“…It should be noted that the spectra (Fig. 5b-d) of CNC obtained from cellulase pretreatment had new peaks at 1724 cm -1 , which corresponds to the carbonyl groups (Shimizu et al 2013;Sun et al 2015), supporting the conclusion that the CNC samples obtained from cellulase pretreated fibers contained relatively higher amounts of carboxyl groups in comparison with the control CNC sample. Figure 6a is the control sample that was obtained at 64 wt% sulfuric acid concentration without the cellulase pretreatment.…”
In this paper, a cellulase pretreatment was studied prior to the acid hydrolysis to decrease the total acid usage during the cellulose nano-crystals (CNC) preparation from a bleached softwood kraft pulp. Cellulase pretreatment facilitates the subsequent acid hydrolysis to produce CNC with similar quality to that of the control, but at a lower sulfuric acid concentration. The underline mechanism is that cellulase pretreatment led to the formation of more carbonyl groups which can be oxidized into carboxyl groups in the subsequent acid hydrolysis, furthermore, more hydroxyl groups are exposed, thus esterification into sulfonic groups can be enhanced. The results showed that with a cellulase dosage of 4.8 u/g (based on dry pulp) in the pretreatment stage, the sulfuric acid concentration can be decreased from 64 to 40 wt% without compromising the quality of resulting CNC particles. Other results from charge properties, Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) analyses also supported the conclusions.
“…It should be noted that the spectra (Fig. 5b-d) of CNC obtained from cellulase pretreatment had new peaks at 1724 cm -1 , which corresponds to the carbonyl groups (Shimizu et al 2013;Sun et al 2015), supporting the conclusion that the CNC samples obtained from cellulase pretreated fibers contained relatively higher amounts of carboxyl groups in comparison with the control CNC sample. Figure 6a is the control sample that was obtained at 64 wt% sulfuric acid concentration without the cellulase pretreatment.…”
In this paper, a cellulase pretreatment was studied prior to the acid hydrolysis to decrease the total acid usage during the cellulose nano-crystals (CNC) preparation from a bleached softwood kraft pulp. Cellulase pretreatment facilitates the subsequent acid hydrolysis to produce CNC with similar quality to that of the control, but at a lower sulfuric acid concentration. The underline mechanism is that cellulase pretreatment led to the formation of more carbonyl groups which can be oxidized into carboxyl groups in the subsequent acid hydrolysis, furthermore, more hydroxyl groups are exposed, thus esterification into sulfonic groups can be enhanced. The results showed that with a cellulase dosage of 4.8 u/g (based on dry pulp) in the pretreatment stage, the sulfuric acid concentration can be decreased from 64 to 40 wt% without compromising the quality of resulting CNC particles. Other results from charge properties, Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) analyses also supported the conclusions.
“…CNWs from cotton show lower aspect ratios between 10-12 [14,15], as opposed to that of CNWs from tunicin at 200 [16]. TEMPO-oxidization can produce CNWs with a high aspect ratio relative to those produced using sulfuric acid hydrolysis [17]. As it is well known, fillers with high aspect ratios conventionally are crucial for an efficient reinforcement effect in polymer matrices.…”
Section: Morphological Characterizations Of Cnwsmentioning
Polylactic acid (PLA)/cellulose nanowhiskers (CNWs) composite nanofibers were successfully produced by electrospinning mixed PLA solutions with CNWs. Observation by means of transmission electron microscopy (TEM) confirms the uniform distribution of CNWs within the PLA nanofibers along the direction of the fiber axis. The spectra of composite nanofibers based on Fourier transform infrared spectroscopy (FTIR) reveal characteristic hydroxyl groups as evidenced by absorption peaks of CNWs. The addition of hydrophilic CNWs is proven to improve the water absorption ability of PLA nanofibers. The initial cold crystallization temperature decreases with the increasing CNW content, implying the nucleating agent role of CNWs as effective nanofillers. The degree of crystallinity increases from 6.0% for as-electrospun pure PLA nanofibers to 14.1% and 21.6% for PLA/5CNWs and PLA/10CNWs composite nanofibers, respectively. The incorporation of CNWs into PLA is expected to offer novel functionalities to electrospun composite nanofibers in the fields of tissue engineering and membranes.
“…T direct is defined as the amount of light that passes through the sample within 2.5° with respect to the total amount of light that passes through the sample. Figure 3e shows that 225-nm-thick GN/BCNs have 50% direct transmittance, which attests to the high transparency of both GNs 4 and BCNs 28–32, 36, 37 .Figure 3( a ) A 225-nm-thick GN/BCN sensor. ( b ) Dependence of sheet resistance of GN/BCN thin films on the concentration of GNs in the sample.…”
Chemical sensors detect a variety of chemicals across numerous fields, such as automobile, aerospace, safety, indoor air quality, environmental control, food, industrial production and medicine. We successfully assemble an alcohol-sensing device comprising a thin-film sensor made of graphene nanosheets (GNs) and bacterial cellulose nanofibers (BCNs). We show that the GN/BCN sensor has a high selectivity to ethanol by distinguishing liquid–phase or vapor–phase ethanol (C2H6O) from water (H2O) intelligently with accurate transformation into electrical signals in devices. The BCN component of the film amplifies the ethanol sensitivity of the film, whereby the GN/BCN sensor has 12400% sensitivity for vapor-phase ethanol compared to the pure GN sensor, which has only 21% sensitivity. Finally, GN/BCN sensors demonstrate fast response/recovery times and a wide range of alcohol detection (10–100%). The superior sensing ability of GN/BCN compared to GNs alone is due to the improved wettability of BCNs and the ionization of liquids. We prove a facile, green, low-cost route for the assembly of ethanol-sensing devices with potential for vast application.
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