Green in-situ synthesized silver nanoparticles embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor
Pourreza, N., Golmohammadi, H., Naghdi, T., & Yousefi, H. (2015). Green in-situ synthesized silver nanoparticles embedded in bacterial cellulose nanopaper as a bionanocomposite plasmonic sensor. Biosensors and Bioelectronics, 74, 353-359. https://www.sciencedirect.com/science/article/pii/S0956566315302050
Herein, we introduce a new strategy for green, in-situ generation of silver nanoparticles using flexible and transparent bacterial cellulose nanopapers. In this method, adsorbed silver ions on bacterial cellulose nanopaper are reduced by the hydroxyl groups of cellulose nanofibers, acting as the reducing agent producing a bionanocomposite “embedded silver nanoparticles in transparent nanopaper” (ESNPs). The fabricated ESNPs were investigated and characterized by field emission scanning electron microscopy (FE-SEM), UV–visible spectroscopy (UV–vis), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and energy-dispersive X-ray spectroscopy (EDX). The important parameters affecting the ESNPs were optimized during the fabrication of specimens. The resulting ESNPs were used as a novel and sensitive probe for the optical sensing of cyanide ion (CN−) and 2-mercaptobenzothiazole (MBT) in water samples with satisfactory results. The change in surface plasmon resonance absorption intensity of ESNPs was linearly proportional to the concentration in the range of 0.2–2.5 µg mL−1 and 2–110 µg mL−1with a detection limit of 0.012 µg mL−1 and 1.37 µg mL−1 for CN−and MBT, respectively.
Comparative effect of mechanical beating and nanofibrillation of cellulose on paper properties made from bagasse and softwood pulps
Afra, E., Yousefi, H., Hadilam, M. M., & Nishino, T. (2013). Comparative effect of mechanical beating and nanofibrillation of cellulose on paper properties made from bagasse and softwood pulps. Carbohydrate Polymers, 97(2), 725-730. https://www.sciencedirect.com/science/article/pii/S0144861713005079
Cellulose fibers were fibrillated using mechanical beating (shearing refiner) and ultra-fine friction grinder, respectively. The fibrillated fibers were then used to make paper. Mechanical beating process created a partial skin fibrillation, while grinding turned fiber from micro to nanoscale through nanofibrillation mechanism. The partially fibrillated and nano fibrillated fibers had significant effects on paper density, tear strength, tensile strength and water drainage time. The effect of nanofibrillation on paper properties was quantitatively higher than that of mechanical beating. Paper sheets from nanofibrillated cellulose have a higher density, higher tensile strength and lower tear strength compared to those subjected to mechanical beating. Mechanical beating and nanofibrillation were both found to be promising fiber structural modifications. Long water drainage time was an important drawback of both fibrillation methods.
Improved antifungal activity and stability of chitosan nanofibers using cellulose nanocrystal on banknote papers
Amirabad, L. M., Jonoobi, M., Mousavi, N. S., Oksman, K., Kaboorani, A., & Yousefi, H. (2018). Improved antifungal activity and stability of chitosan nanofibers using cellulose nanocrystal on banknote papers. Carbohydrate polymers, 189, 229-237. https://www.sciencedirect.com/science/article/pii/S0144861718301899
Microorganisms can spread on the surface of banknotes and cause many infectious diseases. Chitosan nanofibers (CNFs) and cellulose nanocrystals (CNCs) are nanomaterials, which can affect the antimicrobial properties. In this study, the fungal species that grew on the surfaces of collected banknotes from different places were identified. To examine the antifungal effect of the both nanomaterials on the banknotes, the stable coatings using CNFs and CNCs emulsions were prepared by roller coating. The results revealed that the most colonies in the banknotes obtained from the bakeries and butcheries were Aspergilus sp., whereas the colonies in bus terminals and the hospitals were Aspergillus niger and Penicillium, respectively. The results showed that the CNCs had no antifungal effect alone on the aforementioned species, but it could improve the antifungal effect, adhesion, and stability of CNFs on the banknote surfaces. This study suggested a new approach to decrease the infection spreads through banknotes.
MWCNT-coated cellulose nanopapers: Droplet-coating, process factors, and electrical conductivity performance
Mashkour, M., Sharifinia, M., Yousefi, H., & Afra, E. (2018). MWCNT-coated cellulose nanopapers: Droplet-coating, process factors, and electrical conductivity performance. Carbohydrate polymers, 202, 504-512. https://www.sciencedirect.com/science/article/pii/S0144861718310701
Electrically conductive cellulose nanopapers (EC-CNPaps) were fabricated by the droplet-coating of multiwall carbon nanotubes (MWCNTs) on cellulose nanopapers (CNPaps), and the effects of the process factors on the electrical conductivity of EC-CNPaps were investigated. The type of CNPaps (made of softwood nanofibrillated cellulose or bacterial cellulose nanofibres), the drying methods of CNPaps (air drying, freeze drying, and oven drying), the applied method for the stabilisation and the concentration of MWCNT–water solutions, and the droplet-coating temperatures (≈23 °C and ≈60 °C) were the examined variable factors. Overall, the oven-dried nanofibrillated cellulose paper as a substrate, 0.1 wt. % of the gum Arabic stabilised MWCNT–water solution ink, and the droplet coating at 60 °C were introduced as the optimum conditions of the examined process factors in this study.
Cellulose nanofiber board
Yousefi, H., Azad, S., Mashkour, M., & Khazaeian, A. (2018). Cellulose nanofiber board. Carbohydrate polymers, 187, 133-139. https://www.sciencedirect.com/science/article/pii/S0144861718300997
A cellulose nanofiber board (CNF-board) with a nominal thickness of 3 mm was fabricated without adhesive or additive. To provide comparison, a cellulose fiber board (CF-board) was also fabricated. A novel cold pre-press apparatus was made to dewater highly absorbent CNF gel prior to drying. A mild drying condition in the vacuum oven at 70 °C and 0.005 MPa was enough to provide the CNF-board with a density of 1.3 g/cm3 thanks to its self-densification capability. Unlike the CF-board, the fabricated CNF-board had a high water-activated dimensional recovery ratio (averagely 96%) during the five cyclic wetting-drying process. The flexural and tensile strengths of CNF-board obtained were 162 MPa and 85 MPa, respectively. The corresponding values for CF-board were 28 MPa and 11 MPa, respectively. The specific flexural and tensile strengths of CNF-board obtained were higher than those of CF-board as well as some other traditional wood-based composites, polymers and structural ASTM A36 steel.
Nanopaper as an Optical Sensing Platform
Morales-Narváez, E., Golmohammadi, H., Naghdi, T., Yousefi, H., Kostiv, U., Horak, D., ... & Merkoçi, A. (2015). Nanopaper as an optical sensing platform. ACS nano, 9(7), 7296-7305. https://pubs.acs.org/doi/abs/10.1021/acsnano.5b03097
Bacterial cellulose nanopaper (BC) is a multifunctional material known for numerous desirable properties: sustainability, biocompatibility, biodegradability, optical transparency, thermal properties, flexibility, high mechanical strength, hydrophilicity, high porosity, broad chemical-modification capabilities and high surface area. Herein, we report various nanopaper-based optical sensing platforms and describe how they can be tuned, using nanomaterials, to exhibit plasmonic or photoluminescent properties that can be exploited for sensing applications. We also describe several nanopaper configurations, including cuvettes, plates and spots that we printed or punched on BC. The platforms include a colorimetric-based sensor based on nanopaper containing embedded silver and gold nanoparticles; a photoluminescent-based sensor, comprising CdSe@ZnS quantum dots conjugated to nanopaper; and a potential up-conversion sensing platform constructed from nanopaper functionalized with NaYF4:Yb3+@Er3+&SiO2 nanoparticles. We have explored modulation of the plasmonic or photoluminescent properties of these platforms using various model biologically relevant analytes. Moreover, we prove that BC is and advantageous preconcentration platform that facilitates the analysis of small volumes of optically active materials (∼4 μL). We are confident that these platforms will pave the way to optical (bio)sensors or theranostic devices that are simple, transparent, flexible, disposable, lightweight, miniaturized and perhaps wearable.
Direct mechanical production of wood nanofibers from raw wood microparticles with no chemical treatment
Yousefi, H., Azari, V., & Khazaeian, A. (2018). Direct mechanical production of wood nanofibers from raw wood microparticles with no chemical treatment. Industrial Crops and Products, 115, 26-31. https://www.sciencedirect.com/science/article/pii/S092666901830116X
Wood nanofibers (WNFs) were directly isolated from raw wood micro-particles (WMP) of Paulownia using disk grinding with no chemical treatments. TEM analysis showed that the average diameter of the WNF is 55 ± 22 nm, which is 4800 fold less than that of WMP (265 ± 45 μm). The production mechanism of WNF was discussed. XRD results confirmed that the crystallinity and crystallite size of WNF were lower than those of WMP. Chemical composition measurements and FTIR results showed that the chemical compositions of WNF and those of WMP were almost the same. A TGA test also demonstrated that the thermal stability of WNF and WMP was the same (250–260 °C), and the char content of WNF was slightly lower than that of WMP. The direct production of WNF from WMPs with no chemical treatments is an environmentally valuable approach and WNF can be regarded as a promising sustainable nanomaterials with abundant potential applications.