Stability of Phosphonic Self Assembled Monolayers (SAMs) on Cobalt Chromium (Co-Cr) Alloy under Oxidative conditions

Cobalt chromium (Co-Cr) alloys have been widely used in the biomedical arena for cardiovascular, orthopedic and dental applications. Surface modification of the alloy allows us to tailor the interfacial properties to address critical challenges of Co-Cr alloy in medical applications. Self assembled monolayers (SAMs) of Octadecylphosphonic acid (ODPA) have been used to form thin films on the oxide layer of the Co-Cr alloy surface by solution deposition technique. The SAMs formed were investigated for their stability to oxidative conditions of ambient laboratory environment over periods of 1, 3, 7 and 14 days. The samples were then characterized for their stability using X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and contact angle measurements. Detailed high energy XPS elemental scans confirmed the presence of the phosphonic monolayer after oxidative exposure which suggested that the SAMs were firmly attached to the oxide layer of Co-Cr alloy. AFM images gave topographical data of the surface and showed islands of SAMs on Co-Cr alloy surface, before and after SAM formation and also over the duration of the oxidative exposure. Contact angle measurements confirmed the hydrophobicity of the surface over 14 days. Thus the SAMs were found to be stable for the duration of the study. These SAMs could be subsequently tailored by modifying the terminal functional groups and could be used for various potential biomedical applications such as drug delivery, biocompatibility and tissue integration.     

Analysis of personal care products on model skin surfaces using DESI and PADI ambient mass spectrometry

Two ambient ionisation techniques, desorption electrospray ionisation (DESI) and plasma assisted desorption ionisation (PADI), have been used to analyse personal care products (PCPs) on fixed fibroblast cell surfaces. The similarities and differences between the two techniques for this type of analysis have been explored in various ways. Here, we show the results of DESI and PADI analysis of individual PCP ingredients as well as the analysis of these as complex creams on model skin surfaces, with minimal sample preparation. Typically, organosiloxanes and small molecules were detected from the creams. A study of the morphological damage of the fibroblast cells by the two ionisation techniques showed that for a less than 10% reduction in cell number, acquisition times should be limited to 5 s for PADI, which gives good signal levels; with DESI, the morphological damage was negligible. The operating parameters for the plasma source were optimised, and it was also found that the parameters could be modified to vary the relative intensity of different ions in the mass spectrum.     

The instructive redox behaviour of 4‐ferrocenylcatechol on nanocrystalline titanium dioxide electrodes

An investigation into the redox behaviour of 4‐ferrocenylcatechol bound to nanocrystalline TiO₂ electrodes identified a limitation to the use of catechol as an electron‐transfer facilitating anchoring group. 4‐Ferrocenylcatechol was adsorbed to transparent nanocrystalline TiO₂ electrodes. UV–visible spectra of the modified electrode were recorded in an acetonitrile‐electrolyte solution. At an applied potential of + 0.45 mV (vs Ag/AgCl/Cl^?) the ferrocenyl group oxidized to the ferrocenium cation and the catecholate group oxidized to the benzoquinone form. Subsequent application of a potential of 0 V reduced the ferrocenium to ferrocene but, owing to the irreversibility of the catechol oxidation in aprotic solvents, benzoquinone is not reduced to catecholate and subsequently desorbs and is lost due into solution. Electrochromic switching of the ferrocenyl electrochromophore on TiO₂ with aprotic electrolyte is, therefore, irreversible. Copyright © 2006 John Wiley & Sons, Ltd.     

Synthesis,characterization, crystal structure and toxicity evaluation of Co (II), Cu (II), Mn (II), Ni (II), Pd (II) and Pt (II) complexes with Schiff base derived from 2-chloro-5-(trifluoromethyl)aniline

A bidentate NO donor Schiff base, 2-(((2-chloro-5- (trifluoromethyl)phenyl)imino)methyl) phenol ( HL ¹ ) and its complexes [Co(L¹)₂(H₂O)₂] ( 1 ), [Cu(L¹)₂] ( 2 ), [Mn(L¹)₂(H₂O)₂] ( 3 ), [Ni(L¹)₂(H₂O)₂] ( 4 ), [Pd₂(L¹)₂(OAc)₂·1.16H₂O] ( 5 ), [Pt(L¹)₂] ( 6 ) were synthesized and characterized by different physico-chemical techniques including elemental and thermal analysis, magnetic susceptibility measurements, molar electric conductivity, IR, ¹H-NMR, ¹³C-NMR, UV–Vis, mass spectroscopies and X-ray powder diffraction (XRD). The molecular structures of ligand HL ¹ and two complexes ( 2 and 5 ) were confirmed by X-ray crystallography analysis on the monocrystal. In this complexes, the metal ions are in distorted square-planar environments. The copper (II) complex is mononuclear and crystallized in a monoclinic space group P21/c, whereas palladium (II) complex is dinuclear and crystallized in the trigonal crystal system R-3. The toxicity of the ligand and complexes was evaluated on both plant and animal cells, using the plant species Triticum aestivum L. and the crustacean Artemia franciscana Kellogg. At concentrations up to 100 μM the compounds presented very little toxicity on Artemia franciscana Kellogg. Moreover, the palladium (II) complex was devoid of any toxicity on the plant cells.     

A new,one-pot,multicomponent synthesis of 5-aza-9-deaza-adenines under microwave irradiation

A new, practical, three-component method for the synthesis of 5-aza-9-deaza-adenines is developed. Aminopyrazoles react in a one-pot fashion with triethyl orthoformate and cyanamide under microwave irradiation affording 5-aza-9-deaza-adenines in good yields and high purity. The main advantages of this method are the operational simplicity, accessibility, and high efficiency.     

Development and evaluation of methods for determination of naphthodianthrones and flavonoids in St. John's wort

Several major constituents in St. John's wort were determined for a homogenized plant sample. Three extraction techniques were evaluated: Soxhlet extraction, pressurized-fluid extraction (PFE), and sonication extraction. Levels of nine constituents (chlorogenic acid, rutin, hyperoside, isoquercitrin, quercitrin, quercetin, amentoflavone, pseudohypericin, and hypericin) were measured using liquid chromatography with ultraviolet/visible absorbance, mass spectrometric, and fluorescence detection. Levels of total naphthodianthrones determined by liquid chromatography (LC) with absorbance detection at 590 nm were compared with levels determined by direct spectrophotometry at the same wavelength. Additionally, the methods described in this paper were applied to several brands of St. John's wort finished products.     

Experimental design considerations in quantification experiments by using the internal standard technique: cholesterol determination by gas chromatography as a case study

An overview on experimental design in quantification experiments using the internal standard technique is described. Particular emphasis is given to the modelling of the relationship analyte/internal standard and the estimation of the optimal amount of internal standard to be used throughout the analytical concentration range by using a uniform shell design with a minimum number of seven experiments. The described approach is demonstrated in the analysis of cholesterol in various reference materials by gas chromatography (GC), using alpha-5 cholestan as internal standard. The outlined approaches can be applied in the determination of any kind of analyte.     

A new practical synthesis of 3-amino-substituted 5-aminopyrazoles and their tautomerism

It was found that 3-amino-substituted 5-aminopyrazoles could be effectively prepared via hydrolytic decarboxylation of the corresponding 3,5-diaminopyrazole-4-carboxylates under microwave irradiation. The reactions required short time (4?min) and were successfully reproduced in a larger scale and under conventional heating mimicking the microwave heating pattern. X-ray crystallography identified two different types of tautomers in crystals of related 5-aminopyrazoles with p-toluidyl and p-anisidyl moieties at the position 3, respectively.     

Determination of tritium levels in environmental samples around NIPNE,Romania from 2007 to 2017

National Institute for Physics and Nuclear Engineering (NIPNE) Romania is located in Măgurele and approximately 10 km from Bucharest. A continued surveillance over the past 10 years offers the opportunity to verify the tritium releases, but also for development of monitoring methods. The determined levels are well below the maximum admissible limits for environmental samples. Dose values have no impact on the environment and have an insignificant contribution to the cumulative annual dose. Comparison with global, regional and zonal levels highlights the role played by its emissions in the Lower Danube Basin, the Romanian Plain and the Danube Meadow.