Publications

Abstract Straightforward crushing and sieving bulk polymeric R-aminoglutethimide-imprinted materials were prepared by classical free radical polymerization, whereas nano thin walled grafted imprinted materials were prepared using RAFT mediated control polymerization technique. A stoichiometric non-covalent approach based on a triply hydrogen bonding functional monomer-template 1:1 complex (K = 599 mol(-1) L-1) led to chiral selectors far outperforming previously used selectors for resolving this racemate. The recognitive materials produced here (enantioselectivity factors, alpha similar to 10) also have no match within the previously reported enantioselective imprinted polymers (alpha 1.2-4.5). We here demonstrate a potentially generic solution to produce good quality grafted MIPs for templates interacting by hydrogen bonding alone, relying on solvent polarity tuning, significantly extending the range of templates compatible with this format.

Abstract In this work we report for the first time differential capacitance curves measured at imidazolium dicationic ionic liquid/electrode interfaces as a new strategy to understand the interfacial behaviour of ionic liquids (IL) near a charged electrode. The ionic liquid studied (1,5-bis(3-dimethylimidazolium)pentane di-bis(trifluoromethylsulfonyl)imide [C-5(MIM)(2)][Tf2N](2)) contains a cation with two positively charged imidazolium rings substituted with a methyl group connected by a pentane linkage alkyl chain length providing a new cationic structure variation. The comparison with the analogue monocationic ionic liquids showed that the dicationic liquid has a wider electrochemical polarization window and a more positive potential of zero charge at a Hg electrode. Differential capacity curves measured at dicationic ionic liquid/Hg interface show similar shape compared with analogous monocationic ionic liquids and revealed to be very sensitive to the electrode material.

Abstract The quantification of nitric oxide (NO) based on the quenching of the fluorescence of a nanocomposites sensor constituted by cadmium/selenium quantum dots (CdSe) stabilized by chitosan (CS) and mercaptosuccinic acid (MSA) is assessed. The optimization of the response of the CS-CdSe-MSA nanocomposites to NO was done by multivariate response surface experimental design methodologies. The highest fluorescence quenching was obtained at pH 5.5 and at room temperature. The NO quantification capability of CS-CdSe-MSA was evaluated using standard solutions and a NO donor reagent. A large linear working range from 5 to 200 mu M and a limit of detection of 1.86 mu M were obtained. Better quantification results were obtained using the NO donor reagent. Besides NO, the response of the fluorescence of CS-CdSe-MSA to the main reactive oxygen and nitrogen species and similar NO compounds was also assessed.

Abstract Templated microspheres based on the sol-gel process usually present low density, high surface area, excellent loading capacity, biocompatibility, and high thermal and mechanical stability, which make them ideal for a vast number of applications, from sensors to separation processes. The preparation of these templated microspheres, obtained by some sol-gel route, is here the subject of a review. The purposes and ways of insertion of templates inside a sol-gel matrix are diversified. Most commonly, templates are intended to produce some sort of controlled microstructure, either by simply reverting the volume occupied by the template to pore volume of identical dimensions or by directing the self-organization within the sol-gel network during the synthesis. Mesoporous spherical gels or glasses and composites have extensively been produced in this manner, using surfactants and polymeric materials as preferential templates. It is also common to find the utilization of templates related to the very process of achieving the microspheric format of the gels, which in many instances is designed to produce hollow spheres. Bulky templates in the micrometer range, such as whole cells, other microspheres or gas bubbles, are usually applied for the purpose. Molecularly imprinted microspherical gels have also been reported in the recent years. In this case, an usually small molecule of interest is added as template to the solgel mixture. It is expected that, upon removal from the final gel, the template will leave a cavity with the size and shape of the template, as well as some functionally complimentary chemical microenvironment.

Abstract The role of the electrode material on the interfacial double layer structure of a series of ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([C4MIM][PF6]), 1-butyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide ([C4MIM][Tf2N]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM][BF4]) was investigated on gold (Au) and platinum (Pt) electrodes. The aim of this work is to contribute with experimental data to complement theoretical models that are currently under discussion in order to describe the structure of the double layer formed at the interface electrode/ionic liquid. There is still a controversy about the general shape that differential capacitance curves should present and researchers still continue making efforts to correlate the nature of the electrode/ionic liquid with the shape of the curves. Differential capacitance curves at the Au and Pt interface shows that the values of capacity follow the same order C [C4MIM][PF6] < C [C4MIM][Tf2N] < C [C4MIM][BF4]. However, the values of C are considerably lower for Pt when compared with Au for all three liquids studied. The alkyl chain length effect on the differential capacity curves was also studied at the Pt/[CnMIM][Tf2N] interface (where n = 2, 4 and 6). The results follow an expected trend except for the liquid [C6MIM][Tf2N] that shows a value of capacity near to that obtained for [C2MIM][Tf2N]. Since ionic liquids have great applicability in energy storage devices and capacitors it is of great importance to evaluate the dependence of differential capacitance as function of temperature. The results indicate that the capacity increases with increasing temperature for all systems studied in this work.

Abstract 2-Ethylhexyl 4-methoxycinnamate (EHMC) is a very commonly used UVB filter that is known to isomerize from the (E) to the (Z) isomer in the presence of light. In this study, we have performed high level quantum chemical calculations using density functional theory (DFT) with the B3LYP density functional and extended basis sets to study the gas-phase molecular structure of EHMC and its energetic stability. Calculations were also performed for related smaller molecules cinnamic acid and 4-methoxycinnamic acid. Charge delocalization has been analyzed using natural charges and Wiberg bond indexes within the natural bond orbital analysis and using nucleus independent chemical shifts. Density functional theory calculations reveal that the (E) isomer of EHMC is more stable than the (Z) by about 20kJmol(-1) in both the gas and aqueous phases. The enthalpy of formation in the gas phase of (E)-EHMC was derived from an isodesmic bond separation reaction. Long-range corrected DFT calculations in implicit water were made in order to understand the excited state properties of the (E) and (Z) isomers of EHMC. Copyright (c) 2013 John Wiley & Sons, Ltd.