纳米纤维素研究及应用进展Ⅱ

纳米纤维素是一种新型的高分子功能材料,具有独特的结构和优良的性能,特别是细菌纤维素,其三维纳米网状结构,生物适应性,良好的机械稳定性,抗菌性等优良性能使它越来越收到重视。本文是"纳米纤维素研究及应用进展Ⅰ"的下篇,本文中介绍了近年来对于纳米纤维素应用和研究的进展。文中主要内容有纳米纤维素在生物、医学、增强剂、造纸工业、净化、传导、与无机物复合、食品工业、磁性复合物等方面的应用。     

Growth factor functionalized biodegradable nanocellulose scaffolds for potential wound healing application

Cellulose - Nanocellulose has been highlighted as one of the most promising biomaterials for biomedical applications with the potential to outperform conventional polymeric materials. However, the...     

Comparative study on properties of nanocellulose derived from sustainable biomass resources

Cellulose - Nanocellulose, a unique and promising nanosized cellulose fibers extracted from renewable biomass, has gained much attention from both the scientific and industrial communities due to...     

Cellulose nanoanemone: an asymmetric form of nanocellulose

Cellulose - Nanocellulose with increasing attention in basic research and for use in advanced materials is usually considered to have a symmetrical nanofibril, nanorod or fibrillated nanofiber...     

Enhanced curcumin loaded nanocellulose: a possible inhalable nanotherapeutic to treat COVID-19

Cellulose - Nanocellulose/polyvinyl alcohol/curcumin (CNC/PVA/curcumin) nanoparticles with enhanced drug loading properties were developed by the dispersion of nanocellulose in curcumin/polyvinyl...     

纳米纤维素研究及应用进展Ⅰ

纳米纤维素是一种新型的高分子功能材料,具有独特的结构和优良的性能。特别是细菌纤维素,其三维纳米网状结构,生物适应性,良好的机械稳定性,抗菌性等优良性能使它越来越收到重视。本文介绍了近年来对于纳米纤维素制备和应用的研究进展,主要涉及细菌纤维素,植物纤维素和纤维素纳米复合物的制备。本文的下篇《纳米纤维素研究及应用进展Ⅱ》将继续介绍纳米纤维素在生物,医学,增强剂,造纸工业,净化,传导,与无机物复合,食品工业,磁性复合物等方面的应用。     

Nanocellulose characteristics from the inner and outer layer of banana pseudo-stem prepared by TEMPO-mediated oxidation

Many tonnes of agricultural wastes are generated annually, which contains a relatively high amount of cellulose; banana pseudo-stem is one waste type that is a promising material for nanocellulose production. This research characterised nanocellulose from inner and outer layers of banana pseudo-stem as a preliminary research strategy for designing biodegradable packaging material from banana pseudo-stem nanocellulose. Nanocellulose was successfully prepared through TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl)-mediated oxidation. The extracted nanocellulose from both the inner and outer layers had observed widths of approximately 7–35 nm and long fibrillated fibre. They had high negative zeta potential (lower than ?33.6) that provided good colloidal stability. The purity of the nanocellulose was high as demonstrated by ¹³C solid-state NMR and Fourier transform infrared spectroscopy. Nanocellulose from both layers was significantly more crystalline than the raw materials. Thermal stability of nanocellulose sourced from inner and outer layers was relatively similar, with degradation temperature of approximately 220 °C, which was slightly lower than the degradation temperature of its native form (232 °C for inner layer and 261 °C for outer layer).     

Nanocellulose-based soft actuators and their applications

Nanocellulose has aroused growing attention in the design and fabrication of multifarious soft actuators thanks to its abundant source, appropriate mechanical properties, and sustainability. In this mini-review, an up-to-date account of recent progresses in nanocellulose-based actuators with homogeneous and heterogeneous structures is provided. The fundamental design concepts and synthesis strategies for nanocellulose-based soft actuators with a wide array of micro-architecture are described. Moreover, their actuation mechanisms, structure–function relationships, and emerging applications in the fields of soft robotics, biomedical science and bioelectronics are highlighted. Finally, a brief conclusion, the current challenges, and future perspectives in the development of nanocellulose-based actuators is presented. This mini-review provides new insights into the fundamental research and the technological application of advanced nanocellulose-based soft actuators.     

Carboxyl-functionalized Nanocellulose Reinforced Nanocomposite Proton Exchange Membrane

Nanocellulose(NCC) was prepared through the acid hydrolysis of microcellulose(MCC) and was reacted with maleic anliydride to obtain carboxyl-functionized nanocellulose(MA-NCCs). The presence of .OH and .SO3H on the surface of rod-like MA-NCC was confirmed by Fourier transfonn infrared spectrometry(FTIR). Sulfonated poly(aryl ether ether ketone ketone)(Ph-SPEEKK) was synthesized with bis(4-fluorophenyl-methanone) and 2-phenylhydroquinone as monomer. MA-NCC/Ph-SPEEKK nanocomposite membranes with different MA-NCCs content were prepared, and their properties were characterized. Compared with Ph-SPEEKK, MA-NCC/Ph-SPEEKK nanocomposite membrane showed better mechanical and thermal properties and higher proton conductivity. The proton conductivity of the composite membrane with 4%(mass fraction) MA-NCCs under 80℃ was 0.095 S/cm. And its tensile strength reached 30.3 MPa, which was 21.2% higher than that of Ph-SPEEKK pure polymer membrane.     

Nanocellulose as a novel nanostructured adsorbent for environmental remediation: a review

Nanocellulose is a lightweight material with strong mechanical strength, inexpensive production costs and safe handling compared to synthetic nanoparticles. Thanks to the high specific surface area, broad possibility of surface modification and high mechanical strength, nanocellulose has emerged as a new class of biobased adsorbent with promising potential application in environmental remediation. Many classes of pollutants could be adsorbed by nanocellulose, including heavy metals, dissolved organic pollutants, dyes, oil and undesired effluents. The possibility for the regeneration of the nanocellulose adsorbent is another benefit driving attempts to fully exploit this new class of nanostructured biobased material. In this review, an update of the most relevant uses of nanocellulose as a new class of adsorbents for environmental remediation is outlined. An emphasis on the key advancement of surface modifications of nanocellulose to enhance the adsorption efficiency according to the pollutant class is highlighted.     

Filler-nanocellulose substrate for printed electronics: experiments and model approach to structure and conductivity

Composites made of inorganic filler particles and cellulose nanofibres can be applied as substrates for printed electronics. We have studied the structural properties of these substrates both experimentally and with particle-level modeling approach. Our model describes the skeleton structure formed by pigment particles of varied shapes and size distributions. Nanocellulose is assumed to fill voids of the structure. The model simulations predict quite well the relative changes in measured density, porosity and roughness for kaolin and precipitated calcium carbonate (PCC) pigments. Measured roughness turns out to be higher for kaolin than for PCC. Yet, the measured conductivity of printed lines on kaolin surface is higher than the conductivity on the PCC surface. The simulations reveal a more open surface pore structure for PCC than for kaolin, which leads to stronger absorption of the silver ink, and thus explains the differences in the measured conductivities.     

Novel aspects of nanocellulose

Novel nanoscaled cellulose particles were prepared using high-pressure homogenization of aqueous media contenting treated cellulose samples in a Microfluidizer^® processor (MF). Here, we present the generation of spherical cellulose nanoparticles as an extension of previously published reports of nano fibrillated cellulose. Although MF treatment of unmodified cellulose yields nanofibrils which are reported in several publications, in the current work different kinds of pretreatments were proven to be necessary to obtain spherical structured cellulose nanoparticles. One such treatment may be the decrystallization of cellulose regenerating it from N-methylmorpholine-N-oxid-monohydrate (NMMNO*H₂O). Nanocellulose was then obtained by a subsequent high-pressure mechanical treatment of the precipitate in aqueous dispersion. Decrystallization was also realized by grinding cellulose in a planetary ball mill. The resulting amorphous intermediates were characterized by Raman spectroscopy. Another approach tested was hydrolysis and subsequent mechanical treatment using an Ultra-Turrax^® and MF. Another alternative was given by the mechanical treatment of aqueous dispersions of low substituted cellulose derivatives such as carboxymethyl cellulose and oxidized cellulose without any further hydrolysis.     

Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5–12 nm, stacks of nanofibrils with widths of 20–200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.     

Comparison of nano- and microfibrillated cellulose films

Nanocellulose is an interesting building block for functional materials and has gained considerable interest due to its mechanical robustness, large surface area and biodegradability. It can be formed into various structures such as solids, films and gels such as hydrogels and aerogels and combined with polymers or other materials to form composites. Mechanical, optical and barrier properties of nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) films were studied in order to understand their potential for packaging and functional printing applications. Impact of raw material choice and nanocellulose production process on these properties was evaluated. MFC and NFC were produced following two different routes. NFC was produced using a chemical pretreatment followed by a high pressure homogenization, whereas MFC was produced using a mechanical treatment only. TEMPO-mediated oxidation followed by one step of high pressure (2,000 bar) homogenization seems to produce a similar type of NFC from both hardwood and softwood. NFC films showed superior mechanical and optical properties compared with MFC films; however, MFC films demonstrated better barrier properties against oxygen and water vapor. Both the MFC and NFC films were excellent barriers against mineral oil used in ordinary printing inks and dichlorobenzene, a common solvent used in functional printing inks. Barrier properties against vegetable oil were also found to be exceptionally good for both the NFC and MFC films.     

Fe3O4@NCs/BF0.2: A magnetic bio‐based nanocatalyst for the synthesis of 2,3‐dihydro‐1H‐perimidines

Nanocellulose (NC) materials have some unique properties, which make them attractive as organic or inorganic supports for catalytic applications. Nanocatalysts with diameters of less than 100 nm are difficult to separate from the reaction mixture, therefore, magnetic nanoparticles (MNPs) were used as catalysts to overcome this problem. Fe₃O₄@NCs/BF_0.2 as a green, bio‐based, eco‐friendly, and recyclable catalyst was synthesized and characterized using fourier‐transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), X‐ray diffraction (XRD), X‐ray fluorescence (XRF), Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) techniques. Fe₃O₄@NCs/BF_0.2 was employed for the synthesis of 2,3‐dihydro‐1H‐perimidine derivatives via a reaction of 1,8‐diaminonaphthalene with various aldehydes at room temperature under solvent‐free conditions. The present procedure offers several advantages including a short reaction time, excellent yields, easy separation of catalyst, and environmental friendliness.     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了269.33 F·g^-1和350.13 F·cm^-3的高质量和体积比电容,并在10.0 A·g^-1时仍能达到215.88 F·g^-1和280.62 F·cm^-3(其初始值的80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

纳米纤维素/还原氧化石墨烯复合材料用于高性能超级电容器

以高浓度氧化石墨烯(GO)溶液作为反应前驱体,纳米纤维素(NC)作为物理间隔物和电解液储存器,通过简单的一步水热法制备了纳米纤维素/还原氧化石墨烯(NC/rGO)复合材料,并探究了其作为超级电容器电极材料的潜力。结果如下：NC添加量为1 mL所制备的NC/rGO-1具有最佳电化学性能。基于NC/rGO-1的无黏合剂对称型超级电容器在0.3 A·g^-1的电流密度下显示出了 269.33 F·g^-1和 350.13 F·cm^-3的高质量和体积比电容,并在 10.0 A·g^-1时仍能达到 215.88 F·g^-1和 280.62 F·cm^-3(其初始值的 80.15%)。组装器件还显示出了较高的质量和体积能量密度(9.3 Wh·kg^-1和 12.13 Wh·L^-1)和出色的循环性能(10 A·g^-1下10 000次循环后其初始比电容仅减少6.02%)。     

Detection of nanocellulose in commercial products and its size characterization using asymmetric flow field-flow fractionation

The paper reports on a method for the detection of nanocellulose (NC) in consumer products by making use of a combination of (a) liquid-liquid extraction with an ionic liquid, and (b) size characterization by asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) and refractive index (RI) detection. Both AF4 and MALS are viable tools for characterizing the size of the nanofibers. Sample preparation is easy, and the extraction efficiency of the method is 80.9 ± 1.8% (n = 5). It was applied to the detection of NC in toothpaste and coconut foodstuff to verify the practicability of the method.

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Graphical abstract Nanocellulose (NC) monitoring from coconut products and toothpaste and its size characterization by liquid-liquid extraction and asymmetric flow field-flow fractionation equipped with multi-angle light scattering and refractive index detection (AF4-MALS-RI).

     

Determination of trace elements of some Egyptian crops by instrumental neutron activation,inductively coupled plasma-atomic emission spectrometric and flameless atomic absorption spectrophotometric analysis

Instrumental neutron activation analysis was used for the determination of Al, Br, Ca, Ce, Cl, Co, Cr, Cs, Eu, Fe, K, La, Mg, Mn, Na, Rb, Sb, Sc, Se, Ti, Th, V and Zn, ICP-AES for the determination Al, Ag, Ba, Be, Ca, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Na, Ni, P, Sc, Sr, Ti, V and Zn and flameless AAS for the determination of Cd, Hg and Pb in egg plant, potatoes, green pepper (Leguminosae), vegetable marrow (Cucurbitaceae), pears, apple (Rosaceae), castor oil plant (Euphorbiaceae), lettuce (compositae), dill, parsley, coriander (Umbelliferae), and in some soil samples collected from Aswan province.     

57Fe Mössbauer spectroscopy of banded iron formations from eastern India

Samples of the mosses Hylocomium splendens and Pleurozium schreberi, collected in the summer of 1998, were used to study the atmospheric deposition of heavy metals and other toxic elements in the Chelyabinsk Region situated in the South Urals, one of the most heavily polluted industrial areas of the Russian Federation. Samples of natural soils were collected simultaneously with moss at the same 30 sites in order to investigate surface accumulation of heavy metals and to examine the correlation of elements in moss and soil samples in order to separate contributions from atmospheric deposition and from soil minerals. A total of 38 elements (Na, Mg, Al, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Rb, Sr, Zr, Mo, Sb, Cs, Ba, La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Hf, Ta, W, Au, Th, U) in soil and 33 elements Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, Ba, La, Ce, Sm, Tb, Yb, Hf, Ta, W, Au, Th, U) were determined by epithermal neutron activation analysis. The elements Cu, Cd and Pb (in moss samples only) were obtained by atomic absorption spectrometry. VARIMAX rotated principal component analysis was used to identify and characterize different pollution sources and to point out the most polluted areas.