decrease in the saturation magnetisation originates from the disintegration of BHF NPLs, which was observed with atomic-resolution scanning transmission electron microscopy and confirmed by a computational study based on state-of-the-art first-principles calculations. Fe K-edge XANES (X-ray absorption near-edge structure) and EXAFS (Extended X-ray absorption fine structure) combined with Fourier-transformed infrared (FTIR) spectroscopy confirmed the formation of an Fe–phosphonate complex on the partly decomposed NPLs. Comparing our results with other functionalised magnetic nanoparticles confirmed that saturation magnetisation can be exploited to identify the disintegration of magnetic nanoparticles when insoluble disintegration products are formed.

Non-bonding interaction of dual atom catalysts for enhanced oxygen reduction reaction

We demonstrate the design of graphene-supported dual atom catalysts (DACs) for the four-electron oxygen reduction reaction (ORR), by utilizing the non-bonding interaction of counterpart metals (M) that synergistically tune the electronic properties and catalytic activity of the Fe active site in FeMN6-DAC and FeMN8-DAC systems, where M stands for Fe, Co, Ni, Cu, and Zn. More specifically, for Fe-M distances below 15 Å, the non-bonding interaction is significant, making the system act as the DAC. We predicted that FeNiN6-DAC and FeNiN8-DAC exhibit a low ORR overpotential (ηORR) of 0.28 V and 0.47 V, respectively, which are at the summits of volcano plots. This low ηORR originates from the high Bader charge transfer coupled with high spin density at the Fe site in both the FeNiN6-DAC and FeNiN8-DAC systems, which weakens the adsorption of OH* intermediate while enhancing its desorption to H2O. Guided by these density functional theory (DFT) computational results, we synthesized FeCoN8-DAC and FeNiN8-DAC along with N-doped graphene and confirmed their structures with scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and electron spin resonance (ESR). We verify experimentally the catalytic activities and find that FeNiN8-DAC has the low experimental overpotential of 0.39 V with a Tafel slope of 47 mVdec−1. Based on these results, we propose a DFT-guided strategy to tune the charge transfer and spin population of the active site toward designing DACs for electrochemical ORR.

Spectromicroscopy Studies of Silicon Nanowires Array Covered by Tin Oxide Layers.

The composition and atomic and electronic structure of a silicon nanowire (SiNW) array coated with tin oxide are studied at the spectromicroscopic level. SiNWs are covered from top to down with a wide bandgap tin oxide layer using a metal-organic chemical vapor deposition technique. Results obtained via scanning electron microscopy and X-ray diffraction showed that tin-oxide nanocrystals, 20nm in size, form a continuous and highly developed surface with a complex phase composition responsible for the observed electronic structure transformation. The "one spot" combination, containing a chemically sensitive morphology and spectroscopic data, is examined via photoemission electron microscopy in the X-ray absorption near-edge structure spectroscopy (XANES) mode. The observed spectromicroscopy results showed that the entire SiNW surface is covered with a tin(IV) oxide layer and traces of tin(II) oxide and metallic tin phases. The deviation from stoichiometric SnO2 leads to the formation of the density of states sub-band in the atop tin oxide layer bandgap close to the bottom of the SnO2 conduction band. These observations open up the possibility of the precise surface electronic structures estimation using photo-electron microscopy in XANES mode.

X‐ray absorption fine structure characterization of a multicomponent spinel catalyst

AbstractDemand for high‐performing, inexpensive catalysts has motivated the development of mixed 3d transition metal architectures. Here, x‐ray spectroscopies are uniquely positioned to inform intensive searches of compositional spaces by elucidating structure–function relationships. However, thorough analyses of complex systems are often non‐trivial. In this work, one such example was pursued, a chemical series of spinel‐based emissions catalysts of the general formula Mn0.1CuxCo2.9−xO4 for 0.1 ≤ x ≤ 0.8. The local electronic and atomic structures of these materials were characterized by x‐ray absorption near edge structure (XANES) and extended x‐ray absorption fine structure (EXAFS) analyses, respectively. EXAFS analyses required models to be constructed that captured the relevant structural changes across the chemical series. Building these models required insights from XANES, x‐ray diffraction (XRD), and inductively coupled plasma atomic emission spectroscopy analyses. XANES measurements at the Co K‐edge, when complemented with ab initio multiple scattering calculations, suggested that the fraction of Co atoms in the octahedral sites of the spinel increased as the concentration of substituted Cu increased. Similarly, XANES measurements at the Mn K‐edge suggested that the occupancy of the first coordination shell varied throughout the series. Finally, the XRD results revealed an impurity, a CuO phase, formed at higher copper concentrations. This is consistent with the results of the principal component analysis performed on the Cu K‐edge XANES spectra. These hypotheses were incorporated into the EXAFS fitting models and are consistent with the subsequent quantitative analyses.

Robust NASICON-type iron-based Na4Fe3(PO4)2(P2O7) cathode for high temperature sodium-ion batteries

Iron-based mixed phosphates sodium ion batteries (SIBs) are promising sustainable storage devices due to the low-costing and non-toxicity characters. Whereas, their real application is seriously restricted by the sluggish Na+ diffusion and inferior intrinsic electronic conductivity. Herein, we propose mesoporous sponge-like structural Na4Fe3(PO4)2(P2O7) (NFPP) in-situ caged in carbon layer and cross-linked graphene nanosheets (NFPP@C@rGO), toward fast charging and highly stable sodium ion half/full cells in a wide temperature range. This rational strategy gives the cathode superior long-lasting cycling stability, specifically, 86.7 % capacity retention is retained at 20 C for over 30,000 cycles, displaying a capacity loss less than 0.00045 % per cycle. Notably, outstanding thermal stability at 60 °C is achieved and no obvious capacity degradation can be observed after cycling for 200 times at 1 C. Furthermore, the impressive electrochemical performances of full cells are determined, ascribed to the improved electronic conductivity and structural stability (e.g. a small volume change of ∼4.1 % during sodium ion insertion/deinsertion), which is confirmed by in-situ X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) measurements. All the results above prove that the NFPP@C@rGO is of high potential for advanced energy storage system based on its low costs, long-lasting cyclability and excellent thermal stability.

Carboxyl Functionalization of N-MWCNTs with Stone-Wales Defects and Possibility of HIF-1α Wave-Diffusive Delivery.

Nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) are widely used for drug delivery. One of the main challenges is to clarify their interaction with hypoxia-inducible factor 1 alpha (HIF-1α), the lack of which leads to oncological and cardiovascular diseases. In the presented study, N-MWCNTs were synthesized by catalytic chemical vapor deposition and irradiated with argon ions. Their chemical state, local structure, interfaces, Stone-Wales defects, and doping with nitrogen were analyzed by high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Using experimental data, supercells of functionalized N-MWCNTs with an oxygen content of 2.7, 4 and 6 at. % in carboxyl groups were built by quantum chemical methods. Our analysis by the self-consistent charge density functional tight-binding (SCC DFTB) method shows that a key role in the functionalization of CNTs with carboxyl groups belongs to Stone-Wales defects. The results of research in the decoration of CNTs with HIF-1α demonstrate the possibility of wave-diffusion drug delivery. The nature of hybridization and relaxation determines the mechanism of oxygen regulation with HIF-1α molecules, namely, by OH-(OH-C) and OH-(O=C) chemical bonds. The concentration dependence of drug release in the diffusion mode suggests that the best pattern for drug delivery is provided by the tube with a carboxylic oxygen content of 6 at. %.

Deciphering phase evolution in complex metal oxide thin films via high-throughput materials synthesis and characterization

Discovery of structure-property relationships in thin film alloys of complex metal oxides enabled by high-throughput materials synthesis and characterization facilities is demonstrated here with a case-study. Thin films of binary transition metal oxides (Ti–Zn) are prepared by pulsed laser deposition with continuously varying Ti:Zn ratio, creating combinatorial samples for exploration of the properties of this material family. The atomic structure and electronic properties are probed by spatially resolved techniques including x-ray absorption near edge structures (XANES) and x-ray fluorescence (XRF) at the Ti and Zn K-edge, x-ray diffraction, and spectroscopic ellipsometry. The observed properties as a function of Ti:Zn ratio are resolved into mixtures of five distinguishable phases by deploying multivariate curve resolution analysis on the XANES spectral series, under constraints set by results from the other characterization techniques. First-principles computations based on density function theory connect the observed properties of each distinct phase with structural and spectral characteristics of crystalline polymorphs of Ti–Zn oxide. Continuous tuning of the optical absorption edge as a function of Ti:Zn ratio, including the unusual observation of negative optical bowing, exemplifies a functional property of the film correlated to the phase evolution.

Manganese Luminescent Centers of Different Valence in Yttrium Aluminum Borate Crystals.

We present an extensive study of the luminescence characteristics of Mn impurity ions in a YAl3(BO3)4:Mn crystal, in combination with X-ray fluorescence analysis and determination of the valence state of Mn by XANES (X-ray absorption near-edge structure) spectroscopy. The valences of manganese Mn2+(d5) and Mn3+(d4) were determined by the XANES and high-resolution optical spectroscopy methods shown to be complementary. We observe the R1 and R2 luminescence and absorption lines characteristic of the 2E ↔&amp;nbsp;4A2 transitions in d3 ions (such as Mn4+ and Cr3+) and show that they arise due to uncontrolled admixture of Cr3+ ions. A broad luminescent band in the green part of the spectrum is attributed to transitions in Mn2+. Narrow zero-phonon infrared luminescence lines near 1060 nm (9400 cm-1) and 760 nm (13,160 cm-1) are associated with spin-forbidden transitions in Mn3+: 1T2 → 3T1 (between excited triplets) and 1T2 → 5E (to the ground state). Spin-allowed 5T2 → 5E Mn3+ transitions show up as a broad band in the orange region of the spectrum. Using the data of optical spectroscopy and Tanabe-Sugano diagrams we estimated the crystal-field parameter Dq and Racah parameter B for Mn3+ in YAB:Mn as Dq = 1785 cm-1 and B = 800 cm-1. Our work can serve as a basis for further study of YAB:Mn for the purposes of luminescent thermometry, as well as other applications.