Publications

Abstract The standard (p degrees = 0.1 MPa) molar energies of combustion of 2-methylbenzoxazole and 2,5-dimethylbenzoxazole were measured by static-bomb combustion calorimetry. The standard molar enthalpies of vapourization, at T = 298.15 K, were obtained from high-temperature Calvet microcalorimetry. The experimental results enable the calculation of the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, for both compounds, being the results discussed in terms of structural and energetic contributions. The theoretically estimated gas-phase enthalpies of formation were calculated from high-level ab initio molecular orbital calculations at the G3(MP2)//B3LYP level of theory. The computed values compare very well with the experimental results obtained in this work and show that the 2,5-dimethylbenzoxazole is enthalpically the most stable compound. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and adiabatic ionization enthalpies.

Abstract Healthy skin contributes not only to the appearance and body homeostasis of people, but also offers barrier protection against pathogen invasion and water loss. Since beauty plays a vital role in most people's lives, novel cosmetic products are always in the pipelines to meet the demand of the consumer. More effective products such as cosmeceuticals and skin nutraceuticals are gaining popularity among consumers. Many nutraceuticals and cosmeceuticals are known to interact with the genome and may therefore cause changes in the skin through altered gene expression. Finding new chemicals and suitable formulations is becoming even more challenging today. Widely investigated formulations include nanotechnology-based carriers such as nanoemulsions, microemulsions and lipid nanoparticles (solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC)). In this chapter, we describe the nature of cosmeceuticals and skin nutraceuticals, the rationale behind their choices, their formulation into nanotechnology based carriers and successful examples of their application for the delivery of active ingredients.

Abstract Semiconductor, silicon and carbon quantum dots (QDs) are fluorescent nanomaterials with increasing scientific and technological applications. Their fluorescent properties are due to quantum confinement effects and/or surface defects and their emission properties can be easily tuned by size control and/or surface chemical modification. Also, they show high quantum yield and carbon and silicon QDs are nonblinking, which makes QDs particularly interesting in many near future technological applications. Localized surface plasmons resonance (LSPR) observed by metallic nanoparticles (MN) is a well known phenomena that is being coupled to QDs to increase their fluorescence when they are deposited in surfaces in close contact with MN. This chapter presents an updated review on the metal enhancement of fluorescence (MEF) of semiconductor, silicon and carbon QDs that is achieved with LSPR. Besides the theoretical aspects of MEF the most important and recent technological applications are described.

Abstract Tamoxifen is a selective estrogen receptor modulator that is used as an adjuvant and/or chemotherapeutic agent for the treatment of all stages of hormone-dependent breast cancer. Currently there is a deep interest in the study of tamoxifen biotransformation and identification of metabolites since they can significantly contribute to the overall pharmacological or adverse effects of the drug. Accordingly, the study of the electrochemical behavior of tamoxifen in aqueous solution is reported. To clarify the occurring oxidative process and to assess the influence of the functional groups on the oxidation mechanism, the voltammetric assessment was extended to the study of tamoxifen's analogues (E)-tamoxifen and dihydrotamoxifen, and to its main phase I oxidative metabolite, N-desmethyl tamoxifen. The data found shows that the oxidative processes occurring in tamoxifen are essentially related with the two chemical moieties present in the molecule: the substituted aromatic nucleus and the tertiary amine group. Moreover, the results obtained suggest that the ethylenic linkage is not critical for tamoxifen's oxidation although it could play an important role in the course of the oxidation process. These results could contribute to highlight some remaining questions regarding tamoxifen's metabolic behavior and to the development of new analytical strategies, based on electrochemical approaches.

Abstract An electrochemical sensor has been developed for the determination of the herbicide bentazone, based on a GC electrode modified by a combination of multiwalled carbon nanotubes (MWCNT) with β-cyclodextrin (β-CD) incorporated in a polyaniline film. The results indicate that the β-CD/MWCNT modified GC electrode exhibits efficient electrocatalytic oxidation of bentazone with high sensitivity and stability. A cyclic voltammetric method to determine bentazone in phosphate buffer solution at pH6.0, was developed, without any previous extraction, clean-up, or derivatization steps, in the range of 10-80μmolL-1, with a detection limit of 1.6μmolL-1 in water. The results were compared with those obtained by an established HPLC technique. No statistically significant differences being found between both methods. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract In the present work we bridge neutron scattering and calorimetry in the study of a low-hydration sample of a 15-residue hybrid peptide from cecropin and mellitin CA(1-7)M(2-9) of proven antimicrobial activity. Quasielastic and low-frequency inelastic neutron spectra were measured at defined hydration levels a nominally 'dry' sample (specific residual hydration h = 0.060 g/g), a H2O-hydrated (h = 0.49) and a D2O-hydrated one (h = 0.51). Averaged mean square proton mobilities were derived over a large temperature range (50-300 K) and the vibrational density of states (VDOS) were evaluated for the hydrated samples. The heat capacity of the H2O-hydrated CA(1-7) M(2-9) peptide was measured by adiabatic calorimetry in the temperature range 5-300 K, for different hydration levels. The glass transition and water crystallization temperatures were derived in each case. The existence of different types of water was inferred and their amounts calculated. The heat capacities as obtained from direct calorimetric measurements were compared to the values derived from the neutron spectroscopy by way of integrating appropriately normalized VDOS functions. While there is remarkable agreement with respect to both temperature dependence and glass transition temperatures, the results also show that the VDOS derived part represents only a fraction of the total heat capacity obtained from calorimetry. Finally our results indicate that both hydration water and the peptide are involved in the experimentally observed transitions.

Abstract COSMO-RS, the Conductor-like Screening Model for Real Solvents, has been used to predict a set of basic partition coefficients of 22 (alkylated) naphthalenes. To validate the approach, methyl-, dimethyl-, and ethylnaphthalenes have been chosen, according to the availability of experimental data. Then, predictions have been extended to diisopropylnaphthalenes. Given the model's expected uncertainty intervals, COSMO-RS predictions of aqueous solubilities, (subcooled) vapor pressures, Henry's law constants, as well as octanol-water partition coefficients, are in agreement with available literature data. Simultaneous overestimation of aqueous solubilities and vapor pressures of comparable magnitude leads to partial error cancellation in the Henry's law constants. Based on physico-chemical property data obtained with COSMO-RS, the Mackay Level III fugacity model, a steady-state, non equilibrium, and regional-scale model, has been applied to exemplary evaluate the tendency of 2,6-diisopropylnaphthalene to migrate between media by modelling emissions to each individual medium and calculating the amount present at steady state.

Abstract A thermodynamic study of important biogenic compounds, (-)-alpha-pinene, (-)-beta-pinene, (-)-cis-verbenol, and (-)-verbenone, is presented in this work. The vapor pressure measurements were performed using the static method over the environmentally important temperature range from 238 to 313 K. The sublimation and vaporization enthalpies were derived from these measurements as well as directly determined by a Calvet high temperature microcalorimeter. Heat capacities of condensed phases were measured by Calvet and drop calorimetry in the temperature interval from 273 to 355 K. The thermodynamic properties of the ideal-gas state were calculated by combining statistical thermodynamics and density functional theory (DFT) calculations. The trends in thermodynamic properties within the group of compounds possessing similar molecular structures are discussed.

Abstract A structural study of three synthesized stereoisomeric oximes, (-)-8-phenylmenthyl glyoxylate oxime (8-PMGO), (+)-8-phenylneomenthyl glyoxylate oxime (8-PnMGO), and (-)-8-phenylisoneomenthyl glyoxylate oxime (8-PinMGO), was performed by means of variable temperature H-1 NMR spectroscopy, X-ray crystallography, and ab initio calculations. It was found that in 8-PMGO a conformation where the phenyl and oxime moieties are stacked is significantly favored, whereas in the other stereoisomers this preference was not so evident. The conformational differences found between the isomers were used to rationalize the outcome of the reaction (simultaneous 1,3-cycloaddition and aza-Diels Alder reaction) between the referred oximes and cyclopentadiene, in which the stereoselectivity was evaluated and found to be nicely reproduced by a simple conformational analysis. The global results indicate that the stereoselectivity of the studied oximes, a bit higher for 8-PMGO, originates from their particular conformational distribution, in which the phenyl. oxime aromatic interaction plays a decisive role.

Abstract The energetic study of benzoxazole, 5-chloro-2-methylbenzoxazole, and 2-chlorobenzoxazole, in condensed and gaseous states, has been developed using experimental techniques and computational approaches. The values of the standard (p degrees = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, of crystalline benzoxazole (36.0 +/- 2.0) kJ . mol(-1) and 5-chloro-2-methylbenzoxazole (145.6 +/- 2.2) kJ . mol(-1) and liquid 2-chlorobenzoxazole (52.5 +/- 3.0) kJ . mol(-1) were determined from the corresponding experimental standard molar energy of combustion in oxygen, -(3432.1 +/- 1.7) kJ . mol(-1), -(3883.0 2.0) kJ . mol(-1), and -(3298.0 +/- 2.8) kJ . mol(-1), respectively, measured by static or rotating-bomb combustion calorimetry. At T = 298.15 K, the standard (p degrees = 0.1 MPa) molar enthalpy of sublimation of benzoxazole and 5-chloro-2-methylbenzoxazole and of vaporization of 2-chlorobenzoxazole, (69.2 +/- 0.8) kJ . mol(-1), (82.4 +/- 2.2) kJ . mol(-1), and (56.3 +/- 1.6) kJ . mol(-1) respectively, were determined by a direct method, using the vacuum drop microcalorimetric technique. From the latter values and from the enthalpies of formation of the condensed compounds, the standard (p degrees = 0.1 MPa) enthalpies of formation of the gaseous compounds have been calculated. Standard ab initio molecular orbital calculations were performed using the G3(MP2)//B3LYP composite procedure and several working reactions in order to derive the standard molar enthalpy of formation of the three compounds. There exists a good agreement between the experimental and the computational data.