No periodate oxidation on chitin? For the first time, direct selective alkaline periodate oxidation of chitin led to the isolation of ordered domains as uniform anisotropic and zwitterionic ChNCs after simultaneous removal of non-ordered domains.
Many efforts have been made to isolate native nanocrystals from raw materials in the last two decades, such as cellulose nanocrystals (CNCs), but existing methods still suffer from low yields, complicated synthesis processes, and nonuniform sizes of obtained CNCs. This study concerns a facile, self-terminating, and efficient method for the formation of uniform CNCs in high yields during the periodate oxidation process within Pickering emulsions. A biphasic system containing hexane with dissolved hexylamine and an aqueous solution of sodium periodate (NaIO ) was used as the reaction medium. Regulated by hexylamine, owing to its limited solubility in water, the pH value of the aqueous phase was enhanced to around 9.8, leading to the precipitation of sodium orthoperiodate (Na H IO ) nanoplates and thus the formation of the initial Pickering emulsions. During the gradual formation of cellulose nanofibers and then CNCs, CNCs were attracted to stabilize the interface of the Pickering emulsions, which prevented further decomposition of CNCs by the oxidizing agent in aqueous suspensions. Thus, this isolation strategy secured the efficient separation of CNCs based on their own particular amphiphilic properties and achieved a high yield of up to 56 wt %.
13 C and 15 N solid-state nuclear magnetic resonance (NMR) combined with dynamic nuclear polarization (DNP) is used to investigate the structure of dye-doped biopolymer-based materials that can be used in amplified spontaneous emission (ASE) experiments. By comparing calligraphic paper prepared from cellulose and scaffolds prepared from chitosan as substrates, differences in the interactions of the carrier material with the dye molecule Calcofluor White are obtained. These are most probably induced by structural changes of the carrier material due to its interaction with water forming hydrogen bonds. Such structural differences may explain the obtained variation of the emission wavelength of Calcofluor White doped on these substrates in ASE experiments.
An
efficient approach for the characterization of core–shell
polymer hybrid nanoparticles is presented. Selective signal amplification
by dynamic nuclear polarization (DNP) is employed to shed more light
on the molecular structure of surface sites and shell of the particles.
DNP-enhanced 29Si solid-state NMR is used to clearly prove
the core–shell structure of the nanoparticles as well as the
success of their functionalization with low amounts of trimethylsiloxy
groups. By combination of DNP-enhanced 1H → 29Si and 1H → 13C cross-polarization
magic-angle-spinning experiments, differently substituted alkoxysilane
moieties, namely, methacryloxypropyltriethoxysilane, 3-methacryloxypropyltriisopropoxysilane,
and 3-methacryloxypropyltris(methoxyethoxy)silane, are investigated,
revealing various cross-linking capabilities of the particle shell.
This knowledge about efficiency of surface functionalization and cross-linking
sites strongly influences the application and properties of the core–shell
polymer hybrid particles, for instance, as materials for photonic
crystals, particle film formation, and coatings. This is of high importance
for the design of tailor-made core–shell particle architectures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.