pH Switchable Water Dispersed Photocatalytic Nanoparticles

Photogeneration of Reactive Oxygen Species (ROS) finds applications in fields as different as nanomedicine, art preservation, air and water depollution and surface decontamination. Here we present photocatalytic nanoparticles (NP) that are active only at acidic pH while they do not show relevant ROS photo-generation at neutral pH. This dual responsivity (to light and pH) is achieved by stabilizing the surface of TiO₂ NP with a specific organic shell during the synthesis and it is peculiar of the achieved core shell-structure, as demonstrated by comparison with commercial photocatalytic TiO₂ NP. For the investigation of the photocatalytic activity, we developed two methods that allow real time detection of the process preventing any kind of artifact arising from post-treatments and delayed analysis. The reversibility of the pH response was also demonstrated as well as the selective photo-killing of cancer cells at acidic pH.     

Fast chromatographic determination of the bile salt critical micellar concentration

In a line of research focused on the design, synthesis and development of new bile acid-based compounds, the physico-chemical profile of the molecules must be thoroughly explored and analyzed. In this scenario, a fast and reliable information on the critical micellar concentration (CMC) of specific compounds through a profitable chromatographic parameter can be of aid to rationally direct the synthesis of new molecular entities, mainly during the early stages of the drug-discovery process. The derived ‘chromatographic hydrophobicity index’ (CHI), usually employed for a fast access to the log P/log D value of physico-chemically diverse compounds and obtained via RP-gradient elution, was for the first time engaged in the bile acid field. Accordingly, 14 unconjugated bile acids harboured with a different number, position and orientation of hydroxy groups, as well as other substituents onto the steroidal backbone and side chain, were selected to build up a calibration curve. Such a collection of compounds was rationally assembled in order to manage an almost continuous range of CMC values (spanning the spectrophotometrically obtained CMCs between 5 and 25 mM). A high degree of correlation between CMC and CHI values was obtained (R ² and cross-validated R _xv² of the pCMC vs CHI plot equal to 0.975 and 0.966, respectively). A selected new subset of five confidential research bile acids with experimental CMCs in the range 6–19 mM was finally recruited to validate the proposed method. The high statistical quality of the established mathematical model turned out into a very appreciable predictive power.     

Tracing the biological origin of animal glues used in paintings through mitochondrial DNA analysis

We report the development of a suitable protocol for the identification of the biological origin of binding media on tiny samples from ancient paintings, by exploitation of the high specificity and high sensitivity offered by the state-of-the art DNA analysis. In particular, our aim was to molecularly characterize mitochondrial regions of the animal species traditionally employed for obtaining glues. The model has been developed using aged painting models and then tested to analyze the organic components in samples from the polychrome terracotta Madonna of Citerna by Donatello (1415-1420), where, by GC-MS and FTIR spectroscopy, animal glues and siccative oils were identified. The results obtained are good in terms of both sensibility and specificity of the method. First of all, it was possible to confirm that Donatello used animal glue for the preparation of the painted layers of the Madonna of Citerna and, specifically, glue derived from Bos taurus. Data obtained from sequencing confirm that each sample contains animal glue, revealing that it was mostly prepared from two common European taurine lineages called T2 and T3. There is one remarkable exception represented by one sample which falls into a surviving lineage of the now extinct European aurochs.     

Glucose‐ and Cellulose‐Derived Ni/C‐SO3H Catalysts for Liquid Phase Phenol Hydrodeoxygenation

Sulfonated carbons were explored as functionalized supports for Ni nanoparticles to hydrodeoxygenate (HDO) phenol. Both hexadecane and water were used as solvents. The dual‐functional Ni catalysts supported on sulfonated carbon (Ni/C‐SO₃H) showed high rates for phenol hydrodeoxygenation in liquid hexadecane, but not in water. Glucose and cellulose were precursors to the carbon supports. Changes in the carbons resulting from sulfonation of the carbons resulted in variations of carbon sheet structures, morphologies and the surface concentrations of acid sites. While the C‐SO₃H supports were active for cyclohexanol dehydration in hexadecane and water, Ni/C‐SO₃H only catalysed the reduction of phenol to cyclohexanol in water. The state of 3–5 nm grafted Ni particles was analysed by in situ X‐ray absorption spectroscopy. The results show that the metallic Ni was rapidly formed in situ without detectable leaching to the aqueous phase, suggesting that just the acid functions on Ni/C‐SO₃H are inhibited in the presence of water. Using in situ IR spectroscopy, it was shown that even in hexadecane, phenol HDO is limited by the dehydration step. Thus, phenol HDO catalysis was further improved by physically admixing C‐SO₃H with the Ni/C‐SO₃H catalyst to balance the two catalytic functions. The minimum addition of 7 wt % C‐SO₃H to the most active of the Ni/C‐SO₃H catalysts enabled nearly quantitative conversion of phenol and the highest selectivity (90 %) towards cyclohexane in 6 h, at temperatures as low as 473 K, suggesting that the proximity to Ni limits the acid properties of the support.     

Synthesis by MW-assisted direct arylation,side-arms driven self-assembly and functional properties of 9,10-dithienylanthracene orthogonal materials

We report a new class of multifunctional 9,10-dithienylanthracene-based materials having an anthracene π-core functionalized at the 9,10 positions with thienyl side-arms of different size and type of substitution. MW-assisted double direct arylation reaction is employed for the first time to synthesize the target molecules in one-step, organometallic free conditions, in only 5 min and yields up to 80% rather than by a multi-step Stille coupling taken as conventional reference approach. DFT calculations reveal a molecular conformation characterized by the thienyl rings orthogonal to the anthracene core. Nevertheless, despite the non-coplanar structure, all compounds exhibited highly crystalline cast films emitting blue light, with an extraordinary variability in morphology and hole mobility up to 8×10⁻³ cm² V⁻¹ s⁻¹.     

A fullerene-based dyad for organic photovoltaic cells

We describe the synthesis and the photophysical properties of a fullerene–azothiophene dyad, as well as the photovoltaic performance of cells incorporating the dyad and the surface morphology of the device active layer. The results have been compared with those obtained on the blend, in equimolar ratio, between the azothiophene dye and a fulleropyrrolidine. This revealed a pivotal role played by the morphology on both the photophysical behaviour and the device performance. While scanning force microscopy studies for the dyad exhibited fairly smooth surfaces, in the case of the blend they displayed a micrometre-scale phase segregation between the two components. We suggest that, in the latter case, the lack of photo-induced electron transfer evidenced by the photophysical study, and the relevant reduction of the cell performance (up to more than one order of magnitude with respect to the dyad), could be ascribed to the different morphology. Because of the strong optical absorption in the visible region, the dyad-based solar cells gave notable results if compared with those reported in the literature for other donor–acceptor linked systems. A power-conversion efficiency of 0.37% under 80-mWcm^-2 white-light illumination has been achieved by tuning the thickness of the dyad film, though the fullerene–azothiophene is not yet optimised in terms of photo-induced electron transfer. PACS 81.05.Tp; 73.50.Pz; 71.35.Gg; 72.20.Jv     

Phytochemistry and Biological Activity of Medicinal Plants in Wound Healing: An Overview of Current Research

Wound healing is a complicated process, and the effective management of wounds is a major challenge. Natural herbal remedies have now become fundamental for the management of skin disorders and the treatment of skin infections due to the side effects of modern medicine and lower price for herbal products. The aim of the present study is to summarize the most recent in vitro, in vivo, and clinical studies on major herbal preparations, their phytochemical constituents, and new formulations for wound management. Research reveals that several herbal medicaments have marked activity in the management of wounds and that this activity is ascribed to flavonoids, alkaloids, saponins, and phenolic compounds. These phytochemicals can act at different stages of the process by means of various mechanisms, including anti-inflammatory, antimicrobial, antioxidant, collagen synthesis stimulating, cell proliferation, and angiogenic effects. The application of natural compounds using nanotechnology systems may provide significant improvement in the efficacy of wound treatments. Increasing the clinical use of these therapies would require safety assessment in clinical trials.     

Thermochemistry of Lewis adducts of BH3 and nucleophilic substitution of triethylamine on NH3BH3 in tetrahydrofuran

The thermochemistry of the formation of Lewis base adducts of BH(3) in tetrahydrofuran (THF) solution and the gas phase and the kinetics of substitution on ammonia borane by triethylamine are reported. The dative bond energy of Lewis adducts were predicted using density functional theory at the B3LYP/DZVP2 and B3LYP/6-311+G** levels and correlated ab initio molecular orbital theories, including MP2, G3(MP2), and G3(MP2)B3LYP, and compared with available experimental data and accurate CCSD(T)/CBS theory results. The analysis showed that the G3 methods using either the MP2 or the B3LYP geometries reproduce the benchmark results usually to within ~1 kcal/mol. Energies calculated at the MP2/aug-cc-pVTZ level for geometries optimized at the B3LYP/DZVP2 or B3LYP/6-311+G** levels give dative bond energies 2-4 kcal/mol larger than benchmark values. The enthalpies for forming adducts in THF were determined by calorimetry and compared with the calculated energies for the gas phase reaction: THFBH(3) + L → LBH(3) + THF. The formation of NH(3)BH(3) in THF was observed to yield significantly more heat than gas phase dative bond energies predict, consistent with strong solvation of NH(3)BH(3). Substitution of NEt(3) on NH(3)BH(3) is an equilibrium process in THF solution (K ≈ 0.2 at 25 °C). The reaction obeys a reversible bimolecular kinetic rate law with the Arrhenius parameters: log A = 14.7 ± 1.1 and E(a) = 28.1 ± 1.5 kcal/mol. Simulation of the mechanism using the SM8 continuum solvation model shows the reaction most likely proceeds primarily by a classical S(N)2 mechanism.     

Charge transport mechanism in pressed pellets of polymer proton conductors

The charge transport inside some polymer proton conductors, prepared by chemical doping of poly(propargyl alcohol) and poly(p-diethynylbenzene) with acids, or by electrochemical polymerisation of thionaphtheneindole, has been investigated. All the systems, studied as powder pressed pellets between two gold electrodes, show very low electrical conductivity due to electrons motion. In presence of environmental humidity the conductivity increases dramatically as a consequence of proton migration through the material. A mechanism for the charge transport through the materials, based on the proton conductivity of a thin layer of acid aqueous solution adherent to the polymer grains, has been hypothesised. Since the investigated doped polymers show a reversible conductivity variation as a function of water content, they are proposed as materials for humidity sensor construction.