RESUMEN
2,3-Dialdehyde cellulose (DAC) of a high degree of oxidation (92% relative to AGU units) prepared by oxidation of microcrystalline cellulose with sodium periodate (48 °C, 19 h) is soluble in hot water. Solution casting, slow air drying, hot pressing, and reinforcement by cellulose nanocrystals afforded films (â¼100 µm thickness) that feature intriguing properties: they have very smooth surfaces (SEM), are highly flexible, and have good light transmittance for both the visible and near-infrared range (89-91%), high tensile strength (81-122 MPa), and modulus of elasticity (3.4-4.0 GPa) depending on hydration state and respective water content. The extraordinarily low oxygen permeation of <0.005 cm3 µm m-2 day-1 kPa-1 (50% RH) and <0.03 cm3 µm m-2 day-1 kPa-1 (80% RH) can be regarded as a particularly interesting feature of DAC films. The unusually high initial contact angle of about 67° revealed a rather low hydrophilicity compared to other oxidatively modified or unmodified cellulosic materials which is most likely the result of inter- and intramolecular hemiacetal and hemialdal formation during drying and pressing.
Asunto(s)
Celulosa/análogos & derivados , Membranas Artificiales , Celulosa/química , Celulosa/efectos de la radiación , Elasticidad , Calor , Luz , Nanopartículas/química , Oxígeno/químicaRESUMEN
We present an approach to construct biocompatible and photoluminescent hybrid materials comprised of carbon quantum dots (CQDs) and TEMPO-oxidized cellulose nanocrystals (TO-CNCs). First, the amino-functionalized carbon quantum dots (NH2-CQDs) were synthesized using a simple microwave method, and the TO-CNCs were prepared by hydrochloric acid (HCl) hydrolysis followed by TEMPO-mediated oxidation. The conjugation of NH2-CQDs and TO-CNCs was conducted via carbodiimide-assisted coupling chemistry. The synthesized TO-CNC@CQD hybrid nanomaterials were characterized using X-ray photoelectron spectroscopy, cryo-transmittance electron microscopy, confocal microscopy, and fluorescence spectroscopy. Finally, the interactions of TO-CNC@CQD hybrids with HeLa and RAW 264.7 macrophage cells were investigated in vitro. Cell viability tests suggest the surface conjugation with NH2-CQDs not only improved the cytocompatibility of TO-CNCs, but also enhanced their cellular association and internalization on both HeLa and RAW 264.7 cells after 4 and 24 h incubation.