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The development of solar fuel generating materials would greatly benefit from a molecular level understanding of the semiconductor/electrolyte interface and changes in the interface induced by an applied potential and illumination by solar light. Ambient pressure photoelectron spectroscopy techniques with both soft and hard X-rays, AP-XPS and AP-HAXPES respectively, have the potential to markedly contribute to this understanding. In this paper we initially provide two examples of current challenges in solar fuels material development that AP-XPS and AP-HAXPES can directly address. This will be followed by a brief description of the distinguishing and complementary characteristics of soft and hard X-ray AP-XPS and AP-HAXPES and best approaches to achieving monolayer sensitivity in solid/aqueous electrolyte studies. In particular we focus on the detection of surface adsorbed hydroxyl groups in the presence of aqueous hydroxide anions in the electrolyte, a common situation when investigating photoanodes for solar fuel generating applications. The paper concludes by providing an example of a combined AP-XPS and AP-HAXPES study of a semiconductor/aqueous electrolyte interface currently used in water splitting devices specifically the BiVO4/aqueous potassium phosphate electrolyte interface.

The oxidation of the aqueous H 3 PO 3 in contact with Pt was investigated for a fundamental understanding of the Pt/aqueous H 3 PO 3 interaction with the goal of providing a comprehensive basis for the further optimization of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs). Ion-exchange chromatography (IEC) experiments suggested that in ambient conditions, Pt catalyzes H 3 PO 3 oxidation to H 3 PO 4 with H 2 O. X-ray photoelectron spectroscopy (XPS) on different substrates, including Au and Pt, previously treated in H 3 PO 3 solutions was conducted to determine the catalytic abilities of selected metals toward H 3 PO 3 oxidation. In situ ambient pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) combined with the "dip-and-pull" method was performed to investigate the state of H 3 PO 3 at the Pt|H 3 PO 3 interface and in the bulk solution. It was shown that whereas H 3 PO 3 remains stable in the bulk solution, the catalyzed oxidation of H 3 PO 3 by H 2 O to H 3 PO 4 accompanied by H 2 generation occurs in contact with the Pt surface. This catalytic process likely involves H 3 PO 3 adsorption at the Pt surface in a highly reactive pyramidal tautomeric configuration.

We present a new technique for investigating complex model electrocatalysts by means of electrochemical in situ ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). Using a specially designed miniature capillary device, we prepared a three-electrode electrochemical cell in a thin-layer configuration and analyzed the active electrode/electrolyte interface by using "tender" X-ray synchrotron radiation. We demonstrate the potential of this versatile method by investigating a complex model electrocatalyst. Specifically, we monitored the oxidation state of Pd nanoparticles supported on an ordered Co 3 O 4 (111) film on Ir(100) in an alkaline electrolyte under potential control. We found that the Pd oxide formed in the in situ experiment differs drastically from the one observed in an ex situ emersion experiment at similar potential. We attribute these differences to the decomposition of a labile palladium oxide/hydroxide species after emersion. Our experiment demonstrates the potential of our approach and the importance of electrochemical in situ AP-XPS for studying complex electrocatalytic interfaces.

We present a combined computational and experimental study of the adsorption of water on the Mo-doped BiVO 4 (010) surface, revealing how excess electrons influence the dissociation of water and lead to hydroxyl-induced alterations of the surface electronic structure. By comparing ambient pressure resonant photoemission spectroscopy (AP-ResPES) measurements with the results of first-principles calculations, we show that the dissociation of water on the stoichiometric Mo-doped BiVO 4 (010) surface stabilizes the formation of a small electron polaron on the VO 4 tetrahedral site and leads to an enhanced concentration of localized electronic charge at the surface. Our calculations demonstrate that the dissociated water accounts for the enhanced V 4+ signal observed in ambient pressure X-ray photoelectron spectroscopy and the enhanced signal of a small electron polaron inter-band state observed in AP-ResPES measurements. For ternary oxide surfaces, which may contain oxygen vacancies in addition to other electron-donating dopants, our study reveals the importance of defects in altering the surface reactivity toward water and the concomitant water-induced modifications to the electronic structure.

The spatial distribution and concentration of lanthanide activator and sensitizer dopant ions are of key importance for the luminescence color and efficiency of upconverting nanoparticles (UCNPs). Quantifying dopant ion distributions and intermixing, and correlating them with synthesis methods require suitable analytical techniques. Here, X-ray photoelectron spectroscopy depth-profiling with tender X-rays (2000-6000 eV), providing probe depths ideally matched to UCNP sizes, is used to measure the depth-dependent concentration ratios of Er 3+ to Yb 3+ , [Er 3+ ]/[Yb 3+ ], in three types of UCNPs prepared using different reagents and synthesis methods. This is combined with data simulations and inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements of the lanthanide ion concentrations to construct models of the UCNPs' dopant ion distributions. The UCNP sizes and architectures are chosen to demonstrate the potential of this approach. Core-only UCNPs synthesized with XCl 3 ·6H 2 O precursors (β-phase) exhibit a homogeneous distribution of lanthanide ions, but a slightly surface-enhanced [Er 3+ ]/[Yb 3+ ] is observed for UCNPs prepared with trifluroacetate precursors (α-phase). Examination of Yb-core@Er-shell UCNPs reveals a co-doped, intermixed region between the single-doped core and shell. The impact of these different dopant ion distributions on the UCNP's optical properties is discussed to highlight their importance for UCNP functionality and the design of efficient UCNPs., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

The organic component (methylammonium) of CH 3 NH 3 PbI 3- x Cl x -based perovskites shows electronic hybridization with the inorganic framework via H-bonding between N and I sites. Femtosecond dynamics induced by core excitation are shown to strongly influence the measured X-ray emission spectra and the resonant inelastic soft X-ray scattering of the organic components. The N K core excitation leads to a greatly increased N-H bond length that modifies and strengthens the interaction with the inorganic framework compared to that in the ground state. The study indicates that excited-state dynamics must be accounted for in spectroscopic studies of this perovskite solar cell material, and the organic-inorganic hybridization interaction suggests new avenues for probing the electronic structure of this class of materials. It is incidentally shown that beam damage to the methylamine component can be avoided by moving the sample under the soft X-ray beam to minimize exposure and that this procedure is necessary to prevent the creation of experimental artifacts.

The application of bismuth vanadate (BiVO 4 ) photoelectrodes for solar water splitting is hindered by the poor carrier transport. To overcome this, multiple donor-doping strategies (e.g. dual doping, gradient doping) have been explored. Here, we show for the first time the successful introduction of calcium (Ca) as an acceptor-type dopant into BiVO 4 photoelectrodes. Interestingly, instead of generating cathodic photocurrents, the Ca-doped BiVO 4 photoelectrodes show anodic photocurrents with an enhanced carrier separation efficiency. Hard X-ray photoelectron spectroscopy (HAXPES) shows that this enhancement is caused by out-diffusion of Ca during the deposition process, which spontaneously creates a p-n junction within the BiVO 4 layer. Overall, a significant two-fold improvement of the AM1.5 photocurrent is obtained upon Ca-doping. This study highlights the importance of controlled doping beyond simply modifying carrier concentration and may enable new device architectures in photoelectrode materials., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The purposes of this study were to describe primary tooth emergence in an American Indian (AI) population during the first 36 mo of life to compare 1) patterns of emergence between male and female children and 2) tooth emergence between these AI children and other U.S. ethnic groups. Data were derived from a birth cohort of 239 AI children from a Northern Plains tribe participating in a longitudinal study of early childhood caries, with examination data at target ages of 8, 12, 16, 22, 28, and 36 mo of age (±1 mo). Patterns of emergence in AI children were characterized and sex comparisons accomplished with interval-censored survival methodology. Numbers of erupted teeth in AI children at each age were compared via Kruskal-Wallis tests against those in children of the same age, as drawn from a cross-sectional study of dental caries patterns in Arizona; these comparisons were based on the dental examinations of 547 White non-Hispanic and 677 Hispanic children. Characterization of time to achievement of various milestones-including emergence of the anterior teeth, the first molars, and the complete primary dentition-provided no evidence of sex differences among AI children. AI children had significantly more teeth present at 8 mo (median, 3) than either White non-Hispanic ( P < 0.0063) or Hispanic ( P < 0.0001) children (median, 2 each). This was also true at 12 mo ( P < 0.001; medians, 8 vs. 6 and 7, respectively) and 16 mo ( P < 0.001; medians, 12 vs. 11 each). Less pronounced differences were seen at 22 mo ( P < 0.0001). White non-Hispanic and Hispanic children did not differ at any time considered ( P > 0.05). These results provide evidence of earlier tooth emergence in AI children than in the other 2 ethnicities. Although the underlying etiology of the severity of early childhood caries in AI children is likely to be multifactorial, earlier tooth emergence may be a contributing factor. Knowledge Transfer Statement: The findings of this study have practical implications for practitioners providing childhood oral health care to ethnic groups with early tooth emergence. It may be important to provide parents with information on toothbrushing, dentist visits, and other practices supportive of good oral health as early as possible to protect their children's primary dentition., Competing Interests: The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.

Bismuth vanadate has recently drawn significant research attention as a light-absorbing photoanode due to its performance for photoelectrochemical water splitting. In this study, we use in situ ambient pressure X-ray photoelectron spectroscopy with "tender" X-rays (4.0 keV) to investigate a polycrystalline bismuth vanadate (BiVO 4 ) electrode in contact with an aqueous potassium phosphate (KPi) solution at open circuit potential under both dark and light conditions. This is facilitated by the creation of a 25 to 30 nm thick electrolyte layer using the "dip-and-pull" method. We observe that under illumination bismuth phosphate forms on the BiVO 4 surface leading to an increase of the surface negative charge. The bismuth phosphate layer may act to passivate surface states observed in photoelectrochemical measurements. The repulsive interaction between the negatively charged surface under illumination and the phosphate ions in solution causes a shift in the distribution of ions in the thin aqueous electrolyte film, which is observed as an increase in their photoelectron signals. Interestingly, we find that such changes at the BiVO 4 /KPi electrolyte interface are reversible upon returning to dark conditions. By measuring the oxygen 1s photoelectron peak intensities from the phosphate ions and liquid water as a function of time under dark and light conditions, we determine the time scales for the forward and reverse reactions. Our results provide direct evidence for light-induced chemical modification of the BiVO 4 /KPi electrolyte interface.

We have employed soft and hard X-ray photoelectron spectroscopies to study the depth-dependent chemical composition of mixed-halide perovskite thin films used in high-performance solar cells. We detect substantial amounts of metallic lead in the perovskite films, which correlate with significant density of states above the valence band maximum. The metallic lead content is higher in the bulk of the perovskite films than at the surface. Using an optimized postanneal process in air, we can reduce the metallic lead content in the perovskite film. This process reduces the amount of metallic lead and a corresponding increase in the photoluminescence quantum efficiency of the perovskite films can be observed. This correlation indicates that metallic lead impurities are likely a key defect whose concentration can be controlled by simple annealing procedures in order to increase the performance for perovskite solar cells.

Background: Severe-early childhood caries (S-ECC) is one of the most common infectious diseases in children and is prevalent in lower socio-economic populations. American Indian children suffer from the highest levels of S-ECC in the United States. Members of the mutans streptococci, Streptococcus mutans, in particular, are key etiologic agents in the development of caries. Children typically acquire S. mutans from their mothers and early acquisition is often associated with higher levels of tooth decay., Methods: We have conducted a 5-year birth cohort study with a Northern Plains Tribe to determine the temporality and fidelity of S. mutans transmission from mother to child in addition to the genotypic diversity of S. mutans in this community. Plaque samples were collected from 239 mother/child dyads at regular intervals from birth to 36 months and S. mutans were isolated and genotyped by arbitrarily primed-polymerase chain reaction (AP-PCR)., Results: Here we present preliminary findings from a subset of the cohort. The focus for this paper is on initial acquisition events in the children. We identified 17 unique genotypes in 711 S. mutans isolates in our subset of 40 children, 40 mothers and 14 primary caregivers. Twelve of these genotypes were identified in more than one individual. S. mutans colonization occurred by 16 months in 57.5% of the children and early colonization was associated with higher decayed, missing and filled surface (DMFS) scores (p=0.0007). Children colonized by S. mutans shared a common genotype with their mothers 47.8% of the time. While multiple genotypes were common in adults, only 10% of children harbored multiple genotypes., Conclusion: These children acquire S. mutans at an earlier age than the originally described 'window of infectivity' and often, but not exclusively, from their mothers. Early acquisition is associated with both the caries status of the children and the mothers.

Exsolution reactions enable the synthesis of oxide-supported metal nanoparticles, which are desirable as catalysts in green energy conversion technologies. It is crucial to precisely tailor the nanoparticle characteristics to optimize the catalysts' functionality, and to maintain the catalytic performance under operation conditions. We use chemical (co)-doping to modify the defect chemistry of exsolution-active perovskite oxides and examine its influence on the mass transfer kinetics of Ni dopants towards the oxide surface and on the subsequent coalescence behavior of the exsolved nanoparticles during a continuous thermal reduction treatment. Nanoparticles that exsolve at the surface of the acceptor-type fast-oxygen-ion-conductor SrTi0.95Ni0.05O3−δ (STNi) show a high surface mobility leading to a very low thermal stability compared to nanoparticles that exsolve at the surface of donor-type SrTi0.9Nb0.05Ni0.05O3−δ (STNNi). Our analysis indicates that the low thermal stability of exsolved nanoparticles at the acceptor-doped perovskite surface is linked to a high oxygen vacancy concentration at the nanoparticle-oxide interface. For catalysts that require fast oxygen exchange kinetics, exsolution synthesis routes in dry hydrogen conditions may hence lead to accelerated degradation, while humid reaction conditions may mitigate this failure mechanism. Exsolved metal nanoparticles are widely believed to exhibit an exceptional robustness against coarsening. Here, the authors demonstrate that the coarsening behavior depends on the surface defect chemistry of the respective oxide support as well as the oxophilicity of the exsolved metal. [ABSTRACT FROM AUTHOR]

Highlights: A multiscale hierarchical structure design, integrating wrinkled MXene radar-infrared shielding layer and flexible Fe3O4@C/PDMS microwave absorption layer The assembled stealth devices realize a near-perfect stealth capability in both X-band (8-12 GHz) and long-wave infrared (8-14 µm) wavelength ranges. The optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s). Developing advanced stealth devices to cope with radar-infrared (IR) fusion detection and diverse application scenarios is increasingly demanded, which faces significant challenges due to conflicting microwave and IR cloaking mechanisms and functional integration limitations. Here, we propose a multiscale hierarchical structure design, integrating wrinkled MXene IR shielding layer and flexible Fe3O4@C/PDMS microwave absorption layer. The top wrinkled MXene layer induces the intensive diffuse reflection effect, shielding IR radiation signals while allowing microwave to pass through. Meanwhile, the permeable microwaves are assimilated into the bottom Fe3O4@C/PDMS layer via strong magneto-electric synergy. Through theoretical and experimental optimization, the assembled stealth devices realize a near-perfect stealth capability in both X-band (8–12 GHz) and long-wave infrared (8–14 µm) wavelength ranges. Specifically, it delivers a radar cross-section reduction of − 20 dB m2, a large apparent temperature modulation range (ΔT = 70 °C), and a low average IR emissivity of 0.35. Additionally, the optimal device demonstrates exceptional curved surface conformability, self-cleaning capability (contact angle ≈ 129°), and abrasion resistance (recovery time ≈ 5 s). This design strategy promotes the development of multispectral stealth technology and reinforces its applicability and durability in complex and hostile environments. [ABSTRACT FROM AUTHOR]

Heterogeneous chemical reactions at vapor/solid interfaces play an important role in many processes in the environment and technology. Ambient pressure X-ray photoelectron spectroscopy (APXPS) is a valuable tool to investigate the elemental composition and chemical specificity of surfaces and adsorbates on the molecular scale at pressures of up to 130 mbar. In this review we summarize the historical development of APXPS since its introduction over forty years ago, discuss different approaches to minimize scattering of electrons by gas molecules, and give a comprehensive overview about the experimental systems (vapor/solid interfaces) that have been studied so far. We also present several examples for the application of APXPS to environmental science, heterogeneous catalysis, and electrochemistry.

A comprehensive optical design for a high-resolution, high-flux, wide-energy range, micro-focused beamline working in the vacuum ultraviolet and soft x-ray photon energy range is proposed. The beamline is to provide monochromatic radiation to three photoelectron microscopes: a full-field x-ray photoelectron emission microscope and two scanning instruments, one dedicated to angle resolved photoemission spectroscopy (μ-ARPES) and one for ambient pressure x-ray photoelectron spectroscopy and scanning photoelectron microscopy (AP-XPS/SPEM). Microfocusing is achieved with state of the art elliptical cylinders, obtaining a spot size of 1 μm for ARPES and 0.5 μm for AP-XPS/SPEM. A detailed ray tracing analysis quantitatively evaluates the overall beamline performances.

Using a combination of X-ray photoemission and near-edge X-ray absorption spectroscopy (NEXAFS) as well as density-functional theory (DFT), we have investigated the adsorption of acetone on ice in the temperature range from 218 to 245 K. The adsorption enthalpy determined from experiment (45 kJ mol(-1)) agrees well with the adsorption energy predicted by theory (41 to 44 kJ mol(-1)). Oxygen K-edge NEXAFS spectra indicate that the presence of acetone at the ice surface does not induce the formation of a pre-melted layer at temperatures up to 243 K. DFT calculations show that the energetically most favored adsorption geometry for acetone on ice is with the molecular plane almost parallel to the surface.

We report an x-ray photoelectron spectroscopy study of the oxidation of Al(111) surfaces at room temperature, which reveals that the limiting thickness of an aluminum oxide film can be tuned by using oxygen pressure. This behavior is attributed to a strong dependence of the kinetic potential on the oxygen gas pressure. The coverage of oxygen anions on the surface of the oxide film depends on the gas pressure leading to a pressure dependence of the kinetic potential. Our results indicate that a significantly large oxygen pressure (>1  Torr) is required to develop the saturated surface coverage of oxygen ions, which results in the maximum kinetic potential and therefore the saturated limiting thickness of the oxide film.

We discuss a new approach for the measurement of the surfaces of free aerosol particles with diameters from 50 to 1000 nm. Particles in this size range have significant influence on the heterogeneous chemistry in the atmosphere and affect human health. Interfacing an aerodynamic lens to an ambient pressure x-ray photoelectron spectrometer permits measurement of the surface chemical composition of unsupported aerosol particles in real time. We discuss the basic considerations for the design of such an instrument, its current limitations and potentials for improvement. Results from a proof-of-principle experiment on silicon oxide particles with average diameters of 270 nm are shown.

X-Ray photoemission spectroscopy operating under ambient pressure conditions is used to probe ion distributions throughout the interfacial region of a free-flowing aqueous liquid micro-jet of 6 M potassium fluoride. Varying the energy of the ejected photoelectrons by carrying out experiments as a function of X-ray wavelength measures the composition of the aqueous-vapor interfacial region at various depths. The F(-) to K(+) atomic ratio is equal to unity throughout the interfacial region to a depth of 2 nm. The experimental ion profiles are compared with the results of a classical molecular dynamics simulation of a 6 M aqueous KF solution employing polarizable potentials. The experimental results are in qualitative agreement with the simulations when integrated over an exponentially decaying probe depth characteristic of an APPES experiment. First principles molecular dynamics simulations have been used to calculate the potential of mean force for moving a fluoride anion across the air-water interface. The results show that the fluoride anion is repelled from the interface, consistent with the depletion of F(-) at the interface revealed by the APPES experiment and polarizable force field-based molecular dynamics simulation. Together, the APPES and MD simulation data provide a detailed description of the aqueous-vapor interface of alkali fluoride systems. This work offers the first direct observation of the ion distribution at an aqueous potassium fluoride solution interface. The current experimental results are compared to those previously obtained for saturated solutions of KBr and KI to underscore the strong difference in surface propensity between soft/large and hard/small halide ions in aqueous solution.

Using atomic beam/surface scattering measurements to investigate the desorption kinetics of low-coverage Pb from Mo(100), we uncover a large entropy difference between Pb atoms at terrace and step sites, which should be general for adsorbates on surfaces at high temperatures. A line shape analysis of the transient desorption signal reveals the presence of two species with different lifetimes on the surface. An Arrhenius analysis of these lifetimes from 1150 to 1320 K provides the prefactors and desorption activation energies (332 and 411 kJ/mol) of these two states. A comparison of these energies to those measured directly via adsorption calorimetry strongly suggests that one state is a terrace-bound species. The other, more strongly bound species is attributed to steps. The more strongly bound step species has the higher rate constant for desorption because of its much larger desorption prefactor (9 x 10 (19) vs 5 x 10 (15) s (-1)). Within transition state theory, the ratio of these prefactors corresponds to 82 J/(mol K) higher entropy for the terrace species than for the step species. This large entropy difference is quantitatively reproduced by a simple model which assumes the terrace species is a 2D ideal gas parallel to the surface and the step species is a 1D ideal gas along the step edges. Such a difference will generally exist for adsorbed species when k B T exceeds the barrier height for adsorbate diffusion across terraces. A consequence of this large entropy difference is that the defect sites are much less populated relative to terrace sites than would be expected based on enthalpy alone. The measured prefactor for Pb desorption was used to analyze earlier surface lifetime measurements for Pb on MgO(100) to extract adsorption energies for that system, as well.

We describe a combined ambient pressure photoelectron spectroscopy/droplet train apparatus for investigating the nature and heterogeneous chemistry of liquid/vapor interfaces. In this instrument a liquid droplet train with typical droplet diameters from 50-150 mum is produced by a vibrating orifice aerosol generator (VOAG). The droplets are irradiated by soft X-rays (100-1500 eV) in front of the entrance aperture of a differentially pumped electrostatic lens system that transfers the emitted electrons into a conventional hemispherical electron analyzer. The photoemission experiments are performed at background pressures of up to several Torr, which allows the study of environmentally important liquid/vapor interfaces, in particular aqueous solutions, under equilibrium conditions. The exposure time of the droplet surface to the background gases prior to the XPS measurement can be varied, which will allow future kinetic measurements of gas uptake on liquid surfaces. As an example, a measurement of the surface composition of a chi = 0.21 aqueous methanol solution is presented. The concentration of methanol at the vapor/liquid interface is enhanced by a factor of about 3 over the bulk value, while the expected bulk value is recovered at depths larger than about 1.5 nm.

Combining scanning tunneling microscopy (STM), IR reflection absorption spectroscopy (IRAS) and molecular beam (MB) techniques, we have investigated particle size effects on a Pd/Fe(3)O(4) model catalyst. We focus on the particle size dependence of (i) CO adsorption, (ii) oxygen adsorption and (iii) Pd nanoparticle oxidation/reduction. The model system, which is based on Pd nanoparticles supported on an ordered Fe(3)O(4) film on Pt(111), is characterized in detail with respect to particle morphology, nucleation, growth and coalescence behavior of the Pd particles. Morphological changes upon stabilization by thermal treatment in oxygen atmosphere are also considered. The size of the Pd particles can be varied roughly between 1 and 100 nm. The growth and morphology of the Pd particles on the Fe(3)O(4)/Pt(111) film were characterized by STM and IRAS of adsorbed CO as a probe molecule. It was found that very small Pd particles on Fe(3)O(4) show a strongly modified adsorption behavior, characterized by atypically weak CO adsorption and a characteristic CO stretching frequency around 2130 cm(-1). This modification is attributed to a strong interaction with the support. Additionally, the kinetics of CO adsorption was studied by sticking coefficient experiments as a function of particle size. For small particles it is shown that the CO adsorption rate is significantly enhanced by the capture zone effect. The absolute size of the capture zone was quantified on the basis of the STM and sticking coefficient data. Finally, oxygen adsorption was studied by means of MB CO titration experiments. Pure chemisorption of oxygen is observed at 400 K, whereas at 500 K partial oxidation of the particles occurs. The oxidation behavior reveals strong kinetic hindrances to oxidation for larger particles, whereas facile oxidation and reduction are observed for smaller particles. For the latter, estimates point to the formation of oxide layers which, on average, are thicker than the surface oxides on corresponding single crystal surfaces.

Because of their quantum confinement effects and adjustable features, semiconductor nanoparticles have attracted a lot of attention for their various uses in optoelectronic devices. This study investigates how size and shape variations affect the optoelectronic properties of semiconductor nanoparticles InX (X = As, Sb, and P). Using unified thermodynamics modeling, it explores the effects of these nanoparticles' diameters on their electronic band structures, optical properties, and charge carrier dynamics. The inquiry focuses on InX nanoparticles with different sizes and nanostructure morphologies. By examining electronic band structures, the density of states, and optical absorption spectra, the size-dependent quantum confinement processes that govern the optical band gap transitions and excitonic behaviors in these semiconductor nanoparticles were made clear. Also, the influence of the shape of the nanoparticles on carrier mobility and electronic band alignment is investigated, offering insights into the possibility of controlling the morphology to customize optoelectronic capabilities. This theoretical analysis indicates that altering the optoelectronic properties of InX semiconductor nanoparticles is mostly dependent on their size and shape. Smaller nanoparticles show stronger quantum size effects, which lead to improved exciton confinement and blue shifts in the optical absorption spectra. Shape-dependent differences in the density of states and electronic band structures indicate the impact of morphology on the dynamics and recombination of charge carriers in the nanoparticles. In conclusion, this work provides important insights for the design and optimization of semiconductor nanomaterials for photovoltaic, sensing, and light-emitting applications by thoroughly examining the impact of size and shape on the optoelectronic properties of InX semiconductor nanoparticles. [ABSTRACT FROM AUTHOR]

Calorimetric measurements of metal adsorption energies directly provide the energies of metal atoms in supported metal nanoparticles. As the metal coverage increases, the particles grow, revealing the dependence of this energy on particle size, which is found to be much stronger than predicted with the usual Gibbs-Thompson relation. It is shown that this knowledge is crucial to accurately model long-term sintering rates of metal nanoparticles in catalysts.

The calormetically measured heats of adsorption of Cu, Ag, and Pb on MgO(100), previously measured in our group, are correlated with bulk properties of the metals and their sticking probabilities and film morphologies. The low-coverage heats of adsorption (when the metals are mainly in two-dimensional (2D) islands) are used to estimate metal-MgO(100) bond energies within a pairwise bond additivity model. These values correlate well with the observed initial sticking probabilities and saturation island densities of the metals. This supports a transient mobile precursor model for adsorption. The values also correlate with their bulk sublimation energies, which suggests that covalent metal-Mg bonding dominates the interaction at low coverage, probably due to very strong bonding at defects. The heats of adsorption integrated up to multilayer coverages provide the metal-MgO(100) adhesion energies and metal-MgO(100) bond energies for metals in 3D films. These values correlate with the sum of magnitudes of the metal's bulk sublimation energy plus the heat of formation of the bulk oxide of the metal per mole of metal atoms. This suggests that local chemical bonds, both metal-oxygen and covalent metal-Mg, dominate the interfacial bonding for 3D films.

The first direct calorimetric measurements of the energetics of metal film growth on a semiconductor surface are presented. The heat of adsorption of Ag on Si(100)-(2 x 1) at 300 K decreases from approximately 347 to 246 kJ/mol with coverage in the first monolayer (ML) due to overlap of substrate strain from nearby Ag islands. It then rises quickly toward the bulk sublimation enthalpy (285 kJ/mol) as 3D particles grow. A wetting layer grows to 1.0 ML, but is metastable above approximately 0.55 ML and dewets when kinetics permit. This may be common when adsorbate islands induce a large strain in the substrate surface nearby.

Bimetallic catalysts combining precious and earth-abundant metals in well designed nanoparticle architectures can enable cost efficient and stable heterogeneous catalysis. Here, we present an interaction-driven in-situ approach to engineer finely dispersed Ni decorated Pt nanoparticles (1-6 nm) on perovskite nanofibres via reduction at high temperatures (600-800 oC). Deposition of Pt (0.5 wt%) enhances the reducibility of the perovskite support and promotes the nucleation of Ni cations via metal-support interaction, thereafter the Ni species react with Pt forming alloy nanoparticles, with the combined processes yielding smaller nanoparticles that either of the contributing processes. Tuneable uniform Pt-Ni nanoparticles are produced on the perovskite surface, yielding reactivity and stability surpassing 1 wt.% Pt/γ-Al2O3 catalysts for CO oxidation. This approach heralds the possibility of in-situ fabrication of supported bimetallic nanoparticles with engineered compositional distributions and performance. Utilizing "Chemistry at a point", Ni is exsolved from a perovskite lattice under deposited Pt nanoparticles. This yields even smaller Ni Pt alloy nanoparticles on a perovskite nanofiber structure, exhibiting high catalytic activity. [ABSTRACT FROM AUTHOR]

Reaction intermediates buried within a solid-liquid interface are difficult targets for physiochemical measurements. They are inherently molecular and locally dynamic, while their surroundings are extended by a periodic lattice on one side and the solvent dielectric on the other. Challenges compound on a metal-oxide surface of varied sites and especially so at its aqueous interface of many prominent reactions. Recently, phenomenological theory coupled with optical spectroscopy has become a more prominent tool for isolating the intermediates and their molecular dynamics. The following article reviews three examples of the SrTiO3-aqueous interface subject to the oxygen evolution from water: reaction-dependent component analyses of time-resolved intermediates, a Fano resonance of a mode at the metal-oxide–water interface, and reaction isotherms of metastable intermediates. The phenomenology uses parameters to encase what is unknown at a microscopic level to then circumscribe the clear and macroscopically tuned trends seen in the spectroscopic data. [ABSTRACT FROM AUTHOR]

The nature of catalysis has been hotly pursued for over a century, and current research is focused on understanding active centers and their electronic structures. Herein, the concept of conductive catalysis is proposed and verified by theoretical simulations and experimental observations. Metallic systems containing buried catalytically active transitional metals and exposed catalytically inert main group metals are constructed, and the electronic interaction between them via metallic bonding is disclosed. Through the electronic interaction, the catalytic properties of subsurface transitional metals (Pd or Rh) can be transferred to outermost main group metals (Al or Mg) for several important transformations like semi-hydrogenation, Suzuki-coupling and hydroformylation. The catalytic force is conductive, in analogy with the magnetic force and electrostatic force. The traditional definition of active centers is challenged by the concept of conductive catalysis and the electronic nature of catalysis is more easily understood. It might provide new opportunities for shielding traditional active centers against poisoning or leaching and allow for precise regulation of their catalytic properties by the conductive layer. [ABSTRACT FROM AUTHOR]

Room-temperature growth of oxide layers on aluminum in highly diluted mixtures of oxygen with argon (O2 molar fractions 20 ppm ≤ x O 2 ≤ 500 ppm, partial pressures 2 Pa ≤ p O 2 ≤ 50 Pa) flowing through a dielectric-barrier discharge (DBD) reactor is studied, including oxidation in the pre- and post-discharge regions (PrD, PoD) adjacent to the main DBD. Three different mechanisms of plasma-enhanced oxidation were found to prevail, depending on the location of the sample: (1) In the close PrD region, up to 1 cm upstream from the discharge, accelerated growth of Al2O3 is due to the irradiation of the sample surface by highly energetic (9.8 eV) argon excimer radiation in the presence of O2. (2) In the remote PoD, a few cm downstream from the DBD, oxidation can largely be attributed to oxygen atoms, with number densities typically between 1 and 5 × 1014 cm−3. Here, analysis in terms of Cabrera–Mott (CM) theory results in CM potentials between − 1.5 and − 2.1 V. (3) In the DBD itself both O atoms and VUV photons generally play an important role but, under special conditions, an additional oxidation mode can be identified, characterized by a much larger limiting thickness: While, in general, oxide growth by O atoms and/or VUV photons virtually stops at thicknesses X between 5 and 6 nm, much thicker oxide films can be achieved in the downstream region of the main DBD, with thicknesses growing with the length of the DBD zone. Tentatively, we attribute this observation to negative oxygen ions Om− (1 ≤ m ≤ 3) accumulating in the gas while passing the reactor. Any direct electrical effects of the discharge process on the oxidation can probably be neglected. [ABSTRACT FROM AUTHOR]

The technology known as carbon capture and storage (CCS) can significantly reduce greenhouse gas emissions on a massive scale. The whole process and large-scale CCS projects are still in the exploratory stage from project demonstration stage to commercialization stage because to the significant expenditure, prolonged operating term, and numerous technological connections involved. The investment cost of CCS, the advancement of CCS technology, and the safety of CCS operation are its primary points of emphasis. There are several ways to successfully absorb carbon dioxide (CO2), but they all have the drawback of having large investment costs. For the smooth development of capturing technology, the issues of cost and efficiency must be resolved. Transporting CO2 is usually necessary since its source and storage location are dispersed and far apart. This is seen to be the most challenging issue. The secret to ensuring the success of CCS projects is understanding how to perform efficient economic evaluation when making investment decisions in light of the high cost of CCS. The influence of measures like increased carbon taxes and government subsidies will hasten the commercialization of CCS projects. We advise a thorough assessment of CCS projects to support their strategic positioning with nations and investors and deepen decision-makers' understanding of the technical feasibility and economics of CCS projects to obtain a more thorough support. This recommendation is based on the progress and challenges in the development of each module. [ABSTRACT FROM AUTHOR]

A series of La1−xSrxTO3-δ (T = Fe, Co, Ni) with different elements at B-site and Ba1−xSrxCoO3-δ doped with Sr at A-site were prepared by sol–gel method. The samples were tested by synchronous thermal analyzer in air, and the effects of calcination temperature, B-site element type, Sr doping amount on the synthesis and thermal chemical energy storage performance of perovskite oxides were investigated. Through the experiment, we obtained the following main conclusions. (1) In the series of perovskite oxides studied in this article, the higher the calcination temperature required to prepare the samples, the higher the purity and crystallinity of the samples. The samples prepared at higher calcination temperature showed better cycle stability and reversibility in the redox reaction process. (2) La1−xSrxNiO3-δ samples were not applicable to thermochemical energy storage system. In La1−xSrxFeO3-δ samples, La0.1Sr0.9FeO3-δ exhibited the best energy storage effect. However, compared with La1−xSrxCoO3-δ samples, Co-based perovskite oxide exhibited more advantages as energy storage materials for thermochemical energy storage systems. (3) BaCoO3 with single phase needed to be doped with Sr at the A-site to improve its structural stability. Sr doping reduced the molecular weight of BaCoO3 and increased the energy storage density per unit mass of samples. Energy storage performance of Ba1−xSrxCoO3-δ samples were the better in a series of A1−xSrxTO3-δ (A = La, Ba, T = Co, Fe, Ni). When Sr doping amount was 0.5, the sample possessed the best energy storage performance. [ABSTRACT FROM AUTHOR]

One of the significant drawbacks of the Direct Methanol Fuel Cells is the overpotential for the methanol oxidation reaction, which strongly limits the efficiency of this fuel cell. Furthermore, CO poisoning of Pt is considered to be a severe problem for these devices. In this work, electrocatalysts with suitable properties and outstanding performance have been developed for the oxidation reaction of methanol. PtCu and PtCuRu type materials have been synthesized through a relatively uncomplex, fast, highly reproducible, and easily scalable method. In turn, these materials have been subjected to a selective chemical dissolution process to enrich their surface with a higher density of active sites and surface defects. Evidence of alloy formation was found, specifically through XPS measurements on Ru 3d level. Besides, it was observed that with the trimetallic catalysts, which contain not only Cu but also Ru, the onset of CO electrooxidation is substantially reduced. Moreover, the leaching treatment further improves this value. This same trend was observed in the evaluation of methanol oxidation. Regarding the specific and mass activities, PtCuRu-le exhibits almost 240% and 195% higher SA and MA than commercial Pt, respectively. [ABSTRACT FROM AUTHOR]