The application of low energy ion scattering spectroscopy (LEIS) in sub 28‐nm CMOS technology

With the transition to ≤28‐nm CMOS technology nodes, the surface analytical challenges with regard to steadily decreasing dimensions and still growing materials options raise the demand of high performing surface analysis techniques. Characterization of ultrathin films and multilayer stacks, especially in high‐k metal gate stacks, by means of low energy ion scattering spectroscopy (LEIS) with its monolayer sensitivity has been established as a very useful analysis technique next to Auger electron spectroscopy, X‐ray photoelectron spectroscopy , and time‐of‐flight secondary ion mass spectrometry. Questions regarding film nucleation, growth, coverage, and diffusion can be answered, thereby enabling those processes to be controlled appropriately. In this work, growth studies of ALD HfO₂ and TiN are shown, as well as film thickness determination based on surface spectra. PVD aluminum and lanthanum, acting as work function metals on the gate oxide, were deposited, and their film formation and closure were investigated. Further application fields of LEIS have emerged from the characterization of in‐die features on patterned wafers. As presented on test arrays, it is possible to detect material deep in trenches. This is an advantage if residues need to be identified after etch or clean processes.     

Recent advances on electrospun scaffolds as matrices for tissue-engineered heart valves

Valvular heart diseases (VHDs) are a major health problem increasing morbidity and mortality worldwide. Currently, treatment of VHDs relies on valve replacement with mechanical or biological valves, which have major drawbacks in terms of durability and the ability to grow, repair and remodel. To this end, tissue-engineered heart valves (TEHVs) have emerged as ideal substitutes. TEHVs are composed of biodegradable, biocompatible and mechanically stable scaffolds that resemble the native valves. These scaffolds are seeded with autologous cells and conditioned in a bioreactor prior to implantation. Scaffolds that have been utilized so far for such application are (i) biological, (ii) synthetic and (iii) cell entrapment in polymerized extra-cellular matrix based scaffolds. Synthetic scaffolds are considered superior over the other two types in terms of controlled mechanical properties and degradation rate. They can be subdivided into porous, hydrogel and fibrous scaffolds. Among the three subcategories, fibrous scaffolds are preferred because they resemble the natural extra-cellular matrix for the native valve. Such scaffolds can be fabricated using phase separation, self-assembly and electrospinning. Electrospinning is a versatile technique for fabricating scaffolds for tissue engineering applications that possess many advantages. Electrospun scaffolds processed using a wide range of synthetic and natural polymers were proven to be promising in terms of mechanical properties comparable to the native valves, fiber diameter within the range of the natural extracellular matrix and good cellular response. However, further investigation in fabricating fibrous scaffolds for tissue-engineered heart valves is still needed. In this review, we discussed electrospun scaffolds as TEHVs matrices, how far they succeeded in meeting the criteria of ideal scaffolds for such application and what the shortage aspects and possible solutions are.     

Quantification of BTEX in Soil by Headspace SPME–GC–MS Using Combined Standard Addition and Internal Standard Calibration

There is a great demand for simple, fast and accurate methods for quantification of volatile organic contaminants in soil samples. Solid-phase microextraction (SPME) has a huge potential for this purpose, but its application is limited by insufficient accuracy caused by a matrix effect. The aim of this research was to develop the method for BTEX quantification in soil using combined standard addition (SA) and internal standard (IS) calibration. Deuterated benzene (benzene-d6) was used as the internal standard for all analytes. The optimized method includes spiking replicate samples with different concentrations of BTEX standards and the same concentration of benzene-d6, equilibration of soil samples at 40 °C during 2 h, and SPME–GC–MS analysis. Precision and accuracy of IS and SA methods were compared on different soil matrices. Combined SA + IS method provided more precise calibration plots compared to the conventional SA calibration. The SA + IS calibration provided more precise and accurate results compared with a reference method based on solvent extraction followed by GC–MS when applied to BTEX quantification in real soil samples (spiked with diesel fuel and aged). Recoveries of BTEX from soil samples spiked with known concentrations of analytes using the developed method were in the range of 73–130% with RSD values less than 15% for all BTEX. The proposed simultaneous standard addition and internal standard approach can be advantageous and adopted for improved quantification of other toxic VOCs in soil.     

Synthesis and crystal structures of three novel coordination polymers constructed from Ag(I) thiocyanate and nitrogen donor ligands

Three supramolecular coordination polymers (SCPs) [(AgSCN)₂L] {L = 4,4′-bipyridine (bpy) (1), trans-1,2-bis(4-pyridyl)ethylene (tbpe) (2) and phenazine (phenz) (3)} have been synthesized and structurally characterized by single-crystal X-ray diffraction. Synthesis was affected in H₂O/acetonitrile/NH₃ media at room temperature. The bpy, tbpe and phenz bipodal ligands adopt different conformations which would affect the skeleton of the (AgSCN)_n building blocks that allow the interconnection of the (AgSCN)_n fragments and propagation of the network structure in three dimensions. Supramolecular interactions such as hydrogen-bonding, argentophilic interaction and π–π stacking play an important role in the assembly of these coordination polymers.     

Synthesis and Evaluation of Novel Cholestanoheterocyclic Steroids as Anticancer Agents

Applied Biochemistry and Biotechnology - Modification of steroid molecules by introducing heterocyclic ring into the core structure of steroids has been utilized as an attractive approach for...     

Lithium insertion into titanium dioxide (anatase) electrodes: microstructure and electrolyte effects

Insertion characteristics of anatase electrodes were studied on single-crystal and polycrystalline electrodes of different microstructures. The lithium incorporation from propylene carbonate solution containing LiClO₄ and Li(CF₃SO₂)₂N was studied by means of cyclic voltammetry (CV), the quartz crystal microbalance (QCM) and the galvanostatic intermittent titration technique (GITT). The electrode microstructure affects both the accessible coefficient x and the reversibility of the process. The highest insertion activity was observed for electrodes composed of crystals with characteristic dimensions of ∼10^–8 m. The insertion properties deteriorate for higher as well as for smaller crystal sizes. Enhanced insertion was observed in Li(CF₃SO₂)₂N-containing solutions. Lithium insertion is satisfactorily reversible for mesoscopic electrodes; the reversibility in the case of compact polycrystalline and single-crystal electrodes is poor. The reversibility of the insertion improves with increasing electrolyte concentration. The lithium diffusion coefficient decreases with increasing x and ranges between 10^–15 and 10^–18 cm² s^–1. Electronic Publication     

Alkylation of Phenols by Caryophyllene on Acid Aluminosilicate Catalysts

The reactions of the natural sesquiterpene caryophyllene with phenols on various solid acid catalysts gave the corresponding terpenylphenols and phenyl terpenyl ethers with essentially caryolane structures. The selectivity of the process and yield of product can be raised by varying the catalyst and solvent.