Acidic or basic dyeing of fibers involves ionic interactions between reactive groups on the polymers and dye molecules. Such interactions can be utilized in the functional finishing of fabrics. This article discusses a new approach of employing the ionic interactions between anionic carboxylic end groups of polyamides and cationic quaternary ammonium salts in the chemical finishing of nylon fabrics to achieve desired durable antimicrobial functions. The finishing conditions such as pH, finishing temperature, and time were studied, and the pH of the finishing bath was very critical in affecting the ionic interactions and thus exhaustion of the salts on the fabrics. The finishing process should be carried out at a temperature above the glass transition temperature of nylon 66. The finished products demonstrated excellent durability of antimicrobial functions.
Anatase and brookite
are robust materials with enhanced photocatalytic
properties. In this study, we used density functional theory (DFT)
with a hybrid functional and the Hubbard on-site potential methods
to determine electron- and hole-polaron geometries for anatase and
brookite and their energetics. Localized electron and hole polarons
were predicted not to form in anatase using DFT with hybrid functionals.
In contrast, brookite formed both electron and hole polarons. The
brookite electron-polaronic solution exhibits coexisting localized
and delocalized states, with hole polarons mainly dispersed on two-coordinated
oxygen ions. Hubbard on-site potential testing over the wide 4.0–10
eV range revealed that brookite polarons are formed at
U
= 6 eV, while anatase polarons are formed at
U
=
8 eV. The brookite electron polaron was always localized on a single
titanium ion under the Hubbard model, whereas the hole polaron was
dispersed over four oxygen atoms, consistent with the hybrid DFT studies.
The anatase electron polarons were dispersed at lower on-site potentials
but were more localized at higher potentials. Both methods predict
that brookite has a higher driving force for the formation of polarons
than anatase.
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