Tailored covalent grafting of hexafluoropropylene oxide oligomers onto silica nanoparticles: toward thermally stable, hydrophobic, and oleophobic nanocomposites

The modification of silica nanoparticles with hexafluoropropylene oxide (HFPO) oligomers has been investigated. HFPO oligomers with two different average degrees of polymerization (DPn = 8 and 15) were first prepared by anionic ring-opening polymerization, deactivated by methanol, and in some cases postfunctionalized by aminopropyl(tri)ethoxysilane or allylamine. The "grafting onto" reactions of these oligomers were then carried out either on bare silica (reaction between a silanol surface and ethoxy-silanized HFPO) or on silica functionalized by amino groups (in an amidation reaction with methyl ester-ended HFPO) or mercapto groups (via the radical addition of allyl-functionalized HFPO). Hybrid nanoparticles thus obtained were characterized by solid-state (29)Si NMR and FTIR spectroscopies as well as elemental and thermogravimetric analyses. The results assessed a significant yield of covalent grafting of HFPO oligomers when performing the hydrolysis-condensation of ethoxylated HFPO on the bare silica surface, compared to the other two methods that merely led to physically adsorbed HFPO chains. Chemically grafted nanohybrids showed a high thermal stability (up to 400 °C) as well as a very low surface tension (typically 5 mN/m) compared to physisorbed complexes.     

A method for dating small amounts of uranium

In this study we describe a method for uranium dating (i.e. determination of the date of the last chemical purification undergone by the material) by measurement of the ²³⁰Th/²³⁴U ratio, applicable to sub-microgram quantities. The chosen protocol (AG1x8 resin in hydrochloric acid medium) has been tested on separation microcolumns (100 μl). This ‘microchemistry’ technique considerably limits the risks of contamination by reagents or the environment. Thorium extraction efficiencies were greater than 90 % and reproducible. The quantities of ²³⁰Th introduced by the chemical purification procedure were negligible. Using an ultra-sensitive inductively coupled plasma mass spectrometry measurement technique, detection limits of the order of femtograms (10^?15 g) of ²³⁰Th were obtained. The complete procedure, chemical separation and isotope measurement, was successfully tested and validated on a few micrograms of uranium.     

Stable Anilinyl Radicals Coordinated to Nickel: X‐ray Crystal Structure and Characterization

Two anilinosalen and a mixed phenol‐anilinosalen ligands involving sterically hindered anilines moieties were synthesized. Their nickel(II) complexes 1 , 2 , and 3 were prepared and characterized. They could be readily one‐electron oxidized (E_1/2=?0.30, ?0.26 and 0.10 V vs. Fc⁺/Fc, respectively) into anilinyl radicals species [ 1]⁺ , [ 2]⁺ , and [ 3]⁺ , respectively. The radical complexes are extremely stable and were isolated as single crystals. X‐ray crystallographic structures reveal that the changes in bond length resulting from oxidation do not exceed 0.02 Å within the ligand framework in the symmetrical [ 1]⁺ and [ 2]⁺ . No quinoid bond pattern was present. In contrast, larger structural rearrangements were evidenced for the unsymmetrical [ 3]⁺ , with shortening of one C_ortho? C_meta bond. Radical species [ 1]⁺ and [ 2]⁺ exhibit a strong absorption band at around 6000 cm^?1 (class III mixed valence compounds). This band is significantly less intense than [ 3]⁺ , consistent with a rather localized anilinyl radical character, and thus a classification of this species as class II mixed‐valence compound. Magnetic and electronic properties, as well as structural parameters, have been computed by DFT methods.     

Molecular Recognition of Rosmarinic Acid from Salvia sclareoides Extracts by Acetylcholinesterase: A New Binding Site Detected by NMR Spectroscopy

Acetylcholinesterase (AChE) inhibition is one of the most currently available therapies for the management of Alzheimer’s disease (AD) symptoms. In this context, NMR spectroscopy binding studies were accomplished to explain the inhibition of AChE activity by Salvia sclareoides extracts. HPLC‐MS analyses of the acetone, butanol and water extracts eluted with methanol and acidified water showed that rosmarinic acid is present in all the studied samples and is a major constituent of butanol and water extracts. Moreover, luteolin 4′‐O‐glucoside, luteolin 3′,7‐di‐O‐glucoside and luteolin 7‐O‐(6′′‐O‐acetylglucoside) were identified by MS² and MS³ data acquired during the LC‐MSⁿ runs. Quantification of rosmarinic acid by HPLC with diode‐array detection (DAD) showed that the butanol extract is the richest one in this component (134 μg mg^?1 extract). Saturation transfer difference (STD) NMR spectroscopy binding experiments of S. sclareoides crude extracts in the presence of AChE in buffer solution determined rosmarinic acid as the only explicit binder for AChE. Furthermore, the binding epitope and the AChE‐bound conformation of rosmarinic acid were further elucidated by STD and transferred NOE effect (trNOESY) experiments. As a control, NMR spectroscopy binding experiments were also carried out with pure rosmarinic acid, thus confirming the specific interaction and inhibition of this compound against AChE. The binding site of AChE for rosmarinic acid was also investigated by STD‐based competition binding experiments using Donepezil, a drug currently used to treat AD, as a reference. These competition experiments demonstrated that rosmarinic acid does not compete with Donepezil for the same binding site. A 3D model of the molecular complex has been proposed. Therefore, the combination of the NMR spectroscopy based data with molecular modelling has permitted us to detect a new binding site in AChE, which could be used for future drug development.     

Instantaneous synthesis of stable zerovalent metal nanoparticles under standard reaction conditions

In this report is discussed a novel, easy, and general synthesis method to prepare zerovalent iron (ZVI) and copper (ZV Cu) nanoparticles (NPs), from colloid dispersions in an environmental friendly organic solvent, ethylene glycol (EG). Conventional metallic salts are used as nanoparticle precursors; sodium borohydride (NaBH4) is the reducing agent, and triethylamine (TEA) is used as the nanoparticle stabilizer. The chemical changes take place instantaneously under normal reaction conditions. Small iron (alpha-Fe0 phase) and copper (fcc phase) NPs with average diameters of 10.2 +/- 3.3 and 9.5 +/- 2.5 nm, respectively, were obtained. In both cases, the experimental evidence reveals the absence of any metal oxide shell coating the particle surfaces, and their powders remain stable, under aerobic conditions at least for 3 weeks. ZVI NPs were characterized by X-RD, M?ssbauer, and Raman spectroscopies and by EELS coupled to HR-TEM. Otherwise, copper NPs were characterized by X-RD, Z-contrast, and HR-TEM. This synthesis pathway is particularly suitable for large-scale and high-quality zerovalent metallic nanoparticle (ZV M NP) production due to its simple process and low cost.     

A chiral liquid chromatography method for the simultaneous determination of oxcarbazepine, eslicarbazepine, R-licarbazepine and other new chemical derivatives BIA 2-024, BIA 2-059 and BIA 2-265, in mouse plasma and brain

Recently, in silico models have been developed to predict drug pharmacokinetics. However, before application, they must be validated and, for that, information about structurally similar reference compounds is required. A chiral liquid chromatography method with ultraviolet detection (LC‐UV) was developed and validated for the simultaneous quantification of BIA 2–024, BIA 2–059, BIA 2–265, oxcarbazepine, eslicarbazepine (S‐licarbazepine) and R‐licarbazepine in mouse plasma and brain. Compounds were extracted by a selective solid‐phase extraction procedure and their chromatographic separation was achieved on a LiChroCART 250–4 ChiraDex column using a mobile phase of water–methanol (92:8, v/v) pumped at 0.7 mL/min. The UV detector was set at 235 nm. Calibration curves were linear (r² ≥ 0.996) over the concentration ranges of 0.2–30 µg/mL for oxcarbazepine, eslicarbazepine and R‐licarbazepine; 0.2–60 µg/mL for the remaining compounds in plasma; and 0.06–15 µg/mL for all the analytes in brain homogenate. Taking into account all analytes at these concentration ranges in both matrices, the overall precision did not exceed 9.09%, and the accuracy was within ±14.3%. This LC‐UV method is suitable for carrying out pharmacokinetic studies with these compounds in mouse in order to obtain a better picture of their metabolic pathways and biodistribution. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetics of RAFT homopolymerisation of vinylbenzyl chloride in the presence of xanthate or trithiocarbonate

The RAFT homopolymerisation of vinylbenzyl chloride (VBC, or chloromethyl styrene CMS) in bulk and in acetonitrile initiated by α,α′-azoisobutyronitrile (AIBN) in the presence of two chain transfer agents, O-ethyl-S-(1-methyloxycarbonyl)ethyl xanthate and dibenzyl trithiocarbonate, is presented. The reactions were monitored by ¹H nuclear magnetic resonance spectroscopy in the presence of 1,2-dichloroethane as the internal standard. Such a technique enabled one to assess the evolutions of log ([M]₀/[M]) and VBC conversion vs. time that were shown to be linear. Tobolsky’s law allowed one to determine the square of the propagation rate constant to the termination rate constant, $k_{\text{p}}^2/k_{\text{te}}$, of VBC, that worths about 3 × 10^?3 l mol^?1 s^?1 at 80 °C. On the one hand, the controlled character of the polymerisation involving dibenzyl trithiocarbonate was confirmed by size exclusion chromatography. On the other hand, the molar masses of poly(VBC) polymerised in the presence of the xanthate agent decreased with monomer conversion, as already stated with the macromolecular design via interchange of xanthates (MADIX) polymerisation of styrene.     

Determination of Cd levels in smoke condensate of Brazilian and Paraguayan cigarettes by Thermospray Flame Furnace Atomic Absorption Spectrometry (TS-FF-AAS)

In this study, the concentrations of Cd in smoke condensate of Paraguayan and Brazilian full flavor normal size cigarettes were determined. A “fishtail” chimney was used to confine and direct cigarette smoke to an impaction trap followed by 3 MCE (mixed cellulose ester) filters for smoke collection. The smoke condensate collected at the first two collection stages (chimney and impactor) was prepared as Triton X-100 slurry samples and the 3 MCE filters (third collection stage) used to collect smoke were microwave digested. Samples were analyzed by Thermospray Flame Furnace Atomic Absorption Spectrometry (TS-FF-AAS) for Cd and the results obtained were compared with Graphite Furnace Atomic Absorption Spectrometry (GFAAS). No significant differences were found between the values obtained with TS-FF-AAS and GFAAS at a 95% confidence level. The total concentration of Cd in the smoke of Brazilian and Paraguayan cigarettes tested ranged from 187 to 281 ng/cigarette and from 176 to 271 ng/cigarette, respectively. The LODs for Cd using TS-FF-AAS and GFAAS, were 5.8 and 1.5 ng/cigarette, respectively, for the analysis of smoke condensate from 1 cigarette. The main advantages of using the simple TS-FF-AAS system are its low running costs and the analysis time when compared to GFAAS.     

Preparation and characterization of chloroaluminum phthalocyanine-loaded solid lipid nanoparticles by thermal analysis and powder X-ray diffraction techniques

Solid lipid nanoparticles (SLN) without drug and SLN loaded with chloroaluminum phthalocyanine (AlClPc) were prepared by solvent diffusion method in aqueous system and characterized by thermal analyses and X-ray diffraction (XRD) in this study. Determination of particle size, zeta potential (ZP), and encapsulation efficiency were also evaluated. SLN containing AlClPc of nanometer size with high encapsulation efficiency and ZP were obtained. The results indicated that the size of SLN loaded with AlClPc is larger than that of the inert particle, but ZP is not changed significantly with incorporation of the drug. In differential scanning calorimetry (DSC) curves, it was observed that the melting point of stearic acid (SA) isolated and in SLN occurred at 55 and 64 °C, respectively, suggesting the presence of different polymorphs. DSC also shows that the crystallinity state of SLN was much less than that of SA isolated. The incorporation of drug in SLN may have been favored by this lower crystallinity degree of the samples. XRD techniques corroborated with the thermal analytic techniques, suggesting the polymorphic modifications of stearic acid.