Characterization Of Surface Structure Research Articles

Ag modified Cu hollow fiber for gas-phase CO<sub>2</sub> electrocatalytic conversion to oxygenates

<p indent="0mm">The conversion of CO₂ to oxygenates driven by renewable electricity is of great importance, since not only the carbon emission would be reduced by utilizing CO₂ as feedstock, but also the renewable energy could be stored as high value-added chemicals. The development of gas-phase electrocatalytic system is significant for the practical application of CO₂ electroreduction, which could avoid the obstacles of liquid-phase CO₂ electroreduction system, such as the insufficient CO₂ solubility and separation dilemma of soluble products. In this work, Ag modified Cu hollow fibers via galvanic replacement are utilized as the electrode for gas-phase CO₂ electroreduction to produce multi-carbon oxygenates. Hollow fiber with its large surface area, adjustable pore structure, good chemical stability and conductivity shows unique advantage in electrocatalysis application. The morphology, surface and bulk structure characterizations of Ag-Cu hollow fiber electrodes indicate that the modification via galvanic replacement forms Ag nanodendrites in different scales on the surface of Cu hollow fiber electrodes. The relationship between the surface structures and electrocatalytic performances of the as-prepared Ag-Cu electrodes is also unveiled. Compared with Cu hollow fiber electrode, not only the current densities but also the faradaic efficiencies of C₃ products (propanal and acetone) for Ag-Cu hollow fiber electrodes are greatly improved. 0.1wt.% Ag-Cu hollow fiber electrode shows an elevated current density of −0.19, −0.35 and <sc>−0.72 mA cm⁻²</sc> at the potential of −1.4, −1.6 and <sc>−1.8 V</sc> vs. counter electrode respectively, compared with those of −0.11, −0.16 and <sc>−0.33 mA cm⁻²</sc> for Cu hollow fiber. And 0.1wt.% Ag-Cu hollow fiber electrode also gives promoted faradaic efficiencies of not only C₂ product ethanol (with a yield of <sc>56 nmol cm⁻² h⁻¹),</sc> but also C₃ product acetone. Although the further increase of Ag loading narrows the current density difference comparing with Cu hollow fiber, the faradaic efficiencies and yields of C₃ products propanal and acetone are greatly improved for 0.3wt.% and 1wt.% Ag-Cu hollow fiber electrodes. 1wt.% Ag-Cu hollow fiber electrode provides faradaic efficiencies of 19% for propanal and 7% for acetone with a current density of <sc>0.13 mA cm⁻²</sc> at the potential of −1.4 V vs. counter electrode. And its propanal yield reaches <sc>57 nmol cm⁻² h⁻¹,</sc> even higher than the ethanol yield of other electrocatalysts in reported gas-phase CO₂ electroreduction works, indicating the better activity of Ag-Cu hollow fiber electrode on multi-carbon product formation. The modification of Ag dendrites on hollow fiber surface not only promotes the activity of gas-phase CO₂ electroreduction, but also facilitates the formation of multi-carbon oxygenates. The fractal dendrite structure of Ag forms abundant conductive networks on the surface of Cu hollow fiber electrode, which facilitates the electron transport and mass transfer processes, leading to superior kinetics and elevated current densities for gas-phase CO₂ electroreduction. Also, the high curvature surface of Ag dendrites induces high local electric field and high local concentration of CO₂ as well as active intermediates, which would be beneficial for the C-C coupling and the formation of multi-carbon products. The present study provides an inspiration and scientific instruction for designing and constructing gas-phase CO₂ electrocatalytic systems to produce multi-carbon oxygenates with high activity and high selectivity.

Realizing long-term cycling stability and superior rate performance of 4.5 V–LiCoO2 by aluminum doped zinc oxide coating achieved by a simple wet-mixing method

The thermodynamic instability of the layered structure and severe side reactions with liquid carbonate electrolytes have been considered as the key obstacles for the practical application of LiCoO2 (LCO) at voltages of above 4.5 V (versus Li/Li+). Here, we have developed a facile wet-mixing synthetic method which can realize thin and uniform surface coating of aluminum doped zinc oxide (AZO) on LCO particles. The half-cells employing the AZO modified LCO display excellent 4.5 V cycle performance with the discharge capacity retention of 80% after 650 cycles and superior rate capability of 8C capacity of 100 mAh g−1. Combined with surface structure characterizations and bond valence calculations, it is revealed that the stabilized surface and superior kinetic properties contribute to the performance enhancement of AZO modified LCO at 4.5 V. This work demonstrates AZO a suitable coating material for surface protection of cathode materials for high-voltage applications. The preparation method developed in this work is also suitable for mass production and applicable to fabrication of other types of battery materials.

Hierarchical Micro-/Nano-Structures on Polycarbonate via UV Pulsed Laser Processing.

Hierarchical micro/-nanostructures were produced on polycarbonate polymer surfaces by employing a two-step UV-laser processing strategy based on the combination of Direct Laser Interference Patterning (DLIP) of gratings and pillars on the microscale (3 ns, 266 nm, 2 kHz) and subsequently superimposing Laser-induced Periodic Surface Structures (LIPSS; 7–10 ps, 350 nm, 100 kHz) which adds nanoscale surface features. Particular emphasis was laid on the influence of the direction of the laser beam polarization on the morphology of resulting hierarchical surfaces. Scanning electron and atomic force microscopy methods were used for the characterization of the hybrid surface structures. Finite-difference time-domain (FDTD) calculations of the laser intensity distribution on the DLIP structures allowed to address the specific polarization dependence of the LIPSS formation observed in the second processing step. Complementary chemical analyzes by micro-Raman spectroscopy and attenuated total reflection Fourier-transform infrared spectroscopy provided in-depth information on the chemical and structural material modifications and material degradation imposed by the laser processing. It was found that when the linear laser polarization was set perpendicular to the DLIP ridges, LIPSS could be formed on top of various DLIP structures. FDTD calculations showed enhanced optical intensity at the topographic maxima, which can explain the dependency of the morphology of LIPSS on the polarization with respect to the orientation of the DLIP structures. It was also found that the degradation of the polymer was enhanced for increasing accumulated fluence levels.

Synthesis of organic photoresist of Hibiscus tiliaceus L. flowers for patterning with X-Ray and UV exposure

Photoresist is an essential chemical used in patterning the microelectronic devices. To ensure the sustainability of the supply of raw materials of microelectronics industry such as photoresist need to look for alternative materials that are more eco-friendly. This study used natural ingredients of Hibiscus tiliaceus L. flowers extract. The manufacture of photoresists carried in four stages, the manufacture of Hibiscus tiliaceus L. flowers extract, the manufacture of thin film Hibiscus tiliaceus L. flowers extract, the manufacture of resist and the manufacture of thin film photoresist. The manufacture of Hibiscus tiliaceus L. flowers extract is done with mass fraction variations using distillation methods. The optical properties of Hibiscus tiliaceus L. flowers extract was characterized using ocean optic Vis-NIR USB 4000. The functional group was characterized using the Perkin Elmer Frontier FT-IR, while the surface structure was characterized using the Digital CCD Microscope MS-804 Scopeman and the electrical properties were characterized using the Elkahfi 100 I-V Meter. The density of the resist is characterized by the mass per volume method. Thin film of photoresist is grown through the spin coating method with a voltage of 10 V for 60 s and heating to a temperature of 200°C for characterization of surface structures and optical properties. Photoresist is tested for sensitivity by giving exposure to UV and X-ray radiation sources to photoresist material. The resulting photoresist has a value of absorbance that is located in the wavelength range of 350 to 1050 nm with a maximum absorbance value of 0.07 to 0.3 at the wavelength of the g-line, h-line and i-line.

Realization of Rapid Large-Size 3D Printing Based on Full-Color Powder-Based 3DP Technique.

The powder-based 3DP (3D printing) technique has developed rapidly in creative and customized industries on account of it’s uniqueness, such as low energy consumption, cheap consumables, and non-existent exhaust emissions. Moreover, it could actualize full-color 3D printing. However, the printing time and size are both in need of upgrade using ready printers, especially for large-size 3D printing objects. Given the above issues, the effects of height and monolayer area on printing time were explored and the quantitative relationship was given in this paper conducted on the specimens with a certain gradient. On this basis, an XYX rotation method was proposed to minimize the printing time. The mechanical tests were conducted with three impregnation types as well as seven printing angles and combined with the characterization of surface structure based on the scanning electron microscope (SEM) digital images to explore the optimum parameters of cutting-bonding frame (CBF) applied to powder-based 3D printing. Then, four adhesives were compared in terms of the width of bonded gap and chromatic aberration. The results revealed that ColorBond impregnated specimens showed excellent mechanical properties which reached maximum when printed at 45° to Z axis, and α-cyanoacrylate is the most suitable adhesive to bond full-color powder-based models. Finally, an operation technological process was summarized to realize the rapid manufacturing of large-size full-color 3D printed objects.

Investigation of Corrosion Resistance Enhancement for Biodegradable Magnesium Alloy by Ball Burnishing Process

Magnesium and magnesium-based alloys are considered ideal materials for implants in orthopedic treatment because their stiffness is close to that of human bones, and they can be absorbed gradually in the human organism. However, a major issue in their actual application is that the corrosion speed of Mg alloys is very high in aggressive environments such as the human fluids. In previous studies, many approaches have been attempted to enhance the corrosion resistance of Mg alloys. In this research, ball burnishing, a mechanical surface finishing process, is applied to improve the corrosion resistance of Mg alloys by changing its surface properties. The influence of the burnishing parameters on the corrosion resistance is investigated, and the corrosion of a treated and non-treated sample are compared. The test material used is the AZ31 Mg alloy. Firstly, a comprehensive review of the effect of burnishing on the final microstructures is reported. The influence of burnishing on grain size, work-hardened layer thickness, crystal orientation, and residual stress of the sample is discussed. Secondly, by conducting an especially designed long-term immersion test, the mass loss and surface evolution of each sample are evaluated. The experimental results indicate that, under proper processing conditions, the mass loss of the treated sample (8.8 mg) can be reduced to 36% of the non-treated one (24.2 mg). To elucidate the mechanism behind corrosion resistance enhancement by burnishing, the samples treated with the optimal processing parameters found are immersed in an aggressive solution for 1, 3, 5, and 7 days. From the results of mass loss measurement and surface structure characterization, it was found that, among pitting, general, and intergranular corrosion, pitting corrosion is the dominant corrosion mechanism. The holes enlarge because pits combine together, representing the greatest portion of mass loss. The main mechanism enhancing corrosion resistance is the size reduction of the grains on the surface induced by ball burnishing, causing a denser distribution of corrosion products in the immersion test. These corrosion products protect the material underneath accelerated corrosion.

The new external ion-beam station at the Demokritos Tandem 5.5 MV accelerator: A unique analytical tool in the fields of cultural heritage and environmental science

At the 5.5 MV Tandem accelerator of the Institute of Nuclear Physics of NCSR Demokritos, Athens, a new external ion-beam set-up has been recently installed. The aim of this development was to establish a complete experimental set-up integrating the analytical capabilities of the PIXE, RBS and PIGE techniques, so that a complete elemental and near surface structural characterization of samples/artifacts to be attained in an almost non-destructive way and without any limitation concerning their size or conductive state. A careful 3D mechanical drawing optimized the experimental parameters of the set-up so that the special requirements imposed for optimum performance of the aforementioned techniques to be fulfilled.The first applications were focused in the quality control of tagged materials (technologically authentic replicas of attic ceramics and in coatings used by conservators for paintings).

Surface Structure Characterization of Shape and Size Controlled Pd Nanoparticles by Cu UPD: A Quantitative Approach.

The search for new surface sensitive probes that characterize the surface structure of shape and size-controlled nanoparticles is an interesting topic to properly understand the correlations between electrocatalytic properties and surface structure at the nanoscale. Herein, we report the use of Cu UPD to characterize, not only qualitatively but also quantitatively, the surface structure of different Pd nanoparticles with controlled particle shape and size. Thus, Pd nanoparticles with cubic, octahedral and rhombic dodecahedral shapes, that is, with preferential {100}, {111}, and {110} surface structures, respectively, were prepared. In addition, cubic Pd nanoparticles with different particles sizes and spherical (2–3 nm) Pd nanoparticles were also synthesized. Based on the Cu UPD results on Pd single crystals, a new approach is proposed to qualitatively and quantitatively determine the percentages of {100}, {111}, and {110} surface domains present at the surface of the different shape and size controlled Pd nanoparticles. The results reported clearly show the benefits of this Cu UPD to get detailed information of the surface structure of the nanoparticles according to their particle shape and size.

Activation of persulfate by a novel magnetic CuFe2O4/Bi2O3 composite for lomefloxacin degradation

In this paper, magnetic CuFe2O4/Bi2O3 composite was successfully fabricated by a simple sol–gel combustion method with an excellent activity in the activation of persulfate (PS) for lomefloxacin (LOM) degradation. The surface morphology and structure characterizations of CuFe2O4/Bi2O3 were carried out by X-ray diffraction, scanning electron microscope, transmission electron microscope, N2 physical adsorption/desorption and vibration magnetometer measurements. The CuFe2O4/Bi2O3 synthesized exhibited high catalytic activity and good stability, it could degrade 77.19% of LOM at the natural pH (6.08), more efficient than CuFe2O4. Subsequently, the catalytic performances of CuFe2O4/Bi2O3 during LOM degradation were studied comprehensively under different initial conditions (catalyst dosage (0.6–1.8 g/L), PS dosage (0.6–1.8 g/L), initial pH value (3.0–11.0)). Also, the main active radicals (SO4− and OH) were determined by the radical scavenging experiment, which indicated that OH had a higher contribution to remove LOM than SO4− in CuFe2O4/Bi2O3/PS system. Moreover, the mechanism of the CuFe2O4/Bi2O3/PS system for LOM degradation was further proposed and the possible degradation pathways of LOM in CuFe2O4/Bi2O3/PS system were deduced. Furthermore, activated sludge inhibition test was performed to determine the variation of toxicity of the LOM during the degradation process. In a word, the CuFe2O4/Bi2O3 catalyst has a high catalytic efficiency and a short degradation period, indicating that it was a promising catalyst towards LOM wastewater treatment, which had a great potential in environmental protection.

Material flow influence on the quality of molded parts

This paper focuses on a new occurrence mechanism of the flow marks, which appear on the surface of injection-molded parts, through characterization of the part surface structure. Injection-molded parts involving long flow lengths can exhibit visible flow defects characterized by alternating glossy and dull bands on the polymer surface, which have approximately the same direction with the material flow front. These flow defects are considered to have strong negative effect on the appearance of the molded component and thus on the perceived quality. The reasons for the appearance of these stripes are not entirely clear. Defect flow marks (shiny areas) were cut from the molded part and analyzed using optical microscopy, Fourier transform infrared spectroscopy, laser Raman spectroscopy and scanning electron microscopy coupled with energy-dispersive X-ray (SEM/EDX) spectroscopy. Raman spectra detected differences between spectra of defect area and of the reference one. The EDX analysis revealed that the defect area contains slightly more quantity of talc (Mg and Si). This happened because of material flow morphology in the areas where the molded part presents ribs. The flow of melted resin through an enlargement (rib) results in a decrease in flow velocity, and consequently, a pressure rise will occur and it also involves a vortex development. Therefore, the shear stress in this area is higher than upstream and downstream ones, and it will cause a delay of the flow stream, a premature solidification of the melted resin and ribs flow marks occurrence.

3D Electron microscopy characterization of Ag mound-like surface structures made by femtosecond laser surface processing

Laser processing of metal surfaces by ultrafast pulse lasers is a developing technology with many potential uses including applications in heat transfer, medical implants, and tribology. Laser processed silver surfaces has several potential applications such as biomedical devices, antibacterial surfaces, and chemical sensors. However, there is a lack of previous research on laser processing of silver is more difficult to process compared with other metals. A newly investigated dual-pulse femtosecond laser surface processing technique was capable of producing self-organized, micro/nanoscale surface features on silver where single-pulse techniques had previously failed. Three-dimensional (3D) scanning electron microscopy (SEM) was used to examine mound-like structures produced by this new method to determine their composition and formation processes. The interior microstructure revealed that the mounds were comprised mostly of resolidified Ag grains with approximately 1% porosity. Hydrodynamically-driven fluid flow was the primary process that forms these surface structures without significant oxidation.

Surface structure characterization by X-ray photoelectron diffraction of Sn ultra-thin films deposited on Pd(111)

The formation of surface alloys obtained by annealing ultra-thin films of Sn deposited on a Pd(111) surface was characterized by X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and X-ray photoelectron diffraction (XPD). Annealing the surface at 600 K produced a (3x3)R30° LEED pattern, and the comparison between experimental and theoretical XPD results indicated the formation of a corrugated bi-dimensional Pd2Sn surface alloy, with Sn atoms being present not only on the outmost layer but also at least on the second internal layer.

Studi Variasi Konsentrasi NaOH dan H2SO4 Untuk Memurnikan Silika Dari Abu Sekam Padi Sebagai Adsorben Ion Logam Pb2+ dan Cu2+

A study of variations in the concentration of NaOH and H2SO4 to purify silica from rice husk ash and its application as adsorbent of Pb2+ and Cu2+ Metal Ions. The NaOH concentrations used were 8%, 9%, 10%, 11%, 12% and 13% and H2SO4 concentrations were 5.4%, 8.16%, 10.88%, and 13.61%. The process of adsorption of Pb2+ and Cu2+ metal ions was carried out at pH (3, 4, 5, 6) and silica masses. The results showed the silica yield obtained in the form of white powder. The highest silica content at 12% NaOH concentration of 41.81% with a purity of 89.09% and H2SO4 concentration is 10.88% at 65.39% with a purity of 94.94% initial content 86.02%. The results of surface structure characterization using Scanning Electron Microscope (SEM) average size of particle diameter was 0.030 µm. Optimal adsorption process of Pb2+ and Cu2+ metal ions using silica from rice husk occurred at pH 6 and the adsorbent mass was 0.3 gram, the adsorption efficiency was 98% and 86.25% respectively with adsorption capacity of 0.96 mg/g for metal Pb2+ and 0.83 mg/g for Cu2+ metals.

Superior dye degradation using SnO2-ZnO hybrid heterostructure catalysts

We investigated the efficiency of oxide based hierarchical heterostructure as adsorbent for the treatment of organic dyes, Methyl orange (MO) and Methylene Blue (MB), containing solution. Nanocrystals such as ZnO nanorods (at various temperatures of 30, 60 and 75 °C) and SnO2 nanoparticles were synthesized by electrodeposition method and hydrothermal approaches, respectively. SnO2-ZnO heterostructures were formed by spin coating SnO2 nanoparticles on ZnO nanorods matrix to form a heterostructured film. The surface morphologies and structural characterization of as-prepared heterostructures were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. While, absorption spectra of all samples were examined by UV-vis diffuse reflectance spectroscopy. The photocatalytic activities of as-prepared samples for organic dyes degradation were tested under UV light as model reaction. The SnO2-ZnO heterostructured photocatalyst showed superior activities than individual ZnO and SnO2 nanocrystals. This heightened behavior was attributed to its better charge separation capability and the slow charge recombination originating due to difference in energy values of conduction band edges of SnO2 and ZnO. The SnO2-ZnO heterostructure demonstrated better stability and recyclability up to five times, which is highly desirable for potential industrial applications including dye degradation and wastewater treatment systems.

Fabrication of sensitive SWCNT sensor for trace level detection of reducing and oxidizing gases (NH3 and NO2) at room temperature

In the present work, rare dense and long network of single wall carbon nanotubes (SWCNTs) were successfully grown on Fe (Iron) based catalyst Si (Silicon) substrate through Plasma enhanced chemical vapour deposition (PECVD) technique at an operating temperature of 650 °C. The catalyst has been deposited by RF-Sputtering technique. The acetylene (C2H2) was used as the carbon source gas. The surface morphology and structural characterization of as grown SWCNTs have been properly done by various techniques like FESEM, HRTEM, and Raman Spectroscopy. From as grown SWCNTs, highly sensitive SWCNT sensor was fabricated for the trace level detection of NH3 and NO2 at room temperature. Different sensor characteristics like sensor response, repeatability, stability, resistance variation and selectivity of the as fabricated SWCNT sensor were investigated properly for both the gases (NH3 and NO2) and it was found that all the characteristics are in good agreement with reported work. In addition of this, the effect of operating temperature on sensor response was also conducted and it was found that sensitivity decreases with increasing temperature because desorption enhances with increasing temperature. Quick sensor response/recovery characteristics were obtained from the fabricated sensor and is a step forward towards security reasons in various sectors.

Fabrication and characterization of boron nitride reinforced Ni–W nanocomposite coating by electrodeposition

Ni–W/BN nanocomposite coating was successfully synthesized by direct current (DC) electrodeposition in the present work. Their surface morphology, structural characterization and electrochemical properties were investigated by SEM, XRD, AFM, XPS and EIS methods. The influence of BN on the properties of Ni–W/BN nanocomposite coating were discussed. Results indicate that the electrodeposited coatings were uniform and compact without cracks, containing homogeneously distributed 2–4 wt% BN particles and 22–29 wt% W. The growth rate of Ni–W/BN was about 0.4 μm min−1 at 2 A dm−2 and its grain size was about 11–13 nm. The average roughness values Ra of Ni–W/BN were 78–100 nm. The hardness and wear resistance first increase then followed by a decrease with the increase of BN concentration. The coating contains metallic nickel, tungsten and the corresponding oxidized/hydroxide, as well as BN particles. The inclusion of BN in Ni–W alloy could refine grains, decrease porosity and enhance the shielding effect. The corrosion resistance of Ni–W/BN nanocomposite coating firstly increased and then decreased with the increase of BN. The higher concentration of BN nanoparticles has adverse effects on the properties of the coating.

MACE nano-texture process applicable for both single- and multi-crystalline diamond-wire sawn Si solar cells

The photovoltaic (PV) industry requires efficient cutting of large single and multi-crystalline (sc- and mc-) silicon (Si) wafers. Historically multi-wire slurry sawing (MWSS) dominated, but the higher productivity of diamond-wire-sawing (DWS) holds promise for decreasing PV costs in the future. While surface texturing of DWS wafers is more complicated than of MWSS wafers, especially in mc-Si wafers, nanotexturing has been shown to overcome this challenge. While the benefit of nanotexturing is thus clearer in mc-Si, a universal nano-texture process that also works on sc-Si would simplify and reduce the investments costs of PV production-lines. In this paper, such a nano-texture process is developed using a metal-assisted chemical etch (MACE) technique. Step-by-step characterization of surface structure and reflectance of the MACE process is used after: 1) wafering, 2) standard acidic texturing etch, 3) silver nanoparticles deposition, and 4) MACE nanotexturing for both sc and mc-Si. The results show that the same MACE process works effectively for both sc-Si and mc-Si wafers. Finally, the nano-textured wafers are processed into PV cells in an industrial process line with conversion efficiencies of 19.4% and 18.7%, for sc-Si and mc-Si solar cells, respectively.

Ultrafast laser printing of self-organized bimetallic nanotextures for multi-wavelength biosensing

Surface-enhanced spectroscopy (SES) techniques, including surface-enhanced photoluminescence (SEPL), Raman scattering (SERS) and infrared absorption (SEIRA), represent powerful biosensing modalities, allowing non-invasive label-free identification of various molecules and quantum emitters in the vicinity of nanotextured surfaces. Enhancement of multi-wavelength (vis-IR) excitation of analyte molecules of interest atop a single textured substrate could pave the way toward ultimate chemosensing performance and further widespread implementation of the SES-based approaches in various crucial areas, such as point-ofcare diagnostics. In this paper, an easy-to-implement ultrafast direct laser printing via partial spallation of thermally-thick silver films and subsequent large-scale magnetron deposition of nanometer-thick Au layers of variable thickness was implemented to produce bimetallic textured surfaces with the cascaded nanotopography. The produced bimetallic textures demonstrate the strong broadband plasmonic response over the entire visible spectral range. Such plasmonic performance was confirmed by convenient spectroscopy-free Red-Green-Blue (RGB) color analysis of the dark-field (DF) scattering images supported by numerical calculations of the electromagnetic (EM) “near-fields”, as well as comprehensive DF spectroscopic characterization. Bimetallic laser-printed nanotextures, which can be easily printed at ultrafast (square millimeters per second) rate, using galvanometric scanning, exhibited strong enhancement of the SEPL (up to 75-fold) and SERS (up to 106 times) yields for the organic dye molecules excited at various wavelengths. Additionally, comprehensive optical and sensing characterization of the laser-printed bimetallic surface structures allows substantiating the convenient spectroscopy-free RGB color analysis as a valuable tool for predictive assessment of the plasmonic properties of the various irregularly and quasi-periodically nanotextured surfaces.

Atomic Surface Segregation and Structural Characterization of PdPt Bimetallic Nanoparticles.

Bimetallic nanoparticles are of interest since they lead to many interesting electrical, chemical, catalytic, and optical properties. They are particularly important in the field of catalysis since they show superior catalytic properties than their monometallic counterparts. The structures of bimetallic nanoparticles depend mainly on the synthesis conditions and the miscibility of the two components. In this work, PdPt alloyed-bimetallic nanoparticles (NPs) were synthesized through the polyol method, and characterized using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). High-angle annular dark-field (HAADF)-STEM images of bimetallic nanoparticles were obtained. The contrast of images shows that nanoparticles have an alloy structure with an average size of 8.2 nm. Together with the characterization of nanoparticles, a systematic molecular dynamics simulations study focused on the structural stability and atomic surface segregation trends in 923-atom PdPt alloyed-bimetallic NPs was carried out.

Versatile and Scalable Strategy To Grow Sol-Gel Derived 2H-MoS2 Thin Films with Superior Electronic Properties: A Memristive Case.

Transition metal dichalcogenides, such as molybdenum disulfide (MoS2), show peculiar chemical/physical properties that enable their use in applications ranging from micro- and nano-optoelectronics to surface catalysis, gas and light detection, and energy harvesting/production. One main limitation to fully harness the potential of MoS2 is given by the lack of scalable and low environmental impact synthesis of MoS2 films with high uniformity, hence setting a significant challenge for industrial applications. In this work, we develop a versatile and scalable sol-gel-derived MoS2 film fabrication by spin coating deposition of an aqueous sol on different technologically relevant, flexible substrates with annealing at low temperatures (300 °C) and without the need of sulfurization and/or supply of hydrogen as compared to cutting-edge techniques. The electronic and physical properties of the MoS2 thin films were extensively investigated by means of surface spectroscopy and structural characterization techniques. Spatially homogenous nanocrystalline 2H-MoS2 thin films were obtained exhibiting high chemical purity and excellent electronic properties such as an energy band gap of 1.35 eV in agreement with the 2H phase of the MoS2, and a density of states that corresponds to the n-type character expected for high-quality 2H-MoS2. The potential use of sol-gel-grown MoS2 as the candidate material for electronic applications was tested via electrical characterization and demonstrated via the reversible switching in resistivity typical for memristors with a measured ON-OFF ratio ≥102. The obtained results highlight that the novel low-cost fabrication method has a great potential to promote the use of high-quality MoS2 in technological and industrial-relevant scalable applications.