Time-resolved infrared spectroscopy as an in situ tool to study the kinetics during self-assembly of mesostructured films

Rapid scan time-resolved infrared spectroscopy has been used to investigate in situ the kinetics of the chemical processes involved in the formation of self-assembled mesostructured films. The experiments have been done in transmission mode on films cast on a diamond disk using an infrared microscope. Two specific materials have been studied: silica and titania mesoporous films templated by a triblock copolymer surfactant (Pluronic F-127). The time dependence of solvent evaporation and condensation of the chemical species have been clearly observed. Different stages in the film formation have been identified, which support well the general theory of self-assembly. The in situ FTIR spectroscopy using time-resolved rapid scan has proven to be a very effective tool for in situ analysis of film formation from a liquid phase.     

Optimal interval lengths for nonlocal boundary value problems associated with third order Lipschitz equations

For the third order differential equation, y^?=f(x,y,y^′,y^″), where f(x,y₁,y₂,y₃) is Lipschitz continuous in terms of yi, i=1,2,3, we obtain optimal bounds on the length of intervals on which there exist unique solutions of certain nonlocal three and four point boundary value problems. These bounds are obtained through an application of the Pontryagin Maximum Principle from the theory of optimal control.     

Synthesis of fluoro and trifluoromethyl derivatives of 2-phenylquinolin-4-ol

A tert-butoxide base-mediated cyclization of fluoro- and trifluoromethyl-substituted Schiff bases 12-19 produces 4-tert-butoxyquinolines 23-30 which are hydrolyzed to quinolin-4-ols 31-38 .     

Adsorbate-induced alloy phase separation: a direct view by high-pressure scanning tunneling microscopy

The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure scanning tunneling microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au.     

Multiple symmetric positive solutions for a second order boundary value problem

For the second order boundary value problem, , , , where growth conditions are imposed on which yield the existence of at least three symmetric positive solutions.

     

Oxidation of Pt(110)

Using scanning tunneling microscopy and temperature programmed desorption we investigate the Pt(110) surface under strongly oxidizing conditions involving either high-pressure O2 or atomic oxygen exposure. At low temperatures, only disordered Pt oxide structures are observed. After annealing ordered surface oxide islands are observed to coexist with a highly stable reconstructed (12x2)-O chemisorption structure. From density functional theory calculations a model for the surface oxide phase is revealed. The phase is found to be metastable, and its presence is explained in terms of stabilizing defects in the chemisorption layer and reduced Pt mobility.     

A new phase modulated binomial‐like selective‐inversion sequence for solvent signal suppression in NMR

A new 8 ‐pulse P hase M odulated binomial‐like selective inversion pulse sequence, dubbed ‘8PM’, was developed by optimizing the nutation and phase angles of the constituent radio‐frequency pulses so that the inversion profile resembled a target profile. Suppression profiles were obtained for both the 8PM and W5 based excitation sculpting sequences with equal inter‐pulse delays. Significant distortions were observed in both profiles because of the offset effect of the radio frequency pulses. These distortions were successfully reduced by adjusting the inter‐pulse delays. With adjusted inter‐pulse delays, the 8PM and W5 based excitation sculpting sequences were tested on an aqueous lysozyme solution. The 8 PM based sequence provided higher suppression selectivity than the W5 based sequence. Two‐dimensional nuclear Overhauser effect spectroscopy experiments were also performed on the lysozyme sample with 8PM and W5 based water signal suppression. The 8PM based suppression provided a spectrum with significantly increased (~ doubled) cross‐peak intensity around the suppressed water resonance compared to the W5 based suppression. Copyright © 2016 John Wiley & Sons, Ltd.