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We present the photoelectrochemical (PEC) water-splitting properties of pristine and reduced graphene oxide (rGO)-coated GaN nanocolumns (NCs) on flexible niobium (Nb) metal foils. The structural, optical, and electronic structure analyses of rGO-coated GaN-NCs on Nb foils revealed the formation of a rGO/GaN-NCs hybrid structure. Further, the valence-band studies of pure GaN-NCs shows valence-band maxima at ∼3.0 eV below the Fermi level, which decreased to ∼2.8 eV for rGO/GaN-NCs. The PEC measurement performed on pristine GaN-NCs under standard (1 Sun) conditions shows an effective photocatalytic nature with a photocurrent density of ∼60 μA/cm2 at 0.8 V (vs Ag/AgCl) in a 1 M oxalic acid electrolyte, which increases to ∼110 μA/cm2 for rGO/GaN-NCs. The efficient PEC characteristics of rGO/GaN-NCs are attributed to the effective charge separation/transport of photogenerated carriers. Furthermore, transient photocurrent measurement reveals that hybrid and pristine GaN-NCs on flexible metal foil have a fast and stable photoresponse in an aqueous solution. The development of a hybrid nitride nanostructure-based PEC device on flexible metal foils paves the way toward developing scalable PEC devices for hydrogen production applications. [ABSTRACT FROM AUTHOR]

Conducting polymers such as poly-(3,4-ethylenedioxythiophene) (PEDOT) are widely researched for application in electronic devices. Researcher's look to exploit the ability of these polymers to conduct electrical charge. To induce conductivity, the polymers are doped with counterions; for PEDOT, this is typically done with poly-(styrenesulfonate) or tosylate (Tos). The Tos anions inserted within the PEDOT nanostructure stabilize positive defects (holes) on the polymer's conjugated backbone, which, in turn, facilitates electrical conduction. In this study, we use X-ray photoelectron spectroscopy to investigate the Tos doping of PEDOT within the outermost region (<15 nm) of electrochemically oxidized or reduced PEDOT:Tos nanoscale films. Computation of the predicted density of states from density functional theory studies is also conducted to aid in interpreting the ultraviolet photoelectron spectroscopy spectra. We observe that the doping of PEDOT:Tos is more complex than first thought, likely involving the nonionic triblock copolymer used during PEDOT's oxidative polymerization. This hypothesis is corroborated by time-of-flight secondary-ion mass spectrometry measurements on the outer 2 nm of the oxidized and reduced PEDOT:Tos. The observation of complex and heightened doping near the surface opens opportunities for the deliberate surface engineering of PEDOT:Tos nanofilms in polymer electronic applications such as electrochemical transistors and electrical connections. [ABSTRACT FROM AUTHOR]

This paper describes the development and provides comparisons of thiolated (−SH) and unthiolated Ag–Al–Si–O xerogels for iodine gas capture. These xerogels were produced from alkoxides and then heat-treated at 350 °C to provide mechanical strength for subsequent processing steps. Then, a portion of the xerogels was thiolated using (3-mercaptopropyl)-trimethoxysilane. Next, thiolated and unthiolated batches were ion-exchanged in AgNO3 solutions where Ag+ replaced Na+ in the gel network on a near 1:1 molar basis. Subsamples of the Ag-exchanged xerogels were subjected to a reduction step in H2/Ar to convert Ag+ to Ag0 where the rest of the Ag-exchanged (Ag+) were not reduced. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy revealed nanoscale Ag0 in the Ag+ samples despite no active reduction where actively reduced samples had bimodal Ag0 distribution of ∼2–3 nm hexagonal and ∼6–7 nm cubic crystallites. Synchrotron X-ray absorption spectroscopy was used to assess the oxidization states of Ag, S, and I within the different xerogel samples. The specific surface areas of the base xerogels decreased as subsequent treatments were performed on the as-made samples, albeit the decreases were smaller than aerogel equivalents of these samples from a previous study. All iodine-loaded Ag-based samples showed a mixture of β-AgI and γ-AgI. Comparisons of iodine-loading results with other Ag-based iodine sorbents show that the thiolated Ag0-xerogels in this work have one of the highest iodine-loading capacities (qe) reported to date in saturated conditions with the thiolated Ag0-xerogel showing 522 mg iodine per g of the sorbent. [ABSTRACT FROM AUTHOR]

TiO 2 is the most widely used material in photoelectrocatalytic systems. A key parameter to understand its efficacy in such systems is the band bending in the semiconductor layer. In this regard, knowledge on the band energetics at the semiconductor/current collector interface, especially for a nanosemiconductor electrode, is extremely vital as it will directly impact any charge transfer processes at its interface with the electrolyte. Since direct investigation of interfacial electronic features without compromising its structure is difficult, only seldom are attempts made to study the semiconductor/current collector interface specifically. This work utilizes ultraviolet photoelectron spectroscopy (UPS) to determine the valence band maximum ( E VBM ) and Fermi level ( E /TiN thin-film system reached using an Ar gas-clustered ion beam (GCIB). By combining UPS with GCIB depth profiling, we report an innovative approach for truly mapping the energy band structure across a nanosemiconductor/current collector interface. By coupling it with X-ray photoelectron spectroscopy (XPS), correlations among chemistry, chemical bonding, and electronic properties for the nano-TiO F ) at different depths in a nano-TiO 2 /TiN thin-film system reached using an Ar gas-clustered ion beam (GCIB). By combining UPS with GCIB depth profiling, we report an innovative approach for truly mapping the energy band structure across a nanosemiconductor/current collector interface. By coupling it with X-ray photoelectron spectroscopy (XPS), correlations among chemistry, chemical bonding, and electronic properties for the nano-TiO 2 /TiN interface could also be studied. The effects of TiO 2 in situ electrochemical reduction in aqueous electrolytes are also investigated where UPS confirmed a decrease in the semiconductor work function (WF) and an associated increase in n-type Ti 3+ centers of nano-TiO 2 electrodes post use in a 0.2 M potassium chloride solution. We report the use of UPS to precisely determine the energy band diagrams for a nano-TiO 2 /TiN thin-film interface and confirm the increase in TiO 2 n-type dopant concentrations during electrocatalysis, promoting a much more comprehensive and intuitive understanding of the TiO 2 activation mechanism by proton intercalation and therefore further optimizing the design process of efficient photocatalytic materials for solar conversion.

Nonstoichiometric nickel oxide (NiO x ) is one of the very few metal oxides successfully used as hole extraction layer in p-i-n type perovskite solar cells (PSCs). Its favorable optoelectronic properties and facile large-scale preparation methods are potentially relevant for future commercialization of PSCs, though currently low operational stability of PSCs is reported when a NiO x hole extraction layer is used in direct contact with the perovskite absorber. Poorly understood degradation reactions at this interface are seen as cause for the inferior stability, and a variety of interface passivation approaches have been shown to be effective in improving the overall solar cell performance. To gain a better understanding of the processes happening at this interface, we systematically passivated specific defects on NiO x with three different categories of organic/inorganic compounds. The effects on NiO x and the perovskite (MAPbI 3 ) deposited on top were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Here, we find that the perovskite's structural stability and film formation can be significantly affected by the passivation treatment of the NiO x surface. In combination with density functional theory (DFT) calculations, a likely origin of NiO x -perovskite degradation interactions is proposed. The surface passivated NiO x layers were incorporated into MAPbI 3 -based PSCs, and the influence on device performance and operational stability was investigated by current-voltage ( J - V ) characterization, impedance spectroscopy (IS), and open circuit voltage decay (OCVD) measurements. Interestingly, we find that a superior structural stability due to interface passivation must not relate to high operational stability. The discrepancy comes from the formation of excess ions at the interface, which negatively impacts all solar cell parameters.

The adsorption properties of CO 2 on the SrTiO 3 (001) surface were investigated using ambient pressure X-ray photoelectron spectroscopy under elevated pressure and temperature conditions. On the Nb-doped TiO 2 -enriched (1 × 1) SrTiO 3 surface, CO 2 adsorption, i.e., the formation of CO 3 surface species, occurs first at the oxygen lattice site under 10 -6 mbar CO 2 at room temperature. The interaction of CO 2 molecules with oxygen vacancies begins when the CO 2 pressure increases to 0.25 mbar. The adsorbed CO 3 species on the Nb-doped SrTiO 3 surface increases continuously as the pressure increases but starts to leave the surface as the surface temperature increases, which occurs at approximately 373 K on the defect-free surface. On the undoped TiO 2 -enriched (1 × 1) SrTiO 3 surface, CO 2 adsorption also occurs first at the lattice oxygen sites. Both the doped and undoped SrTiO 3 surfaces exhibit an enhancement of the CO 3 species with the presence of oxygen vacancies, thus indicating the important role of oxygen vacancies in CO 2 dissociation. When OH species are removed from the undoped SrTiO 3 surface, the CO 3 species begin to form under 10 -6 mbar at 573 K, thus indicating the critical role of OH in preventing CO 2 adsorption. The observed CO 2 adsorption properties of the various SrTiO 3 surfaces provide valuable information for designing SrTiO 3 -based CO 2 catalysts.

Fluorocarbon polymers (FPs) are ideal coatings for sliding parts in automotive, medical, or semiconductor manufacturing equipment owing to their excellent nonadhesiveness, low friction, and high heat and chemical resistance. FPs are used as coatings of slide bearings, oil pumps, sliding packing in automobiles, robot housing in biomedical fields, and the inner surface of the exhaust duct in semiconductor manufacturing equipment. However, the nonadhesiveness of FPs hinders their adhesion to metals, preventing their application. Recently, high-energy electron irradiation during the coating process above the melting point of FPs and under anoxic conditions has been proven to enhance the adhesion of FPs to metal substrates. However, the mechanism underlying this phenomenon remains unveiled because the investigation of the buried interface is difficult. Herein, we fabricated samples of fluorinated ethylene–polypropylene (FEP) coating an Al substrate using a unique approach based on semiconductor manufacturing processes to clarify the morphology and chemical interactions of the Al–FEP interface. Time-of-flight secondary ion mass spectrometry showed that the uncoated Al surface comprised 0.5 nm-thick Al hydroxides. Scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy showed that a 1000 keV electron irradiation during the coating process caused a significant diffusion of F atoms from the FEP layer to Al. Soft X-ray photoelectron spectroscopy (XPS) clearly indicated that the O atoms in the native Al2O3 layer were substituted by F atoms. Hard XPS showed the appearance of strong C–O–Al bonds caused by the irradiation. These results stem from the irradiation-induced cleavage of the C–F bonds in the FEP coating and O–Al–O bonds in the native Al2O3, facilitating the diffusion of F atoms and the formation of C–O–Al bonds, improving the adhesion between the FEP coating and Al substrate. Thus, high-energy electron irradiation modified the nanostructure at the Al–FEP interface through the FEP layer. [ABSTRACT FROM AUTHOR]

This Letter reports Pd-nanocluster catalysts and their formation in ligand-free Suzuki-Miyaura reactions with palladium-(II) nitrate as a precatalyst. The catalysts are water-soluble neutral Pd tetramer and trimer in their singlet electronic states, as identified by UV-vis absorption spectroscopy, and are formed by leaching of spherical Pd(0) nanoparticles with an average diameter of about 3 nm. The Pd(0) nanoparticles are produced by reducing palladium-(II) nitrate and characterized with transmission electron microscopy and Pd K-edge extended X-ray fine structure spectroscopy. The Pd-(II) reduction is induced by ethanol, enhanced by potassium hydroxide, and monitored with X-ray photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

The concept of a solid catalyst with an ionic liquid layer (SCILL) is a promising approach to improve the selectivity of noble metal catalysts in heterogeneous reactions. In order to understand the origins of this selectivity control, we investigated the growth and thermal stability of ultrathin 1-ethyl-3-methylimidazolium trifluormethanesulfonate [C 2 C 1 Im][OTf] films on Pt(111) by infrared reflection absorption spectroscopy (IRAS) and X-ray photoelectron spectroscopy (XPS) in time-resolved and temperature-programmed experiments. We combined these spectroscopy experiments with scanning tunneling microscopy (STM) to obtain detailed insights into the orientation and adsorption geometry of the ions in the first IL layer. Furthermore, we propose a mechanism for the thermal evolution of [C 2 C 1 Im][OTf] on Pt(111). We observe an intact IL layer on the surface at temperatures below 200 K. Adsorbed [C 2 C 1 Im][OTf] forms islands, which are evenly distributed over the surface. The [OTf] - anion adsorbs via the SO 3 group, with the molecular axis perpendicular to the surface. Anions and cations are arranged next to each other, alternating on the Pt(111) surface. Upon heating to 250 K, we observe changes in geometry and structural distribution. Whereas at low temperature, the ions are arranged alternately for electrostatic reasons, this driving force is no longer decisive at 250 K. Here, a phase separation of two different species is discernible in STM. We propose that this effect is due to a surface reaction, which changes the charge of the adsorbates. We assume that the IL starts to decompose at around 250 K, and thus, pristine IL and decomposition products coexist on the surface. Also, IRAS and XPS show indication of IL decomposition. Further heating leads to increased IL decomposition. The reaction products associated with the anions are volatile and leave the surface. In contrast, the cation fragments remain on the surface up to temperatures above 420 K.

This study investigates the influence of surface nitridation of Ta metal foil substrates on the growth of GaN nanorods using the laser molecular beam epitaxy (LMBE) technique and the field emission characteristics of the grown GaN nanorod ensemble. Surface morphology examinations underscore the pivotal role of Ta foil nitridation in shaping the dimensions and densities of GaN nanorods. Bare Ta foil fosters the formation of high-density, vertically self-aligned GaN nanorods at a growth temperature of 700 °C. Furthermore, the density of these nanorods is directly related to the duration of Ta foil nitridation, with increased duration leading to a reduced nanorod density. X-ray Photoelectron Spectroscopy (XPS) studies reveal that the transition of the Ta foil surface from tantalum oxide to tantalum nitride during nitridation emerges as a crucial factor influencing GaN nanorod growth. Photoluminescence (PL) spectroscopy at ambient temperature reveals a strong near-band-edge (NBE) emission peak with negligible defect-related peaks, displaying the high optical quality of the GaN nanorods. The highly dense vertically aligned GaN nanorod ensemble growth without Ta prenitridation exhibits the most favorable field emission performance, featuring a turn-on field of 2.1 V/μm, a field enhancement factor of 2480, and a stable long-term operation at the emission current density of 2.26 mA/cm 2 . This study advances the understanding of the role of the surface chemistry of metal foil in determining GaN nanorod growth and opens up exciting possibilities for tailoring advanced optoelectronic devices for specific application requirements.

The bottom-up synthesis of carbon-based nanomaterials directly on semiconductor surfaces allows for the decoupling of their electronic and magnetic properties from the substrates. However, the typically reduced reactivity of such nonmetallic surfaces adversely affects the course of these reactions. Here, we achieve a high polymerization yield of halogenated polyphenyl molecular building blocks on the semiconducting TiO 2 (110) surface via concomitant surface decoration with cobalt atoms, which catalyze the Ullmann coupling reaction. Specifically, cobalt atoms trigger the debromination of 4,4″-dibromo- p -terphenyl molecules on TiO 2 (110) and mediate the formation of an intermediate organometallic phase already at room temperature (RT). As the debromination temperature is drastically reduced, homocoupling and polymerization readily proceed, preventing presursor desorption from the substrate and entailing a drastic increase of the poly- para -phenylene polymerization yield. The general efficacy of this mechanism is shown with an iodinated terphenyl derivative, which exhibits similar dehalogenation and reaction yield.

To make a drug work better, the active substance can be incorporated into a vehicle for optimal protection and control of the drug delivery time and space. For making the drug carrier, the porous metal-organic framework (MOF) can offer high drug-loading capacity and various designs for effective drug delivery performance, biocompatibility, and biodegradability. Nevertheless, its degradation process is complex and not easily predictable, and the toxicity concern related to the MOF degradation products remains a challenge for their clinical translation. Here, we describe an in-depth molecular and nanoscale degradation mechanism of aluminum- and iron-based nanoMIL-100 materials exposed to phosphate-buffered saline. Using a combination of analytical tools, including X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, small-angle X-ray scattering, and electron microscopy, we demonstrate qualitatively and quantitatively the formation of a new coordination bond between metal(III) and phosphate, trimesate release, and correlation between these two processes. Moreover, the extent of material erosion, i.e. , bulk or surface erosion, was examined from the transformation of nanoparticles' surface, morphology, and interaction with water. Similar analyses show the impact of drug loading and surface coating on nanoMIL-100 degradation and drug release as a function of the metal-ligand binding strength. Our results indicate how the chemistry of nanoMIL-100(Al) and nanoMIL-100(Fe) drug carriers affects their degradation behaviors in a simulated physiological medium. This difference in behavior between the two nanoMIL-100s enables us to better correlate the nanoscale and atomic-scale mechanisms of the observed phenomena, thus validating the presented multiscale approach.

Natural polyphenol assisted fabrication of nanohybrids with improved stability and bioactivity have gained considerable interest in material science. In this study, the anticancer flavone chrysin (5,7-dihydroxyflavone ChR) was employed to fabricate silver (AgNPs) and gold nanoparticles (AuNPs) hybridized reduced graphene oxide (rGO) nanocomposites (ChR@Ag-rGONCs and ChR@Au-rGONCs) with long-term stabilities. Prepared nanocomposites (NCs) were characterized using high-throughput analyses. The hydroxyl (O–H) and carbonyl (CO) functional groups of ChR actively contribute to the reduction of GO/metal ions (Ag+ and Au3+) and uniform decoration of Ag and AuNPs on the rGO active sites. The presence of noble metal NPs on the rGO surface improved its thermal stability and performances in diverse physiological conditions. Moreover, the surface passivation of the fabricated NCs with natural anticancer flavone ChR improved its biocompatibility. Due to the synergistic impact of the plasmonic metal–rGO hybrids, the fabricated NCs exhibited an increased cytotoxic effect over that of free-ChR against two different breast carcinoma (MDA-MD-468 and MDA-MD-231) cell lines. The prepared NCs showed comparatively less toxicity against the normal mouse fibroblast (L929) cells, demonstrating the high safety of biofunctionalized NCs in anticancer therapy. We demonstrated that the generation of reactive oxygen species released by the metal ions coexisting on the rGO induce apoptosis. Hence, this work offers a natural and viable scaling-up procedure to synthesize noble metal NPs decorated hybrid rGO composites for useful antibreast cancer applications. [ABSTRACT FROM AUTHOR]

Solution-based organometallic nanoclusters are unique nanoscale precursors due to the ability to precisely control their size, shape, structure, and assembly. The interaction of extreme ultraviolet (EUV) or X-ray photons with these organometallic nanoclusters can result in processes that can lead to a change in solubility. This makes these materials prime candidates for next-generation photoresists for EUV nanolithography. In this study, we investigate the interaction of X-ray radiation with a charge neutral, sodium templated, butyl-tin Keggin (β-NaSn13) nanocluster. This nanocluster is used as a model EUV photoresist to better understand the radiation induced solubility transition. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) was used to characterize the β-NaSn13 thin films, where Sn 3d, O 1s, and C 1s core levels were measured under a range of ambient conditions, including ultrahigh vacuum and 1 mbar of oxygen, water, methanol, or nitrogen. A photon dose array was obtained for each ambient condition to determine their effect on the photon induced chemistries which result in the solubility transition. The resulting contrast curves indicate that an oxygen ambient significantly reduces the required photon dose for the solubility transition relative to UHV, while all other ambients increase the required photon dose for the solubility transition relative to UHV. We performed in situ XPS after postexposure annealing β-NaSn13 thin films in multiple ambients to study the chemistry that occurs after a postexposure bake (PEB). The β-NaSn13 thin films retained a significant amount of aliphatic carbon following the PEB in all the ambients we studied. On the basis of our studies, we propose that the solubility transition for β-NaSn13 thin films occurs through radical hydrogen abstraction and radical–radical coupling reactions. These studies further improve the understanding of photon induced chemistries in a β-NaSn13 model resist and provide mechanistic insights for EUV lithography processing with organometallic nanomaterials. [ABSTRACT FROM AUTHOR]

Quantum dot solar cells are based on the concept of harvesting different parts of the solar light spectrum with a single, cheap semiconductor by simply changing the size of the nanoparticles. Of the many compositions explored, germanium is one of the most interesting as it has the major advantage of a large Bohr radius, which allows for the fabrication of larger particles. Moreover, germaniums possess very high optical absorption, and a small band gap give it free parameters to optimize the quantum dot solar cell. In a previous work, the germanium quantum dots were used in a Grätzel type solar cell containing an electrolyte, which is not desirable for applications. In this work instead, the n-doped germanium quantum dots were combined with a p-doped a-Si layer, making it the first all solid-state solar cell made from nanoparticles from a gas aggregation nanoparticle source. Remarkably, the effect of quantum confinement in both the germanium quantum dot assembled layer and a-Si was observed by peaks in the spectral response experiments. This work forms an important step toward realizing a germanium quantum dot based solar cell and studying quantum dot based solids. [ABSTRACT FROM AUTHOR]

Functionalized carbon nanostructures have garnered significant research interest as a class of materials for a myriad of energy applications, including fuel cell catalysts, and batteries. However, the design and optimization of these materials is impeded by the challenges in identifying heteroatom chemical speciation and spatial distribution within a carbon nanomaterial, as well as correlating these properties with application-specific performance metrics. In this work, a set of nitrogen-functionalized carbon nanospheres (N–Csph) was synthesized with independent control over nitrogen functionality and N–Csph size and shape. This study features atom probe tomography (APT) of these isolated N-doped carbon nanospheres along with a thorough description of many considerations and challenges for APT of these materials, considering both sample preparation and analysis of data. The APT discussion provides a foundation for future studies of modified C materials with the goal of gaining insights into 3D heteroatom distribution within functionalized carbon nanomaterials through cross-correlative analysis between APT and complementary characterization techniques. Transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) was conducted in order to verify the morphology of the N–Csph, 2D spatial distribution of nitrogen heteroatoms, and the chemical distribution of nitrogen functionalities. Variable energy XPS was employed to characterize the depth dependence of chemical species' distribution, showing that certain nitrogen functionalities were more surface-enriched than others. This study discusses cross-correlative analysis between APT and XPS, with the two techniques providing powerful complementary elemental and chemical information for energy application materials. [ABSTRACT FROM AUTHOR]

While organic-inorganic hybrid perovskites are emerging as promising materials for next-generation photovoltaic applications, the origins and pathways of perovskite instability remain speculative. In particular, the degradation of perovskite surfaces by ambient water is a crucial subject for determining the long-term viability of perovskite-based solar cells. Here, we conducted surface characterization and atomic-scale analysis of the reaction mechanisms for methylammonium lead bromide (MA(CH 3 NH 3 )PbBr 3 ) single crystals using ambient-pressure atomic force microscopy (AP-AFM) and near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS) in environments ranging from ultrahigh vacuum to 0.01 mbar of water vapor. MAPbBr 3 single crystals, grown by a solution process, were mechanically cleaved under UHV conditions to obtain an atomically clean surface. Consecutive topography and friction force measurements in low-pressure water ( p water ≈ 10 -5 mbar) revealed the formation of degraded patches, one atomic layer deep, gradually increasing their coverage until the surface was entirely covered at a water exposure of 4.7 × 10 4 langmuir (L). At the perimeters of these degraded patches, a higher friction coefficient was observed, along with an interstitial step height, which we attribute to a structure equivalent to that of the MA-Br terminated surface. Combined with NAP-XPS analysis, our results demonstrate that water vapor induces the dissociation of surface methylammonium ligands, eventually resulting in the depletion of the surface MA and the full coverage of hydrocarbon species after exposure to 0.01 mbar of water vapor.

This study focuses on investigating the intriguing properties of Ca 10 (PO 4 ) 6 (OH) 2 (HAP)-K 0.5 Na 0.5 NbO 3 (KNN) bioceramic composites, seeking to elucidate the relationship between their structural, electrical, biological, and optical behavior. The article begins with a close inspection of the O 1s spectra of the specimens obtained from X-ray photoelectron spectroscopy (XPS). The spectra reveal the peak related to lattice oxygen, O vacancy and the surface adsorbed O. The formed O vacancy strongly influences the changes in lattice parameters as observed from the X-ray diffraction (XRD) patterns. The frequency variation of the dielectric response for the composites in the radio frequency (RF) regime has electrical polarization effective for biomedical applications. Nyquist plots along with equivalent RC circuits further confirm that those electrical responses are mainly contributed from the grain boundaries. Adsorption dynamics of protein on the ceramic surface are investigated using bovine serum albumin (BSA), which established the major role of electrostatic interaction. Surface charge and O vacancies are modeled to understand the adsorption of protein and a linear correlation is reported. The role of O vacancies in modulating adsorption dynamics adds a new dimension to this study. The conformational change of BSA has also been considered by constructing the secondary structure following the protein-ceramic interaction. Excitingly, the composites are also found to be fluorescent active, a courtesy of the defects and vacancies leading to electron-hole recombination in the forbidden region. These promising properties envision an exciting future for HAP-KNN composites, especially in the domain of bioimaging and bone-tissue engineering.

Garnet-type Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) is a highly promising solid-state lithium metal battery electrolyte due to its exceptional ionic conductivity and electrochemical stability. However, when exposed to air, a passivation layer can be spontaneously formed on the garnet-type electrolyte, deteriorating its wettability with metallic lithium (Li) and impeding the lithium ion transfer at the Li-garnet electrolyte interface. The passivation layer is considered a critical issue for garnet-type solid electrolytes. Despite intensive research, the formation mechanism of the passivation film remains poorly understood. The key to elucidating the formation mechanism is to obtain a pristine garnet electrolyte surface and study how the pristine garnet electrolyte interacts with air. In this study, different passivation layer removal pretreatments were performed to expose pristine garnet electrolytes, and their impacts on the samples were systematically studied. The results reveal the overlooked negative impacts of vacuum annealing and acid treatment on LLZTO, which are indicated by the severe loss of Li and O and the formation of additional Li-depleted metal oxides. It was confirmed that argon annealing is the only viable approach to remove the passivation layer without introducing concomitant contaminations to LLZTO. Based on this method, we directly evidenced the formation of LiOH on LLZTO under rarefied air using quasi- in situ X-ray photoelectron spectroscopy. It was confirmed that the loss of Li and O ions, rather than Li + /H + exchange, drives the formation of LiOH in the passivation layer. These results not only provide a better understanding of the surface and interface chemistry of LLZTO but also reveal a reliable surface treatment for the LLZTO sample.

In 2 O 3 -based catalysts have shown high activity and selectivity for CO 2 hydrogenation to methanol; however, the origin of the high performance of In 2 O 3 is still unclear. To elucidate the initial steps of CO 2 hydrogenation over In 2 O 3 , we have combined X-ray photoelectron spectroscopy and density functional theory calculations to study the adsorption of CO 2 on the In 2 O 3 (111) crystalline surface with different terminations, namely, the stoichiometric, reduced, and hydroxylated surface. The combined approach confirms that the reduction of the surface results in the formation of In adatoms and that water dissociates on the surface at room temperature. A comparison of the experimental spectra and the computed core-level shifts (using methanol and formic acid as benchmark molecules) suggests that CO 2 adsorbs as a carbonate on all three surface terminations. We find that the adsorption of CO 2 is hindered by hydroxyl groups on the hydroxylated surface.

Interfacial instabilities in electrodes control the performance and lifetime of Li-ion batteries. While the formation of the solid-electrolyte interphase (SEI) on anodes has received much attention, there is still a lack of understanding the formation of the cathode-electrolyte interphase (CEI) on the cathodes. To fill this gap, we report on dynamic deformations on LiFePO 4 cathodes during charge/discharge by utilizing operando digital image correlation, impedance spectroscopy, and cryo X-ray photoelectron spectroscopy. LiFePO 4 cathodes were cycled in either LiPF 6 , LiClO 4 , or LiTFSI-containing organic liquid electrolytes. Beyond the first cycle, Li-ion intercalation results in a nearly linear correlation between electrochemical strains and the state of (dis)-charge, regardless of the electrolyte chemistry. However, during the first charge in the LiPF 6 -containing electrolyte, there is a distinct irreversible positive strain evolution at the onset of anodic current rise as well as current decay at around 4.0 V. Impedance studies show an increase in surface resistance in the same potential window, suggesting the formation of CEI layers on the cathode. The chemistry of the CEI layer was characterized by X-ray photoelectron spectroscopy. LiF is detected in the CEI layer starting as early as 3.4 V and Li x PO y F z appeared at voltages higher than 4.0 V during the first charge. Our approach offers insights into the formation mechanism of CEI layers on the cathode electrodes, which is crucial for the development of robust cathodes and electrolyte chemistries for higher-performance batteries.