Phosphinine-Based Ligands in Gold-Catalyzed Reactions

A series of substituted phosphinines, 1-phosphabarrelenes and 5-phosphasemibullvalenes were synthesized and evaluated for their potential application as ligands in homogeneous catalytic reactions. While their buried volume (%V_bur) was calculated to get insight into the steric properties, [LNi(CO)₃] complexes were prepared in order to determine the corresponding Tolman electronic parameter. ETS-NOCV (extended-transition-state natural orbital for chemical valence) calculations on [LAuCl] complexes further allowed an estimation of the σ- and π-contributions to the L− M interaction. Au^I coordination compounds of selected examples were prepared and characterized by single crystal X-ray diffraction. Finally, the three classes of P^III compounds were successfully used in the Au^I-catalyzed cycloisomerization of N-2-propyn-1-ylbenzamide, showing very good activities and selectivities, which are comparable with the reported data of cationic phosphorus-based gold catalysts.     

Tailoring the properties of electrospun PHBV mats: Co-solution blending and selective removal of PEO

Microstructure, surface topography, thermal and mechanical features of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) electrospun non-woven mats were modified, modulated and tailored through blending with different polyethylene oxide (PEO) amounts (20, 30 and 50% wt/wt). The optimal parameters of the soaking protocol for the selective removal of the sacrificial polymer were accurately identified by means of scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy, simultaneous thermogravimetric and differential analyses (TG-DTA) and differential scanning calorimetry (DSC). The complete PEO removal after soaking in H₂O for 7 days with daily refreshment was confirmed. The resulting samples were only comprised of PHBV fibers characterized by a remarkable decrease of the average size with respect to the respective blends. Their surface topography was corrugated and rough and presented nodules, pits, nanopores, shallow and elongated nanostructured indents/grooves along the fiber axis. A remarkable reduction (>75%) of the tensile modulus (E) of electrospun PHBV mats (15–20 MPa) was obtained, maintaining comparable elongation at break (ε_max) values (20–30%).     

Optimization and validation of organochlorine compounds in adipose tissue by SPE‐gas chromatography

Scientific evidence has shown an association between organochlorine compounds (OCC) exposure and human health hazards. Concerning this, OCC detection in human adipose samples has to be considered a public health priority. This study evaluated the efficacy of various solid‐phase extraction (SPE) and cleanup methods for OCC determination in human adipose tissue. Octadecylsilyl endcapped (C₁₈‐E), benzenesulfonic acid modified silica cation exchanger (SA), poly(styrene‐divinylbenzene (EN) and EN/RP₁₈ SPE sorbents were evaluated. The relative sample cleanup provided by these SPE columns was evaluated using gas chromatography with electron capture detection (GC–ECD). The C₁₈‐E columns with strong homogenization were found to provide the most effective cleanup, removing the greatest amount of interfering substance, and simultaneously ensuring good analyte recoveries higher than 70%. Recoveries > 70% with standard deviations (SD) < 15% were obtained for all compounds under the selected conditions. Method detection limits were in the 0.003–0.009 mg/kg range. The positive samples were confirmed by gas chromatography coupled with tandem mass spectrometry (GC‐MS/MS). The highest percentage found of the OCC in real samples corresponded to HCB, o,p′‐DDT and methoxychlor, which were detected in 80 and 95% of samples analyzed respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Biodegradable PLGA-b-PEG polymeric nanoparticles: synthesis, properties, and nanomedical applications as drug delivery system

Liquid sodium containing titanium nanoparticles (LSnanop) of 10-nm diameter was prepared by dispersing titanium nanoparticles (2 at.% Ti) into liquid sodium with the addition of stirring and ultrasonic sound wave. The titanium nanoparticles themselves were prepared by the vapor deposition method. This new liquid metal, LSnanop, shows a remarkable stability due to the Brownian motion of nanoparticles in liquid sodium medium. In addition, the difference of measured heat of reaction to water between this LSnanop and liquid sodium indicates the existence of cohesive energy between the liquid sodium medium and dispersed titanium nanoparticles. The origin of the cohesive energy, which serves to stabilize this new liquid metal, was explained by the model of screened nanoparticles in liquid sodium. In this model, negatively charged nanoparticles with transferred electrons from liquid sodium are surrounded by the positively charged screening shell, which may inhibit the gathering of nanoparticles by the ??Coulombic repulsion coating.?? The atomic volume of LSnanop shows the shrinkage from the linear law, which also suggests the existence of cohesive energy. The viscosity of LSnanop is almost the same as that of liquid sodium. This behavior was explained by the Einstein equation. The surface tension of LSnanop is 17?% larger than that of liquid sodium. The cohesive energy and the negative adsorption may be responsible to this increase. Titanium nanoparticles in liquid sodium seem to be free from the Coulomb fission. This new liquid metal containing nanoparticles suggests the possibility to prepare various stable suspensions with new properties.     

Porphyrin decorated CdSe quantum dots for direct fluorescent sensing of metal ions

In this study, we report on a novel hybrid structure for the direct sensing of metal ions based on the use of CdSe quantum dots functionalized with tetrapyridyl-substituted porphyrin, a cation-selective carrier. It is shown that the porphyrin ion carrier coordinates to Cd atoms of the CdSe quantum dots through the Lewis basic pyridyl groups. The porphyrin-quantum dot ligation allows for the direct communication between the porphyrin and the underlying CdSe quantum structure. The quantum yield of CdSe is maintained despite the robust capping generated when the unmetallated porphyrins coordinate onto the quantum dots. Upon coordination with zinc ions, this porphyrin capping is shown to strongly contribute to the increase in the fluorescence efficiency of CdSe, via an activating interaction with the quantum dots surface. The results provide the grounds for the development of highly sensitive and selective nano-optode sensing systems.     

Biosensors based on gold nanoelectrode ensembles and screen printed electrodes

Gold nanowires were synthesized within polycarbonate membranes according to an electroless deposition method, obtaining nanoelectrode ensembles (NEEs) with special electrochemical features. NEEs were coupled with home-produced carbon graphite screen printed electrodes and the electrochemical properties of the original nanoelectrode ensemble on screen printed substrate (NEE/SPS) assembly has been tested for sensors application. Glucose oxidase has been used as model enzyme in order to verify the feasibility of disposable gold NEE/SPS biosensors. Finally, different immobilisation and electrochemical deposition techniques based on either self assembled monolayers of cysteamine (CYS) or amino-propyl-triethoxysilane (APTES) and conductive polyaniline (PANI) molecular wires were used. Spatial patterning of the enzyme on the polycarbonate surface and of PANI wires on gold nanoelectrodes was obtained. Possible direct electron transfer between the enzyme and the PANI modified gold nanoelectrodes has been evaluated.