In situ growth of well-dispersed CdS nanocrystals in semiconducting polymers

A straight synthetic route to fabricate hybrid nanocomposite films of well-dispersed CdS nanocrystals (NCs) in poly[2-methoxy-5-(2''-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) is reported. A soluble cadmium complex [Cd(SBz)₂]₂·MI, obtained by incorporating a Lewis base (1-methylimidazole, MI) on the cadmium bis(benzyl)thiol, is used as starting reagent in an in situ thermolytic process. CdS NCs with spherical shape nucleate and grow well below 200°C in a relatively short time (30 min). Photoluminescence spectroscopy measurements performed on CdS/MEH-PPV nanocomposites show that CdS photoluminescence peaks are totally quenched inside MEH-PPV, if compared to CdS/PMMA nanocomposites, as expected due to overlapping of the polymer absorption and CdS emission spectra. The CdS NCs are well-dispersed in size and homogeneously distributed within MEH-PPV matrix as proved by transmission electron microscopy. Nanocomposites with different precursor/polymer weight ratios were prepared in the range from 1:4 to 4:1. Highly dense materials, without NCs clustering, were obtained for a weight/weight ratio of 2:3 between precursor and polymer, making these nanocomposites particularly suitable for optoelectronic and solar energy conversion applications.     

Laser irradiation of ZnO:Al/Ag/ZnO:Al multilayers for electrical isolation in thin film photovoltaics

Laser irradiation of ZnO:Al/Ag/ZnO:Al transparent contacts is investigated for segmentation purposes. The quality of the irradiated areas has been experimentally evaluated by separation resistance measurements, and the results are complemented with a thermal model used for numerical simulations of the laser process. The presence of the Ag interlayer plays two key effects on the laser scribing process by increasing the maximum temperature reached in the structure and accelerating the cool down process. These evidences can promote the use of ultra-thin ZnO:Al/Ag/ZnO:Al electrode in large-area products, such as for solar modules.     

Photoactive sol–gel hybrid coatings from modified fluorocarbon polymers and amorphous titania

A series of organic–inorganic hybrid coatings was prepared through sol–gel chemistry by combining silanized chlorotrifluoroethylene-vinylether (FEVE) binders with tetraalkoxy silicon and titania sols under acidic conditions. The best compositions to obtain highly transparent and homogeneous coatings after thermal curing were determined. All the hybrid coatings easily pass the MEK test and show high scratch hardness. The atomic force microscopy (AFM) shows the formation of very smooth surfaces (R_rms routinely <1 nm) without clear phase separation phenomena. The typical size of the “objects” which may be individuated is in the range of 40–80 nm. Wettability through contact angle measurements shows the formation of moderately hydrophobic surfaces with a low contact angle hysteresis (~20°) which is a further indication of very smooth, homogeneous and chemically stable surfaces. After irradiation with UV-B light only hybrid coatings containing titania phases show a significant switch to a superhydrophilic behavior with a contact angle against H₂O down to 6°, which is only partially recovered after storage of the material in the dark. Titania based hybrid coatings also showed a fast and efficient UV-induced discoloration of the resazurin ink. The formulation of the coatings with photostabilizers belonging to the class of radical scavengers and UV absorbers does not change the photoinduced surface properties while eliminating the yellowing of the coating after UV exposure. It is concluded that titania-fluoropolymer hybrid coating show photoactivity and UV-induced superhydrophylicity mostly through ionic mechanisms, which could be beneficial to develop high durability and self-cleaning protective coatings.     

Synthesis and Structure Determination of the Adducts of Dibenzo[a,l]pyrene Diol Epoxides and Deoxyadenosine or Deoxyguanosine

Abstract

(±)?Syn?dibenzo[a,l]pyrene diol epoxide (DB[a,l]PDE) and (±)?anti?DB[a,l]PDE were reacted with deoxyadenosine (dA) or deoxyguanosine (dG) in dimethylformamide at 100 °C for 30 min. The crude products were purified by reverse phase HPLC under gradient and isocratic conditions. The structure of each adduct was assigned by 1D and 2D NMR spectra and by fast atom bombardment mass spectrometry. Five adducts were isolated from the reaction of (±)?syn?DB[a,l]PDE and dA: syn?DB[a,l]PDE?N⁶dA?1, syn?DB[a,l]PDE?N⁶dA?2, syn?DB[a,l]PDE?N⁶dA?3, syn?DB[a,l]PDE?N⁶dA?4 and syn?DB[a,l]PDE?N7Ade. Four adducts were isolated from the reaction of (±)?anti?DB[a,l]PDE and dA: anti?DB[a,l]PDE?N⁶dA?1, anti?DB[a,l]PDE?N⁶dA?2, anti?DB[a,l]PDE?N⁶dA?3 and anti?DB[a,l]PDE?N⁶dA?4. Two adducts were isolated from the reaction of (±)?syn?DB[a,l]PDE and dG: (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N²dG and (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N7Gua. Two adducts were isolated from the reaction of (±)?anti?DB[a,l]PDE and dG: (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N²dG and (±)?11,12,13?trihydroxy?tetrahydroDB[a,l]P?14?N7Gua.     

Wollastonite/hydroxyapatite scaffolds with improved mechanical,bioactive and biodegradable properties for bone tissue engineering

Wollastonite/hydroxyapatite composite scaffolds are proposed as bone graft. An investigation on scaffold with varying reinforcing wollastonite content fabricated by polymeric sponge replica is reported. The composition, sintering behavior, morphology, porosity and mechanical strength were characterized. All the scaffolds had a highly porous well-interconnected structure. A significant increase in mechanical strength is achieved by adding a 50% wollastonite phase. The most mechanically resistant (50/50) wollastonite/hydroxyapatite scaffolds were soaked in both simulated body fluid (SBF) and Tris–HCl solution in order to assess bioactivity and biodegradability. A carbo-hydroxyapatite layer formed on their surfaces when immersed in SBF. The biodegradability tests reveals that the composite scaffold shows a higher degradation rate compared to pure hydroxyapatite used as comparison. These results demonstrate that the incorporation of a 50% of wollastonite phase in hydroxyapatite matrix is effective in improving the strength and the bioactive and biodegradable properties of the porous scaffolds.     

Electrochemical anticorrosion performance evaluation of Al2O3 coatings deposited by MOCVD on an industrial brass substrate

Alumina (Al₂O₃) coatings of different thickness were deposited on OT59 brass substrate (BS) using the metal organic chemical vapour deposition (MOCVD) technique to evaluate the corrosion performance by EIS measurements. The used precursor was dimethyl-aluminium-isopropoxide. Electrochemical characterizations of the deposited films were performed in a standard very aggressive acidic solution (aerated 1N H₂SO₄ at 25 °C up to 168 h of immersion time) by means of direct current method (Tafel curves) and electrochemical impedance spectroscopy (EIS). The Rutherford backscattering spectroscopy (RBS) indicated that the films are very pure with the correct Al₂O₃ stoichiometry, while the IR absorption spectra showed that the films did not contain any OH groups. The surface film morphology was investigated by atomic force microscopy (AFM) and displayed a globular texture. The films were very smooth, with a maximum root mean square roughness, for example, of 14 nm for a 0.96 μm thick coating. The EIS data confirmed, as expected, that a 2.40 μm Al₂O₃ layer ensures the best corrosion protection after 168 h of immersion in the very acidic environment used.     

Cycling stability of a hybrid activated carbon//poly(3-methylthiophene) supercapacitor with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid as electrolyte

A long cycle-life, high-voltage supercapacitor featuring an activated carbon//poly(3-methylthiophene) hybrid configuration with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid, a solvent-free green electrolyte, was developed. The cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60 °C over 16,000 galvanostatic charge-discharge cycles at 10 mA cm⁻² in the 1.5 and 3.6 V voltage range. The reported average and maximum specific energy and power, specific capacitance and capacity, equivalent series resistance and coulombic efficiency over cycling demonstrate the long-term viability of this ionic liquid as green electrolyte for high-voltage hybrid supercapacitors.     

Accurate determination of hexanal in beef bouillons by headspace solid‐phase microextraction gas‐chromatography mass‐spectrometry

Lipid oxidation has great impact on the quality of food products through flavor and taste deterioration, reduction in nutritive value, and potential toxicity of the oxidized food components. Flavor and taste deterioration can be easily perceived and it represents one of the major causes of consumer complaints in the food industry. The deterioration of sensory properties is due to the decomposition products of hydroperoxides that easily isomerize and degrade into volatile compounds. Volatile products are responsible for flavor and taste deterioration. In this study, we present the development of the solid‐phase microextraction gas chromatography‐mass spectrometry (SPME‐GC‐MS) technique to quantify low amounts (μg/g range) of secondary oxidation products, i.e. hexanal. The optimization of SPME parameters is a difficult task because of the possibility of further formation of volatile products during analysis. Different parameters such as type of fiber, exposure time of the fiber to the sample headspace and the optimal temperature of absorption have also been investigated. The complete validation of the method was achieved by the determination of linearity, limits of detection and quantification and repeatability. We demonstrated that the SPME method is a valuable tool for the quantification of low amounts of secondary oxidation products such as hexanal. Therefore, this technique can be used to detect early formation of volatiles.     

Design and Characterization of Myristoylated and Non-Myristoylated Peptides Effective against Candida spp. Clinical Isolates

The increasing resistance of fungi to antibiotics is a severe challenge in public health, and newly effective drugs are required. Promising potential medications are lipopeptides, linear antimicrobial peptides (AMPs) conjugated to a lipid tail, usually at the N-terminus. In this paper, we investigated the in vitro and in vivo antifungal activity of three short myristoylated and non-myristoylated peptides derived from a mutant of the AMP Chionodracine. We determined their interaction with anionic and zwitterionic membrane-mimicking vesicles and their structure during this interaction. We then investigated their cytotoxic and hemolytic activity against mammalian cells. Lipidated peptides showed a broad spectrum of activity against a relevant panel of pathogen fungi belonging to Candida spp., including the multidrug-resistant C. auris. The antifungal activity was also observed vs. biofilms of C. albicans, C. tropicalis, and C. auris. Finally, a pilot efficacy study was conducted on the in vivo model consisting of Galleria mellonella larvae. Treatment with the most-promising myristoylated peptide was effective in counteracting the infection from C. auris and C. albicans and the death of the larvae. Therefore, this myristoylated peptide is a potential candidate to develop antifungal agents against human fungal pathogens.