Pyridine-4-thiol as halogen-bond (HaB) acceptor: influence of the noncovalent interaction in its reactivity.

The study of pyridine-4-thiol as a halogen-bond (HaB) acceptor has allowed the isolation of its cocrystal with the HaB donor IC6F4I, namely, 1,2,4,5-tetrafluoro-3,6-diiodobenzene bis(pyridin-1-ium-4-ylsulfanide), C6F4I2·2C5H5NS (1), where the S atom is the HaB acceptor, while the pyridine position is blocked by the proton. Furthermore, the S atom acts a dual acceptor and also establishes an interaction with the pyridinium proton from an adjacent molecule. The presence of these interactions in 1 contributes to the stabilization of the zwitterionic form. This pre-organization seems to have an influence on the reactivity of the compound since when left in dichloromethane solution, an unusual activation of the C-Cl bond is observed that leads to the formation of the bis[(pyridin-1-ium-4-yl)sulfanyl]methane dication, while the Cl atoms are still present as chloride counter-ions, i.e. 4,4'-[methanediyldi(sulfanediyl)]dipyridinium dichloride, C11H12N2S22+·2Cl- (2). In the crystal structure of 2 it is observed that the S atom is now acting as the donor part of a chalcogenide bond with the chloride anions.

Nanostructure ITO and Get More of It. Better Performance at Lower Cost.

In this paper, we investigated how different growth conditions (i.e., temperature, growth time, and composition) allows for trading off cost (i.e., In content) and performance of nanostructured indium tin oxide (ITO) for biosensing applications. Next, we compared the behavior of these functionalized nanostructured surfaces obtained in different growth conditions between each other and with a standard thin film as a reference, observing improvements in effective detection area up to two orders of magnitude. This enhanced the biosensor's sensitivity, with higher detection level, better accuracy and higher reproducibility. Results show that below 150 °C, the growth of ITO over the substrate forms a homogenous layer without any kind of nanostructuration. In contrast, at temperatures higher than 150 °C, a two-phase temperature-dependent growth was observed. We concluded that (i) nanowire length grows exponentially with temperature (activation energy 356 meV) and leads to optimal conditions in terms of both electroactive surface area and sensitivity at around 300 °C, (ii) longer times of growth than 30 min lead to larger active areas and (iii) the In content in a nanostructured film can be reduced by 10%, obtaining performances equivalent to those found in commercial flat-film ITO electrodes. In summary, this work shows how to produce appropriate materials with optimized cost and performances for different applications in biosensing.

A low-cost and miniaturized potentiostat for sensing of biomolecular species such as TNF-α by electrochemical impedance spectroscopy.

Miniaturizing potentiostats, keeping their cost low and yet preserving full measurement characteristics (e.g. bandwidth, determination of capacitive/inductive contribution to sensor's impedance and parallel screening) is still an unresolved challenge in bioelectronics. In this work, the combination of simple analogue circuitry together with powerful microcontrollers and a digital filter implementation is presented as an alternative to complex and incomplete architectures reported in the literature. A low-cost acquisition electronic system fully integrated with a biosensors platform containing eight gold working microelectrodes and integrated reference and counter electrodes was developed and validated. The manufacturing cost of the prototype was kept below 300 USD. The performance of the proposed device was benchmarked against a commercial impedance analyzer through the electrochemical analysis of a highly sensitive biosensor for the detection of tumor necrosis factor α (TNF-α) within the randomly chosen range of 266pg/mL to 666ng/mL in physiological medium (PBS). A strong correlation between the outputs of both devices was found in a critical range of frequencies (1-10Hz), and several TNF-α cytokine concentrations were properly discriminated. These results are very promising for the development of low-cost, portable and miniaturized electrochemical systems for point-of-care and environmental diagnosis.

Photoresponsive ionic liquid crystals assembled via halogen bond: en route towards light-controllable ion transporters.

We demonstrate that halogen bonding (XB) can offer a novel approach for the construction of photoresponsive ionic liquid crystals. In particular, we assembled two new supramolecular complexes based on 1-ethyl-3-methylimidazolium iodides and azobenzene derivatives containing an iodotetrafluoro-benzene ring as XB donor, where the iodide anion acted as an XB acceptor. DSC and X-ray diffraction analyses revealed that the preferred stoichiometry between the XB donors and acceptors is 2 : 1, and that the iodide anions act as bidentate XB-acceptors, binding two azobenzene derivatives. Due to the high directionality of the XB, calamitic superanions are obtained, while the segregation occurring between the charged and uncharged parts of the molecules gives rise to a layered structure in the crystal lattice. Despite the fact that the starting materials are non-mesomorphic, the halogen-bonded supramolecular complexes exhibited monotropic lamellar liquid-crystalline phases over broad temperature ranges, as confirmed with polarized optical microscopy. Due to the presence of the azobenzene moieties, the LCs were photoresponsive, and a LC-to-isotropic phase transition could be obtained by irradiation with UV light. We envisage that the light-induced phase transition, in combination with the ionic nature of the LC, provides a route towards light-induced control over ion transport and conductance in these supramolecular complexes.

Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains.

Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabrication.

Efficient Light-Induced Phase Transitions in Halogen-Bonded Liquid Crystals.

Here, we present a new family of light-responsive, fluorinated supramolecular liquid crystals (LCs) showing efficient and reversible light-induced LC-to-isotropic phase transitions. Our materials design is based on fluorinated azobenzenes, where the fluorination serves to strengthen the noncovalent interaction with bond-accepting stilbazole molecules, and increase the lifetime of the cis-form of the azobenzene units. The halogen-bonded LCs were characterized by means of X-ray diffraction, hot-stage polarized optical microscopy, and differential scanning calorimetry. Simultaneous analysis of light-induced changes in birefringence, absorption, and optical scattering allowed us to estimate that <4% of the mesogenic units in the cis-form suffices to trigger the full LC-to-isotropic phase transition. We also report a light-induced and reversible crystal-to-isotropic phase transition, which has not been previously observed in supramolecular complexes. In addition to fundamental understanding of light-responsive supramolecular complexes, we foresee this study to be important in the development of bistable photonic devices and supramolecular actuators.

Evaluación clínica del bebé / Clinical assessment of baby

Este artículo propone un modelo multiaxial para la evaluación del bebé a partir de considerar los cinco ejes siguientes: la sobrecarga de la problemática parental en el funcionamiento psíquico del bebé y de sus síntomas (I); las características propias del niño que determinan la calidad de las relaciones interpersonales (II) que, a su vez, pueden dar lugar a trastornos del apego (III) y que están en la base de los trastornos del humor (IV) y del desarrollo del bebé (V). A lo largo del artículo el autor habla, de forma breve, cada uno de los ejes mencionados (AU)

This paper propose multiaxial model for the clinical assessment of the baby. This model considers the following axes: the overweight of the parental problematic on the baby's symptoms and psychological functioning (I); the particular characteristics of the baby that determine the quality of interpersonal relations (II) and can lead to attachment disorders (III) responsible for developmental and mood disorders in the baby (V-IV) (AU)