Bright-field Transmission Electron Microscopy Research Articles

Assessment of Novel MgCe4P6O24 Ceramic Electrolyte in Fabricating Mg-Sensors: Focus on Structure and Electrochemical Impedance Spectroscopy

In this study, a high-temperature ceria-based phosphate ceramic electrolyte, MgCe4P6O24 prepared using a modified sol-gel chemical method produced pure dried xerogel powders is presented [1-3]. The dried xerogel powders were then calcined at 900 oC to produce MgCe4P6O24 single phase nanopowders using data extracted from thermal analysis (TGA-DSC) on the dried xerogel powders. The nanopowders were further pelletised and sintered at 1300 oC to produce a single phase dense pellets preparatory for electrochemical impedance spectroscopy analysis. X-ray diffraction (XRD) reveals that the calcined nanopowders possess an excellent crystalline structure with an average crystallite size of 52 ± 1 nm, and having a monoclinic phase, which invariably was confirmed using the High Resolution TEM (HRTEM), as presented in Figure 1. In using electrochemical impedance spectroscopy [1-3], ionic conductivity of MgCe4P6O24 ceramic electrolyte = 2.14 x 10-3 Scm-1 at an impedance bulk temperature of 744 oC was achieved. In adapting the electrochemical method [2,3], thermodynamic and kinetic data computed in this study shows the transport number of Mg2+-cation = 0.85 ± 0.03 at 700 ± 5 oC. The structural orientation, transport number and ionic conductivity data of MgCe4P6O24 ceramic electrolyte suggests the ionic conductor as a suitable solid-state ceramic electrolyte for fabricating high-temperature Mg-sensors. Figure 1(a):Bright-field TEM image showing SAED with crystalline particles (insert), and (b) HRTEM micrograph showing corresponding SAED patterns for MgCe4P6O24 nanoparticles detailing d-spacing from lattice fringes of the HRTEM patterns in b(iii).

Major Factors Influencing the Size Distribution Analysis of Cellulose Nanocrystals Imaged in Transmission Electron Microscopy.

Size distributions of cellulose nanocrystals (CNCs), extracted from softwood pulp via strong sulfuric acid hydrolysis, exhibit large variability when analyzed from transmission electron microscopy (TEM) images. In this article, the causes of this variability are studied and discussed. In order to obtain results comparable with those reported, a reference material of CNCs (CNCD-1) was used to evaluate size distribution. CNC TEM specimens were prepared as-stained and dried with a rapid-flushing staining method or hydrated and embedded in vitreous ice with the plunge-freezing method. Several sets of bright-field TEM (BF-TEM), annular dark-field scanning TEM (ADF-STEM) and cryogenic-TEM (cryo-TEM) images were acquired for size distribution analysis to study the contributing factors. The rapid-flushing staining method was found to be the most effective for contrast enhancement of CNCs, not only revealing the helical structure of single CNCs but also resolving the laterally jointed CNCs. During TEM specimen preparation, CNCs were fractionated on TEM grids driven by the coffee-ring effect, as observed from contrast variation of CNCs with a stain-depth gradient. From the edge to the center of the TEM grids, the width of CNCs increases, while the aspect ratio (length to width) decreases. This fractionated dispersion of CNCs suggests that images taken near the center of a droplet would give a larger mean width. In addition to particle fractionation driven by the coffee-ring effect, the arrangement and orientation of CNC particles on the substrate significantly affect the size measurement when CNC aggregation cannot be resolved in images. The coexistence of asymmetric cross-section CNC particles introduces a large variation in size measurement, as TEM images of CNCs are mixed projections of the width and height of particles. As a demonstration of how this contributes to inflated size measurement, twisted CNC particles, rectangular cross-section particles and end-to-end jointed CNCs were revealed in reconstructed three-dimensional (3D) micrographs by electron tomography (ET).

The possible role of nano sized precipitates on the mechanical properties of additively manufactured IN 718 superalloy

In the present study, three dimensional parts of Inconel 718® (IN 718) superalloy were fabricated using laser powder bed fusion (L-PBF) additive manufacturing (AM). The soundness of the as-built parts was checked by measuring the relative density using Archimedes method. Tensile tests were carried out at the strain rate of 4.6 × 10-3 s-1 at ambient temperature on cylindrical samples extracted from the large size 3D blocks of AM IN 718. Tensile tests were also carried out employing the same test parameters on the wrought counterpart of IN 718 (W IN 718) so as to compare their mechanical properties. The AM IN 718 exhibited about 15% increase in 0.2% yield strength (0.2%YS) as compared to W IN 718. Microstructures of AM IN 718 and W IN 718 were characterized using electron back scattered diffraction. The dislocation substructure of pre-deformed samples was examined using transmission electron microscope (TEM). Bright field TEM images revealed nano-sized precipitates in AM IN 718 and carbides in W IN 718. The marginal increase in 0.2%YS in AM IN 718 is attributed to the impediment to dislocation movements by nano-sized precipitates and high initial dislocation density.

Structure and Bottom-up Formation Mechanism of Multisheet Silica-Based Nanoparticles Formed in an Epoxy Matrix through an In Situ Process.

Organic/inorganic hybrid composite materials with the dispersed phases in sizes down to a few tens of nanometers raised very great interest. In this paper, it is shown that silica/epoxy nanocomposites with a silica content of 6 wt % may be obtained with an “in situ” sol–gel procedure starting from two precursors: tetraethyl orthosilicate (TEOS) and 3-aminopropyl-triethoxysilane (APTES). APTES also played the role of a coupling agent. The use of advanced techniques (bright-field high-resolution transmission electron microscopy, HRTEM, and combined small- and wide-angle X-ray scattering (SAXS/WAXS) performed by means of a multirange device Ganesha 300 XL+) allowed us to evidence a multisheet structure of the nanoparticles instead of the gel one typically obtained through a sol–gel route. A mechanism combining in a new manner well-assessed knowledge regarding sol–gel chemistry, emulsion formation, and Ostwald ripening allowed us to give an explanation for the formation of the observed lamellar nanoparticles.

Microwave-assisted synthesis of nanoscale VO2 structures

Nanoscaled VO2 structures were made using a fast microwave-assisted synthesis method in acetophenone as solvent, starting from vanadium pentoxide V2O5. Insights in the reaction and purification process were elaborated by attenuated total reflection infrared and nuclear magnetic resonance spectroscopy, which validated the choice of oleyl amine as ligand and acetophenone as solvent. A straightforward heat treatment in inert atmosphere was used to convert the mixture of VOx (M) and VOOH phases to thermochromically active monoclinic VO2 (M) nanomaterials. This conversion process was monitored via in-situ X-ray diffraction and gave insight in the influence of ethanol and tert-butyl hydroperoxide on the crystal structure and morphology, monitored via bright-field transmission electron microscopy. The thermochromic switching was investigated with differential scanning calorimetry showing a latent heat up to 43.34 ​J/g.

Optimization of ion-beam-deposited Mo/Si multilayers for extreme ultraviolet masks

The aim of our work is to investigate deposition conditions to further optimize the reflectivity of Mo/Si multilayers (MLs) for reflective coatings of extreme ultraviolet mask blanks. Dark-field transmission electron microscopy (TEM) measurements imply interfacial roughness values of 80 to 150 pm. Bright-field TEM images indicate intermixed layer thicknesses of 0.4 to 1.8 nm. We present reflectivity calculations including these two ML imperfections and compare against prior empirical results. Both interfacial roughness and intermixing are predicted to lower the maximum reflectivity. For example, interfacial roughness of 400 pm lowers the maximum reflectivity by ∼2 % . Smoother interfaces with sub-100 pm allow recovery of ∼1.5 % of the reflectivity. Mo/Si intermixing is predicted to lower the maximum reflectivity by up to 6% relative to an ideal ML. Reflectivity could be recovered by ∼3 % by reducing the intermixing depth by only 20% to 30%. We demonstrate ways to reduce roughness or intermixing by ion beam deposition (IBD). Ion bombardment simulations provide estimates of the atom energy distribution arriving at the mask blank surface during Mo and Si deposition and of stopping depths of each atom into the underlying layer. Key IBD parameters to reduce the deposition energy, and hence the intermixing depth, are summarized: beam voltage and deposition pressure. Lower ion beam voltage or higher pressure can together reduce the intermixing depth by at least 20% to 30%. Bright-field TEM measurements of MLs deposited at various deposition conditions confirm the intermixing predictions.

Propagation of threading dislocations and effects of Burgers vectors in HVPE-grown GaN bulk crystals on Na-flux-grown GaN substrates

The propagation behavior of threading dislocations (TDs) and the effects of Burgers vectors in hydride vapor phase epitaxy (HVPE) GaN bulk crystals generated on Na-flux-grown GaN and in a commercially available HVPE-grown GaN bulk crystal were investigated. Analyses based on chemical etching and transmission electron microscopy (TEM) revealed a close correlation between the etch pit sizes and the Burgers vector of these TDs. The existence of TDs with the unique Burgers vector b = 1m + 1c was observed for the first time ever using a large-angle convergent-beam electron diffraction technique and plan-view bright-field scanning TEM. Multi-photon excitation photoluminescence microscopy observations showed that TDs with b = 1c had a meandering morphology in contrast to the linear morphology of TDs with b = 1a, 1a + 1c, or 1m + 1c in both types of HVPE-grown GaN crystals. The inclinations of TDs with b = 1a and 1a + 1c in HVPE-grown GaN on Na-flux-grown GaN were greatly affected by large symmetrical hexagonal hillocks. The TDs with b = 1a were inclined in the slope directions of the hillock planes, while those with b = 1a + 1c were inclined in the a directions parallel or antiparallel to the a component in their Burgers vector. These inclinations were readily explained by the isotropic elastic theory of an individual TD. The hillocks were produced around pairs of parallel mixed TDs for which the a components were opposite to one another. This phenomenon was attributed to inclusions at the interface between the Na-flux-grown GaN substrate and the HVPE-grown layer. The origins of other TDs including unusual ones having b = 1m + 1c are also discussed herein.

Significant Improvement of Strength in Wrought 945A Ni-Based Superalloy by Aging Treatment

Ni-based superalloys have attracted much attention due to their good resistance to high-temperature and -pressure environments. Compared with the traditional 718 Ni-based superalloy, 945A Ni-based superalloy with a lower Ni content showed better performance in terms of precipitated hardening and corrosion resistance. In this study, the aging behavior and the evolution of mechanical properties of the wrought 945A Ni-based superalloy were investigated. Microstructures were analyzed by scanning electron microscopy (SEM), bright field transmission electron microscopy (TEM), high-resolution TEM and high-angle annular dark field scanning TEM. Mechanical properties were measured by tensile and compressive tests. The results illustrated that the compressive yield stress was significantly improved by increasing aging time from 229 to 809 MPa. The increase was greater than 220%. This improvement was mainly attributed to the precipitates of the γ′ phase and carbides during the aging treatment. The residual dislocations generated by the plastic processes stimulated the formation of these precipitates. The precipitation behavior and the strengthening mechanism are discussed in detail.

In Situ tem Cycling of Semi-Solid State Micro-Battery in Liquid Electrolyte

All solid state Li-ion micro-battery is a promising candidate to power miniaturized sensors for Internet of things (IOT) and other electronic devices. In recent times, the spinel LiMn1.5Ni0.5O4 (LNMO) has demonstrated as a potential positive electrode material for Li-ion thin film batteries offering a theoretical capacity of 147 mAh/g (65 µAh/cm2/µm for a bulk density of 4.47 g/cm3) and operates up to now at the highest potential (around 4.7 V vs. Li+/Li) [1]. In this work, we report our first successful in situ TEM attempts to observe the morphological, structural and interfacial changes in the positive electrode layer of FIB prepared sample which undergo after cycling using liquid electrolyte. More precisely we compared the morphological and structural evolution between a pristine and cycled microbattery by 4D STEM-ASTAR technique to highlight the key information to improve the deposition conditions that will enhance the reliability and production quality of such micro power devices. The in situ cycling in liquid TEM has given this opportunity to study the battery electrode materials so as to spot the slightest modifications of the materials resulting in important advances in knowledge on electrochemical energy storage [2-3].Here, our approach is based on the cycling a FIB lamella sample inside the TEM using liquid-electrochemical TEM holder with conventional liquid electrolyte (1M LiClO4, EC: DMC 1:1). The cross-section image of as prepared FIB sample with homogeneous deposition of distinctive layers of different thickness [from bottom to top-Si (0.385mm)/ Al2O3 (100nm)/ Pt (630nm) / LNMO (400nm)] is shown in figure 1a. The Pt current collector of FIB lamella sample is connected to the Pt working electrode on the e-chips used for TEM study (figure 1b). First, using FIB preparation technique, we sliced a full 2-D “thin film micro-battery” making it as thin to observe/analyse under TEM. Then, we modified the FIB lamellar design using FIB-SEM tool to get good electrical contact and reduced polarisation. Several technological problems have to be overcome in the process. For the instance, it is mandatory to obtain a good electrical contact between the Pt working electrode of e-chip and Pt current collector of FIB lamellar, which is later achieved by depositing extra Pt between the two contacts forming a platinum bridge. A 4-Probe electrical conductivity performed locally confirms the good electrical contact between the as prepared FIB lamella sample and Pt working electrode of e-chip. The cross-section bright field TEM image of a final modified version of FIB lamella sample used in the study is shown in figure 1d.The FIB lamella sample is then later cycled inside the liquid electrochemical TEM holder (fig 1c) in potential window of 4.1 V-4.8 V vs. Li+/Li. The flow of the electrolyte (LiClO4 EC:DMC 1:1) inside the TEM holder was further controlled by microfluidic controller with the flow rate of 2 µL/min. CV was recorded at a sweep rate of 0.1mV/s and two plateaus at 4.4 V and 4.6 V was observed corresponding to Ni2+/3+ and Ni3+/4+ oxidation respectively (Fig 1f). The basic redox steps observed during the charge are same as observed in the case of cycling bulk 2D thin film in a homemade flat cell.The comparison between the cycled and pristine microbattery sliced by FIB and observed by TEM allowed us to clearly demonstrate the formation of cracks inside the LMNO layer, loss of contact between the LMNO layer and the platinum current collector, as well as the agglomeration of the organic compounds produced due to the electrolyte decomposition. Moreover, 4D STEM-ASTAR technique provided us with the crucial information regarding the grain size reduction from 20 nm in pristine to 12 nm in cycled sample, confirming the continuous electrode-electrolyte reaction happening over the cycling. Also, the decrease in crystallinity and increase in the amorphization of the LMNO grains by 38 % in the cycled sample compared to pristine as shown in figure 1e and g clearly prove the fast capacity fading phenomenon observed in bulk microbattery. Furthermore, a thickness of ~20nm along the platinum layer, a (111) preferred orientation is observed exhibiting the epitaxial effect of LMNO on platinum layer which has been further supported by the precision electron diffraction (PED) recorded on both LMNO and platinum grains.

(Invited) Solution-Processed Reorganization of Semiconductor Nanocrystals in Thin Films

Colloidal nanocrystals (NCs) have been attracted because of their strongly size-dependent luminous characteristics and solution processability. As prepared colloidal NCs covered with some bulky and long-chain organic ligands such as oleic acid, oleylamine (OAm), trioctylphosphine oxide, and so on are mostly dispersed in some solvents such as hexane, toluene, and so on. After preparation of thin films from the dispersed solutions of NCs, reduced inter NC distance (viz. NCs coming closer) with highly ordered alignment will lead to enhanced electronic coupling between adjacent NCs resulting in better wave function overlap and charge transport of the conducting solid materials.In this context, remarkable improvement of the alignment of the particles through solution-processed reorganization of AgInS2 quantum dots (QDs) covered with OAm by cast method was confirmed by bright-field TEM observation [1,2]. The interplanar spacing of the QDs was 0.33 nm, which corresponds to (112) crystal planes of the tetragonal phase of AgInS2.On the other hand, it was found that PbS colloidal QDs can be packed densely and infiltrated efficiently into the interrod space of vertically aligned ZnO nanowire arrays through convective deposition method, which is one of the meniscus coating techniques [3] as compared with spin-coating process, which brings many cracks and voids in the obtained thin films. As a result, a record power conversion efficiency of 9.92% has been demonstrated for ordered bulk heterojunction structured solar cells that are compatible with low-temperature and scalable manufacturing processes.While comparisons of perovskite CsPbBr3 NCs grafted on the surface of silica nanohelices as templates in dispersed state in toluene and dried state on quartz glass substrate revealed that the interparticle distance becomes shorter after the dryness by cast method from the dispersed state and the closely and helically packed NCs [4]. Tuning the conditions of solution-processed reorganization of CsPbBr3 NCs is crucial for reducing the inter NC distance with highly ordered alignment in the cast films with large circular dichroism and circularly polarized luminescence signals.On the basis of the above findings, reorganization of NCs with highly controlled crystal orientation and inter NC distance in thin films has deep influence on specific spectral characteristics and photovoltaic performances.[1] Kaewprajak, A.; Kumnorkaew, P.; Sagawa, T. Silver-indium-sulfide quantum dots in titanium dioxide as electron transport layer for highly efficient and stable perovskite solar cells. J. Mater. Sci.: Mater. Electron., 2019, 30, 4041-4055.[2] Kaewprajak, A.; Kumnorkaew, P.; Sagawa, T. Improved photovoltaic performance and device stability of planar heterojunction perovskite solar cells using TiO2 and TiO2 mixed with AgInS2 quantum dots as dual electron transport layers. Org. Electron., 2019, 69, 26-33.[3] Shi, G.; Kaewprajak, A.; Ling, X.; Hayakawa, A.; Zhou, S.; Song, B.; Kang, Y.-w.; Hayashi, T.; Altun, M. E.; Nakaya, M.; Liu, Z.; Wang, H.; Sagawa, T.; Ma, W. Finely interpenetrating bulk heterojunction structure for lead sulfide colloidal quantum dot solar cells by convective deposition. ACS Energy Lett., 2019, 4, 960-967.[4] Liu, P.; Chen, W.; Okazaki, Y.; Battie, Y.; Brocard, L.; Decossas, M.; Pouget, E.; M.-Buschbaum, P.; Kauffmann, B.; Pathan, S.; Sagawa, T.; Oda, R. Optically active perovskite CsPbBr3 nanocrystals helically arranged on inorganic silica nanohelices. Nano Lett., 2020, 20, 8453-8460.

Synthesis of C:Se nanoparticles via laser ablated with magnetic field on porous silicon for gas sensor applications

The presented study synthesized C:Se NPs via a combination of the laser along with magnetic field at various laser pulse energies 200, 600 and 1000mJ with 100 shots, have been deposited on the porous silicon (PS) through the use of drop-casting method. The pattern of the X-ray diffraction (XRD) had indicated the nanocrystaline of specimens. In Atomic force microscopy (AFM), which shows agglomeration of C:Se NPs increased, the distribution of the granularity showed that the distribution of part was almost Gaussian, also the transmission electron microscope (TEM) indicated that the synthesized C:Se particles have an average particle size of 35 nm. Bright-field TEM images show complementary contrast, confirming the formation of core/shell structures. The optical measurements in wavelength range ultraviolet-visible near infrared (UV–vis–NIR) as well as a transition of indirect type with 4 eV band gap is specified. Also, the electrical characteristics like barrier height (ΦB), ideal factor (n) for Al/C:Se NPs/PS/Si/Al heterojunction were concluded with measurements of current-voltage (I-V). Lastly, the operation temperature variations associated with NO2 and NH3 gas sensors are subjected to fabrication from the prepared samples on response time, sensor sensitivity and recover time was examined. The maximum sensitivity of C:Se/PS at 1000 mJ gas sensor to 60 ppm of NO2 about 202.5% at around 100 °C,also the maximum sensitivity of C:Se/PS at 1000mJgas sensor to 200 ppm of NH3 can reach 17.9%, and the optimum sensing temperature of C: Se/PS sensor is at around 150 °C.

Cholecalciferol Mediates Apoptosis in Siha Cervical Cancer Line via Autocrine Mechanisms

Cervical cancer disproportionately affects low-resource countries and is a significant health burden in South Africa. Pre-clinical studies have demonstrated numerous anti-cancer actions of vitamin D metabolites. Here, the anti-cancer action of the vitamin D precursor, cholecalciferol, was investigated in a high-grade cervical cancer cell line, SiHa. SiHa cell cultures were treated with a range of cholecalciferol doses (26 nM, 104 nM, 260 nM and 2600 nM) for 72 hours. Cell count and viability were assessed by crystal violet and trypan blue assays, respectively. Apoptotic cell death was investigated by flow cytometry, which measured mitochondrial membrane potential (∆Ψm), phosphatidylserine (PS) externalisation, effector caspase activation and the expression of DNA damage markers. Additionally, brightfield microscopy and transmission electron microscopy (TEM) were respectively used to characterise morphological and ultrastructural features of apoptosis. Expression of the vitamin D metabolising system (VDMS) – consisting of cholecalciferol activating (CYP2R1 and CYP27A1), calcidiol activating (CYP27B1) and calcidiol inactivating (CYP24A1) enzymes, and the vitamin D receptor (VDR) – was assessed by qPCR and Western blots. Data were analysed using a one-way ANOVA and Bonferroni post-hoc tests and p < 0.05 was considered statistically significant. Significant decreases in cell count (p = 0.011) and cell viability (p < 0.0001) were identified in SiHa cells treated with 2600 nM cholecalciferol. Furthermore, biochemical markers at 2600 nM treatment were significant for apoptosis, and included decreased ∆Ψm (p = 0.0145); increased PS externalisation (p = 0.0439); terminal caspase activation (p = 0.0025); and nuclear damage (p = 0.004). Moreover, biochemical apoptosis was corroborated by classical apoptotic features observed by brightfield microscopy and TEM. Additionally, a significant increase in CYP2R1 gene (p < 0.0001) and protein (p = 0.021) expression, and a converse significant decrease in CYP27B1 gene (p = 0.003) and protein expression (p = 0.031) were observed at 2600 nM cholecalciferol treatment. Furthermore, significant increases in VDR gene (p = 0.033) and protein (p = 0.04) expression, and CYP24A1 gene (p < 0.0001) and protein (p = 0.0274) expression were observed at 2600 nM cholecalciferol. In summary, high-dose cholecalciferol treatment of SiHa cervical cancer cells inhibits cell growth, induces apoptosis, and furthermore, upregulates CYP2R1 and VDR expression. Taken together, these findings suggest that autocrine activation of cholecalciferol to calcidiol may mediate VDR signalling of cell growth inhibition, and apoptosis in SiHa experimental cultures.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

AutoDetect-mNP: An Unsupervised Machine Learning Algorithm for Automated Analysis of Transmission Electron Microscope Images of Metal Nanoparticles.

The synthesis quality of artificial inorganic nanocrystals is most often assessed by transmission electron microscopy (TEM) for which high-throughput advances have dramatically increased both the quantity and information richness of metal nanoparticle (mNP) characterization. Existing automated data analysis algorithms of TEM mNP images generally adopt a supervised approach, requiring a significant effort in human preparation of labeled data that reduces objectivity, efficiency, and generalizability. We have developed an unsupervised algorithm AutoDetect-mNP for automated analysis of TEM images that objectively extracts morphological information on convex mNPs from TEM images based on their shape attributes, requiring little to no human input in the process. The performance of AutoDetect-mNP is tested on two data sets of bright field TEM images of Au nanoparticles with different shapes and further extended to palladium nanocubes and cadmium selenide quantum dots, demonstrating that the algorithm is quantitatively reliable and can thus serve as a generalizable measure of the morphology distributions of any mNP synthesis. The AutoDetect-mNP algorithm will aid in future developments of high-throughput characterization of mNPs and the future advent of time-resolved TEM studies that can investigate reaction mechanisms of mNP synthesis and reactivity.

Robust Ruthenium Catalysts Supported on Mesoporous Cyclodextrin-Templated TiO2-SiO2 Mixed Oxides for the Hydrogenation of Levulinic Acid to γ-Valerolactone.

In this paper, we present a versatile template-directed colloidal self-assembly method for the fabrication in aqueous phase of composition-tuned mesoporous RuO2@TiO2-SiO2 catalysts. Randomly methylated β-cyclodextrin/Pluronic F127 supramolecular assemblies were used as soft templates, TiO2 colloids as building blocks, and tetraethyl orthosilicate as a silica source. Catalysts were characterized at different stages of their synthesis using dynamic light scattering, N2-adsorption analysis, powder X-ray diffraction, temperature programmed reduction, high-resolution transmission electron microscopy, high-angle annular bright-field and dark-field scanning transmission electron microscopy, together with EDS elemental mapping. Results revealed that both the supramolecular template and the silica loading had a strong impact on the pore characteristics and crystalline structure of the mixed oxides, as well as on the morphology of the RuO2 nanocrystals. Their catalytic performance was then evaluated in the aqueous phase hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) under mild conditions (50 °C, 50 bar H2). Results showed that the cyclodextrin-derived catalyst displayed almost quantitative LA conversion and 99% GVL yield in less than one hour. Moreover, this catalyst could be reused at least five times without loss of activity. This work offers an effective approach to the utilization of cyclodextrins for engineering the surface morphology of Ru nanocrystals and pore characteristics of TiO2-based materials for catalytic applications in hydrogenation reactions.

Mechanical Reshaping of Inorganic Nanostructures with Weak Nanoscale Forces.

Inorganic nanomaterials are often depicted as rigid structures whose shape is permanent. However, forces that are ordinarily considered weak can exert sufficient stress at the nanoscale to drive mechanical deformation. Here, we leverage van der Waals (VdW) interactions to mechanically reshape inorganic nanostructures from planar to curvilinear. Modified plate deformation theory shows that high-aspect-ratio two-dimensional particles can be plastically deformed via VdW forces. Informed by this finding, silver nanoplates were deformed over spherical iron oxide template particles, resulting in distinctive bend contour patterns in bright-field (BF) transmission electron microscopy (TEM) images. High-resolution TEM images of deformed areas reveal the presence of highly strained bonds in the material. Finally, we show that the distance between two nearby template particles allows for the engineering of several distinct curvilinear morphologies. This work challenges the traditional view of nanoparticles as static objects and introduces methods for postsynthetic mechanical shape control.

Thermal gas-phase etching of titanium nitride (TiN) by thionyl chloride (SOCl2)

In this work, thermal based gas-phase etching of titanium nitride (TiN) is demonstrated using thionyl chloride (SOCl2) as a novel etchant. A single etchant is utilised in a pulsed fashion to etch TiN. This type of etching technique may also be considered as a chemical gas-phase or dry etching. The removed TiN amount was measured by various techniques like spectroscopic ellipsometry (SE), weighing balance and in some cases X-ray reflectometry (XRR). Additionally, the post-etch surfaces were analysed with X-ray photoelectron spectroscopy (XPS) and bright field transmission electron microscopy (BF-TEM). The surface roughness and morphology of before and after etching TiN films were measured using atomic force microscopy (AFM). The etch per cycle (EPC) was calculated and is plotted as a function of SOCl2 pulse time, purge time after SOCl2 exposure, number of etch cycles and etch temperature (Tetch). An increase in EPC with an increase in SOCl2 pulse time as well as etch temperature was observed. SOCl2 is able to etch TiN starting from 270 °C with an EPC of about 0.03 Å to almost 1.2 Å at 370 °C. Arrhenius plot determined the activation energy (Ea) of about 25 kcal/mol for TiN etching by SOCl2. In addition, the etch selectivity between different substrates such as silicon dioxide (SiO2), silicon nitride (Si3N4) and aluminum oxide (Al2O3) was investigated on blanket as well as 3D structures. Moreover, thermodynamic calculations were performed for various possible etch reactions. Titanium from TiN is proposed to be etched in the form of either titanium trichloride (TiCl3) or titanium tetrachloride (TiCl4). Nitrogen from TiN films may form volatile by-products such as diatomic nitrogen (N2), nitrous oxide (N2O) and nitrogen dioxide (NO2).

Second Life Application of Automotive Catalysts: Hydrodynamic Cavitation Recovery and Photo Water Splitting

A hydrodynamic cavitation method was used to maximize the effect of destructuration of a honeycomb monolithic support of a spent Selective Catalyst Reduction (SCR) catalyst—V2O5-WO3/TiO2-type—for extracting crystalline titanium and tungsten oxides from the cordierite surface. A high relative inlet pressure of 40 MPa was applied to a divergent nozzle for obtaining high shear stresses of the submerged cavitating jets and intensive micro- and nano-jets and shock waves acting on the particle surface of the milled catalyst. Scanning Electron Microscopy (SEM) analysis indicated the compact morphology of the thin metal oxide layer at the surface of the cordierite support and the high content of Ti and W elements in the sample. Energy dispersive spectroscopy (EDAX) performed along with TEM investigations on different nano-zones from the sample established the elemental composition of WO3-TiO2 agglomerates separated after hydrodynamic cavitation processing and identified as independent nanocrystalline structures through Bright Field Transmission Electron Microscopy (BF-TEM) and High Resolution Transmission Electron Microscopy (HR-TEM) measurements. The tetragonal anatase phase of TiO2 and cubic phase of WO3 were established by both interplanar d spacing measurements and X-ray diffraction analysis. The photoelectrochemical results showed the possible second life application of automotive catalysts.

Constituent Isomerism-Induced Quasicrystal and Frank–Kasper σ Superlattices Based on Nanosized Shape Amphiphiles

Naturally, subtle variations in the chemical structures of constituent molecules may significantly affect their multiscale spatial arrangements, properties, and functions. Deceptively simple spheri...

Synthesis and characterizations of Pd/Mn(Mn1.36Pd0.64)O4 nanocomposite: An experimental and theoretical approach

Due to the growing environmental issues and high energy consumption, there is an emergent need to synthesize the multifunctional materials to reduce energy consumption. Hence, we synthesized the Pd/Mn(Mn1·36Pd0.64)O4 nanocomposite by a simple sol-gel process, and studied their Crystal structure, surface morphology, optical absorbance, electrochemical and magnetic properties. Phase analysis, crystalline structures and crystallite sizes of the nanocomposite were revealed using the X-ray diffraction. Nanosize, globular shape morphologies were revealed using SEM and TEM bright field images. The optical energy band-gap from the optical absorbance spectra was estimated to be 2.22 eV. The electrochemical properties of the composite were observed by cyclic voltammetry studies. The symmetric behavior of the voltammetry plots indicates that the nanocomposite is a favorable candidate used for the fast redox reactions with higher specific capacitance. The vibrating sample magnetometer studies confirm the paramagnetic behavior at room temperature. Electronic structures of the composite reveal the half-metallicity and magnetic behavior of Pd/Mn(Mn1·36Pd0.64)O4 structure.