Photo-cured epoxy networks reinforced with TiO2 in-situ generated by means of non-hydrolytic sol–gel process

Suspensions of titania nanoparticles in benzyl alcohol were synthesised from TiCl₄ by means of non-hydrolytic sol–gel (NHSG) process. The stable suspensions were mixed with an aliphatic epoxy resin and subsequently photo-polymerised in the presence of a cationic photo-initiator to produce transparent composite films. The presence of titania didn’t influence significantly the polymerisation rate, while a progressive decrease in the maximum value of epoxy groups conversion was observed by increasing the titania content. Gel content analysis demonstrated that all organic species (benzyl alcohol and corresponding by-products) were covalently linked to the epoxy network, suggesting that both ‘active chain end’ and ‘activated monomer’ mechanisms were active during the propagation step in the cationic ring-opening polymerisation. The presence of titania increased significantly both glass transition temperature and modulus (in the rubbery region) confirming the reinforcing and stiffening effect due to both the presence of inorganic nanofillers and, most importantly, a higher cross-linking density of the composite material with respect to the pristine epoxy matrix. Nano-indentation and scratch tests also showed a systematic increase of hardness and scratch resistance by increasing the filler content.     

Sonochemical Synthesis and Structural Characterization and DFT Calculations of a Novel Nano Flower Pb(II) Coordination Compound [Pb(phen)2(4-abs)2]n

Nano-structures of a new coordination polymer of divalent Pb with the ligands 1,10-phenanthroline (phen) and 4-aminobenzene sulfonic acid (4-abs), [Pb(phen)₂(4-abs)₂]_n (1), were synthesized by a sonochemical method that produced a coordination polymer of nanometer size. The new nano-structure was characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy and elemental analysis. Compound 1 was structurally characterized by single crystal X-ray diffraction and showed that the coordination number of the Pb(II) ions is six; i.e. (PbN₄O₂). Compound 1 also has a stereochemically active lone pair of electrons and a hemi-directed coordination sphere. The chains interact with each other through π–π stacking to create a 3D framework. The structure of 1 was optimized by density functional theory calculations. The calculated structural parameters and IR spectra of 1 are consistent with the crystal structure.     

Transition from core-shell to Janus chemical configuration for bimetallic nanoparticles

In order to determine the possibilities to control the chemical configuration of bimetallic nanoparticles, we have considered CuAg nanoparticles synthesized by a physical route as a model in this study. The synthesis was made by pulsed laser deposition under ultra-high vacuum conditions, via a sequential deposition procedure. We show that the temperature of the substrate and the absolute quantity of Ag in a particle are the main parameters that drive the chemical configuration. To explain the transition from a core-shell configuration to a Janus configuration as a function of Ag quantity, we have conducted density-functional theory calculations and atomistic molecular dynamics simulations to investigate the stability of this system. The results are presented together with the experimental observations.     

Nanostructure of buried interface layers in TiO₂ anatase thin films grown on LaAlO₃ and SrTiO₃ substrates

TiO(2) anatase thin films grown by pulsed laser deposition are investigated by high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy. The analyses provide evidence of a peculiar growth mode of anatase on LaAlO(3) and SrTiO(3) characterized by the formation of an epitaxial layer at the film/substrate interface, due to cationic diffusion from the substrate into the film region. Pure TiO(2) anatase growth occurs in both specimens above a critical thickness of about 20 nm. The microstructural and chemical characterization of the samples is presented and discussed in the framework of oxide interface engineering.     

Colloidal synthesis and characterization of tetrapod-shaped magnetic nanocrystals

Tetrapod-shaped maghemite nanocrystals are synthesized by manipulating the decomposition of iron pentacarbonyl in a ternary surfactant mixture under mild thermal conditions. Adjustment of the reaction parameters allows for the systematic tuning of both the width and the length of the tetrapod arms, which grow preferentially along the 111 easy axis direction. Such degree of control leads to modulation of the magnetic behavior of the nanocrystals, which evolves systematically as their surface magnetization phase and shape anisotropy are progressively increased.     

Phantom nanoparticles as probes of biomolecular interactions

A new light-scattering-based method to detect molecular interactions at the surface of low-refractive-index nanoparticles was recently proposed. Water-dispersed nanoparticles functionalized with receptors typical of immature bacteria cell walls were used to study the activity of the antibiotic vancomycin. This method subtly depends on the specific properties of the nanoparticles. Here we discuss, by comparative experiments and through theoretical evaluation, the effects of size, refractive index, electric charge, and dilution on the reliability and accuracy of the method. Quite surprisingly, perfect index matching and minimal size (i.e., maximum surface), which is almost attained in one of the colloids here employed, do not represent the ideal conditions. Rather, we show that a nanoparticle radius of 100 nm and a refractive index slightly below that of water yields the best signal/background amplitude. We also show that repulsive interactions can lead to artifacts in the adsorption isotherm, thus indicating that electrostatic stabilization should be kept at a minimum. The close agreement between the interaction strengths, as measured with two different nanoparticle systems, testifies to the reliability of the method.     

The importance of turbulence during condensation in a horizontal circular minichannel

Three-dimensional simulations of condensation of refrigerant R134a in a horizontal minichannel are presented. Mass fluxes ranging from 50 kg m^?2 s^?1 up to 1000 kg m^?2 s^?1 are considered in a circular minichannel of 1 mm diameter, and uniform wall and vapour–liquid interface temperatures are imposed as boundary conditions. The Volume of Fluid (VOF) method is used to track the vapour–liquid interface; the effects of interfacial shear stress, gravity and surface tension are taken into account. The influence of turbulence in the condensate film is analysed and compared against the assumption of laminar condensate flow by employing different computational approaches and validating the results against experimental data. Under the assumption of laminar condensate flow, experimental heat transfer coefficient values at low mass fluxes can be predicted, but the computed heat transfer coefficient is found to be almost independent of mass flux and vapour quality. Only when turbulence in the condensate film is taken into account does the numerical model capture the influence of mass flux that is observed in the experimental measurements.     

Colors of transparent submicron suspensions on approaching the Rayleigh regime

The features of scattered and transmitted light by dilute suspensions of transparent submicron particles are investigated both in the spectral and in the perceived colorimetric domains, as a function of effective particle diameter D, particle-host refractive-index mismatch m, and scattering angle θ. Our results show that the wavelength λ-dependence of the scattering and extinction cross sections remains quite similar well beyond the Rayleigh regime up to particle sizes of a few hundreds nm, but only for specific scattering angles that depend on D and m, and tend to 90° on approaching the Rayleigh regime. Close to this limit (D/λ<1), a simple criterion that relates the perceived scattering color at θ=90° and the ratio of the sample extinction coefficients at two properly selected wavelengths is demonstrated. A comparison between computed and measured data is presented.     

Fruit consumption determinants among young adults in Italy: A case study

Knowing fruit consumption determinants is essential to improve interventions aiming at stimulating fruit intake in young population. This paper analyses young adults attitude and behaviour towards fruit consumption. We performed a survey on Italian university students (n = 692) to explain fruit consumption behaviour and determinants based on the theory of planned behaviour (TPB). The importance of determinants was evaluated with multi-group structural equation modelling (SEM). The TPB variables (attitudes, subjective norms and perceptions of control) explain 72% of intention to consume at least 200 g/d of fruit, and 15% of fruit consumption. These figures increase, respectively, to 88% and 20% if we include habits as a mediator. In this case, intention becomes relatively less important in explaining fruit consumption. This suggests that stronger habits result in less conscious behaviour, and that interventions to increase fruit consumption should improve fruit availability and develop individuals' ability to overcome barriers. Multi-group analysis has shown that low fruit consumers' intention is influenced by attitude, supporting the effectiveness of education campaigns for this target. Intention is the main fruit consumption predictor for those doing regular physical activity, which points to possible synergies of integrated public interventions to improve health behaviours.     

Development of a tensiometric model for surface energy characterization of raw coffee beans

The aim of this work is to investigate surface energy properties of various raw coffee bean species (tensiometric approach) and to develop a tensiometric marker based on contact angle measurements of Fomblin HC/25 drops, a perfluoropolyether phosphate (PFPE), to distinguish different species of raw coffee beans. To create measurable contact angles, raw coffee beans were pre-selected according to the endosperm surface morphology (smooth surface) and affixed to a specifically developed support. The tensiometric method was developed using contact angle method (CA) and calculation models such as Owens, Wendt and Kaelble. Results show the tensiometric properties of raw coffee beans expressed as surface free energy (SFE) and the capability of the marker to distinguish species. This work could create interesting prospects for quality control at the product source, storage conditions, and for industrial process evaluation of roasting and drying.