Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates

Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.     

Exploiting Synergistic Effects in Organozinc Chemistry for Direct Stereoselective C‐Glycosylation Reactions at Room Temperature

Pairing a range of bis(aryl) zinc reagents ZnAr₂ with the stronger Lewis acidic [(ZnAr^F₂)] (Ar^F=C₆F₅), enables highly stereoselective cross‐coupling between glycosyl bromides and ZnAr₂ without the use of a transition metal. Reactions occur at room temperature with excellent levels of stereoselectivity, where ZnAr^F₂ acts as a non‐coupling partner although its presence is crucial for the execution of the C(sp²)–C(sp³) bond formation process. Mechanistic studies have uncovered a unique synergistic partnership between the two zinc reagents, which circumvents the need for transition‐metal catalysis or forcing reaction conditions. Key to the success of the coupling is the avoidance of solvents that act as Lewis bases versus diarylzinc compounds (e.g. THF).     

Nanometric thin films of non-doped diamond-like carbon grown on n-type (P-doped) silicon substrates as electrochemical electrodes

Journal of Solid State Electrochemistry - The electrochemical response of thin non-doped diamond-like carbon films grown by pulsed laser deposition onto n-type (P-doped) silicon substrates was...     

Different sites of insertion in the reaction of isocyanates with [Re(N(R)Ar)(CO)3(bipy)] (R = H or Me): N-H vs. Re-N

The reactions of isocyanates with [Re(N(R)Ar)(CO)3(bipy)] complexes lead to R'NCO insertion into the Re-N bond (for R = Me) or the N-H bond (R = H).     

Structural and Mechanistic Insights into s‐Block Bimetallic Catalysis: Sodium Magnesiate‐Catalyzed Guanylation of Amines

To advance the catalytic applications of s‐block mixed‐metal complexes, sodium magnesiate [NaMg(CH₂SiMe₃)₃] ( 1 ) is reported as an efficient precatalyst for the guanylation of a variety of anilines and secondary amines with carbodiimides. First examples of hydrophosphination of carbodiimides by using a Mg catalyst are also described. The catalytic ability of the mixed‐metal system is much greater than that of its homometallic components [NaCH₂SiMe₃] and [Mg(CH₂SiMe₃)₂]. Stoichiometric studies suggest that magnesiate amido and guanidinate complexes are intermediates in these catalytic routes. Reactivity and kinetic studies imply that these guanylation reactions occur via (tris)amide intermediates that react with carbodiiimides in insertion steps. The rate law for the guanylation of N,N′‐diisopropylcarbodiimide with 4‐tert‐butylaniline catalyzed by 1 is first order with respect to [amine], [carbodiimide], and [catalyst], and the reaction shows a large kinetic isotopic effect, which is consistent with an amine‐assisted rate‐determining carbodiimide insertion transition state. Studies to assess the effect of sodium in these transformations denote a secondary role with little involvement in the catalytic cycle.     

Fabrication of Translucid Gold-Nanocellulose Electrodes and their Potential Application as Hydrogen Peroxide Sensor

In this work, we describe the fabrication of a transparent gold electrode based on nanocellulose. The electrode was prepared via electron beam evaporation of gold onto nanocellulose films previously spread over a glass slip. Electrodes with different thickness of Au was fabricated, and the material's optical, morphological and electrical properties were assessed. Finally, as a proof of concept, a possible application of this electrode in hydrogen peroxide sensing was performed. The results show that a thin layer of gold on a nanocellulose translucid film allows obtaining a conductive transparent surface that could be used to design a transparent electrode.     

Development and validation of new methods for the determination of melatonin and its oxidative metabolites by high performance liquid chromatography and capillary electrophoresis,using multivariate optimization

Melatonin (N-acetyl-5-metoxytriptamine, MEL) has focused a lot of attention as consequence of its multiple functions. MEL is a potent endogenous antioxidant and a free radical scavenger that reacts with several sort of radicals generating various metabolites. Two of them are N1-acetyl-N2-formyl-5-methoxykynurenine (AFMK) and N1-acetyl-5-methoxykynurenine (AMK). These compounds are important because they have also antioxidant actions as well as other important biological properties. In the present work, we develop two methods to detect and quantify these compounds (MEL, AFMK and AMK) in the same sample. For this purpose we used an experimental design, and utilized high performance liquid chromatography (HPLC-DAD) and micellar electrokinetic chromatography (MEKC) techniques with diode array detector in both of them. The limit of detection/quantification for MEL, AFMK and AMK were respectively 44/94, 18/38 and 23/51 ng mL⁻¹ by using HPLC and 13/44, 37/124 and 47/156 ng mL⁻¹ by using MEKC. This is the first time that these compounds have been separated in the same chromatogram or electroferogram. The time of analysis was faster using MEKC. Furthermore, this technique showed better resolution but HPLC offered better limit of detection and quantification for metabolites. Both methods were validated and correlation coefficients were higher than 0.999 and the range of recovery of those methods were 99.6–103.7%. Precision was evaluated as repeatability and intermediate precision with relative standard derivation <5%. When a 5 μg mL⁻¹ solution of these compounds were analyzed with both methods we do not observed any statistically significance differences. Moreover, we analyzed 3COHM (cyclic-3-hydroximelatonin), another known metabolite of melatonin, by using the same methods. The employment of these methods will offer a useful tool to contribute to answer the role of MEL, AFMK and AMK in biological system and both methods can be used in routine analysis for these compounds.     

A new reactivity pattern of low-valent transition-metal hydroxo complexes: straightforward synthesis of hydrosulfido complexes via reaction with carbon disulfide

A new basic transformation linking two important classes of transition metal compounds; namely, hydroxo and hydrosulfido complexes has been discovered.