Monte Carlo simulations of the exchange kinetics of polymers adsorbed on a solid surface

The exchange kinetics of polymers adsorbing on a solid surface is extensively studied by dynamic Monte Carlo simulations. A model employed simulates a semidilute polymer solution placed in contact with a solid surface that attracts polymer segments by the adsorption interaction (χ_s). The exchange process of polymer chains, between the solution and the adsorbed polymer layer, is examined under various conditions. The exchange kinetics shows two characteristic regimes with increasing chain length. One is the diffusion‐controlled regime found with a small χ_s , and the other the detachment‐controlled regime with a large χ_s . These two regimes are well described by a kinetic theory. Various dynamic quantities show that the diffusion‐controlled regime is not due to sluggish dynamics near the surface, but rather to bulk diffusion of chains. The diffusion‐controlled regime found in this study is considered to appear at the high temperature limit.     

Photoluminescent copolymer-pendant Ru(BPY)32+ grafted onto non-woven silk fabric and its application to oxygen sensor

Copolymer-pendant Ru(bpy)₃²⁺ grafted onto silk fibroin was prepared by at first grafting copoly(4-methyl-4′-vinyl-2,2′-bipyridine - methylmethacrylate) onto non-woven silk fabric, and then by reacting the grafted sample with cis-Ru(bpy)₂Cl₂. Photoluminescence of this silk-poly Ru complex and its quenching by oxygen were studied in gas, methanol and water phases. The relative emission intensity and the emission lifetime of the silk-poly Ru showed that there are two kinds of sites for the Ru complex. The major, longer lifetime component (1070 ns, 77.1%, under Ar gas) is considered to be surrounded by polymer matrices, and the minor, shorter one (288 ns, 22.9%) seems to be exposed and is subjected to concentration quenching. The shorter lifetime species are quenched by oxygen more effectively than the longer ones. The mechanism of the quenching by oxygen and its application to oxygen sensor were discussed.     

Modulating Electronic Metal-Support Interactions to Boost Visible-Light-Driven Hydrolysis of Ammonia Borane: Nickel-Platinum Nanoparticles Supported on Phosphorus-Doped Titania

Ammonia borane (AB) is a promising material for chemical H₂ storage owing to its high H₂ density (up to 19.6 wt %). However, the development of an efficient catalyst for driving H₂ evolution through AB hydrolysis remains challenging. Therefore, a visible-light-driven strategy for generating H₂ through AB hydrolysis was implemented in this study using Ni−Pt nanoparticles supported on phosphorus-doped TiO₂ (Ni-Pt/P-TiO₂) as photocatalysts. Through surface engineering, P-TiO₂ was prepared by phytic-acid-assisted phosphorization and then employed as an ideal support for immobilizing Ni−Pt nanoparticles via a facile co-reduction strategy. Under visible-light irradiation at 283 K, Ni₄₀Pt₆₀/P-TiO₂ exhibited improved recyclability and a high turnover frequency of 967.8 mol mol_Pt⁻¹ min⁻¹. Characterization experiments and density functional theory calculations indicated that the enhanced performance of Ni₄₀Pt₆₀/P-TiO₂ originated from a combination of the Ni−Pt alloying effect, the Mott–Schottky junction at the metal-semiconductor interface, and strong metal-support interactions. These findings not only underscore the benefits of utilizing multipronged effects to construct highly active AB-hydrolyzing catalysts, but also pave a path toward designing high-performance catalysts by surface engineering to modulate the electronic metal-support interactions for other visible-light-induced reactions.