Fluorometric and isothermal titration calorimetric studies on binding interaction of a telechelic polymer with sodium alkyl sulfates of varying chain length

Steady-state fluorescence measurements and isothermal titration calorimetric experiments have been performed to study the interaction between a telechelic polymer, pyrene-end-capped poly(ethylene oxide) (PYPY), and sodium alkyl sulfate surfactants having decyl, dodecyl, and tetradecyl hydrocarbon tails. Fluorometric results suggest polymer-surfactant interaction in the very low range of polymer concentrations. The relative variation in the excimer to monomer pyrene emission intensities with varying surfactant concentration reveals that initial addition of surfactant favors intramolecular preassociation until the surfactant molecules start binding with the ethylene oxide (EO) chain. With the growing number of surfactant aggregates along the EO chain, the association becomes hindered due to the polyelectrolyte effect. The results from microcalorimetric titrations in the low concentration range of PYPY solution (approximately 10(-6) M) with alkyl sulfates suggest two kinds of surfactant-polymer interactions, one with the polymer hydrophobic end groups and the other with the ethylene oxide backbone. The overall polymer-surfactant interaction starts at a much lower surfactant concentration for the hydrophobically modified polymers compared to that in the case of unsubstituted poly(ethylene oxide) homopolymer. From the experiments critical aggregation concentration values and the second critical concentration where free micelles start forming have been determined. An endeavor has been made to unveil the mechanism underlying the corresponding associations of the surfactants with the polymer.     

Indium trichloride catalyzed sp C–H bond functionalization of 2-alkyl azaarenes under microwave irradiation

Microwave promoted indium trichloride (10 mol %) catalyzed sp³ C–H bond functionalization of 2-alkyl azaarenes 1 or 4 has been observed to construct C–C bond either with but-2-ene-1,4-diones 2 or (E)-3-(2-oxo-2-phenylethylidene)indolin-2-one (6) giving access to 2-((quinolin-2-yl)methyl)butane-1,4-diones 3, 2-((pyridin-2-yl)methyl)butane-1,4-diones 5, or 3-(quinolin-2-yl)propan-2-yl)indolin-2-ones 7 in good yields using 1,4-dioxane as solvent.     

Efficient approach to produce multi‐functional copolymers for effective DNA binding

Norbornene‐derived copolymer with side‐chain phosphonic acid and cationic motifs (NORP‐PHOS‐CAT copolymer) are synthesized using ring opening metathesis polymerization method. All the monomers and polymers are characterized very carefully using nuclear magnetic resonance, MASS, Fourier transform infrared spectroscopy, and gel permeation chromatography technique. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and scanning electron microscope techniques are employed to confirm the anchoring of Fe₃O₄ particles to the NORP‐PHOS‐CAT copolymer. Formation of nano‐aggregates from NORP‐PHOS‐CAT copolymer is first observed in dynamic light scattering, and later, it is confirmed as nano‐spheres by scanning electron microscope and transmission electron microscopy studies. Zeta‐potential values of nano‐spheres suggest that the cationic motifs are on the surface. The encapsulation of anionic dye methyl orange to the nanocarrier is analyzed through UV–Vis spectroscopy in aqueous medium. DNA binding nature of NORP‐PHOS‐CAT‐Fe copolymer is confirmed through the circular dichroism measurement and UV–Vis spectroscopy. To the best of our knowledge, this is the first report where the norbornene‐derived copolymers that are elegantly synthesized with both magnetic as well as cationic nature to demonstrate the effective encapsulation of dye into the nano‐spheres followed by its release. Copyright © 2016 John Wiley & Sons, Ltd.     

Random overlap structures: properties and applications to spin glasses

Random overlap structures (ROSt’s) are random elements on the space of probability measures on the unit ball of a Hilbert space, where two measures are identified if they differ by an isometry. In spin glasses, they arise as natural limits of Gibbs measures under the appropriate algebra of functions. We prove that the so called ‘cavity mapping’ on the space of ROSt’s is continuous, leading to a proof of the stochastic stability conjecture for the limiting Gibbs measures of a large class of spin glass models. Similar arguments yield the proofs of a number of other properties of ROSt’s that may be useful in future attempts at proving the ultrametricity conjecture. Lastly, assuming that the ultrametricity conjecture holds, the setup yields a constructive proof of the Parisi formula for the free energy of the Sherrington–Kirkpatrick model by making rigorous a heuristic of Aizenman, Sims and Starr.     

Anharmonic Oscillator Driven by Additive Ornstein–Uhlenbeck Noise

We present an analytical study of a nonlinear oscillator subject to an additive Ornstein–Uhlenbeck noise. Known results are mainly perturbative and are restricted to the large dissipation limit (obtained by neglecting the inertial term) or to a quasi-white noise (i.e., a noise with vanishingly small correlation time). Here, in contrast, we study the small dissipation case (we retain the inertial term) and consider a noise with finite correlation time. Our analysis is non perturbative and based on a recursive adiabatic elimination scheme a reduced effective Langevin dynamics for the slow action variable is obtained after averaging out the fast angular variable. In the conservative case, we show that the physical observables grow algebraically with time and calculate the associated anomalous scaling exponents and generalized diffusion constants. In the case of small dissipation, we derive an analytic expression of the stationary probability distribution function (PDF) which differs from the canonical Boltzmann–Gibbs distribution. Our results are in excellent agreement with numerical simulations.     

Enhancement of silicon solar cell performances due to light trapping by colloidal metal nanoparticles

Photovoltaics is the most promising technology for the future of green energy production. To fully realize the potential use of photovoltaic technology, low manufacturing cost and high working photoconversion efficiency must be obtained. Light trapping by metal nanoparticles is an attractive strategy in thin film as well as in bulk silicon solar cells aimed to confine light within the active layer to promote the photon absorption and therefore achieving higher efficiency. In this paper, we tested the deposition of silver and gold nanoparticles on bulk silicon solar cells by colloidal technique in order to enhance their photovoltaic conversion efficiency by means of Plasmonic Light Scattering by metal nanoparticles. The feasible Plasmonic Light Scattering related enhancement was examined using spectral response and I–V measurements. Relative increases of the total delivered power under simulated solar irradiation were observed for cells both with and without antireflection coating using silver and gold nanoparticles.     

Evolution of surface morphology of NiO thin films under swift heavy ion irradiation

NiO nanoparticle thin films grown on Si substrates were irradiated by 107 MeV Ag⁸⁺ ions. The films were characterized by glancing angle X-ray diffraction and atomic force microscopy. Ag ion irradiation was found to influence the shape and size of the nanoparticles. The pristine NiO film consisted of uniform size (∼100 nm along major axis and ∼55 nm along minor axis) elliptical particles, which changed to also of uniform size (∼63 nm) circular shape particles on irradiation at a fluence of 3 × 10¹³ ions cm⁻². Comparison of XRD line width analysis and AFM data revealed that the particles in the pristine films are single crystalline, which turn to polycrystalline on irradiation with 107 MeV Ag ions.     

Dipolar relaxation within the protein matrix of the green fluorescent protein: a red edge excitation shift study

The fluorophore in green fluorescent protein (GFP) is localized in a highly constrained environment, protected from the bulk solvent by the barrel-shaped protein matrix. We have used the wavelength-selective fluorescence approach (red edge excitation shift, REES) to monitor solvent (environment) dynamics around the fluorophore in enhanced green fluorescent protein (EGFP) under various conditions. Our results show that EGFP displays REES in buffer and glycerol, i.e., the fluorescence emission maxima exhibit a progressive shift toward the red edge, as the excitation wavelength is shifted toward the red edge of the absorption spectrum. Interestingly, EGFP displays REES when incorporated in reverse micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), independent of the hydration state. We interpret the observed REES to the constrained environment experienced by the EGFP fluorophore in the rigid protein matrix, rather than to the dynamics of the bulk solvent. These results are supported by the temperature dependence of REES and characteristic wavelength-dependent changes in fluorescence anisotropy.     

Potential Precursor Alternatives to the Pyrophoric Trimethylaluminium for the Atomic Layer Deposition of Aluminium Oxide

New precursor chemistries for the atomic layer deposition (ALD) of aluminium oxide are reported as potential alternatives to the pyrophoric trimethylaluminium (TMA) which is to date a widely used Al precursor. Combining the high reactivity of aluminium alkyls employing the 3-(dimethylamino)propyl (DMP) ligand with thermally stable amide ligands yielded three new heteroleptic, non-pyrophoric compounds [Al(NMe₂)₂(DMP)] ( 2 ), [Al(NEt₂)₂(DMP)] ( 3 , BDEADA) and [Al(NiPr₂)₂(DMP)] ( 4 ), which combine the properties of both ligand systems. The compounds were synthesized and thoroughly chemically characterized, showing the intramolecular stabilization of the DMP ligand as well as only reactive Al−C and Al−N bonds, which are the key factors for the thermal stability accompanied by a sufficient reactivity, both being crucial for ALD precursors. Upon rational variation of the amide alkyl chains, tunable and high evaporation rates accompanied by thermal stability were found, as revealed by thermal evaluation. In addition, a new and promising plasma enhanced (PE)ALD process using BDEADA and oxygen plasma in a wide temperature range from 60 to 220 °C is reported and compared to that of a modified variation of the TMA, namely [AlMe₂(DMP)] (DMAD). The resulting Al₂O₃ layers are of high density, smooth, uniform, and of high purity. The applicability of the Al₂O₃ films as effective gas barrier layers (GBLs) was successfully demonstrated, considering that coating on polyethylene terephthalate (PET) substrates yielded very good oxygen transmission rates (OTR) with an improvement factor of 86 for a 15 nm film by using DMAD and a factor of 25 for a film thickness of just 5 nm by using BDEDA compared to bare PET substrates. All these film attributes are of the same quality as those obtained for the industrial precursor TMA, rendering the new precursors safe and potential alternatives to TMA.