Molecular Insight into the Effect of Polymer Topology on Wettability of Block Copolymers: The Case of Amphiphilic Polyurethanes.

The microstructure design of multiblock copolymers is essential for achieving desired interfacial properties in submerged applications. Two major design factors are the chemical composition and polymer topology. Despite a clear relationship between chemical composition and wetting, the effect of polymer topology (i.e., linear vs cross-linked polymers) is not very clear. Thus, in this study, we shed light on the molecular origins of polymer topology on the wetting behavior. To this end, we synthesized linear and three-dimensional (3D) cross-linked network topologies of poly(ethylene glycol) (PEG)-modified polycarbonate polyurethanes with the same amount of hydrophilic PEG groups on the surface (confirmed by X-ray photoelectron spectroscopy (XPS)) and studied the wetting mechanisms through water contact angle (WCA), atomic force microscopy (AFM), and molecular dynamics (MD) simulations. The linear topology exhibited superhydrophilic behavior, while the WCA of the cross-linked polymer was around 50°. AFM analysis (performed on dry and wet samples) suggests that PEG migration toward the interface is the dominant factor. MD simulations confirm the AFM results and unravel the mechanisms: the higher flexibility of PEG in linear topology results in a greater PEG migration to the interface and formation of a thicker interfacial layer (i.e., twice as thick as the cross-linked polymers). Accordingly, water diffusion into the interfacial layer was greater in the case of the linear polymer, leading to better screening of the underneath hydrophobic (polycarbonate) segments.

Chrono-colorimetric sensor array for detection and discrimination of halide ions using an all-in-one plasmonic sensor element.

Most nanoparticle based colorimetric sensor array utilize several sensor elements and static response for discrimination of target analytes. This approach can be complicated and costly to synthesize or functionalize different nanoparticles for providing wide color variation. Herein, triangular silver nanoparticles (TSNPs) were used to develop a colorimetric sensor array by time-dimension responses. The principle of this sensor array is based on the diverse etching process of TSNPs in the presence of three halide ions, including bromide (Br-), iodide (I-) and chloride (Cl-). Various etchings of TSNPs induced color changes at different reaction time intervals, which produced a colorimetric pattern for each ion. Therefore, using time dependent etching responses of TSNPs as a single sensing component can produce a wide color variation which can be distinguished by naked eyes. The colorimetric responses of TSNPs upon the addition of different concentrations of halide ions have been analyzed by PLS regression (PLS-R) and PLS discriminant analysis (PLS-DA). The analytical figures of merit confirmed that the developed chrono-colorimetric TSNPs -based sensor array is successful in both the discrimination and quantitative detection of halide ions. At the final step, the three halide ions were accurately determined in a real water sample, which verified the potential of the developed sensor in a real sample.

Enhanced Photocatalytic Properties of Restacked Unilamellar [SrTa2O7]2- Nanosheets of Aurivillius Phase Layered Perovskites.

In the present work, unilamellar [SrTa2O7]2- perovskite nanosheets with variable lateral dimensions were synthesized via a high-yield, three-step liquid exfoliation route from layered Bi2SrTa2O9. The photocatalytic activity of the parent and exfoliated layered perovskites was evaluated for the photocatalytic dye degradation of Rhodamine B under UV light (254 nm) and reduction of water to H2 under the full solar spectrum. A comparative study of the photocatalytic behavior of unilamellar [SrTa2O7]2- perovskite nanosheets and parent layered structure showed a significant improvement in both hydrogen evolution (98.20 vs 3 µmol g-1) and Rhodamine B degradation time (180 vs 30 min), with the restacked nanosheets. The exfoliation of layered perovskites not only increases their specific surface area, providing more active sites, but also reduces the recombination probability of electrons and holes due to their unilamellar structure and reduced charge transport pathways. The synthesis and preparation of strong acid solids such as [SrTa2O7]2- perovskite nanosheets can be a promising approach for effective adsorption of pollutants with cationic nature and more efficient electron transfer between the dye and catalyst. Finally, the photocatalytic characteristics of the restacked unilamellar [SrTa2O7]2- nanosheets remained unchanged after three successive cycles of recycling-reusing.

Er doped layered perovskites with dual mode luminescent behavior and tunable multicolor upconversion emission.

Er3+ doped BST nanoparticles with Aurivillius layered structure are synthesized through common solid-state method. Photoluminescence spectroscopy has shown that these oxides are capable of emitting light under UV (366 nm) and IR (980 nm) source. The effect of Er3+ to Yb3+ concentration ratio on upconversion emission are investigated and possible upconversion and energy transfer mechanisms are suggested based on the number of photons participating in UC process. Shift in the upconversion emission from green to red region is visualized by CIE chromaticity diagram. The superiority of coexistence of stoke and anti-stoke emission in a single host lattice with a single activator ion, besides to tunability of UC luminescence only by controlling sensitizer/activator ratio are very interesting features which can be used to produce dual mode multicolor luminescent ink with high security level against forgery.

Attachment styles as predictors of empathy in nursing students.

Previous studies have traced a relationship between the attachment styles of nurses working as in healthcare teams and their empathy which is an essential characteristic required of people concerned with managing relationships, supporting social events, and improving the of nurse-patient relationships. Since determining the effective variables in the quality of nurse-patient relationships in clinical settings is of paramount importance, current investigation is an effort to examine the relationship between attachment styles and empathy in nursing students. 260 university students (male = 130 and female = 130) were chosen as the sample of the study based upon specific inclusion criteria. All participants completed the Attachment Style Questionnaire (ASQ) and the Interpersonal Reactivity Index (IRI). Data was collected and analyzed using Pearson correlation coefficient and regression analysis with SPSS (v.18). The results showed that secure and insecure attachment styles have significant positive and negative correlation with empathy respectively. Based on the results of regression analysis, it was shown that secure attachment style is predicting 53% of the variance empathy variable, whereas insecure attachment styles are explaining up to 76% of the variance empathy variable collectively. The increase of attention to instructions that focus on empathetic relationships with patients and that are based upon the secure attachment style can result in positive changes in the area of nurse-patient relations and in increasing attention to medical ethics. Findings are consistent with prediction derived from attachment theory and add to our understanding of relationship between attachment styles with empathy in nursing students. The meaning and limitations of this study and suggestions for further research are also discussed.