ABSTRACT
Novel nanosized biomass-based pH-responsive cellulose nanofibers (CNF-PEI) with excellent biocompatibility were tailored by grafting polyethylenimine (PEI) onto carboxylated cellulose nanofibers (CNF-COOH); the active site (-COOH, 0.96 mmol/g) was anchored on cellulose nanofibers (CNFs) to introduce PEI with a high density (10.57 mmol/g) of amino groups. The as-prepared CNF-PEI not only maintained the good properties of CNFs but also possessed excellent biocompatibility and pH-responsive properties, offering interesting possibilities for pH-induced sustained drug release and medical dressing. The CNF-PEI showed rapid wettability conversion from hydrophilic, underwater superoleophobic (WCA = 20.7°, OCA = 159.3°) to hydrophobic, superoleophilic (WCA = 129.6°, OCA = 29.7°) in response to pH change from acidic conditions to alkaline conditions. The antibacterial activity of CNF-PEI toward Escherichia coli and Listeria monocytogenes was 100% and 94.6% under acidic conditions, respectively. Furthermore, the pH-responsive mechanism of CNF-PEI was revealed by XPS, 13C NMR, 1H NMR, and AFM analyses.
Subject(s)
Nanofibers , Anti-Bacterial Agents/pharmacology , Cellulose , Drug Liberation , Hydrogen-Ion ConcentrationABSTRACT
A novel biomass cellulose-based colorimetric sensor (DAC-PDH) was prepared by a Schiff base reaction between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of 2,6-pyridine dihydrazide (PDH). The as-prepared sensor (DAC-PDH) showed selective recognition of Cu2+ and a visual colour change from white to green. The visual limit of detection for Cu2+ was 10-7 mol/L. Furthermore, DAC-PDH responded to Cu2+ within 30 s by the method of dynamic condition. The sensor possessed the properties of a high density of functional groups (CO, NH, NH2), a large external surface area, a short transit distance and flexibility; thus, Cu2+ can be rapidly absorbed and enriched on the DAC-PDH through multi-dentate ligand chelation between Cu2+ and the carbonyl groups (CO) and the amino groups (NH, NH2) of DAC-PDH. The as-prepared DAC-PDH colorimetric sensor exhibits promising prospects for in situ identification of Cu2+.
ABSTRACT
Two novel pH-responsive reversible-wettability biomass cellulose-based materials of cellulose-g-PAA and cellulose-g-PAM were conveniently prepared by grafting acrylic acid (AA) and acrylamide (AM), respectively, onto eucalyptus pulp cellulose. The hydrophobic-oleophilic of cellulose-g-PAA and the oleophobic-hydrophilic of cellulose-g-PAM were converted to oleophobic-hydrophilic and hydrophobic-oleophilic, respectively, as the pH converted from 1 to 9. The pH-responsive mechanism of these cellulose-based materials was investigated by 13C nuclear magnetic resonance, X-ray photoelectron spectroscopy, and atomic force microscopy analyses. The resulting cellulose-g-PAA and cellulose-g-PAM papers were applied in the switchable separation of oil/water mixtures. Water passed through the cellulose-g-PAA paper at pH = 9 and cellulose-g-PAM paper at pH = 1, while oil was retained. After changing the pH value, oil permeated these papers, but water did not. The papers exhibited excellent regeneration performances; the oil adsorbed on the papers was completely desorbed via pH control.
ABSTRACT
A thermo-responsive cellulose-based material (cellulose-g-PNIPAAm) was prepared by grafting N-isopropylacrylamide (NIPAAm) onto bagasse pulp cellulose via Ce (IV)-initiated free radical polymerization. The surfaces of the obtained cellulose-g-PNIPAAm paper showed a rapid wettability conversion from being hydrophilic (water contact angles (WCA) of 0°) at 25 °C to becoming hydrophobic (WCA of 134.2°) at 45 °C. Furthermore, the thermo-responsive mechanism of cellulose-g-PNIPAAm was examined by the in situ variable-temperature 13C NMR, ¹H NMR and AFM analysis. At the same time, the resulting cellulose paper was applied for a switchable separation of oil/water mixtures. Water can pass through the paper under 45 °C, while oil is kept on the paper. When the temperature is above 45 °C, oil can permeate through the paper, while water cannot pass through the water. Moreover, the paper exhibited excellent regeneration performance after five cycles and maintained its switchable wettability.
