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1. Coaxial Spinning of All-Cellulose Systems for Enhanced Toughness

Author

Claudia Oviedo, Orlando J. Rojas, Meri Lundahl, Luis E. Arteaga-Pérez, Guillermo Reyes, Alistair W. T. King, Serguei Alejandro-Martín, Department of Chemistry, and Doctoral Programme in Chemistry and Molecular Sciences

Subjects
Materials science, Polymers and Plastics, IONCELL-F FIBERS, Scanning electron microscope, 116 Chemical sciences, Nanofibers, Ionic Liquids, Bioengineering, 02 engineering and technology, 010402 general chemistry, FILMS, OXIDATION, 01 natural sciences, Gas Chromatography-Mass Spectrometry, Nanocellulose, Biomaterials, chemistry.chemical_compound, DISSOLUTION, Tensile Strength, Materials Chemistry, WATER, CYTOTOXICITY, Cellulose, Spinning, Dissolution, NATIVE CELLULOSE, chemistry.chemical_classification, Hydrogels, 021001 nanoscience & nanotechnology, 0104 chemical sciences, NANOCRYSTALS, chemistry, Chemical engineering, Ionic liquid, Self-healing hydrogels, Propionate, PAPER, NANOCELLULOSE, 0210 nano-technology
Abstract

Hydrogels of TEMPO-oxidized nanocellulose were stabilized for dry-jet wet spinning using a shell of cellulose dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium propionate ([DBNH][CO2Et]), a protic ionic liquid (PIL). Coagulation in an acidic water bath resulted in continuous core-shell filaments (CSFs) that were tough and flexible with an average dry (and wet) toughness of similar to 11 (2) MJ.m(-3) and elongation of similar to 9 (14) %. The CSF morphology, chemical composition, thermal stability, crystallinity, and bacterial activity were assessed using scanning electron microscopy with energy-dispersive X-ray spectroscopy, liquid-state nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, pyrolysis gas chromatography-mass spectrometry, wide-angle X-ray scattering, and bacterial cell culturing, respectively. The coaxial wet spinning yields PIL-free systems carrying on the surface the cellulose II polymorph, which not only enhances the toughness of the filaments but facilities their functionalization.

Published
2020
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2. Preparation of silver nano-particles immobilized onto chitin nano-crystals and their application to cellulose paper for imparting antimicrobial activity.

Author

Li, Zhihan, Zhang, Ming, Cheng, Dong, and Yang, Rendang

Subjects
*SILVER nanoparticles, *CHITIN, *NANOCRYSTALS, *CELLULOSE, *PAPER, *ANTI-infective agents
Abstract

Immobilized silver nano-particles (Ag NPs) possess excellent antimicrobial properties due to their unique surface characteristics. In this paper, immobilized silver nano-particles were synthesized in the presence of chitin nano-crystals (CNC) based on the Tollens mechanism (reduction of silver ion by aldehydes in the chitosan oligosaccharides (COS)) under microwave-assisted conditions. The prepared Ag NPs-loaded CNC nano-composites were then applied onto the paper surface via coating for the preparation of antibacterial paper. Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results confirmed that the Ag NPs were immobilized onto the CNC. The transmission electron microscope (TEM) and scanning electron microscopy (SEM) results further revealed that the spherical Ag NPs (5–12 nm) were well dispersed on the surface of CNC. The coated paper made from the Ag NPs-loaded CNC nano-composites exhibited a high effectiveness of the antibacterial activity against E. coli or S. aureus . [ABSTRACT FROM AUTHOR]

Published
2016
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3. Hydride Generation for Headspace Solid-Phase Extraction with CdTe Quantum Dots Immobilized on Paper for Sensitive Visual Detection of Selenium

Author

Lu Yang, Xiandeng Hou, Chengbin Zheng, Kailai Xu, Wei Zhu, and Ke Huang

Subjects
Paper, Headspace solid-phase extraction, X ray diffraction, X ray photoelectron spectroscopy, Phase separation, Analytical chemistry, chemistry.chemical_element, Relative standard deviations, Spectrofluorometers, Extraction, 02 engineering and technology, 01 natural sciences, Analytical Chemistry, Selenium, Quantum Dots, Cadmium Compounds, Cadmium telluride, Semiconductor quantum dots, Animals, Humans, Solid phase extraction, Detection limit, Hydride, Hydrides, Muscles, 010401 analytical chemistry, Extraction (chemistry), Solid Phase Extraction, Human urine samples, Spectrofluorometer, Conventional methods, 021001 nanoscience & nanotechnology, Nanocrystals, Hydride generations, 0104 chemical sciences, Body fluids, Potential interferences, Certified reference materials, chemistry, Dogfish, Density functional theory, Quantum Theory, Tellurium, 0210 nano-technology, Hair
Abstract

A low-cost, simple, and highly selective analytical method was developed for sensitive visual detection of selenium in human urine both outdoors and at home, by coupling hydride generation with headspace solid-phase extraction using quantum dots (QDs) immobilized on paper. The visible fluorescence from the CdTe QDs immobilized on paper was quenched by H2Se from hydride generation reaction and headspace solid-phase extraction. The potential mechanism was investigated by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) as well as Density Functional Theory (DFT). Potential interferences from coexisting ions, particularly Ag(+), Cu(2+), and Zn(2+), were eliminated. The selectivity was significantly increased because the selenium hydride was effectively separated from sample matrices by hydride generation. Moreover, due to the high sampling efficiency of hydride generation and headspace solid phase extraction, the sensitivity and the limit of detection (LOD) were significantly improved compared to conventional methods. A LOD of 0.1 μg L(-1) and a relative standard deviation (RSD, n = 7) of 2.4% at a concentration of 20 μg L(-1) were obtained when using a commercial spectrofluorometer as the detector. Furthermore, a visual assay based on the proposed method was developed for the detection of Se, 5 μg L(-1) of selenium in urine can be discriminated from the blank solution with the naked eye. The proposed method was validated by analysis of certified reference materials and human urine samples with satisfactory results.

Published
2015