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The FT-IR and vibrational circular dichroism (VCD) spectra of ( S )- and -( R )-methyl lactate have been recorded for neat samples and at various concentrations in CCl 4 and DMSO solutions. These spectra are used to analyse the FT-IR and VCD spectra of methyl lactates in presence of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in CCl 4 , where the surfactant molecules are known to form reverse micelles. Some tendency of methyl lactate to interact with AOT micellar aggregates is observed, but not as well defined as previously observed for dimethyl tartrate in analogous circumstances. Besides, near infrared (NIR) absorption and VCD data have been obtained for most of the above systems, allowing to monitor the first overtone of the OH-stretching vibration of methyl lactates, especially in the spectroscopic region where the OH bond is not involved in hydrogen bond with other molecules. The NIR absorption and NIR VCD data for dilute solutions are reproduced and interpreted by anharmonic DFT calculations. Further understanding of the behavior of aggregated methyl lactate systems has been gained on this basis.

The formation and structural features of positively mono-charged aggregates of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium methane—(MetS), butane—(ButS) and octane—(OctS) sulfonate molecules in the gas phase have been investigated by electrospray ionization mass spectrometry, energy-resolved mass spectrometry and density functional theory (DFT) calculations. The experimental results show that the center-of-mass collision energy required to dissociate 50% of these mono-charged aggregates scantly depends on the length of the alkyl chain as well as on the aggregation number. This, together with the large predominance of mono-charged species in the mass spectra, was rationalized in terms of an aggregation pattern mainly driven by the counter ions and head groups electrostatic interactions while minor effects were attributed to the steric hindrance caused by the size of the surfactant head group and alkyl chain. DFT calculations show that the most favored structural arrangement of these aggregates is always characterized by an internal polar core constituted by the sodium counter ions and surfactant head groups surrounded by an external layer composed by the surfactant alkyl chains.

Self-assembling of amphiphilic molecules under electrospray ionization (ESI) conditions is characterized by quite unexpected phenomenology. The noticeable differences with respect to the condensed phase are attributable to the absence of the surfactant-solvent interactions, the presence of net charge in the aggregates, and the strong deviation from equilibrium conditions. Aiming to investigate the effects of the net charge on abundance and stability of supramolecular surfactant aggregates, positively and negatively charged aggregates of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium methane sulfonate (MetS), butane sulfonate (ButS) and octane sulfonate (OctS) have been studied by ESI mass spectrometry, energy resolved mass spectrometry and density functional theory calculations. The negatively charged aggregates are found to be less stable than their positive counterparts. The results are consistent with a self-assembling pattern dominated by electrostatic interactions involving the counterions and head groups of the investigated amphiphilic compounds while the alkyl chains point outwards, protecting the aggregates from unlimited growth processes.

Novel photoluminescent materials formed by some selected surfactants, metal derivatives of bis(2-ethylhexyl) sulfosuccinate (M(AOT)n; M = Na+, Co2+, Er3+ and Yb3+), bis(2-ethylhexyl) amine (BEEA), bis(2-ethylhexy1) phosphoric acid (HDEHP) and a 1:1 BEEA/HDEHP mixture, doped with the red perylimide (ROT-300) have been prepared, and their optical properties have been tested by absorption spectroscopy and steady state and timeresolved fluorescence. Experimental results show spectral shifts of the typical ROT-300 absorption and fluorescence bands with respect to that in apolar solvent medium. Data analysis leads consistently to attribute this feature mainly to the freezing of the diffusive movement of the dye molecules confined in the nanodomains of the surfactant liquid crystals, whilst minor effects can be due to interaction with the surfactant polar groups. Potentialities of these novel luminescent nanostructured composites as dye lasers, optical amplifiers and solar concentrators have been highlighted. In particular, under optical pumping using a pulse laser, amplified spontaneous fluorescence emission of the ROT-300/HDEHP system above an excitation energy threshold value of about 725 mJ cm-2 was observed. © Springer Science+Business Media, LLC 2011.

Cobalt nickel bimetallic nanoparticles were synthesized by changing the sequence of the chemical reduction of Co(II) and Ni(II) ions confined in the core of bis(2-ethylhexyl)phosphate (2)., and Ni(DEHP)(2). The reduction was carried out by mixing, sequentially or contemporaneously, fixed amounts of n-heptane solution of Co(DEHP)2 and Ni(DEHP)2 micelles with a solution of sodium borohydride in ethanol at a fixed (reductant)/(total metal) molar ratio. This procedure involves the rapid formation of surfactant-coated nanoparticles, indicated as Co/Ni (Co after Ni), Ni/Co (Ni after Co), and Co + Ni (simultaneous), followed by their slow separation as nanostructures embedded in a sodium bis(2-ethylhexyl)phosphate matrix. The resulting composites, together with those obtained by reducing the n-heptane solutions of pure Co(DEHP)(2) or Ni(DEHP)(2), were characterized by XPS, EXAFS, WAXS, and SAXS. The data analysis confirms the presence of nanometer-sized surfactant-coated cobalt, nickel, and cobalt/nickel particles. As expected, the composition and internal structure of cobalt/nickel bimetallic nanoparticles are influenced by the preparation sequence as well as by the "chemical affinity" between the surfactant and the metal. However, some atomic-scale physicochemical processes play a subtle role in determining the structural features of bimetallic nanoparticles. Further effects due to the competition between nanoparticle growing process and surfactant adsorption at the nanoparticle surface were observed.

The photophysical and photochemical properties of the cationic Zn II complex of 5-triethyl ammonium methyl salicylidene ortho-phenylendiimine (ZnL 2+ ) interacting with native DNA were investigated by steady state and time-resolved fluorescence spectroscopies. Experimental results indicate that, in the presence of DNA, ZnL 2+ is efficiently protected from a photochemical process, which occurs when it is in the free state dispersed in aqueous solution. The analysis of the absorption and emission spectra of ZnL 2+ , both stored in the dark and after exposure to tungsten lamp light for 24 h, corroborated by quantum chemical calculations, allowed us to point out that ZnL 2+ undergoes a photoinduced two-electron oxidation process. According to this picture, the protective action of DNA toward the intercalated ZnL 2+ was attributed to an effective inhibition of the ZnL 2+ photooxidation. In this context, it can be considered that DNA-intercalated ZnL 2+ is located in a region more hydrophobic than that sensed in the bulk water solvent. Moreover, by a thorough analysis of steady state and time-resolved fluorescence spectra, the interaction process can be consistently explained in terms of a complete intercalation of the complex molecules and that the polarity of the environment sensed by intercalated ZnL 2+ is comprised between that of methanol and ethanol.

Surfactant-based liquid mixtures constitute an interesting class of nanostructured materials with promising potential in specialized applications. Here, structural and conductometric properties of liquid mixtures composed of bis(2-ethylhexyl)amine (BEEA) and bis(2-ethylhexyl)phosphoric acid (HDEHP) have been thoroughly investigated with the aim to correlate structural features with system charge transport capability. The evolution of self-assembled local nanostructures with system composition has been investigated by FT-IR and XRD while the conductometric properties were probed by conventional AC complex impedance. Both pure components exhibit nano-segregation due to their amphiphilic nature but with only very low proton conductivities. However their mixtures, characterized by local organization of polar and apolar domains driven by acid-base interactions between HDEHP PO(4)H and BEEA NH groups, show enhanced structural order and proton conductivity.

Co nanoclusters were synthesized by an inverse-micelle chemical route. The magnetic and microstructural properties of the nanoparticles have been analyzed as a function of the surfactant (AOT and DEHP) and the drying method. Microstructural analysis has been performed by TEM and XANES; magnetic properties have been studied by hysteresis loops and zero-field cooling - field cooling (ZFC-FC) curves. TEM images show 2 to 4 nm sized particles spherical in shape. XANES measurements point out a significant presence of Co3O4 with metallic Co and some Co2+ bound to the surfactant. The presence of antiferromagnetic Co3O4 explains the magnetic transition observed at low T in both ZFC-FC measurements and hysteresis loops. Finally, the presence of magnetic interactions explains the bigger effective cluster size obtained from hysteresis loops fits (6-10 nm) compared to the sizes observed by TEM (2-4 nm).

The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a coreshell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The coreshell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant. (C) 2010 Elsevier B.V. All rights reserved.

Surfactant-coated ytterbium nanoparticles were produced by Nd:YAG laser ablation of a Yb bulk target immersed in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/ n -heptane micellar solution. In our experimental conditions, as highlighted by IR spectroscopy, AOT molecules are not decomposed by the intense laser pulses but play a pivotal role in the stabilisation of Yb nanoparticles. The formation of Yb nanoparticles in the liquid phase was monitored by UV–Vis spectroscopy whereas the Yb/AOT composites obtained by evaporation of the organic solvent were characterised by XPS and TEM. Data analysis consistently shows the presence of surfactant-coated, nearly spherical and non-interacting Yb nanoparticles of mean diameter of 3 nm. Moreover, the presence of bigger polycrystalline nanoparticles (about 30%) in coexistence with smaller mono crystalline ones indicates that, after the rapid formation of the pristine Yb nanoparticles from plume condensation, two processes effectively compete for their size distribution: nanoparticle agglomeration and surfactant adsorption.

Stable dispersions of surfactant-coated TiO2–Ag based nanoparticles in apolar medium have been prepared by performing sequentially the hydrolysis of titanium(IV) isopropoxide and the reduction of Ag? in the confined space of sodium bis(2-ethylhexyl)sulfosuccinate (NaAOT) reverse micelles. Depending on the sequence length, this novel procedure allowed the synthesis of semiconductor–metal nanoparticles, nominally indicated as TiO2/Ag, TiO2/Ag/TiO2, and TiO2/Ag/TiO2/ Ag, stabilized by a monolayer of oriented surfactant molecules. The structural characterization of these nanoparticles has been performed by High Resolution Transmission Electron Microscopy (HR-TEM), while optical properties were investigated by UV–Vis absorption and fluorescence spectroscopies. TEM investigation showed the presence of globular nanoparticles with an average diameter of about 10 nm composed by distinct amorphous TiO2 and crystalline Ag glued domains whose structure depends on the sequence length. UV–Vis absorption measurements highlighted the mutual metal–semiconductor influence on the TiO2 energy band gap and on the Ag plasmon resonance. Steady-state fluorescence spectra analysis allowed to reveal the strong inhibition of the electron–hole radiative recombination in the TiO2 domains due to the Ag and the appearance of a new emission band centred in the 484–545 nm range. Possible attributions of the involved electronic transition of this last emission are discussed.

The magnetic response of nanometer sized Co nanoparticles (NP) prepared using reverse micelle solutions are presented. The use of complementary structural and morphological probes (like transmission electron microscopy, high resolution electron microscopy, X-ray absorption spectroscopy) allowed to relate the magnetic properties to the size, morphology, composition and atomic structure of the nanoparticles. All data agree on the presence of a core–shell structure of NPs made of a metallic Co core surrounded by a thin Co-oxide layer. The core–shell microstructure of NPs affects its magnetic response mainly raising the anisotropy constant.

Chemically stable cobalt nanostructures have been prepared with Co(II) reduction in the confined space of cobalt bis(2-ethylhexyl)sulfosuccinate, Co(AOT)2, reverse micelles dispersed in n-heptane. The reaction was carried out by adding a solution of sodium borohydride in ethanol (1% weight) to a 0.2M micellar solution of Co(AOT)2 in n-heptane at a reductant to Co(II) molar ratio of 4. This procedure involves the rapid formation of surfactant-coated Co nanoparticles followed by their slow separation as nanostructures embedded in a sodium bis(2-ethylhexyl)sulfosuccinate matrix. The resulting composites, characterized by extended x-ray absorption fine structure and small-angle x-ray scattering, showed the presence of subnanometer sized cobalt nanoparticles aggregated together to form elongated structures coated by the surfactant molecules.

The confinement of D and L dimethyl tartrate in lecithin reverse micelles dispersed in cyclohexane has been investigated by FT-IR, polarimetry, electronic and vibrational circular dichroism (ECD and VCD), 1H NMR, and small-angle X-ray scattering (SAXS). Measurements have been performed at room temperature as a function of the solubilizate-to-surfactant molar ratio (R) at fixed lecithin concentration. The analysis of experimental data indicates that the dimethyl tartrate molecules are solubilized within reverse micelles in proximity to the surfactant head groups in the same way for the D and L forms. The encapsulation of dimethyl tatrate within lecithin reverse micelles involves changes in its H-bonds, from what is observed in the pure solid or in CCl4 solutions; this is a consequence of the establishment of specific solute-surfactant headgroup interactions and of confinement effects. In the 0or = Ror = 1.7 range, SAXS profiles of dimethyl tartrate/lecithin/ cyclohexane micellar solutions are well-described by a model of interacting polydisperse spherical micellar cores whose mean radius does not change appreciably with R (i.e., it changes from about 18 to 20 angstroms). 1H NMR diffusion measurements of both dimethyl tartrates and lecithin were rationalized in terms of collective translational motions of the entire micellar aggregate and of their molecular diffusion among clusters of reverse micelles. The association of optically active lecithin with D and L dimethyl tartrate leads to the formation of self-organized supramolecular aggregates whose interesting chiroptical features are evidenced by polarimetry and CD.

The state of acrylamide confined within dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and lecithin reversed micelles dispersed in CCl4 has been investigated by FTIR and H-1 NMR spectroscopy. Measurements have been performed at 25 degreesC as a function of the acrylamide-to-surfactant molar ratio (R) at a fixed surfactant concentration (0.1 mol kg(-1)). The analysis of experimental data, corroborated by the results of SAXS measurements, is consistent with the hypothesis that acrylamide is quite uniformly distributed among reversed micelles mainly located in proximity to the surfactant head-group region and that its presence induces significant unidimensional growth of micellar aggregates. Moreover, the confinement of acrylamide within reversed micelles involves some changes of the typical H-bonded structure of pure solid acrylamide attributable to the establishment of system-specific acrylamide/surfactant head group interactions. Preliminary experiments showed that, by exposure to X-rays, the polymerization of acrylamide can be induced in the confined space of dry AOT and lecithin reversed micelles. (C) 2004 Elsevier Inc. All rights reserved.