Electron Scanning Tunneling Microscopy Research Articles

Passive Film Formed on Si-Mn Steel in Boric Acid-Borate Buffer at 6.5

Passivity-maintaining current of high-strength (Si-Mn) steel in boric acid-borate buffer at pH 6.5 was larger than that of ferrite/pearlite (F/P) steel. Charge transfer resistance of the Si-Mn steel surface passivated at 1.10 V vs SHE in pH 6.5 buffer was smaller than that of F/P steel surface. Nano-analyses using AES and STEM revealed the details of the structure and components of the passive film on the Si-Mn steel. The inferiorities of passivity of Si-Mn steel were suggested to be due to the alloying components and metallurgical structure to increase the strength of the steel.

Comparison of physical and chemical vapor deposition for magnesium intercalation underneath epitaxial graphene

Intercalation of Mg into epitaxial graphene was investigated using chemical vapor deposition (CVD) and physical vapor deposition (PVD) for the formation of n-type doped graphene. Scanning electron microscopy and atomic force microscopy indicate PVD has significantly greater metal deposition and surface roughness compared to the CVD process. Findings from x-ray photoelectron spectroscopy infer the formation of Mg intercalated quasi-freestanding epitaxial graphene indicated by shifting of the SiC peak in C 1s spectra. This is substantiated by visual evidence from scanning tunneling electron microscopy of one or more layers of Mg residing underneath EG. Furthermore, an invariant 2D peak position in Raman spectra taken over a 7-day period in ambient conditions support arguments of the stability of electron doped Mg-intercalated epitaxial graphene. CVD offers a cleaner and smoother surface compared to PVD due to improved control over when the substrate is subjected to Mg exposure, but PVD allows for greater Mg concentrations per minute that may increase the amount of intercalated metal.

Understanding the Electrooxidation of Dimethyl Ether on Pt3Pd3Sn2 Supported on a Mixture of Carbon Materials

Recently, we reported a rigorous study on the effect of carbon supports and their cold plasma treatment on a state-of-the-art catalyst, Pt3Pd3Sn2, for dimethyl ether (DME) electrooxidation. The catalyst supported on a mixture of 75% activated multi-walled carbon nanotube (MWCNT) (75 M) and 25% pristine black pearl 2000 (BP2000) (25B) (Pt3Pd3Sn2/75M25B) offered improved DME kinetics with respect to the single or other combinations of the same supports. In this work, the results of the electrochemical impedance spectroscopy (EIS) were coupled with physicochemical characterizations (X-ray Diffraction (XRD), Small Angle X-ray Scattering (SAXS), and Scanning Tunneling Electron Microscopy (STEM)) for a detailed understanding of the origins of the improved kinetics. With an appropriate composition of the two supports in the mixture (75M25B), a catalyst with optimized particle size, dispersion, and conductivity was obtained. A Pt3Pd3Sn2/75M25B-coated electrode exhibited a reduced charge transfer resistance of 0.63 ohms at the catalyst layer compared to BP2000 and MWCNT, which showed 1.53 and 1.31 ohms, respectively. These results provide vital insights into catalyst support design considering the use of support mixtures of optimized conductivity and surface area for enhanced power output.

Solution-Processed Formation of DNA-Origami-Supported Polyoxometalate Multi-Level Switches with Countercation-Controlled Conductance Tunability

We report a chemically programmed design and the switching characteristics of a functional metal–DNA-origami–polyoxometalate (POM) material obtained from the solution-processed assembling of biocompatible molecular precursors. The DNA origami is immobilized on the gold surface via thiolate groups and acts as a carrier (ad-layer) structure, ensuring the spatially controlled hybridization of the pre-defined six-helix bundle (6HB) positions with DNA-augmented, tris(alkoxo)-ligated Lindqvist-type polyoxovanadate (POV6) units. The DNA-confined POV6 units accept electrons in a stepwise fashion, allowing for a multi-logic function, which we directly probe using scanning tunneling electron microscopy and spectroscopy. Electron acceptance and injection into the originally non-conducting DNA structure and the subsequent release to the gold substrate depend upon the potential at the nanoscale tip and the oxidation state of POV6, as well as on the mechanism of action of POV6 countercations. By combining experiment and theory, we show that the bio-hybrid heterojunction has far-reaching potential to create a chemically controlled POM-based nano-environment with synaptic behavior.

Interaction Study of Anti‐E. coli Immobilization on 1DZnO at Nanoscale for Optical Biosensing Application

AbstractDeveloping low‐cost biosensing platforms for robust detection response and sensitivity at low concentrations is of great interest. This work reports synthesizing 1D ZnO nanostructured materials (1DZnO) with controllable properties utilizing a metal catalyst‐assisted vapor phase growth technique (VLS). The obtained materials are functionalized with (3‐aminopropyl) trimetoxysilane (APTMS) and immobilized with anti‐Escherichia coli enteropathogenic (EPEC) antibodies. Characterization results show changes in the optical and structural properties of 1DZnO that are correlated with the biofunctionalization methodologies. Further, the biofunctionalization process is assessed on 1DZnO surface platforms to obtain acceptable antibody immobilization efficiencies (52%, 96%, and 100%) using a low‐concentration antibody solution (30 µg ml−1). Special techniques such as focused ion beam micromachining and scanning tunneling electron microscopy are proposed to appreciate the semiconductor biofunctionalization layer around 1DZnO and explain the physics of the interaction process. It is found that morphology obtained from distinct synthesis methods, solvents, and functionalization agents can generate functional groups for biomolecule attachment. Remarkably, it is demonstrated that biofunctionalization on 1DZnO takes place all over a single nanostructure. This work presents a proof‐of‐concept focused on generating pathogen sensing platforms using 1DznO semiconducting materials, providing new insights into bio‐analytes interaction with structures at the nanoscale.

The Importance of Structural Uniformity and Chemical Homogeneity in Cobalt-Free Lithium Excess Nickel Manganese Oxide Cathodes.

This study explores the relationships between material quench rate during processing and the resulting structural and electrochemical properties of Li[Ni0.25 Li0.167 Mn0.583 ]O2 . Samples of this lithium-rich material are prepared with highly contrasting postfiring cooling methods: a rapid water emersion quench or closed-door oven cooling. The contrasting approaches result in samples with different structural, chemical, and electrochemical behaviors; after cycling the rapidly quenched material yields greater capacity, greater stability, and initially lower, but more stable voltages than the slower cooled samples. Through the use of scanning tunneling electron microscopy, X-Ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) it is demonstrated that rapidly quenched powders are more structurally uniform and chemically homogenous before cycling. By comparing these precycling sample to postcycling samples, it is then examined how this increased structural uniformity and chemical homogeneity leads to the superior electrochemical properties of the rapidly quenched samples.

The direct evidence of the composition pulling effect and its role in InGaN multiple quantum wells

Direct evidence of composition pulling effect (CPE) in InGaN` quantum wells was obtained by combining energy dispersive x-ray spectrometry (EDS) and scanning tunneling electron microscope (STEM). The indium content increases along the c-axis in the InGaN quantum wells, forming an In-rich sublayer on the surface. The indium content in the In-rich sublayer will reach saturation earlier. After that, the incorporation of indium atoms is hindered, resulting in a decrease in the average indium composition in the InGaN quantum wells. Moreover, an aggregation behavior of indium atoms has been observed in samples with a stronger CPE. This leads to a lot of dark spot defects, seriously deteriorating the luminescence quality. By restricting the migration ability of indium atoms, dark spot defects could be greatly suppressed, and a higher quality InGaN/GaN MQW with higher indium content was obtained.

(Digital Presentation) Improving Oxygen Evolution Reaction Performance and Durability Using Rhombic Dodecahedral Pt3(Ni,X) Nanoparticles with Metal Oxide Supports

The supply infrastructure and production of hydrogen remains a limiting aspect in the introduction of polymer electrolyte fuel cell (PEFC) technologies.[1] The creation of highly efficient electrocatalysts is limited by predominantly carbon-based support systems which corrode readily during the oxygen evolution reaction (OER).[2] In acidic environments, iridium and ruthenium electrocatalysts with unary, binary, and ternary compositions have been used to achieve excellent OER results, however, carbon corrosion remains an issue for performance over long periods of time. The objective of this work is to examine the effect of highly active ternary based Pt3(Ni,X) rhombic dodecahedral nanoframes loaded onto metal oxide supports.Novel platinum-based electrocatalysts have been developed to improve catalytic activity and overall durability in acidic environments. Of note is the creation of binary Pt3Ni in a rhombic dodecahedral shape with a Pt skin synthesized.[3] These nanoparticles demonstrate very high specific/mass activities and are comparably durable over 10,000 potential cycles.Previous work[4] has been able to recreate the Pt3Ni rhombic dodecahedron under different synthesis conditions allowing for more rapid manufacture. These nanoparticles were used in combination with nitrogen-doped carbon support to examine the effects of surface nitrogen as anchoring sites. Examination using XPS, electrochemical stripping, and SEIRAS shows that the nitrogen sites alter the d-band center of surface Pt in addition to creating a more homogenous distribution of the nanoparticles. The addition of a ternary element allows for additional fine tuning of the d-band center of platinum near the particle surface.The oxygen evolution reaction requires a higher potential range which leaves carbon-based support systems susceptible to corrosion.[2] Several metal oxide support systems have been investigated as potential candidates, with a particular focus on material conductivity. Antimony tin oxide (ATO) shows promise as a relatively conductive metal oxide support for OER applications.[2] Furthermore, ATO shows lower dissolution rates when compared to other tin oxides in similar acidic environments.[5] As mentioned, iridium and ruthenium are used predominantly for OER in acidic environments. Therefore, the ternary metal additions (X) used in this work include PtNiIr and PtNiRu based nanoframes. These nanoframes have been successfully loaded onto ATO metal oxide supports. These catalyst support systems show promising OER results, even when compared to carbon supported NFs, as well as excellent durability. Examination was done using Scanning Tunneling Electron Microscopy (STEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), X-ray absorption spectroscopy (XAS), and rotating disk electrode (RDE) electrochemical measurement. This work could lead to significant improvements into electrocatalyst activity and durability which are necessary to implement PEFC technology onto a global scale.

Synthesis and Thermal Degradation of MAl4(OH)12SO4·3H2O with M = Co2+, Ni2+, Cu2+, and Zn2.

The synthesis and thermal degradation of MAl4(OH)12SO4·3H2O layered double hydroxides with M = Co2+, Ni2+, Cu2+, and Zn2+ ("MAl4-LDH") were investigated by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, powder X-ray diffraction, Rietveld refinement, scanning electron microscopy, scanning tunnel electron microscopy, energy-dispersive X-ray spectroscopy, and solid-state 1H and 27Al NMR spectroscopy. Following extensive synthesis optimization, phase pure CoAl4- and NiAl4-LDH were obtained, whereas 10-12% unreacted bayerite (Al(OH)3) remained for the CuAl4-LDH. The optimum synthesis conditions are hydrothermal treatment at 120 °C for 14 days (NiAl4-LDH only 9 days) with MSO4(aq) concentrations of 1.4-2.8, 0.7-0.8, and 0.08 M for the CoAl4-, NiAl4-, and CuAl4-LDH, respectively. A pH ≈ 2 for the metal sulfate solutions is required to prevent the formation of byproducts, which were Ni(OH)2 and Cu3(SO4)(OH)4 for NiAl4- and CuAl4-LDH, respectively. The thermal degradation of the three MAl4-LDH and ZnAl4-LDH in a nitrogen atmosphere proceeds in three steps: (i) dehydration and dehydroxylation between 200 and 600 °C, (ii) loss of sulfate between 600 and 900 °C, and (iii) formation of the end products at 900-1200 °C. For CoAl4-LDH (ZnAl4-LDH), these are α-Al2O3 and CoAl2O4 (ZnAl2O4) spinel. For NiAl4-LDH, a spinel-like NiAl4O7 phase forms, whereas CuAl4-LDH degrades by a redox reaction yielding a diamagnetic CuAlO2 (delafossite structure) and α-Al2O3.

Selective Catalysis for Electrocatalytic Hydrogen Oxidation and Evolution Reactions Via Carbon Nanotube Encapsulation and Oxide Nano-Layer Deposition

Catalysts undergo poisoning and degradation during their utilisation in many different fields. Common examples are the CO poisoning of Pt,1 or the degradation of Pt/C catalysts during start-stop procedures,2 both occurring in polymer electrolyte fuel cells (PEMFCs). Another energy technology that features prominent catalyst degradation is the hydrogen bromine redox flow battery (H2-Br2 RFB). H2-Br2 RFBs are a cheap and efficient solution to large scale energy storage.3 The main hinderance of the technology is the poisoning of the hydrogen evolution reaction/hydrogen oxidation reaction (HER/HOR) catalyst by bromine species which have crossed over the proton exchange membrane.4 Without a revolution in membrane development, this crossover appears unpreventable.5,6 Therefore, we sought to protect the catalyst locally. Two possible solutions were found to impart catalyst selectivity: Pt encapsulation in single-walled carbon nanotubes (SWCNTs) and metal oxide deposition on catalysts via atomic layer deposition (ALD).Platinum nanoparticles were synthesised within the internal cavities of small diameter SWCNTs, through a simple impregnation and drying procedure. High resolution transmission electron microscopy (HRTEM), atomic force microscopy (AFM) and scanning tunnelling electron microscopy (STEM) were used to characterise the particles and demonstrate that they were confined within the SWCNTs. The typical hydrogen under potential deposition peaks were observed on a cyclic voltammogram of the sample, whereas the oxide region was heavily suppressed compared to Pt/C. Some diffusion limitation was observed during the HOR, indicating that the electrolyte diffusion pathway is through the SWCNTs, but the same mass transport limited current was attained. The oxygen reduction reaction (ORR) mass transport limited current was much lower than expected for Pt (2 mA cm-2), indicating a selectivity for hydrogen over oxygen. The stability of these platinum nanoparticles in the presence of bromide/tribromide solution was vastly increased compared to the standard 50% Pt/C catalyst, shown by x-ray photoelectron spectroscopy (XPS) and electrochemistry. It is proposed that this effect is caused by steric and electrostatic repulsion of the large tribromide ion by the SWCNT cavity (internal diameter of 2 nm). The encapsulated platinum also features a vastly higher mass activity when cycled in a cell, indicating better Pt utilization due to the small particle size. This opens a new route for imparting selective access to active sites of a catalyst, hence increasing the stability of the catalyst, a potential solution to many problems faced by technologies that rely on catalysts.Another possible solution to prevent catalyst poisoning is through a protective oxide coating on its surface. ALD was chosen due to its highly controllable, conformal deposition, but also as it can be applied to a wide range of commercial catalysts, making it highly applicable for real world applications. Vanadium oxide was deposited on a commercial 50% Pt/C catalyst via ALD, chosen for its precise control in both layer thickness and conformity on the surface of the catalyst. XPS and HRTEM confirmed the ALD process had deposited vanadium oxide species on the catalyst. The HOR was unaffected by this deposition, indicating diffusion of hydrogen could occur through the oxide layer. Stability of the material in the presence of bromide/tribromide solution was superior to the uncoated commercial catalyst, showing the oxide coating successfully protected the catalyst. Again, whilst it has been demonstrated for bromine poisoning of Pt, this approach should be applicable to many poisoning problems facing other catalysts/applications.(1) Li, Q.; He, R.; Gao, J.-A.; Jensen, J. O.; Bjerrum, N. J. The CO Poisoning Effect in PEMFCs Operational at Temperatures up to 200°C. J. Electrochem. Soc. 2003, 150 (12), A1599. https://doi.org/10.1149/1.1619984.(2) Stühmeier, B. M.; Selve, S.; Patel, M. U. M.; Geppert, T. N.; Gasteiger, H. A.; El-Sayed, H. A. Highly Selective Pt/TiOx Catalysts for the Hydrogen Oxidation Reaction. ACS Appl. Energy Mater. 2019, 2 (8), 5534–5539. https://doi.org/10.1021/acsaem.9b00718.(3) Singh, N.; McFarland, E. W. Levelized Cost of Energy and Sensitivity Analysis for the Hydrogen-Bromine Flow Battery. J. Power Sources 2015, 288, 187–198. https://doi.org/10.1016/j.jpowsour.2015.04.114.(4) Lin, G.; Chong, P. Y.; Yarlagadda, V.; Nguyen, T. V.; Wycisk, R. J.; Pintauro, P. N.; Bates, M.; Mukerjee, S.; Tucker, M. C.; Weber, A. Z. Advanced Hydrogen-Bromine Flow Batteries with Improved Efficiency, Durability and Cost. J. Electrochem. Soc. 2016, 163 (1), A5049–A5056. https://doi.org/10.1149/2.0071601jes.(5) Hugo, Y. A.; Kout, W.; Sikkema, F.; Borneman, Z.; Nijmeijer, K. In Situ Long-Term Membrane Performance Evaluation of Hydrogen-Bromine Flow Batteries. J. Energy Storage 2020, 27, 101068. https://doi.org/10.1016/j.est.2019.101068.(6) Tucker, M. C.; Cho, K. T.; Spingler, F. B.; Weber, A. Z.; Lin, G. Impact of Membrane Characteristics on the Performance and Cycling of the Br2-H2 Redox Flow Cell. J. Power Sources 2015, 284, 212–221. https://doi.org/10.1016/j.jpowsour.2015.03.010. Figure 1

High-Resolution Lithographic Patterning with Organotin Films: Role of CO2 in Differential Dissolution Rates

Details of the chemistry enabling the patterning of organotin photoresists to single-digit-nm resolution continue to engage study. In this report, we examine the contributions of atmospheric gases to the differential dissolution rates of an n-butyltin oxide hydroxide photoresist. Cryo scanning tunneling electron microscopy (cryo-STEM) produces a micrograph of the latent image of an irradiated resist film, readily distinguishing exposed and unexposed regions. Temperature-programmed desorption mass spectrometry (TPD-MS) and cryo electron energy loss spectroscopy (cryo-EELS) show that irradiated films are depleted in carbon through desorption of butane and butene. Upon aging in air, irradiated films absorb H2O, as previously established. TPD-MS also reveals a previously unrecognized absorption of CO2, which correlates to a heightened dissolution contrast. This absorption may play an active role in determining intrinsic patterning performance and its variability based on changes in atmospheric-gas composition.

Real-space observation of ferroelectrically induced magnetic spin crystal in SrRuO3

Unusual features in the Hall Resistivity of thin film systems are frequently associated with whirling spin textures such as Skyrmions. A host of recent investigations of Hall Hysteresis loops in SrRuO3 heterostructures have provided conflicting evidence for different causes for such features. We have constructed an SrRuO3-PbTiO3 (Ferromagnetic – Ferroelectric) bilayer that exhibits features in the Hall Hysteresis previously attributed to a Topological Hall Effect, and Skyrmions. Here we show field dependent Magnetic Force Microscopy measurements throughout the key fields where the ‘THE’ presents, revealing the emergence to two periodic, chiral spin textures. The zero-field cycloidal phase, which then transforms into a ‘double-q’ incommensurate spin crystal appears over the appearance of the ‘Topological-like’ Hall effect region, and develop into a ferromagnetic switching regime as the sample reaches saturation, and the ‘Topological-like’ response diminishes. Scanning Tunnelling Electron Microscopy and Density Functional Theory is used to observe and analyse surface inversion symmetry breaking and confirm the role of an interfacial Dzyaloshinskii–Moriya interaction at the heart of the system.

Improving Electrochemical Activity of Rhombic Dodecahedral Pt3(Ni,X) Nanoparticles Using Transition Metal Additions

Large scale use of polymer electrolyte membrane fuel cell (PEMFC) technology remains in its infancy owing to high costs, performance and durability challenges. Novel platinum-based electrocatalysts have been developed to improve catalytic activity and overall durability in acidic environments. Of note is the synthesis of binary Pt3Ni in a rhombic dodecahedral shape with a Pt skin.[1] These nanoparticles demonstrate very high specific/mass activities and are comparably durable over 10,000 potential cycles. The objective of this work is to further improve on the Pt3Ni rhombic dodecahedral nanoframes using ternary additions Pt3(Ni,X), where X denotes an additional transition metal.Previous work[2] has been able to recreate the Pt3Ni rhombic dodecahedron under different synthesis conditions. These nanoparticles were used in combination with nitrogen-doped carbon support to examine the effects of surface nitrogen as anchoring sites. Examination using XPS, electrochemical CO stripping, and SEIRAS shows that the nitrogen sites alter the d-band center of surface platinum in addition to creating a more homogeneous distribution of the nanoparticles.The addition of a ternary element allows for additional fine tuning of the d-band center of platinum near the particle surface. This leads to an increase in overall activity over binary systems when examining electrocatalyst volcano plots. In addition, ternary elements could lead to a reduction in the rate of nickel leeching over repeated electrochemical cycles.DFT studies[3] examined the adsorption energy of ternary Pt3(M,X) where M is another transition metal different than X. The model arranged the ternary surfaces into intermetallic, Pt skin, and Pt skin with subsurface intermetallic layers. From this work, Rankin recommended the investigation of Pt skin ternary systems using Pd, Rh, Ru, Ir, and Os; as well as a Pt-Ni-Cu system with a subsurface intermetallic layer.Ternary Pt3(Ni,X) nanoparticle systems have been investigated previously but have not been directly synthesized into a rhombic dodecahedral shape. Thus, the scope of this work is to investigate Pt3(Ni,X) systems where X includes Cu, Pd, Rh, Ru, Ir, and Os. Using similar synthesis methods,[2] rhombic dodecahedral nanoparticles will be created with a Pt skin. Examination will follow using Scanning Tunneling Electron Microscopy (STEM), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), electrochemical CO stripping, and thin film rotating disk electrode (RDE) measurement.Successful candidates will be added with modified carbon supports (nitrogen doping, additions of polybenzimidazole (PBI), modifications of pore structure) with the goal of improving local mass transport at the support surface. Further annealing may also be investigated to create ordered intermetallic layers under the Pt skin which have been shown to improve activity. This work could lead to significant improvements into electrocatalyst activity and durability which are necessary to implement PEMFC technology onto a global scale.

Calcium alginate-TiO2/SiO2 nanocomposite for glucose conversion to 5-hydroxymethylfurfural

The sodium alginate biopolymer used to form calcium alginate-TiO2/SiO2 nanocomposite has been successfully synthesized. The first stage is synthesis of TiO2/SiO2 composites by the sol-gel method using tetraethyl orthosilicate (TEOS) and titanium isopropoxide (TTIP) precursors. Calcium alginate nanocomposite is formed from the crosslinking process between Ca2+ ions from CaCl2.2H2O with sodium alginate combined with TiO2/SiO2 composites, characterized by Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and Tunneling Electron Microscopy (TEM). The average particle size of TiO2/SiO2 composite on the surface of calcium alginate obtained by TEM is about 50 nm. The application of calcium alginate-TiO2/SiO2 nanocomposite as catalyst is used for conversion of glucose into 5-hydroxymethylfurfural (HMF) using dimethyl sulfoxide (DMSO) solvents. The best glucose conversion obtained at 140 °C for 4 hours is 97 % and optimum HMF yield obtained at 140 °C and 5 hours is 40 %. Nanocomposites based on sodium alginate biopolymers combined with TiO2/SiO2 composites can be developed as new superior materials and promising catalysts because it is easily obtained and biodegradable.

NaAlg-PVA-g-AAm/ZnO nanocomposite hydrogel as material of wound dressing: synthesis and characterization

In this study, sodium alginate and polyvinyl alcohol grafted acrylamide with modified ZnO nanoparticles to nanocomposite hydrogel NaAlg-PVA-g-AAm/ZnO have been successfully synthesized. The characterizations of hydrogels were supported by Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Tunneling Electron Microscopy and Energy Dispersive X-Ray (TEM-EDX). The image of TEM obtained shows that ZnO nanoparticle are distributed evenly with about 70 nm diameter in hydrogel nanocomposite. The results for NaAlg-PVA-g-AAm nanocomposite hydrogel modified ZnO nanoparticles was obtained the best nanocomposite at 32.21 ppm Zn2+ concentration. It has Zn2+ ion maximum loading capacity at 80 %, maximum release capacity of 25 % measured by AAS, and its water maximum swelling capacity is 230.20 (g/g). While the maximum swelling capacity for NaAlg-PVA-g-AAm nanocomposite hydrogel is 106.30 (g/g). From in-vitro antibacterial activity test, S.aureus (gram positive bacteria) has more resistance than P. Aeruginosa (gram negative bacteria) in which S. aureus inhibition percentage is 60.22 % and P. Aeruginosa is 40.10 % with the minimum inhibitory concentration of 31.25 ppm.

Decoration of Voids with Rhenium and Osmium Transmutation Products in Neutron Irradiated Single Crystal Tungsten

High temperature, neutron irradiated single crystal tungsten,with a post irradiation composition of W-1.20±0.11at.%Re-0.11±0.05at.%Os0.03±0.01at.%Ta was characterised using a combination of Atom ProbeTomography (APT) and Scanning Tunnelling Electron Microscopy (STEM). APTshowed that within nanoscale clusters of Re/Os, the atomic density wasabove the theoretical limit. Complimentary High Angle Annular Dark Field(HAADF) imaging shows that some clusters contain voids at their centrewhich are leading to APT aberrations and enhancing the atomic density.High resolution Energy Dispersive X-ray (EDX) spectroscopy shows thatvoids are decorated with a shell of rhenium with a small osmium clusterto one side.

Photothermally Active Upconversion Core–Shell NaGdF4:Yb:Tm@Cu Nanostructures: Synthesis and Theranostic Properties

AbstractNear infrared (NIR) active nanostructures with applications in imaging and therapy have attracted significant attention in cancer diagnosis and treatment. NIR active structures can provide molecular images, penetrating from deep within tissue with high resolution. In addition, particles with photothermal properties can lead to a new era of cancer diagnostics. The first synthesis of core–shell NaGdF4:Yb:Tm@Cu (NGF@Cu) nanostructures is reported. NGF@Cu particles have molecular imaging and photothermal activation properties owing to an upconverting core and metallic shell. The upconversion core means that cancer cell location can be recognized and the Cu‐based photothermal therapy is subsequently able to disrupt the cells. NGF@Cu characterization studies, including scanning tunneling electron microscopy and energy dispersive X‐ray spectroscopy mapping, confirm the core–shell structure with Cu as the shell. This study demonstrates the use of a single nanostructure for diagnosis in the NIR therapeutic window (650–1400 nm) and photothermal therapy, with a core–shell particle efficiency of ≈36.3%.

Ozone-assisted catalysis of CO: In situ Fourier transform IR evidence of the cooperative effect of a bimetallic Ag-Pd catalyst

The room-temperature oxidation of CO using ozone-assisted catalysis (OAC) over monometallic or bimetallic catalysts supported on γ-Al2O3 is presented. Within the tested particle size range, ozone decomposition was insensitive to the size of the Ag particles (6.6–11.9 nm) at weight hourly space velocities of up to 360 L·g−1·h−1. Among the tested monometallic catalysts (Ag Pd, Fe, Mn, and Cu), Ag showed the highest activity for CO oxidation. Bimetallic catalysts (Ag-M or Pd-M where M = Cu, La, Ru, and Fe) were also considered by adding a second metal or perovskite oxide (LaFeO3) to Ag. A cooperative effect was observed with the bimetallic Ag-Pd catalyst for the OAC of CO oxidation at room temperature, whereas the other bimetallic catalysts showed slightly lower performance compared to the monometallic catalyst. A high ozone utilization efficiency of 0.94 was achieved with the bimetallic Ag-Pd/γ-Al2O3 catalyst. High-angle annular dark-field scanning tunneling electron microscopy (HAADF) and energy dispersive X-ray (EDX) spectroscopy measurements confirmed the proximity of the two components, which is essential for their interaction. The in situ FTIR measurements revealed that the cooperative effect in the bimetallic Ag-Pd catalyst involved modification of CO adsorption and the suppression of product accumulation. Two typical IR absorption bands of linear- (2090 cm−1) and bridge-CO (1918 cm−1) on Pd disappeared in the presence of Ag nanoparticles. Thus, the presence of Ag in contact with Pd inhibited the accumulation of carbonates, which led to enhanced catalytic performance. Adsorption site-dependent CO oxidation on Pd was also confirmed by the in situ Fourier transform IR measurement.

Revealing multimode resistive switching in Cu-O nanostructures using conductive atomic force microscopy

We demonstrate the nanoscale multimode resistive switching in copper oxide nanostructures using conductive atomic force microscopy (cAFM). The cross-sectional transmission electron microscopy (XTEM) and scanning tunnelling electron microscopy – high angle angular dark field (STEM-HADDF) imaging confirms the formation of Cu-O nanostructures. In addition, x-ray photoelectron spectroscopy (XPS) is used to study the chemical composition of Cu-O nanostructures. Current-voltage characteristics measured by conductive atomic force microscopy (cAFM) reveals that the filament forms in multistep processes, instead the rapid one, indicating the multimode resistive switching. The presence of multimode RS is corroborated to the defect-induced conduction mechanism across the Cu-O nanostructures. The present study should open up a new avenue to understand the conduction mechanism and to design an advanced nanoscale device.

Interfacial Interactions in van der Waals Heterostructures of MoS2 and Graphene.

Interfacial coupling between neighboring layers of van der Waals heterostructures (vdWHs), formed by vertically stacking more than two types of two-dimensional materials (2DMs), greatly affects their physical properties and device performance. Although high-resolution cross-sectional scanning tunneling electron microscopy can directly image the atomically sharp interfaces in the vdWHs, the interfacial coupling and lattice dynamics of vdWHs formed by two different types of 2DMs, such as semimetal and semiconductor, are not clear so far. Here, we report the ultralow-frequency Raman spectroscopy investigation on interfacial couplings in the vdWHs formed by graphene and MoS2 flakes. Because of the significant interfacial layer-breathing couplings between MoS2 and graphene flakes, a series of layer-breathing modes with frequencies dependent on their layer numbers are observed in the vdWHs, which can be described by the linear chain model. It is found that the interfacial layer-breathing force constant between MoS2 and graphene, α0⊥(I) = 60 × 1018 N/m3, is comparable with the layer-breathing force constant of multilayer MoS2 and graphene. The results suggest that the interfacial layer-breathing couplings in the vdWHs formed by MoS2 and graphene flakes are not sensitive to their stacking order and twist angle between the two constituents. Our results demonstrate that the interfacial interlayer coupling in vdWHs formed by two-dimensional semimetals and semiconductors can lead to new lattice vibration modes, which not only can be used to measure the interfacial interactions in vdWHs but also is beneficial to fundamentally understand the properties of vdWHs for further engineering the vdWHs-based electronic and photonic devices.