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Novel synthetic routes of large-pore magnetic mesoporous nanocomposites (SBA-15/Fe3O4) as potential multifunctional theranostic nanodevices

Z. Vargas-Osorio, M. A. González-Gómez, Y. Piñeiro, C. Vázquez-Vázquez, C. Rodríguez-Abreu, M. A. López-Quintela  and  J. Rivas

Journal of Materials Chemistry B, 5(47), pp. 9395-9404.2017

In this paper, novel magnetic silica nanocomposites were prepared by anchoring magnetite nanoparticles onto the outer surface of mesoporous SBA-15 silica; the magnetic nanoparticles were prepared by microemulsion and solvothermal methods, varying the synthesis conditions in order to control the final physicochemical, textural and magnetic properties. The morphology and mesostructure of the materials were characterized by X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), N2 adsorption–desorption, and Transmission and Scanning Electron Microscopy (TEM and SEM). Magnetic silica nanocomposites feature a two-dimensional hexagonal arrangement constituted by a homogeneous pore channel system with diameters between 13 and 18 nm and a Brunauer–Emmett–Teller (BET) surface area higher than 260 m2 g−1. The different morphologies of the samples are given by the presence of diverse magnetic nanoparticle arrangements covalently linked onto the outer surface of the mesoporous silica rods. This confers on them a superparamagnetic behaviour with a magnetic response between 50–80 emu g−1, even though the weight percent of magnetite present in the samples does not exceed 21.7%. In addition, the magnetic nanocomposites exhibit magnetic hyperthermia with moderate Specific Absorption Rate (SAR) values.
 

Theoretical study of non-Hammett vs. Hammett behaviour in the thermolysis and photolysis of arylchlorodiazirines

Xing-Liang Peng, Annapaola Migani, Quan-Song Li, Ze-Sheng Lia and Lluís Blancafort

Phys. Chem. Chem. Phys., 20, 1181-118, 2018

Arylchlorodiazirines (ACDA) are thermal and photochemical precursors of carbenes that form these molecules via nitrogen elimination. We have studied this reaction with multireference quantum chemical methods (CASSCF and CASPT2) for a series of ACDA derivatives with different substitution at the aromatic ring. The calculations explain the different reactivity trends found in the ground and excited state, with good correlation between the calculated barriers and the experimental reaction rates. The ground state mechanism can be described as a reverse cycloaddition with small charge transfer from the aromatic ring to the diazirine moiety. This is consistent with the lack of correlation between the Hammett s descriptors and the experimental rates. In contrast, the excited state reaction is the cleavage of a single C–N bond mediated by small barriers of 4–6 kcal mol-1. The reaction path goes through a conical intersection with the ground state, which facilitates radiationless decay and explains the disappearance of the transient absorption signal measured experimentally. This leads to a diazomethane intermediate that ultimately yields the carbene. Electronically, excitation to S1 is characterized initially by significant charge transfer from the phenyl ring to the diazirine. The charge transfer is reversed during the C–N cleavage reaction, and this explains the preferential stabilization of the excited-state minimum by polar solvents and electron-donating substituents. Therefore, our calculations reproduce and explain the relationship found experimentally between the Hammett s+ parameters and the life time of S1 (Y. L. Zhang, et al. J. Am. Chem. Soc., 2009, 131, 16652–16653).
 

A comparison between biostimulation and bioaugmentation in a solid treatment of anaerobic sludge: Drug content and microbial evaluation

G. Llorens-Blanch, E. Parladé, M. Martinez-Alonso, N. Gaju, G. Caminal and P.Blánquez

Waste Management, 2017

Emerging pollutants can reach the environment through the sludge of Wastewater Treatment Plants. In this work, the use of Trametes versicolor in biopiles at lab-scale was studied, evaluating its capacity to remove the most hydrophobic Pharmaceuticals and assessing the evolution of the biopiles microbial communities. The total removal of drugs at real concentrations from sewage sludge was assessed for non-inoculated and fungal inoculated biopiles, testing if the re-inoculation of the biopiles after 22?days of treatment would improve the removal yields. It was found that 2 out of the 15 initially detected pharmaceuticals were totally degraded after 22?days, and re-inoculated fungal biopiles achieved higher removal rates than non-re-inoculated fungal biopiles for single compounds and for all the drugs simultaneously: 66.45% and 49.18% re-inoculated and non-re-inoculated biopiles, respectively. Finally, the study of the bacterial and fungal communities revealed that fungal inoculated and non-inoculated biopiles evolved to similar communities adapted to the presence of those drugs.

 

The Atmospheric Oxidation of HONO by OH, Cl, and ClO Radicals

Josep M. Anglada and Albert Solé

J. Phys. Chem. A, 121 (51), pp 9698–9707, 2017

The atmospheric oxidation of nitrous acid by hydroxyl radical, chlorine atom, and chlorine monoxide radical was investigated with high-level theoretical methods. Nitrous acid has two conformers (cis and trans), and we found a reaction path for the oxidation of each of these conformers with the radicals considered. In all cases, the oxidation of the cis conformer is much more favorable than the oxidation of the trans conformer. Interestingly all transition states in these oxidation processes follow a proton-coupled electron-transfer mechanism. Our computed rate constant at 298 K for the reaction of cis-HONO + ·OH is 4.83 × 10–12 cm3 molecule–1 s–1, in excellent agreement with their experimental values (4.85 × 10–12 and 6.48 × 10–12 cm3 molecule–1 s–1). For the trans-HONO + ·OH reaction our calculated rate constant at 298 K is 9.05 × 10–18 cm3 molecule–1 s–1, and we computed an effective rate constant for the oxidation of the whole nitrous acid by hydroxyl radical of 1.81 × 10–12 cm3 molecule–1 s–1. For the oxidation of nitrous acid by chlorine atom we predict greater rate constants (7.38 × 10–11, 3.33 × 10–15, and 2.76 × 10–11 cm3 molecule–1 s–1, for the cis and trans conformers and for the whole HONO), these results suggesting that this reaction should contribute to the tropospheric oxidation of nitrous acid, especially in marine boundary areas, and to the formation of tropospheric ozone. For the oxidation of nitrous acid by chlorine monoxide we predict rate constants roughly 6 orders of magnitude smaller than the oxidation by chlorine atom, and therefore we consider that this process should play a minor role in the troposphere.
 

Phenylalanine and derivatives as versatile low-molecular-weight gelators: design, structure and tailored function

Tanmay Das, Marleen Haering, Debasish Haldar and David Díaz Díaz

Biomater. Sci., 2017

Phenylalanine (Phe) is an essential amino acid classified as neutral and nonpolar due to the hydrophobic nature of the benzyl side chain. In the field of materials science, the chemical modification of phenylalanine at C or N terminus has enabled a large number of low-molecular-weight gelators over the past decade. Thus, many physical (or supramolecular) softgel materials have been fabricated by self-assembling Phe-derived building blocks, which can be programmed with atomic level information and modification. The process of self-assembly and gelation must balance the parameters that influence the solubility as well as the contrasting forces that dictate epitaxial growth into entangled fibrillar aggregates. Gelator–gelator and solvent–gelator interactions are known to be highly important for the gelation process, and the non-covalent nature of these interactions provide physical gels with important properties such as reversible phase transitions and responsiveness towards external stimuli. Among other applications, these gels have been used for drug delivery, as extracellular matrix for tissue engineering, for oil spills recovery, removal of dyes, extraction of heavy metals or pollutants, and for the detection of explosives. In this tutorial review, we highlight the advances in the design, synthesis and applications of supramolecular gels made of Phe and derivatives.

 

Multiplex environmental pollutant analysis using an array biosensor coated with chimeric hapten-dextran-lipase constructs

Sonia Herranz, Marzia Marciello, María -P. Marco, José L. Garcia-Fierro, José M. Guisan and María C. Moreno-Bondi

Sensors and Actuators B: Chemical 257, 256-262, 2018

This paper reports the development of a novel strategy for the easy immobilization of low molecular weight haptens to microarray platforms by coating with modified lipase molecules. The chimers consist of a dextran network covalently coupled to bacterial thermoalkalophilic lipase (BTL2). The relative high surface hydrophobicity of lipase allows easy immobilization of the conjugates onto glass planar waveguides previously modified with 1,1,1,3,3,3-hexamethyldisilazane, via nonspecific hydrophobic interactions, while the dextran layer provides a three-dimensional network that can be easily modified with different functional groups for further hapten immobilization on the glass substrate. The conjugates have been applied to the development of microarray biosensors for the simultaneous detection of three water pollutants namely, atrazine (ATR), a triazine pesticide, enrofloxacin (ENRO), a fluoroquinolone antimicrobial, and the hepatotoxin microcystin LR (MCLR). In an alternative approach, the chimeric hapten-dextran-BTL2 constructs were synthesized, purified and further immobilized on the hydrophobic transducer surface through their hydrophobic faces (Janus character). Detection of the three model targets was based in a competitive immunoassay format. A combination of detection and tracer antibodies was optimized to avoid significant cross-reactivity. Evanescent wave excitation was used to excite the fluorescent immunocomplexes formed on the planar waveguide and the identity of the target analyte was encoded by its location in the detection platform. The developed microarray allows the simultaneous detection of the target pollutants with IC50 values, of 4.4 ± 0.7, 75 ± 9, 18 ± 4 ng L-1 for ATR, ENRO and MCLR, respectively and relative standard deviations (RSDs) lower than 15%. Waveguide functionalization using the dextran-BTL2 chimers is rapid, simple and allows the development of highly sensitive microarrays that can be easily applied to the multiplexed detection of pollutants in environmental samples.

 

Cationic gemini surfactants containing an O-substituted spacer and hydroxyethyl moiety in the polar heads: Self-assembly, biodegradability and aquatic toxicity

Olga Kaczerewska, Bogumil Brycki, Isabel Ribosa, Francesc Comelles and M. Teresa Garcia

Journal of Industrial and Engineering Chemistry 59,141-148, 2018

Micellization and some ecological properties of new cationic gemini surfactants with oxygen-substituted spacer and hydroxyethyl groups connected to the polar heads have been studied. The incorporation of a hydroxyethyl group in the polar head favors self-aggregation whereas the presence of the oxygen in the spacer increases critical micelle concentration. Surfactants investigated are not biodegradable due to their toxic effect on microorganisms responsible for biodegradation. Aquatic toxicity increases with the hydrophobic chain and decreases by increasing the hydrophilicity of spacer and polar heads. New gemini surfactants are less toxic to the aquatic environment than monomeric surfactants and non-oxygen-containing gemini surfactants.

 

Reversible Self-Assembly of Water-Soluble Gold(I) Complexes

Elisabet Aguiló,  Artur J. Moro, Raquel Gavara, Ignacio Alfonso , Yolanda Pérez , Francesco Zaccaria, Célia Fonseca Guerra, Marc Malfois, Clara Baucells, Montserrat Ferrer, João Carlos Lima , and Laura Rodríguez

Inorg. Chem., 2018, 57 (3), pp 1017–1028

 The reaction of the gold polymers containing bipyridyl and terpyridyl units, [Au(C≡CC15H10N3)]n and [Au(C≡CC10H7N2)]n, with the water-soluble phosphines 1,3,5-triaza-7-phosphatricyclo[3.3.1.13.7]decane and 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane gives rise to the formation of four gold(I) alkynyl complexes that self-assemble in water (H2O) and dimethyl sulfoxide (DMSO), through different intermolecular interactions, with an impact on the observed luminescence displayed by the supramolecular assemblies. A detailed analysis carried out by NMR studies performed in different DMSO/deuterated H2O mixtures indicates the presence of two different assembly modes in the aggregates: (i) chain assemblies, which are based mainly on aurophilic interactions, and (ii) stacked assemblies, which are based on Au···π and π···π interactions. These different supramolecular environments can also be detected by their intrinsic optical properties (differences in absorption and emission spectra) and are predicted by the changes in the relative binding energy from density functional theory calculations carried out in DMSO and H2O. Small-angle X-ray scattering (SAXS) experiments performed in the same mixture of solvents are in agreement with the formation of aggregates in all cases. The aromatic units chosen, bipyridine and terpyridine, allow the use of external stimuli to reversibly change the aggregation state of the supramolecular assemblies. Interaction with the Zn2+ cation is observed to disassemble the aggregates, while encapsulating agents competing for Zn2+ complexation revert the process to the aggregation stage, as verified by SAXS and NMR. The adaptive nature of the supramolecular assemblies to the metal-ion content is accompanied by significant changes in the absorption and emission spectra, signaling the aggregation state and also the content on Zn2+.

 

Self-Aggregation and Emulsifying Properties of Methyl Ester Sulfonate Surfactants

Amel Asselah, Aurora Pinazo, Amalia Mezei, Lourdes Pérez and Amel Tazerouti

Journal of Surfactants and Detergents, 2017

Methyl ester sulfonate (MES) anionic surfactants made from natural resources are of particular interest as sustainable surfactants. They offer good physicochemical properties for applications as detergents and emulsifiers. The liquid crystal structures of MES surfactants synthesized in a previous work were determined by polarizing optical microscopy (POM) and small-angle X-ray scattering (SAXS). The emulsifying activity for each surfactant was also measured, and the stability of emulsions was estimated and compared to that induced by sodium dodecyl sulfate (SDS). The POM micrographs showed the presence of birefringent textures. Several factors, including temperature and hydration, influenced the stability of the phases and their structure. SAXS confirmed the structure of the phases formed by dry and hydrated ф-MES surfactants at 25 °C, giving the position of peaks corresponding to the ratio 1:2:3 and revealing the phase transitions of lamellar to double lamellar or the reverse. Also, the Bragg distance (d) decreased with an increase in chain length from 13 to 17 carbon atoms and an increase in the area per molecule of surfactant. The geometric packing parameters were also determined, and suggest that surfactants are tilted. The stability of surfactant emulsions is around 60%, which is comparable to that of SDS. The micrographs show that the emulsions formed are O/W, and an increase in chain length gives rise to a decrease in the size of the emulsion droplets. These results are confirmed by the values of hydrophilic-lipophilic balance (HLB) which reveals the hydrophilic nature of these surfactants.

 

Effect of fatliquoring on leather comfort. Part III: Moisture absorption-desorption of leather

Manich, A.M., Barenys, J., Martinez, L., Lloria, J., Carilla, J. and Marsal, A

Journal of the American Leather Chemists Association,  112, 10, 347-355, 2017

The comfort of tanned hide/skin is an added value, which is decisive for the choice of leather in articles for footwear or clothing, compared to other alternatives whose design excludes this component. This comfort is related to the capacity of absorption and desorption of moisture and with the physical, mechanical and organoleptic characteristics of the leather. After tanning, fatliquoring and retanning are the operations that more intensively modify the characteristics of leather articles. This work is a continuation of two previous ones that have studied the influence of fatliquoring on softness and compressibility of leather and on grain and corium quality of leather assessed by ball bursting and tearing tests. In this case, the effect of fatliquoring on moisture absorption-desorption characteristics of leather is studied. The experimental work has been carried out in the pilot plant of Trumpler Espanola S. A. and the moisture absorption-desorption tests in the Laboratory of Thermal Analysis and Calorimetry of the 1QAC. The behavior of non-fatliquored leather and that of leather fatliquored with a combination of sulphited triglycerides of colza oil and fatty polymer (TCSi/PGR) or fatliquored separately with their components TCSi and PGR, or with phosphoric ester ESF or sulphited fish oil Psi has been determined. The determination of the size of the moisture absorbing monolayer (Xm), the binding energy constants of the monolayer C and the multilayer K, the maximum absorption capacity at saturation XI and the hysteresis (Hyst.) between absorption and desorption, enabled us to classify the different fatliquoring agents according to stage (crust-blue, finished-red) by applying factorial analysis (see following graph). Finishing is the factor that best explains this behavior. Finishing decreases the size of the monolayer and increases the binding energy constants. Fatliquoring decreases the maximum absorption capacity and hysteresis, partially affecting the reduction of the monolayer size.
 


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