Boron nitride nanotubes (BNNTs) and hexagonal boron nitride platelets (h-BNs) have received considerable attention for aerospace insulation applications due to their exceptional chemical and thermal stability. Presently, making BN nanomaterials compatible with polymer and composite matrices is challenging. Due to their inert and highly stable structure, h-BN and BNNTs are difficult to covalently functionalize. In this work, we present a novel sonochemical technique that enables covalent attachment of fluoroalkoxy substituents to the surface of BN nanomaterials in a controlled and metered process. Covalent functionalization is confirmed via colloidal stability analysis, FT-IR, and x-ray photoelectron spectroscopy (XPS).

Graphene has been publicized as the game changing material of this millennium. As research continues to expand our knowledge of this 2D semimetal, the properties at the interface have become an increasingly important characteristic. Translating graphene’s strength at the nanoscale to the macroscale is suggested by functionalizing the graphene, creating a favourable interfacial morphology to adhere. An interfacial morphology that is able to form primary chemical bonds is ideal, providing the best mechanical property performance. We proposed a method of creating a graphene reinforced polymer matrix composite from flake mineral graphite in-situ, using high shear elongational flow to produces these conditions. In our process we were able to identify chemical bonding at graphene’s surface, which developed into newly created interfacial morphologies. These morphologies lead to an increase in mechanical properties while providing an improved stress transfer between graphene and its containing matrix. Our work sheds light on a solvent free route to scalable high strength graphene composites.

A series of ${\left\hbox[ {{{\left\hbox( {{\rm{SnSe}}} \right\hbox)}_{1 \hbox+ \delta }}} \right\hbox]_m}{\left\hbox[ {{\rm{TiS}}{{\rm{e}}_2}} \right\hbox]_2}$ heterostructure thin films built up from repeating units of m bilayers of SnSe and two layers of TiSe2 were synthesized from designed precursors. The electronic structure of the films was investigated using X-ray photoelectron spectroscopy for samples with m = 1, 2, 3, and 7 and compared to binary samples of TiSe2 and SnSe. The observed binding energies of core levels and valence bands of the heterostructures are largely independent of m. For the SnSe layers, we can observe a rigid band shift in the heterostructures compared to the binary, which can be explained by electron transfer from SnSe to TiSe2. The electronic structure of the TiSe2 layers shows a more complicated behavior, as a small shift can be observed in the valence band and Se3d spectra, but the Ti2p core level remains at a constant energy. Complementary UV photoemission spectroscopy measurements confirm a charge transfer mechanism where the SnSe layers donate electrons into empty Ti3d states at the Fermi energy.

Chemical bonding in native oxides of GaAs, before and after etching, is detected by X-Ray Photoelectron Spectroscopy (XPS). It is correlated with surface energy engineering (SEE), measured via Three Liquid Contact Angle Analysis (3LCAA), and oxygen coverage, measured by High Resolution Ion Beam Analysis (HR-IBA).

Before etching, GaAs native oxides are found to be hydrophobic with an average surface energy, γT, of 33 ± 1 mJ/m2, as measured by 3LCAA. After dilute NH4OH etching, GaAs becomes highly hydrophilic and its surface energy, γT, increases by a factor 2 to a reproducible value of 66 ± 1 mJ/m2. Using HR-IBA, oxygen coverage on GaAs is found to decrease from 7.2 ± 0.5 monolayers (ML) to 3.6 ± 0.5 ML. The 1.17 ratio of Ga to As, measured by HR-IBA, remains constant after etching.

XPS is used to measure oxidation of Ga and As, as well as surface stoichiometry on two locations of several GaAs(100) wafers before and after etching. The relative proportions of Ga and As are unaffected by adventitious carbon contamination. The 1.16 Ga:As ratio, measured by XPS, matches HR-IBA analysis. The proportions of oxidized Ga and As do not change significantly after etching. However, the initial ratio of As2O5 to As2O3, within the oxidized As, significantly decreases after etching from approximately 3:1 to 3:2.

Absolute oxygen coverage, as a function of surface processing, is determined within 0.5 ML by HR-IBA. XPS offers insight into these modifications by detecting electronic states and phase composition changes of GaAs oxides. The changes in surface chemistry are correlated to changes in hydro-affinity and surface energies measured by 3LCAA.

One of the most promising methods to produce graphene in large scale is the use of chemical exfoliation together with chemical reduction to achieve reduced graphene oxide. Replacing conventional reducing agents, such as NaBH4 and hydrazine, with cheap, widely available, safe, environmentally friendly, and easy-to-prepare reducing agents is a key to large-scale commercial production of reduced graphene oxide. In this work, we investigate the effectiveness of utilizing fruit extracts derived from banana peel and juice to reduce graphene oxide. After the reduction, the oxygen-containing functional groups in graphene oxide are effectively removed, and the sp2 hybridized carbon-carbon bonding networks are restored, as evidenced by the characterization using x-ray photoelectron spectroscopy and Raman spectroscopy. Our banana extracts would offer a promising pathway for realizing cheap, safe, and environmentally friendly reducing agents for the upscale production of reduced graphene oxide.

The present work describes a simple method to produce zinc oxide nanoparticles supported in nitrogen-doped reduced graphene oxide, ZnO/N-rGO. The rGO structures were nitrogen-doped using hydrazine as nitrogen source (N-rGO) with the purpose of enhancing the rGO capability to promote the electrons transport along their surface. Thus, ZnO/N-rGO catalytic systems were tested as photocatalyst to degrade methylene blue and lignin molecules under ultraviolet (UV) and visible (Vis) light irradiation. N-doping of rGO was confirmed by X-ray photoelectron spectroscopy (XPS). Photocatalytic degradation studies confirm better performance of the ZnO/N-rGO in comparison to ZnO. The percentage of lignin degradation for the ZnO/N-rGO compound under UV was 59%, while using visible energy it was achieved 46%, in a time of 70 min.

We have investigated the chemical and electrical properties of a thin SiO2/TiO2 stacking layer deposited on n-Si and heavily phosphorus-doped n++ Si substrates to elucidate effects of phosphorus doping of Si absorbers on the band alignment and electrical performance of a SiO2/TiO2 stack-based electron-selective contact deposited on the differently doped Si substrates. From our XPS study, we show a shift of the TiO2 energy levels up to ∼0.13 eV with respect to those of Si as the doping level of Si substrates changes. We also show that the conduction band offset of the SiO2/TiO2 stacking layer at the interface with the n++ Si substrate seems to smaller than that of the SiO2/TiO2 stacking layer at the interface with n-Si substrate. Finally, from our electrical transport measurements, we could conclude that the thinner tunneling barrier, the increased electron density in front of the SiO2 layer in the n++ Si surface, and/or the reduced barrier height by heavy doping, seem to enhance the majority electron transport property of the SiO2/TiO2/n++ Si samples compared to that of the SiO2/TiO2/n-Si samples.

Either boron or nitrogen doped multilayered graphene was prepared by thermal chemical vapor deposition (CVD). Obtained heteroatom doped graphene was examined by Raman scattering, x-ray photo electron spectroscopy (XPS) and temperature dependence of sheet resistance. From the Raman scattering, obvious increase of ID/IG ratio could not be detected by boron doping, while it increased by ∼0.2 or more for nitrogen doped sample. From XPS, doping rates of boron and nitrogen were estimated to be in the range of 5∼12 at% and 1∼2 at%, respectively. XPS also showed that the boron and nitrogen atoms would locate at the doping sites of both graphitic and neighborhood of atomic defect. Magnitude of sheet resistance was decreased by either doping of boron or nitrogen.

The emergence of 2D materials has led to increased attention on correlating the structural, optical, and optoelectronic properties of atomically thin transition metal chalcogenides like MoS2. We demonstrate the tunability of the photoluminescence (PL) properties of bulk MoS2 via implantation of Nb ions. Raman spectroscopy is used to confirm the p-type doping. The PL intensity of MoS2 is drastically enhanced by the adsorption of p-type dopants. X-ray photoelectron spectroscopy (XPS) is used to study the change of MoS2 structure post-implantation. Our results provide a new route for modulating the optical properties of two-dimensional semiconductors. The strong and stable PL from defect sites of MoS2 created by Nb ion implantation may have promising applications in optoelectronic devices.

Sulfur loss from the surface of MoS2(0001) is observed following the adsorption of methanol on MoS2 at 86 K and subsequent annealing of MoS2 near 300 K. This sulfur loss, at the MoS2 surface, leads to suppression of inverse photoemission features characteristic of the unoccupied states associated with MoS2. This sulfur loss is counteracted by further annealing to 350 K, as is evident in the temperature dependent sulfur to molybdenum integrated X-ray photoemission intensity ratios near 300 to 350 K. Upon further annealing to 350 K, inverse photoemission additionally indicates a reestablishment of characteristic features associated with the unoccupied states of MoS2. These results are indicative of sulfur segregation to the surface and compensation of surface vacancy sites.

Lithium-ion batteries featuring electrodes of silicon nanoparticles, conductive carbon, and polymer binders were constructed with electrolyte containing 1.2 M LiPF6 in ethylene carbonate and diethyl carbonate (1:1, w/w). Material binders used include polyvinylidene difluoride (PVdF), polyacrylic acid (PAA), sodium carboxymethyl cellulose (CMC), and a mixture of equal masses of CMC and PAA (CMCPAA). Hard X-ray photoelectron spectroscopy (HAXPES) was performed on the electrodes when fresh, cycled at reduced potential, and cycled one full time to study how substrate material binders affect the early formation of the solid electrolyte interphase (SEI) layer. Electrodes cycled 5, 10, and 20 times were also analyzed to discern what changes to the SEI occur after initial formation. We also present estimates of the SEI thickness by cycle count, indicating that PAA develops the thinnest SEI, followed by CMCPAA, CMC, and PVdF in order of increasing layer thickness.

Atomic layer deposition (ALD) of air stable cobalt and nickel complexes based on tridentate enaminones N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylethyldiamine (Htfb-dmeda) and N,N-(4,4,4-trifluorobut-1-en-3-on)-dimethylpropyldiamine (Htfb-dmpda) successfully produced metallic cobalt and nickel thin films. Detailed X-ray photoelectron spectroscopy (XPS) studies on the binding interaction of the first precursor monolayer with the surface functional groups elucidated the chemisorption behavior of the new precursor systems. A reactive remote hydrogen plasma was used as the co-reactant to activate the precursor decomposition yielding metal hydroxide intermediates. Subsequent hydrogen plasma etching of as-deposited films resulted in phase-pure metallic films through a recrystallization process, verified by surface and sub-surface XPS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed pinhole-free films, with low surface roughness (0.2 ± 0.06 nm root mean square, RMS) for both, cobalt and nickel thin films. Herein, the competitive role of hydrogen as etchant and reactant was demonstrated as prolonged plasma exposure time periods resulted in the formation of metal hydrides. This is mostly due to the catalytic dissociation of molecular hydrogen on transition metal surfaces, which already occurs upon low energy input.

The magnetic properties of a magnetic material can be modified by elastic deformation—termed the magnetoelastic effect. This effect is considered an alternative approach to magnetic fields for the low-power control of magnetization states of nanostructures since it avoids charge currents that create heat dissipation. This article describes the effects of dynamic strain accompanying a surface acoustic wave on magnetic nano-elements. We use a technique based on stroboscopic x-ray microscopy to simultaneously image the evolution of both strain and magnetization at the nanometer length and picosecond time scales. The study shows that there is a delayed response of the magnetization to dynamic strain, adjustable by the magnetic properties of the material. The presented analysis provides insights into dynamic magnetoelastic coupling in nanostructures with implications for the design of strain-controlled nanodevices.

The changes in hydrodesulfurization activity, selectivity, dispersion, sulfidation, and extent of promotion of Co(Ni)Mo catalysts were investigated when the alumina support surface is modified by grafting 4 wt% silica. Adding SiO2 eliminates the most reactive hydroxyl groups on the alumina surface (IR band at 3775 cm−1) decreasing the possibility of generating tetrahedral Mo species difficult to sulfide in favor of octahedral ones capable of contributing to the sulfided active phase. The catalysts were evaluated in the hydrodesulfurization of 4,6-dimethyldibenzothiophene. Incorporating SiO2 to alumina increases the hydrogenation rate constant and therefore the global hydrodesulfurization rate of 4,6-dimethyldibenzothiophene and enhances the promotion of Mo by Co (or Ni). The global sulfidation of Ni is not affected by the addition of silica but the sulfidation of cobalt is significantly improved. The extent of promotion of the NiMo/Al2O3 and NiMo/SiO2/Al2O3 catalysts was greater than the one achieved in their Co-promoted counterparts.

X-ray photoelectron spectroscopy (XPS) was used to determine the surface-charge magnitude and distribution for some micas and high-illite I-S clays. Based on predictable layer by layer atomic ratios for margarite, muscovite and sericite it was possible to establish an escape depth of ∼15 Å for photoelectrons. After the replacement of surface ions by Ba2+, interlayer ion (Ca, K, Na)/Ba ratios are a measure of the relative layer charges on external surfaces and the first internal interlayer. These ratios can be used to assign charge magnitudes and ascertain layer charge asymmetry when it occurs. The O/Ba ratios determined by XPS serve the same purpose. Diagenetic I-S from the Vienna Basin gives an XPS-determined symmetrical layer charge of 0.41; in a similar clay from the Gulf Coast sequence, the outer surface is smectitic, with an external charge of 0.21, in contrast to an opposing silica layer with a charge of 0.31.

We develop an asymmetric aqueous supercapacitor using iron oxide anode and cobalt oxide cathode. The anode was fabricated using electrospinning of carbon precursor/iron oxide precursor blend followed by pyrolysis and in situ electrochemical conversion (to oxide) to form the binder-free and freestanding composite anode which delivered a capacitance of 460 F/g at 1 A/g and retained 82% capacitance after 5000 cycles. The superior performance is attributed to easy electrolyte accessibility as well as the porous fibrous carbon morphology, facilitating volume expansion of iron oxide. The cobalt oxide cathode was prepared using a simple chemical synthesis technique. The electrodes were chosen based on high over potential to water splitting reactions in 6 M KOH electrolyte resulting in a potential window of 1.6 V. The asymmetric device operated in 1.6 V achieved a capacitance of 94.5 F/g at 0.5 A/g while retaining 75% of its capacitance after 12,000 cycles, delivering energy and power densities of 40.53 W h/kg and 2432 W/kg, respectively.

Metal organic precursor has a sufficiently high vapor pressure at low temperature, contributing high-speed low-temperature MOCVD-MoS2 film formation. We fabricated monolayer MoS2 by 1 step cold-wall MOCVD using di-isopropyl-diazadiene-molybdenum tricarbonyl [i-Pr2DADMo(CO)3] and di-tertiary-butyl disulfide [(t-C4H9)2S2]. These precursors are able to be vaporized using bubbling system and deposited at low temperature. From the XPS investigations, Mo-S bonding peaks were observed and S:Mo ratio was calculated as 2:1, suggesting formation of MoS2. Moreover, molybdenum carbides and nitrogen impurities were not observed which was confirmed by XPS and EDX. From the results of Raman spectroscopy, AFM height distribution, and spectroscopic ellipsometry, it was determined that the film thickness is 0.64 nm which is corresponding to monolayer MoS2, the lateral grain size is approximately 100 nm, and the bandgap energy is 1.8 eV.

Enzymes have recently attracted increasing attention in material research based on their capacity to catalyze the conversion of polymer-bound moieties for synthesizing polymer networks, particularly bulk hydrogels. In this study, the surface immobilization of a relevant enzyme, mushroom tyrosinase, should be explored using glass as model surface. In a first step, the glass support was functionalized with silanes to introduce either amine or carboxyl groups, as confirmed e.g. by X-ray photoelectron spectroscopy. By applying glutaraldehyde and EDC/NHS chemistry, respectively, surfaces have been activated for subsequent successful coupling of tyrosinase. Via protein hydrolysis and amino acid characterization by HPLC, the quantity of bound tyrosinase was shown to correspond to a full surface coverage. Based on the visualized enzymatic conversion of a test substrate at the glass support, the functionalized surfaces may be explored for surface-associated material synthesis in the future.

We determined that the conduction band offset (CBO) and the valence band offset (VBO) at the CdS/ Cu2ZnSnSe4 (CZTSe) heterointerface are +0.56 and +0.89eV, respectively, by using X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and inversed photoemission spectroscopy (IPES). A positive CBO value, so-called “spike” structure, means that the position of conduction band becomes higher than that of absorber layer. The evaluated CBO of +0.56 eV suggests that the conduction band alignment at CdS/CZTSe interface is enough to become an electron barrier. Despite such a large spike structure in the conduction band at the interface, a conversion efficiency of 8.7 % could be obtained for the CdS/CZTSe heterojunction solar cells.

Cerium dioxide (CeO2) thin films were deposited by atomic layer deposition (ALD) on both Si and TiN substrates. The ALD growth produces CeO2 cubic polycrystalline films on both substrates. However, the films show a preferential orientation along <200> crystallographic direction for CeO2/Si or <111> for CeO2/TiN. In correspondence, we measure a relative concentration of Ce3+ equals to 22.0% in CeO2/Si and around 18% in CeO2/TiN, by X-ray photoelectron spectroscopy. Such values indicate the presence of oxygen vacancies in the films. Our results underline the films differences and similarities between ALD-deposited CeO2 either on Si or TiN substrates, thus extending the knowledge on the CeO2 structural and chemical properties.