Two‐Photon Absorption Enhancement by the Inclusion of a Tropone Ring in Distorted Nanographene Ribbons

A new family of distorted ribbon‐shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two‐photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven‐membered‐ring‐containing nanographene presenting a tropone moiety at the edge, its full‐carbon analogue, and a purely hexagonal one. We have found that the TPA cross‐sections and the electrochemical band gaps of the seven‐membered‐ring‐containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non‐linear optical properties of those ribbons.     

Estimation of Reactivity Ratios in the Copolymerization of Styrene and VeoVa‐10

The styrene and vinyl neodecanoate copolymerization system shows a strong tendency to form two separate homopolymers. In order to improve the feeding strategies and hence the copolymer uniformity, it is necessary to know the reactivity ratios between these monomers. The error‐in‐variables‐method (EVM) is the most recommended mathematical procedure for estimating these parameters. Experiments on free‐radical copolymerization in solution in sealed ampoules are carried out to provide data for the conversion (via gravimetry) and fractional monomer compositions (via Fourier transform mid‐infrared (mid‐FT‐IR) spectroscopy). These data allow estimation of the reactivity ratios. EVM appropriately takes into account the experimental errors in the data and allows determination of the reactivity ratio values by the Mayo–Lewis model (r₁ = 28.60 and r₂ = 1.23). The convergence and robustness of the method decrease considerably with a larger discrepancy between the reactivity values.     

Preparation and Characterization of Electrodes Modified with Pyrrole Surfactant,Multiwalled Carbon Nanotubes and Metallophthalocyanines for the Electrochemical Detection of Thiols

Our aim was to prepare hybrid electrodes active towards the electrooxidation of thiols by the co‐immobilization of native carbon nanotubes (CNTs) and cobalt phthalocyanine (CoPc) from aqueous solutions. This strategy was adopted to avoid the oxidation of CNTs that can induce a modification of their exceptional properties. To do so, a hydrosoluble pyrrole surfactant was used to get homogeneous aqueous dispersions of CNTs and CoPc and to trap both materials on the electrode via the electropolymerization of the pyrrole surfactant. The hybrid electrodes exhibit a good electrocatalytic activity towards the oxidation of L ‐cysteine and glutathione. Their performances in terms of limit of detection (0.01 mM) are compatible with the detection of these thiols in biological samples.     

Deracemization By Simultaneous Bio‐oxidative Kinetic Resolution and Stereoinversion

Deracemization, that is, the transformation of a racemate into a single product enantiomer with theoretically 100 % conversion and 100 % ee, is an appealing but also challenging option for asymmetric synthesis. Herein a novel chemo‐enzymatic deracemization concept by a cascade is described: the pathway involves two enantioselective oxidation steps and one non‐stereoselective reduction step, enabling stereoinversion and a simultaneous kinetic resolution. The concept was exemplified for the transformation of rac‐benzylisoquinolines to optically pure (S)‐berbines. The racemic substrates were transformed to optically pure products (ee>97 %) with up to 98 % conversion and up to 88 % yield of isolated product.     

Catalytic Enantioselective Quick Route to Aldol‐Tethered 1,6‐ and 1,7‐Enynes from ω‐Unsaturated Aldehydes

An effective asymmetric route to functionalized 1,6‐ and 1,7‐enynes has been developed based on a direct cross‐aldol reaction between ω‐unsaturated aldehydes and propargylic aldehydes (α,β‐ynals) promoted by combined α,α‐dialkylprolinol ether/Brønsted acid catalysis. This synergistic activation strategy is key to accessing the corresponding aldol adducts with high stereoselectivity, both enantio‐ and diastereoselectivity. The aldol reaction also proceeds well with propargylic ketones (α,β‐ynones) thus enabling a stereocontrolled access to the corresponding tertiary alcohols. The utility of these adducts, which are difficult to prepare through standard methodology, is demonstrated by their transformation into trisubstituted bicyclic enones using standard Pauson–Khand conditions.     

Hierarchically Organized Silica–Titania Monoliths Prepared under Purely Aqueous Conditions

Hierarchically organized silica–titania monoliths were synthesized under purely aqueous conditions by applying a new ethylene glycol‐modified single‐source precursor, such as 3‐[3‐{tris(2‐hydroxyethoxy)silyl}propyl]acetylacetone coordinated to a titanium center. The influence of the silicon‐ and titanium‐containing single‐source precursor, the novel glycolated organofunctional silane, and the addition of tetrakis(2‐hydroxyethyl)orthosilicate on the formation of the final porous network was investigated by SEM, TEM, nitrogen sorption, and SAXS/WAXS. In situ SAXS measurements were performed to obtain insight into the development of the mesoporous network during sol–gel transition. IR‐ATR, UV/Vis, XPS, and XAFS measurements showed that up to a Si/Ti ratio of 35:1, well‐dispersed titanium centers in a macro‐/mesoporous SiO₂ network with a specific surface area of up to 582 m² g^?1 were obtained. An increase in Ti content resulted in a decrease in specific surface area and a loss of the cellular character of the macroporous network. With a 1:1 Si/Ti ratio, silica–titania powders with circa 100 m² g^?1 and anatase domains within the SiO₂ matrix were obtained.     

Phosphathiahelicenes: Synthesis and Uses in Enantioselective Gold Catalysis

Enantiomerically pure thiahelicenes displaying a terminal phosphole unit and a stereogenic phosphorus center have been prepared by oxidative photocyclization of a diaryl‐olefin precursor. Starting from one of these phosphathiahelicene oxides, the corresponding trivalent phosphine–Au^I complex is obtained with complete diastereoselectivity. It affords a new, excellent precatalyst for the enantioselective cycloisomerization of N‐tethered enynes (up to 96 % ee).     

Thermo-sensitive chitosan–cellulose derivative hydrogels: swelling behaviour and morphologic studies

Hydrogels are three-dimensional, hydrophilic, polymer networks that are able to imbibe large amounts of water or biological fluids, while maintaining their dimensional stability. The polymer binding might be achieved by chemical or physical interactions. Physical crosslinking of a polymer to form its hydrogel, might be accomplished either by casting-solvent evaporation (SC) method or by freeze–thaw (FT) technique. The physical hydrogels, especially the ones based on natural biopolymers, like polysaccharides, are being widely used in industry and medicine due to their favourable properties: biocompatibility; biodegradability; low toxicity and eco-friendly characteristics. Polysaccharides, like chitosan (CH) and (hydroxypropyl)methyl cellulose (HPMC) have gained great attention due to its stimuli sensitive properties: pH and temperature responsiveness, respectively. Thus, within this work we have developed physically crosslinked CH:HPMC hydrogel films, using both SC and FT techniques. The attained CH:HPMC membranes were evaluated in terms of their swelling, thermal (low critical solution temperature—LCST), structural (attenuated total reflectance Fourier transform infrared spectroscopy) and morphological (scanning electron microscopy and atomic force microscopy) properties. According to these results, the developed membranes exhibit a good miscibility between the two component biopolymers. Moreover, the CH:HPMC membranes exhibit a high swelling capacity (SW_FT = 1,172 and SW_SC = 7,323), a low surface roughness (Sq = 5.6–9.5 nm) and an elevated LCST (LCST = 85.2–87.5 °C). The stimuli sensitive behaviour makes hydrogels appealing for the design of smart devices applicable in a variety of technological fields. In our particular case, we envisage the application of such materials as active substances (moisturisers, antiperspirants and scents) delivers, into textile substrates in a controlled manner.     

Surface-enhanced Raman spectroscopy of blood plasma and serum using Ag and Au nanoparticles: a systematic study

Surface-enhanced Raman spectroscopy (SERS) is a good candidate for the development of fast and easy-to-use diagnostic tools, possibly used on biofluids in point-of-care or screening tests. In particular, label-free SERS spectra of blood serum and plasma, two biofluids widely used in diagnostics, could be used as a metabolic fingerprinting approach for biomarker discovery. This study aims at a systematic evaluation of SERS spectra of blood serum and plasma, using various Ag and Au aqueous colloids, as SERS substrates, in combination with three excitation lasers of different wavelengths, ranging from the visible to the near-infrared. The analysis of the SERS spectra collected from 20 healthy subjects under a variety of experimental conditions revealed that intense and repeatable spectra are quickly obtained only if proteins are filtered out from samples, and an excitation in the near-infrared is used in combination with Ag colloids. Moreover, common plasma anticoagulants such as EDTA and citrate are found to interfere with SERS spectra; accordingly, filtered serum or heparin plasma are the samples of choice, having identical SERS spectra. Most bands observed in SERS spectra of these biofluids are assigned to uric acid, a metabolite whose blood concentration depends on factors such as sex, age, therapeutic treatments, and various pathological conditions, suggesting that, even when the right experimental conditions are chosen, great care must be taken in designing studies with the purpose of developing diagnostic tests.     

Surfactant protein C metabolism in human infants and adult patients by stable isotope tracer and mass spectrometry

Surfactant protein C (SP-C) is deemed as the surfactant protein most specifically expressed in type II alveolar epithelial cells and plays an important role in surfactant function. SP-C turnover in humans and its meaning in the clinical context have never been approached. In this study, we used mass spectrometry to investigate SP-C turnover in humans. We studied four infants and eight adults requiring mechanical ventilation. All patients had no lung disease. Patients received a 24-h continuous infusion of ¹³C-leucine as precursor of SP-C, and serial tracheal aspirates and plasma samples were obtained every 6 h till 48 h. SP-C was isolated from tracheal aspirates by sorbent-phase chromatography. ¹³C-leucine SP-C enrichment could be successfully measured in three infant and in four adult samples by using mass spectrometry coupled with a gas chromatographer. Median SP-C fractional synthesis rate, secretion time, and peak time were 15.7 (14.1–27.5) %/day, 6.0 (4.7–11.5) h, and 24 (20–27) h. In conclusion, this study shows that it is feasible to accurately determine SP-C turnover in humans by stable isotopes.