Metal Organic Framework-235 (MOF-235) Modified Carbon Paste Electrode for Catechol Determination in Water

MOF-235 is presented as an orange powder, with crystals of the octahedral formation. It was already used as adsorbent to remove different compounds from water; however, no attempts have been published about the exploration of the MOF-235 application as electrochemical sensor for organic compounds yet. MOF-235 was synthetized and after that, it was characterized by SEM, XRD and FTIR. Graphite electrodes (GEs) were modified with different MOF-235 ratio (5 %, 7 %, 10 %, 12 % and 14 %) and these modified GEs were characterized by cyclic voltammetry (CV) measurements in order to determine the effect of MOF-235 concentration on the current response. Results indicated that, a significant improvement on the current response was attained at MOF-235(10 %)/GE respect to unmodified GE. This behavior is related to the pore structure and multiple active sites on the MOF surface. The performance of the MOF-235(10 %)/GE as electrochemical sensor for detecting catechol was assessed by differential pulse voltammetry (DPV). Catechol detection response of MOF-based sensor provided a detection limit of about 12.79 μmol L⁻¹ with a correlation coefficient (R²) of about 0.9928 ranging from 12 to 514 μmol L⁻¹. Finally, MOF-235(10 %)/GE was used to determine catechol in real water matrixes.     

Nanostructure and dielectric properties of a twist-bend nematic liquid crystal mixture

We present freeze-fracture transmission electron microscopy (FF-TEM), dielectric spectroscopy and electro-optic measurements on a dimeric liquid crystal mixture, which previously was proposed to form the twist-bend nematic (N_tb) phase. Our FF-TEM studies provide a direct image of a 10.5 nm periodic structure, consistent with the expected nanoscale, heliconical twist-bend modulation of the molecular orientation. Dielectric measurements in the 100 Hz to 10 MHz range reveal three nearly Debye-type dispersion processes in the nematic and the twist-bend phase. Low frequency 8 V/µm electric fields applied on planar cells cause the optical-scale stripe texture (another characteristic feature of the N_tb phase) to disappear. Higher (>16 V/µm) fields gradually realign the heliconical axis along the electric field; it relaxes back after the field removal.     

Chlorhexidine/losartan ionic pair binding and its nanoprecipitation: physico-chemical characterisation and antimicrobial activity

Chlorhexidine is a widely used, di-cationic, broad-spectrum antimicrobial agent and losartan is a well-known, anionic-specific antagonist of AT1 renin–angiotensin receptor that acts as an anti-hypertensive agent. The combination of these molecules gives a chlorhexidine di-losartanate (ClxLos₂) hydrophobic ion pair that spontaneously aggregates into nanoparticles (NPs). This work investigated the formation of ClxLos₂ NPs using the analysis of the solid state by fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy and in aqueous environment by calorimetric, zeta potential and dynamic light scattering titrations. Furthermore, to demonstrate the potential antimicrobial activity of ClxLos₂, in vitro antibacterial tests were conducted against Staphylococcus aureus (ATCC 27664), Streptococcus viridans (ATCC 11563) and Enterococcus faecalis (ATCC 14508). Based on these studies, it is proposed that ClxLos₂ could be used for controlled drug release based on ionic dissociation during dilution, thereby avoiding the use of any solid matrix.     

Synthesis and characterization of cellulose acetate from cellophane industry residues. Application as acetaminophen controlled-release membranes

Journal of Thermal Analysis and Calorimetry - Cellophane film production generates cellulosic residues from scraps, edges, and low-quality films. In this work, cellophane was used as a raw material...     

Calcium polyphosphate coacervates: effects of thermal treatment

The addition of calcium chloride eletrolyte to sodium polyphosphate solutions lead to Calcium polyphosphate coacervates. The effects of a thermal treatment were investigated with the objective to increase the relative stability of the obtained material. Thermogravimetry analysis indicates that coacervates became less hydrophilic and more thermally stable after the thermal treatment. Crystallization was identified through differential scanning calorimetry and X-ray diffraction. Morphological changes were observed after the thermal treatment by scanning electron microscopy. N₂ adsorption?Cdesorption isotherms suggest that both materials, thermally treated or not, display type IV isotherms, low superficial area and mesoporous structure. Stability experiments in solutions at different pH values show that the thermally treated calcium polyphosphate is relatively more stable than the non-treated coacervate.     

Green solvent approach for printable large deformation thermoplastic elastomer based piezoresistive sensors and their suitability for biomedical applications

Composites based on biocompatible thermoplastic elastomer styrene‐ethylene/butylene‐styrene (SEBS) as matrix and multi‐walled carbon nanotubes (MWCNT) as nanofillers show excellent mechanical and piezoresistive properties from low to large deformations. The MWCNT/SEBS composites have been prepared following a green solvent approach, to extend their range of applicability to biomedical applications. The obtained composites with 2, 4, and 5 wt % MWCNT content provide suitable piezoresistive response up to 80% deformation with a piezoresistive sensibility near 2.7, depending on the applied strain and MWCNT content. Composite sensors were also developed by spray and screen printing and integrated with an electronic data acquisition system with RF communication. The possibility to accurately control the composites properties and performance by varying MWCNT content, viscosity, and mechanical properties of the polymer matrix, shows the large potential of the system for the development of large deformation printable piezoresistive sensors. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2092–2103