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The activity and enantiomeric excess (ee) (in some cases >85%) obtained for the asymmetric addition of trimethylsilyl cyanide to aldehydes using different heterogeneous chiral catalysts are compared. A library of recoverable catalysts was developed by immobilization of a chiral vanadyl salen complex having a terminal carbon–carbon double bond onto a series of scaffolds including silica, single-wall carbon nanotubes, activated carbon and room-temperature ionic liquids. The covalent linkage has been achieved by radical initiated addition of mercapto groups to CC. The highest enantiomeric excesses, similar to those obtained in the homogeneous phase, were achieved using silica as support or with the homogeneous tetra-tert-butyl salen catalyst dissolved in an imidazolium ionic liquid. The use of silica as support permits an easier separation and reuse of the catalyst from the reaction media. [Copyright &y& Elsevier]

Two vanadyl salen complexes having peripheral styryl substituents have been reacted with 1-methyl-3-(3-mercaptopropyl)-imidazolium chloride using azoisobutyronitrile as radical initiator. The resulting compounds contain at the same time a vanadyl salen complex and one imidazolium cation. In agreement with the expectations in view of their structure, these compounds were insoluble in conventional organic solvents, but completely miscible in imidazolium ionic liquids. These vanadyl salen complexes bonded to an imidazolium cation are highly active and reusable catalysts for the cyanosilylation of aldehydes. Moderate enantiomeric excesses were obtained using the chiral version of this complex. [Copyright &y& Elsevier]

Ionic liquids with different counter-ion and alkyl substitutes were tested as solvents in the dealkylation and acylation of methyl dehydroabietate, a useful and inexpensive building block for the synthesis of higher diterpenes derivatives. Ionic liquids with halogen counter-ions are very active in both reactions with high rate constant and conversion, avoiding the use of the conventional solvents (benzene and carbon disulfide) in these reactions. In the dealkylation reaction, the change of counter-ion from halogens to tetrafluoroborate had a dramatic effect on the stereoselectivity, showing the importance of the counter-ion in the course of the reactions. [Copyright &y& Elsevier]

The chemiluminescence of several naphthalene-based luminol analogues is characterized and compared with that of luminol. The compounds produce a strong greenish or green-yellow chemiluminescence in alkaline aqueous and nonaqueous solutions by reaction with hydrogen peroxide in the presence of hexacyanoferrate (III). The results point to the possibility of increasing the sensitivity of analytical methods currently based on luminol. The photophysics of the oxidation products is also studied. The solubility of some of the new compounds in aqueous solution is significantly increased using a nonionic surfactant Triton X-100. Increase of the chemiluminescence intensity in aqueous micellar media was observed. The location of the oxidation product 3-aminophthalate in the external hydrophilic shell of the micelle was established using its intrinsic fluorescence by iodide. The described luminol analogues may prove of interest in forensic and other applications. • The chemiluminescence of several naphthalene-based luminol analogues is characterized and compared with that of luminol. • Green chemiluminescence in aqueous and nonaqueous solutions in the presence of hexacyanoferrate (III) were recorded. • The chemiluminescence of the naphthalene-based luminol analogues in micellar media were also performed. • The location of the oxidation product 3-APA in micelles was evaluated by measuring the fluorescence quenching by iodide. [ABSTRACT FROM AUTHOR]

Boron is a key element for some biological processes,but it becomes toxic for humans and plants in concentrations above a few ppm. We have design a new approach for boron scavenging, based in hybrid membranes of functional mesoporous silica nanoparticles immobilized in cellulose acetate. The mesoporous silica nanoparticles, with diameters around 150 nm, were functionalized with vicinal diol groups that complex boron very efficiently. The functional nanoparticles were covalently immobilized in a cellulose acetate membrane using a di-terminated alkoxisilane that react with the remaining silanol groups at the nanoparticles surfaces and with the hydroxyl groups of the cellulose. The functional nanoparticles and the hybrid membranes show boron removal efficiencies of phenyl boronic acid of up to 93%. The membranes can be used in multistage filtering systems, with sequential membranes modules in continuous operation, in a cheap, simple and efficient process for boron scavenging. [ABSTRACT FROM AUTHOR]

Boron is biologically beneficial but only in trace quantities. It is hard to detect and remove from water, as sometimes required in the treatment of residual waters. We have designed an approach based on thermo-responsive polymer nanoparticles containing vicinal diol groups for boron scavenging. The particles have a core of poly(methyl methacrylate) (PMMA) and a thermosensitive shell with a brush composed of a copolymer of N -isopropylacrylamide (NIPAM), 2-aminoethyl methacrylate (AEMH), and either d -gluconoamidoethyl methacrylate (GAEM) or monodiol methacrylate (MDM) boron chelating monomers. The nanoparticles show boron removal efficiencies of up to 96%, with removal of phenylboronic acid being more efficient than that of boric acid. The best boron scavenging efficiency was obtained for the higher specific surface area particles containing d -gluconoamidoethyl groups. At temperatures above ca. 35 °C the particle shell collapses, inducing particle aggregation which allows simple separation and recovery of the nanoparticles. These can be subsequently used for boron scavenging, without loss of efficiency. [ABSTRACT FROM AUTHOR]

We describe the preparation of very bright and photostable fluorescent silica nanoparticles (SiNPs), with emission in the visible or in the near infrared (NIR). The nanoparticles can be prepared with diameters of 30–300 nm with low size dispersity, and incorporate perylenediimide (PDI) dyes modified with alkoxysilane groups that react with the silica structure. One of the dyes ( PDIvis ) emits in the green and the other ( PDInir ) in the NIR (with fluorescence quantum yields of 90% and 24%, respectively). Silica nanoparticles containing these dyes were efficiently internalized in HEK293 cells with low toxicity and reveled very high photostability, showing good potential for use as a platform for in vivo laser scanning bioimaging applications. The NIR emitting nanoparticles, in particular, can be used in multi-color imaging, even in cells expressing high levels of fluorescent proteins and/or co-stained with different fluorescent dyes (most of which commonly emit at wavelengths lower than the NIR). [ABSTRACT FROM AUTHOR]

Abstract: A three-component condensation reaction between aminopyrazolo[3,4-d]pyrimidine, an aldehyde, and an isocyanide catalyzed by scandium triflate yields a series of heterocyclic derivatives of imidazo[1,2-c]pyrazolo[3,4-d]pyrimidine in good yields, exhibiting interesting fluorescent properties. [Copyright &y& Elsevier]

Abstract: It is shown that pristine fullerene C70 can be solubilised in imidazolium, ammonium and phosphonium based ionic liquids (ILs) bearing long alkyl chains (C8 or higher). The absorption and fluorescence properties are similar to those displayed in conventional polar solvents except in ILs containing chloride as the counter ion, which completely quench the fluorescence of C70. Fluorescence decay analysis using a sum of Becquerel functions to account for the complex decay of background emission allows the successful recovery of the solute’s lifetime. [ABSTRACT FROM AUTHOR]

Multifunctional polymeric coatings containing drug delivery vehicles can play a key role in preventing/reducing biofilm formation on implant surfaces. Their requirements are biocompatibility, good adhesion, and controllable drug release. Although cellulose acetate (CA) films and membranes are widely studied for scaffolding, their applications as a protective coating and drug delivery vehicle for metal implants are scarce. The reason is that adhesion to stainless steel (SS) substrates is non-trivial. Grinding SS substrates enhances the adhesion of dip-coated CA films while the adhesion of electrospun CA membranes is improved by an electrosprayed chitosan intermediate layer. PMMA microcapsules containing daptomycin have been successfully incorporated into CA films and fibres. The released drug concentration of 3 × 10−3 mg/mL after 120 min was confirmed from the peak luminescence intensity under UV radiation of simulated body fluid (SBF) after immersion of the fibres. [ABSTRACT FROM AUTHOR]

Improving the efficiency of photon upconversion in small organic molecules is a challenge where the molecular framework of perylene-3,4,9,10-tetracarboxylic acid diimides (PDIs) can provide meaningful achievements. To disentangle the different factors that can affect the n6onlinear optical response of such framework we present a systematic study of the two-photon absorption (TPA) properties of substituted PDIs addressing effects such as distortion from planarity, inductive vs. conjugative substituents, symmetric vs. asymmetric substitution of the bay positions and electron donor (D) vs. acceptor (A) nature of the bay substituents. The best performance in terms of nonlinear absorption was found in tetra-phenoxy bay-substituted PDIs with an A-PDI-A architecture that shows a TPA cross-section one order of magnitude higher than that of planar unsubstituted PDI, despite its distortion from planarity. This study constitutes a paradigmatic example of twisted core PDIs with enhanced optical properties. Twisted core perylenediimides (PDIs) show enhanced nonlinear optical brightness in a study that disentangles the relevance of different factors affecting the nonlinear optical response of bay substituted PDIs such as planarity, inductive vs. conjugative substituents, symmetric vs. asymmetric substitution of the bay positions and electron donor vs. acceptor nature of the substituent. The best performance was obtained for a tetra-substituted PDI despite its distortion from planarity. [Display omitted] • Systematic study of the two-photon absorption properties of bay substituted PDIs. • Disentangle the different factors affecting PDIs nonlinear response. • Planarity, inductive/conjugate, symmetric/asymmetric, electron donor/acceptor. • Best performance obtained for a tetra-substituted PDI despite its distortion. [ABSTRACT FROM AUTHOR]

Composites based on a piezoelectric polymer (PVDF) doped with different silica nanoparticles (SiNPs) content (8, 16 and 32 wt%) and functionalization (WF-without, NF-negative and PF-positive) have been investigated. Composite films were prepared by solvent casting and melt crystallization to investigate the effect of the presence of the SiNPs on the physico-chemical characteristics and, in particular, in the nucleation of the electroactive β- phase of the polymer. It is shown that the introduction of the SiNPs allows to increase water surface angle up to 34% with respect to α- PVDF, as well to increase the elastic modulus. Filler content and type have an important effect on the nucleation of the electroactive beta phase content and the dielectric properties of the composites, the larger values of both being obtained for positively surface charged nanoparticles. It is concluded that, taken into consideration the overall properties of the composites, the SiNPs-PF/PVDF nanocomposites with 8 wt% filler content offer a promising approach for applications due to the improvement of the electroactive phase of PVDF. Image 1 [ABSTRACT FROM AUTHOR]