Photocatalytic Degradation of 4,4′-Isopropylidenebis(2,6-Dibromophenol) on Sulfur-Doped Nano TiO2

In present work, we examine the photocatalytic properties of S-doped TiO2 (S1, S2) compared to bare TiO2 (S0) in present work. The photocatalytic tests were performed in alkaline aqueous solutions (pH = 10) of three differently substituted phenols (phenol (I), 4,4′-isopropylidenebisphenol (II), and 4,4′-isopropylidenebis(2,6-dibromophenol) (III)). The activity of the catalysts was evaluated by monitoring I, II, III degradation in the reaction mixture. The physicochemical properties (particle size, ζ-potential, Ebg, Eu, E0cb, E0vb, σo, KL) of the catalysts were established, and we demonstrated their influence on degradation reaction kinetics. Substrate degradation rates are consistent with first-order kinetics. The apparent conversion constants of the tested compounds (kapp) in all cases reveal the sulfur-loaded catalyst S2 to show the best photocatalytic activity (for compound I and II S1 and S2 are similarly effective). The different efficiency of photocatalytic degradation I, II and III can be explained by the interactions between the catalyst and the substrate solution. The presence of bromine substituents in the benzene ring additionally allows reduction reactions. The yield of bromide ion release in the degradation reaction III corresponds to the Langmuir constant. The mixed oxidation-reduction degradation mechanism results in higher degradation efficiency. In general, the presence of sulfur atoms in the catalyst network improves the degradation efficiency, but too much sulfur is not desired for the reduction pathway.

Colorimetric Monitoring of a Chemical Reaction Using Cesium Lead Halide Assays

Cesium lead halide (CsPbX3, X = F, Cl, Br, I ) nanomaterials have a number of novel optoelectronic and physical properties, both of which are tailorable based on halide type and concentration, such as halide composition-dependent photoluminescence and rapid halide exchange while maintaining crystal structure. In this work we take advantage of these properties and use colloidal CsPbI3 nanoparticles as a proxy and colorimetric sensor of a chemical reaction in real-time. A solvolysis reaction between 2-bromo-2-methylbutane and butanol was used as a model system. A product of reaction, a bromide ion, could be detected via halide exchange with CsPbI3, by way of a quantitative blue shift (Δλ) in photoluminescence. The kinetics of this shift was calibrated against a known Br - source, which allowed for conversion to apparent values solvation kinetics. The observed rate constants (k) and corresponding activation energies (Ea) measured via the CsPbI3 probe were consistent with literature values for the reaction, confirming the validity of the approach.

Reactivity Studies of Thiophosgene and its Halo Versions towards Diazo Derivatives

The reactions of thiophosgene with diazo derivatives gives dichloro-alkene derivatives and cyclized, 1,2,3-thiadiazoles respectively. The product formation is mainly depending on substitutions on diazo substrates. When its halo versions, CSBr2 and in combination with bromide ion, CSBr2 less reactive than bromide ion with disubstituted diazo, give gem-dihalo derivatives whereas more reactive with mono substituted diazo to gives 1,2,3-thiadiazoles. In case CSI2 irrespective of substitution on diazo, iodide ion is more reactive then CSI2 was observed.

The Effect of the Corrosion Medium on Silane Coatings Deposited on Titanium Grade 2 and Titanium Alloy Ti13Nb13Zr

The present paper focuses on the fabrication of coatings based on vinyltrimethoxysilane and the influence of various corrosion media on the coatings produced. Coatings were deposited on two substrate materials, namely, titanium Grade 2 and titanium alloy Ti13Nb13Zr, by immersion in a solution containing vinyltrimethoxysilane, anhydrous ethyl alcohol, acetic acid and distilled water. The obtained coatings were characterized in terms of surface morphology, adhesion to the substrate and corrosion resistance. As corrosion solutions, four different simulated physiological fluids, which differed in the contents of individual ions, and a 1 mol dm−3 NaBr solution were used. The chloride ions contained in the simulated physiological fluids did not lead to pitting corrosion of titanium Grade 2 and titanium alloy Ti13Nb13Zr. This investigation shows that titanium undergoes pitting corrosion in a bromide ion medium. It is demonstrated that the investigated coatings slow down corrosion processes in all corrosion media examined.

Photoredox Catalyzed Ring-Opening Addition Reaction Between Benzyl Bromides and Cyclic Ethers

A novel nucleophilic reaction between cyclic ethers and benzyl bromides is achieved under photoredox catalysis. The reaction proceeds through a single electron transfer (SET) pathway rather than a common SN2 mechanism. By two steps of reduction and oxidation, a benzyl bromide heterolyzes to give a carbocation and bromide ion under mild conditions, and then a cyclic ether captures both the carbocation and bromide ion to afford the addition product.

Constrained Molecular Dynamic Simulation of the Potential Mean Force of Lithium Bromide Ion Pairs in Acetonitrile

Molecular dynamic simulations of Li+, and Br− ions in acetonitrile were carried out. The simulated structural properties were compared to experimental data. The solvent potentials of Li+-Br−, Li+-Li+, and Br−-Br− were evaluated using constrained molecular dynamics (CMD) simulations, to determine the solvent contribution to the total force acting on the solute and estimate the liquid arrangements according to the potential of mean force (PMF) values. The PMF of friction kernels and the passage across the Li+-Br− barrier was studied using the Grote–Hynes theory. The union-separation development happens in the polarization confining system.

In-situ study of electrochemical migration of tin in the presence of bromide ion

The miniaturization of electronic devices and the consequent decrease in the distance between conductive lines have increased the risk of short circuit failure due to electrochemical migration (ECM). The presence of ionic contaminants affects the ECM process. This work systematically investigates the ECM of tin (Sn) in the presence of bromide ions (Br−) in the range of 10−6 M to 1.0 M. Water drop test (WDT) was conducted in the two-probe semiconductor characterization system under an optical microscope as an in-situ observation. Polarization test was carried out to study the correlation between the corrosion properties of Sn and its ECM behaviour. The products of ECM were characterized by scanning electron microscope coupled with an energy dispersive X-rays spectrometer (SEM/EDX) and X-ray photoelectron spectrometer (XPS). The results confirm that the rate of anodic dissolution of Sn monotonously increases with the Br− concentration. However, the probability of ECM failure follows a normal distribution initially, but later increases with the Br− concentration. The main products of the ECM reactions are identified as Sn dendrites and tin hydroxide precipitates. The mechanisms of the ECM process of Sn in the presence of Br− are also suggested.